Moderator design studies for a new neutron reference source based on the D–T fusion reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mozhayev, Andrey V.; Piper, Roman K.; Rathbone, Bruce A.

2016-06-01

The radioactive isotope Californium-252 (252Cf) is relied upon internationally as a neutron calibration source for ionizing radiation dosimetry because of its high specific activity. The source may be placed within a heavy-water (D2O) moderating sphere to produce a softened spectrum representative of neutron fields common to commercial nuclear power plant environments, among others. Due to termination of the U.S. Department of Energy loan/lease program in 2012, the expense of obtaining 252Cf sources has undergone a significant increase, rendering high output sources largely unattainable. On the other hand, the use of neutron generators in research and industry applications has increased dramaticallymore » in recent years. Neutron generators based on deuterium-tritium (D-T) fusion reaction provide high neutron fluence rates and, therefore, could possibly be used as a replacement for 252Cf. To be viable, the 14.6 MeV D-T output spectrum must be significantly moderated to approximate common workplace environments. This paper presents the results of an effort to select appropriate moderating materials and design a configuration to reshape the primary neutron field toward a spectrum approaching that from a nuclear power plant workplace. A series of Monte-Carlo (MCNP) simulations of single layer high- and low-Z materials are used to identify initial candidate moderators. Candidates are refined through a similar series of simulations involving combinations of 2 to 5 different materials. The simulated energy distribution using these candidate moderators are rated in comparison to a target spectrum. Other properties, such as fluence preservation and/or enhancement, prompt gamma production and other characteristics are also considered.« less

Simulation of the neutron response matrix of an EJ309 liquid scintillator

NASA Astrophysics Data System (ADS)

Bai, Huaiyong; Wang, Zhimin; Zhang, Luyu; Jiang, Haoyu; Lu, Yi; Chen, Jinxiang; Zhang, Guohui

2018-04-01

The neutron response matrix is the basis for measuring the neutron energy spectrum through unfolding the pulse height spectrum detected with a liquid scintillator. Based on the light output of the EJ309 liquid scintillator and the related reaction cross sections, a Monte Carlo code is developed to obtain the neutron response matrix. The effects of the related reactions, the contributions of different number of neutron interactions and the wall effect of the recoil proton are discussed. With the obtained neutron response matrix and the GRAVEL iterative unfolding method, the neutron energy spectra of the 252Cf and the 241AmBe neutron sources are measured, and the results are respectively compared with the theoretical prediction of the 252Cf neutron energy spectrum and the previous results of the 241AmBe neutron energy spectra.

What happened to the moon? A lunar history mission using neutrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Breitkreutz, H.; Li, X.; Burfeindt, J.

2011-07-01

The ages of lunar rocks can be determined using the {sup 40}Ar -{sup 39}Ar technique that can be used in-situ on the moon if a neutron source, a noble gas mass spectrometer and a gas extraction and purification system are brought to the lunar surface. A possible instrument for such a task is ISAGE, which combines a strong {sup 252}Cf neutron source and a compact spectrometer for in-situ dating of e.g. the South Pole Aitken impact basin or the potentially very young basalts south of the Aristachus Plateau. In this paper, the design of the neutron source will be discussed.more » The source is assumed to be a hollow sphere surrounded by a reflector, a geometry that provides a very homogeneous flux at the irradiation position inside the sphere. The optimal source geometry depending on the experimental conditions, the costs of transportation for the reflector and the costs of the source itself are calculated. A minimum {sup 252}Cf mass of 1.5 mg is determined. (authors)« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelley, R.P., E-mail: rpkelley@ufl.edu; Ray, H.; Jordan, K.A.

An empirical investigation of the scintillation mechanism in a pressurized {sup 4}He gas fast neutron detector was conducted using pulse shape fitting. Scintillation signals from neutron interactions were measured and averaged to produce a single generic neutron pulse shape from both a {sup 252}Cf spontaneous fission source and a (d,d) neutron generator. An expression for light output over time was then developed by treating the decay of helium excited states in the same manner as the decay of radioactive isotopes. This pulse shape expression was fitted to the measured neutron pulse shape using a least-squares optimization algorithm, allowing an empiricalmore » analysis of the mechanism of scintillation inside the {sup 4}He detector. A further understanding of this mechanism in the {sup 4}He detector will advance the use of this system as a neutron spectrometer. For {sup 252}Cf neutrons, the triplet and singlet time constants were found to be 970 ns and 686 ns, respectively. For neutrons from the (d,d) generator, the time constants were found to be 884 ns and 636 ns. Differences were noted in the magnitude of these parameters compared to previously published data, however the general relationships were noted to be the same and checked with expected trends from theory. Of the excited helium states produced from a {sup 252}Cf neutron interaction, 76% were found to be born as triplet states, similar to the result from the neutron generator of 71%. The two sources yielded similar pulse shapes despite having very different neutron energy spectra, validating the robustness of the fits across various neutron energies.« less

Quantitative NDA of isotopic neutron sources.

PubMed

Lakosi, L; Nguyen, C T; Bagi, J

2005-01-01

A non-destructive method for assaying transuranic neutron sources was developed, using a combination of gamma-spectrometry and neutron correlation technique. Source strength or actinide content of a number of PuBe, AmBe, AmLi, (244)Cm, and (252)Cf sources was assessed, both as a safety issue and with respect to combating illicit trafficking. A passive neutron coincidence collar was designed with (3)He counters embedded in a polyethylene moderator (lined with Cd) surrounding the sources to be measured. The electronics consist of independent channels of pulse amplifiers and discriminators as well as a shift register for coincidence counting. The neutron output of the sources was determined by gross neutron counting, and the actinide content was found out by adopting specific spontaneous fission and (alpha,n) reaction yields of individual isotopes from the literature. Identification of an unknown source type and constituents can be made by gamma-spectrometry. The coincidences are due to spontaneous fission in the case of Cm and Cf sources, while they are mostly due to neutron-induced fission of the Pu isotopes (i.e. self-multiplication) and the (9)Be(n,2n)(8)Be reaction in Be-containing sources. Recording coincidence rate offers a potential for calibration, exploiting a correlation between the Pu amount and the coincidence-to-total ratio. The method and the equipment were tested in an in-field demonstration exercise, with participation of national public authorities and foreign observers. Seizure of the illicit transport of a PuBe source was simulated in the exercise, and the Pu content of the source was determined. It is expected that the method could be used for identification and assay of illicit, found, or not documented neutron sources.

Neutron detection using a water Cherenkov detector with pure water and a single PMT

NASA Astrophysics Data System (ADS)

Sidelnik, Iván; Asorey, Hernán; Blostein, Juan Jerónimo; Gómez Berisso, Mariano

2017-12-01

We present the performance of a novel neutron detector based on a water Cherenkov detector (WCD) employing pure water and a single photomultiplier tube (PMT). The experiments presented in this work were performed using 241AmBe and 252Cf neutron sources in different neutron moderator and shielding configurations. We show that fast neutrons from the 241AmBe and 241Cf sources, as well as thermal neutrons from a neutron moderator, despite having different spectral characteristics, produce essentially the same pulse histogram shape. This characteristic pulse-height histogram shapes are recorded as a clear signature of neutrons with energies lower than ≃ 11 MeV . This is verified in different experimental conditions. Our estimation of the neutron detection efficiency is at the level of (15±5)%, for fast neutrons. Since water is the material employed as active volume, the results of this study are of interest for the construction of low cost and large active volume neutron detectors for various applications. Of special importance are those related with space weather phenomena monitoring as well as those for the detection of fissile special nuclear material, including uranium or plutonium.

Cf-252 Characterization Documents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feldman, Alexander

2014-03-14

Six documents were written by Vance and Associates under contract to the Off-Site Source Recovery Project of Los Alamos National Laboratory. These Six documents provided the basis for characterization of Californium-252 sealed sources and for the packaging and manifesting of this material for disposal at the Waste Isolation Pilot Project. The Six documents are: 1. VA-OSR-10, Development of radionuclide distributions for Cf-252 sealed sources. 2. VA-OSR-11, Uncertainty analysis for Cf-252 sealed sources. 3. VA-OSR-12, To determine the radionuclides in the waste drums containing Cf-252 sealed source waste that are required to be reported under the requirements of the WIPP WACmore » and the TRAMPAC. 4. VA-OSR-13, Development of the spreadsheet for the radiological calculations for the characterization of Cf-252 sources. 5. VA-OSR-14, Relative importance of neutron-induced fission in Cf-252 sources. 6. VA-OSR-15, Determine upper bound of decay product inventories from a drum of Cf-252 sources. These six documents provide the technical basis for the characterization of Cf-252 sources and will be part of the AK documentation required for submittal to the Central Characterization Project (CCP) of WIPP.« less

A Comparison of Neutron-Based Non-Destructive Assessment Methods for Chemical Warfare Materiel and High Explosives

DOE Office of Scientific and Technical Information (OSTI.GOV)

E.H. Seabury; D.L. Chichester; C.J. Wharton

2008-08-01

Prompt Gamma Neutron Activation Analysis (PGNAA) systems employ neutrons as a probe to interrogate items, e.g. chemical warfare materiel-filled munitions. The choice of a neutron source in field-portable systems is determined by its ability to excite nuclei of interest, operational concerns such as radiological safety and ease-of-use, and cost. Idaho National Laboratory’s PINS Chemical Assay System has traditionally used a Cf-252 isotopic neutron source, but recently a Deuterium-Tritium (DT) Electronic Neutron Generator (ENG) has been tested as an alternate neutron source. This paper presents the results of using both of these neutron sources to interrogate chemical warfare materiel (CWM) andmore » high explosive (HE) filled munitions.« less

A Comparison of Neutron-Based Non-Destructive Assessment Methods for Chemical Warfare Material and High Explosives

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seabury, E. H.; Chichester, D. L.; Wharton, C. J.

2009-03-10

Prompt Gamma Neutron Activation Analysis (PGNAA) systems employ neutrons as a probe to interrogate items, e.g. chemical warfare materiel-filled munitions. The choice of a neutron source in field-portable systems is determined by its ability to excite nuclei of interest, operational concerns such as radiological safety and ease-of-use, and cost. Idaho National Laboratory's PINS Chemical Assay System has traditionally used a {sup 252}Cf isotopic neutron source, but recently a deuterium-tritium (DT) electronic neutron generator (ENG) has been tested as an alternate neutron source. This paper presents the results of using both of these neutron sources to interrogate chemical warfare materiel (CWM)more » and high explosive (HE) filled munitions.« less

Fission-neutrons source with fast neutron-emission timing

NASA Astrophysics Data System (ADS)

Rusev, G.; Baramsai, B.; Bond, E. M.; Jandel, M.

2016-05-01

A neutron source with fast timing has been built to help with detector-response measurements. The source is based on the neutron emission from the spontaneous fission of 252Cf. The time is provided by registering the fission fragments in a layer of a thin scintillation film with a signal rise time of 1 ns. The scintillation light output is measured by two silicon photomultipliers with rise time of 0.5 ns. Overall time resolution of the source is 0.3 ns. Design of the source and test measurements using it are described. An example application of the source for determining the neutron/gamma pulse-shape discrimination by a stilbene crystal is given.

Intracavitary moderator balloon combined with (252)Cf brachytherapy and boron neutron capture therapy, improving dosimetry in brain tumour and infiltrations.

PubMed

Brandão, S F; Campos, T P R

2015-07-01

This article proposes a combination of californium-252 ((252)Cf) brachytherapy, boron neutron capture therapy (BNCT) and an intracavitary moderator balloon catheter applied to brain tumour and infiltrations. Dosimetric evaluations were performed on three protocol set-ups: (252)Cf brachytherapy combined with BNCT (Cf-BNCT); Cf-BNCT with a balloon catheter filled with light water (LWB) and the same set-up with heavy water (HWB). Cf-BNCT-HWB has presented dosimetric advantages to Cf-BNCT-LWB and Cf-BNCT in infiltrations at 2.0-5.0 cm from the balloon surface. However, Cf-BNCT-LWB has shown superior dosimetry up to 2.0 cm from the balloon surface. Cf-BNCT-HWB and Cf-BNCT-LWB protocols provide a selective dose distribution for brain tumour and infiltrations, mainly further from the (252)Cf source, sparing the normal brain tissue. Malignant brain tumours grow rapidly and often spread to adjacent brain tissues, leading to death. Improvements in brain radiation protocols have been continuously achieved; however, brain tumour recurrence is observed in most cases. Cf-BNCT-LWB and Cf-BNCT-HWB represent new modalities for selectively combating brain tumour infiltrations and metastasis.

Comparison of Cf-252 thin-film sources prepared by evaporation or self-transfer

DOE PAGES

Algutifan, Noor J.; Sherman, Steven R.; Alexander, Charles W.

2014-11-29

Californium-252 (Z = 98) is valued as a potent neutron source due to its spontaneous fission decay path. Thin film sources containing Cf-252 were prepared by two techniques: evaporation and self-transfer. The sources were analyzed by alpha and gamma spectroscopy. Results indicate that self-transfer sources exhibit less alpha energy straggling and energy loss than evaporative sources. Fission fragments may also self-transfer, and sources made by self-transfer may need some decay time to reach radioactive equilibrium.

Californium Electrodepositions at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boll, Rose Ann

2015-01-01

Electrodepositions of californium isotopes were successfully performed at Oak Ridge National Laboratory (ORNL) during the past year involving two different types of deposition solutions, ammonium acetate (NH 4C 2H 3O 2) and isobutanol ((CH 3) 2CHCH 2OH). A californium product that was decay enriched in 251Cf was recovered for use in super-heavy element (SHE) research. This neutron-rich isotope, 251Cf, provides target material for SHE research for the potential discovery of heavier isotopes of Z=118. The californium material was recovered from aged 252Cf neutron sources in storage at ORNL. These sources have decayed for over 30 years, thus providing material withmore » a very high 251Cf-to- 252Cf ratio. After the source capsules were opened, the californium was purified and then electrodeposited using the isobutanol method onto thin titanium foils for use in an accelerator at the Joint Institute for Nuclear Research in Dubna, Russia. Another deposition method, ammonium acetate, was used to produce a deposition containing 1.7 0.1 Ci of 252Cf onto a stainless steel substrate. This was the largest single electrodeposition of 252Cf ever prepared. The 252Cf material was initially purified using traditional ion exchange media, such as AG50-AHIB and AG50-HCl, and further purified using a TEVA-NH 4SCN system to remove any lanthanides, resulting in the recovery of 3.6 0.1 mg of purified 252Cf. The ammonium acetate deposition was run with a current of 1.0 amp, resulting in a 91.5% deposition yield. Purification and handling of the highly radioactive californium material created additional challenges in the production of these sources.« less

The neutron-gamma Feynman variance to mean approach: Gamma detection and total neutron-gamma detection (theory and practice)

NASA Astrophysics Data System (ADS)

Chernikova, Dina; Axell, Kåre; Avdic, Senada; Pázsit, Imre; Nordlund, Anders; Allard, Stefan

2015-05-01

Two versions of the neutron-gamma variance to mean (Feynman-alpha method or Feynman-Y function) formula for either gamma detection only or total neutron-gamma detection, respectively, are derived and compared in this paper. The new formulas have particular importance for detectors of either gamma photons or detectors sensitive to both neutron and gamma radiation. If applied to a plastic or liquid scintillation detector, the total neutron-gamma detection Feynman-Y expression corresponds to a situation where no discrimination is made between neutrons and gamma particles. The gamma variance to mean formulas are useful when a detector of only gamma radiation is used or when working with a combined neutron-gamma detector at high count rates. The theoretical derivation is based on the Chapman-Kolmogorov equation with the inclusion of general reactions and corresponding intensities for neutrons and gammas, but with the inclusion of prompt reactions only. A one energy group approximation is considered. The comparison of the two different theories is made by using reaction intensities obtained in MCNPX simulations with a simplified geometry for two scintillation detectors and a 252Cf-source. In addition, the variance to mean ratios, neutron, gamma and total neutron-gamma are evaluated experimentally for a weak 252Cf neutron-gamma source, a 137Cs random gamma source and a 22Na correlated gamma source. Due to the focus being on the possibility of using neutron-gamma variance to mean theories for both reactor and safeguards applications, we limited the present study to the general analytical expressions for Feynman-alpha formulas.

Determination of the optimum-size californium-252 neutron source for borehole capture gamma-ray analysis

USGS Publications Warehouse

Senftle, F.E.; Macy, R.J.; Mikesell, J.L.

1979-01-01

The fast- and thermal-neutron fluence rates from a 3.7 ??g 252Cf neutron source in a simulated borehole have been measured as a function of the source-to-detector distance using air, water, coal, iron ore-concrete mix, and dry sand as borehole media. Gamma-ray intensity measurements were made for specific spectral lines at low and high energies for the same range of source-to-detector distances in the iron ore-concrete mix and in coal. Integral gamma-ray counts across the entire spectrum were also made at each source-to-detector distance. From these data, the specific neutron-damage rate, and the critical count-rate criteria, we show that in an iron ore-concrete mix (low hydrogen concentration), 252Cf neutron sources of 2-40 ??g are suitable. The source size required for optimum gamma-ray sensitivity depends on the energy of the gamma ray being measured. In a hydrogeneous medium such as coal, similar measurements were made. The results show that sources from 2 to 20 ??g are suitable to obtain the highest gamma-ray sensitivity, again depending on the energy of the gamma ray being measured. In a hydrogeneous medium, significant improvement in sensitivity can be achieved by using faster electronics; in iron ore, it cannot. ?? 1979 North-Holland Publishing Co.

A physics investigation of deadtime losses in neutron counting at low rates with Cf252

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, Louise G; Croft, Stephen

2009-01-01

{sup 252}Cf spontaneous fission sources are used for the characterization of neutron counters and the determination of calibration parameters; including both neutron coincidence counting (NCC) and neutron multiplicity deadtime (DT) parameters. Even at low event rates, temporally-correlated neutron counting using {sup 252}Cf suffers a deadtime effect. Meaning that in contrast to counting a random neutron source (e.g. AmLi to a close approximation), DT losses do not vanish in the low rate limit. This is because neutrons are emitted from spontaneous fission events in time-correlated 'bursts', and are detected over a short period commensurate with their lifetime in the detector (characterizedmore » by the system die-away time, {tau}). Thus, even when detected neutron events from different spontaneous fissions are unlikely to overlap in time, neutron events within the detected 'burst' are subject to intrinsic DT losses. Intrinsic DT losses for dilute Pu will be lower since the multiplicity distribution is softer, but real items also experience self-multiplication which can increase the 'size' of the bursts. Traditional NCC DT correction methods do not include the intrinsic (within burst) losses. We have proposed new forms of the traditional NCC Singles and Doubles DT correction factors. In this work, we apply Monte Carlo neutron pulse train analysis to investigate the functional form of the deadtime correction factors for an updating deadtime. Modeling is based on a high efficiency {sup 3}He neutron counter with short die-away time, representing an ideal {sup 3}He based detection system. The physics of dead time losses at low rates is explored and presented. It is observed that new forms are applicable and offer more accurate correction than the traditional forms.« less

Intracavitary moderator balloon combined with 252Cf brachytherapy and boron neutron capture therapy, improving dosimetry in brain tumour and infiltrations

PubMed Central

Brandão, S F

2015-01-01

Objective: This article proposes a combination of californium-252 (252Cf) brachytherapy, boron neutron capture therapy (BNCT) and an intracavitary moderator balloon catheter applied to brain tumour and infiltrations. Methods: Dosimetric evaluations were performed on three protocol set-ups: 252Cf brachytherapy combined with BNCT (Cf-BNCT); Cf-BNCT with a balloon catheter filled with light water (LWB) and the same set-up with heavy water (HWB). Results: Cf-BNCT-HWB has presented dosimetric advantages to Cf-BNCT-LWB and Cf-BNCT in infiltrations at 2.0–5.0 cm from the balloon surface. However, Cf-BNCT-LWB has shown superior dosimetry up to 2.0 cm from the balloon surface. Conclusion: Cf-BNCT-HWB and Cf-BNCT-LWB protocols provide a selective dose distribution for brain tumour and infiltrations, mainly further from the 252Cf source, sparing the normal brain tissue. Advances in knowledge: Malignant brain tumours grow rapidly and often spread to adjacent brain tissues, leading to death. Improvements in brain radiation protocols have been continuously achieved; however, brain tumour recurrence is observed in most cases. Cf-BNCT-LWB and Cf-BNCT-HWB represent new modalities for selectively combating brain tumour infiltrations and metastasis. PMID:25927876

Evaluation of neutron sources for ISAGE-in-situ-NAA for a future lunar mission.

PubMed

Li, X; Breitkreutz, H; Burfeindt, J; Bernhardt, H-G; Trieloff, M; Hopp, J; Jessberger, E K; Schwarz, W H; Hofmann, P; Hiesinger, H

2011-11-01

For a future Moon landing, a concept for an in-situ NAA involving age determination using the (40)Ar-(39)Ar method is developed. A neutron source (252)Cf is chosen for sample irradiation on the Moon. A special sample-in-source irradiation geometry is designed to provide a homogeneous distribution of neutron flux at the irradiation position. Using reflector, the neutron flux is likely to increase by almost 200%. Sample age of 1Ga could be determined. Elemental analysis using INAA is discussed. Copyright © 2011 Elsevier Ltd. All rights reserved.

New production systems at ISOLDE

NASA Astrophysics Data System (ADS)

Hagebø, E.; Hoff, P.; Jonsson, O. C.; Kugler, E.; Omtvedt, J. P.; Ravn, H. L.; Steffensen, K.

1992-08-01

New target systems for the ISOLDE on-line mass separator facility are presented. Targets of carbides, metal/graphite mixtures, foils of refractory metals, molten metals and oxides have been tested. Beams of high intensity of neutron-rich isotopes of a large number of elements are obtained from a uranium carbide target with a hot plasma-discharge ion source. A target of ZrO 2 has been shown to provide high intensity beams of neutron-deficient isotopes of Mn, Cu, Zn, Ga, Ge, As, Se, Br, Kr and Rb, while a SiC target with a hot plasma ion source gives intense beams of radioactive isotopes of a number of light elements. All these systems are rather chemically unselective. Chemically selective performance has been obtained for several systems, i.e.: the production of neutron-deficient Au from ( 3He, pχn) reactions on a Pt/graphite target with a hot plasma ion source; the production of neutron-deficient Lu and LuF + and Hf and HfF 3+ from a Ta-foil target with a hot plasma ion source under CF 4 addition; the production of neutron-deficient Sr as SrF + and Y as YF 2+ form a Nb-foil target with a W surface ionizer under CF 4 addition; the production of neutron-deficient Se as COSe + from a ZrO 2 target with a hot plasma ion source under O 2 addition; and the production of radioactive F from a SiC target with a hot plasma ion source operating in Al vapour.

Development of a new method for measurement of neutron detector efficiency up to 20 MeV

DOE PAGES

Kornilov, N. V.; Grimes, S. M.; Massey, T. N.; ...

2014-09-03

A new approach to neutron detector efficiency has been taken. A neutron detector has been calibrated with a 252Cf source at low energy. The calibration can be extended to energies above 8 MeV based on the 252Cf results. The techniques uses the fact that the cross section for a symmetric reaction with nucleus of atomic number A yielding a final nucleus with atomic number (2A-1) and a neutron A + A → (2A – 1) + n. This reaction must be symmetric about 90° in the center-of-mass system. Furthermore, the laboratory energies for the neutrons at the paired energies differmore » substantially. Thus, an efficiency known at one of the two angles can be used to determine the efficiency to higher energies or, for a negative Q, to lower neutron energies.« less

Viability of Acremonium coenophialum in tall fescue seed after ionizing radiation treatments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagegni, A.M.; Sleper, D.A.; Kerr, H.D.

Planting tall fescue (Festuca arundinacea Schreb.) seed free of the endophyte Acremonium coenophialum Morgan-Jones and Gams allows establishment of swards free of the fungus. Eradication of the fungal endophyte from infected tall fescue seeds containing 130 g kg{sup {minus}1} moisture using ionizing radiation was investigated. Three sources of radiation were used: gamma rays ({sup 60}Co source), neutron particles ({sup 252}Cf source), and a thermal neutron beam. The percent germination of tall fescue seeds among gamma doses did not differ significantly (P < 0.05) from the control treatment and did not show a significant negative response (R{sub 2} = 0.41) tomore » increasing levels of gamma radiation. At 250 Gy of gamma radiation, percent germination after 14 d was still > 90%. Percent seed germination of tall fescue and high levels of radiation were negatively correlated for both sources of neutrons. Gamma radiation was shown to reduce (P < 0.01) the percent of the viable endophyte to {approx} 10% of control. The {sup 252}Cf and thermal neutrons reduced the percent of tall fescue infected by the endophyte to {approx} 30% without deleterious effects on seed germination.« less

Single-view 3D reconstruction of correlated gamma-neutron sources

DOE PAGES

Monterial, Mateusz; Marleau, Peter; Pozzi, Sara A.

2017-01-05

We describe a new method of 3D image reconstruction of neutron sources that emit correlated gammas (e.g. Cf- 252, Am-Be). This category includes a vast majority of neutron sources important in nuclear threat search, safeguards and non-proliferation. Rather than requiring multiple views of the source this technique relies on the source’s intrinsic property of coincidence gamma and neutron emission. As a result only a single-view measurement of the source is required to perform the 3D reconstruction. In principle, any scatter camera sensitive to gammas and neutrons with adequate timing and interaction location resolution can perform this reconstruction. Using a neutronmore » double scatter technique, we can calculate a conical surface of possible source locations. By including the time to a correlated gamma we further constrain the source location in three-dimensions by solving for the source-to-detector distance along the surface of said cone. As a proof of concept we applied these reconstruction techniques on measurements taken with the the Mobile Imager of Neutrons for Emergency Responders (MINER). Two Cf-252 sources measured at 50 and 60 cm from the center of the detector were resolved in their varying depth with average radial distance relative resolution of 26%. To demonstrate the technique’s potential with an optimized system we simulated the measurement in MCNPX-PoliMi assuming timing resolution of 200 ps (from 2 ns in the current system) and source interaction location resolution of 5 mm (from 3 cm). Furthermore, these simulated improvements in scatter camera performance resulted in radial distance relative resolution decreasing to an average of 11%.« less

Single-view 3D reconstruction of correlated gamma-neutron sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monterial, Mateusz; Marleau, Peter; Pozzi, Sara A.

We describe a new method of 3D image reconstruction of neutron sources that emit correlated gammas (e.g. Cf- 252, Am-Be). This category includes a vast majority of neutron sources important in nuclear threat search, safeguards and non-proliferation. Rather than requiring multiple views of the source this technique relies on the source’s intrinsic property of coincidence gamma and neutron emission. As a result only a single-view measurement of the source is required to perform the 3D reconstruction. In principle, any scatter camera sensitive to gammas and neutrons with adequate timing and interaction location resolution can perform this reconstruction. Using a neutronmore » double scatter technique, we can calculate a conical surface of possible source locations. By including the time to a correlated gamma we further constrain the source location in three-dimensions by solving for the source-to-detector distance along the surface of said cone. As a proof of concept we applied these reconstruction techniques on measurements taken with the the Mobile Imager of Neutrons for Emergency Responders (MINER). Two Cf-252 sources measured at 50 and 60 cm from the center of the detector were resolved in their varying depth with average radial distance relative resolution of 26%. To demonstrate the technique’s potential with an optimized system we simulated the measurement in MCNPX-PoliMi assuming timing resolution of 200 ps (from 2 ns in the current system) and source interaction location resolution of 5 mm (from 3 cm). Furthermore, these simulated improvements in scatter camera performance resulted in radial distance relative resolution decreasing to an average of 11%.« less

French comparison exercise with the rotating neutron spectrometer, 'ROSPEC'.

PubMed

Crovisier, P; Asselineau, B; Pelcot, G; Van-Ryckeghem, L; Cadiou, A; Truffert, H; Groetz, J E; Benmosbah, M

2005-01-01

The French laboratories in charge of 'neutron' dosimetry using the spectrometer 'ROSPEC', formed a working group in 2001. The participants began to study the behaviour of the instrument with a comparison exercise in broad energy neutron fields recommended by the International Organisation for Standardisation (ISO) and available at the LMDN in Cadarache. The complete version of the ROSPEC is made up of six spherical proportional counters fixed to a rotating platform. These counters cover different energy ranges which overlap each other to provide a link between the detectors, within the energy range from thermal neutrons to 4.5 MeV. The irradiation configurations chosen were ISO standard sources (252Cf, (252Cf+D2O)(/Cd), 241Am-Be) and the SIGMA facility. The results show that the 'thermal and epithermal' neutron fluence was widely overestimated by the spectrometer in all configurations.

Radioactivity in atomic-bomb samples from exposure to environmental neutrons.

PubMed

Endo, S; Shizuma, K; Tanaka, K; Ishikawa, M; Rühm, W; Egbert, S D; Hoshi, M

2007-12-01

For about one decade, activation measurements performed on environmental samples from a distance larger than 1 km from the hypocenter of the atomic-bomb explosion over Hiroshima suggested much higher thermal neutron fluences to the survivors than predicted. This caused concern among the radiation protection community and prompted a complete re-evaluation of all aspects of survivor dosimetry. While it was shown recently that secondary neutrons from cosmic radiation and other sources have probably been the reason for the high measured concentrations of the long-lived radioisotope 36Cl in these samples, the source for high measured concentrations of the short-lived radionuclides 152Eu and 60Co has not yet been investigated in detail. In order to quantify the production of 152Eu and 60Co in environmental samples by secondary neutrons from cosmic radiation, thermal neutron fluxes were measured by means of a He gas proportional counter in various buildings where these samples had been and still are being stored. Because a 252Cf neutron source has been operated occasionally close to one of the sample storage rooms, additional neutron flux measurements were carried out when the neutron source was in operation. The thermal neutron fluxes measured ranged from 0.00017 to 0.00093 n cm(-2) s(-1) and depended on the floor number of the investigated building. Based on the measured neutron fluxes, the specific activities from the reactions 151Eu(n,gamma)152Eu and 59Co(n,gamma)60Co in the atomic-bomb samples were estimated to be 7.9 mBq g(-1) Eu and 0.27 mBq g(-1) Co, respectively, in saturation. These activities are much lower than those recently measured in samples that had been exposed to atomic-bomb neutrons. It is therefore concluded that environmental and moderated 252Cf neutrons are not the source for the high activities that had been measured in these samples.

Analysis of linear energy transfers and quality factors of charged particles produced by spontaneous fission neutrons from 252Cf and 244Pu in the human body.

PubMed

Endo, Akira; Sato, Tatsuhiko

2013-04-01

Absorbed doses, linear energy transfers (LETs) and quality factors of secondary charged particles in organs and tissues, generated via the interactions of the spontaneous fission neutrons from (252)Cf and (244)Pu within the human body, were studied using the Particle and Heavy Ion Transport Code System (PHITS) coupled with the ICRP Reference Phantom. Both the absorbed doses and the quality factors in target organs generally decrease with increasing distance from the source organ. The analysis of LET distributions of secondary charged particles led to the identification of the relationship between LET spectra and target-source organ locations. A comparison between human body-averaged mean quality factors and fluence-averaged radiation weighting factors showed that the current numerical conventions for the radiation weighting factors of neutrons, updated in ICRP103, and the quality factors for internal exposure are valid.

Californium-252: a remarkable versatile radioisotope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osborne-Lee, I.W.; Alexander, C.W.

A product of the nuclear age, Californium-252 ({sup 252}Cf) has found many applications in medicine, scientific research, industry, and nuclear science education. Californium-252 is unique as a neutron source in that it provides a highly concentrated flux and extremely reliable neutron spectrum from a very small assembly. During the past 40 years, {sup 252}Cf has been applied with great success to cancer therapy, neutron radiography of objects ranging from flowers to entire aircraft, startup sources for nuclear reactors, fission activation for quality analysis of all commercial nuclear fuel, and many other beneficial uses, some of which are now ready formore » further growth. Californium-252 is produced in the High Flux Isotope Reactor (HFIR) and processed in the Radiochemical Engineering Development Center (REDC), both of which are located at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, Tennessee. The REDC/HFIR facility is virtually the sole supplier of {sup 252}Cf in the western world and is the major supplier worldwide. Extensive exploitation of this product was made possible through the {sup 252}Cf Market Evaluation Program, sponsored by the United States Department of Energy (DOE) [then the Atomic Energy Commission (AEC) and later the Energy Research and Development Administration (ERDA)]. This program included training series, demonstration centers, seminars, and a liberal loan policy for fabricated sources. The Market Evaluation Program was instituted, in part, to determine if large-quantity production capability was required at the Savannah River Laboratory (SRL). Because of the nature of the product and the means by which it is produced, {sup 252}Cf can be produced only in government-owned facilities. It is evident at this time that the Oak Ridge research facility can meet present and projected near-term requirements. The production, shipment, and sales history of {sup 252}Cf from ORNL is summarized herein.« less

Spectral correction factors for conventional neutron dosemeters used in high-energy neutron environments.

PubMed

Lee, K W; Sheu, R J

2015-04-01

High-energy neutrons (>10 MeV) contribute substantially to the dose fraction but result in only a small or negligible response in most conventional moderated-type neutron detectors. Neutron dosemeters used for radiation protection purpose are commonly calibrated with (252)Cf neutron sources and are used in various workplace. A workplace-specific correction factor is suggested. In this study, the effect of the neutron spectrum on the accuracy of dose measurements was investigated. A set of neutron spectra representing various neutron environments was selected to study the dose responses of a series of Bonner spheres, including standard and extended-range spheres. By comparing (252)Cf-calibrated dose responses with reference values based on fluence-to-dose conversion coefficients, this paper presents recommendations for neutron field characterisation and appropriate correction factors for responses of conventional neutron dosemeters used in environments with high-energy neutrons. The correction depends on the estimated percentage of high-energy neutrons in the spectrum or the ratio between the measured responses of two Bonner spheres (the 4P6_8 extended-range sphere versus the 6″ standard sphere). © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

MCNP SIMULATION OF THE HP(10) ENERGY RESPONSE OF A BRAZILIAN TLD ALBEDO NEUTRON INDIVIDUAL DOSEMETER, FROM THERMAL TO 20 MeV.

PubMed

Freitas, B M; Martins, M M; Pereira, W W; da Silva, A X; Mauricio, C L P

2016-09-01

The Brazilian Instituto de Radioproteção e Dosimetria (IRD) runs a neutron individual monitoring system with a home-made TLD albedo dosemeter. It has already been characterised and calibrated in some reference fields. However, the complete energy response of this dosemeter is not known, and the calibration factors for all monitored workplace neutron fields are difficult to be obtained experimentally. Therefore, to overcome such difficulties, Monte Carlo simulations have been used. This paper describes the simulation of the HP(10) neutron response of the IRD TLD albedo dosemeter using the MCNPX transport code, for energies from thermal to 20 MeV. The validation of the MCNPX modelling is done comparing the simulated results with the experimental measurements for ISO standard neutron fields of (241)Am-Be, (252)Cf, (241)Am-B and (252)Cf(D2O) and also for (241)Am-Be source moderated with paraffin and silicone. Bare (252)Cf are used for normalisation. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Technical basis for the use of a correlated neutron source in the uranium neutron coincidence collar

DOE PAGES

Root, Margaret A.; Menlove, Howard Olsen; Lanza, Richard C.; ...

2017-01-16

Active neutron coincidence systems are commonly used by international inspectorates to verify a material balance across the various stages of the nuclear fuel cycle. The Uranium Neutron Coincidence Collar (UNCL) is one such instrument; it is used to measure the linear density of 235U (g 235U/cm of active length in assembly) in fresh light water reactor fuel in nuclear fuel fabrication facilities. The UNCL and other active neutron interrogation detectors have historically relied on americium lithium ( 241AmLi) sources to induce fission within the sample in question. Californium-252 is under consideration as a possible alternative to the traditional 241AmLi source.more » Finally, this work relied upon a combination of experiments and Monte Carlo simulations to demonstrate the technical basis for the replacement of 241AmLi sources with 252Cf sources by evaluating the statistical uncertainty in the measurements incurred by each source and assessing the penetrability of neutrons from each source for the UNCL.« less

Technical basis for the use of a correlated neutron source in the uranium neutron coincidence collar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Root, Margaret A.; Menlove, Howard Olsen; Lanza, Richard C.

Active neutron coincidence systems are commonly used by international inspectorates to verify a material balance across the various stages of the nuclear fuel cycle. The Uranium Neutron Coincidence Collar (UNCL) is one such instrument; it is used to measure the linear density of 235U (g 235U/cm of active length in assembly) in fresh light water reactor fuel in nuclear fuel fabrication facilities. The UNCL and other active neutron interrogation detectors have historically relied on americium lithium ( 241AmLi) sources to induce fission within the sample in question. Californium-252 is under consideration as a possible alternative to the traditional 241AmLi source.more » Finally, this work relied upon a combination of experiments and Monte Carlo simulations to demonstrate the technical basis for the replacement of 241AmLi sources with 252Cf sources by evaluating the statistical uncertainty in the measurements incurred by each source and assessing the penetrability of neutrons from each source for the UNCL.« less

An active drop counting device using condenser microphone for superheated emulsion detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Mala; Marick, C.; Kanjilal, D.

2008-11-15

An active device for superheated emulsion detector is described. A capacitive diaphragm sensor or condenser microphone is used to convert the acoustic pulse of drop nucleation to electrical signal. An active peak detector is included in the circuit to avoid multiple triggering of the counter. The counts are finally recorded by a microprocessor based data acquisition system. Genuine triggers, missed by the sensor, were studied using a simulated clock pulse. The neutron energy spectrum of {sup 252}Cf fission neutron source was measured using the device with R114 as the sensitive liquid and compared with the calculated fission neutron energy spectrummore » of {sup 252}Cf. Frequency analysis of the detected signals was also carried out.« less

Dark Matter Limits From a 2L C3F8 Filled Bubble Chamber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robinson, Alan Edward

2015-12-01

The PICO-2L C3F8 bubble chamber search forWeakly Interacting Massive Particle (WIMP) dark matter was operated in the SNOLAB underground laboratory at the same location as the previous CF3I lled COUPP-4kg detector. Neutron calibrations using photoneutron sources in C3F8 and CF3I lled calibration bubble chambers were performed to verify the sensitivity of these target uids to dark matter scattering. This data was combined with similar measurements using a low-energy neutron beam at the University of Montreal and in situ calibrations of the PICO-2L and COUPP-4kg detectors. C3F8 provides much greater sensitivity to WIMP-proton scattering than CF3I in bubble chamber detectors. PICO-2Lmore » searched for dark matter recoils with energy thresholds below 10 keV. Radiopurity assays of detector materials were performed and the expected neutron recoil background was evaluated to be 1.6+0:3« less

Prompt fission gamma-ray emission spectral data for 239Pu(n,f) using fast directional neutrons from the LICORNE neutron source

NASA Astrophysics Data System (ADS)

Qi, L.; Wilson, J. N.; Lebois, M.; Al-Adili, A.; Chatillon, A.; Choudhury, D.; Gatera, A.; Georgiev, G.; Göök, A.; Laurent, B.; Maj, A.; Matea, I.; Oberstedt, A.; Oberstedt, S.; Rose, S. J.; Schmitt, C.; Wasilewska, B.; Zeiser, F.

2018-03-01

Prompt fission gamma-ray spectra (PFGS) have been measured for the 239Pu(n,f) reaction using fast neutrons at Ēn=1.81 MeV produced by the LICORNE directional neutron source. The setup makes use of LaBr3 scintillation detectors and PARIS phoswich detectors to measure the emitted prompt fission gamma rays (PFG). The mean multiplicity, average total energy release per fission and average energy of photons are extracted from the unfolded PFGS. These new measurements provide complementary information to other recent work on thermal neutron induced fission of 239Pu and spontaneous fission of 252Cf.

GEANT4 and PHITS simulations of the shielding of neutrons from the 252Cf source

NASA Astrophysics Data System (ADS)

Shin, Jae Won; Hong, Seung-Woo; Bak, Sang-In; Kim, Do Yoon; Kim, Chong Yeal

2014-09-01

Monte Carlo simulations are performed by using the GEANT4 and the PHITS for studying the neutron-shielding abilities of several materials, such as graphite, iron, polyethylene, NS-4-FR and KRAFTON-HB. As a neutron source, 252Cf is considered. For the Monte Carlo simulations by using the GEANT4, high precision (G4HP) models with the G4NDL 4.2 based on ENDF/B-VII data are used. For the simulations by using the PHITS, the JENDL-4.0 library is used. The neutron-dose-equivalent rates with or without five different shielding materials are estimated and compared with the experimental values. The differences between the shielding abilities calculated by using the GEANT4 with the G4NDL 4.2 and the PHITS with the JENDL-4.0 are found not to be significant for all the cases considered in this work. The neutron-dose-equivalent rates obtained by using the GEANT4 and the PHITS are compared with experimental data and other simulation results. Our neutron-dose-equivalent rates agree well with the experimental dose-equivalent rates, within 20% errors, except for polyethylene. For polyethylene, the discrepancies between our calculations and the experiments are less than 40%, as observed in other simulation results.

Preliminary calibration of the ACP safeguards neutron counter

NASA Astrophysics Data System (ADS)

Lee, T. H.; Kim, H. D.; Yoon, J. S.; Lee, S. Y.; Swinhoe, M.; Menlove, H. O.

2007-10-01

The Advanced Spent Fuel Conditioning Process (ACP), a kind of pyroprocess, has been developed at the Korea Atomic Energy Research Institute (KAERI). Since there is no IAEA safeguards criteria for this process, KAERI has developed a neutron coincidence counter to make it possible to perform a material control and accounting (MC&A) for its ACP materials for the purpose of a transparency in the peaceful uses of nuclear materials at KAERI. The test results of the ACP Safeguards Neutron Counter (ASNC) show a satisfactory performance for the Doubles count measurement with a low measurement error for its cylindrical sample cavity. The neutron detection efficiency is about 21% with an error of ±1.32% along the axial direction of the cavity. Using two 252Cf neutron sources, we obtained various parameters for the Singles and Doubles rates for the ASNC. The Singles, Doubles, and Triples rates for a 252Cf point source were obtained by using the MCNPX code and the results for the ft8 cap multiplicity tally option with the values of ɛ, fd, and ft measured with a strong source most closely match the measurement results to within a 1% error. A preliminary calibration curve for the ASNC was generated by using the point model equation relationship between 244Cm and 252Cf and the calibration coefficient for the non-multiplying sample is 2.78×10 5 (Doubles counts/s/g 244Cm). The preliminary calibration curves for the ACP samples were also obtained by using an MCNPX simulation. A neutron multiplication influence on an increase of the Doubles rate for a metal ingot and UO2 powder is clearly observed. These calibration curves will be modified and complemented, when hot calibration samples become available. To verify the validity of this calibration curve, a measurement of spent fuel standards for a known 244Cm mass will be performed in the near future.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lintereur, Azaree T.; Ely, James H.; Stave, Jean A.

The goal of this was research effort was to test the ability of two poly vinyltoluene research samples to produce recordable, distinguishable signals in response to gamma rays and neutrons. Pulse shape discrimination was performed to identify if the signal was generated by a gamma ray or a neutron. A standard figure of merit for pulse shape discrimination was used to quantify the gamma-neutron pulse separation. Measurements were made with gamma and neutron sources with and without shielding. The best figure of merit obtained was 1.77; this figure of merit was achieved with the first sample in response to anmore » un-moderated 252Cf source shielded with 5.08 cm of lead.« less

DOSE PROFILE MODELING OF IDAHO NATIONAL LABORATORY’S ACTIVE NEUTRON INTERROGATION TEST FACILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. L. Chichester; E. H. Seabury; J. M. Zabriskie

2009-06-01

A new research and development laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for DT fusion (14.1 MeV) neutron generators (2 x 108 neutrons per second), DD fusion (2.5 MeV) neutron generators (up to 2 x 106 neutrons per second), and 252Cf spontaneous fission neutron sources (6.7 x 107 neutrons per second, 30 micrograms). Shielding at the laboratory is comprised of modular concrete shield blocks 0.76 m thick with tongue-in-groove features to prevent radiation streaming, arranged into one small and one large test vault.more » The larger vault is designed to allow operation of the DT generator and has walls 3.8 m tall, an entrance maze, and a fully integrated electrical interlock system; the smaller test vault is designed for 252Cf and DD neutron sources and has walls 1.9 m tall and a simple entrance maze. Both analytical calculations and numerical simulations were used in the design process for the building to assess the performance of the shielding walls and to ensure external dose rates are within required facility limits. Dose rate contour plots have been generated for the facility to visualize the effectiveness of the shield wall and entrance maze and to illustrate the spatial profile of the radiation dose field above the facility and the effects of skyshine around the vaults.« less

Monte Carlo N-particle simulation of neutron-based sterilisation of anthrax contamination

PubMed Central

Liu, B; Xu, J; Liu, T; Ouyang, X

2012-01-01

Objective To simulate the neutron-based sterilisation of anthrax contamination by Monte Carlo N-particle (MCNP) 4C code. Methods Neutrons are elementary particles that have no charge. They are 20 times more effective than electrons or γ-rays in killing anthrax spores on surfaces and inside closed containers. Neutrons emitted from a 252Cf neutron source are in the 100 keV to 2 MeV energy range. A 2.5 MeV D–D neutron generator can create neutrons at up to 1013 n s−1 with current technology. All these enable an effective and low-cost method of killing anthrax spores. Results There is no effect on neutron energy deposition on the anthrax sample when using a reflector that is thicker than its saturation thickness. Among all three reflecting materials tested in the MCNP simulation, paraffin is the best because it has the thinnest saturation thickness and is easy to machine. The MCNP radiation dose and fluence simulation calculation also showed that the MCNP-simulated neutron fluence that is needed to kill the anthrax spores agrees with previous analytical estimations very well. Conclusion The MCNP simulation indicates that a 10 min neutron irradiation from a 0.5 g 252Cf neutron source or a 1 min neutron irradiation from a 2.5 MeV D–D neutron generator may kill all anthrax spores in a sample. This is a promising result because a 2.5 MeV D–D neutron generator output >1013 n s−1 should be attainable in the near future. This indicates that we could use a D–D neutron generator to sterilise anthrax contamination within several seconds. PMID:22573293

Monte Carlo N-particle simulation of neutron-based sterilisation of anthrax contamination.

PubMed

Liu, B; Xu, J; Liu, T; Ouyang, X

2012-10-01

To simulate the neutron-based sterilisation of anthrax contamination by Monte Carlo N-particle (MCNP) 4C code. Neutrons are elementary particles that have no charge. They are 20 times more effective than electrons or γ-rays in killing anthrax spores on surfaces and inside closed containers. Neutrons emitted from a (252)Cf neutron source are in the 100 keV to 2 MeV energy range. A 2.5 MeV D-D neutron generator can create neutrons at up to 10(13) n s(-1) with current technology. All these enable an effective and low-cost method of killing anthrax spores. There is no effect on neutron energy deposition on the anthrax sample when using a reflector that is thicker than its saturation thickness. Among all three reflecting materials tested in the MCNP simulation, paraffin is the best because it has the thinnest saturation thickness and is easy to machine. The MCNP radiation dose and fluence simulation calculation also showed that the MCNP-simulated neutron fluence that is needed to kill the anthrax spores agrees with previous analytical estimations very well. The MCNP simulation indicates that a 10 min neutron irradiation from a 0.5 g (252)Cf neutron source or a 1 min neutron irradiation from a 2.5 MeV D-D neutron generator may kill all anthrax spores in a sample. This is a promising result because a 2.5 MeV D-D neutron generator output >10(13) n s(-1) should be attainable in the near future. This indicates that we could use a D-D neutron generator to sterilise anthrax contamination within several seconds.

Performance of the electronic personal dosemeter for neutron 'Saphydose-N' at different workplaces of nuclear facilities.

PubMed

Lahaye, T; Chau, Q; Ménard, S; Lacoste, V; Muller, H; Luszik-Bhadra, M; Reginatto, M; Bruguier, P

2006-01-01

This paper mainly aims at presenting the measurements and the results obtained with the electronic personal neutron dosemeter Saphydose-N at different facilities. Three campaigns were led in the frame of the European contract EVIDOS ('Evaluation of Individual Dosimetry in Mixed Neutron and Photon Radiation Fields'). The first one consisted in the measurements at the IRSN French research laboratory in reference neutron fields generated by a thermal facility (SIGMA), radionuclide ISO sources ((241)AmBe; (252)Cf; (252)Cf(D(2)O)\\Cd) and a realistic spectrum (CANEL/T400). The second one was performed at the Krümmel Nuclear Power Plant (Germany) close to the boiling water reactor and to a spent fuel transport cask. The third one was realised at Mol (Belgium), at the VENUS Research Reactor and at Belgonucléaire, a fuel processing factory.

Validation of IRDFF in 252Cf standard and IRDF-2002 reference neutron fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simakov, Stanislav; Capote Noy, Roberto; Greenwood, Lawrence R.

The results of validation of the latest release of International Reactor Dosimetry and Fusion File, IRDFF-1.03, in the standard 252Cf(s.f.) and reference 235U(nth,f) neutron benchmark fields are presented. The spectrum-averaged cross sections were shown to confirm the recommended spectrum for 252Cf spontaneous fission source; that was not the case for the current recommended spectra for 235U(nth,f). IRDFF was also validated in the spectra of the research reactor facilities ISNF, Sigma-Sigma and YAYOI, which are available in the IRDF- 2002 collection. Before this analysis, the ISFN spectrum was resimulated to remove unphysical oscillations in spectrum. IRDFF-1.03 was shown to reasonably reproducemore » the spectrum-averaged data measured in these fields except for the case of YAYOI.« less

Response of CMS avalanche photo-diodes to low energy neutrons

NASA Astrophysics Data System (ADS)

Brown, R. M.; Deiters, K.; Ingram, Q.; Renker, D.

2012-12-01

The response of the Avalanche Photo-diodes (APDs) installed in the CMS detector at the LHC to neutrons from 241AmBe and 252Cf sources is reported. Signals in size equivalent to those of up to 106 photo-electrons with the nominal APD gain are observed. Measurements with an APD with the protective epoxy coating removed and with the source placed behind the APD show that there is an important response due to recoil protons from neutron interactions with the hydrogen in the epoxy, in addition to signals from neutron interactions with the silicon of the diode. The effective gain of these signals is much smaller than the diode's nominal gain.

Measurement of prompt fission neutron spectrum for spontaneous fission of 252Cf using γ multiplicity tagging

NASA Astrophysics Data System (ADS)

Blain, E.; Daskalakis, A.; Block, R. C.; Danon, Y.

2017-06-01

The prompt fission neutron spectrum from spontaneous fission of 252Cf is an integral part of several aspects of nuclear data. Not only is the spectrum itself of interest, but neutron detectors often use the spectrum for calibration, and other prompt fission neutron spectra are measured as a ratio to 252Cf. Therefore, reducing the uncertainties in this spectrum will allow for more accurate nuclear data to be available across a wide range of fields. The prompt fission neutron spectrum for the spontaneous fission of 252Cf was measured at Rensselaer Polytechnic Institute using the multiple γ tagging method with a 18.4-ng fission sample. An EJ-301 liquid scintillator fast neutron detector was used to measure the high energy portion of the spectrum, 0.5-7 MeV, and a thin EJ-204 plastic scintillator was used to measure the low energy portion of the spectrum, from 50 keV to 2 MeV. These spectra both show good agreement with the current evaluation of 252Cf and have low associated uncertainties providing a new high precision measurement that helps reduce the uncertainties in the prompt fission neutron spectrum for the spontaneous fission of 252Cf.

Detecting fast and thermal neutrons with a boron loaded liquid scintillator, EJ-339A.

PubMed

Pino, F; Stevanato, L; Cester, D; Nebbia, G; Sajo-Bohus, L; Viesti, G

2014-09-01

A commercial boron-loaded liquid scintillator EJ-339 A was studied, using a (252)Cf source with/without polyethylene moderator, to examine the possibility of discriminating slow-neutron induced events in (10)B from fast-neutron events, resulting from proton recoils, and gamma-ray events. Despite the strong light quenching associated with neutron induced events in (10)B, correct classification of these events is shown to be possible with the aid of digital signal processing. Copyright © 2014 Elsevier Ltd. All rights reserved.

Assessment of neutron dosemeters around standard sources and nuclear fissile objects.

PubMed

Raimondi, N; Tournier, B; Groetz, J E; Piot, J; Riebler, E; Crovisier, P; Chambaudet, A; Cabanné, N

2002-01-01

In order to evaluate the neutron doses around nuclear fissile objects, a comparative study has been made on several neutron dosemeters: bubble dosemeters, etched-track detectors (CR-39) and 3He-filled proportional counters used as dose-rate meters. The measurements were made on the ambient and the personal dose equivalents H*(10) and Hp(10). Results showed that several bubble dosemeters should have been used due to a low reproducibility in the measurements. A strong correlation with the neutron energy was also found, with about a 30% underestimation of Hp(10) for neutrons from the PuBe source, and about a 9% overestimation for neutrons from the 252Cf source. Measurements of the nuclear fissile objects were made using the CR-39 and the dose-rate meters. The CR-39 led to an underestimation of 30% with respect to the neutron dose-rate meter measurements. In addition, the MCNP calculation code was used in the different configurations.

An airport cargo inspection system based on X-ray and thermal neutron analysis (TNA).

PubMed

Ipe, Nisy E; Akery, A; Ryge, P; Brown, D; Liu, F; Thieu, J; James, B

2005-01-01

A cargo inspection system incorporating a high-resolution X-ray imaging system with a material-specific detection system based on Ancore Corporation's patented thermal neutron analysis (TNA) technology can detect bulk quantities of explosives and drugs concealed in trucks or cargo containers. The TNA process utilises a 252Cf neutron source surrounded by a moderator. The neutron interactions with the inspected object result in strong and unique gamma-ray signals from nitrogen, which is a key ingredient in modern high explosives, and from chlorinated drugs. The TNA computer analyses the gamma-ray signals and automatically determines the presence of explosives or drugs. The radiation source terms and shielding design of the facility are described. For the X-ray generator, the primary beam, leakage radiation, and scattered primary and leakage radiation were considered. For the TNA, the primary neutrons and tunnel scattered neutrons as well as the neutron-capture gamma rays were considered.

SPECTRAL CORRECTION FACTORS FOR CONVENTIONAL NEUTRON DOSE METERS USED IN HIGH-ENERGY NEUTRON ENVIRONMENTS-IMPROVED AND EXTENDED RESULTS BASED ON A COMPLETE SURVEY OF ALL NEUTRON SPECTRA IN IAEA-TRS-403.

PubMed

Oparaji, U; Tsai, Y H; Liu, Y C; Lee, K W; Patelli, E; Sheu, R J

2017-06-01

This paper presents improved and extended results of our previous study on corrections for conventional neutron dose meters used in environments with high-energy neutrons (En > 10 MeV). Conventional moderated-type neutron dose meters tend to underestimate the dose contribution of high-energy neutrons because of the opposite trends of dose conversion coefficients and detection efficiencies as the neutron energy increases. A practical correction scheme was proposed based on analysis of hundreds of neutron spectra in the IAEA-TRS-403 report. By comparing 252Cf-calibrated dose responses with reference values derived from fluence-to-dose conversion coefficients, this study provides recommendations for neutron field characterization and the corresponding dose correction factors. Further sensitivity studies confirm the appropriateness of the proposed scheme and indicate that (1) the spectral correction factors are nearly independent of the selection of three commonly used calibration sources: 252Cf, 241Am-Be and 239Pu-Be; (2) the derived correction factors for Bonner spheres of various sizes (6"-9") are similar in trend and (3) practical high-energy neutron indexes based on measurements can be established to facilitate the application of these correction factors in workplaces. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Reliability of Monte Carlo simulations in modeling neutron yields from a shielded fission source

NASA Astrophysics Data System (ADS)

McArthur, Matthew S.; Rees, Lawrence B.; Czirr, J. Bart

2016-08-01

Using the combination of a neutron-sensitive 6Li glass scintillator detector with a neutron-insensitive 7Li glass scintillator detector, we are able to make an accurate measurement of the capture rate of fission neutrons on 6Li. We used this detector with a 252Cf neutron source to measure the effects of both non-borated polyethylene and 5% borated polyethylene shielding on detection rates over a range of shielding thicknesses. Both of these measurements were compared with MCNP calculations to determine how well the calculations reproduced the measurements. When the source is highly shielded, the number of interactions experienced by each neutron prior to arriving at the detector is large, so it is important to compare Monte Carlo modeling with actual experimental measurements. MCNP reproduces the data fairly well, but it does generally underestimate detector efficiency both with and without polyethylene shielding. For non-borated polyethylene it underestimates the measured value by an average of 8%. This increases to an average of 11% for borated polyethylene.

Development of a lithium fluoride zinc sulfide based neutron multiplicity counter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowles, Christian; Behling, Spencer; Baldez, Phoenix

Here, the feasibility of a full-scale lithium fluoride zinc sulfide (LiF/ZnS) based neutron multiplicity counter has been demonstrated. The counter was constructed of modular neutron detecting stacks that each contain five sheets of LiF/ZnS interleaved between six sheets of wavelength shifting plastic with a photomultiplier tube on each end. Twelve such detector stacks were placed around a sample chamber in a square arrangement with lithiated high-density polyethylene blocks in the corners to reflect high-energy neutrons and capture low-energy neutrons. The final system design was optimized via modeling and small-scale test. Measuring neutrons from a 252Cf source, the counter achieved amore » 36% neutron detection efficiency (ϵϵ) and an View the MathML source11.7μs neutron die-away time (ττ) for a doubles figure-of-merit (ϵ 2/τ) of 109. This is the highest doubles figure-of-merit measured to-date for a 3He-free neutron multiplicity counter.« less

Development of a lithium fluoride zinc sulfide based neutron multiplicity counter

DOE PAGES

Cowles, Christian; Behling, Spencer; Baldez, Phoenix; ...

2018-01-12

Here, the feasibility of a full-scale lithium fluoride zinc sulfide (LiF/ZnS) based neutron multiplicity counter has been demonstrated. The counter was constructed of modular neutron detecting stacks that each contain five sheets of LiF/ZnS interleaved between six sheets of wavelength shifting plastic with a photomultiplier tube on each end. Twelve such detector stacks were placed around a sample chamber in a square arrangement with lithiated high-density polyethylene blocks in the corners to reflect high-energy neutrons and capture low-energy neutrons. The final system design was optimized via modeling and small-scale test. Measuring neutrons from a 252Cf source, the counter achieved amore » 36% neutron detection efficiency (ϵϵ) and an View the MathML source11.7μs neutron die-away time (ττ) for a doubles figure-of-merit (ϵ 2/τ) of 109. This is the highest doubles figure-of-merit measured to-date for a 3He-free neutron multiplicity counter.« less

A new facility for non-destructive assay using a 252Cf source.

PubMed

Stevanato, L; Caldogno, M; Dima, R; Fabris, D; Hao, Xin; Lunardon, M; Moretto, S; Nebbia, G; Pesente, S; Pino, F; Sajo-Bohus, L; Viesti, G

2013-03-01

A new laboratory facility for non-destructive analysis (NDA) using a time-tagged (252)Cf source is presented. The system is designed to analyze samples having maximum size of about 20 × 25 cm(2), the material recognition being obtained by measuring simultaneously total and energy dependent transmission of neutrons and gamma rays. The equipment technical characteristics and performances of the NDA system are presented, exploring also limits due to the sample thickness. Some recent applications in the field of cultural heritage are presented. Copyright © 2012 Elsevier Ltd. All rights reserved.

Dose profile modeling of Idaho National Laboratory's active neutron interrogation laboratory.

PubMed

Chichester, D L; Seabury, E H; Zabriskie, J M; Wharton, J; Caffrey, A J

2009-06-01

A new laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for deuterium-tritium (DT) fusion (14.1 MeV) neutron generators (2 x 10(8) n/s), deuterium-deuterium (DD) fusion (2.5 MeV) neutron generators (1 x 10(7) n/s), and (252)Cf spontaneous fission neutron sources (6.96 x 10(7) n/s, 30 microg). Shielding at the laboratory is comprised of modular concrete shield blocks 0.76 m thick with tongue-in-groove features to prevent radiation streaming, arranged into one small and one large test vault. The larger vault is designed to allow operation of the DT generator and has walls 3.8m tall, an entrance maze, and a fully integrated electrical interlock system; the smaller test vault is designed for (252)Cf and DD neutron sources and has walls 1.9 m tall and a simple entrance maze. Both analytical calculations and numerical simulations were used in the design process for the building to assess the performance of the shielding walls and to ensure external dose rates are within required facility limits. Dose rate contour plots have been generated for the facility to visualize the effectiveness of the shield walls and entrance mazes and to illustrate the spatial profile of the radiation dose field above the facility and the effects of skyshine around the vaults.

A neutron Albedo system with time rejection for landmine and IED detection

NASA Astrophysics Data System (ADS)

Kovaltchouk, V. D.; Andrews, H. R.; Clifford, E. T. H.; Faust, A. A.; Ing, H.; McFee, J. E.

2011-10-01

A neutron Albedo system has been developed for imaging of buried landmines and improvised explosive devices (IEDs). It involves irradiating the ground with fast neutrons and subsequently detecting the thermalized neutrons that return. A scintillating 6Li loaded ZnS(Ag) screen with a sensitive area of 40 cm×40 cm is used as a thermal neutron detector. Scintillation light is captured by orthogonal arrays of wavelength-shifting fibers placed on either side of the scintillator surface and then transferred to X and Y multi-pixel PMTs. A timing circuit, used with pulsed neutron sources, records the time when a neutron detection takes place relative to an external synchronization pulse from the pulsed source. Experimental tests of the Albedo system performance have been done in a sand box with a 252Cf neutron source (no time gating) and with pulsed D-D (2.6 MeV) neutrons from the Defense R&D Ottawa Van de Graaff accelerator (with time gating). Information contained in the time evolution of the thermal neutron field provided improved detection capability and image reconstruction. The detector design is described and experimental results are discussed.

Development of a thin scintillation films fission-fragment detector and a novel neutron source

NASA Astrophysics Data System (ADS)

Rusev, G.; Jandel, M.; Baramsai, B.; Bond, E. M.; Bredeweg, T. A.; Couture, A.; Daum, J. K.; Favalli, A.; Ianakiev, K. D.; Iliev, M. L.; Mosby, S.; Roman, A. R.; Springs, R. K.; Ullmann, J. L.; Walker, C. L.

2015-08-01

Investigation of prompt fission and neutron-capture Υ rays from fissile actinide samples at the Detector for Advanced Neutron Capture Experiments (DANCE) requires use of a fission-fragment detector to provide a trigger or a veto signal. A fission-fragment detector based on thin scintillating films and silicon photomultipliers has been built to serve as a trigger/veto detector in neutron-induced fission measurements at DANCE. The fissile material is surrounded by scintillating films providing a 4π detection of the fission fragments. The scintillations were registered with silicon photomultipliers. A measurement of the 235U(n,f) reaction with this detector at DANCE revealed a correct time-of-flight spectrum and provided an estimate for the efficiency of the prototype detector of 11.6(7)%. Design and test measurements with the detector are described. A neutron source with fast timing has been built to help with detector-response measurements. The source is based on the neutron emission from the spontaneous fission of 252Cf and the same type of scintillating films and silicon photomultipliers. Overall time resolution of the source is 0.3 ns. Design of the source and test measurements with it are described. An example application of the source for determining the neutron/gamma pulse-shape discrimination by a stilbene crystal is given.

A portable neutron spectroscope (NSPECT) for detection, imaging and identification of nuclear material

NASA Astrophysics Data System (ADS)

Ryan, James M.; Bancroft, Christopher; Bloser, Peter; Bravar, Ulisse; Fourguette, Dominique; Frost, Colin; Larocque, Liane; McConnell, Mark L.; Legere, Jason; Pavlich, Jane; Ritter, Greg; Wassick, Greg; Wood, Joshua; Woolf, Richard

2010-08-01

We have developed, fabricated and tested a prototype imaging neutron spectrometer designed for real-time neutron source location and identification. Real-time detection and identification is important for locating materials. These materials, specifically uranium and transuranics, emit neutrons via spontaneous or induced fission. Unlike other forms of radiation (e.g. gamma rays), penetrating neutron emission is very uncommon. The instrument detects these neutrons, constructs images of the emission pattern, and reports the neutron spectrum. The device will be useful for security and proliferation deterrence, as well as for nuclear waste characterization and monitoring. The instrument is optimized for imaging and spectroscopy in the 1-20 MeV range. The detection principle is based upon multiple elastic neutron-proton scatters in organic scintillator. Two detector panel layers are utilized. By measuring the recoil proton and scattered neutron locations and energies, the direction and energy spectrum of the incident neutrons can be determined and discrete and extended sources identified. Event reconstruction yields an image of the source and its location. The hardware is low power, low mass, and rugged. Its modular design allows the user to combine multiple units for increased sensitivity. We will report the results of laboratory testing of the instrument, including exposure to a calibrated Cf-252 source. Instrument parameters include energy and angular resolution, gamma rejection, minimum source identification distances and times, and projected effective area for a fully populated instrument.

Studying fission neutrons with 2E-2v and 2E

NASA Astrophysics Data System (ADS)

Al-Adili, Ali; Jansson, Kaj; Tarrío, Diego; Hambsch, Franz-Josef; Göök, Alf; Oberstedt, Stephan; Olivier Frégeau, Marc; Gustavsson, Cecilia; Lantz, Mattias; Mattera, Andrea; Prokofiev, Alexander V.; Rakopoulos, Vasileios; Solders, Andreas; Vidali, Marzio; Österlund, Michael; Pomp, Stephan

2018-03-01

This work aims at measuring prompt-fission neutrons at different excitation energies of the nucleus. Two independent techniques, the 2E-2v and the 2E techniques, are used to map the characteristics of the mass-dependent prompt fission neutron multiplicity, v(A), when the excitation energy is increased. The VERDI 2E-2v spectrometer is being developed at JRC-GEEL. The Fission Fragment (FF) energies are measured using two arrays of 16 silicon (Si) detectors each. The FFs velocities are obtained by time-of-flight, measured between micro-channel plates (MCP) and Si detectors. With MCPs placed on both sides of the fission source, VERDI allows for independent timing measurements for both fragments. 252Cf(sf) was measured and the present results revealed particular features of the 2E-2v technique. Dedicated simulations were also performed using the GEF code to study important aspects of the 2E-2v technique. Our simulations show that prompt neutron emission has a non-negligible impact on the deduced fragment data and affects also the shape of v(A). Geometrical constraints lead to a total-kinetic energy-dependent detection efficiency. The 2E technique utilizes an ionization chamber together with two liquid scintillator detectors. Two measurements have been performed, one of 252Cf(sf) and another one of thermal-neutron induced fission in 235U(n,f). Results from 252Cf(sf) are reported here.

Evaluation of radioisotope tracer and activation analysis techniques for contamination monitoring in space environment simulation chambers

NASA Technical Reports Server (NTRS)

Smathers, J. B.; Kuykendall, W. E., Jr.; Wright, R. E., Jr.; Marshall, J. R.

1973-01-01

Radioisotope measurement techniques and neutron activation analysis are evaluated for use in identifying and locating contamination sources in space environment simulation chambers. The alpha range method allows the determination of total contaminant concentration in vapor state and condensate state. A Cf-252 neutron activation analysis system for detecting oils and greases tagged with stable elements is described. While neutron activation analysis of tagged contaminants offers specificity, an on-site system is extremely costly to implement and provides only marginal detection sensitivity under even the most favorable conditions.

Prequantum classical statistical field theory: background field as a source of everything?

NASA Astrophysics Data System (ADS)

Khrennikov, Andrei

2011-07-01

Prequantum classical statistical field theory (PCSFT) is a new attempt to consider quantum mechanics (QM) as an emergent phenomenon, cf. with De Broglie's "double solution" approach, Bohmian mechanics, stochastic electrodynamics (SED), Nelson's stochastic QM and its generalization by Davidson, 't Hooft's models and their development by Elze. PCSFT is a comeback to a purely wave viewpoint on QM, cf. with early Schrodinger. There is no quantum particles at all, only waves. In particular, photons are simply wave-pulses of the classical electromagnetic field, cf. SED. Moreover, even massive particles are special "prequantum fields": the electron field, the neutron field, and so on. PCSFT claims that (sooner or later) people will be able to measure components of these fields: components of the "photonic field" (the classical electromagnetic field of low intensity), electronic field, neutronic field, and so on. At the moment we are able to produce quantum correlations as correlations of classical Gaussian random fields. In this paper we are interested in mathematical and physical reasons of usage of Gaussian fields. We consider prequantum signals (corresponding to quantum systems) as composed of a huge number of wave-pulses (on very fine prequantum time scale). We speculate that the prequantum background field (the field of "vacuum fluctuations") might play the role of a source of such pulses, i.e., the source of everything.

Verification of threshold activation detection (TAD) technique in prompt fission neutron detection using scintillators containing 19F

NASA Astrophysics Data System (ADS)

Sibczynski, P.; Kownacki, J.; Moszyński, M.; Iwanowska-Hanke, J.; Syntfeld-Każuch, A.; Gójska, A.; Gierlik, M.; Kaźmierczak, Ł.; Jakubowska, E.; Kędzierski, G.; Kujawiński, Ł.; Wojnarowicz, J.; Carrel, F.; Ledieu, M.; Lainé, F.

2015-09-01

In the present study ⌀ 5''× 3'' and ⌀ 2''× 2'' EJ-313 liquid fluorocarbon as well as ⌀ 2'' × 3'' BaF2 scintillators were exposed to neutrons from a 252Cf neutron source and a Sodern Genie 16GT deuterium-tritium (D+T) neutron generator. The scintillators responses to β- particles with maximum endpoint energy of 10.4 MeV from the n+19F reactions were studied. Response of a ⌀ 5'' × 3'' BC-408 plastic scintillator was also studied as a reference. The β- particles are the products of interaction of fast neutrons with 19F which is a component of the EJ-313 and BaF2 scintillators. The method of fast neutron detection via fluorine activation is already known as Threshold Activation Detection (TAD) and was proposed for photofission prompt neutron detection from fissionable and Special Nuclear Materials (SNM) in the field of Homeland Security and Border Monitoring. Measurements of the number of counts between 6.0 and 10.5 MeV with a 252Cf source showed that the relative neutron detection efficiency ratio, defined as epsilonBaF2 / epsilonEJ-313-5'', is 32.0% ± 2.3% and 44.6% ± 3.4% for front-on and side-on orientation of the BaF2, respectively. Moreover, the ⌀ 5'' EJ-313 and side-on oriented BaF2 were also exposed to neutrons from the D+T neutron generator, and the relative efficiency epsilonBaF2 / epsilonEJ-313-5'' was estimated to be 39.3%. Measurements of prompt photofission neutrons with the BaF2 detector by means of data acquisition after irradiation (out-of-beam) of nuclear material and between the beam pulses (beam-off) techniques were also conducted on the 9 MeV LINAC of the SAPHIR facility.

Use of SRIM and Garfield with Geant4 for the characterization of a hybrid 10B/3He neutron detector

NASA Astrophysics Data System (ADS)

van der Ende, B. M.; Rand, E. T.; Erlandson, A.; Li, L.

2018-06-01

This paper describes a method for more complete neutron detector characterization using Geant4's Monte Carlo methods for characterizing overall detector response rate and Garfield interfaced with SRIM for the simulation of the detector's raw pulses, as applied to a hybrid 10B/3He detector. The Geant4 models characterizing the detector's interaction with a 252Cf point source and parallel beams of mono-energetic neutrons (assuming ISO 8529 reference energy values) compare and agree well with calibrated 252Cf measurements to within 6.4%. Validated Geant4 model outputs serve as input to Garfield+SRIM calculations to provide meaningful pulse height spectra. Modifications to Garfield for this work were necessary to account for simultaneous tracking of electrons resulting from proton and triton reaction products from a single 3He neutron capture event, and it was further necessary to interface Garfield with the energy loss, range, and straggling calculations provided by SRIM. Individual raw pulses generated by Garfield+SRIM are also observed to agree well with experimentally measured raw pulses from the detector.

A probe for neutron activation analysis in a drill hole using 252Cf, and a Ge(Li) detector cooled by a melting cryogen

USGS Publications Warehouse

Tanner, A.B.; Moxham, R.M.; Senftle, F.E.; Baicker, J.A.

1972-01-01

A sonde has been built for high-resolution measurement of natural or neutron-induced gamma rays in boreholes. The sonde is 7.3 cm in diameter and about 2.2 m in length and weighs about 16 kg. The lithium-compensated germanium semiconductor detector is stabilized at -185 to -188??C for as much as ten hours by a cryostatic reservoir containing melting propane. During periods when the sonde is not in use the propane is kept frozen by a gravity-fed trickle of liquid nitrogen from a reservoir temporarily attached to the cryostat section. A 252Cf source, shielded from the detector, may be placed in the bottom section of the sonde for anlysis by measurement of neutron-activation or neutron-capture gamma rays. Stability of the cryostat with changing hydrostatic pressure, absence of vibration, lack of need for power to the cryostat during operation, and freedom of orientation make the method desirable for borehole, undersea, space, and some laboratory applications. ?? 1972.

Calibration of LiBaF3: Ce Scintillator for Fission Spectrum Neutrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reeder, Paul L.; Bowyer, Sonya M.

2002-05-21

The scintillator LiBaF3 doped with small amounts of Ce+3 has the ability to distinguish heavy charged particles (p, d, t, or a) from beta and/or gamma radiation based on the presence or absence of ns components in the scintillation light output. Because the neutron capture reaction on 6Li produces recoil alphas and tritons, this scintillator also discriminates between neutron induced events and beta or gamma interactions. An experimental technique using a time-tagged 252Cf source has been used to measure the efficiency of this scintillator for neutron capture, the calibration of neutron capture pulse height, and the pulse height resolution -more » all as a function of incident neutron energy.« less

Fast neutron flux analyzer with real-time digital pulse shape discrimination

NASA Astrophysics Data System (ADS)

Ivanova, A. A.; Zubarev, P. V.; Ivanenko, S. V.; Khilchenko, A. D.; Kotelnikov, A. I.; Polosatkin, S. V.; Puryga, E. A.; Shvyrev, V. G.; Sulyaev, Yu. S.

2016-08-01

Investigation of subthermonuclear plasma confinement and heating in magnetic fusion devices such as GOL-3 and GDT at the Budker Institute (Novosibirsk, Russia) requires sophisticated equipment for neutron-, gamma- diagnostics and upgrading data acquisition systems with online data processing. Measurement of fast neutron flux with stilbene scintillation detectors raised the problem of discrimination of the neutrons (n) from background cosmic particles (muons) and neutron-induced gamma rays (γ). This paper describes a fast neutron flux analyzer with real-time digital pulse-shape discrimination (DPSD) algorithm FPGA-implemented for the GOL-3 and GDT devices. This analyzer was tested and calibrated with the help of 137Cs and 252Cf radiation sources. The Figures of Merit (FOM) calculated for different energy cuts are presented.

Characterization of a prototype neutron portal monitor detector

NASA Astrophysics Data System (ADS)

Nakhoul, Nabil

The main objective of this thesis is to provide characterization measurements on a prototype neutron portal monitor (NPM) detector constructed at the University of Massachusetts Lowell. NPM detectors are deployed at all United States border crossings and shipping ports to stop the illicit transfer of weapons-grade plutonium (WGPu) into our country. This large prototype detector with its 0.93 square meter face area is based on thermal neutron capture in 6Li as an alternate technology to the current, very expensive, 3He-based NPM. A neutron detection efficiency of 27.5 % is measured with a 252Cf source which has a spontaneous fission neutron spectrum very similar to that of 240Pu in WGPu. Measurements with an intense 137Cs source establish the extreme insensitivity of the prototype NPM to gamma-ray backgrounds with only one additional count registered for 1.1 million incident gamma rays. This detector also has the ability to locate neutron sources to within an angle of a few degrees. Its sensitivity is further demonstrated by discovering in a few-second measurement the presence of a 2 curie PuBe neutron source even at a distance of 95.5 feet. This thesis also covers in considerable detail the design features that give rise to both a high intrinsic neutron detection efficiency and an extreme gamma-ray insensitivity.

Benchmark test of transport calculations of gold and nickel activation with implications for neutron kerma at Hiroshima.

PubMed

Hoshi, M; Hiraoka, M; Hayakawa, N; Sawada, S; Munaka, M; Kuramoto, A; Oka, T; Iwatani, K; Shizuma, K; Hasai, H

1992-11-01

A benchmark test of the Monte Carlo neutron and photon transport code system (MCNP) was performed using a 252Cf fission neutron source to validate the use of the code for the energy spectrum analyses of Hiroshima atomic bomb neutrons. Nuclear data libraries used in the Monte Carlo neutron and photon transport code calculation were ENDF/B-III, ENDF/B-IV, LASL-SUB, and ENDL-73. The neutron moderators used were granite (the main component of which is SiO2, with a small fraction of hydrogen), Newlight [polyethylene with 3.7% boron (natural)], ammonium chloride (NH4Cl), and water (H2O). Each moderator was 65 cm thick. The neutron detectors were gold and nickel foils, which were used to detect thermal and epithermal neutrons (4.9 eV) and fast neutrons (> 0.5 MeV), respectively. Measured activity data from neutron-irradiated gold and nickel foils in these moderators decreased to about 1/1,000th or 1/10,000th, which correspond to about 1,500 m ground distance from the hypocenter in Hiroshima. For both gold and nickel detectors, the measured activities and the calculated values agreed within 10%. The slopes of the depth-yield relations in each moderator, except granite, were similar for neutrons detected by the gold and nickel foils. From the results of these studies, the Monte Carlo neutron and photon transport code was verified to be accurate enough for use with the elements hydrogen, carbon, nitrogen, oxygen, silicon, chlorine, and cadmium, and for the incident 252Cf fission spectrum neutrons.

Development and operation of a 6LiF:ZnS(Ag)-scintillating plastic capture-gated detector

NASA Astrophysics Data System (ADS)

Wilhelm, K.; Nattress, J.; Jovanovic, I.

2017-01-01

We report on the design, construction, and operation of a capture-gated neutron detector based on a heterogeneous scintillating structure comprising two scintillator types. A flat, 500 μm thick sheet composed of a mixture of lithium-6-fluoride capture agent, 6LiF, and zinc sulfide phosphor, ZnS(Ag), is wrapped around scintillating polyvinyl toluene (PVT) in a form of cylinder. The 6LiF: ZnS(Ag) sheet uses an aluminum foil backing as a support for the scintillating material and as an optical reflector, and its optical properties have been characterized independently. The composite scintillator was tested using 252Cf, DD fusion, 137Cs, and 60Co sources. The intrinsic detection efficiency for neutrons from an unmoderated 252Cf source and rejection of gammas from 137Cs were measured to be 3.6 % and 10-6, respectively. A figure of merit for pulse shape discrimination of 4.6 was achieved, and capture-gated spectroscopic analysis is demonstrated.

Development of a thin scintillation films fission-fragment detector and a novel neutron source

DOE PAGES

Rusev, Gencho Yordanov; Jandel, Marian; Baramsai, Bayarbadrakh; ...

2015-08-26

Here, investigation of prompt fission and neutron-capture Υ rays from fissile actinide samples at the Detector for Advanced Neutron Capture Experiments (DANCE) requires use of a fission-fragment detector to provide a trigger or a veto signal. A fission-fragment detector based on thin scintillating films and silicon photomultipliers has been built to serve as a trigger/veto detector in neutron-induced fission measurements at DANCE. The fissile material is surrounded by scintillating films providing a 4π detection of the fission fragments. The scintillations were registered with silicon photomultipliers. A measurement of the 235U(n,f) reaction with this detector at DANCE revealed a correct time-of-flightmore » spectrum and provided an estimate for the efficiency of the prototype detector of 11.6(7)%. Design and test measurements with the detector are described. A neutron source with fast timing has been built to help with detector-response measurements. The source is based on the neutron emission from the spontaneous fission of 252Cf and the same type of scintillating films and silicon photomultipliers. Overall time resolution of the source is 0.3 ns. Design of the source and test measurements with it are described. An example application of the source for determining the neutron/gamma pulse-shape discrimination by a stilbene crystal is given.« less

Benchmark test of neutron transport calculations: indium, nickel, gold, europium, and cobalt activation with and without energy moderated fission neutrons by iron simulating the Hiroshima atomic bomb casing.

PubMed

Iwatani, K; Hoshi, M; Shizuma, K; Hiraoka, M; Hayakawa, N; Oka, T; Hasai, H

1994-10-01

A benchmark test of the Monte Carlo neutron and photon transport code system (MCNP) was performed using a bare- and energy-moderated 252Cf fission neutron source which was obtained by transmission through 10-cm-thick iron. An iron plate was used to simulate the effect of the Hiroshima atomic bomb casing. This test includes the activation of indium and nickel for fast neutrons and gold, europium, and cobalt for thermal and epithermal neutrons, which were inserted in the moderators. The latter two activations are also to validate 152Eu and 60Co activity data obtained from the atomic bomb-exposed specimens collected at Hiroshima and Nagasaki, Japan. The neutron moderators used were Lucite and Nylon 6 and the total thickness of each moderator was 60 cm or 65 cm. Measured activity data (reaction yield) of the neutron-irradiated detectors in these moderators decreased to about 1/1,000th or 1/10,000th, which corresponds to about 1,500 m ground distance from the hypocenter in Hiroshima. For all of the indium, nickel, and gold activity data, the measured and calculated values agreed within 25%, and the corresponding values for europium and cobalt were within 40%. From this study, the MCNP code was found to be accurate enough for the bare- and energy-moderated 252Cf neutron activation calculations of these elements using moderators containing hydrogen, carbon, nitrogen, and oxygen.

An equivalent n-source for WGPu derived from a spectrum-shifted PuBe source

NASA Astrophysics Data System (ADS)

Ghita, Gabriel; Sjoden, Glenn; Baciak, James; Walker, Scotty; Cornelison, Spring

2008-04-01

We have designed, built, and laboratory-tested a unique shield design that transforms the complex neutron spectrum from PuBe source neutrons, generated at high energies, to nearly exactly the neutron signature leaking from a significant spherical mass of weapons grade plutonium (WGPu). This equivalent "X-material shield assembly" (Patent Pending) enables the harder PuBe source spectrum (average energy of 4.61 MeV) from a small encapsulated standard 1-Ci PuBe source to be transformed, through interactions in the shield, so that leakage neutrons are shifted in energy and yield to become a close reproduction of the neutron spectrum leaking from a large subcritical mass of WGPu metal (mean energy 2.11 MeV). The utility of this shielded PuBe surrogate for WGPu is clear, since it directly enables detector field testing without the expense and risk of handling large amounts of Special Nuclear Materials (SNM) as WGPu. Also, conventional sources using Cf-252, which is difficult to produce, and decays with a 2.7 year half life, could be replaced by this shielded PuBe technology in order to simplify operational use, since a sealed PuBe source relies on Pu-239 (T½=24,110 y), and remains viable for more than hundreds of years.

Neutron radiative capture methods for surface elemental analysis

USGS Publications Warehouse

Trombka, J.I.; Senftle, F.; Schmadebeck, R.

1970-01-01

Both an accelerator and a 252Cf neutron source have been used to induce characteristic gamma radiation from extended soil samples. To demonstrate the method, measurements of the neutron-induced radiative capture and activation gamma rays have been made with both Ge(Li) and NaI(Tl) detectors, Because of the possible application to space flight geochemical analysis, it is believed that NaI(Tl) detectors must be used. Analytical procedures have been developed to obtain both qualitative and semiquantitative results from an interpretation of the measured NaI(Tl) pulse-height spectrum. Experiment results and the analytic procedure are presented. ?? 1970.

Detection of fast neutrons from shielded nuclear materials using a semiconductor alpha detector.

PubMed

Pöllänen, R; Siiskonen, T

2014-08-01

The response of a semiconductor alpha detector to fast (>1 MeV) neutrons was investigated by using measurements and simulations. A polyethylene converter was placed in front of the detector to register recoil protons generated by elastic collisions between neutrons and hydrogen nuclei of the converter. The developed prototype equipment was tested with shielded radiation sources. The low background of the detector and insensitivity to high-energy gamma rays above 1 MeV are advantages when the detection of neutron-emitting nuclear materials is of importance. In the case of a (252)Cf neutron spectrum, the intrinsic efficiency of fast neutron detection was determined to be 2.5×10(-4), whereas three-fold greater efficiency was obtained for a (241)AmBe neutron spectrum. Copyright © 2014 Elsevier Ltd. All rights reserved.

Development and Characterization of a High Sensitivity Segmented Fast Neutron Spectrometer (FaNS-2)

PubMed Central

Langford, T.J.; Beise, E.J.; Breuer, H.; Heimbach, C.R.; Ji, G.; Nico, J.S.

2016-01-01

We present the development of a segmented fast neutron spectrometer (FaNS-2) based upon plastic scintillator and 3He proportional counters. It was designed to measure both the flux and spectrum of fast neutrons in the energy range of few MeV to 1 GeV. FaNS-2 utilizes capture-gated spectroscopy to identify neutron events and reject backgrounds. Neutrons deposit energy in the plastic scintillator before capturing on a 3He nucleus in the proportional counters. Segmentation improves neutron energy reconstruction while the large volume of scintillator increases sensitivity to low neutron fluxes. A main goal of its design is to study comparatively low neutron fluxes, such as cosmogenic neutrons at the Earth's surface, in an underground environment, or from low-activity neutron sources. In this paper, we present details of its design and construction as well as its characterization with a calibrated 252Cf source and monoenergetic neutron fields of 2.5 MeV and 14 MeV. Detected monoenergetic neutron spectra are unfolded using a Singular Value Decomposition method, demonstrating a 5% energy resolution at 14 MeV. Finally, we discuss plans for measuring the surface and underground cosmogenic neutron spectra with FaNS-2. PMID:27226807

Characterization of boron coated vitreous carbon foam for neutron detection

NASA Astrophysics Data System (ADS)

Lavelle, C. M.; Deacon, Ryan M.; Hussey, Daniel S.; Coplan, Michael; Clark, Charles W.

2013-11-01

Reticulated vitreous carbon (RVC) foams coated with 3-11 μm thick layers of boron carbide (B4C) are experimentally characterized for use as an active material for neutron detection. The potential advantage of this material over thin films is that it can be fabricated in any shape and its porous structure may enhance the emission surface area for ionizing charged particles following thermal neutron capture. A coated foam is also advantageous because the neutron-absorbing material is only on the surface, which is more efficient for α particle emission on a per captured neutron basis. Measurements of the B4C layer thickness of an RVC coated foam, and determination of its elemental composition, are performed using scanning electron microscopy. Neutron transmission measurements using neutron radiography are presented and α particle emission from the coated foam in response to a moderated 252Cf thermal neutron source is demonstrated.

NIST Calibration of a Neutron Spectrometer ROSPEC.

PubMed

Heimbach, Craig

2006-01-01

A neutron spectrometer was acquired for use in the measurement of National Institute of Standards and Technology neutron fields. The spectrometer included options for the measurement of low and high energy neutrons, for a total measurement range from 0.01 eV up to 17 MeV. The spectrometer was evaluated in calibration fields and was used to determine the neutron spectrum of an Americium-Beryllium neutron source. The calibration fields used included bare and moderated (252)Cf, monoenergetic neutron fields of 2.5 MeV and 14 MeV, and a thermal-neutron beam. Using the calibration values determined in this exercise, the spectrometer gives a good approximation of the neutron spectrum, and excellent values for neutron fluence, for all NIST calibration fields. The spectrometer also measured an Americium-Beryllium neutron field in a NIST exposure facility and determined the field quite well. The spectrometer measured scattering effects in neutron spectra which previously could be determined only by calculation or integral measurements.

Neutron noise measurements at the Delphi subcritical assembly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szieberth, M.; Klujber, G.; Kloosterman, J. L.

2012-07-01

The paper presents the results and evaluations of a comprehensive set of neutron noise measurements on the Delphi subcritical assembly of the Delft Univ. of Technology. The measurements investigated the effect of different source distributions (inherent spontaneous fission and {sup 252}Cf) and the position of the detectors applied (both radially and vertically). The evaluation of the measured data has been performed by the variance-to-mean ratio (VTMR, Feynman-{alpha}), the autocorrelation (ACF, Rossi-{alpha}) and the cross-correlation (CCF) methods. The values obtained for the prompt decay constant show a strong bias, which depends both on the detector position and on the source distribution.more » This is due to the presence of higher modes in the system. It has been observed that the {alpha} value fitted is higher when the detector is close to the boundary of the core or to the {sup 252}Cf point-source. The higher alpha-modes have also been observed by fitting functions describing two alpha-modes. The successful set of measurement also provides a good basis for further theoretical investigations including the Monte Carlo simulation of the noise measurements and the calculation of the alpha-modes in the Delphi subcritical assembly. (authors)« less

Unfolding the neutron spectrum of a NE213 scintillator using artificial neural networks.

PubMed

Sharghi Ido, A; Bonyadi, M R; Etaati, G R; Shahriari, M

2009-10-01

Artificial neural networks technology has been applied to unfold the neutron spectra from the pulse height distribution measured with NE213 liquid scintillator. Here, both the single and multi-layer perceptron neural network models have been implemented to unfold the neutron spectrum from an Am-Be neutron source. The activation function and the connectivity of the neurons have been investigated and the results have been analyzed in terms of the network's performance. The simulation results show that the neural network that utilizes the Satlins transfer function has the best performance. In addition, omitting the bias connection of the neurons improve the performance of the network. Also, the SCINFUL code is used for generating the response functions in the training phase of the process. Finally, the results of the neural network simulation have been compared with those of the FORIST unfolding code for both (241)Am-Be and (252)Cf neutron sources. The results of neural network are in good agreement with FORIST code.

Neutron detection with a NaI spectrometer using high-energy photons

NASA Astrophysics Data System (ADS)

Holm, Philip; Peräjärvi, Kari; Sihvonen, Ari-Pekka; Siiskonen, Teemu; Toivonen, Harri

2013-01-01

Neutrons can be indirectly detected by high-energy photons. The performance of a 4″×4″×16″ NaI portal monitor was compared to a 3He-based portal monitor with a comparable cross-section of the active volume. Measurements were performed with bare and shielded 252Cf and AmBe sources. With an optimum converter and moderator structure for the NaI detector, the detection efficiencies and minimum detectable activities of the portal monitors were similar. The NaI portal monitor preserved its detection efficiency much better with shielded sources, making the method very interesting for security applications. For heavily shielded sources, the NaI detector was 2-3 times more sensitive than the 3He-based detector.

Study of a nTHGEM-based thermal neutron detector

NASA Astrophysics Data System (ADS)

Li, Ke; Zhou, Jian-Rong; Wang, Xiao-Dong; Xiong, Tao; Zhang, Ying; Xie, Yu-Guang; Zhou, Liang; Xu, Hong; Yang, Gui-An; Wang, Yan-Feng; Wang, Yan; Wu, Jin-Jie; Sun, Zhi-Jia; Hu, Bi-Tao

2016-07-01

With new generation neutron sources, traditional neutron detectors cannot satisfy the demands of the applications, especially under high flux. Furthermore, facing the global crisis in 3He gas supply, research on new types of neutron detector as an alternative to 3He is a research hotspot in the field of particle detection. GEM (Gaseous Electron Multiplier) neutron detectors have high counting rate, good spatial and time resolution, and could be one future direction of the development of neutron detectors. In this paper, the physical process of neutron detection is simulated with Geant4 code, studying the relations between thermal conversion efficiency, boron thickness and number of boron layers. Due to the special characteristics of neutron detection, we have developed a novel type of special ceramic nTHGEM (neutron THick GEM) for neutron detection. The performance of the nTHGEM working in different Ar/CO2 mixtures is presented, including measurements of the gain and the count rate plateau using a copper target X-ray source. A detector with a single nTHGEM has been tested for 2-D imaging using a 252Cf neutron source. The key parameters of the performance of the nTHGEM detector have been obtained, providing necessary experimental data as a reference for further research on this detector. Supported by National Natural Science Foundation of China (11127508, 11175199, 11205253, 11405191), Key Laboratory of Neutron Physics, CAEP (2013DB06, 2013BB04) and CAS (YZ201512)

[Shape of neutron energy].

PubMed

Nohtomi, Akihiro

2012-01-01

Cone-like acryl converters have been used for transforming the energy-distribution information of incident fast neutrons into the spatial-distribution information of recoil protons. The characteristics of neutron-proton conversion have been studied up to around 10MeV by using an imaging plate (IP). A notable and interesting signal enhancement due to recoil protons generated in an acrylic converter was observed on IP images for irradiation with a 252Cf source. A Monte Carlo calculation was carried out in order to understand the spatial distributions of the signal enhancement by recoil protons; these distributions promisingly involve the energy information of incident neutrons in principle. Consequently, it has been revealed that the neutron energy evaluation is surely possible by analyzing the spatial distributions of signal enhancement that is caused by recoil protons.

Micronucleus induction in Vicia faba roots. Part 2. Biological effects of neutrons below 1 cGy.

PubMed

Marshall, I; Bianchi, M

1983-08-01

A dose-effect relationship has been established for high-energy neutrons (maximum energy 600 MeV) within a dose range of 0.2 to 80 cGy and for low-energy neutrons produced by a 252Cf source (mean energy 2.35 MeV) for doses between 0.2 and 5 cGy. The frequency of micronuclei was found to increase linearly with dose. The relative biological effectiveness (r.b.e) values calculated using 60Co radiation as a reference were, in the high-dose region, 4.7 +/- 0.4 and 11.8 +/- 1.3 for the high- and low-energy neutrons, respectively. At doses below 1 cGy constant values of 25.4 +/- 4.4 and 63.7 +/- 12 were reached for the respective neutron energies.

Nonnegative Tensor Factorization Approach Applied to Fission Chamber’s Output Signals Blind Source Separation

NASA Astrophysics Data System (ADS)

Laassiri, M.; Hamzaoui, E.-M.; Cherkaoui El Moursli, R.

2018-02-01

Inside nuclear reactors, gamma-rays emitted from nuclei together with the neutrons introduce unwanted backgrounds in neutron spectra. For this reason, powerful extraction methods are needed to extract useful neutron signal from recorded mixture and thus to obtain clearer neutron flux spectrum. Actually, several techniques have been developed to discriminate between neutrons and gamma-rays in a mixed radiation field. Most of these techniques, tackle using analogue discrimination methods. Others propose to use some organic scintillators to achieve the discrimination task. Recently, systems based on digital signal processors are commercially available to replace the analog systems. As alternative to these systems, we aim in this work to verify the feasibility of using a Nonnegative Tensor Factorization (NTF) to blind extract neutron component from mixture signals recorded at the output of fission chamber (WL-7657). This last have been simulated through the Geant4 linked to Garfield++ using a 252Cf neutron source. To achieve our objective of obtaining the best possible neutron-gamma discrimination, we have applied the two different NTF algorithms, which have been found to be the best methods that allow us to analyse this kind of nuclear data.

Energy spectra unfolding of fast neutron sources using the group method of data handling and decision tree algorithms

NASA Astrophysics Data System (ADS)

Hosseini, Seyed Abolfazl; Afrakoti, Iman Esmaili Paeen

2017-04-01

Accurate unfolding of the energy spectrum of a neutron source gives important information about unknown neutron sources. The obtained information is useful in many areas like nuclear safeguards, nuclear nonproliferation, and homeland security. In the present study, the energy spectrum of a poly-energetic fast neutron source is reconstructed using the developed computational codes based on the Group Method of Data Handling (GMDH) and Decision Tree (DT) algorithms. The neutron pulse height distribution (neutron response function) in the considered NE-213 liquid organic scintillator has been simulated using the developed MCNPX-ESUT computational code (MCNPX-Energy engineering of Sharif University of Technology). The developed computational codes based on the GMDH and DT algorithms use some data for training, testing and validation steps. In order to prepare the required data, 4000 randomly generated energy spectra distributed over 52 bins are used. The randomly generated energy spectra and the simulated neutron pulse height distributions by MCNPX-ESUT for each energy spectrum are used as the output and input data. Since there is no need to solve the inverse problem with an ill-conditioned response matrix, the unfolded energy spectrum has the highest accuracy. The 241Am-9Be and 252Cf neutron sources are used in the validation step of the calculation. The unfolded energy spectra for the used fast neutron sources have an excellent agreement with the reference ones. Also, the accuracy of the unfolded energy spectra obtained using the GMDH is slightly better than those obtained from the DT. The results obtained in the present study have good accuracy in comparison with the previously published paper based on the logsig and tansig transfer functions.

A Sensitive, Selective, and Portable Detector for Contraband: The Compact Integrated Narcotics Detection Instrument

DOE Office of Scientific and Technical Information (OSTI.GOV)

T. O. Tuemer; L. Doan; C. W. Su

2000-06-04

This paper describes the design and operation of a Compact Integrated Narcotics Detection Instrument (CINDI), which utilizes neutrons emitted from {sup 252}Cf. Neutrons emitted from the front face of CINDI penetrate dense compartment barrier materials with little change in energy but are backscattered by hydrogen-rich materials such as drugs. CINDI has led to a new technology that shows promise for identifying the concealed contraband. Carriers such as vehicles, marine vessels, airplanes, containers, cargo, and luggage will be scanned using both neutron and gamma-ray sources. The signal from both the neutron and gamma-ray backscattering and/or transmission can be used simultaneously tomore » detect and possibly identify the contrabands it has been trained for.« less

Design and feasibility of a multi-detector neutron spectrometer for radiation protection applications based on thermoluminescent 6LiF:Ti,Mg (TLD-600) detectors

NASA Astrophysics Data System (ADS)

Lis, M.; Gómez-Ros, J. M.; Bedogni, R.; Delgado, A.

2008-01-01

The design of a neutron detector with spectrometric capability based on thermoluminescent (TL) 6LiF:Ti,Mg (TLD-600) dosimeters located along three perpendicular axis within a single polyethylene (PE) sphere has been analyzed. The neutron response functions have been calculated in the energy range from 10 -8 to 100 MeV with the Monte Carlo (MC) code MCNPX 2.5 and their shape and behaviour have been used to discuss a suitable configuration for an actual instrument. The feasibility of such a device has been preliminary evaluated by the simulation of exposure to 241Am-Be, bare 252Cf and Fe-PE moderated 252Cf sources. The expected accuracy in the evaluation of energy quantities has been evaluated using the unfolding code FRUIT. The obtained results together with additional calculations performed using MAXED and GRAVEL codes show the spectrometric capability of the proposed design for radiation protection applications, especially in the range 1 keV-20 MeV.

Octupole Deformation Bands of πh11/2 in Neutron-Rich 145,147La Nuclei

NASA Astrophysics Data System (ADS)

Zhu, Sheng-jiang; S, Zhu J.; Wang, Mu-ge; J, Hamilton H.; A, Ramayya V.; B, Babu R. S.; W, Ma C.; Long, Gui-lu; Zhu, Ling-yan; Li, Ming; A, Sakhaee; Gan, Cui-yun; Yang, Li-ming; J, Komicki; J, Cole D.; R, Aryaeinejad; M, Drigert W.; J, Rasmussen O.; M, Stoyer A.; S, Chu Y.; K, Gregorich E.; M, Mohar F.; S, Prussin G.; I, Lee Y.; Yu, Oganessian Ts; G, Ter-Akopian M.; A, Daniel V.

1999-03-01

Octupole deformation bands built on πh11/2 orbital in neutron-rich odd-Z 145,147La nuclei have been investigated by measuring the prompt γ-rays emitted from the 252Cf source. The alternating parity band structures and strong E1 transitions observed between negative- and positive-parity bands in both nuclei indicate the octupole deformation enhanced by the h11/2 single proton coupling. According to observed energy displacements the octupole deformation becomes stable at the intermediate spin states.

Development of a lithium fluoride zinc sulfide based neutron multiplicity counter

NASA Astrophysics Data System (ADS)

Cowles, Christian; Behling, Spencer; Baldez, Phoenix; Folsom, Micah; Kouzes, Richard; Kukharev, Vladislav; Lintereur, Azaree; Robinson, Sean; Siciliano, Edward; Stave, Sean; Valdez, Patrick

2018-04-01

The feasibility of a full-scale lithium fluoride zinc sulfide (LiF/ZnS) based neutron multiplicity counter has been demonstrated. The counter was constructed of modular neutron detecting stacks that each contain five sheets of LiF/ZnS interleaved between six sheets of wavelength shifting plastic with a photomultiplier tube on each end. Twelve such detector stacks were placed around a sample chamber in a square arrangement with lithiated high-density polyethylene blocks in the corners to reflect high-energy neutrons and capture low-energy neutrons. The final system design was optimized via modeling and small-scale test. Measuring neutrons from a 252Cf source, the counter achieved a 36% neutron detection efficiency (ɛ) and an 11 . 7 μs neutron die-away time (τ) for a doubles figure-of-merit (ɛ2 / τ) of 109. This is the highest doubles figure-of-merit measured to-date for a 3He-free neutron multiplicity counter.

Benchmarking Data for the Proposed Signature of Used Fuel Casks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rauch, Eric Benton

2016-09-23

A set of benchmarking measurements to test facets of the proposed extended storage signature was conducted on May 17, 2016. The measurements were designed to test the overall concept of how the proposed signature can be used to identify a used fuel cask based only on the distribution of neutron sources within the cask. To simulate the distribution, 4 Cf-252 sources were chosen and arranged on a 3x3 grid in 3 different patterns and raw neutron totals counts were taken at 6 locations around the grid. This is a very simplified test of the typical geometry studied previously in simulationmore » with simulated used nuclear fuel.« less

Perforated semiconductor neutron detectors for battery operated portable modules

NASA Astrophysics Data System (ADS)

McGregor, Douglas S.; Bellinger, Steven L.; Bruno, David; McNeil, Walter J.; Patterson, Eric; Shultis, J. Kenneth; Solomon, C. J.; Unruh, Troy

2007-09-01

Perforated semiconductor diode detectors have been under development for several years at Kansas State University for a variety of neutron detection applications. The fundamental device configuration is a pin diode detector fabricated from high-purity float zone refined Si wafers. Perforations are etched into the diode surface with inductively-coupled plasma (ICP) reactive ion etching (RIE) and backfilled with 6LiF neutron reactive material. The perforation shapes and depths can be optimized to yield a flat response to neutrons over a wide variation of angles. The prototype devices delivered over 3.8% thermal neutron detection efficiency while operating on only 15 volts. The highest efficiency devices thus far have delivered over 12% thermal neutron detection efficiency. The miniature devices are 5.6 mm in diameter and require minimal power to operate, ranging from 3.3 volts to 15 volts, depending upon the amplifying electronics. The battery operated devices have been incorporated into compact modules with a digital readout. Further, the new modules have incorporated wireless readout technology and can be monitored remotely. The neutron detection modules can be used for neutron dosimetry and neutron monitoring. When coupled with high-density polyethylene, the detectors can be used to measure fission neutrons from spontaneous fission sources. Monto Carlo analysis indicates that the devices can be used in cargo containers as a passive search tool for spontaneous fission sources, such as 240Pu. Measurements with a 252Cf source are being conducted for verification.

Cross-correlation measurements with the EJ-299-33 plastic scintillator

NASA Astrophysics Data System (ADS)

Bourne, Mark M.; Whaley, Jeff; Dolan, Jennifer L.; Polack, John K.; Flaska, Marek; Clarke, Shaun D.; Tomanin, Alice; Peerani, Paolo; Pozzi, Sara A.

2015-06-01

New organic-plastic scintillation compositions have demonstrated pulse-shape discrimination (PSD) of neutrons and gamma rays. We present cross-correlation measurements of 252Cf and mixed uranium-plutonium oxide (MOX) with the EJ-299-33 plastic scintillator. For comparison, equivalent measurements were performed with an EJ-309 liquid scintillator. Offline, digital PSD was applied to each detector. These measurements show that EJ-299-33 sacrifices a factor of 5 in neutron-neutron efficiency relative to EJ-309, but could still utilize the difference in neutron-neutron efficiency and neutron single-to-double ratio to distinguish 252Cf from MOX. These measurements were modeled with MCNPX-PoliMi, and MPPost was used to convert the detailed collision history into simulated cross-correlation distributions. MCNPX-PoliMi predicted the measured 252Cf cross-correlation distribution for EJ-309 to within 10%. Greater photon uncertainty in the MOX sample led to larger discrepancy in the simulated MOX cross-correlation distribution. The modeled EJ-299-33 plastic also gives reasonable agreement with measured cross-correlation distributions, although the MCNPX-PoliMi model appears to under-predict the neutron detection efficiency.

Experimental study of boron-coated straws with a neutron source

NASA Astrophysics Data System (ADS)

Xie, Zhaoyang; Zhou, Jianrong; Song, Yushou; Lacy, Jeffrey L.; Sun, Liang; Sun, Zhijia; Hu, Bitao; Chen, Yuanbo

2018-04-01

Multiple types of high quality neutron detectors are proposed for the first phase of the China Spallation Neutron Source (CSNS), which will be commissioned in 2018. Considering the shortage of 3He supply, a detector module composed of 49 boron-coated straws (BCS) was developed by Proportional Technologies Inc. (PTI). Each straw has a length of 1000 mm and a diameter of 7.5 mm. Seven straws are tightly packed in a tube, and seven tubes are organized in a row to form a detector module. The charge division method is used for longitudinal positioning. A specific readout system was utilized to output the signal and simultaneously encode each straw. The performance of this detector module was studied using a moderated 252Cf source at the Institute of High Energy Physics (IHEP). The signal amplitude spectrum indicates its n-gamma discrimination capability. Despite the complex readout method, a longitudinal resolution of FWHM=6.1 ± 0.5 mm was obtained. The three-dimensional positioning ability qualifies this BCS detector module as a promising detector for small angle neutron scattering.

Neutron and gamma-ray energy reconstruction for characterization of special nuclear material

DOE PAGES

Clarke, Shaun D.; Hamel, Michael C.; Di fulvio, Angela; ...

2017-06-30

Characterization of special nuclear material may be performed using energy spectroscopy of either the neutron or gamma-ray emissions from the sample. Gamma-ray spectroscopy can be performed relatively easily using high-resolution semiconductors such as high-purity germanium. Neutron spectroscopy, by contrast, is a complex inverse problem. Here, results are presented for 252Cf and PuBe energy spectra unfolded using a single EJ309 organic scintillator; excellent agreement is observed with the reference spectra. Neutron energy spectroscopy is also possible using a two-plane detector array, whereby time-offlight kinematics can be used. With this system, energy spectra can also be obtained as a function of position.more » Finally, spatial-dependent energy spectra are presented for neutron and gamma-ray sources that are in excellent agreement with expectations.« less

Neutron and gamma-ray energy reconstruction for characterization of special nuclear material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clarke, Shaun D.; Hamel, Michael C.; Di fulvio, Angela

Characterization of special nuclear material may be performed using energy spectroscopy of either the neutron or gamma-ray emissions from the sample. Gamma-ray spectroscopy can be performed relatively easily using high-resolution semiconductors such as high-purity germanium. Neutron spectroscopy, by contrast, is a complex inverse problem. Here, results are presented for 252Cf and PuBe energy spectra unfolded using a single EJ309 organic scintillator; excellent agreement is observed with the reference spectra. Neutron energy spectroscopy is also possible using a two-plane detector array, whereby time-offlight kinematics can be used. With this system, energy spectra can also be obtained as a function of position.more » Finally, spatial-dependent energy spectra are presented for neutron and gamma-ray sources that are in excellent agreement with expectations.« less

CHARACTERIZATION OF A THIN SILICON SENSOR FOR ACTIVE NEUTRON PERSONAL DOSEMETERS.

PubMed

Takada, M; Nunomiya, T; Nakamura, T; Matsumoto, T; Masuda, A

2016-09-01

A thin silicon sensor has been developed for active neutron personal dosemeters for use by aircrews and first responders. This thin silicon sensor is not affected by the funneling effect, which causes detection of cosmic protons and over-response to cosmic neutrons. There are several advantages to the thin silicon sensor: a decrease in sensitivity to gamma rays, an improvement of the energy detection limit for neutrons down to 0.8 MeV and an increase in the sensitivity to fast neutrons. Neutron response functions were experimentally obtained using 2.5 and 5 MeV monoenergy neutron beams and a (252)Cf neutron source. Simulation results using the Monte Carlo N-Particle transport code agree quite well with the experimental ones when an energy deposition region shaped like a circular truncated cone is used in place of a cylindrical region. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Detecting special nuclear material using a neutron time projection chamber

NASA Astrophysics Data System (ADS)

Carosi, G.; Bernstein, A.; Bowden, N.; Burke, J.; Carter, D.; Foxe, M.; Heffner, M.; Jovanovic, I.; Mintz, J.; O'Malley, P.

2010-02-01

Time projection chambers are 3-dimensional charged particle cameras based on drifting ionization tracks at a known velocity onto an electronic readout plane. These instruments are capable of detecting fast neutrons which are unique signatures of special nuclear material with low natural background rates. Here we describe a neutron Time Projection Chamber (nTPC) developed at Lawrence Livermore National Laboratory (LLNL) which has demonstrated directional sensitivity to fission neutrons along with high rejection of background gamma-ray and electron events. Using a combination hydrogen/methane drift gas at several atmospheres we've demonstrated the ability to point to a Cf-252 source simulating 6kg of weapons grade plutonium at 10's of meters with one hour integration time. Plans for future field deployable devices will also be outlined. )

Development of a technique using MCNPX code for determination of nitrogen content of explosive materials using prompt gamma neutron activation analysis method

NASA Astrophysics Data System (ADS)

Nasrabadi, M. N.; Bakhshi, F.; Jalali, M.; Mohammadi, A.

2011-12-01

Nuclear-based explosive detection methods can detect explosives by identifying their elemental components, especially nitrogen. Thermal neutron capture reactions have been used for detecting prompt gamma 10.8 MeV following radioactive neutron capture by 14N nuclei. We aimed to study the feasibility of using field-portable prompt gamma neutron activation analysis (PGNAA) along with improved nuclear equipment to detect and identify explosives, illicit substances or landmines. A 252Cf radio-isotopic source was embedded in a cylinder made of high-density polyethylene (HDPE) and the cylinder was then placed in another cylindrical container filled with water. Measurements were performed on high nitrogen content compounds such as melamine (C3H6N6). Melamine powder in a HDPE bottle was placed underneath the vessel containing water and the neutron source. Gamma rays were detected using two NaI(Tl) crystals. The results were simulated with MCNP4c code calculations. The theoretical calculations and experimental measurements were in good agreement indicating that this method can be used for detection of explosives and illicit drugs.

A feasibility study of [sup 252]Cf neutron brachytherapy, cisplatin + 5-FU chemo-adjuvant and accelerated hyperfractionated radiotherapy for advanced cervical cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murayama, Y.; Wierzbicki, J.; Bowen, M.G.

The purpose was to evaluate the feasibility and toxicity of [sup 252]Cf neutron brachytherapy combined with hyperaccelerated chemoradiotherapy for Stage III and IV cervical cancers. Eleven patients with advanced Stage IIIB-IVA cervical cancers were treated with [sup 252]Cf neutron brachytherapy in an up-front schedule followed by cisplatin (CDDP; 50 mg/m[sup 2]) chemotherapy and hyperfractionated accelerated (1.2 Gy bid) radiotherapy given concurrently with intravenous infusion of 5-Fluorouracil (5-FU) (1000 mg/m[sup 2]/day [times] 4 days) in weeks 1 and 4 with conventional radiation (weeks 2, 3, 5, and 6). Total dose at a paracervical point A isodose surface was 80-85 Gy-eq bymore » external and intracavitary therapy and 60 Gy at the pelvic sidewalls. Patients tolerated the protocol well. There was 91% compliance with the chemotherapy and full compliance with the [sup 252]Cf brachytherapy and the external beam radiotherapy. There were no problems with acute chemo or radiation toxicity. One patient developed a rectovaginal fistula (Grade 3-4 RTOG criteria) but no other patients developed significant late cystitis, proctitis or enteritis. There was complete response (CR) observed in all cases. With mean follow-up to 26 months, local control has been achieved with 90% actuarial 3-year survival with no evidence of disease (NED). [sup 252]Cf neutrons can be combined with cisplatin and 5-FU infusion chemotherapy plus hyperaccelerated chemoradiotherapy without unusual side effects or toxicity and with a high local response and tumor control rate. Further study of [sup 252]Cf neutron-chemoradiotherapy for advanced and bulky cervical cancer are indicated. The authors found chemotherapy was more effective with the improved local tumor control. 18 refs., 2 tabs.« less

Development of prototype induced-fission-based Pu accountancy instrument for safeguards applications.

PubMed

Seo, Hee; Lee, Seung Kyu; An, Su Jung; Park, Se-Hwan; Ku, Jeong-Hoe; Menlove, Howard O; Rael, Carlos D; LaFleur, Adrienne M; Browne, Michael C

2016-09-01

Prototype safeguards instrument for nuclear material accountancy (NMA) of uranium/transuranic (U/TRU) products that could be produced in a future advanced PWR fuel processing facility has been developed and characterized. This is a new, hybrid neutron measurement system based on fast neutron energy multiplication (FNEM) and passive neutron albedo reactivity (PNAR) methods. The FNEM method is sensitive to the induced fission rate by fast neutrons, while the PNAR method is sensitive to the induced fission rate by thermal neutrons in the sample to be measured. The induced fission rate is proportional to the total amount of fissile material, especially plutonium (Pu), in the U/TRU product; hence, the Pu amount can be calibrated as a function of the induced fission rate, which can be measured using either the FNEM or PNAR method. In the present study, the prototype system was built using six (3)He tubes, and its performance was evaluated for various detector parameters including high-voltage (HV) plateau, efficiency profiles, dead time, and stability. The system's capability to measure the difference in the average neutron energy for the FNEM signature also was evaluated, using AmLi, PuBe, (252)Cf, as well as four Pu-oxide sources each with a different impurity (Al, F, Mg, and B) and producing (α,n) neutrons with different average energies. Future work will measure the hybrid signature (i.e., FNEM×PNAR) for a Pu source with an external interrogating neutron source after enlarging the cavity size of the prototype system to accommodate a large-size Pu source (~600g Pu). Copyright © 2016 Elsevier Ltd. All rights reserved.

Optimizing moderation of He-3 neutron detectors for shielded fission sources

DOE PAGES

Rees, Lawrence B.; Czirr, J. Bart

2012-07-10

Abstract: The response of 3-He neutron detectors is highly dependent on the amount of moderator incorporated into the detector system. If there is too little moderation, neutrons will not react with the 3-He. If there is too much moderation, neutrons will not reach the 3-He. In applications for portal or border monitors where 3He detectors are used to interdict illicit Importation of plutonium, the fission source is always shielded to some extent. Since the energy distribution of neutrons emitted from the source depends on the amount and type of shielding present, the optimum placement of moderating material around 3-He tubesmore » is a function of shielding. In this paper, we use Monte Carlo techniques to model the response of 3-He tubes placed in polyethylene boxes for moderation. To model the shielded fission neutron source, we use a 252-Cf source placed in the center of spheres of water of varying radius. Detector efficiency as a function of box geometry and shielding are explored. We find that increasing the amount of moderator behind and to the sides of the detector generally improves the detector response, but that benefits are limited if the thickness of the polyethylene moderator is greater than about 5-7 cm. The thickness of the moderator in front of the 3He tubes, however, is very important. For bare sources, about 5-6 cm of moderator is optimum, but as the shielding increases, the optimum thickness of this moderator decreases to 0-1 cm. A two-tube box with a moderator thickness of 5 cm in front of the first tube and a thickness of 1 cm in front of the second tube is proposed to improve the detector's sensitivity to lower-energy neutrons.« less

In-vivo assessment of total body protein in rats by prompt-γ neutron activation analysis

NASA Astrophysics Data System (ADS)

Stamatelatos, Ion E.; Boozer, Carol N.; Ma, Ruimei; Yasumura, Seiichi

1997-02-01

A prompt-(gamma) neutron activation analysis facility for in vivo determination of total body protein (TBP) in rats has been designed. TBP is determined in vivo by assessment of total body nitrogen. The facility is based on a 252Cf radionuclide neutron source within a heavy water moderator assembly and two NaI(Tl) scintillation detectors. The in vivo precision of the technique, as estimated by three repeated measurements of 15 rats is 6 percent, for a radiation dose equivalent of 60 mSv. The radiation dose per measurement is sufficiently low to enable serial measurements on the same animal. MCNP-4A Monte Carlo transport code was utilized to calculate thermal neutron flux correction factors to account for differences in size and shape of the rats and calibration phantoms. Good agrement was observed in comparing body nitrogen assessment by prompt-(gamma) neutron activation and chemical carcass analysis.

Apparatus for irradiating a continuously flowing stream of fluid. [For neutron activation analysis

DOEpatents

Speir, L.G.; Adams, E.L.

1982-05-13

An apparatus for irradiating a continuously flowing stream of fluid is disclosed. The apparatus consists of a housing having a spherical cavity and a spherical moderator containing a radiation source positioned within the spherical cavity. The spherical moderator is of lesser diameter than the spherical cavity so as to define a spherical annular volume around the moderator. The housing includes fluid intake and output conduits which open onto the spherical cavity at diametrically opposite positions. Fluid flows through the cavity around the spherical moderator and is uniformly irradiated due to the 4..pi.. radiation geometry. The irradiation source, for example a /sup 252/Cf neutron source, is removable from the spherical moderator through a radial bore which extends outwardly to an opening on the outside of the housing. The radiation source may be routinely removed without interrupting the flow of fluid or breaching the containment of the fluid.

Angular correlations in the prompt neutron emission in spontaneous fission of 252Cf

NASA Astrophysics Data System (ADS)

Kopatch, Yuri; Chietera, Andreina; Stuttgé, Louise; Gönnenwein, Friedrich; Mutterer, Manfred; Gagarski, Alexei; Guseva, Irina; Dorvaux, Olivier; Hanappe, Francis; Hambsch, Franz-Josef

2017-09-01

An experiment aiming at the detailed investigation of angular correlations in the neutron emission from spontaneous fission of 252Cf has been performed at IPHC Strasbourg using the angle-sensitive double ionization chamber CODIS for measuring fission fragments and a set of 60 DEMON scintillator counters for neutron detection. The main aim of the experiment is to search for an anisotropy of neutron emission in the center-of-mass system of the fragments. The present status of the data analysis and the full Monte-Carlo simulation of the experiment are reported in the present paper.

Design and verification of the shielding around the new Neutron Standards Laboratory (LPN) at CIEMAT.

PubMed

Méndez-Villafañe, R; Guerrero, J E; Embid, M; Fernández, R; Grandio, R; Pérez-Cejuela, P; Márquez, J L; Alvarez, F; Ortego, P

2014-10-01

The construction of the new Neutron Standards Laboratory at CIEMAT (Laboratorio de Patrones Neutrónicos) has been finalised and is ready to provide service. The facility is an ∼8 m×8 m×8 m irradiation vault, following the International Organization for Standardization 8529 recommendations. It relies on several neutron sources: a 5-GBq (5.8× 10(8) s(-1)) (252)Cf source and two (241)Am-Be neutron sources (185 and 11.1 GBq). The irradiation point is located 4 m over the ground level and in the geometrical centre of the room. Each neutron source can be moved remotely from its storage position inside a water pool to the irradiation point. Prior to this, an important task to design the neutron shielding and to choose the most appropriate materials has been developed by the Radiological Security Unit and the Ionizing Radiations Metrology Laboratory. MCNPX was chosen to simulate the irradiation facility. With this information the walls were built with a thickness of 125 cm. Special attention was put on the weak points (main door, air conditioning system, etc.) so that the ambient dose outside the facility was below the regulatory limits. Finally, the Radiation Protection Unit carried out a set of measurements in specific points around the installation with an LB6411 neutron monitor and a Reuter-Stokes high-pressure ion chamber to verify experimentally the results of the simulation. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Studies on new neutron-sensitive dosimeters using an optically stimulated luminescence technique

NASA Astrophysics Data System (ADS)

Kulkarni, M. S.; Luszik-Bhadra, M.; Behrens, R.; Muthe, K. P.; Rawat, N. S.; Gupta, S. K.; Sharma, D. N.

2011-07-01

The neutron response of detectors prepared using α-Al 2O 3:C phosphor developed using a melt processing technique and mixed with neutron converters was studied in monoenergetic neutron fields. The detector pellets were arranged in two different pairs: α-Al 2O 3:C + 6LiF/α-Al 2O 3:C + 7LiF and α-Al 2O 3:C + high-density polyethylene/α-Al 2O 3:C + Teflon, for neutron dosimetry using albedo and recoil proton techniques. The optically stimulated luminescence response of the Al 2O 3:C + 6,7LiF dosimeter to radiation from a 252Cf source was 0.21, in terms of personal dose equivalent Hp(10) and relative to radiation from a 137Cs source. This was comparable to results obtained with similar detectors prepared using commercially available α-Al 2O 3:C phosphor. The Hp(10) response of the α-Al 2O 3:C + 6,7LiF dosimeters was found to decrease by more than two orders of magnitude with increasing neutron energy, as expected for albedo dosimeters. The response of the α-Al 2O 3:C + high-density polyethylene/α-Al 2O 3:C + Teflon dosimeters was small, of the order of 1% to 2% in terms of Hp(10) and relative to radiation from a 137Cs source, for neutron energies greater than 1 MeV.

Neutron-neutron angular correlations in spontaneous fission of 252Cf and 240Pu

NASA Astrophysics Data System (ADS)

Verbeke, J. M.; Nakae, L. F.; Vogt, R.

2018-04-01

Background: Angular anisotropy has been observed between prompt neutrons emitted during the fission process. Such an anisotropy arises because the emitted neutrons are boosted along the direction of the parent fragment. Purpose: To measure the neutron-neutron angular correlations from the spontaneous fission of 252Cf and 240Pu oxide samples using a liquid scintillator array capable of pulse-shape discrimination. To compare these correlations to simulations combining the Monte Carlo radiation transport code MCNPX with the fission event generator FREYA. Method: Two different analysis methods were used to study the neutron-neutron correlations with varying energy thresholds. The first is based on setting a light output threshold while the second imposes a time-of-flight cutoff. The second method has the advantage of being truly detector independent. Results: The neutron-neutron correlation modeled by FREYA depends strongly on the sharing of the excitation energy between the two fragments. The measured asymmetry enabled us to adjust the FREYA parameter x in 240Pu, which controls the energy partition between the fragments and is so far inaccessible in other measurements. The 240Pu data in this analysis was the first available to quantify the energy partition for this isotope. The agreement between data and simulation is overall very good for 252Cf(sf ) and 240Pu(sf ) . Conclusions: The asymmetry in the measured neutron-neutron angular distributions can be predicted by FREYA. The shape of the correlation function depends on how the excitation energy is partitioned between the two fission fragments. Experimental data suggest that the lighter fragment is disproportionately excited.

A USB-2 based portable data acquisition system for detector development and nuclear research

NASA Astrophysics Data System (ADS)

Jiang, Hao; Ojaruega, M.; Becchetti, F. D.; Griffin, H. C.; Torres-Isea, R. O.

2011-10-01

A highly portable high-speed CAMAC data acquisition system has been developed using Kmax software (Sparrow, Inc.) for Macintosh laptop and tower computers. It uses a USB-2 interface to the CAMAC crate controller with custom-written software drivers. Kmax permits 2D parameter gating and specific algorithms have been developed to facilitate the rapid evaluation of various multi-element nuclear detectors for energy and time-of-flight measurements. This includes tests using neutrons from 252Cf and a 2.5 MeV neutron generator as well as standard gamma calibration sources such as 60Co and 137Cs. In addition, the system has been used to measure gamma-gamma coincidences over extended time periods using radioactive sources (e.g., Ra-228, Pa-233, Np-237, and Am-243).

SHIELDING AND DETECTOR RESPONSE CALCULATIONS PERTAINING TO CATEGORY 1 QUANTITIES OF PLUTONIUM AND HAND-HELD PLASTIC SCINTILLATORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Couture, A.

2013-06-07

Nuclear facilities sometimes use hand-held plastic scintillator detectors to detect attempts to divert special nuclear material in situations where portal monitors are impractical. MCNP calculations have been performed to determine the neutron and gamma radiation field arising from a Category I quantity of weapons-grade plutonium in various shielding configurations. The shields considered were composed of combinations of lead and high-density polyethylene such that the mass of the plutonium plus shield was 22.7 kilograms. Monte-Carlo techniques were also used to determine the detector response to each of the shielding configurations. The detector response calculations were verified using field measurements of high-,more » medium-, and low- energy gamma-ray sources as well as a Cf-252 neutron source.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meierbachtol, K.; Tovesson, F.; Shields, D.

We developed the SPectrometer for Ion DEtermination in fission Research (SPIDER) for measuring mass yield distributions of fission products from spontaneous and neutron-induced fission. The 2E–2v method of measuring the kinetic energy (E) and velocity (v) of both outgoing fission products has been utilized, with the goal of measuring the mass of the fission products with an average resolution of 1 atomic mass unit (amu). Moreover, the SPIDER instrument, consisting of detector components for time-of-flight, trajectory, and energy measurements, has been assembled and tested using 229Th and 252Cf radioactive decay sources. For commissioning, the fully assembled system measured fission productsmore » from spontaneous fission of 252Cf. Individual measurement resolutions were met for time-of-flight (250 ps FWHM), spacial resolution (2 mm FHWM), and energy (92 keV FWHM for 8.376 MeV). Finally, these mass yield results measured from 252Cf spontaneous fission products are reported from an E–v measurement.« less

Aircraft Radiation Shield Experiments--Preflight Laboratory Testing

NASA Technical Reports Server (NTRS)

Singleterry, Robert C., Jr.; Shinn, Judy L.; Wilson, John W.; Maiden, Donald L.; Thibeault, Sheila A.; Badavi, Francis F.; Conroy, Thomas; Braby, Leslie

1999-01-01

In the past, measurements onboard a research Boeing 57F (RB57-F) aircraft have demonstrated that the neutron environment within the aircraft structure is greater than that in the local external environment. Recent studies onboard Boeing 737 commercial flights have demonstrated cabin variations in radiation exposure up to 30 percent. These prior results were the basis of the present study to quantify the potential effects of aircraft construction materials on the internal exposures of the crew and passengers. The present study constitutes preflight measurements using an unmoderated Cf-252 fission neutron source to quantify the effects of three current and potential aircraft materials (aluminum, titanium, and graphite-epoxy composite) on the fast neutron flux. Conclusions about the effectiveness of the three selected materials for radiation shielding must wait until testing in the atmosphere is complete; however, it is clear that for shielding low-energy neutrons, the composite material is an improved shielding material over aluminum or titanium.

Investigation of the response of a neutron-Hand monitor dedicated to the powder diffractometer at CENM-Maamora

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messous, M.Y.; Belhorma, B.; Labrim, H.

2015-07-01

Neutrons are used for the study of condensed matter. A neutron beam can indeed easily penetrate the solid material and undergo diffraction phenomena. Analysis of the diffused neutrons allows studying the atomic structure of crossed material. Their neutral electric charge makes them nondestructive probe of a great interest. In general, the size of the powder samples is very small and therefore the centering of the beam on these is very crucial. It is in this context we proceed to test a portable neutron monitor for centering and checking beam leak around the shielding to be installed around the diffractometer inmore » TRIGA Mark II of CENM. It's consisting of a scintillation neutron detector NE426 ({sup 6}LiF + ZnS (Ag)) with electronic module and data acquisition system. The effect of radiation from radioactive neutrons source {sup 252}Cf is shown. Sensitivity and differential linearity are also performed. This study indicates several advantages of this detector with very good detection sensitivity and excellent stability during the counting time. (authors)« less

Magnetic Excitations in Polyoxotungstate-Supported Lanthanoid Single-Molecule Magnets: An Inelastic Neutron Scattering and ab Initio Study.

PubMed

Vonci, Michele; Giansiracusa, Marcus J; Van den Heuvel, Willem; Gable, Robert W; Moubaraki, Boujemaa; Murray, Keith S; Yu, Dehong; Mole, Richard A; Soncini, Alessandro; Boskovic, Colette

2017-01-03

Inelastic neutron scattering (INS) has been used to investigate the crystal field (CF) magnetic excitations of the analogs of the most representative lanthanoid-polyoxometalate single-molecule magnet family: Na 9 [Ln(W 5 O 18 ) 2 ] (Ln = Nd, Tb, Ho, Er). Ab initio complete active space self-consistent field/restricted active space state interaction calculations, extended also to the Dy analog, show good agreement with the experimentally determined low-lying CF levels, with accuracy better in most cases than that reported for approaches based only on simultaneous fitting to CF models of magnetic or spectroscopic data for isostructural Ln families. In this work we demonstrate the power of a combined spectroscopic and computational approach. Inelastic neutron scattering has provided direct access to CF levels, which together with the magnetometry data, were employed to benchmark the ab initio results. The ab initio determined wave functions corresponding to the CF levels were in turn employed to assign the INS transitions allowed by selection rules and interpret the observed relative intensities of the INS peaks. Ultimately, we have been able to establish the relationship between the wave function composition of the CF split Ln III ground multiplets and the experimentally measured magnetic and spectroscopic properties for the various analogs of the Na 9 [Ln(W 5 O 18 ) 2 ] family.

Developments toward Understanding and Improving the Low Energy Measurement Capabilities of a Fission Time Projection Chamber

NASA Astrophysics Data System (ADS)

Bundgaard, Jeremy J.

Nuclear physicists have been recently called upon for new, high precision fission measurements to improve existing fission models, ultimately enabling engineers to design next generation reactors as well as guarding the nation's stockpile. In response, a resurgence in fission research is aimed at developing detectors to design and build new experiments to meet these needs. The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) collaboration has developed the fission Time Projection Chamber (fissionTPC) to measure neutron induced fission with unprecedented precision. The fissionTPC is annually deployed to the Los Alamos Neutron Science Center LANSCE where it operates with a neutron beam passing axially through the drift volume, irradiating heavy actinide targets to induce fission. The fissionTPC was developed at the Lawrence Livermore National Laboratory's (LLNL) TPC lab, where it is tested with spontaneous fission (SF) from radioactive sources, typically 252Cf and 244Cm, to characterize detector response, improve performance, and evolve the design. One of the experiments relevant for both nuclear energy and nonproliferation is to measure the neutron induced fission of 239Pu, which exhibits a high alpha activity, generating a large unwanted background for the fission measurements. The ratio of alpha to fission present in our neutron induced fission measurement of 239Pu is on the same order of magnitude as the 244Cm alpha/SF branching ratio. The high alpha rate required the TPC to be triggering on fission signals during beam time and we set out to build a trigger system, which, using 244Cm to produce a similar alpha to fission ratio as 239Pu in the neutron beam, we successfully demonstrated the viability of this approach. The trigger design has been evolved for use in NIFFTE's current measurements at LANSCE. In addition to several hardware and software contributions in the development and operation of the fissionTPC, a central purpose of this thesis was also to develop analyses to demonstrate the fissionTPC's performance abilities/limitations in measuring the alpha/SF branching ratio of 252Cf and 244Cm. Our method results in benchmarking the fissionTPC's ability to produce a competitive alpha/SF ratio for 252Cf with sub-percent precision.

Neutron-fragment and Neutron-neutron Correlations in Low-energy Fission

NASA Astrophysics Data System (ADS)

Lestone, J. P.

2016-01-01

A computational method has been developed to simulate neutron emission from thermal-neutron induced fission of 235U and from spontaneous fission of 252Cf. Measured pre-emission mass-yield curves, average total kinetic energies and their variances, both as functions of mass split, are used to obtain a representation of the distribution of fragment velocities. Measured average neutron multiplicities as a function of mass split and their dependence on total kinetic energy are used. Simulations can be made to reproduce measured factorial moments of neutron-multiplicity distributions with only minor empirical adjustments to some experimental inputs. The neutron-emission spectra in the rest-frame of the fragments are highly constrained by ENDF/B-VII.1 prompt-fission neutron-spectra evaluations. The n-f correlation measurements of Vorobyev et al. (2010) are consistent with predictions where all neutrons are assumed to be evaporated isotropically from the rest frame of fully accelerated fragments. Measured n-f and n-n correlations of others are a little weaker than the predictions presented here. These weaker correlations could be used to infer a weak scission-neutron source. However, the effect of neutron scattering on the experimental results must be studied in detail before moving away from a null hypothesis that all neutrons are evaporated from the fragments.

Stabilization of Particle Discrimination Efficiencies for Neutron Spectrum Unfolding With Organic Scintillators

NASA Astrophysics Data System (ADS)

Lawrence, Chris C.; Polack, J. K.; Febbraro, Michael; Kolata, J. J.; Flaska, Marek; Pozzi, S. A.; Becchetti, F. D.

2017-02-01

The literature discussing pulse-shape discrimination (PSD) in organic scintillators dates back several decades. However, little has been written about PSD techniques that are optimized for neutron spectrum unfolding. Variation in n-γ misclassification rates and in γ/n ratio of incident fields can distort the neutron pulse-height response of scintillators and these distortions can in turn cause large errors in unfolded spectra. New applications in arms-control verification call for detection of lower-energy neutrons, for which PSD is particularly problematic. In this article, we propose techniques for removing distortions on pulse-height response that result from the merging of PSD distributions in the low-pulse-height region. These techniques take advantage of the repeatable shapes of PSD distributions that are governed by the counting statistics of scintillation-photon populations. We validate the proposed techniques using accelerator-based time-of-flight measurements and then demonstrate them by unfolding the Watt spectrum from measurement with a 252Cf neutron source.

Design of a transportable high efficiency fast neutron spectrometer

DOE PAGES

Roecker, C.; Bernstein, A.; Bowden, N. S.; ...

2016-04-12

A transportable fast neutron detection system has been designed and constructed for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The transportability of the spectrometer reduces the detector-related systematic bias between different neutron spectra and flux measurements, which allows for the comparison of measurements above or below ground. The spectrometer will measure neutron fluxes that are of prohibitively low intensity compared to the site-specific background rates targeted by other transportable fast neutron detection systems. To measure low intensity high-energy neutron fluxes, a conventional capture-gating technique is used for measuring neutron energies above 20 MeV andmore » a novel multiplicity technique is used for measuring neutron energies above 100 MeV. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. To calibrate and characterize the position dependent response of the spectrometer, a Monte Carlo model was developed and used in conjunction with experimental data from gamma ray sources. Multiplicity event identification algorithms were developed and used with a Cf-252 neutron multiplicity source to validate the Monte Carlo model Gd concentration and secondary neutron capture efficiency. The validated Monte Carlo model was used to predict an effective area for the multiplicity and capture gating analyses. For incident neutron energies between 100 MeV and 1000 MeV with an isotropic angular distribution, the multiplicity analysis predicted an effective area of 500 cm 2 rising to 5000 cm 2. For neutron energies above 20 MeV, the capture-gating analysis predicted an effective area between 1800 cm 2 and 2500 cm 2. As a result, the multiplicity mode was found to be sensitive to the incident neutron angular distribution.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roecker, C.; Bernstein, A.; Bowden, N. S.

A transportable fast neutron detection system has been designed and constructed for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The transportability of the spectrometer reduces the detector-related systematic bias between different neutron spectra and flux measurements, which allows for the comparison of measurements above or below ground. The spectrometer will measure neutron fluxes that are of prohibitively low intensity compared to the site-specific background rates targeted by other transportable fast neutron detection systems. To measure low intensity high-energy neutron fluxes, a conventional capture-gating technique is used for measuring neutron energies above 20 MeV andmore » a novel multiplicity technique is used for measuring neutron energies above 100 MeV. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. To calibrate and characterize the position dependent response of the spectrometer, a Monte Carlo model was developed and used in conjunction with experimental data from gamma ray sources. Multiplicity event identification algorithms were developed and used with a Cf-252 neutron multiplicity source to validate the Monte Carlo model Gd concentration and secondary neutron capture efficiency. The validated Monte Carlo model was used to predict an effective area for the multiplicity and capture gating analyses. For incident neutron energies between 100 MeV and 1000 MeV with an isotropic angular distribution, the multiplicity analysis predicted an effective area of 500 cm 2 rising to 5000 cm 2. For neutron energies above 20 MeV, the capture-gating analysis predicted an effective area between 1800 cm 2 and 2500 cm 2. As a result, the multiplicity mode was found to be sensitive to the incident neutron angular distribution.« less

PVT-NG sensor final report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchell, Dean James; Brusseau, Charles A.

2012-01-01

This document is a final report for the polyvinyl toluene (PVT) neutron-gamma (PVT-NG) project, which was sponsored by the Domestic Nuclear Detection Office (DNDO). The PVT-NG sensor uses PVT detectors for both gamma and neutron detection. The sensor exhibits excellent spectral resolution and gain stabilization, which are features that are beneficial for detection of both gamma-ray and neutron sources. In fact, the ability to perform isotope identification based on spectra that were measured by the PVT-NG sensor was demonstrated. As described in a previous report, the neutron sensitivity of the first version of the prototype was about 25% less thanmore » the DNDO requirement of 2.5 cps/ng for bare Cf-252. This document describes design modifications that were expected to improve the neutron sensitivity by about 50% relative to the PVT-NG prototype. However, the project was terminated before execution of the design modifications after portal vendors demonstrated other technologies that enable neutron detection without the use of He-3. Nevertheless, the PVT-NG sensor development demonstrated several performance goals that may be useful in future portal designs.« less

Non destructive multi elemental analysis using prompt gamma neutron activation analysis techniques: Preliminary results for concrete sample

NASA Astrophysics Data System (ADS)

Dahing, Lahasen@Normanshah; Yahya, Redzuan; Yahya, Roslan; Hassan, Hearie

2014-09-01

In this study, principle of prompt gamma neutron activation analysis has been used as a technique to determine the elements in the sample. The system consists of collimated isotopic neutron source, Cf-252 with HPGe detector and Multichannel Analysis (MCA). Concrete with size of 10×10×10 cm3 and 15×15×15 cm3 were analysed as sample. When neutrons enter and interact with elements in the concrete, the neutron capture reaction will occur and produce characteristic prompt gamma ray of the elements. The preliminary result of this study demonstrate the major element in the concrete was determined such as Si, Mg, Ca, Al, Fe and H as well as others element, such as Cl by analysis the gamma ray lines respectively. The results obtained were compared with NAA and XRF techniques as a part of reference and validation. The potential and the capability of neutron induced prompt gamma as tool for multi elemental analysis qualitatively to identify the elements present in the concrete sample discussed.

Segmented Ge detector rejection of internal beta activity produced by neutron irradiation

NASA Technical Reports Server (NTRS)

Varnell, L. S.; Callas, J. L.; Mahoney, W. A.; Pehl, R. H.; Landis, D. A.

1991-01-01

Future Ge spectrometers flown in space to observe cosmic gamma-ray sources will incorporate segmented detectors to reduce the background from radioactivity produced by energetic particle reactions. To demonstrate the effectiveness of a segmented Ge detector in rejecting background events due to the beta decay of internal radioactivity, a laboratory experiment has been carried out in which radioactivity was produced in the detector by neutron irradiation. A Cf-252 source of neutrons was used to produce, by neutron capture on Ge-74 (36.5 percent of natural Ge) in the detector itself, Ge-75 (t sub 1/2 = 82.78 min), which decays by beta emission with a maximum electron kinetic energy of 1188 keV. By requiring that an ionizing event deposit energy in two or more of the five segments of the detector, each about 1-cm thick, the beta particles, which have a range of about 1-mm, are rejected, while most external gamma rays incident on the detector are counted. Analysis of this experiment indicates that over 85 percent of the beta events from the decay of Ge-75 are rejected, which is in good agreement with Monte Carlo calculations.

Investigation of Workplace-like Calibration Fields via a Deuterium-Tritium (D-T) Neutron Generator.

PubMed

Mozhayev, Andrey V; Piper, Roman K; Rathbone, Bruce A; McDonald, Joseph C

2017-04-01

Radiation survey meters and personal dosimeters are typically calibrated in reference neutron fields based on conventional radionuclide sources, such as americium-beryllium (Am-Be) or californium-252 (Cf), either unmodified or heavy-water moderated. However, these calibration neutron fields differ significantly from the workplace fields in which most of these survey meters and dosimeters are being used. Although some detectors are designed to yield an approximately dose-equivalent response over a particular neutron energy range, the response of other detectors is highly dependent upon neutron energy. This, in turn, can result in significant over- or underestimation of the intensity of neutron radiation and/or personal dose equivalent determined in the work environment. The use of simulated workplace neutron calibration fields that more closely match those present at the workplace could improve the accuracy of worker, and workplace, neutron dose assessment. This work provides an overview of the neutron fields found around nuclear power reactors and interim spent fuel storage installations based on available data. The feasibility of producing workplace-like calibration fields in an existing calibration facility has been investigated via Monte Carlo simulations. Several moderating assembly configurations, paired with a neutron generator using the deuterium tritium (D-T) fusion reaction, were explored.

The SPIDER fission fragment spectrometer for fission product yield measurements

DOE PAGES

Meierbachtol, K.; Tovesson, F.; Shields, D.; ...

2015-04-01

We developed the SPectrometer for Ion DEtermination in fission Research (SPIDER) for measuring mass yield distributions of fission products from spontaneous and neutron-induced fission. The 2E–2v method of measuring the kinetic energy (E) and velocity (v) of both outgoing fission products has been utilized, with the goal of measuring the mass of the fission products with an average resolution of 1 atomic mass unit (amu). Moreover, the SPIDER instrument, consisting of detector components for time-of-flight, trajectory, and energy measurements, has been assembled and tested using 229Th and 252Cf radioactive decay sources. For commissioning, the fully assembled system measured fission productsmore » from spontaneous fission of 252Cf. Individual measurement resolutions were met for time-of-flight (250 ps FWHM), spacial resolution (2 mm FHWM), and energy (92 keV FWHM for 8.376 MeV). Finally, these mass yield results measured from 252Cf spontaneous fission products are reported from an E–v measurement.« less

Study of the Mo-Ba partition in 252Cf spontaneous fission

NASA Astrophysics Data System (ADS)

Biswas, D. C.; Choudhury, R. K.; Cinausero, M.; Fornal, B.; Shetty, D. V.; Viesti, G.; Fabris, D.; Fioretto, E.; Lunardon, M.; Nebbia, G.; Prete, G.; Bazzacco, D.; DePoli, M.; Napoli, D. R.; Ur, C. A.; Vedovato, G.

Measurements of fission fragment yields and neutron multiplicities have been carried out for the Mo-Ba fragment pairs in the spontaneous fission of 252Cf, using the γ-ray spectroscopy technique to analyze γ-γ-γ coincidence data. Prompt γ -ray multiplicities were also measured as a function of the number of neutrons emitted in the fission process leading to the Mo-Ba partition. We do not observe the enhancement in the yields of events with high neutron emission multiplicity (νn > 7) that has been associated to a second fission mode leading to the production of hyperdeformed Ba fragments, as reported in some earlier studies. The average γ-ray multiplicity is found to be rather weakly dependent on the number of neutrons emitted in the fission process.

Source detection at 100 meter standoff with a time-encoded imaging system

NASA Astrophysics Data System (ADS)

Brennan, J.; Brubaker, E.; Gerling, M.; Marleau, P.; Monterial, M.; Nowack, A.; Schuster, P.; Sturm, B.; Sweany, M.

2018-01-01

We present the design, characterization, and testing of a laboratory prototype radiological search and localization system. The system, based on time-encoded imaging, uses the attenuation signature of neutrons in time, induced by the geometrical layout and motion of the system. We have demonstrated the ability to detect a ∼ 1mCi252Cf radiological source at 100m standoff with 90% detection efficiency and 10% false positives against background in 12min. This same detection efficiency is met at 15s for a 40m standoff, and 1 . 2s for a 20m standoff.

FIELD CALIBRATION OF A TLD ALBEDO DOSEMETER IN THE HIGH-ENERGY NEUTRON FIELD OF CERF.

PubMed

Haninger, T; Kleinau, P; Haninger, S

2017-04-28

The new albedo dosemeter-type AWST-TL-GD 04 has been calibrated in the CERF neutron field (Cern-EU high-energy Reference Field). This type of albedo dosemeter is based on thermoluminescent detectors (TLDs) and used by the individual monitoring service of the Helmholtz Zentrum München (AWST) since 2015 for monitoring persons, who are exposed occupationally against photon and neutron radiation. The motivation for this experiment was to gain a field specific neutron correction factor Nn for workplaces at high-energy particle accelerators. Nn is a dimensionless factor relative to a basic detector calibration with 137Cs and is used to calculate the personal neutron dose in terms of Hp(10) from the neutron albedo signal. The results show that the sensitivity of the albedo dosemeter for this specific neutron field is not significantly lower as for fast neutrons of a radionuclide source like 252Cf. The neutron correction factor varies between 0.73 and 1.16 with a midrange value of 0.94. The albedo dosemeter is therefore appropriate to monitor persons, which are exposed at high-energy particle accelerators. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Technical Letter Report on the Cracking of Irradiated Cast Stainless Steels with Low Ferrite Content

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Y.; Alexandreanu, B.; Natesan, K.

2014-11-01

Crack growth rate and fracture toughness J-R curve tests were performed on CF-3 and CF-8 cast austenite stainless steels (CASS) with 13-14% of ferrite. The tests were conducted at ~320°C in either high-purity water with low dissolved oxygen or in simulated PWR water. The cyclic crack growth rates of CF-8 were higher than that of CF-3, and the differences between the aged and unaged specimens were small. No elevated SCC susceptibility was observed among these samples, and the SCC CGRs of these materials were comparable to those of CASS alloys with >23% ferrite. The fracture toughness values of unirradiated CF-3more » were similar between unaged and aged specimens, and neutron irradiation decreased the fracture toughness significantly. The fracture toughness of CF-8 was reduced after thermal aging, and declined further after irradiation. It appears that while lowering ferrite content may help reduce the tendency of thermal aging embrittlement, it is not very effective to mitigate irradiation-induced embrittlement. Under a combined condition of thermal aging and irradiation, neutron irradiation plays a dominant role in causing embrittlement in CASS alloys.« less

Characterization of a tin-loaded liquid scintillator for gamma spectroscopy and neutron detection

NASA Astrophysics Data System (ADS)

Wen, Xianfei; Harvey, Taylor; Weinmann-Smith, Robert; Walker, James; Noh, Young; Farley, Richard; Enqvist, Andreas

2018-07-01

A tin-loaded liquid scintillator has been developed for gamma spectroscopy and neutron detection. The scintillator was characterized in regard to energy resolution, pulse shape discrimination, neutron light output function, and timing resolution. The loading of tin into scintillators with low effective atomic number was demonstrated to provide photopeaks with acceptable energy resolution. The scintillator was shown to have reasonable neutron/gamma discrimination capability based on the charge comparison method. The effect on the discrimination quality of the total charge integration time and the initial delay time for tail charge integration was studied. To obtain the neutron light output function, the time-of-flight technique was utilized with a 252Cf source. The light output function was validated with the MCNPX-PoliMi code by comparing the measured and simulated pule height spectra. The timing resolution of the developed scintillator was also evaluated. The tin-loading was found to have negligible impact on the scintillation decay times. However, a relatively large degradation of timing resolution was observed due to the reduced light yield.

Detection of Landmines by Neutron Backscattering: Effects of Soil Moisture on the Detection System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baysoy, D. Y.; Subasi, M.

2010-01-21

Detection of buried land mines by using neutron backscattering technique (NBS) is a well established method. It depends on detecting a hydrogen anomaly in dry soil. Since a landmine and its plastic casing contain much more hydrogen atoms than the dry soil, this anomaly can be detected by observing a rise in the number of neutrons moderated to thermal or epithermal energy. But, the presence of moisture in the soil limits the effectiveness of the measurements. In this work, a landmine detection system using the NBS technique was designed. A series of Monte Carlo calculations was carried out to determinemore » the limits of the system due to the moisture content of the soil. In the simulations, an isotropic fast neutron source ({sup 252}Cf, 100 mug) and a neutron detection system which consists of five {sup 3}He detectors were used in a practicable geometry. In order to see the effects of soil moisture on the efficiency of the detection system, soils with different water contents were tested.« less

Correlated fission data measurements with DANCE and NEUANCE

NASA Astrophysics Data System (ADS)

Jandel, M.; Baramsai, B.; Bredeweg, T. A.; Couture, A.; Favalli, A.; Hayes, A. C.; Ianakiev, K. D.; Iliev, M. L.; Kawano, T.; Mosby, S.; Rusev, G.; Stetcu, I.; Talou, P.; Ullmann, J. L.; Vieira, D. J.; Walker, C. L.; Wilhelmy, J. B.

2018-02-01

To enhance the capabilities of the DANCE array, a new detector array NEUANCE was developed to enable simultaneous measurements of prompt fission neutrons and γ rays. NEUANCE was designed and constructed using 21 stilbene organic scintillator crystals. It was installed in the central cavity of the DANCE array. Signals from the 160 BaF2 detectors of DANCE and the 21 detectors of NEUANCE were merged into a newly designed high-density high-throughput data acquisition system. The excellent pulse shape discrimination properties of stilbene enabled detection of neutrons with energy thresholds as low as 30-40 keVee. A fission reaction tagging method was developed using a NEUANCE γ-ray or neutron signal. The probability of detecting a neutron from the spontaneous fission of 252Cf using NEUANCE is ∼47%. New correlated data for prompt fission neutrons and prompt fission γ rays were obtained for 252Cf using this high detection efficiency experimental setup. Average properties of prompt fission neutron emission as a function of prompt fission γ-ray quantities were also obtained, suggesting that neutron and γ-ray emission in fission are correlated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jandel, Marian; Baramsai, Baramsai; Bredeweg, Todd Allen

To enhance the capabilities of the DANCE array, a new detector array NEUANCE was developed to enable simultaneous measurements of prompt fission neutrons and γ rays. NEUANCE was designed and constructed using 21 stilbene organic scintillator crystals. It was installed in the central cavity of the DANCE array. Signals from the 160 BaF 2 detectors of DANCE and the 21 detectors of NEUANCE were merged into a newly designed high-density high-throughput data acquisition system. The excellent pulse shape discrimination properties of stilbene enabled detection of neutrons with energy thresholds as low as 30–40 keVee. A fission reaction tagging method wasmore » developed using a NEUANCE γ-ray or neutron signal. The probability of detecting a neutron from the spontaneous fission of 252Cf using NEUANCE is 47%. New correlated data for prompt fission neutrons and prompt fission rays were obtained for 252Cf using this high detection efficiency experimental setup. In conclusion, average properties of prompt fission neutron emission as a function of prompt fission γ-ray quantities were also obtained, suggesting that neutron and γ-ray emission in fission are correlated.« less

IEC-Based Neutron Generator for Security Inspection System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Linchun; Miley, George H.

2002-07-01

Large nuclear reactors are widely employed for electricity power generation, but small nuclear radiation sources can also be used for a variety of industrial/government applications. In this paper we will discuss the use of a small neutron source based on Inertial Electrostatic Confinement (IEC) of accelerated deuterium ions. There is an urgent need of highly effective detection systems for explosives, especially in airports. While current airport inspection systems are strongly based on X-ray technique, neutron activation including Thermal Neutron Analysis (TNA) and Fast Neutron Analysis (FNA) is powerful in detecting certain types of explosives in luggage and in cargoes. Basicmore » elements present in the explosives can be measured through the (n, n'?) reaction initiated by fast neutrons. Combined with a time-of-flight technique, a complete imaging of key elements, hence of the explosive materials, is obtained. Among the various neutron source generators, the IEC is an ideal candidate to meet the neutron activation analysis requirements. Compared with other accelerators and radioisotopes such as {sup 252}Cf, the IEC is simpler, can be switched on or off, and can reliably produce neutrons with minimum maintenance. Theoretical and experimental studies of a spherical IEC have been conducted at the University of Illinois. In a spherical IEC device, 2.54-MeV neutrons of {approx}10{sup 8} n/s via DD reactions over recent years or 14-MeV neutrons of {approx}2x10{sup 10} n/s via DT reactions can be obtained using an ion gun injection technique. The possibility of the cylindrical IEC in pulsed operation mode combining with pulsed FNA method would also be discussed. In this paper we examine the possibility of using an alternative cylindrical IEC configuration. Such a device was studied earlier at the University of Illinois and it provides a very convenient geometry for security inspection. However, to calculate the neutron yield precisely with this configuration, an understanding of the potential wall trapping and acceleration of ions is needed. The theory engaged is an extension of original analytic study by R.L. Hirsh on the potential well structure in a spherical IEC device, i.e. roughly a 'line' source of neutrons from a cylindrical IEC is a 'point' source from the spherical geometry. Thus our present study focuses on the cylindrical IEC for its convenient application in an FNA detecting system. The conceptual design and physics of ion trapping and re-circulation in a cylindrical IEC intended for neutron-based inspection system will be presented. (authors)« less

CF NEUTRON TIME OF FLIGHT TRANSMISSION FOR MATERIAL IDENTIFICATION FOR WEAPONS TRAINERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mihalczo, John T; Valentine, Timothy E; Blakeman, Edward D

2011-01-01

The neutron transmission, elastic scattering, and non elastic reactions can be used to distinguish various isotopes. Neutron transmission as a function of energy can be used in some cases to identify materials in unknown objects. A time tagged californium source that provides a fission spectrum of neutrons is a useful source for neutron time-of-flight (TOF) transmission measurements. Many nuclear weapons trainer units for a particular weapons system (no fissile, but of same weight and center of gravity) in shipping containers were returned to the National Nuclear Security Administration Y-12 National Security Complex in the mid 1990s. Nuclear Materials Identification Systemmore » (NMIS) measurements with a time tagged californium neutron source were used to verify that these trainers did not contain fissile material. In these blind tests, the time distributions of neutrons through the containers were measured as a function of position to locate the approximate center of the trainer in the container. Measurements were also performed with an empty container. TOF template matching measurements were then performed at this location for a large number of units. In these measurements, the californium source was located on one end of the container and a proton recoil scintillator was located on the other end. The variations in the TOF transmission for times corresponding to 1 to 5 MeV were significantly larger than statistical. Further examination of the time distribution or the energy dependence revealed that these variations corresponded to the variations in the neutron cross section of aluminum averaged over the energy resolution of the californium TOF measurement with a flight path of about 90 cm. Measurements using different thicknesses of aluminum were also performed with the source and detector separated the same distance as for the trainer measurements. These comparison measurements confirmed that the material in the trainers was aluminum, and the total thickness of aluminum through the trainers was determined. This is an example of how californium transmission TOF measurements can be used to identify materials.« less

Neutron Detection with Centrifugally-Tensioned Metastable Fluid Detectors (CMTFD)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Y.; Smagacz, P.; Lapinskas, J.

2006-07-01

Tensioned metastable liquid states at room temperature were utilized to display sensitivity to impinging nuclear radiation, that manifests itself via audio-visual signals that one can see and hear. A centrifugally-tensioned metastable fluid detector (CTMFD), a diamond shaped spinning device rotating about its axis, was used to induce tension states, i.e. negative (sub-vacuum) pressures in liquids. In this device, radiation induced cavitation is audible due to liquid fracture and is visible from formed bubbles, so called hearing and seeing radiation. This type of detectors is selectively insensitive to Gamma rays and associated indication devices could be extremely simple, reliable and inexpensive.more » Furthermore, any liquids with large neutron interaction cross sections could be good candidates. Two liquids, isopentane and methanol, were tested with three neutron sources of Cf-252, PuBe and Pulsed Neutron Generator (PNG) under various configurations of neutron spectra and fluxes. The neutron count rates were measured using a liquid scintillation detector. The CTMFD was operated at preset values of rotating frequency and a response time was recorded when a cavitation occurred. Other parameters, including ambient temperature, ramp rate, delay time between two consecutive cavitations, were kept constant. The distance between the menisci of the liquid in the CTMFD was measured before and after each experiment. In general, the response of liquid molecules in a CTMFD varies with the neutron spectrum and flux. The response time follows an exponential trend with negative pressures for a given neutron count rate and spectra conditions. Isopentane was found to exhibit lower tension thresholds than methanol. On the other hand, methanol offered a larger tension metastability state variation for the various types of neutron sources, indicating the potential for offering significantly better energy resolution abilities for spectroscopic applications. (authors)« less

Source detection at 100 meter standoff with a time-encoded imaging system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brennan, J.; Brubaker, E.; Gerling, M.

Here, we present the design, characterization, and testing of a laboratory prototype radiological search and localization system. The system, based on time-encoded imaging, uses the attenuation signature of neutrons in time, induced by the geometrical layout and motion of the system. We have demonstrated the ability to detect a ~1 mCi 252 Cf radiological source at 100 m standoff with 90% detection efficiency and 10% false positives against background in 12 min. As a result, this same detection efficiency is met at 15 s for a 40 m standoff, and 1.2 s for a 20 m standoff.

Source detection at 100 meter standoff with a time-encoded imaging system

DOE PAGES

Brennan, J.; Brubaker, E.; Gerling, M.; ...

2017-09-28

Here, we present the design, characterization, and testing of a laboratory prototype radiological search and localization system. The system, based on time-encoded imaging, uses the attenuation signature of neutrons in time, induced by the geometrical layout and motion of the system. We have demonstrated the ability to detect a ~1 mCi 252 Cf radiological source at 100 m standoff with 90% detection efficiency and 10% false positives against background in 12 min. As a result, this same detection efficiency is met at 15 s for a 40 m standoff, and 1.2 s for a 20 m standoff.

Direction sensitive neutron detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahlen, Steven; Fisher, Peter; Dujmic, Denis

2017-01-31

A neutron detector includes a pressure vessel, an electrically conductive field cage assembly within the pressure vessel and an imaging subsystem. A pressurized gas mixture of CF.sub.4, .sup.3He and .sup.4He at respective partial pressures is used. The field cage establishes a relatively large drift region of low field strength, in which ionization electrons generated by neutron-He interactions are directed toward a substantially smaller amplification region of substantially higher field strength in which the ionization electrons undergo avalanche multiplication resulting in scintillation of the CF.sub.4 along scintillation tracks. The imaging system generates two-dimensional images of the scintillation patterns and employs track-findingmore » to identify tracks and deduce the rate and direction of incident neutrons. One or more photo-multiplier tubes record the time-profile of the scintillation tracks permitting the determination of the third coordinate.« less

ALGORITHM BASED ON ARTIFICIAL BEE COLONY FOR UNFOLDING OF NEUTRON SPECTRA OBTAINED WITH BONNER SPHERES.

PubMed

Silva, Everton R; Freitas, Bruno M; Santos, Denison S; Maurício, Cláudia L P

2018-04-13

Occupational neutron fields usually have energies from the thermal range to some MeV and the characterization of the spectra is essential for estimation of the radioprotection quantities. Thus, the spectrum must be unfolded based on a limited number of measurements. This study implemented an algorithm based on the bee colonies behavior, named Artificial Bee Colony (ABC), where the intelligent behavior of the bees in search of food is reproduced to perform the unfolding of neutron spectra. The experimental measurements used Bonner spheres and 6LiI (Eu) detector, with irradiations using a thermal neutron flux and three reference fields: 241Am-Be, 252Cf and 252Cf (D2O). The ABC obtained good estimation of the expected spectrum even without previous information and its results were closer to expected spectra than those obtained by the SPUNIT algorithm.

Experimental characterization of the AFIT neutron facility. Master's thesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lessard, O.J.

1993-09-01

AFIT's Neutron Facility was characterized for room-return neutrons using a (252)Cf source and a Bonner sphere spectrometer with three experimental models, the shadow shield, the Eisenhauer, Schwartz, and Johnson (ESJ), and the polynomial models. The free-field fluences at one meter from the ESJ and polynomial models were compared to the equivalent value from the accepted experimental shadow shield model to determine the suitability of the models in the AFIT facility. The polynomial model behaved erratically, as expected, while the ESJ model compared to within 4.8% of the shadow shield model results for the four Bonner sphere calibration. The ratio ofmore » total fluence to free-field fluence at one meter for the ESJ model was then compared to the equivalent ratio obtained by a Monte Cario Neutron-Photon transport code (MCNP), an accepted computational model. The ESJ model compared to within 6.2% of the MCNP results. AFIT's fluence ratios were compared to equivalent ratios reported by three other neutron facilities which verified that AFIT's results fit previously published trends based on room volumes. The ESJ model appeared adequate for health physics applications and was chosen was chosen for calibration of the AFIT facility. Neutron Detector, Bonner Sphere, Neutron Dosimetry, Room Characterization.« less

Benchmarking the MCNP code for Monte Carlo modelling of an in vivo neutron activation analysis system.

PubMed

Natto, S A; Lewis, D G; Ryde, S J

1998-01-01

The Monte Carlo computer code MCNP (version 4A) has been used to develop a personal computer-based model of the Swansea in vivo neutron activation analysis (IVNAA) system. The model included specification of the neutron source (252Cf), collimators, reflectors and shielding. The MCNP model was 'benchmarked' against fast neutron and thermal neutron fluence data obtained experimentally from the IVNAA system. The Swansea system allows two irradiation geometries using 'short' and 'long' collimators, which provide alternative dose rates for IVNAA. The data presented here relate to the short collimator, although results of similar accuracy were obtained using the long collimator. The fast neutron fluence was measured in air at a series of depths inside the collimator. The measurements agreed with the MCNP simulation within the statistical uncertainty (5-10%) of the calculations. The thermal neutron fluence was measured and calculated inside the cuboidal water phantom. The depth of maximum thermal fluence was 3.2 cm (measured) and 3.0 cm (calculated). The width of the 50% thermal fluence level across the phantom at its mid-depth was found to be the same by both MCNP and experiment. This benchmarking exercise has given us a high degree of confidence in MCNP as a tool for the design of IVNAA systems.

Insulating epoxy/barite and polyester/barite composites for radiation attenuation.

PubMed

El-Sarraf, M A; El-Sayed Abdo, A

2013-09-01

A trial has been made to create insulating Epoxy/Barite (EP/Brt) (ρ=2.85 g cm(-3)) and Crosslinked Unsaturated Polyester/Barite (CUP/Brt) (ρ=3.25 g cm(-3)) composites with radiation attenuation and shielding capabilities. Experimental work regarding mechanical and physical properties was performed to study the composites integrity for practical applications. The properties were found to be reasonable. Radiation attenuation properties have been carried out using emitted collimated beam from a fission (252)Cf (100 µg) neutron source, and the neutron-gamma spectrometer with stilbene scintillator. The pulse shape discriminating (P.S.D) technique based on the zero cross-over method was used to discriminate between neutron and gamma-ray pulses. Thermal neutron fluxes, measured using the BF3 detector and thermal neutron detection system, were used to plot the attenuation relations. The fast neutron macroscopic effective removal cross-section ΣR, gamma ray total attenuation coefficient µ and thermal neutron macroscopic cross-section Σ have been evaluated. Theoretical calculations have been achieved using MCNP-4C2 code to calculate ΣR, µ and Σ. Also, MERCSF-N program was used to calculate macroscopic effective removal cross-section ΣR. Measured and calculated results have been compared and were found to be in reasonable agreement. Copyright © 2013 Elsevier Ltd. All rights reserved.

Influence of magnetite, ilmenite and boron carbide on radiation attenuation of polyester composites

NASA Astrophysics Data System (ADS)

El-Sarraf, M. A.; El-Sayed Abdo, A.

2013-07-01

This work is concerned with studying polyester/ magnetite CUP/Mag (ρ=2.75 g cm-3) and polyester/ ilmenite CUP/Ilm (ρ=2.7 g cm-3) composites for shielding of medical facilities, laboratory hot cells and for various purposes. Mechanical and physical properties such as compressive, flexural and impact strengths, as well as, a.c. electrical conductivity, specific heat, water absorption and porosity have been performed to evaluate the composite capabilities for radiation shielding. A collimated beam from fission 252Cf (100 µg) neutron source and neutron-gamma spectrometer with stilbene scintillator based on the zero cross over method and pulse shape discrimination (P.S.D.) technique have been used to measure neutron and gamma ray spectra. Fluxes of thermal neutrons have been measured using the BF3 detector and thermal neutron detection system. The attenuation parameters, namely macroscopic effective removal cross-section ΣR, total attenuation coefficient µ and macroscopic cross-section Σ of fast neutrons, gamma rays and thermal neutrons respectively have been evaluated. Theoretical calculations using MCNP-4C2 code was used to calculate ΣR,μ and Σ. Also, MERCSF-N program was used to calculate macroscopic effective removal cross-section ΣR. Measured and calculated results were compared and reasonable agreement was found.

Correlated fission data measurements with DANCE and NEUANCE

DOE PAGES

Jandel, Marian; Baramsai, Baramsai; Bredeweg, Todd Allen; ...

2017-11-16

To enhance the capabilities of the DANCE array, a new detector array NEUANCE was developed to enable simultaneous measurements of prompt fission neutrons and γ rays. NEUANCE was designed and constructed using 21 stilbene organic scintillator crystals. It was installed in the central cavity of the DANCE array. Signals from the 160 BaF 2 detectors of DANCE and the 21 detectors of NEUANCE were merged into a newly designed high-density high-throughput data acquisition system. The excellent pulse shape discrimination properties of stilbene enabled detection of neutrons with energy thresholds as low as 30–40 keVee. A fission reaction tagging method wasmore » developed using a NEUANCE γ-ray or neutron signal. The probability of detecting a neutron from the spontaneous fission of 252Cf using NEUANCE is 47%. New correlated data for prompt fission neutrons and prompt fission rays were obtained for 252Cf using this high detection efficiency experimental setup. In conclusion, average properties of prompt fission neutron emission as a function of prompt fission γ-ray quantities were also obtained, suggesting that neutron and γ-ray emission in fission are correlated.« less

Characterization of Deuterated-xylene Scintillator as a Neutron Spectrometer

DOE PAGES

Di Fulvio, Angela; Becchetti, F. D.; Raymond, R. S.; ...

2016-11-16

We have experimentally characterized the neutron light output response functions of a deuterated-xylene scintillator for neutron energies lower than 10 MeV. We then used the response matrix to unfold the energy distribution of neutrons produced via several reactions, i.e. spontaneous fission, d(d,n)3He, 27Al(d,n)28Si, and 9Be(alpha,n)12C. Organic scintillators based on deuterated compounds show a fast response and good gamma-neutron discrimination capability, similar to proton-based scintillators. Deuterated scintillators can also effectively provide neutron spectra by unfolding measured data with the detector response matrix, without the need of time-of-flight. Deuteron recoils, produced by elastic collisions between deuterium and impinging neutrons, are preferentially forward-scattered.more » This non-isotropic reaction results in distinct peaks in the response functions to monoenergetic neutrons. In this work, we evaluated a custom-fabricated 7.62 cm x 7.62 cm deuterated-xylene (EJ301D) liquid scintillator. This liquid has a low volatility and higher flash point, compared to benzene-based deuterated detectors, e.g. EJ315 and NE230. We measured the EJ301D detector neutron response matrix (up to 6 MeV neutron energy) using an intense Cf252 source and the time-of-flight technique. The number of response functions obtained using our method is only limited by counting statistics and by the experimentally achievable energy resolution. Multi-channel unfolding was performed successfully for neutron spectra with different energy spectra.« less

Development of a lithium fluoride zinc sulfide based neutron multiplicity counter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cowles, Christian; Behling, Spencer; Baldez, Phoenix

Past 3He shortages led to investigations into replacement options for neutron detectors in systems that previously used 3He-based technologies. The goal of this research was to investigate the feasibility of a full-scale lithium fluoride with silver activated zinc sulfide (LiF/ZnS) based neutron multiplicity counter. The LiF/ZnS based neutron multiplicity counter (LiNMC) was developed based on an iterative process between modeling and experimental measurements. Each active region of the LiNMC contains five sheets of LiF/ZnS sandwiched between six sheets of wavelength shifting plastic to form neutron detection stacks. The wavelength shifted scintillation light was collected by photomultiplier tubes located on eachmore » end of the stacks. Twelve such detector stacks were placed around a sample chamber in a square arrangement with lithiated high density polyethylene blocks in the corners to reflect high energy neutrons and capture low energy neutrons. Preliminary calibration with a 252Cf neutron source showed that the LiNMC was able to achieve 36% neutron detection efficiency (ε) and an 11.7 μs neutron die-away time (τ) for a doubles Figure-of-merit (ε2/ τ) of 109. This is the highest doubles Figure-of-merit performance measured to-date for a 3He-free neutron multiplicity counter system. By the end of this project, the LiNMC’s basic components were integrated into a single laboratory scale system capable of proof-of-concept measurements.« less

Phase 1 environmental report for the Advanced Neutron Source at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blasing, T.J.; Brown, R.A.; Cada, G.F.

1992-02-01

The US Department of Energy (DOE) has proposed the construction and operation of the Advanced Neutron Source (ANS), a 330-MW(f) reactor, at Oak Ridge National Laboratory (ORNL) to support neutron scattering and nuclear physics experiments. ANS would provide a steady-state source of neutrons that are thermalized to produce sources of hot, cold, and very coal neutrons. The use of these neutrons in ANS experiment facilities would be an essential component of national research efforts in basic materials science. Additionally, ANS capabilities would include production of transplutonium isotopes, irradiation of potential fusion and fission reactor materials, activation analysis, and production ofmore » medical and industrial isotopes such as {sup 252}Cf. Although ANS would not require licensing by the US Nuclear Regulatory Commission (NRC), DOE regards the design, construction, and operation of ANS as activities that would produce a licensable facility; that is, DOE is following the regulatory guidelines that NRC would apply if NRC were licensing the facility. Those guidelines include instructions for the preparation of an environmental report (ER), a compilation of available data and preliminary analyses regarding the environmental impacts of nuclear facility construction and operation. The ER, described and outlined in NRC Regulatory Guide 4.2, serves as a background document to facilitate the preparation of environmental impact statements (EISs). Using Regulatory Guide 4.2 as a model, this ANS ER provides analyses and information specific to the ANS site and area that can be adopted (and modified, if necessary) for the ANS EIS. The ER is being prepared in two phases. Phase 1 ER includes many of the data and analyses needed to prepare the EIS but does not include data or analyses of alternate sites or alternate technologies. Phase 2 ER will include the additional data and analyses stipulated by Regulatory Guide 4.2.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrews, Madison Theresa; Bates, Cameron Russell; Mckigney, Edward Allen

Here, this work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNPR output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed- field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNPR ®6, which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discriminationmore » plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.« less

Organic Scintillator Detector Response Simulations with DRiFT

DOE PAGES

Andrews, Madison Theresa; Bates, Cameron Russell; Mckigney, Edward Allen; ...

2016-06-11

Here, this work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNPR output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed- field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNPR ®6, which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discriminationmore » plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.« less

Organic scintillator detector response simulations with DRiFT

NASA Astrophysics Data System (ADS)

Andrews, M. T.; Bates, C. R.; McKigney, E. A.; Solomon, C. J.; Sood, A.

2016-09-01

This work presents the organic scintillation simulation capabilities of DRiFT, a post-processing Detector Response Function Toolkit for MCNP® output. DRiFT is used to create realistic scintillation detector response functions to incident neutron and gamma mixed-field radiation. As a post-processing tool, DRiFT leverages the extensively validated radiation transport capabilities of MCNP® 6 , which also provides the ability to simulate complex sources and geometries. DRiFT is designed to be flexible, it allows the user to specify scintillator material, PMT type, applied PMT voltage, and quenching data used in simulations. The toolkit's capabilities, which include the generation of pulse shape discrimination plots and full-energy detector spectra, are demonstrated in a comparison of measured and simulated neutron contributions from 252Cf and PuBe, and photon spectra from 22Na and 228Th sources. DRiFT reproduced energy resolution effects observed in EJ-301 measurements through the inclusion of scintillation yield variances, photon transport noise, and PMT photocathode and multiplication noise.

Keno-Nr a Monte Carlo Code Simulating the Californium -252-SOURCE-DRIVEN Noise Analysis Experimental Method for Determining Subcriticality

NASA Astrophysics Data System (ADS)

Ficaro, Edward Patrick

The ^{252}Cf -source-driven noise analysis (CSDNA) requires the measurement of the cross power spectral density (CPSD) G_ {23}(omega), between a pair of neutron detectors (subscripts 2 and 3) located in or near the fissile assembly, and the CPSDs, G_{12}( omega) and G_{13}( omega), between the neutron detectors and an ionization chamber 1 containing ^{252}Cf also located in or near the fissile assembly. The key advantage of this method is that the subcriticality of the assembly can be obtained from the ratio of spectral densities,{G _sp{12}{*}(omega)G_ {13}(omega)over G_{11 }(omega)G_{23}(omega) },using a point kinetic model formulation which is independent of the detector's properties and a reference measurement. The multigroup, Monte Carlo code, KENO-NR, was developed to eliminate the dependence of the measurement on the point kinetic formulation. This code utilizes time dependent, analog neutron tracking to simulate the experimental method, in addition to the underlying nuclear physics, as closely as possible. From a direct comparison of simulated and measured data, the calculational model and cross sections are validated for the calculation, and KENO-NR can then be rerun to provide a distributed source k_ {eff} calculation. Depending on the fissile assembly, a few hours to a couple of days of computation time are needed for a typical simulation executed on a desktop workstation. In this work, KENO-NR demonstrated the ability to accurately estimate the measured ratio of spectral densities from experiments using capture detectors performed on uranium metal cylinders, a cylindrical tank filled with aqueous uranyl nitrate, and arrays of safe storage bottles filled with uranyl nitrate. Good agreement was also seen between simulated and measured values of the prompt neutron decay constant from the fitted CPSDs. Poor agreement was seen between simulated and measured results using composite ^6Li-glass-plastic scintillators at large subcriticalities for the tank of uranyl nitrate. It is believed that the response of these detectors is not well known and is incorrectly modeled in KENO-NR. In addition to these tests, several benchmark calculations were also performed to provide insight into the properties of the point kinetic formulation.

Microchannel plate special nuclear materials sensor

NASA Astrophysics Data System (ADS)

Feller, W. B.; White, P. L.; White, P. B.; Siegmund, O. H. W.; Martin, A. P.; Vallerga, J. V.

2011-10-01

Nova Scientific Inc., is developing for the Domestic Nuclear Detection Office (DNDO SBIR #HSHQDC-08-C-00190), a solid-state, high-efficiency neutron detection alternative to 3He gas tubes, using neutron-sensitive microchannel plates (MCPs) containing 10B and/or Gd. This work directly supports DNDO development of technologies designed to detect and interdict nuclear weapons or illicit nuclear materials. Neutron-sensitized MCPs have been shown theoretically and more recently experimentally, to be capable of thermal neutron detection efficiencies equivalent to 3He gas tubes. Although typical solid-state neutron detectors typically have an intrinsic gamma sensitivity orders of magnitude higher than that of 3He gas detectors, we dramatically reduce gamma sensitivity by combining a novel electronic coincidence rejection scheme, employing a separate but enveloping gamma scintillator. This has already resulted in a measured gamma rejection ratio equal to a small 3He tube, without in principle sacrificing neutron detection efficiency. Ongoing improvements to the MCP performance as well as the coincidence counting geometry will be described. Repeated testing and validation with a 252Cf source has been underway throughout the Phase II SBIR program, with ongoing comparisons to a small commercial 3He gas tube. Finally, further component improvements and efforts toward integration maturity are underway, with the goal of establishing functional prototypes for SNM field testing.

Low cost mobile explosive/drug detection devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gozani, T.; Bendahan, J.

1999-06-10

Inspection technologies based on Thermal Neutron Analysis (TNA) and/or Fast Neutron Analysis (FNA) are the basis for relatively compact and low-cost, material-sensitive devices for a wide variety of inspection needs. The TNA allows the use of either isotropic neutron sources such as a {sup 252}Cf, or electronic neutron generators such as the d-T sealed neutron generator tubes. The latter could be used in a steady state mode or in slow (>{mu}s) pulsing mode, to separate the thermal neutron capture signatures following the pulse from the combination of the FNA plus TNA signatures during the pulse. Over the years, Ancore Corporationmore » has built and is continuing to develop a variety of inspection devices based on its TNA and FNA technologies: SPEDS--an explosive detection device for small parcels, portable electronics, briefcases and other similar carry-on items; MDS - a system for the detection or confirmation of buried mines; VEDS - a system for the detection of varied amounts of explosives and/or drugs concealed in passenger vehicles, pallets, lightly loaded trucks or containers, etc.; ACD - a device to clear alarms from a primary, non-specific explosive detection system for passenger luggage. The principle and performance of these devices will be shown and discussed.« less

Digital fast neutron radiography of steel reinforcing bar in concrete

NASA Astrophysics Data System (ADS)

Mitton, K.; Jones, A.; Joyce, M. J.

2014-12-01

Neutron imaging has previously been used in order to test for cracks, degradation and water content in concrete. However, these techniques often fall short of alternative non-destructive testing methods, such as γ-ray and X-ray imaging, particularly in terms of resolution. Further, thermal neutron techniques can be compromised by the significant expense associated with thermal neutron sources of sufficient intensity to yield satisfactory results that can often precipitate the need for a reactor. Such embodiments are clearly not portable in the context of the needs of field applications. This paper summarises the results of a study to investigate the potential for transmission radiography based on fast neutrons. The objective of this study was to determine whether the presence of heterogeneities in concrete, such as reinforcement structures, could be identified on the basis of variation in transmitted fast-neutron flux. Monte-Carlo simulations have been performed and the results from these are compared to those arising from practical tests using a 252Cf source. The experimental data have been acquired using a digital pulse-shape discrimination system that enables fast neutron transmission to be studied across an array of liquid scintillators placed in close proximity to samples under test, and read out in real time. Whilst this study does not yield sufficient spatial resolution, a comparison of overall flux ratios does provide a basis for the discrimination between samples with contrasting rebar content. This approach offers the potential for non-destructive testing that gives less dose, better transportability and better accessibility than competing approaches. It is also suitable for thick samples where γ-ray and X-ray methods can be limited.

Silicon Photomultipliers for Compact Neutron Scatter Cameras

NASA Astrophysics Data System (ADS)

Ruch, Marc L.

The ability to locate and identify special nuclear material (SNM) is critical for treaty verification and emergency response applications. SNM is used as the nuclear explosive in a nuclear weapon. This material emits neutrons, either spontaneously or when interrogated. The ability to form an image of the neutron source can be used for characterization and/or to confirm that the item is a weapon by determining whether its shape is consistent with that of a weapon. Additionally, treaty verification and emergency response applications might not be conducive to non-portable instruments. In future weapons treaties, for example, it is unlikely that host countries will make great efforts to facilitate large, bulky, and/or fragile inspection equipment. Furthermore, inspectors and especially emergency responders may need to access locations not easily approachable by vehicles. Therefore, there is a considerable need for a compact, human-portable neutron imaging system. Of the currently available neutron imaging technologies, only neutron scatter cameras (NSCs) can be made truly compact because aperture-based imagers, and time-encoded imagers, rely on large amounts of materials to modulate the neutron signal. NSCs, in contrast, can be made very small because most of the volume of the imager can be filled with active detector material. Also, unlike other neutron imaging technologies, NSCs have the inherent ability to act as neutron spectrometers which gives them an additional means of identifying a neutron source. Until recently, NSCs have relied on photomultiplier tubes (PMT) readouts, which are bulky and fragile, require high voltage, and are very sensitive to magnetic fields. Silicon photomultipliers (SiPMs) do not suffer from these drawbacks and are comparable to PMTs in many respects such as gain, and cost with better time resolution. Historically, SiPMs have been too noisy for these applications; however, recent advancements have greatly reduced this issue and they have now been shown to be viable alternatives to PMTs for neutron detection applications. In this thesis, the development of a handheld NSC based on SiPMs coupled to stilbene bars is presented. An algorithm for performing image reconstruction with this type of device is detailed. Prototype design optimization is achieved using a series of simulations and the construction of the optimized prototype is described. The device is calibrated through a series of collimated measurements, backscatter-gated measurements, and a time-of-flight measurement. Experimental imaging and spectroscopic results are presented for a measurement of a Cf-252 spontaneous fission source. Simulated detector response, based on measurements performed with components of the design, demonstrates that fission sources of different sizes would be distinguishable. Notably, a significant quantity of plutonium can be confidently distinguished from a point neutron source.

Optimization and Characterization of a Novel Self Powered Solid State Neutron Detector

NASA Astrophysics Data System (ADS)

Clinton, Justin

There is a strong interest in detecting both the diversion of special nuclear material (SNM) from legitimate, peaceful purposes and the transport of illicit SNM across domestic and international borders and ports. A simple solid-state detector employs a planar solar-cell type p-n junction and a thin conversion layer that converts incident neutrons into detectable charged particles, such as protons, alpha-particles, and heavier ions. Although simple planar devices can act as highly portable, low cost detectors, they have historically been limited to relatively low detection efficiencies; ˜10% and ˜0.2% for thermal and fast detectors, respectively. To increase intrinsic detection efficiency, the incorporation of 3D microstructures into p-i-n silicon devices was proposed. In this research, a combination of existing and new types of detector microstructures were investigated; Monte Carlo models, based on analytical calculations, were constructed and characterized using the GEANT4 simulation toolkit. The simulation output revealed that an array of etched hexagonal holes arranged in a honeycomb pattern and filled with either enriched (99% 10B) boron or parylene resulted in the highest intrinsic detection efficiencies of 48% and 0.88% for thermal and fast neutrons, respectively. The optimal parameters corresponding to each model were utilized as the basis for the fabrication of several prototype detectors. A calibrated 252Cf spontaneous fission source was utilized to generate fast neutrons, while thermal neutrons were created by placing the 252Cf in an HDPE housing designed and optimized using the MCNP simulation software. Upon construction, thermal neutron calibration was performed via activation analysis of gold foils and measurements from a 6Li loaded glass scintillator. Experimental testing of the prototype detectors resulted in maximum intrinsic efficiencies of 4.5 and 0.12% for the thermal and fast devices, respectively. The prototype thermal device was filled with natural (19% 10B) boron; scaling the response to 99% 10B enriched boron resulted in an intrinsic efficiency of 22.5%, one of the highest results in the literature. A comparison of simulated and experimental detector responses demonstrated a high degree of correlation, validating the conceptual models.

Feasibility study for wax deposition imaging in oil pipelines by PGNAA technique.

PubMed

Cheng, Can; Jia, Wenbao; Hei, Daqian; Wei, Zhiyong; Wang, Hongtao

2017-10-01

Wax deposition in pipelines is a crucial problem in the oil industry. A method based on the prompt gamma-ray neutron activation analysis technique was applied to reconstruct the image of wax deposition in oil pipelines. The 2.223MeV hydrogen capture gamma rays were used to reconstruct the wax deposition image. To validate the method, both MCNP simulation and experiments were performed for wax deposited with a maximum thickness of 20cm. The performance of the method was simulated using the MCNP code. The experiment was conducted with a 252 Cf neutron source and a LaBr 3 : Ce detector. A good correspondence between the simulations and the experiments was observed. The results obtained indicate that the present approach is efficient for wax deposition imaging in oil pipelines. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evaluation of a new neutron energy spectrum unfolding code based on an Adaptive Neuro-Fuzzy Inference System (ANFIS).

PubMed

Hosseini, Seyed Abolfazl; Esmaili Paeen Afrakoti, Iman

2018-01-17

The purpose of the present study was to reconstruct the energy spectrum of a poly-energetic neutron source using an algorithm developed based on an Adaptive Neuro-Fuzzy Inference System (ANFIS). ANFIS is a kind of artificial neural network based on the Takagi-Sugeno fuzzy inference system. The ANFIS algorithm uses the advantages of both fuzzy inference systems and artificial neural networks to improve the effectiveness of algorithms in various applications such as modeling, control and classification. The neutron pulse height distributions used as input data in the training procedure for the ANFIS algorithm were obtained from the simulations performed by MCNPX-ESUT computational code (MCNPX-Energy engineering of Sharif University of Technology). Taking into account the normalization condition of each energy spectrum, 4300 neutron energy spectra were generated randomly. (The value in each bin was generated randomly, and finally a normalization of each generated energy spectrum was performed). The randomly generated neutron energy spectra were considered as output data of the developed ANFIS computational code in the training step. To calculate the neutron energy spectrum using conventional methods, an inverse problem with an approximately singular response matrix (with the determinant of the matrix close to zero) should be solved. The solution of the inverse problem using the conventional methods unfold neutron energy spectrum with low accuracy. Application of the iterative algorithms in the solution of such a problem, or utilizing the intelligent algorithms (in which there is no need to solve the problem), is usually preferred for unfolding of the energy spectrum. Therefore, the main reason for development of intelligent algorithms like ANFIS for unfolding of neutron energy spectra is to avoid solving the inverse problem. In the present study, the unfolded neutron energy spectra of 252Cf and 241Am-9Be neutron sources using the developed computational code were found to have excellent agreement with the reference data. Also, the unfolded energy spectra of the neutron sources as obtained using ANFIS were more accurate than the results reported from calculations performed using artificial neural networks in previously published papers. © The Author(s) 2018. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Standardization of the neutron probe for the assessment of masonry deterioration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Livingston, R.A.

1992-01-01

The repair of the infrastructure will require nondestructive methods to assess the condition of existing buildings and other structures, many of which are constructed of masonry. One possible technology is the neutron probe, a prompt-gamma neutron activation (PGNA) technique that can perform non- destructive elemental analyses in the field. It is based on a very low intensity [sup 252]Cf neutron source and a high-purity germanium detector for the gamma rays emitted by neutron capture within the material. The thermal neutron capture cross sections for hydrogen and chlorine are very large, and in masonry, these elements are found primarily in moisturemore » and chlorides. These are major causes of deterioration in porous materials such as brick masonry. The moisture damages the material through expansive stresses during freeze-thaw cycles. Chlorides also generate expansive stresses through periodic cycles of dissolution and recrystallization in response to relative humidity cycles in the atmosphere. Similar problems also occur in reinforced concrete, where chlorides cause additional damage through corrosion of the reinforcing steel. The sensitivity of the neutron probe to hydrogen and chlorine thus means it can be used to map the distribution of these agents of deterioration. Preliminary field work at Colonial Williamsburg and Venice, Italy, showed that the technique could yield useful qualitative information. However, to be a quantitative method, the neutron probe had to be standardized in the laboratory on materials of known composition and specified moisture and chloride content.« less

Neutron spectra measurement and calculations using data libraries CIELO, JEFF-3.2 and ENDF/B-VII.1 in iron benchmark assemblies

NASA Astrophysics Data System (ADS)

Jansky, Bohumil; Rejchrt, Jiri; Novak, Evzen; Losa, Evzen; Blokhin, Anatoly I.; Mitenkova, Elena

2017-09-01

The leakage neutron spectra measurements have been done on benchmark spherical assemblies - iron spheres with diameter of 20, 30, 50 and 100 cm. The Cf-252 neutron source was placed into the centre of iron sphere. The proton recoil method was used for neutron spectra measurement using spherical hydrogen proportional counters with diameter of 4 cm and with pressure of 400 and 1000 kPa. The neutron energy range of spectrometer is from 0.1 to 1.3 MeV. This energy interval represents about 85 % of all leakage neutrons from Fe sphere of diameter 50 cm and about of 74% for Fe sphere of diameter 100 cm. The adequate MCNP neutron spectra calculations based on data libraries CIELO, JEFF-3.2 and ENDF/B-VII.1 were done. Two calculations were done with CIELO library. The first one used data for all Fe-isotopes from CIELO and the second one (CIELO-56) used only Fe-56 data from CIELO and data for other Fe isotopes were from ENDF/B-VII.1. The energy structure used for calculations and measurements was 40 gpd (groups per decade) and 200 gpd. Structure 200 gpd represents lethargy step about of 1%. This relatively fine energy structure enables to analyze the Fe resonance neutron energy structure. The evaluated cross section data of Fe were validated on comparisons between the calculated and experimental spectra.

Measurement and Interpretation of DT Neutron Emission from Tftr.

NASA Astrophysics Data System (ADS)

McCauley, John Scott, Jr.

A fast-ion diffusion coefficient of 0.1 +/- 0.1 m^2s ^{-1} has been deduced from the triton burnup neutron emission profile measured by a collimated array of helium-4 spectrometers. The experiment was performed with high-power deuterium discharges produced by Princeton University's Tokamak Fusion Test Reactor (TFTR). The fast ions monitored were the 1.0 MeV tritons produced from the d(d,t)p triton burnup reaction. These tritons "burn up" with deuterons and emit a 14 MeV neutron by the d(t, alpha)n reaction. The measured radial profiles of DT emission were compared with the predictions of a computer transport code. The ratio of the measured-to -calculated DT yield is typically 70%. The measured DT profile width is typically 5 cm larger than predicted by the transport code. The radial 14 MeV neutron profile was measured by a radial array of helium-4 recoil neutron spectrometers installed in the TFTR Multichannel Neutron Collimator (MCNC). The spectrometers are capable of measuring the primary and secondary neutron fluxes from deuterium discharges. The response to 14 MeV neutrons of the array has been measured by cross calibrating with the MCNC ZnS detector array when the emission from TFTR is predominantly DT neutrons. The response was also checked by comparing a model of the recoil spectrum based on nuclear physics data to the observed spectrum from ^{252 }Cf, ^{238}Pu -Be, and DT neutron sources. Extensions of this diagnostic to deuterium-tritium plasma and the implications for fusion research are discussed.

Fast-neutron, coded-aperture imager

NASA Astrophysics Data System (ADS)

Woolf, Richard S.; Phlips, Bernard F.; Hutcheson, Anthony L.; Wulf, Eric A.

2015-06-01

This work discusses a large-scale, coded-aperture imager for fast neutrons, building off a proof-of concept instrument developed at the U.S. Naval Research Laboratory (NRL). The Space Science Division at the NRL has a heritage of developing large-scale, mobile systems, using coded-aperture imaging, for long-range γ-ray detection and localization. The fast-neutron, coded-aperture imaging instrument, designed for a mobile unit (20 ft. ISO container), consists of a 32-element array of 15 cm×15 cm×15 cm liquid scintillation detectors (EJ-309) mounted behind a 12×12 pseudorandom coded aperture. The elements of the aperture are composed of 15 cm×15 cm×10 cm blocks of high-density polyethylene (HDPE). The arrangement of the aperture elements produces a shadow pattern on the detector array behind the mask. By measuring of the number of neutron counts per masked and unmasked detector, and with knowledge of the mask pattern, a source image can be deconvolved to obtain a 2-d location. The number of neutrons per detector was obtained by processing the fast signal from each PMT in flash digitizing electronics. Digital pulse shape discrimination (PSD) was performed to filter out the fast-neutron signal from the γ background. The prototype instrument was tested at an indoor facility at the NRL with a 1.8-μCi and 13-μCi 252Cf neutron/γ source at three standoff distances of 9, 15 and 26 m (maximum allowed in the facility) over a 15-min integration time. The imaging and detection capabilities of the instrument were tested by moving the source in half- and one-pixel increments across the image plane. We show a representative sample of the results obtained at one-pixel increments for a standoff distance of 9 m. The 1.8-μCi source was not detected at the 26-m standoff. In order to increase the sensitivity of the instrument, we reduced the fastneutron background by shielding the top, sides and back of the detector array with 10-cm-thick HDPE. This shielding configuration led to a reduction in the background by a factor of 1.7 and thus allowed for the detection and localization of the 1.8 μCi. The detection significance for each source at different standoff distances will be discussed.

A new measurement of the 6Li(n, α)t cross section at MeV energies using a 252Cf fission chamber and 6Li scintillators

NASA Astrophysics Data System (ADS)

Kirsch, Leo E.; Devlin, M.; Mosby, S. M.; Gomez, J. A.

2017-12-01

A new measurement is presented of the 6Li(n, α)t cross section from 245 keV to 10 MeV using a 252Cf fission chamber with 6LiI(Eu) and Cs2LiYCl6:Ce (CLYC) scintillators which act as both target and detector. Neutron energies are determined from the time of flight (TOF) method using the signals from spontaneous fission and reaction product recoil. Simulations of neutron downscatter in the crystals and fission chamber bring 6Li(n, α)t cross section values measured with the 6LiI(Eu) into agreement with previous experiments and evaluations, except for two resonances at 4.2 and 6.5 MeV introduced by ENDF/B-VII.1. Suspected neutron transport modeling issues cause the cross section values obtained with CLYC to be discrepant above 2 MeV.

Prompt fission gamma-ray studies at DANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jandel, M.; Rusev, G.; Bond, E. M.

2014-11-26

Measurements of correlated data on prompt-fission γ-rays (PFG) have been carried out for various actinide isotopes in recent years using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL). We have developed a model that conveniently parametrizes the correlated data of γ-ray multiplicity and energy. New results on two- dimensional prompt-fission γ-ray multiplicity versus energy distributions from spontaneous fission on ²⁵²Cf and neutron-induced fission on 242mAm are presented together with previously obtained results on 233,235U and ²³⁹Pu. Correlated PFG data from ²⁵²Cf are also compared to results of the detailed theoretical model developed at LANL,more » for different thresholds of PFG energies. Future plans to measure correlated data on fission fragments, prompt fission neutrons and γ-rays at DANCE are presented.« less

Realization of highly efficient hexagonal boron nitride neutron detectors

DOE PAGES

Maity, A.; Doan, T. C.; Li, J.; ...

2016-08-16

Here, we report the achievement of highly efficient 10B enriched hexagonal boron nitride (h- 10BN) direct conversion neutron detectors. These detectors were realized from freestanding 4-in. diameter h- 10BN wafers 43 μm in thickness obtained from epitaxy growth and subsequent mechanical separation from sapphire substrates. Both sides of the film were subjected to ohmic contact deposition to form a simple vertical “photoconductor-type” detector. Transport measurements revealed excellent vertical transport properties including high electrical resistivity (>10 13 Ω cm) and mobility-lifetime (μτ) products. A much larger μτ product for holes compared to that of electrons along the c-axis of h- BNmore » was observed, implying that holes (electrons) behave like majority (minority) carriers in undoped h- BN. Exposure to thermal neutrons from a californium-252 ( 252Cf) source moderated by a high density polyethylene moderator reveals that 43 μm h- 10BN detectors possess 51.4% detection efficiency at a bias voltage of 400 V, which is the highest reported efficiency for any semiconductor-based neutron detector. The results point to the possibility of obtaining highly efficient, compact solid-state neutron detectors with high gamma rejection and low manufacturing and maintenance costs.« less

Estimating the Effective System Dead Time Parameter for Correlated Neutron Counting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Croft, Stephen; Cleveland, Steve; Favalli, Andrea

We present that neutron time correlation analysis is one of the main technical nuclear safeguards techniques used to verify declarations of, or to independently assay, special nuclear materials. Quantitative information is generally extracted from the neutron-event pulse train, collected from moderated assemblies of 3He proportional counters, in the form of correlated count rates that are derived from event-triggered coincidence gates. These count rates, most commonly referred to as singles, doubles and triples rates etc., when extracted using shift-register autocorrelation logic, are related to the reduced factorial moments of the time correlated clusters of neutrons emerging from the measurement items. Correctingmore » these various rates for dead time losses has received considerable attention recently. The dead time losses for the higher moments in particular, and especially for large mass (high rate and highly multiplying) items, can be significant. Consequently, even in thoughtfully designed systems, accurate dead time treatments are needed if biased mass determinations are to be avoided. In support of this effort, in this paper we discuss a new approach to experimentally estimate the effective system dead time of neutron coincidence counting systems. It involves counting a random neutron source (e.g. AmLi is a good approximation to a source without correlated emission) and relating the second and higher moments of the neutron number distribution recorded in random triggered interrogation coincidence gates to the effective value of dead time parameter. We develop the theoretical basis of the method and apply it to the Oak Ridge Large Volume Active Well Coincidence Counter using sealed AmLi radionuclide neutron sources and standard multiplicity shift register electronics. The method is simple to apply compared to the predominant present approach which involves using a set of 252Cf sources of wide emission rate, it gives excellent precision in a conveniently short time, and it yields consistent results as a function of the order of the moment used to extract the dead time parameter. In addition, this latter observation is reassuring in that it suggests the assumptions underpinning the theoretical analysis are fit for practical application purposes. However, we found that the effective dead time parameter obtained is not constant, as might be expected for a parameter that in the dead time model is characteristic of the detector system, but rather, varies systematically with gate width.« less

Estimating the Effective System Dead Time Parameter for Correlated Neutron Counting

DOE PAGES

Croft, Stephen; Cleveland, Steve; Favalli, Andrea; ...

2017-04-29

We present that neutron time correlation analysis is one of the main technical nuclear safeguards techniques used to verify declarations of, or to independently assay, special nuclear materials. Quantitative information is generally extracted from the neutron-event pulse train, collected from moderated assemblies of 3He proportional counters, in the form of correlated count rates that are derived from event-triggered coincidence gates. These count rates, most commonly referred to as singles, doubles and triples rates etc., when extracted using shift-register autocorrelation logic, are related to the reduced factorial moments of the time correlated clusters of neutrons emerging from the measurement items. Correctingmore » these various rates for dead time losses has received considerable attention recently. The dead time losses for the higher moments in particular, and especially for large mass (high rate and highly multiplying) items, can be significant. Consequently, even in thoughtfully designed systems, accurate dead time treatments are needed if biased mass determinations are to be avoided. In support of this effort, in this paper we discuss a new approach to experimentally estimate the effective system dead time of neutron coincidence counting systems. It involves counting a random neutron source (e.g. AmLi is a good approximation to a source without correlated emission) and relating the second and higher moments of the neutron number distribution recorded in random triggered interrogation coincidence gates to the effective value of dead time parameter. We develop the theoretical basis of the method and apply it to the Oak Ridge Large Volume Active Well Coincidence Counter using sealed AmLi radionuclide neutron sources and standard multiplicity shift register electronics. The method is simple to apply compared to the predominant present approach which involves using a set of 252Cf sources of wide emission rate, it gives excellent precision in a conveniently short time, and it yields consistent results as a function of the order of the moment used to extract the dead time parameter. In addition, this latter observation is reassuring in that it suggests the assumptions underpinning the theoretical analysis are fit for practical application purposes. However, we found that the effective dead time parameter obtained is not constant, as might be expected for a parameter that in the dead time model is characteristic of the detector system, but rather, varies systematically with gate width.« less

Estimating the effective system dead time parameter for correlated neutron counting

NASA Astrophysics Data System (ADS)

Croft, Stephen; Cleveland, Steve; Favalli, Andrea; McElroy, Robert D.; Simone, Angela T.

2017-11-01

Neutron time correlation analysis is one of the main technical nuclear safeguards techniques used to verify declarations of, or to independently assay, special nuclear materials. Quantitative information is generally extracted from the neutron-event pulse train, collected from moderated assemblies of 3He proportional counters, in the form of correlated count rates that are derived from event-triggered coincidence gates. These count rates, most commonly referred to as singles, doubles and triples rates etc., when extracted using shift-register autocorrelation logic, are related to the reduced factorial moments of the time correlated clusters of neutrons emerging from the measurement items. Correcting these various rates for dead time losses has received considerable attention recently. The dead time losses for the higher moments in particular, and especially for large mass (high rate and highly multiplying) items, can be significant. Consequently, even in thoughtfully designed systems, accurate dead time treatments are needed if biased mass determinations are to be avoided. In support of this effort, in this paper we discuss a new approach to experimentally estimate the effective system dead time of neutron coincidence counting systems. It involves counting a random neutron source (e.g. AmLi is a good approximation to a source without correlated emission) and relating the second and higher moments of the neutron number distribution recorded in random triggered interrogation coincidence gates to the effective value of dead time parameter. We develop the theoretical basis of the method and apply it to the Oak Ridge Large Volume Active Well Coincidence Counter using sealed AmLi radionuclide neutron sources and standard multiplicity shift register electronics. The method is simple to apply compared to the predominant present approach which involves using a set of 252Cf sources of wide emission rate, it gives excellent precision in a conveniently short time, and it yields consistent results as a function of the order of the moment used to extract the dead time parameter. This latter observation is reassuring in that it suggests the assumptions underpinning the theoretical analysis are fit for practical application purposes. However, we found that the effective dead time parameter obtained is not constant, as might be expected for a parameter that in the dead time model is characteristic of the detector system, but rather, varies systematically with gate width.

Measurement of nitrogen in the body using a commercial PGNAA system--phantom experiments.

PubMed

Chichester, D L; Empey, E

2004-01-01

An industrial prompt-gamma neutron activation analysis (PGNAA) system, originally designed for the real-time elemental analyses of bulk coal on a conveyor belt, has been studied to examine the feasibility of using such a system for body composition analysis. Experiments were conducted to measure nitrogen in a simple, tissue equivalent phantom comprised of 2.7 wt% of nitrogen. The neutron source for these experiments was 365 MBq (18.38 microg) of 252Cf located within an engineered low Z moderator and it yielded a dose rate in the measurement position of 3.91 mSv/h; data were collected using a 2780 cm(3) NaI(Tl) cylindrical detector with a digital signal processor and a 512 channel MCA. Source, moderator and detector geometries were unaltered from the system's standard configuration, where they have been optimized for considerations such as neutron thermalization, measurement sensitivity and uniformity, background radiation and external dose minimization. Based on net counts in the 10.8 MeV PGNAA nitrogen photopeak and its escape peaks the dose dependent nitrogen count rate was 11,600 counts/mSv with an uncertainty of 3.0% after 0.32 mSv (4.9 min), 2.0% after 0.74 mSv (11.4 min) and 1.0% after 3.02 mSv (46.4 min).

NSDann2BS, a neutron spectrum unfolding code based on neural networks technology and two bonner spheres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ortiz-Rodriguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.

In this work a neutron spectrum unfolding code, based on artificial intelligence technology is presented. The code called ''Neutron Spectrometry and Dosimetry with Artificial Neural Networks and two Bonner spheres'', (NSDann2BS), was designed in a graphical user interface under the LabVIEW programming environment. The main features of this code are to use an embedded artificial neural network architecture optimized with the ''Robust design of artificial neural networks methodology'' and to use two Bonner spheres as the only piece of information. In order to build the code here presented, once the net topology was optimized and properly trained, knowledge stored atmore » synaptic weights was extracted and using a graphical framework build on the LabVIEW programming environment, the NSDann2BS code was designed. This code is friendly, intuitive and easy to use for the end user. The code is freely available upon request to authors. To demonstrate the use of the neural net embedded in the NSDann2BS code, the rate counts of {sup 252}Cf, {sup 241}AmBe and {sup 239}PuBe neutron sources measured with a Bonner spheres system.« less

NSDann2BS, a neutron spectrum unfolding code based on neural networks technology and two bonner spheres

NASA Astrophysics Data System (ADS)

Ortiz-Rodríguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Solís Sánches, L. O.; Miranda, R. Castañeda; Cervantes Viramontes, J. M.; Vega-Carrillo, H. R.

2013-07-01

In this work a neutron spectrum unfolding code, based on artificial intelligence technology is presented. The code called "Neutron Spectrometry and Dosimetry with Artificial Neural Networks and two Bonner spheres", (NSDann2BS), was designed in a graphical user interface under the LabVIEW programming environment. The main features of this code are to use an embedded artificial neural network architecture optimized with the "Robust design of artificial neural networks methodology" and to use two Bonner spheres as the only piece of information. In order to build the code here presented, once the net topology was optimized and properly trained, knowledge stored at synaptic weights was extracted and using a graphical framework build on the LabVIEW programming environment, the NSDann2BS code was designed. This code is friendly, intuitive and easy to use for the end user. The code is freely available upon request to authors. To demonstrate the use of the neural net embedded in the NSDann2BS code, the rate counts of 252Cf, 241AmBe and 239PuBe neutron sources measured with a Bonner spheres system.

ORGANIC SCINTILLATOR FOR REAL-TIME NEUTRON DOSIMETRY.

PubMed

Beyer, Kyle A; Di Fulvio, Angela; Stolarczyk, Liliana; Parol, Wiktor; Mojzeszek, Natalia; Kopéc, Renata; Clarke, Shaun D; Pozzi, Sara A

2017-11-15

We developed a radiation detector based on an organic scintillator for spectrometry and dosimetry of out-of-field secondary neutrons from clinical proton beams. The detector consists of an EJ-299-34 crystalline organic scintillator, coupled by fiber optic cable to a silicon photomultiplier (SiPM). Proof of concept measurements were taken with 137Cs and 252Cf, and corresponding simulations were performed in MCNPX-PoliMi. Despite its small size, the detector is able to discriminate between neutron and gamma-rays via pulse shape discrimination. We simulated the response function of the detector to monoenergetic neutrons in the 100 keV-0 MeV range using MCNPX-PoliMi. The measured unfolded 252Cf neutron spectrum is in good agreement with the theoretical Watt fission spectrum. We determined the ambient dose equivalent by folding the spectrum with the fluence-to-ambient dose conversion coefficient, with a 1.4% deviation from theory. Some preliminary proton beam experiments were preformed at the Bronowice Cyclotron Center patient treatment facility using a clinically relevant proton pencil beam for brain tumor and craino-spinal treatment directed at a child phantom. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A Radiation Laboratory Curriculum Development at Western Kentucky University

NASA Astrophysics Data System (ADS)

Barzilov, Alexander P.; Novikov, Ivan S.; Womble, Phil C.

2009-03-01

We present the latest developments for the radiation laboratory curriculum at the Department of Physics and Astronomy of Western Kentucky University. During the last decade, the Applied Physics Institute (API) at WKU accumulated various equipment for radiation experimentation. This includes various neutron sources (computer controlled d-t and d-d neutron generators, and isotopic 252 Cf and PuBe sources), the set of gamma sources with various intensities, gamma detectors with various energy resolutions (NaI, BGO, GSO, LaBr and HPGe) and the 2.5-MeV Van de Graaff particle accelerator. XRF and XRD apparatuses are also available for students and members at the API. This equipment is currently used in numerous scientific and teaching activities. Members of the API also developed a set of laboratory activities for undergraduate students taking classes from the physics curriculum (Nuclear Physics, Atomic Physics, and Radiation Biophysics). Our goal is to develop a set of radiation laboratories, which will strengthen the curriculum of physics, chemistry, geology, biology, and environmental science at WKU. The teaching and research activities are integrated into real-world projects and hands-on activities to engage students. The proposed experiments and their relevance to the modern status of physical science are discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rogers, D.M.; Coggins, T.L.; Marsh, J.

Numerous efforts are funded by US agencies (DOE, DoD, DHS) for development of novel radiation sensing and measurement systems. An effort has been undertaken to develop a flexible shielding system compatible with a variety of sources (beta, X-ray, gamma, and neutron) that can be highly characterized using conventional radiation detection and measurement systems. Sources available for use in this system include americium-beryllium (AmBe), plutonium-beryllium (PuBe), strontium-90 (Sr-90), californium-252 (Cf-252), krypton-85 (Kr-85), americium-241 (Am-241), and depleted uranium (DU). Shielding can be varied by utilization of materials that include lexan, water, oil, lead, and polyethylene. Arrangements and geometries of source(s) and shieldingmore » can produce symmetrical or asymmetrical radiation fields. The system has been developed to facilitate accurately repeatable configurations. Measurement positions are similarly capable of being accurately re-created. Stand-off measurement positions can be accurately re-established using differential global positioning system (GPS) navigation. Instruments used to characterize individual measurement locations include a variety of sodium iodide (NaI(Tl)) (3 x 3 inch, 4 x 4 x 16 inch, Fidler) and lithium iodide (LiI(Eu)) detectors (for use with multichannel analyzer software) and detectors for use with traditional hand held survey meters such as boron trifluoride (BF{sub 3}), helium-3 ({sup 3}He), and Geiger-Mueller (GM) tubes. Also available are Global Dosimetry thermoluminescent dosimeters (TLDs), CR39 neutron chips, and film badges. Data will be presented comparing measurement techniques with shielding/source configurations. The system is demonstrated to provide a highly functional process for comparison/characterization of various detector types relative to controllable radiation types and levels. Particular attention has been paid to use of neutron sources and measurements. (authors)« less

Organic liquid scintillation detectors for on-the-fly neutron/gamma alarming and radionuclide identification in a pedestrian radiation portal monitor

NASA Astrophysics Data System (ADS)

Paff, Marc Gerrit; Ruch, Marc L.; Poitrasson-Riviere, Alexis; Sagadevan, Athena; Clarke, Shaun D.; Pozzi, Sara

2015-07-01

We present new experimental results from a radiation portal monitor based on the use of organic liquid scintillators. The system was tested as part of a 3He-free radiation portal monitor testing campaign at the European Commission's Joint Research Centre in Ispra, Italy, in February 2014. The radiation portal monitor was subjected to a wide range of test conditions described in ANSI N42.35, including a variety of gamma-ray sources and a 20,000 n/s 252Cf source. A false alarm test tested whether radiation portal monitors ever alarmed in the presence of only natural background. The University of Michigan Detection for Nuclear Nonproliferation Group's system triggered zero false alarms in 2739 trials. It consistently alarmed on a variety of gamma-ray sources travelling at 1.2 m/s at a 70 cm source to detector distance. The neutron source was detected at speeds up to 3 m/s and in configurations with up to 8 cm of high density polyethylene shielding. The success of on-the-fly radionuclide identification varied with the gamma-ray source measured as well as with which of two radionuclide identification methods was used. Both methods used a least squares comparison between the measured pulse height distributions to library spectra to pick the best match. The methods varied in how the pulse height distributions were modified prior to the least squares comparison. Correct identification rates were as high as 100% for highly enriched uranium, but as low as 50% for 241Am. Both radionuclide identification algorithms produced mixed results, but the concept of using liquid scintillation detectors for gamma-ray and neutron alarming in radiation portal monitor was validated.

Estimate of the neutron fields in ATLAS based on ATLAS-MPX detectors data

NASA Astrophysics Data System (ADS)

Bouchami, J.; Dallaire, F.; Gutiérrez, A.; Idarraga, J.; Král, V.; Leroy, C.; Picard, S.; Pospíšil, S.; Scallon, O.; Solc, J.; Suk, M.; Turecek, D.; Vykydal, Z.; Žemlièka, J.

2011-01-01

The ATLAS-MPX detectors are based on Medipix2 silicon devices designed by CERN for the detection of different types of radiation. These detectors are covered with converting layers of 6LiF and polyethylene (PE) to increase their sensitivity to thermal and fast neutrons, respectively. These devices allow the measurement of the composition and spectroscopic characteristics of the radiation field in ATLAS, particularly of neutrons. These detectors can operate in low or high preset energy threshold mode. The signature of particles interacting in a ATLAS-MPX detector at low threshold are clusters of adjacent pixels with different size and form depending on their type, energy and incidence angle. The classification of particles into different categories can be done using the geometrical parameters of these clusters. The Medipix analysis framework (MAFalda) — based on the ROOT application — allows the recognition of particle tracks left in ATLAS-MPX devices located at various positions in the ATLAS detector and cavern. The pattern recognition obtained from the application of MAFalda was configured to distinguish the response of neutrons from other radiation. The neutron response at low threshold is characterized by clusters of adjoining pixels (heavy tracks and heavy blobs) left by protons and heavy ions resulting from neutron interactions in the converting layers of the ATLAS-MPX devices. The neutron detection efficiency of ATLAS-MPX devices has been determined by the exposure of two detectors of reference to radionuclide sources of neutrons (252Cf and 241AmBe). With these results, an estimate of the neutrons fields produced at the devices locations during ATLAS operation was done.

Characterization of a 6Li-loaded liquid organic scintillator for fast neutron spectrometry and thermal neutron detection.

PubMed

Bass, C D; Beise, E J; Breuer, H; Heimbach, C R; Langford, T J; Nico, J S

2013-07-01

The characterization of a liquid scintillator incorporating an aqueous solution of enriched lithium chloride to produce a scintillator with 0.40% (6)Li is presented, including the performance of the scintillator in terms of its optical properties and neutron response. The scintillator was incorporated into a fast neutron spectrometer, and the light output spectra from 2.5 MeV, 14.1 MeV, and (252)Cf neutrons were measured using capture-gated coincidence techniques. The spectrometer was operated without coincidence to perform thermal neutron measurements. Possible improvements in spectrometer performance are discussed. Published by Elsevier Ltd.

Correlations of neutron multiplicity and γ -ray multiplicity with fragment mass and total kinetic energy in spontaneous fission of Cf 252

DOE PAGES

Wang, Taofeng; Li, Guangwu; Zhu, Liping; ...

2016-01-08

The dependence of correlations of neutron multiplicity ν and γ-ray multiplicity M γ in spontaneous fission of 252Cf on fragment mass A* and total kinetic energy (TKE) have been investigated by employing the ratio of M γ/ν and the form of M γ(ν). We show for the first time that M γ and ν have a complex correlation for heavy fragment masses, while there is a positive dependence of Mγ for light fragment masses and for near-symmetric mass splits. The ratio M γ/ν exhibits strong shell effects for neutron magic number N=50 and near doubly magic number shell closure atmore » Z=50 and N=82. The γ-ray multiplicity Mγ has a maximum for TKE=165-170 MeV. Above 170 MeV M γ(TKE) is approximately linear, while it deviates significantly from a linear dependence at lower TKE. The correlation between the average neutron and γ-ray multiplicities can be partly reproduced by model calculations.« less

Apparatus for irradiating a continuously flowing stream of fluid

DOEpatents

Speir, Leslie G.; Adams, Edwin L.

1984-01-01

An apparatus for irradiating a continuously flowing stream of fluid is diosed. The apparatus consists of a housing having a spherical cavity and a spherical moderator containing a radiation source positioned within the spherical cavity. The spherical moderator is of lesser diameter than the spherical cavity so as to define a spherical annular volume around the moderator. The housing includes fluid intake and output conduits which open onto the spherical cavity at diametrically opposite positions. Fluid flows through the cavity around the spherical moderator and is uniformly irradiated due to the 4.pi. radiation geometry. The irradiation source, for example a .sup.252 CF neutron source, is removable from the spherical moderator through a radial bore which extends outwardly to an opening on the outside of the housing. The radiation source may be routinely removed without interrupting the flow of fluid or breaching the containment of the fluid.

Assessing and minimizing contamination in time of flight based validation data

NASA Astrophysics Data System (ADS)

Lennox, Kristin P.; Rosenfield, Paul; Blair, Brenton; Kaplan, Alan; Ruz, Jaime; Glenn, Andrew; Wurtz, Ronald

2017-10-01

Time of flight experiments are the gold standard method for generating labeled training and testing data for the neutron/gamma pulse shape discrimination problem. As the popularity of supervised classification methods increases in this field, there will also be increasing reliance on time of flight data for algorithm development and evaluation. However, time of flight experiments are subject to various sources of contamination that lead to neutron and gamma pulses being mislabeled. Such labeling errors have a detrimental effect on classification algorithm training and testing, and should therefore be minimized. This paper presents a method for identifying minimally contaminated data sets from time of flight experiments and estimating the residual contamination rate. This method leverages statistical models describing neutron and gamma travel time distributions and is easily implemented using existing statistical software. The method produces a set of optimal intervals that balance the trade-off between interval size and nuisance particle contamination, and its use is demonstrated on a time of flight data set for Cf-252. The particular properties of the optimal intervals for the demonstration data are explored in detail.

On the Development of a Miniature Neutron Generator for the Brachytherapy Treatment of Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forman, L.

Brachytherapy refers to application of an irradiation source within a tumor. {sup 252}Cf needles used in brachytherapy have been successfully applied to treatment of some of the most virulent cancers but it is doubtful that it will be widely used because of difficulty in dealing with unwanted dose (source cannot be turned off) and in adhering to stringent NRC regulations that have been exacerbated in our post 911 environment. We have been working on the development of a miniature neutron generator with the reaction target placed at the end of a needle (tube) for brachytherapy applications. Orifice geometries are mostmore » amenable, e.g. rectum and cervix, but interstitial use is possible with microsurgery. This paper dicusses the results of a 30 watt DD neutron generator SBU project that demonstrates that sufficient hydrogen isotope current can be delivered down a small diameter needle required for a DT neutron treatment device, and, will summarize the progress of building a commercial device pursued by the All Russian Institute for Automatics (VNIIA) supported by the DOE's Industrial Proliferation Prevention Program (IPP). It is known that most of the fast neutron (FN) beam cancer treatment facilities have been closed down. It appears that the major limitation in the use of FN beams has been damage to healthy tissue, which is relatively insensitive to photons, but this problem is alleviated by brachytherapy. Moreover, recent clinical results indicate that fast neutrons in the boost mode are most highly effective in treating large, hypoxic, and rapidly repopulating diseases. It appears that early boost application of FN may halt angiogenesis (development and repair of tumor vascular system) and shrink the tumor resulting in lower hypoxia. The boost brachytherapy application of a small, low cost neutron generator holds promise of significant contribution to the treatment of cancer.« less

Monte Carlo Simulations Comparing the Response of a Novel Hemispherical Tepc to Existing Spherical and Cylindrical Tepcs for Neutron Monitoring and Dosimetry.

PubMed

Broughton, David P; Waker, Anthony J

2017-05-01

Neutron dosimetry in reactor fields is currently mainly conducted with unwieldy flux monitors. Tissue Equivalent Proportional Counters (TEPCs) have been shown to have the potential to improve the accuracy of neutron dosimetry in these fields, and Multi-Element Tissue Equivalent Proportional Counters (METEPCs) could reduce the size of instrumentation required to do so. Complexity of current METEPC designs has inhibited their use beyond research. This work proposes a novel hemispherical counter with a wireless anode ball in place of the traditional anode wire as a possible solution for simplifying manufacturing. The hemispherical METEPC element was analyzed as a single TEPC to first demonstrate the potential of this new design by evaluating its performance relative to the reference spherical TEPC design and a single element from a cylindrical METEPC. Energy deposition simulations were conducted using the Monte Carlo code PHITS for both monoenergetic 2.5 MeV neutrons and the neutron energy spectrum of Cf-D2O moderated. In these neutron fields, the hemispherical counter appears to be a good alternative to the reference spherical geometry, performing slightly better than the cylindrical counter, which tends to underrespond to H*(10) for the lower neutron energies of the Cf-D2O moderated field. These computational results are promising, and if follow-up experimental work demonstrates the hemispherical counter works as anticipated, it will be ready to be incorporated into an METEPC design.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, C A; Clarke, S D; Pozzi, S A

Purpose: To develop an instrument for measuring neutron and photon dose rates from mixed fields with a single device. Methods: Stilbene organic scintillators can be used to detect fast neutrons and photons. Stilbene was used to measure emission from mixed particle sources californium-252 (Cf-252) and plutonium-beryllium (PuBe). Many source detector configurations were used, along with varying amounts of shielding. Collected spectra were analyzed using pulse shape discrimination software, to separate neutron and photon interactions. With a measured light output to energy relationship the pulse height spectrum was converted to energy deposited in the detector. Energy deposited was converted to dosemore » with a variety of standard dose factors, for comparison to current methods. For validation, all measurements and processing was repeated using an EJ-309 liquid scintillator detector. Dose rates were also measured in the same configuration with commercially available dose meters for further validation. Results: Measurements of dose rates will show agreement across all methods. Higher accuracy of pulse shape discrimination at lower energies with stilbene leads to more accurate measurement of neutron and photon deposited dose. In strong fields of mixed particles discrimination can be performed well at a very low energy threshold. This shows accurate dose measurements over a large range of incident particle energy. Conclusion: Stilbene shows promise as a material for dose rate measurements due to its strong ability for separating neutrons and photon pulses and agreement with current methods. A dual particle dose meter would simplify methods which are currently limited to the measurement of only one particle type. Future work will investigate the use of a silicon photomultiplier to reduce the size and required voltage of the assembly, for practical use as a handheld survey meter, room monitor, or phantom installation. Funding From the United States Department of Energy and the National Nuclear Security Administration.« less

A new measurement of the 6Li(n,α)t cross section at MeV energies using a 252Cf fission chamber and 6Li scintillators

DOE PAGES

Kirsch, Leo Edward; Devlin, Matthew James; Mosby, Shea Morgan; ...

2017-09-01

We present a new measurement of the 6Li(n,α)t cross section from 245 keV to 10 MeV using a 252Cf fission chamber with 6LiI(Eu) and Cs 2LiYCl 6:Ce (CLYC) scintillators which act as both target and detector. Neutron energies are determined from the time of flight (TOF) method using the signals from spontaneous fission and reaction product recoil. Simulations of neutron downscatter in the crystals and fission chamber bring 6Li(n,α)t cross section values measured with the 6LiI(Eu) into agreement with previous experiments and evaluations, except for two resonances at 4.2 and 6.5 MeV introduced by ENDF/B-VII.1. Suspected neutron transport modeling issuesmore » cause the cross section values obtained with CLYC to be discrepant above 2 MeV.« less

A new measurement of the 6Li(n,α)t cross section at MeV energies using a 252Cf fission chamber and 6Li scintillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirsch, Leo Edward; Devlin, Matthew James; Mosby, Shea Morgan

We present a new measurement of the 6Li(n,α)t cross section from 245 keV to 10 MeV using a 252Cf fission chamber with 6LiI(Eu) and Cs 2LiYCl 6:Ce (CLYC) scintillators which act as both target and detector. Neutron energies are determined from the time of flight (TOF) method using the signals from spontaneous fission and reaction product recoil. Simulations of neutron downscatter in the crystals and fission chamber bring 6Li(n,α)t cross section values measured with the 6LiI(Eu) into agreement with previous experiments and evaluations, except for two resonances at 4.2 and 6.5 MeV introduced by ENDF/B-VII.1. Suspected neutron transport modeling issuesmore » cause the cross section values obtained with CLYC to be discrepant above 2 MeV.« less

Evaluation Of Shielding Efficacy Of A Ferrite Containing Ceramic Material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verst, C.

2015-10-12

The shielding evaluation of the ferrite based Mitsuishi ceramic material has produced for several radiation sources and possible shielding sizes comparative dose attenuation measurements and simulated projections. High resolution gamma spectroscopy provided uncollided and scattered photon spectra at three energies, confirming theoretical estimates of the ceramic’s mass attenuation coefficient, μ/ρ. High level irradiation experiments were performed using Co-60, Cs-137, and Cf-252 sources to measure penetrating dose rates through steel, lead, concrete, and the provided ceramic slabs. The results were used to validate the radiation transport code MCNP6 which was then used to generate dose rate attenuation curves as a functionmore » of shielding material, thickness, and mass for photons and neutrons ranging in energy from 200 keV to 2 MeV.« less

Report of the Snowmass M6 Working Group on high intensity proton sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weiren Chou and J. Wei

The U.S. high-energy physics program needs an intense proton source, a 1-4 MW Proton Driver (PD), by the end of this decade. This machine will serve as a stand-alone facility that will provide neutrino superbeams and other high intensity secondary beams such as kaons, muons, neutrons, and anti-protons (cf. E1 and E5 group reports) and also serve as the first stage of a neutrino factory (cf. M1 group report). It can also be a high brightness source for a VLHC. Based on present accelerator technology and project construction experience, it is both feasible and cost-effective to construct a 1-4 MWmore » Proton Driver. Two recent PD design studies have been made, one at FNAL and the other at the BNL. Both designed PD's for 1 MW proton beams at a cost of about U.S. $200M (excluding contingency and overhead) and both designs were upgradeable to 4 MW. An international collaboration between FNAL, BNL and KEK on high intensity proton facilities is addressing a number of key design issues. The superconducting (sc) RF cavities, cryogenics, and RF controls developed for the SNS can be directly adopted to save R&D efforts, cost, and schedule. PD studies are also actively being pursued at Europe and Japan.« less

μ CF Study of D/T and H/D/T Mixtures in Homogeneous and Inhomogeneous Medium, and Comparison of Their Fusion Yields

NASA Astrophysics Data System (ADS)

Eskandari, M. R.; Faghihi, F.; Gheisari, R.

Muon reactivation coefficient are determined for muonic He (He = 42He = α , He = 23 He = h) for up to six (n = 1, 2, 3, ..., 6) states of formation and at temperature Tp = 100 eV and for various relative ion densities. In the next decade it may be possible to explore new conditions for further energy gain in muon catalyzed fusion system, μ CF, using nonuniform (temperature and density) plasma states. Here, we have considered a model for inhomogeneous μ CF for mixtures of D/T and H/D/T. Using coupled dynamical equations it is shown that the neutrons yield per muon injection, Yn (neutrons/muon), in the dt branch of an inhomogeneous H/D/T mixture is at least 2.24 times higher than similar homogeneous systems and this rate for a D/T mixture is 1.92. Also, we have compared the neutron yield in the dt branch of homogeneous D/T and H/D/T mixtures (temperature range T = 300-800 K, and density φ = 1 LHD). It is shown that Yn(D/T)/Yn(H/D/T) = 1.32, which is in good agreement with recently measured experimental values. In other words our calculations show that the addition of protonium to a D/T mixture leads to a significant decrease in the cycling rate for the physical conditions described herein.

Nuclear-Recoil Energy Scale in CDMS II Silicon Dark-Matter Detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agnese, R.; et al.

The Cryogenic Dark Matter Search (CDMS II) experiment aims to detect dark matter particles that elastically scatter from nuclei in semiconductor detectors. The resulting nuclear-recoil energy depositions are detected by ionization and phonon sensors. Neutrons produce a similar spectrum of low-energy nuclear recoils in such detectors, while most other backgrounds produce electron recoils. The absolute energy scale for nuclear recoils is necessary to interpret results correctly. The energy scale can be determined in CDMS II silicon detectors using neutrons incident from a broad-spectrummore » $$^{252}$$Cf source, taking advantage of a prominent resonance in the neutron elastic scattering cross section of silicon at a recoil (neutron) energy near 20 (182) keV. Results indicate that the phonon collection efficiency for nuclear recoils is $$4.8^{+0.7}_{-0.9}$$% lower than for electron recoils of the same energy. Comparisons of the ionization signals for nuclear recoils to those measured previously by other groups at higher electric fields indicate that the ionization collection efficiency for CDMS II silicon detectors operated at $$\\sim$$4 V/cm is consistent with 100% for nuclear recoils below 20 keV and gradually decreases for larger energies to $$\\sim$$75% at 100 keV. The impact of these measurements on previously published CDMS II silicon results is small.« less

Coupled multi-group neutron photon transport for the simulation of high-resolution gamma-ray spectroscopy applications

NASA Astrophysics Data System (ADS)

Burns, Kimberly Ann

The accurate and efficient simulation of coupled neutron-photon problems is necessary for several important radiation detection applications. Examples include the detection of nuclear threats concealed in cargo containers and prompt gamma neutron activation analysis for nondestructive determination of elemental composition of unknown samples. In these applications, high-resolution gamma-ray spectrometers are used to preserve as much information as possible about the emitted photon flux, which consists of both continuum and characteristic gamma rays with discrete energies. Monte Carlo transport is the most commonly used modeling tool for this type of problem, but computational times for many problems can be prohibitive. This work explores the use of coupled Monte Carlo-deterministic methods for the simulation of neutron-induced photons for high-resolution gamma-ray spectroscopy applications. RAdiation Detection Scenario Analysis Toolbox (RADSAT), a code which couples deterministic and Monte Carlo transport to perform radiation detection scenario analysis in three dimensions [1], was used as the building block for the methods derived in this work. RADSAT was capable of performing coupled deterministic-Monte Carlo simulations for gamma-only and neutron-only problems. The purpose of this work was to develop the methodology necessary to perform coupled neutron-photon calculations and add this capability to RADSAT. Performing coupled neutron-photon calculations requires four main steps: the deterministic neutron transport calculation, the neutron-induced photon spectrum calculation, the deterministic photon transport calculation, and the Monte Carlo detector response calculation. The necessary requirements for each of these steps were determined. A major challenge in utilizing multigroup deterministic transport methods for neutron-photon problems was maintaining the discrete neutron-induced photon signatures throughout the simulation. Existing coupled neutron-photon cross-section libraries and the methods used to produce neutron-induced photons were unsuitable for high-resolution gamma-ray spectroscopy applications. Central to this work was the development of a method for generating multigroup neutron-photon cross-sections in a way that separates the discrete and continuum photon emissions so the neutron-induced photon signatures were preserved. The RADSAT-NG cross-section library was developed as a specialized multigroup neutron-photon cross-section set for the simulation of high-resolution gamma-ray spectroscopy applications. The methodology and cross sections were tested using code-to-code comparison with MCNP5 [2] and NJOY [3]. A simple benchmark geometry was used for all cases compared with MCNP. The geometry consists of a cubical sample with a 252Cf neutron source on one side and a HPGe gamma-ray spectrometer on the opposing side. Different materials were examined in the cubical sample: polyethylene (C2H4), P, N, O, and Fe. The cross sections for each of the materials were compared to cross sections collapsed using NJOY. Comparisons of the volume-averaged neutron flux within the sample, volume-averaged photon flux within the detector, and high-purity gamma-ray spectrometer response (only for polyethylene) were completed using RADSAT and MCNP. The code-to-code comparisons show promising results for the coupled Monte Carlo-deterministic method. The RADSAT-NG cross-section production method showed good agreement with NJOY for all materials considered although some additional work is needed in the resonance region and in the first and last energy bin. Some cross section discrepancies existed in the lowest and highest energy bin, but the overall shape and magnitude of the two methods agreed. For the volume-averaged photon flux within the detector, typically the five most intense lines agree to within approximately 5% of the MCNP calculated flux for all of materials considered. The agreement in the code-to-code comparisons cases demonstrates a proof-of-concept of the method for use in RADSAT for coupled neutron-photon problems in high-resolution gamma-ray spectroscopy applications. One of the primary motivators for using the coupled method over pure Monte Carlo method is the potential for significantly lower computational times. For the code-to-code comparison cases, the run times for RADSAT were approximately 25--500 times shorter than for MCNP, as shown in Table 1. This was assuming a 40 mCi 252Cf neutron source and 600 seconds of "real-world" measurement time. The only variance reduction technique implemented in the MCNP calculation was forward biasing of the source toward the sample target. Improved MCNP runtimes could be achieved with the addition of more advanced variance reduction techniques.

Future research program on prompt γ-ray emission in nuclear fission

NASA Astrophysics Data System (ADS)

Oberstedt, S.; Billnert, R.; Hambsch, F.-J.; Lebois, M.; Oberstedt, A.; Wilson, J. N.

2015-12-01

In recent years the measurement of prompt fission γ-ray spectra (PFGS) has gained renewed interest, after about forty years since the first comprehensive studies of the reactions 235U(n th , f), 239Pu(n th ,f) and 252Cf(sf). The renaissance was initiated by requests for new values especially for γ-ray multiplicity and average total energy release per fission in neutron-induced fission of 235U and 239Pu. Both isotopes are considered the most important ones with respect to the modeling of innovative cores required for the Generation-IV reactors, the majority working with fast neutrons. During the last 5 years we have conducted a systematic study of spectral data for thermal-neutron-induced fission on 235U and 241Pu as well as for the spontaneous fission of 252Cf with unprecedented accuracy. From the new data we conclude that those reactions do not considerably contribute to the observed heat excess and suspect other reactions playing a significant role. Possible contributions may originate from fast-neutron-induced reactions on 238U, which is largely present in the fuel, or from γ-induced fission from neutron capture in the construction material. A first experiment campaign on prompt γ-ray emission from fast-neutron-induced fission on 235,238U was successfully performed in order to test our assumptions. In the following we attempt to summarize, what has been done in the field to date, and to motivate future measurement campaigns exploiting dedicated neutron and photon beams as well as upcoming highly efficient detector assemblies.

Applications of Elpasolites as a Multimode Radiation Sensor

NASA Astrophysics Data System (ADS)

Guckes, Amber

This study consists of both computational and experimental investigations. The computational results enabled detector design selections and confirmed experimental results. The experimental results determined that the CLYC scintillation detector can be applied as a functional and field-deployable multimode radiation sensor. The computational study utilized MCNP6 code to investigate the response of CLYC to various incident radiations and to determine the feasibility of its application as a handheld multimode sensor and as a single-scintillator collimated directional detection system. These simulations include: • Characterization of the response of the CLYC scintillator to gamma-rays and neutrons; • Study of the isotopic enrichment of 7Li versus 6Li in the CLYC for optimal detection of both thermal neutrons and fast neutrons; • Analysis of collimator designs to determine the optimal collimator for the single CLYC sensor directional detection system to assay gamma rays and neutrons; Simulations of a handheld CLYC multimode sensor and a single CLYC scintillator collimated directional detection system with the optimized collimator to determine the feasibility of detecting nuclear materials that could be encountered during field operations. These nuclear materials include depleted uranium, natural uranium, low-enriched uranium, highly-enriched uranium, reactor-grade plutonium, and weapons-grade plutonium. The experimental study includes the design, construction, and testing of both a handheld CLYC multimode sensor and a single CLYC scintillator collimated directional detection system. Both were designed in the Inventor CAD software and based on results of the computational study to optimize its performance. The handheld CLYC multimode sensor is modular, scalable, low?power, and optimized for high count rates. Commercial?off?the?shelf components were used where possible in order to optimize size, increase robustness, and minimize cost. The handheld CLYC multimode sensor was successfully tested to confirm its ability for gamma-ray and neutron detection, and gamma?ray and neutron spectroscopy. The sensor utilizes wireless data transfer for possible radiation mapping and network?centric deployment. The handheld multimode sensor was tested by performing laboratory measurements with various gamma-ray sources and neutron sources. The single CLYC scintillator collimated directional detection system is portable, robust, and capable of source localization and identification. The collimator was designed based on the results of the computational study and is constructed with high density polyethylene (HDPE) and lead (Pb). The collimator design and construction allows for the directional detection of gamma rays and fast neutrons utilizing only one scintillator which is interchangeable. For this study, a CLYC-7 scintillator was used. The collimated directional detection system was tested by performing laboratory directional measurements with various gamma-ray sources, 252Cf and a 239PuBe source.

Two detector arrays for fast neutrons at LANSCE

NASA Astrophysics Data System (ADS)

Haight, R. C.; Lee, H. Y.; Taddeucci, T. N.; O'Donnell, J. M.; Perdue, B. A.; Fotiades, N.; Devlin, M.; Ullmann, J. L.; Laptev, A.; Bredeweg, T.; Jandel, M.; Nelson, R. O.; Wender, S. A.; White, M. C.; Wu, C. Y.; Kwan, E.; Chyzh, A.; Henderson, R.; Gostic, J.

2012-03-01

The neutron spectrum from neutron-induced fission needs to be known in designing new fast reactors, predicting criticality for safety analyses, and developing techniques for global security application. The experimental data base of fission neutron spectra is very incomplete and most present evaluated libraries are based on the approach of the Los Alamos Model. To validate these models and to provide improved data for applications, a program is underway to measure the fission neutron spectrum for a wide range of incident neutron energies using the spallation source of fast neutrons at the Weapons Neutron Research (WNR) facility at the Los Alamos Neutron Science Center (LANSCE). In a double time-of-flight experiment, fission neutrons are detected by arrays of neutron detectors to increase the solid angle and also to investigate possible angular dependence of the fission neutrons. The challenge is to measure the spectrum from low energies, down to 100 keV or so, to energies over 10 MeV, where the evaporation-like spectrum decreases by 3 orders of magnitude from its peak around 1 MeV. For these measurements, we are developing two arrays of neutron detectors, one based on liquid organic scintillators and the other on 6Li-glass detectors. The range of fission neutrons detected by organic liquid scintillators extends from about 600 keV to well over 10 MeV, with the lower limit being defined by the limit of pulse-shape discrimination. The 6Li-glass detectors have a range from very low energies to about 1 MeV, where their efficiency then becomes small. Various considerations and tests are in progress to understand important contributing factors in designing these two arrays and they include selection and characterization of photomultiplier tubes (PM), the performance of relatively thin (1.8 cm) 6Li-glass scintillators on 12.5 cm diameter PM tubes, use of 17.5 cm diameter liquid scintillators with 12.5 cm PM tubes, measurements of detector efficiencies with tagged neutrons from the WNR/LANSCE neutron beam, and efficiency calibration with 252Cf spontaneous fission neutrons. Design considerations and test results are presented.

Update of the α - n Yields for Reactor Fuel Materials for the Interest of Nuclear Safeguards

NASA Astrophysics Data System (ADS)

Simakov, S. P.; van den Berg, Q. Y.

2017-01-01

The neutron yields caused by spontaneous α-decay of actinides and subsequent (α,xn) reactions were re-evaluated for the reactor fuel materials UO2, UF6, PuO2 and PuF4. For this purpose, the most recent reference data for decay parameters, α-particle stopping powers and (α,xn) cross sections were collected, analysed and used in calculations. The input data and elaborated code were validated against available thick target neutron yields in pure and compound materials measured at accelerators or with radioactive sources. This paper provides the specific neutron yields and their uncertainties resultant from α-decay of actinides 241Am, 249Bk, 252Cf, 242,244Cm, 237Np, 238-242Pu, 232Th and 232-236,238U in oxide and fluoride compounds. The obtained results are an update of previous reference tables issued by the Los Alamos National Laboratory in 1991 which were used for the safeguarding of radioactive materials by passive non-destructive techniques. The comparison of the updated values with previous ones shows an agreement within one estimated uncertainty (≈ 10%) for oxides, and deviations of up to 50% for fluorides.

Trail of Black Holes and Neutron Stars Points to Ancient Collision

NASA Astrophysics Data System (ADS)

2003-12-01

An image of an elliptical galaxy by NASA's Chandra X-ray Observatory has revealed a trail of black holes and neutron stars stretching more than fifty thousand light years across space. The trail of intense X-ray sources is evidence that this apparently sedate galaxy collided with another galaxy a few billion years ago. "This discovery shows that X-ray observations may be the best way to identify the ancient remains of mergers between galaxies," said Lars Hernquist of the Harvard-Smithsonian Center for Astrophysics in Cambridge (CfA), Massachusetts, and a coauthor on an article on the galaxy NGC 4261 in an upcoming issue of The Astrophysical Journal Letters. "It could be a significant tool for probing the origin of elliptical galaxies." "From the optical and radio images, we knew something unusual was going on in the nucleus of this galaxy, but the real surprise turned out to be on the outer edges of the galaxy," said Andreas Zezas, also of CfA, and lead-author of the paper on NGC 4261. "Dozens of black holes and neutron stars were strung out across space like beads on a necklace." The spectacular structure is thought to represent the aftermath of the destruction of a smaller galaxy that was pulled apart by gravitational tidal forces as it fell into NGC 4261. As the doomed galaxy fell into the larger one, large streams of gas were pulled out into long tidal tails. Shock waves generated as these tidal tails fell into the larger galaxy triggered the formation of large numbers of massive stars which over the course of a few million years evolved into neutron stars or black holes. A few of these extremely compact objects had companion stars, and became bright X-ray sources as gas from the companions was captured by the intense gravitational fields of the neutron stars and black holes. The origin of elliptical galaxies has long been a subject of intense debate among astronomers. The currently favored view is that they are produced by collisions between spiral galaxies. Computer simulations of galaxy collisions support this idea, and optical evidence of tails, shells, ripples, arcs and other structures have been interpreted as evidence for this theory. However the optical evidence rather quickly fades into the starry background of the galaxy, whereas the NGC 4261 X-ray observations show that the X-ray signature may linger for hundreds of millions of years. NGC 4261 is approximately 100 million light years away from Earth. The data for these results were taken from the Chandra archive. NGC 4261 was originally observed with the Advanced CCD Imaging Spectrometer on May 6, 2000. Other members of the research team were Pepi Fabbiano and Jon Miller, both from the CfA. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the Office of Space Science, NASA Headquarters, Washington. Northrop Grumman of Redondo Beach, Calif., formerly TRW, Inc., was the prime development contractor for the observatory. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass. Additional information and images are available at: http://chandra.harvard.edu and http://chandra.nasa.gov

An evaluation of a manganese bath system having a new geometry through MCNP modelling.

PubMed

Khabaz, Rahim

2012-12-01

In this study, an approximate symmetric cylindrical manganese bath system with equal diameter and height was appraised using a Monte Carlo simulation. For nine sizes of the tank filled with MnSO(4).H(2)O solution of three different concentrations, the necessary correction factors involved in the absolute measurement of neutron emission rate were determined by a detailed modelling of the MCNP4C code with the ENDF/B-VII.0 neutron cross section data library. The results obtained were also used to determine the optimum dimensions of the bath for each concentration of solution in the calibration of (241)Am-Be and (252)Cf sources. Also, the amount of gamma radiation produced as a result of (n,γ) the reaction with the nuclei of the manganese sulphate solution that escaped from the boundary of each tank was evaluated. This gamma can be important for the background in NaI(Tl) detectors and issues concerned with radiation protection.

Single Event Upset in Static Random Access Memories in Atmospheric Neutron Environments

NASA Astrophysics Data System (ADS)

Arita, Yutaka; Takai, Mikio; Ogawa, Izumi; Kishimoto, Tadafumi

2003-07-01

Single-event upsets (SEUs) in a 0.4 μm 4 Mbit complementary metal oxide semiconductor (CMOS) static random access memory (SRAM) were investigated in various atmospheric neutron environments at sea level, at an altitude of 2612 m mountain, at an altitude of commercial airplane, and at an underground depth of 476 m. Neutron-induced SEUs increase with the increase in altitude. For a device with a borophosphosilicate glass (BPSG) film, SEU rates induced by thermal neutrons increase with the decrease in the cell charge of a memory cell. A thermal neutron-induced SEU is significant in SRAMs with a small cell charge. With the conditions of small cell charge, thermal neutron-induced SEUs account for 60% or more of the total neutron-induced SEUs. The SEU rate induced by atmospheric thermal neutrons can be estimated by an acceleration test using 252Cf.

Measurement of Fission Neutron Spectrum and Multiplicity using a Gamma Tag Double Time-of-flight Setup

NASA Astrophysics Data System (ADS)

Blain, E.; Daskalakis, A.; Danon, Y.

2014-05-01

Recent efforts have been made to improve the prompt fission neutron spectrum and nu-bar measurements for Uranium and Plutonium isotopes particularly in the keV region. A system has been designed at Rensselaer Polytechnic Institute (RPI) utilizing an array of EJ-301 liquid scintillators as well as lithium glass and plastic scintillators to experimentally determine these values. An array of BaF2 detectors was recently obtained from Oak Ridge National Laboratory to be used in conjunction with the neutron detectors. The system uses a novel gamma tagging method for fission which can offer an improvement over conventional fission chambers due to increased sample mass. A coincidence requirement on the gamma detectors from prompt fission gammas is used as the fission tag for the system as opposed to fission fragments in a conventional fission chamber. The system utilizes pulse digitization using Acqiris 8 bit digitizer boards which allow for gamma/neutron pulse height discrimination on the liquid scintillators during post processing. Additionally, a 252Cf fission chamber was designed and constructed at RPI which allowed for optimization and testing of the system without the need for an external neutron source. The characteristics of the gamma tagging method such as false detection rate and detection efficiency were determined using this fission chamber and verified using MCNP Polimi modeling. Prompt fission neutron spectrum data has been taken using the fission chamber focusing on the minimum detectable neutron energy for each of the various detectors. Plastic scintillators were found to offer a significant improvement over traditional liquid scintillators allowing energy measurements down to 50 keV. Background was also characterized for all detectors and will be discussed.

Experimental study on the measurement of uranium casting enrichment by time-dependent coincidence method

NASA Astrophysics Data System (ADS)

Xie, Wen-Xiong; Li, Jian-Sheng; Gong, Jian; Zhu, Jian-Yu; Huang, Po

2013-10-01

Based on the time-dependent coincidence method, a preliminary experiment has been performed on uranium metal castings with similar quality (about 8-10 kg) and shape (hemispherical shell) in different enrichments using neutron from Cf fast fission chamber and timing DT accelerator. Groups of related parameters can be obtained by analyzing the features of time-dependent coincidence counts between source-detector and two detectors to characterize the fission signal. These parameters have high sensitivity to the enrichment, the sensitivity coefficient (defined as (ΔR/Δm)/R¯) can reach 19.3% per kg of 235U. We can distinguish uranium castings with different enrichments to hold nuclear weapon verification.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milbrandt, Anelia; Booth, Samuel

Carbon fiber (CF), known also as graphite fiber, is a lightweight, strong, and flexible material used in both structural (load-bearing) and non-structural applications (e.g., thermal insulation). The high cost of precursors (the starting material used to make CF, which comes predominately from fossil sources) and manufacturing have kept CF a niche market with applications limited mostly to high-performance structural materials (e.g., aerospace). Alternative precursors to reduce CF cost and dependence on fossil sources have been investigated over the years, including biomass-derived precursors such as rayon, lignin, glycerol, and lignocellulosic sugars. The purpose of this study is to provide a comprehensivemore » overview of CF precursors from biomass and their market potential. We examine the potential CF production from these precursors, the state of technology and applications, and the production cost (when data are available). We discuss their advantages and limitations. We also discuss the physical properties of biomass-based CF, and we compare them to those of polyacrylonitrile (PAN)-based CF. We also discuss manufacturing and end-product considerations for bio-based CF, as well as considerations for plant siting and biomass feedstock logistics, feedstock competition, and risk mitigation strategies. The main contribution of this study is that it provides detailed technical and market information about each bio-based CF precursor in one document while other studies focus on one precursor at a time or a particular topic (e.g., processing). Thus, this publication allows for a comprehensive view of the CF potential from all biomass sources and serves as a reference for both novice and experienced professionals interested in CF production from alternative sources.« less

Prompt Neutron Time Decay in Single HEU and DU Metal Annular Storage Castings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pena, Kirsten E; McConchie, Seth M; Mihalczo, John T

2010-01-01

Previous measurements of highly enriched uranium (HEU) storage castings performed by Oak Ridge National Laboratory (ORNL) at the Y-12 National Security Complex showed a prompt neutron time decay that is not exponential. These measurements showed that multiple time constants originating from multiplication, time-of-flight, scattering in the assembly and room return could be associated with this prompt neutron decay. In this work, the contribution not associated with neutron multiplication was investigated via measurements with a depleted uranium (DU) casting. The measurements at ORNL used an annular (5.0-in OD, 3.5-in ID, 6.0-in H) DU casting with a time-tagged 252Cf source, centered verticallymore » on the axis, and four closely coupled 1 1 6-in.-long plastic scintillators with -in.- thick lead shielding adjacent to the outer surface of the casting. This setup was identical to the configuration used in the previously performed measurements with HEU castings at Y-12. The time correlation between fission events and detections in the plastic scintillators was measured, as well as the time distribution of coincidences between multiple detectors within a 512-ns time window. The measurement results were then compared to MCNP-PoliMi calculations and the previous HEU measurements. Time constants from decay fits to the HEU and DU data were compared to characterize the contributions resulting from multiplication, time-of-flight, and scattering.« less

Study of sampling rate influence on neutron-gamma discrimination with stilbene coupled to a silicon photomultiplier.

PubMed

Zhang, Jinglong; Moore, Michael E; Wang, Zhonghai; Rong, Zhou; Yang, Chaowen; Hayward, Jason P

2017-10-01

Choosing a digitizer with an appropriate sampling rate is often a trade-off between performance and economy. The influence of sampling rates on the neutron-gamma Pulse Shape Discrimination (PSD) with a solid stilbene scintillator coupled to a Silicon Photomultiplier was investigated in this work. Sampling rates from 125MSPS to 2GSPS from a 10-bit digitizer were used to collect detector pulses produced by the interactions of a Cf-252 source. Due to the decreased signal-to-noise ratio (SNR), the PSD performance degraded with reduced sampling rates. The reason of PSD performance degradation was discussed. Then, an efficient combination of filtering and digital signal processing (DSP) was then applied to suppress the timing noise and electronic background noise. The results demonstrate an improved PSD performance especially at low sampling rates, down to 125MSPS. Using filtering and DSP, the ascribed Figure of Merit (FOM) at 125keV ee (± 10keV ee ) increased from 0.95 to 1.02 at 125MSPS. At 300keV ee and above, all the FOMs are better than 2.00. Our study suggests that 250MSPS is a good enough sampling rate for neutron-gamma discrimination in this system in order to be sensitive to neutrons at and above ~ 125keV ee . Copyright © 2017 Elsevier Ltd. All rights reserved.

Neutron-induced fission: properties of prompt neutron and γ rays as a function of incident energy

NASA Astrophysics Data System (ADS)

Stetcu, I.; Talou, P.; Kawano, T.

2016-06-01

We have applied the Hauser-Feshbach statistical theory, in a Monte-Carlo implementation, to the de-excitation of fission fragments, obtaining a reasonable description of the characteristics of neutrons and gamma rays emitted before beta decays toward stability. Originally implemented for the spontaneous fission of 252Cf and the neutroninduced fission of 235U and 239Pu at thermal neutron energy, in this contribution we discuss the extension of the formalism to incident neutron energies up to 20 MeV. For the emission of pre-fission neutrons, at incident energies beyond second-chance fission, we take into account both the pre-equilibrium and statistical pre-fission components. Phenomenological parameterizations of mass, charge and TKE yields are used to obtain the initial conditions for the fission fragments that subsequently decay via neutron and emissions. We illustrate this approach for 239Pu(n,f).

Visualization of water usage and photosynthetic activity of street trees exposed to 2 ppm of SO 2—A combined evaluation by cold neutron and chlorophyll fluorescence imaging

NASA Astrophysics Data System (ADS)

Matsushima, U.; Kardjilov, N.; Hilger, A.; Manke, I.; Shono, H.; Herppich, W. B.

2009-06-01

Photosynthetic efficacy and auto-exhaust-fume resistance of street trees were evaluated by cold neutron radiography (CNR) with D 2O tracer and chlorophyll fluorescence (CF) imaging. With these techniques, information on the responses of water usage and photosynthetic activity of plants exposed to simulate toxic auto-exhaust fumes (2 ppm SO 2 in air) were obtained. Branches of hibiscus trees were detached, placed into a tub with aerated water and used for the experiments after rooting. A CF image was taken before SO 2 was applied for 1 h. During the experiment, CNR and CF imaging were conduced. H 2O and D 2O in the plant container were exchanged every 30 min to observe water uptake. D 2O tracer clearly showed water uptake into the hibiscus stem during each treatment. When the atmosphere was changed from simulated auto-exhaust fumes to normal air again, the amount of D 2O and, hence, water uptake increased. CF imaging was well suited to evaluate the effects of SO 2 as simulated toxic auto-exhaust fumes on plants. The maximum photochemical efficiency ( Fv/ Fm), a sensitive indicator of the efficacy and the integrity of plants' photosynthesis, immediately dropped by 30% after supplying the simulated auto-exhaust fumes. This indicates that toxic auto-exhaust fumes negatively affected the photosynthetic activity of hibiscus leaves. Simultaneous CNR and CF imaging successfully visualized variations of photosynthetic activity and water uptake in the sample. Thus, this combination method was effective to non-destructive analyze the physiological status of plants.

Charge breeding results and future prospects with electron cyclotron resonance ion source and electron beam ion source (invited)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vondrasek, R.; Levand, A.; Pardo, R.

2012-02-15

The Californium Rare Ion Breeder Upgrade (CARIBU) of the Argonne National Laboratory ATLAS facility will provide low-energy and reaccelerated neutron-rich radioactive beams for the nuclear physics program. A 70 mCi {sup 252}Cf source produces fission fragments which are thermalized and collected by a helium gas catcher into a low-energy particle beam with a charge of 1+ or 2+. An electron cyclotron resonance (ECR) ion source functions as a charge breeder in order to raise the ion charge sufficiently for acceleration in the ATLAS linac. The final CARIBU configuration will utilize a 1 Ci {sup 252}Cf source to produce radioactive beamsmore » with intensities up to 10{sup 6} ions/s for use in the ATLAS facility. The ECR charge breeder has been tested with stable beam injection and has achieved charge breeding efficiencies of 3.6% for {sup 23}Na{sup 8+}, 15.6% for {sup 84}Kr{sup 17+}, and 13.7% for {sup 85}Rb{sup 19+} with typical breeding times of 10 ms/charge state. For the first radioactive beams, a charge breeding efficiency of 11.7% has been achieved for {sup 143}Cs{sup 27+} and 14.7% for {sup 143}Ba{sup 27+}. The project has been commissioned with a radioactive beam of {sup 143}Ba{sup 27+} accelerated to 6.1 MeV/u. In order to take advantage of its lower residual contamination, an EBIS charge breeder will replace the ECR charge breeder in the next two years. The advantages and disadvantages of the two techniques are compared taking into account the requirements of the next generation radioactive beam facilities.« less

Superconducting High Resolution Fast-Neutron Spectrometers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hau, Ionel Dragos

2006-01-01

Superconducting high resolution fast-neutron calorimetric spectrometers based on 6LiF and TiB{sub 2} absorbers have been developed. These novel cryogenic spectrometers measure the temperature rise produced in exothermal (n, α) reactions with fast neutrons in 6Li and 10B-loaded materials with heat capacity C operating at temperatures T close to 0.1 K. Temperature variations on the order of 0.5 mK are measured with a Mo/Cu thin film multilayer operated in the transition region between its superconducting and its normal state. The advantage of calorimetry for high resolution spectroscopy is due to the small phonon excitation energies k BT on the order ofmore » μeV that serve as signal carriers, resulting in an energy resolution ΔE ~ (k BT 2C) 1/2, which can be well below 10 keV. An energy resolution of 5.5 keV has been obtained with a Mo/Cu superconducting sensor and a TiB 2 absorber using thermal neutrons from a 252Cf neutron source. This resolution is sufficient to observe the effect of recoil nuclei broadening in neutron spectra, which has been related to the lifetime of the first excited state in 7Li. Fast-neutron spectra obtained with a 6Li-enriched LiF absorber show an energy resolution of 16 keV FWHM, and a response in agreement with the 6Li(n, α) 3H reaction cross section and Monte Carlo simulations for energies up to several MeV. The energy resolution of order of a few keV makes this novel instrument applicable to fast-neutron transmission spectroscopy based on the unique elemental signature provided by the neutron absorption and scattering resonances. The optimization of the energy resolution based on analytical and numerical models of the detector response is discussed in the context of these applications.« less

Reflection Asymmetric Shapes in the Neutron-Rich 140,143Ba Isotopes

NASA Astrophysics Data System (ADS)

Zhu Sheng-jiang (S, J. Zhu; Wang, Mu-ge; J, H. Hamilton; A, V. Ramayya; B, R. S. Babu; W, C. Ma; Long, Gui-lu; Deng, Jing-kang; Zhu, Ling-yan; Li, Ming; T, N. Ginter; J, Komicki; J, D. Cole; R, Aryaeinejad; Y, K. Dardenne; M, W. Drigert; J, O. Rasmussen; Ts, Yu Oganessian; M, A. Stoyer; S, Y. Chu; K, E. Gregorich; M, F. Mohar; S, G. Prussin; I, Y. Lee; N, R. Johnson; F, K. McGowan

1997-08-01

Level schemes for the neutron-rich 140,143Ba nuclei have been determined by study of prompt γ-rays in spontaneous fission of 252Cf. The level pattern and enhanced E1 transitions between π = + and π = - bands show reflection asymmetric shapes with simplex quantum number s = +1 in 140Ba and s = ±i in 143Ba, respectively. The octupole deformation stability with spin variation has been discussed.

Neutron investigation of Nd 2- x- yCe xLa yCuO 4 (0 ⩽ x ⩽ 0.2; y = 0.5, 1)

NASA Astrophysics Data System (ADS)

Gutmann, M.; Allenspach, P.; Fauth, F.; Furrer, A.; Zolliker, M.; Rosenkranz, S.; Eccleston, R. S.

1997-02-01

We present neutron diffraction and crystal field (CF) spectroscopy results obtained for the electron-doped superconductor precursor material Nd 2- x- yCe xLa yCuO 4 (0 ⩽ x ⩽ 0.2; y = 0.5, 1). Samples were prepared via a sol-gel methods. The lattice constants as a function of Ce-doping show the well-known behavior common to this class of compounds, i.e. the a parameter increases while the c parameter decreases with increasing Ce amount. The presence of La expands the unit cell in all directions compared to the mother compound Nd 2CuO 4 while preserving the T‧-structure for the above mentioned range. The CF spectra clearly show the presence of electronic inhomogeneities associated with electron doping from Ce 4+ on one Cu-site in the CuO 2-planes.

Californium purification and electrodeposition

DOE PAGES

Burns, Jonathan D.; Van Cleve, Shelley M.; Smith, Edward Hamilton; ...

2014-11-30

The staff at the Radiochemical Engineering Development Center, located at Oak Ridge National Laboratory, produced a 6.3 ± 0.4 GBq (1.7 ± 0.1 Ci) 252Cf source for the Californium Rare Isotope Breeder Upgrade (CARIBU) project at Argonne National Laboratory’s Argonne Tandem Linac Accelerator System. The source was produced by electrodeposition of a 252Cf sample onto a stainless steel substrate, which required material free from excess mass for efficient deposition. The resulting deposition was the largest reported 252Cf electrodeposition source ever produced. Several different chromatographic purification methods were investigated to determine which would be most effective for final purification of themore » feed material used for the CARIBU source. The separation of lanthanides from the Cf was of special concern. Furthermore, the separation, using 145Sm, 153Gd, and 249Cf as tracers, was investigated using BioRad AG 50X8 in α-hydroxyisobutyric acid, Eichrom LN resin in both HNO 3 and HCl, and Eichrom TEVA resin in NH 4SCN. The TEVA NH 4SCN system was found to completely separate 145Sm and 153Gd from 249Cf and was adopted into the purification process used in purifying the 252Cf.« less

Advanced Multilayer Composite Heavy-Oxide Scintillator Detectors for High Efficiency Fast Neutron Detection

NASA Astrophysics Data System (ADS)

Ryzhikov, Vladimir D.; Naydenov, Sergei V.; Pochet, Thierry; Onyshchenko, Gennadiy M.; Piven, Leonid A.; Smith, Craig F.

2018-01-01

We have developed and evaluated a new approach to fast neutron and neutron-gamma detection based on large-area multilayer composite heterogeneous detection media consisting of dispersed granules of small-crystalline scintillators contained in a transparent organic (plastic) matrix. Layers of the composite material are alternated with layers of transparent plastic scintillator material serving as light guides. The resulting detection medium - designated as ZEBRA - serves as both an active neutron converter and a detection scintillator which is designed to detect both neutrons and gamma-quanta. The composite layers of the ZEBRA detector consist of small heavy-oxide scintillators in the form of granules of crystalline BGO, GSO, ZWO, PWO and other materials. We have produced and tested the ZEBRA detector of sizes 100x100x41 mm and greater, and determined that they have very high efficiency of fast neutron detection (up to 49% or greater), comparable to that which can be achieved by large sized heavy-oxide single crystals of about Ø40x80 cm3 volume. We have also studied the sensitivity variation to fast neutron detection by using different types of multilayer ZEBRA detectors of 100 cm2 surface area and 41 mm thickness (with a detector weight of about 1 kg) and found it to be comparable to the sensitivity of a 3He-detector representing a total cross-section of about 2000 cm2 (with a weight of detector, including its plastic moderator, of about 120 kg). The measured count rate in response to a fast neutron source of 252Cf at 2 m for the ZEBRA-GSO detector of size 100x100x41 mm3 was 2.84 cps/ng, and this count rate can be doubled by increasing the detector height (and area) up to 200x100 mm2. In summary, the ZEBRA detectors represent a new type of high efficiency and low cost solid-state neutron detector that can be used for stationary neutron/gamma portals. They may represent an interesting alternative to expensive, bulky gas counters based on 3He or 10B neutron detection technologies.

New fit of thermal neutron constants (TNC) for 233,235U, 239,241Pu and 252Cf(sf): Microscopic vs. maxwellian data

NASA Astrophysics Data System (ADS)

Pronyaev, Vladimir G.; Capote, Roberto; Trkov, Andrej; Noguere, Gilles; Wallner, Anton

2017-09-01

An IAEA project to update the Neutron Standards is near completion. Traditionally, the Thermal Neutron Constants (TNC) evaluated data by Axton for thermal-neutron scattering, capture and fission on four fissile nuclei and the total nu-bar of 252Cf(sf) are used as input in the combined least-square fit with neutron cross section standards. The evaluation by Axton (1986) was based on a least-square fit of both thermal-spectrum averaged cross sections (Maxwellian data) and microscopic cross sections at 2200 m/s. There is a second Axton evaluation based exclusively on measured microscopic cross sections at 2200 m/s (excluding Maxwellian data). Both evaluations disagree within quoted uncertainties for fission and capture cross sections and total multiplicities of uranium isotopes. There are two factors, which may lead to such difference: Westcott g-factors with estimated 0.2% uncertainties used in the Axton's fit, and deviation of the thermal spectra from Maxwellian shape. To exclude or mitigate the impact of these factors, a new combined GMA fit of standards was undertaken with Axton's TNC evaluation based on 2200 m/s data used as a prior. New microscopic data at the thermal point, available since 1986, were added to the combined fit. Additionally, an independent evaluation of TNC was undertaken using CONRAD code. Both GMA and CONRAD results are consistent within quoted uncertainties. New evaluation shows a small increase of fission and capture thermal cross sections, and a corresponding decrease in evaluated thermal nubar for uranium isotopes and 239Pu.

Development of a neutron measurement system in unified non-destructive assay for the PRIDE facility

NASA Astrophysics Data System (ADS)

Seo, Hee; Park, Se-Hwan; Won, Byung-Hee; Ahn, Seong-Kyu; Shin, Hee-Sung; Na, Sang-Ho; Song, Dae-Yong; Kim, Ho-Dong; Lee, Seung Kyu

2013-12-01

The Korea Atomic Energy Research Institute (KAERI) has made an effort to develop pyroprocessing technology to resolve an on-going problem in Korea, i.e., the management of spent nuclear fuels. To this end, a test-bed facility for pyroprocessing, called PRIDE (PyRoprocessing Integrated inactive DEmonstration facility), is being constructed at KAERI. The main objective of PRIDE is to evaluate the performance of the unit processes, remote operation, maintenance, and proliferation resistance. In addition, integrating all unit processes into a one-step process is also one of the main goals. PRIDE can also provide a good opportunity to test safeguards instrumentations for a pyroprocessing facility such as nuclear material accounting devices, surveillance systems, radiation monitoring systems, and process monitoring systems. In the present study, a non-destructive assay (NDA) system for the testing of nuclear material accountancy of PRIDE was designed by integrating three different NDA techniques, i.e., neutron, gamma-ray, and mass measurements. The developed neutron detection module consists of 56 3He tubes and 16 AMPTEK A111 signal processing circuits. The amplifiers were matched in terms of the gain and showed good uniformity after a gain-matching procedure (%RSD=0.37%). The axial and the radial efficiency distributions within the cavity were then measured using a 252Cf neutron source and were compared with the MCNPX calculation results. The measured efficiency distributions showed excellent agreement with the calculations, which confirmed the accuracy of the MCNPX model of the system.

Prompt γ rays and neutrons from fission

NASA Astrophysics Data System (ADS)

Kwan, E.; Wu, C. Y.; Chyzh, A.; Gostic, J.; Henderson, R.; Haight, R. C.; Lee, H. Y.; O'Donnell, J. M.; Perdue, B. A.; Taddeucci, T. N.

2011-10-01

Nuclear data are needed to test the accuracy of calculations from nuclear reaction codes. Information on the prompt γ-ray distributions from fission is sparse and only a handful of published experiments data that measured the prompt γ-ray distribution above incident neutron energies of 1 MeV can be found. In addition, improvement on the accuracy and shape of neutron spectrum from the fission of actinides been requested by the nuclear data community. An investigation on the shapes of the neutron and γ-ray distributions from the spontaneous fission of 252Cf and the neutron-induced fission of 235U was undertaken using the Chi-Nu detector array at the Weapons Neutron Research Facility of the Los Alamos Neutron Science Center. Preliminary results will be presented. This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and the Los Alamos National Laboratory under Contract DE-AC52-06NA25396.

Correlated Production and Analog Transport of Fission Neutrons and Photons using Fission Models FREYA, FIFRELIN and the Monte Carlo Code TRIPOLI-4® .

NASA Astrophysics Data System (ADS)

Verbeke, Jérôme M.; Petit, Odile; Chebboubi, Abdelhazize; Litaize, Olivier

2018-01-01

Fission modeling in general-purpose Monte Carlo transport codes often relies on average nuclear data provided by international evaluation libraries. As such, only average fission multiplicities are available and correlations between fission neutrons and photons are missing. Whereas uncorrelated fission physics is usually sufficient for standard reactor core and radiation shielding calculations, correlated fission secondaries are required for specialized nuclear instrumentation and detector modeling. For coincidence counting detector optimization for instance, precise simulation of fission neutrons and photons that remain correlated in time from birth to detection is essential. New developments were recently integrated into the Monte Carlo transport code TRIPOLI-4 to model fission physics more precisely, the purpose being to access event-by-event fission events from two different fission models: FREYA and FIFRELIN. TRIPOLI-4 simulations can now be performed, either by connecting via an API to the LLNL fission library including FREYA, or by reading external fission event data files produced by FIFRELIN beforehand. These new capabilities enable us to easily compare results from Monte Carlo transport calculations using the two fission models in a nuclear instrumentation application. In the first part of this paper, broad underlying principles of the two fission models are recalled. We then present experimental measurements of neutron angular correlations for 252Cf(sf) and 240Pu(sf). The correlations were measured for several neutron kinetic energy thresholds. In the latter part of the paper, simulation results are compared to experimental data. Spontaneous fissions in 252Cf and 240Pu are modeled by FREYA or FIFRELIN. Emitted neutrons and photons are subsequently transported to an array of scintillators by TRIPOLI-4 in analog mode to preserve their correlations. Angular correlations between fission neutrons obtained independently from these TRIPOLI-4 simulations, using either FREYA or FIFRELIN, are compared to experimental results. For 240Pu(sf), the measured correlations were used to tune the model parameters.

In situ capture gamma-ray analysis of coal in an oversize borehole

USGS Publications Warehouse

Mikesell, J.L.; Dotson, D.W.; Senftle, F.E.; Zych, R.S.; Koger, J.; Goldman, L.

1983-01-01

In situ capture gamma-ray analysis in a coal seam using a high resolution gamma-ray spectrometer in a close-fitting borehole has been reported previously. In order to check the accuracy of the method under adverse conditions, similar measurements were made by means of a small-diameter sonde in an oversize borehole in the Pittsburgh seam, Greene County, Pennsylvania. The hole was 5 times the diameter of the sonde, a ratio that substantially increased the contribution of water (hydrogen) to the total spectral count and reduced the size of the sample measured by the detector. The total natural count, the 40K,count, and the intensities of capture gamma rays from Si, Ca, H, and Al were determined as a function of depth above, through, and below the coal seam. From these logs, the depth and width of the coal seam and its partings were determined. Spectra were accumulated in the seam for 1 h periods by using neutron sources of different strengths. From the spectra obtained by means of several 252Cf neutron sources of different sizes, the ultimate elemental analysis and ash content were determined. The results were not as good as those obtained previously in a close-fitting borehole. However, the results did improve with successively larger source-to-detector distances, i.e.,as the count contribution due to hydrogen in the water decreased. It was concluded that in situ borehole analyses should be made in relatively close-fitting boreholes. ?? 1983.

Methodology for Estimating Thermal and Neutron Embrittlement of Cast Austenitic Stainless Steels During Service in Light Water Reactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chopra, O. K.; Rao, A. S.

2016-04-28

Cast austenitic stainless steel (CASS) materials, which have a duplex structure consisting of austenite and ferrite phases, are susceptible to thermal embrittlement during reactor service. In addition, the prolonged exposure of these materials, which are used in reactor core internals, to neutron irradiation changes their microstructure and microchemistry, and these changes degrade their fracture properties even further. This paper presents a revision of the procedure and correlations presented in NUREG/CR-4513, Rev. 1 (Aug. 1994) for predicting the change in fracture toughness and tensile properties of CASS components due to thermal aging during service in light water reactors (LWRs) at 280–330more » °C (535–625 °F). The methodology is applicable to CF-3, CF-3M, CF-8, and CF-8M materials with a ferrite content of up to 40%. The fracture toughness, tensile strength, and Charpy-impact energy of aged CASS materials are estimated from known material information. Embrittlement is characterized in terms of room-temperature (RT) Charpy-impact energy. The extent or degree of thermal embrittlement at “saturation” (i.e., the minimum impact energy that can be achieved for a material after long-term aging) is determined from the chemical composition of the material. Charpy-impact energy as a function of the time and temperature of reactor service is estimated from the kinetics of thermal embrittlement, which are also determined from the chemical composition. The fracture toughness J-R curve for the aged material is then obtained by correlating RT Charpy-impact energy with fracture toughness parameters. A common “predicted lower-bound” J-R curve for CASS materials of unknown chemical composition is also defined for a given grade of material, range of ferrite content, and temperature. In addition, guidance is provided for evaluating the combined effects of thermal and neutron embrittlement of CASS materials used in the reactor core internal components. The correlations for estimating the change in tensile strength, including the Ramberg/Osgood parameters for strain hardening, are also described.« less

A compact gas-filled avalanche counter for DANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, C. Y.; Chyzh, A.; Kwan, E.

2012-08-04

A compact gas-filled avalanche counter for the detection of fission fragments was developed for a highly segmented 4π γ-ray calorimeter, namely the Detector for Advanced Neutron Capture Experiments located at the Lujan Center of the Los Alamos Neutron Science Center. It has been used successfully for experiments with 235U, 238Pu, 239Pu, and 241Pu isotopes to provide a unique signature to differentiate the fission from the competing neutron-capture reaction channel. We also used it to study the spontaneous fission in 252Cf. The design and performance of this avalanche counter for targets with extreme α-decay rate up to ~2.4×108/s are described.

Working Gas Selection of the Honeycomb Converter-Based Neutron Detector

NASA Astrophysics Data System (ADS)

Fang, Zhujun; Yang, Yigang; Li, Yulan; Wang, Xuewu

2017-07-01

To reduce the manufacturing difficulty and improve the robustness of traditional boron-lined detectors that may replace the 3He counter, the honeycomb neutron converter-based gaseous neutron detector has been proposed. A drift electric field is applied to drive electrons ionized by α or 7Li after the 10B(n, α)7Li reaction from their origination positions to the incident surface of the gas electron multiplier (GEM), which multiplies electrons and forms the neutron signal. As the working gas affects the energy deposition of α or 7Li, the transverse diffusion of electrons in the migration process, as well as the multiplication of electrons in the GEM detector, the working gas selection of the honeycomb converter-based detector would be very important. Fourteen different working gases are investigated in detail through simulation research. Four working gases, Ar:iC4H10:CF4 = 90:7:3, Ar:CO2 = 95:5, Ar:CH4 = 90:10, and Ar:DME = 95:5, are experimentally tested. Both the simulation and experimental results demonstrate that working gases of Ar:iC4H10:CF4 = 90:7:3, Ar:CO2 = 95:5, and Ar:DME = 95:5 show good performances benefitting from both the large stopping powers of α or 7Li and the small transverse diffusion coefficients of electrons. The simulation results indicate that the detection efficiency with one of the three gases is 1.33 to 1.48 times the Ar:CH4 = 90:10, while the experimental results demonstrate that there is 1.34-1.49 times of the detection efficiency. The research in this paper helps improve the performance of the honeycomb converter-based neutron detector.

Setup and Calibration of SLAC's Peripheral Monitoring Stations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooper, C.

2004-09-03

The goals of this project were to troubleshoot, repair, calibrate, and establish documentation regarding SLAC's (Stanford Linear Accelerator Center's) PMS (Peripheral Monitoring Station) system. The PMS system consists of seven PMSs that continuously monitor skyshine (neutron and photon) radiation levels in SLAC's environment. Each PMS consists of a boron trifluoride (BF{sub 3}) neutron detector (model RS-P1-0802-104 or NW-G-20-12) and a Geiger Moeller (GM) gamma ray detector (model TGM N107 or LND 719) together with their respective electronics. Electronics for each detector are housed in Nuclear Instrument Modules (NIMs) and are plugged into a NIM bin in the station. All communicationmore » lines from the stations to the Main Control Center (MCC) were tested prior to troubleshooting. To test communication with MCC, a pulse generator (Systron Donner model 100C) was connected to each channel in the PMS and data at MCC was checked for consistency. If MCC displayed no data, the communication cables to MCC or the CAMAC (Computer Automated Measurement and Control) crates were in need of repair. If MCC did display data, then it was known that the communication lines were intact. All electronics from each station were brought into the lab for troubleshooting. Troubleshooting usually consisted of connecting an oscilloscope or scaler (Ortec model 871 or 775) at different points in the circuit of each detector to record simulated pulses produced by a pulse generator; the input and output pulses were compared to establish the location of any problems in the circuit. Once any problems were isolated, repairs were done accordingly. The detectors and electronics were then calibrated in the field using radioactive sources. Calibration is a process that determines the response of the detector. Detector response is defined as the ratio of the number of counts per minute interpreted by the detector to the amount of dose equivalent rate (in mrem per hour, either calculated or measured). Detector response for both detectors is dependent upon the energy of the incident radiation; this trend had to be accounted for in the calibration of the BF{sub 3} detector. Energy dependence did not have to be taken into consideration when calibrating the GM detectors since GM detector response is only dependent on radiation energy below 100 keV; SLAC only produces a spectrum of gamma radiation above 100 keV. For the GM detector, calibration consisted of bringing a {sup 137}Cs source and a NIST-calibrated RADCAL Radiation Monitor Controller (model 9010) out to the field; the absolute dose rate was determined by the RADCAL device while simultaneously irradiating the GM detector to obtain a scaler reading corresponding to counts per minute. Detector response was then calculated. Calibration of the BF{sub 3} detector was done using NIST certified neutron sources of known emission rates and energies. Five neutron sources ({sup 238}PuBe, {sup 238}PuB, {sup 238}PuF4, {sup 238}PuLi and {sup 252}Cf) with different energies were used to account for the energy dependence of the response. The actual neutron dose rate was calculated by date-correcting NIST source data and considering the direct dose rate and scattered dose rate. Once the total dose rate (sum of the direct and scattered dose rates) was known, the response vs. energy curve was plotted. The first station calibrated (PMS6) was calibrated with these five neutron sources; all subsequent stations were calibrated with one neutron source and the energy dependence was assumed to be the same.« less

TUNABLE IRRADIATION TESTBED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wootan, David W.; Casella, Andrew M.; Asner, David M.

PNNL has developed and continues to develop innovative methods for characterizing irradiated materials from nuclear reactors and particle accelerators for various clients and collaborators around the world. The continued development of these methods, in addition to the ability to perform unique scientific investigations of the effects of radiation on materials could be greatly enhanced with easy access to irradiation facilities. A Tunable Irradiation Testbed with customized targets (a 30 MeV, 1mA cyclotron or similar coupled to a unique target system) is shown to provide a much more flexible and cost-effective source of irradiating particles than a test reactor or isotopicmore » source. The configuration investigated was a single shielded building with multiple beam lines from a small, flexible, high flux irradiation source. Potential applications investigated were the characterization of radiation damage to materials applicable to advanced reactors, fusion reactor, legacy waste, (via neutron spectra tailored to HTGR, molten salt, LWR, LMR, fusion environments); 252Cf replacement; characterization of radiation damage to materials of interest to High Energy Physics to enable the neutrino program; and research into production of short lived isotopes for potential medical and other applications.« less

Collective Band Structures in the Neutron-Rich 107,109Ru Nuclei

NASA Astrophysics Data System (ADS)

Zhu, Sheng-jiang; Gan, Cui-yun; J, Hamilton H.; A, Ramayya V.; B, Babu R. S.; M, Sakhaee; W, Ma C.; Long, Gui-lu; Deng, Jing-kang; Zhu, Ling-yan; Li, Ming; Yang, Li-ming; J, Komicki; J, Cole D.; R, Aryaeinejad; Y, Dardenne K.; M, Drigert W.; J, Rasmussen O.; M, Stoyer A.; S, Chu Y.; K, Gregorich E.; M, Mohar F.; S, Prussin G.; I, Lee Y.; N, Johnson R.; F, McGowan K.

1998-11-01

The levels in neutron-rich odd-A 107,109Ru nuclei have been investigated by using γ-γ- and γ-γ-γ-coincidence studies of the prompt γ-rays from the spontaneous fission of 252Cf. The ground state bands and the negative parity bands are identified and expanded in both nuclei. Triaxial rotor plus particle model calculations indicate the ground state bands originate from ν(d5/2 + g7/2) quasiparticle configurations and the negative parity bands are from νh11/2 orbital.

A sensitive, selective, and portable detector for contraband: The compact integrated narcotics detection instrument

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tuemer, T.O.; Doan, L.; Su, C.W.

2000-07-01

A Compact Integrated Narcotics Detection Instrument (CINDI) has been developed at NOVA R and D, Inc., in cooperation with the US Coast Guard. This detector utilizes neutrons emitted from {sup 252}Cf. Neutrons emitted from the front face of CINDI penetrate dense compartment barrier materials with little change in energy but are backscattered by hydrogen-rich materials such as drugs. The backscattered neutrons are detected, and the rate is displayed by a microprocessor-controller integrated into CINDI. The operator guides the detector along a suspected area and receives immediate feedback from the state-of-the-art electronics. For user safety, the device incorporates a highly sensitivemore » detection scheme to permit the use of a very weak radioactive source, without compromising detectability. CINDI is capable of detecting narcotics effectively behind panels made of steel, wood, fiberglass, or even lead-lined materials. This makes it useful for inspecting marine vessels, ship bulkheads, automobiles, structure walls, or small sealed containers. Figure 2 shows three views of the CINDI instrument. CINDI responds strongly to hydrogen-rich materials such as narcotics. It has been tested at NOVA, the US Coast Guard, and Brewt Power Systems. The results of the tests show excellent response and specificity to narcotics. CINDI has led to a new technology that shows promise for identifying the concealed contraband. The new technique uses a fusion of two independent but complementary signals for detecting and possibly identifying concealed drugs in a variety of carriers such as vehicles, marine vessels, airplanes, containers, cargo, and luggage. The carriers will be scanned using both neutron and gamma-ray sources. The signal from both the neutron and gamma-ray backscattering and/or transmission can be used simultaneously to detect and possibly identify the contrabands it has been trained for. A system that can produce three-dimensional images for both signals may also be developed. The two images may be combined and analyzed by a fast host computer to detect concealed contraband. The two independent signatures when analyzed simultaneously may help determine the type of concealed contraband.« less

Experimental evaluation of the extended Dytlewski-style dead time correction formalism for neutron multiplicity counting

NASA Astrophysics Data System (ADS)

Lockhart, M.; Henzlova, D.; Croft, S.; Cutler, T.; Favalli, A.; McGahee, Ch.; Parker, R.

2018-01-01

Over the past few decades, neutron multiplicity counting has played an integral role in Special Nuclear Material (SNM) characterization pertaining to nuclear safeguards. Current neutron multiplicity analysis techniques use singles, doubles, and triples count rates because a methodology to extract and dead time correct higher order count rates (i.e. quads and pents) was not fully developed. This limitation is overcome by the recent extension of a popular dead time correction method developed by Dytlewski. This extended dead time correction algorithm, named Dytlewski-Croft-Favalli(DCF), is detailed in reference Croft and Favalli (2017), which gives an extensive explanation of the theory and implications of this new development. Dead time corrected results can then be used to assay SNM by inverting a set of extended point model equations which as well have only recently been formulated. The current paper discusses and presents the experimental evaluation of practical feasibility of the DCF dead time correction algorithm to demonstrate its performance and applicability in nuclear safeguards applications. In order to test the validity and effectiveness of the dead time correction for quads and pents, 252Cf and SNM sources were measured in high efficiency neutron multiplicity counters at the Los Alamos National Laboratory (LANL) and the count rates were extracted up to the fifth order and corrected for dead time. In order to assess the DCF dead time correction, the corrected data is compared to traditional dead time correction treatment within INCC. The DCF dead time correction is found to provide adequate dead time treatment for broad range of count rates available in practical applications.

Characterization of silicon carbide and diamond detectors for neutron applications

NASA Astrophysics Data System (ADS)

Hodgson, M.; Lohstroh, A.; Sellin, P.; Thomas, D.

2017-10-01

The presence of carbon atoms in silicon carbide and diamond makes these materials ideal candidates for direct fast neutron detectors. Furthermore the low atomic number, strong covalent bonds, high displacement energies, wide bandgap and low intrinsic carrier concentrations make these semiconductor detectors potentially suitable for applications where rugged, high-temperature, low-gamma-sensitivity detectors are required, such as active interrogation, electronic personal neutron dosimetry and harsh environment detectors. A thorough direct performance comparison of the detection capabilities of semi-insulating silicon carbide (SiC-SI), single crystal diamond (D-SC), polycrystalline diamond (D-PC) and a self-biased epitaxial silicon carbide (SiC-EP) detector has been conducted and benchmarked against a commercial silicon PIN (Si-PIN) diode, in a wide range of alpha (Am-241), beta (Sr/Y-90), ionizing photon (65 keV to 1332 keV) and neutron radiation fields (including 1.2 MeV to 16.5 MeV mono-energetic neutrons, as well as neutrons from AmBe and Cf-252 sources). All detectors were shown to be able to directly detect and distinguish both the different radiation types and energies by using a simple energy threshold discrimination method. The SiC devices demonstrated the best neutron energy discrimination ratio (E\\max (n=5 MeV)/E\\max (n=1 MeV)  ≈5), whereas a superior neutron/photon cross-sensitivity ratio was observed in the D-PC detector (E\\max (AmBe)/E\\max (Co-60)  ≈16). Further work also demonstrated that the cross-sensitivity ratios can be improved through use of a simple proton-recoil conversion layer. Stability issues were also observed in the D-SC, D-PC and SiC-SI detectors while under irradiation, namely a change of energy peak position and/or count rate with time (often referred to as the polarization effect). This phenomenon within the detectors was non-debilitating over the time period tested (> 5 h) and, as such, stable operation was possible. Furthermore, the D-SC, self-biased SiC-EP and semi-insulating SiC detectors were shown to operate over the temperature range -60 °C to +100 °C.

Large-Area, Low-Cost, High-Efficiency Neutron Detector for Vehicle-Mounted Operation

NASA Astrophysics Data System (ADS)

Lacy, Jeffrey L.; Martin, Christopher S.; Athanasiades, Athanasios; Regmi, Murari; Vazquez-Flores, Gerson J.; Davenport, Stephen; King, Nicholas S.; Lyons, Tom

2017-07-01

We have developed a large-area, low-cost, high-efficiency neutron detector for vehicle-mounted operation. The detector, which has overall dimensions 12.7 cm x 91.4 cm x 102 cm (5”x36”x40”), a sensitive area equal to 0.85 m2 (1320 in2), and weight of 110 kg (242 lbs), employs an array of 90 boron-coated straw (BCS) detectors. PTI has also developed electronics to minimize cost and space while providing low-noise signal conditioning for both neutron and gamma detection channels, as well as low energy Bluetooth communication with handheld devices. Extremely low power consumption allows continuous use for 225 hours (-.10 days) using three AAA lithium-ion rechargeable batteries. We present radiological, mechanical, and environmental tests, collected from four full-scale prototypes. Outdoor neutron-counting tests with a moderated 252Cf source 2 m away from the center of the detector face showed an average detection rate of 5.5 cps/ng with a standard deviation of 0.09 cps/ng over the four individual detector measurements. Measurements showed a gamma rejection ratio of 1.0 x 10-8, and gamma absolute rejection ratio (GARRn) of 0.93. The prototypes were also operated successfully onboard a moving vehicle for high-speed tests and a long-range 1433-mile, two-day road trip from Houston, TX, USA, to Laurel, MD, USA. Using auxiliary DARPA SIGMA equipment, the GPS, timestamp, gamma and neutron data were transmitted over the cellular network with 10 Hz resolution to a server and real-time tracking website. Mechanical impact and electrostatic discharge testing produced no spurious counts in either the neutron or gamma channels. Ambient environmental temperature testing showed less than ±1% response variation over the range from -30°C to +55°C.

Multi-particle inspection using associated particle sources

DOEpatents

Bingham, Philip R.; Mihalczo, John T.; Mullens, James A.; McConchie, Seth M.; Hausladen, Paul A.

2016-02-16

Disclosed herein are representative embodiments of methods, apparatus, and systems for performing combined neutron and gamma ray radiography. For example, one exemplary system comprises: a neutron source; a set of alpha particle detectors configured to detect alpha particles associated with neutrons generated by the neutron source; neutron detectors positioned to detect at least some of the neutrons generated by the neutron source; a gamma ray source; a set of verification gamma ray detectors configured to detect verification gamma rays associated with gamma rays generated by the gamma ray source; a set of gamma ray detectors configured to detect gamma rays generated by the gamma ray source; and an interrogation region located between the neutron source, the gamma ray source, the neutron detectors, and the gamma ray detectors.

High intensity, pulsed thermal neutron source

DOEpatents

Carpenter, J.M.

1973-12-11

This invention relates to a high intensity, pulsed thermal neutron source comprising a neutron-producing source which emits pulses of fast neutrons, a moderator block adjacent to the last neutron source, a reflector block which encases the fast neutron source and the moderator block and has a thermal neutron exit port extending therethrough from the moderator block, and a neutron energy- dependent decoupling reflector liner covering the interior surfaces of the thermal neutron exit port and surrounding all surfaces of the moderator block except the surface viewed by the thermal neutron exit port. (Official Gazette)

Real-Time, Fast Neutron Coincidence Assay of Plutonium With a 4-Channel Multiplexed Analyzer and Organic Scintillators

NASA Astrophysics Data System (ADS)

Joyce, Malcolm J.; Gamage, Kelum A. A.; Aspinall, M. D.; Cave, F. D.; Lavietes, A.

2014-06-01

The design, principle of operation and the results of measurements made with a four-channel organic scintillator system are described. The system comprises four detectors and a multiplexed analyzer for the real-time parallel processing of fast neutron events. The function of the real-time, digital multiple-channel pulse-shape discrimination analyzer is described together with the results of laboratory-based measurements with 252Cf, 241Am-Li and plutonium. The analyzer is based on a single-board solution with integrated high-voltage supplies and graphical user interface. It has been developed to meet the requirements of nuclear materials assay of relevance to safeguards and security. Data are presented for the real-time coincidence assay of plutonium in terms of doubles count rate versus mass. This includes an assessment of the limiting mass uncertainty for coincidence assay based on a 100 s measurement period and samples in the range 0-50 g. Measurements of count rate versus order of multiplicity for 252Cf and 241Am-Li and combinations of both are also presented.

Thermal neutron detection system

DOEpatents

Peurrung, Anthony J.; Stromswold, David C.

2000-01-01

According to the present invention, a system for measuring a thermal neutron emission from a neutron source, has a reflector/moderator proximate the neutron source that reflects and moderates neutrons from the neutron source. The reflector/moderator further directs thermal neutrons toward an unmoderated thermal neutron detector.

Cs2LiLa(Br,Cl)6 Crystals for Nuclear Security Applications

NASA Astrophysics Data System (ADS)

Hawrami, R.; Pandian, L. Soundara; Ariesanti, E.; Glodo, J.; Finkelstein, J.; Tower, J.; Shah, K.

2016-04-01

Properties of dual-mode scintillation detectors based on CLLBC crystals are reported. Energy resolution and light yield are measured at 2.9% (FWHM) at 662 keV and 45000 photons/MeV, respectively, for a 1-in-diameter and 1-in-long crystal. With less than 2% variation in light yield as a function of energy, CLLBC has better proportionality than LaBr3 and NaI:Tl. Neutron peak resulting from reactions with neutrons emitted by 252Cf (moderated) is measured at a gamma energy equivalent of 3.1 MeVee (electron energy equivalent), making pulse height discrimination between gamma-rays and neutrons easy. The material is also of effective pulse shape discrimination. The figure-of-merit for discrimination of gamma rays and thermal neutrons in CLLBC can be as high as 3.2, which is comparable to that of CLYC.

Fissile solution measurement apparatus

DOEpatents

Crane, T.W.; Collinsworth, P.R.

1984-06-11

An apparatus for determining the content of a fissile material within a solution by detecting delayed fission neutrons emitted by the fissile material after it is temporarily irradiated by a neutron source. The apparatus comprises a container holding the solution and having a portion defining a neutron source cavity centrally disposed within the container. The neutron source cavity temporarily receives the neutron source. The container has portions defining a plurality of neutron detector ports that form an annular pattern and surround the neutron source cavity. A plurality of neutron detectors count delayed fission neutrons emitted by the fissile material. Each neutron detector is located in a separate one of the neutron detector ports.

ESR1 and PIK3CA mutational status in serum and plasma from metastatic breast cancer patients: A comparative study.

PubMed

Takeshita, Takashi; Yamamoto, Yutaka; Yamamoto-Ibusuki, Mutsuko; Tomiguchi, Mai; Sueta, Aiko; Iwase, Hirotaka

2018-04-07

Plasma and serum cell-free DNA (cfDNA) are useful sources of tumor DNA, but comparative investigations of the tumor mutational status between them are rare. we performed droplet digital PCR assay for representative hotspot mutations in metastatic breast cancer (MBC) (ESR1 and PIK3CA) in serum and plasma cfDNA concurrently extracted from the blood of 33 estrogen receptor-positive MBC patients. ESR1 mutations in plasma cfDNA were found in 7 of the 33 patients; ESR1 mutations in serum cfDNA were detected in only one out of 7 patients with ESR1 mutations in plasma cfDNA. PIK3CA exon 9 and exon 20 mutations in plasma cfDNA were found in 3 and 7 out of the 33 patients, respectively; PIK3CA exon 9 mutations in serum cfDNA were detected in 2 out of 3 patients with PIK3CA exon 9 mutations in plasma cfDNA; PIK3CA exon 20 mutations in serum cfDNA were detected in 2 out of 7 patients with PIK3CA exon 20 mutations in plasma cfDNA. Here we show the higher frequency of ESR1 and PIK3CA mutations in the plasma than in the serum in 33 MBC patients; therefore, serum samples should not be considered the preferred source of cfDNA.

In situ CF3 Detection in Low Pressure Inductive Discharges by Fourier Transform Infrared Spectroscopy

NASA Technical Reports Server (NTRS)

Kim, J. S.; Cappelli, M. A.; Sharma, S. P.; Arnold, J. O. (Technical Monitor)

1998-01-01

The detection of CF(x) (x=1-3) radicals in low pressure discharges using source gases such as CF4 and CHF3 is of importance to the understanding of their chemical structure and relevance in plasma based etching processes. These radicals are known to contribute to the formation of fluorocarbon polymer films, which affect the selectivity and anisotropy of etching. In this study, we present preliminary results of the quantitative measurement of trifluoromethyl radicals, CF3, in low pressure discharges. The discharge studied here is an inductively (transformer) coupled plasma (ICP) source in the GEC reference cell, operating on pure CF4 at pressures ranging from 10 - 100 mTorr, This plasma source generates higher electron number densities at lower operating pressures than obtainable with the parallel-plate capacitively coupled version of the GEC reference cell. Also, this expanded operating regime is more relevant to new generations of industrial plasma reactors being used by the microelectronics industry. Fourier transform infrared (FTIR) spectroscopy is employed to observe the absorption band of CF3 radicals in the electronic ground state X2Al in the region of 1233-1270/cm. The spectrometer is equipped with a high sensitivity HgCdTe (MCT) detector and has a fixed resolution of 0.125/cm. The CF3 concentrations are measured for a range of operating pressures and discharge power levels.

Astrophysical reaction rate for α(αn,γ)9Be by photodisintegration

NASA Astrophysics Data System (ADS)

Sumiyoshi, K.; Utsunomiya, H.; Goko, S.; Kajino, T.

2002-10-01

We study the astrophysical reaction rate for the formation of 9Be through the three body reaction α(αn,γ). This reaction is one of the key reactions which could bridge the mass gap at A=8 nuclear systems to produce intermediate-to-heavy mass elements in alpha- and neutron-rich environments such as r-process nucleosynthesis in supernova explosions, s-process nucleosynthesis in asymptotic giant branch (AGB) stars, and primordial nucleosynthesis in baryon inhomogeneous cosmological models. To calculate the thermonuclear reaction rate in a wide range of temperatures, we numerically integrate the thermal average of cross sections assuming a two-steps formation through a metastable 8Be, α+α⇌8Be(n,γ)9Be. Off-resonant and on-resonant contributions from the ground state in 8Be are taken into account. As input cross section, we adopt the latest experimental data by photodisintegration of 9Be with laser-electron photon beams, which covers all relevant resonances in 9Be. Experimental data near the neutron threshold are added with γ-ray flux corrections and a new least-squares analysis is made to deduce resonance parameters in the Breit-Wigner formulation. Based on the photodisintegration cross section, we provide the reaction rate for α(αn,γ)9Be in the temperature range from T9=10-3 to T9=101 (T9 is the temperature in units of 109 K) both in the tabular form and in the analytical form for potential usage in nuclear reaction network calculations. The calculated reaction rate is compared with the reaction rates of the CF88 and the NACRE compilations. The CF88 rate, which is based on the photoneutron cross section for the 1/2+ state in 9Be by Berman et al., is valid at T9>0.028 due to lack of the off-resonant contribution. The CF88 rate differs from the present rate by a factor of two in a temperature range T9⩾0.1. The NACRE rate, which adopted different sources of experimental information on resonance states in 9Be, is 4-12 times larger than the present rate at T9⩽0.028, but is consistent with the present rate to within ±20% at T9⩾0.1.

Measurements of the thermal neutron flux for an accelerator-based photoneutron source.

PubMed

Taheri, Ali; Pazirandeh, Ali

2016-12-01

To have access to an appropriate neutron source is one of the most demanding requirements for neutron studies. This is important specially in laboratory and clinical applications, which need more compact and accessible sources. The most known neutron sources are fission reactors and natural isotopes, but there is an increasing interest for using accelerator based neutron sources because of their advantages. In this paper, we shall present a photo-neutron source prototype which is designed and fabricated to be used for different neutron researches including in-laboratory neutron activation analysis and neutron imaging, and also preliminary studies in boron neutron capture therapy (BNCT). Series of experimental tests were conducted to examine the intensity and quality of the neutron field produced by this source. Monte-Carlo simulations were also utilized to provide more detailed evaluation of the neutron spectrum, and determine the accuracy of the experiments. The experiments demonstrated a thermal neutron flux in the order of 10 7 (n/cm 2 .s), while simulations affirmed this flux and showed a neutron spectrum with a sharp peak at thermal energy region. According to the results, about 60 % of produced neutrons are in the range of thermal to epithermal neutrons.

Neutron-multiplicity experiments for enhanced fission modelling

NASA Astrophysics Data System (ADS)

Al-Adili, Ali; Tarrío, Diego; Hambsch, Franz-Josef; Göök, Alf; Jansson, Kaj; Solders, Andreas; Rakapoulos, Vasileios; Gustavsson, Cecilia; Lantz, Mattias; Mattera, Andrea; Oberstedt, Stephan; Prokofiev, Alexander V.; Sundén, Erik A.; Vidali, Marzio; Österlund, Michael; Pomp, Stephan

2017-09-01

The nuclear de-excitation process of fission fragments (FF) provides fundamental information for the understanding of nuclear fission and nuclear structure in neutron-rich isotopes. The variation of the prompt-neutron multiplicity, ν(A), as a function of the incident neutron energy (En) is one of many open questions. It leads to significantly different treatments in various fission models and implies that experimental data are analyzed based on contradicting assumptions. One critical question is whether the additional excitation energy (Eexc) is manifested through an increase of ν(A) for all fragments or for the heavy ones only. A systematic investigation of ν(A) as a function of En has been initiated. Correlations between prompt-fission neutrons and fission fragments are obtained by using liquid scintillators in conjunction with a Frisch-grid ionization chamber. The proof-of-principle has been achieved on the reaction 235U(nth,f) at the Van De Graff (VdG) accelerator of the JRC-Geel using a fully digital data acquisition system. Neutrons from 252Cf(sf) were measured separately to quantify the neutron-scattering component due to surrounding shielding material and to determine the intrinsic detector efficiency. Prelimenary results on ν(A) and spectrum in correlation with FF properties are presented.

The Case of the Neutron Star With a Wayward Wake

NASA Astrophysics Data System (ADS)

2006-06-01

A long observation with NASA's Chandra X-ray Observatory has revealed important new details of a neutron star that is spewing out a wake of high-energy particles as it races through space. The deduced location of the neutron star on the edge of a supernova remnant, and the peculiar orientation of the neutron star wake, pose mysteries that remain unresolved. "Like a kite flying in the wind, the behavior of this neutron star and its wake tell us what sort of gas it must be plowing through," said Bryan Gaensler of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., and lead author of a paper accepted to The Astrophysical Journal. "Yet we're still not sure how the neutron star got to its present location." Animation: Sequence of images of J0617 in IC 443 Animation: Sequence of images of J0617 in IC 443 The neutron star, known as CXOU J061705.3+222127, or J0617 for short, appears to lie near the outer edge of an expanding bubble of hot gas associated with the supernova remnant IC 443. Presumably, J0617 was created at the time of the supernova -- approximately 30,000 years ago -- and propelled away from the site of the explosion at about 500,000 miles per hour. However, the neutron star's wake is oriented almost perpendicularly to the direction expected if the neutron star were moving away from the center of the supernova remnant. This apparent misalignment had previously raised doubts about the association of the speeding neutron star with the supernova remnant. Gaensler and his colleagues provide strong evidence that J0617 was indeed born in the same explosion that created the supernova remnant. First, the shape of the neutron star's wake indicates it is moving a little faster than the speed of sound in Composite Images of SNR IC 443 Composite Images of SNR IC 443 the remnant's multimillion-degree gas. The velocity that one can then calculate from this conclusion closely matches the predicted pace of the neutron star. In contrast, if the neutron star were outside the confines of the remnant, its inferred speed would be a sluggish 20,000 miles per hour. Also, the measured temperature of the neutron star matches that of one born at the same time of the supernova remnant. What then, could cause the misaligned, or wayward, neutron star wake? The authors speculate that perhaps the doomed progenitor star was moving at a high speed before it exploded, so that the explosion site was not at the observed center of the supernova remnant. Fast moving gusts of gas inside the supernova remnant have further pushed the neutron star's wake out of alignment. Observations of J0617 in the next 10 years should put this idea to the test. "If the neutron star was born off-center and if the wake is being pushed around by cross-winds, the neutron star should be moving close to vertically, away from the center of the supernova remnant. Now we wait and see," said Gaensler. Chandra X-ray Image of J0617 in IC 443 Chandra X-ray Image of J0617 in IC 443 Another group, led by Margarita Karovska, also of the CfA, has concentrated on other, previously unnoticed intriguing features of J0617. At a recent conference on neutron stars in London, England, they announced their findings, which include a thin filament of cooler gas that appears to extend from the neutron star along the long axis of its wake, and a second point-like feature embedded in the X-ray nebula around the neutron star. "There are a number of puzzling observational features associated with this system crying out for longer observations," said Karovska. Other members of the Gaensler team were S. Chatterjee and P. O. Slane (CfA), E. van der Swaluw (Royal Netherlands Meteorological Institute), F. Camilo (Columbia University), and J. P. Hughes (Rutgers University). Karovska's team included T. Clarke (Naval Research Laboratory), G. Pavlov (Penn State University), and M.C. Weisskopf and V. Zavlin of the Marshall Space Flight Center, Huntsville, Ala. which also manages the Chandra program for NASA's Science Mission Directorate. The Smithsonian Astrophysical Observatory provides science support and controls flight operations from the Chandra X-ray Center in Cambridge, Mass. Additional information and images can be found at: http://chandra.harvard.edu and http://chandra.nasa.gov For information about NASA and agency programs on the Web, visit: http://www.nasa.gov

Experimental evaluation of the extended Dytlewski-style dead time correction formalism for neutron multiplicity counting

DOE PAGES

Lockhart, M.; Henzlova, D.; Croft, S.; ...

2017-09-20

Over the past few decades, neutron multiplicity counting has played an integral role in Special Nuclear Material (SNM) characterization pertaining to nuclear safeguards. Current neutron multiplicity analysis techniques use singles, doubles, and triples count rates because a methodology to extract and dead time correct higher order count rates (i.e. quads and pents) was not fully developed. This limitation is overcome by the recent extension of a popular dead time correction method developed by Dytlewski. This extended dead time correction algorithm, named Dytlewski-Croft-Favalli (DCF), is detailed in reference Croft and Favalli (2017), which gives an extensive explanation of the theory andmore » implications of this new development. Dead time corrected results can then be used to assay SNM by inverting a set of extended point model equations which as well have only recently been formulated. Here, we discuss and present the experimental evaluation of practical feasibility of the DCF dead time correction algorithm to demonstrate its performance and applicability in nuclear safeguards applications. In order to test the validity and effectiveness of the dead time correction for quads and pents, 252Cf and SNM sources were measured in high efficiency neutron multiplicity counters at the Los Alamos National Laboratory (LANL) and the count rates were extracted up to the fifth order and corrected for dead time. To assess the DCF dead time correction, the corrected data is compared to traditional dead time correction treatment within INCC. In conclusion, the DCF dead time correction is found to provide adequate dead time treatment for broad range of count rates available in practical applications.« less

New perspectives for undoped CaF2 scintillator as a threshold activation neutron detector

NASA Astrophysics Data System (ADS)

Sibczynski, Pawel; Dziedzic, Andrzej; Grodzicki, Krystian; Iwanowska-Hanke, Joanna; Moszyński, Marek; Swiderski, Lukasz; Syntfeld-Każuch, Agnieszka; Wolski, Dariusz; Carrel, Frédérick; Grabowski, Amélie; Hamel, Matthieu; Laine, Frederic; Sari, Adrien; Iovene, Alessandro; Tintori, Carlo; Fontana, Cristiano; Pino, Felix

2018-01-01

In this paper we present the prompt photofission neutron detection performance of undoped CaF2 scintillator using Threshold Activation Detection (TAD). The study is carried out in the frame of C-BORD Horizon 2020 project, during which an efficient toolbox for high volume freight non-intrusive inspection (NII) is under development. Technologies for radiation monitoring are the part of the project. Particularly, detection of various radiological threats on country borders plays an important significant role in Homeland Security applications. Detection of illegal transfer of Special Nuclear Material (SNM) - 235U, 233U and 239Pu - is particular due to the potential use for production of nuclear weapon as well as radiological dispersal device (RDD) V known also as a "dirty bomb". This technique relies on activation of 19F nuclei in the scintillator medium by fast neutrons and registration of high-energy β particles and γ-rays from the decay of reaction products. The radiation from SNM is detected after irradiation in order to avoid detector blinding. Despite the low 19F(n,α)16N or 19F(n,p)19O reaction cross-section, the method could be a good solution for detection of shielded nuclear material. Results obtained with the CaF2 detector were compared with the previous study done for BaF2 and 3He detector. These experimental results were obtained using 252Cf source and 9 MeV Varian Linatron M9 linear accelerator (LINAC). Finally, performance of the prompt neutron detection system based on CaF2 will be validated at Rotterdam Seaport during field trails in 2018.

Experimental evaluation of the extended Dytlewski-style dead time correction formalism for neutron multiplicity counting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lockhart, M.; Henzlova, D.; Croft, S.

Over the past few decades, neutron multiplicity counting has played an integral role in Special Nuclear Material (SNM) characterization pertaining to nuclear safeguards. Current neutron multiplicity analysis techniques use singles, doubles, and triples count rates because a methodology to extract and dead time correct higher order count rates (i.e. quads and pents) was not fully developed. This limitation is overcome by the recent extension of a popular dead time correction method developed by Dytlewski. This extended dead time correction algorithm, named Dytlewski-Croft-Favalli (DCF), is detailed in reference Croft and Favalli (2017), which gives an extensive explanation of the theory andmore » implications of this new development. Dead time corrected results can then be used to assay SNM by inverting a set of extended point model equations which as well have only recently been formulated. Here, we discuss and present the experimental evaluation of practical feasibility of the DCF dead time correction algorithm to demonstrate its performance and applicability in nuclear safeguards applications. In order to test the validity and effectiveness of the dead time correction for quads and pents, 252Cf and SNM sources were measured in high efficiency neutron multiplicity counters at the Los Alamos National Laboratory (LANL) and the count rates were extracted up to the fifth order and corrected for dead time. To assess the DCF dead time correction, the corrected data is compared to traditional dead time correction treatment within INCC. In conclusion, the DCF dead time correction is found to provide adequate dead time treatment for broad range of count rates available in practical applications.« less

Historical review of californium-252 discovery and development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoddard, D.H.

1985-01-01

This paper discusses the discovery and history of californium 252. This isotope may be synthesized by irradiating plutonium 239, plutonium 242, americium 243, or curium 244 with neutrons in a nuclear reactor. Various experiments and inventions involving /sup 252/Cf conducted at the Savannah River Plant are discussed. The evolution of radiotherapy using californium 252 is reviewed. (PLG)

Historical Review of Californium-252 Discovery and Development

DOE R&D Accomplishments Database

Stoddard, D. H.

1985-01-01

This paper discusses the discovery and history of californium 252. This isotope may be synthesized by irradiating plutonium 239, plutonium 242, americium 243, or curium 244 with neutrons in a nuclear reactor. Various experiments and inventions involving Cf conducted at the Savannah River Plant are discussed. The evolution of radiotherapy using californium 252 is reviewed. (PLG)

Nuclear Resonance Fluorescence to Measure Plutonium Mass in Spent Nuclear Fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ludewigt, Bernhard A; Quiter, Brian J.; Ambers, Scott D.

2011-01-14

The Next Generation Safeguard Initiative (NGSI) of the U.S Department of Energy is supporting a multi-lab/university collaboration to quantify the plutonium (Pu) mass in spent nuclear fuel (SNF) assemblies and to detect the diversion of pins with non-destructive assay (NDA) methods. The following 14 NDA techniques are being studied: Delayed Neutrons, Differential Die-Away, Differential Die-Away Self-Interrogation, Lead Slowing Down Spectrometer, Neutron Multiplicity, Passive Neutron Albedo Reactivity, Total Neutron (Gross Neutron), X-Ray Fluorescence, {sup 252}Cf Interrogation with Prompt Neutron Detection, Delayed Gamma, Nuclear Resonance Fluorescence, Passive Prompt Gamma, Self-integration Neutron Resonance Densitometry, and Neutron Resonance Transmission Analysis. Understanding and maturity ofmore » the techniques vary greatly, ranging from decades old, well-understood methods to new approaches. Nuclear Resonance Fluorescence (NRF) is a technique that had not previously been studied for SNF assay or similar applications. Since NRF generates isotope-specific signals, the promise and appeal of the technique lies in its potential to directly measure the amount of a specific isotope in an SNF assay target. The objectives of this study were to design and model suitable NRF measurement methods, to quantify capabilities and corresponding instrumentation requirements, and to evaluate prospects and the potential of NRF for SNF assay. The main challenge of the technique is to achieve the sensitivity and precision, i.e., to accumulate sufficient counting statistics, required for quantifying the mass of Pu isotopes in SNF assemblies. Systematic errors, considered a lesser problem for a direct measurement and only briefly discussed in this report, need to be evaluated for specific instrument designs in the future. Also, since the technical capability of using NRF to measure Pu in SNF has not been established, this report does not directly address issues such as cost, size, development time, nor concerns related to the use of Pu in measurement systems. This report discusses basic NRF measurement concepts, i.e., backscatter and transmission methods, and photon source and {gamma}-ray detector options in Section 2. An analytical model for calculating NRF signal strengths is presented in Section 3 together with enhancements to the MCNPX code and descriptions of modeling techniques that were drawn upon in the following sections. Making extensive use of the model and MCNPX simulations, the capabilities of the backscatter and transmission methods based on bremsstrahlung or quasi-monoenergetic photon sources were analyzed as described in Sections 4 and 5. A recent transmission experiment is reported on in Appendix A. While this experiment was not directly part of this project, its results provide an important reference point for our analytical estimates and MCNPX simulations. Used fuel radioactivity calculations, the enhancements to the MCNPX code, and details of the MCNPX simulations are documented in the other appendices.« less

Active Neutron-Based Interrogation System with D-D Neutron Source for Detection of Special Nuclear Materials

NASA Astrophysics Data System (ADS)

Takahashi, Y.; Misawa, T.; Yagi, T.; Pyeon, C. H.; Kimura, M.; Masuda, K.; Ohgaki, H.

2015-10-01

The detection of special nuclear materials (SNM) is an important issue for nuclear security. The interrogation systems used in a sea port and an airport are developed in the world. The active neutron-based interrogation system is the one of the candidates. We are developing the active neutron-based interrogation system with a D-D fusion neutron source for the nuclear security application. The D-D neutron source is a compact discharge-type fusion neutron source called IEC (Inertial-Electrostatic Confinement fusion) device which provides 2.45 MeV neutrons. The nuclear materials emit the highenergy neutrons by fission reaction. High-energy neutrons with energies over 2.45 MeV amount to 30% of all the fission neutrons. By using the D-D neutron source, the detection of SNMs is considered to be possible with the attention of fast neutrons if there is over 2.45 MeV. Ideally, neutrons at En>2.45 MeV do not exist if there is no nuclear materials. The detection of fission neutrons over 2.45 MeV are hopeful prospect for the detection of SNM with a high S/N ratio. In the future, the experiments combined with nuclear materials and a D-D neutron source will be conducted. Furthermore, the interrogation system will be numerically investigated by using nuclear materials, a D-D neutron source, and a steel container.

Cystic Fibrosis Revisited - a Review Study.

PubMed

Klimova, Blanka; Kuca, Kamil; Novotny, Michal; Maresova, Petra

2017-01-01

Cystic fibrosis (CF) is an incurable, chronic disease, which causes severe damages to respiratory and digestive tracts. It is the most common genetically inherited disease among caucasians. This disease is caused by defects in CF genes, the so-called mutations in cystic fibrosis transmembrane conductance regulator (CFTR) gene population. At present over 100,000 people suffer from this disease worldwide. The purpose of this review study is to describe the pathophysiology of CF and provide the latest information on its diagnosis and treatment therapies with respect to the improvement of patient's quality of life and emphasis on targeted specialized care. The methodological approaches include a method of literature review of available sources exploring the issue of cystic fibrosis both from a global and specific perspective point of view. A search was performed in the databases PubMed, MEDLINE, Web of Science, Scopus, Springer and ScienceDirect. Furthermore, other sources cited in the analyzed studies were also examined. On the basis of evaluation of these literature sources, the research issue was explored. The main benefits (e.g., specialized centres for the treatment of CF exist or a new breakthrough in the gene therapy of CF has been made) and limitations (e.g., comorbidity of CF, lifelong and costly treatment, or adverse impact on patient's and caregiver's quality of life) in the treatment of narcolepsy are highlighted. CF requires an integrated treatment approach in specialized CF centers, involving various factors contributing to a better patient's state of health in the form of relevant and well-balanced non-pharmacological and pharmacological therapies. In addition, further large scale clinical trials are needed in order to develop compounds that are aimed at the most common classes of CFTR. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

CF.sub.4 laser

DOEpatents

Wittig, Curt; Tiee, Joe J.

1979-01-01

A CF.sub.4 laser for producing near 16 .mu.m radiation utilizing a line tunable CO.sub.2 laser as an optical pumping source. The device uses a cryogenically cooled optically pumped cell containing molecular CF.sub.4 gas. An optical resonant cavity formed around the optically pumped cell induces oscillations of near 16 .mu.m radiation from the .nu..sub.2 +.nu..sub.4 .fwdarw..nu..sub.2 transition in the molecular CF.sub.4 gas.

Detecting fission from special nuclear material sources

DOEpatents

Rowland, Mark S [Alamo, CA; Snyderman, Neal J [Berkeley, CA

2012-06-05

A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source. The system includes a graphing component that displays the plot of the neutron distribution from the unknown source over a Poisson distribution and a plot of neutrons due to background or environmental sources. The system further includes a known neutron source placed in proximity to the unknown source to actively interrogate the unknown source in order to accentuate differences in neutron emission from the unknown source from Poisson distributions and/or environmental sources.

A reference aerosol for a radon reference chamber

NASA Astrophysics Data System (ADS)

Paul, Annette; Keyser, Uwe

1996-02-01

The measurement of radon and radon progenies and the calibration of their detection systems require the production and measurement of aerosols well-defined in size and concentration. In the German radon reference chamber, because of its unique chemical and physical properties, carnauba wax is used to produce standard aerosols. The aerosol size spectra are measured on-line by an aerosol measurement system in the range of 10 nm to 1 μm aerodynamic diameter. The experimental set-ups for the study of adsorption of radioactive ions on aerosols as function of their size and concentration will be described, the results presented and further adaptations for an aerosol jet introduced (for example, for the measurement of short-lived neutron-rich isotopes). Data on the dependence of aerosol radius, ion concentration and element selectivity is collected by using a 252Cf-sf source. The fission products of this source range widely in elements, isotopes and charges. Adsorption and the transport of radioactive ions on aerosols have therefore been studied for various ions for the first time, simultaneously with the aerosol size on-line spectrometry.

Measurement of the 23Na(n,2n) cross section in 235U and 252Cf fission neutron spectra

NASA Astrophysics Data System (ADS)

Košťál, Michal; Schulc, Martin; Rypar, Vojtěch; Losa, Evžen; Švadlenková, Marie; Baroň, Petr; Jánský, Bohumil; Novák, Evžen; Mareček, Martin; Uhlíř, Jan

2017-09-01

The presented paper aims to compare the calculated and experimental reaction rates of 23Na(n,2n)22Na in a well-defined reactor spectra and in the spontaneous fission spectrum of 252Cf. The experimentally determined reaction rate, derived using gamma spectroscopy of irradiated NaF sample, is used for average cross section determination.Estimation of this cross-section is important as it is included in International Reactor Dosimetry and Fusion File and is also relevant to the correct estimation of long-term activity of Na coolant in Sodium Fast Reactors. The calculations were performed with the MCNP6 code using ENDF/B-VII.0, JEFF-3.1, JEFF-3.2, JENDL-3.3, JENDL-4, ROSFOND-2010, CENDL-3.1 and IRDFF nuclear data libraries. In the case of reactor spectrum, reasonable agreement was not achieved with any library. However, in the case of 252Cf spectrum agreement was achieved with IRDFF, JEFF-3.1 and JENDL libraries.

A Neutron Diffractometer for a Long Pulsed Neutron Source

NASA Astrophysics Data System (ADS)

Sokol, Paul; Wang, Cailin

Long pulsed neutron sources are being actively developed as small university based sources and are being considered for the next generation of high powered sources, such as the European Neutron Source (ESS) and the Spallation Neutron Source (SNS) second target station. New instrumentation concepts will be required to effectively utilize the full spectrum of neutrons generated by these sources. Neutron diffractometers, which utilize time-of-flight (TOF) techniques for wavelength resolution, are particularly problematic. We describe an instrument for a long pulsed source that provides resolution comparable to that obtained on short pulsed sources without the need of long incident flight paths. We accomplish this by utilizing high speed choppers to impose a time structure on the spectrum of incident neutrons. By strategically positioning these choppers the response matrix assumes a convenient form that can be deconvoluted from the measured TOF spectrum to produce the diffraction pattern of the sample. We compare the performance of this instrument to other possible diffraction instruments that could be utilized on a long pulsed source.

10 CFR 39.55 - Tritium neutron generator target sources.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 1 2010-01-01 2010-01-01 false Tritium neutron generator target sources. 39.55 Section 39... Equipment § 39.55 Tritium neutron generator target sources. (a) Use of a tritium neutron generator target....77. (b) Use of a tritium neutron generator target source, containing quantities exceeding 1,110 GBg...

10 CFR 39.55 - Tritium neutron generator target sources.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 1 2011-01-01 2011-01-01 false Tritium neutron generator target sources. 39.55 Section 39... Equipment § 39.55 Tritium neutron generator target sources. (a) Use of a tritium neutron generator target....77. (b) Use of a tritium neutron generator target source, containing quantities exceeding 1,110 GBg...

10 CFR 39.55 - Tritium neutron generator target sources.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 1 2014-01-01 2014-01-01 false Tritium neutron generator target sources. 39.55 Section 39... Equipment § 39.55 Tritium neutron generator target sources. (a) Use of a tritium neutron generator target....77. (b) Use of a tritium neutron generator target source, containing quantities exceeding 1,110 GBg...

10 CFR 39.55 - Tritium neutron generator target sources.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 1 2013-01-01 2013-01-01 false Tritium neutron generator target sources. 39.55 Section 39... Equipment § 39.55 Tritium neutron generator target sources. (a) Use of a tritium neutron generator target....77. (b) Use of a tritium neutron generator target source, containing quantities exceeding 1,110 GBg...

10 CFR 39.55 - Tritium neutron generator target sources.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 1 2012-01-01 2012-01-01 false Tritium neutron generator target sources. 39.55 Section 39... Equipment § 39.55 Tritium neutron generator target sources. (a) Use of a tritium neutron generator target....77. (b) Use of a tritium neutron generator target source, containing quantities exceeding 1,110 GBg...

Organic Scintillator for Real-Time Neutron Dosimetry

DOE PAGES

Beyer, Kyle A.; Di Fulvio, Angela; Stolarczyk, Liliana; ...

2017-11-15

We have developed a radiation detector based on an organic scintillator for spectrometry and dosimetry of out-of-field secondary neutrons from clinical proton beams. The detector consists of an EJ-299-34 crystalline organic scintillator, coupled by fiber optic cable to a silicon photomultiplier (SiPM). Proof of concept measurements were taken with 137Cs and 252Cf, and corresponding simulations were performed in MCNPX-PoliMi. Despite its small size, the detector is able to discriminate between neutron and gamma-rays via pulse shape discrimination. We simulated the response function of the detector to monoenergetic neutrons in the 100 keV–0 MeV range using MCNPX-PoliMi. The measured unfolded 252Cfmore » neutron spectrum is in good agreement with the theoretical Watt fission spectrum. We determined the ambient dose equivalent by folding the spectrum with the fluence-to-ambient dose conversion coefficient, with a 1.4% deviation from theory. Some preliminary proton beam experiments were preformed at the Bronowice Cyclotron Center patient treatment facility using a clinically relevant proton pencil beam for brain tumor and craino-spinal treatment directed at a child phantom.« less

Investigations of Nuclear Structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarantites, Demetrios; Reviol, W.

The proposal addresses studies of nuclear structure at low-energies and development of instrumentation for that purpose. The structure studies deal with features of neutron-rich nuclei with unexplored shapes (football- or pear-shaped nuclei). The regions of interest are: neutron rich nuclei like 132-138Sn, or 48-54Ca, and the Zr, Mo, and Ru isotopes. The tools used can be grouped as follows: either Gammasphere or Gretina multi-gamma detector arrays and auxiliary detectors (Microball, Neutron Shell, and the newly completed Phoswich Wall).The neutron-rich nuclei are accessed by radioactive-beam binary reactions or by 252Cf spontaneous fission. The experiments with heavy radioactive beams aim at excitingmore » the beam nuclei by pick-up or transfer a neutron or a proton from a light target like 13C, 9Be, 11B or 14N .For these binary-reaction studies the Phoswich Wall detector system is essential. It is based on four multi-anode photomultiplier tubes on which CsI and thin fast-timing plastic scintillators are attached. Their signals are digitized with a high density microchip system.« less

A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions

NASA Astrophysics Data System (ADS)

Syed Mohd, A.; Pütter, S.; Mattauch, S.; Koutsioubas, A.; Schneider, H.; Weber, A.; Brückel, T.

2016-12-01

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 Å-1. The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions.

Organic Scintillator for Real-Time Neutron Dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beyer, Kyle A.; Di Fulvio, Angela; Stolarczyk, Liliana

We have developed a radiation detector based on an organic scintillator for spectrometry and dosimetry of out-of-field secondary neutrons from clinical proton beams. The detector consists of an EJ-299-34 crystalline organic scintillator, coupled by fiber optic cable to a silicon photomultiplier (SiPM). Proof of concept measurements were taken with 137Cs and 252Cf, and corresponding simulations were performed in MCNPX-PoliMi. Despite its small size, the detector is able to discriminate between neutron and gamma-rays via pulse shape discrimination. We simulated the response function of the detector to monoenergetic neutrons in the 100 keV–0 MeV range using MCNPX-PoliMi. The measured unfolded 252Cfmore » neutron spectrum is in good agreement with the theoretical Watt fission spectrum. We determined the ambient dose equivalent by folding the spectrum with the fluence-to-ambient dose conversion coefficient, with a 1.4% deviation from theory. Some preliminary proton beam experiments were preformed at the Bronowice Cyclotron Center patient treatment facility using a clinically relevant proton pencil beam for brain tumor and craino-spinal treatment directed at a child phantom.« less

A versatile UHV transport and measurement chamber for neutron reflectometry under UHV conditions.

PubMed

Syed Mohd, A; Pütter, S; Mattauch, S; Koutsioubas, A; Schneider, H; Weber, A; Brückel, T

2016-12-01

We report on a versatile mini ultra-high vacuum (UHV) chamber which is designed to be used on the MAgnetic Reflectometer with high Incident Angle of the Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum in Garching, Germany. Samples are prepared in the adjacent thin film laboratory by molecular beam epitaxy and moved into the compact chamber for transfer without exposure to ambient air. The chamber is based on DN 40 CF flanges and equipped with sapphire view ports, a small getter pump, and a wobble stick, which serves also as sample holder. Here, we present polarized neutron reflectivity measurements which have been performed on Co thin films at room temperature in UHV and in ambient air in a magnetic field of 200 mT and in the Q-range of 0.18 Å -1 . The results confirm that the Co film is not contaminated during the polarized neutron reflectivity measurement. Herewith it is demonstrated that the mini UHV transport chamber also works as a measurement chamber which opens new possibilities for polarized neutron measurements under UHV conditions.

The Los Alamos Neutron Science Center Spallation Neutron Sources

NASA Astrophysics Data System (ADS)

Nowicki, Suzanne F.; Wender, Stephen A.; Mocko, Michael

The Los Alamos Neutron Science Center (LANSCE) provides the scientific community with intense sources of neutrons, which can be used to perform experiments supporting civilian and national security research. These measurements include nuclear physics experiments for the defense program, basic science, and the radiation effect programs. This paper focuses on the radiation effects program, which involves mostly accelerated testing of semiconductor parts. When cosmic rays strike the earth's atmosphere, they cause nuclear reactions with elements in the air and produce a wide range of energetic particles. Because neutrons are uncharged, they can reach aircraft altitudes and sea level. These neutrons are thought to be the most important threat to semiconductor devices and integrated circuits. The best way to determine the failure rate due to these neutrons is to measure the failure rate in a neutron source that has the same spectrum as those produced by cosmic rays. Los Alamos has a high-energy and a low-energy neutron source for semiconductor testing. Both are driven by the 800-MeV proton beam from the LANSCE accelerator. The high-energy neutron source at the Weapons Neutron Research (WNR) facility uses a bare target that is designed to produce fast neutrons with energies from 100 keV to almost 800 MeV. The measured neutron energy distribution from WNR is very similar to that of the cosmic-ray-induced neutrons in the atmosphere. However, the flux provided at the WNR facility is typically 5×107 times more intense than the flux of the cosmic-ray-induced neutrons. This intense neutron flux allows testing at greatly accelerated rates. An irradiation test of less than an hour is equivalent to many years of neutron exposure due to cosmic-ray neutrons. The low-energy neutron source is located at the Lujan Neutron Scattering Center. It is based on a moderated source that provides useful neutrons from subthermal energies to ∼100 keV. The characteristics of these sources, and ongoing industry program are described in this paper.

Fusion neutron source blanket: requirements for calculation accuracy and benchmark experiment precision

NASA Astrophysics Data System (ADS)

Zhirkin, A. V.; Alekseev, P. N.; Batyaev, V. F.; Gurevich, M. I.; Dudnikov, A. A.; Kuteev, B. V.; Pavlov, K. V.; Titarenko, Yu. E.; Titarenko, A. Yu.

2017-06-01

In this report the calculation accuracy requirements of the main parameters of the fusion neutron source, and the thermonuclear blankets with a DT fusion power of more than 10 MW, are formulated. To conduct the benchmark experiments the technical documentation and calculation models were developed for two blanket micro-models: the molten salt and the heavy water solid-state blankets. The calculations of the neutron spectra, and 37 dosimetric reaction rates that are widely used for the registration of thermal, resonance and threshold (0.25-13.45 MeV) neutrons, were performed for each blanket micro-model. The MCNP code and the neutron data library ENDF/B-VII were used for the calculations. All the calculations were performed for two kinds of neutron source: source I is the fusion source, source II is the source of neutrons generated by the 7Li target irradiated by protons with energy 24.6 MeV. The spectral indexes ratios were calculated to describe the spectrum variations from different neutron sources. The obtained results demonstrate the advantage of using the fusion neutron source in future experiments.

A Monte Carlo Simulation of Prompt Gamma Emission from Fission Fragments

NASA Astrophysics Data System (ADS)

Regnier, D.; Litaize, O.; Serot, O.

2013-03-01

The prompt fission gamma spectra and multiplicities are investigated through the Monte Carlo code FIFRELIN which is developed at the Cadarache CEA research center. Knowing the fully accelerated fragment properties, their de-excitation is simulated through a cascade of neutron, gamma and/or electron emissions. This paper presents the recent developments in the FIFRELIN code and the results obtained on the spontaneous fission of 252Cf. Concerning the decay cascades simulation, a fully Hauser-Feshbach model is compared with a previous one using a Weisskopf spectrum for neutron emission. A particular attention is paid to the treatment of the neutron/gamma competition. Calculations lead using different level density and gamma strength function models show significant discrepancies of the slope of the gamma spectra at high energy. The underestimation of the prompt gamma spectra obtained regardless our de-excitation cascade modeling choice is discussed. This discrepancy is probably linked to an underestimation of the post-neutron fragments spin in our calculation.

The new double energy-velocity spectrometer VERDI

NASA Astrophysics Data System (ADS)

Jansson, Kaj; Frégeau, Marc Olivier; Al-Adili, Ali; Göök, Alf; Gustavsson, Cecilia; Hambsch, Franz-Josef; Oberstedt, Stephan; Pomp, Stephan

2017-09-01

VERDI (VElocity foR Direct particle Identification) is a fission-fragment spectrometer recently put into operation at JRC-Geel. It allows measuring the kinetic energy and velocity of both fission fragments simultaneously. The velocity provides information about the pre-neutron mass of each fission fragment when isotropic prompt-neutron emission from the fragments is assumed. The kinetic energy, in combination with the velocity, provides the post-neutron mass. From the difference between pre- and post-neutron masses, the number of neutrons emitted by each fragment can be determined. Multiplicity as a function of fragment mass and total kinetic energy is one important ingredient, essential for understanding the sharing of excitation energy between fission fragments at scission, and may be used to benchmark nuclear de-excitation models. The VERDI spectrometer design is a compromise between geometrical efficiency and mass resolution. The spectrometer consists of an electron detector located close to the target and two arrays of silicon detectors, each located 50 cm away from the target. In the present configuration pre-neutron and post-neutron mass distributions are in good agreement with reference data were obtained. Our latest measurements performed with spontaneously fissioning 252Cf is presented along with the developed calibration procedure to obtain pulse height defect and plasma delay time corrections.

Estimation of low-level neutron dose-equivalent rate by using extrapolation method for a curie level Am-Be neutron source.

PubMed

Li, Gang; Xu, Jiayun; Zhang, Jie

2015-01-01

Neutron radiation protection is an important research area because of the strong radiation biological effect of neutron field. The radiation dose of neutron is closely related to the neutron energy, and the connected relationship is a complex function of energy. For the low-level neutron radiation field (e.g. the Am-Be source), the commonly used commercial neutron dosimeter cannot always reflect the low-level dose rate, which is restricted by its own sensitivity limit and measuring range. In this paper, the intensity distribution of neutron field caused by a curie level Am-Be neutron source was investigated by measuring the count rates obtained through a 3 He proportional counter at different locations around the source. The results indicate that the count rates outside of the source room are negligible compared with the count rates measured in the source room. In the source room, 3 He proportional counter and neutron dosimeter were used to measure the count rates and dose rates respectively at different distances to the source. The results indicate that both the count rates and dose rates decrease exponentially with the increasing distance, and the dose rates measured by a commercial dosimeter are in good agreement with the results calculated by the Geant4 simulation within the inherent errors recommended by ICRP and IEC. Further studies presented in this paper indicate that the low-level neutron dose equivalent rates in the source room increase exponentially with the increasing low-energy neutron count rates when the source is lifted from the shield with different radiation intensities. Based on this relationship as well as the count rates measured at larger distance to the source, the dose rates can be calculated approximately by the extrapolation method. This principle can be used to estimate the low level neutron dose values in the source room which cannot be measured directly by a commercial dosimeter. Copyright © 2014 Elsevier Ltd. All rights reserved.

Finding Motivation: Online Information Seeking Following Newborn Screening for Cystic Fibrosis.

PubMed

Strekalova, Yulia A

2016-07-01

Cystic fibrosis (CF) is a genetic disease that has no manifestations for carriers but is terminal for those diagnosed with it. CF is identified through newborn screening (NBS) tests, and most families have no knowledge about CF before their contact with a NBS program. Acknowledging the Internet as a popular health information source, this study examined information exchange about CF in online community forums. This article, guided by self-determination theory, aimed at providing understanding of psychological needs and motivation for health information seeking and active communication about CF. Through online communication with other families who share similar experience, caregivers of newborns diagnosed with CF sought and received support for their competence, autonomy, and relatedness needs during the initial CF testing and diagnosis reconciliation process. Online communities play an important role in the information seeking related to CF diagnosis and could become active partners in strategic knowledge dissemination efforts. © The Author(s) 2015.

Dating groundwater with trifluoromethyl sulfurpentafluoride (SF 5CF3), sulfur hexafluoride (SF6), CF 3Cl (CFC-13), and CF2Cl2 (CFC-12)

USGS Publications Warehouse

Busenberg, E.; Plummer, Niel

2008-01-01

[1] A new groundwater dating procedure using the transient atmospheric signal of the environmental tracers SF5CF3, CFC-13, SF6, and CFC-12 was developed. The analytical procedure determines concentrations of the four tracers in air and water samples. SF 5CF3 and CFC-13 can be used to date groundwaters in some environments where the CFCs and SF6 have previously failed because these new tracers have increasing atmospheric input functions, no known terrigenic source, and are believed to be stable under reducing conditions. SF5CF3 has a dating range from 1970 to modern; the mixing ratio (mole fraction) in North American air has increased from the detection limit of 0.005 parts per trillion (ppt) to the 2006 mole fraction of about 0.16 ppt. No evidence was found for degradation of SF5CF3 in laboratory anaerobic systems. The solubility of SF5CF3 was measured in water from 1 to 35??C. Groundwater samples that contained large amounts of terrigenic SF6 did not contain terrigenic SF 5CF3. CFC-13 is a trace atmospheric gas with a dating range in groundwater of about 1965 to modem. CFC-13 has been used primarily in very low-temperature refrigeration; thus groundwater environments are less likely to be contaminated with nonatmospheric sources as compared to other widely used CFCs. Because of the low solubility of SF5CF3 and CFC-13 in water, an excess air correction must be applied to the apparent ages. The new dating procedure was tested in water samples from wells and springs from Maryland, Virginia, and West Virginia.

Product toxicity and cometabolic competitive inhibition modeling of chloroform and trichloroethylene transformation by methanotrophic resting cells.

PubMed Central

Alvarez-Cohen, L; McCarty, P L

1991-01-01

The rate and capacity for chloroform (CF) and trichloroethylene (TCE) transformation by a mixed methanotrophic culture of resting cells (no exogenous energy source) and formate-fed cells were measured. As reported previously for TCE, formate addition resulted in an increased CF transformation rate (0.35 day-1 for resting cells and 1.5 day-1 for formate-fed cells) and transformation capacity (0.0065 mg of CF per mg of cells for resting cells and 0.015 mg of CF per mg of cells for formate-fed cells), suggesting that depletion of energy stores affects transformation behavior. The observed finite transformation capacity, even with an exogenous energy source, suggests that toxicity was also a factor. CF transformation capacity was significantly lower than that for TCE, suggesting a greater toxicity from CF transformation. The toxicity of CF, TCE, and their transformation products to whole cells was evaluated by comparing the formate oxidation activity of acetylene-treated cells to that of non-acetylene-treated cells with and without prior exposure to CF or TCE. Acetylene arrests the activity of methane monooxygenase in CF and TCE oxidation without halting cell activity toward formate. Significantly diminished formate oxidation by cells exposed to either CR or TCE without acetylene compared with that with acetylene suggests that the solvents themselves were not toxic under the experimental conditions but their transformation products were. The concurrent transformation of CF and TCE by resting cells was measured, and results were compared with predictions from a competitive-inhibition cometabolic transformation model. The reasonable fit between model predictions and experimental observations was supportive of model assumptions. PMID:1905516

New sources and instrumentation for neutron science

NASA Astrophysics Data System (ADS)

Gil, Alina

2011-04-01

Neutron-scattering research has a lot to do with our everyday lives. Things like medicine, food, electronics, cars and airplanes have all been improved by neutron-scattering research. Neutron research also helps scientists improve materials used in a multitude of different products, such as high-temperature superconductors, powerful lightweight magnets, stronger, lighter plastic products etc. Neutron scattering is one of the most effective ways to obtain information on both, the structure and the dynamics of condensed matter. Most of the world's neutron sources were built decades ago, and although the uses and demand for neutrons have increased throughout the years, few new sources have been built. The new construction, accelerator-based neutron source, the spallation source will provide the most intense pulsed neutron beams in the world for scientific research and industrial development. In this paper it will be described what neutrons are and what unique properties make them useful for science, how spallation source is designed to produce neutron beams and the experimental instruments that will use those beams. Finally, it will be described how past neutron research has affected our everyday lives and what we might expect from the most exciting future applications.

The Development of Neutron Radiography and Tomography on a SLOWPOKE-2 Reactor

NASA Astrophysics Data System (ADS)

Bennett, L. G. I.; Lewis, W. J.; Hungler, P. C.

Development of neutron radiography at the Royal Military College of Canada (RMC) started by trying to interest the Royal Canadian Air Force (RCAF) in this new non-destructive testing (NDT) technique. A Californium-252 based device was ordered and then installed at RMC for development of applicable techniques for aircraft by the first author. A second and transportable device was then designed, modified and used in trials at RCAF Bases and other locations for one year. This activity was the only foreign loan of the U.S. Californium Loan Program. Around this time, SLOWPOKE-2 reactors were being installed at four Canadian universities, while a new science and engineering building was being built at RMC. A reactor pool was incorporated and efforts to procure a reactor succeeded a decade later with a SLOWPOKE-2 reactor being installed at RMC. The only modification by the vendor for RMC was a thermal column replacing an irradiation site inside the reactor container for a later installation of a neutron beam tube (NBT). Development of a working NBT took several years, starting with the second author. A demonstration of the actual worth of neutron radiography took place with a CF-18 Hornet aircraft being neutron and X-radiographed at McClellan Air Force Base, Sacramento, CA. This inspection was followed by one of the rudders that had indications of water ingress being radiographed successfully at RMC just after the NBT became functional. The next step was to develop a neutron radioscopy system (NRS), initially employing film and then digital imaging, and is in use today for all flight control surfaces (FCS). With the third author, a technique capable of removing water from affected FCS was developed at RMC. Heating equipment and a vacuum system were utilized to carefully remove the water. This technique was proven using a sequence of near real time neutron images obtained during the drying process. The results of the drying process were correlated with a relative humidity gauge and an NDT technique that could be performed at Canadian Forces (CF) Bases was developed. In order to determine the structural integrity of the component having undergone this water removal, further research was required into the effect of water inside composite honeycomb structures. This need has led to the present development of neutron tomography on the reactor at RMC, which is capable of determining the exact location of water ingress inside composite components. This technique has been successfully applied to coupons as well as to complete rudders.

Measuring soil moisture near soil surface...minor differences due to neutron source type

Treesearch

Robert R. Ziemer; Irving Goldberg; Norman A. MacGillivray

1967-01-01

Moisture measurements were made in three media?paraffin, water, saturated sand?with four neutron miusture meters, each containing 226-radium-beryllium, 227-actinium-beryllium, 238-plutonium-beryllium, or 241-americium-beryllium neutron sources. Variability in surface detection by the different sources may be due to differences in neutron sources, in length of source,...

Intense fusion neutron sources

NASA Astrophysics Data System (ADS)

Kuteev, B. V.; Goncharov, P. R.; Sergeev, V. Yu.; Khripunov, V. I.

2010-04-01

The review describes physical principles underlying efficient production of free neutrons, up-to-date possibilities and prospects of creating fission and fusion neutron sources with intensities of 1015-1021 neutrons/s, and schemes of production and application of neutrons in fusion-fission hybrid systems. The physical processes and parameters of high-temperature plasmas are considered at which optimal conditions for producing the largest number of fusion neutrons in systems with magnetic and inertial plasma confinement are achieved. The proposed plasma methods for neutron production are compared with other methods based on fusion reactions in nonplasma media, fission reactions, spallation, and muon catalysis. At present, intense neutron fluxes are mainly used in nanotechnology, biotechnology, material science, and military and fundamental research. In the near future (10-20 years), it will be possible to apply high-power neutron sources in fusion-fission hybrid systems for producing hydrogen, electric power, and technological heat, as well as for manufacturing synthetic nuclear fuel and closing the nuclear fuel cycle. Neutron sources with intensities approaching 1020 neutrons/s may radically change the structure of power industry and considerably influence the fundamental and applied science and innovation technologies. Along with utilizing the energy produced in fusion reactions, the achievement of such high neutron intensities may stimulate wide application of subcritical fast nuclear reactors controlled by neutron sources. Superpower neutron sources will allow one to solve many problems of neutron diagnostics, monitor nano-and biological objects, and carry out radiation testing and modification of volumetric properties of materials at the industrial level. Such sources will considerably (up to 100 times) improve the accuracy of neutron physics experiments and will provide a better understanding of the structure of matter, including that of the neutron itself.

Quantifying the Contributions of Environmental Parameters to Ceres Surface Net Radiation Error in China

NASA Astrophysics Data System (ADS)

Pan, X.; Yang, Y.; Liu, Y.; Fan, X.; Shan, L.; Zhang, X.

2018-04-01

Error source analyses are critical for the satellite-retrieved surface net radiation (Rn) products. In this study, we evaluate the Rn error sources in the Clouds and the Earth's Radiant Energy System (CERES) project at 43 sites from July in 2007 to December in 2007 in China. The results show that cloud fraction (CF), land surface temperature (LST), atmospheric temperature (AT) and algorithm error dominate the Rn error, with error contributions of -20, 15, 10 and 10 W/m2 (net shortwave (NSW)/longwave (NLW) radiation), respectively. For NSW, the dominant error source is algorithm error (more than 10 W/m2), particularly in spring and summer with abundant cloud. For NLW, due to the high sensitivity of algorithm and large LST/CF error, LST and CF are the largest error sources, especially in northern China. The AT influences the NLW error large in southern China because of the large AT error in there. The total precipitable water has weak influence on Rn error even with the high sensitivity of algorithm. In order to improve Rn quality, CF and LST (AT) error in northern (southern) China should be decreased.

DETECTORS AND EXPERIMENTAL METHODS: Equivalent properties of single event burnout induced by different sources

NASA Astrophysics Data System (ADS)

Yang, Shi-Yu; Cao, Zhou; Da, Dao-An; Xue, Yu-Xiong

2009-05-01

The experimental results of single event burnout induced by heavy ions and 252Cf fission fragments in power MOSFET devices have been investigated. It is concluded that the characteristics of single event burnout induced by 252Cf fission fragments is consistent to that in heavy ions. The power MOSFET in the “turn-off" state is more susceptible to single event burnout than it is in the “turn-on" state. The thresholds of the drain-source voltage for single event burnout induced by 173 MeV bromine ions and 252Cf fission fragments are close to each other, and the burnout cross section is sensitive to variation of the drain-source voltage above the threshold of single event burnout. In addition, the current waveforms of single event burnouts induced by different sources are similar. Different power MOSFET devices may have different probabilities for the occurrence of single event burnout.

Lithium target for accelerator based BNCT neutron source: Influence by the proton irradiation on lithium

NASA Astrophysics Data System (ADS)

Fujii, R.; Imahori, Y.; Nakakmura, M.; Takada, M.; Kamada, S.; Hamano, T.; Hoshi, M.; Sato, H.; Itami, J.; Abe, Y.; Fuse, M.

2012-12-01

The neutron source for Boron Neutron Capture Therapy (BNCT) is in the transition stage from nuclear reactor to accelerator based neutron source. Generation of low energy neutron can be achieved by 7Li (p, n) 7Be reaction using accelerator based neutron source. Development of small-scale and safe neutron source is within reach. The melting point of lithium that is used for the target is low, and durability is questioned for an extended use at a high current proton beam. In order to test its durability, we have irradiated lithium with proton beam at the same level as the actual current density, and found no deterioration after 3 hours of continuous irradiation. As a result, it is suggested that lithium target can withstand proton irradiation at high current, confirming suitability as accelerator based neutron source for BNCT.

Ultra-short ion and neutron pulse production

DOEpatents

Leung, Ka-Ngo; Barletta, William A.; Kwan, Joe W.

2006-01-10

An ion source has an extraction system configured to produce ultra-short ion pulses, i.e. pulses with pulse width of about 1 .mu.s or less, and a neutron source based on the ion source produces correspondingly ultra-short neutron pulses. To form a neutron source, a neutron generating target is positioned to receive an accelerated extracted ion beam from the ion source. To produce the ultra-short ion or neutron pulses, the apertures in the extraction system of the ion source are suitably sized to prevent ion leakage, the electrodes are suitably spaced, and the extraction voltage is controlled. The ion beam current leaving the source is regulated by applying ultra-short voltage pulses of a suitable voltage on the extraction electrode.

Response functions for neutron skyshine analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gui, A.A.; Shultis, J.K.; Faw, R.E.

1997-02-01

Neutron and associated secondary photon line-beam response functions (LBRFs) for point monodirectional neutron sources are generated using the MCNP Monte Carlo code for use in neutron skyshine analysis employing the integral line-beam method. The LBRFs are evaluated at 14 neutron source energies ranging from 0.01 to 14 MeV and at 18 emission angles from 1 to 170 deg, as measured from the source-to-detector axis. The neutron and associated secondary photon conical-beam response functions (CBRFs) for azimuthally symmetric neutron sources are also evaluated at 13 neutron source energies in the same energy range and at 13 polar angles of source collimationmore » from 1 to 89 deg. The response functions are approximated by an empirical three-parameter function of the source-to-detector distance. These response function approximations are available for a source-to-detector distance up to 2,500 m and, for the first time, give dose equivalent responses that are required for modern radiological assessments. For the CBRFs, ground correction factors for neutrons and secondary photons are calculated and also approximated by empirical formulas for use in air-over-ground neutron skyshine problems with azimuthal symmetry. In addition, simple procedures are proposed for humidity and atmospheric density corrections.« less

The Los Alamos Neutron Science Center Spallation Neutron Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nowicki, Suzanne F.; Wender, Stephen A.; Mocko, Michael

The Los Alamos Neutron Science Center (LANSCE) provides the scientific community with intense sources of neutrons, which can be used to perform experiments supporting civilian and national security research. These measurements include nuclear physics experiments for the defense program, basic science, and the radiation effect programs. This paper focuses on the radiation effects program, which involves mostly accelerated testing of semiconductor parts. When cosmic rays strike the earth's atmosphere, they cause nuclear reactions with elements in the air and produce a wide range of energetic particles. Because neutrons are uncharged, they can reach aircraft altitudes and sea level. These neutronsmore » are thought to be the most important threat to semiconductor devices and integrated circuits. The best way to determine the failure rate due to these neutrons is to measure the failure rate in a neutron source that has the same spectrum as those produced by cosmic rays. Los Alamos has a high-energy and a low-energy neutron source for semiconductor testing. Both are driven by the 800-MeV proton beam from the LANSCE accelerator. The high-energy neutron source at the Weapons Neutron Research (WNR) facility uses a bare target that is designed to produce fast neutrons with energies from 100 keV to almost 800 MeV. The measured neutron energy distribution from WNR is very similar to that of the cosmic-ray-induced neutrons in the atmosphere. However, the flux provided at the WNR facility is typically 5×107 times more intense than the flux of the cosmic-ray-induced neutrons. This intense neutron flux allows testing at greatly accelerated rates. An irradiation test of less than an hour is equivalent to many years of neutron exposure due to cosmic-ray neutrons. The low-energy neutron source is located at the Lujan Neutron Scattering Center. It is based on a moderated source that provides useful neutrons from subthermal energies to ~100 keV. The characteristics of these sources, and ongoing industry program are described in this paper.« less

The Los Alamos Neutron Science Center Spallation Neutron Sources

DOE PAGES

Nowicki, Suzanne F.; Wender, Stephen A.; Mocko, Michael

2017-10-26

The Los Alamos Neutron Science Center (LANSCE) provides the scientific community with intense sources of neutrons, which can be used to perform experiments supporting civilian and national security research. These measurements include nuclear physics experiments for the defense program, basic science, and the radiation effect programs. This paper focuses on the radiation effects program, which involves mostly accelerated testing of semiconductor parts. When cosmic rays strike the earth's atmosphere, they cause nuclear reactions with elements in the air and produce a wide range of energetic particles. Because neutrons are uncharged, they can reach aircraft altitudes and sea level. These neutronsmore » are thought to be the most important threat to semiconductor devices and integrated circuits. The best way to determine the failure rate due to these neutrons is to measure the failure rate in a neutron source that has the same spectrum as those produced by cosmic rays. Los Alamos has a high-energy and a low-energy neutron source for semiconductor testing. Both are driven by the 800-MeV proton beam from the LANSCE accelerator. The high-energy neutron source at the Weapons Neutron Research (WNR) facility uses a bare target that is designed to produce fast neutrons with energies from 100 keV to almost 800 MeV. The measured neutron energy distribution from WNR is very similar to that of the cosmic-ray-induced neutrons in the atmosphere. However, the flux provided at the WNR facility is typically 5×107 times more intense than the flux of the cosmic-ray-induced neutrons. This intense neutron flux allows testing at greatly accelerated rates. An irradiation test of less than an hour is equivalent to many years of neutron exposure due to cosmic-ray neutrons. The low-energy neutron source is located at the Lujan Neutron Scattering Center. It is based on a moderated source that provides useful neutrons from subthermal energies to ~100 keV. The characteristics of these sources, and ongoing industry program are described in this paper.« less

Total prompt γ-ray emission in fission

NASA Astrophysics Data System (ADS)

Wu, C. Y.; Chyzh, A.; Kwan, E.; Henderson, R. A.; Bredeweg, T. A.; Haight, R. C.; Hayes-Sterbenz, A. C.; Lee, H. Y.; O'Donnell, J. M.; Ullmann, J. L.

2017-09-01

The total prompt γ-ray energy distributions were measured for the neutron-induced fission of 235U, 239,241Pu at incident neutron energy of 0.025 eV-100 keV, and the spontaneous fission of 252Cf using the Detector for Advanced Neutron Capture Experiments (DANCE) array in coincidence with the detection of fission fragments by a parallel-plate avalanche counter. Corrections were made to the measured distribution by unfolding the two-dimension spectrum of total prompt γ-ray energy vs multiplicity using a simulated DANCE response matrix. A summary of this work is presented with the emphasis on the comparison of total prompt fission γ-ray energy between our results and previous ones. The mean values of the total prompt γ-ray energy ⟨Eγ,tot⟩, determined from the unfolded distributions, are ˜20% higher than those derived from measurements using single γ-ray detector for all the fissile nuclei studied.

Microscopic analysis of octupole shape transitions in neutron-rich actinides with relativistic energy density functional

NASA Astrophysics Data System (ADS)

Xu, Zhong; Li, Zhi-Pan

2017-12-01

Quadrupole and octupole deformation energy surfaces, low-energy excitation spectra, and electric transition rates in eight neutron-rich isotopic chains - Ra, Th, U, Pu, Cm, Cf, Fm, and No - are systematically analyzed using a quadrupole-octupole collective Hamiltonian model, with parameters determined by constrained reflection-asymmetric and axially-symmetric relativistic mean-field calculations based on the PC-PK1 energy density functional. The theoretical results of low-lying negative-parity bands, odd-even staggering, average octupole deformations ⟨β 3⟩, and show evidence of a shape transition from nearly spherical to stable octupole-deformed, and finally octupole-soft equilibrium shapes in the neutron-rich actinides. A microscopic mechanism for the onset of stable octupole deformation is also discussed in terms of the evolution of single-nucleon orbitals with deformation. Supported by National Natural Science Foundation of China (11475140, 11575148)

Studies On Particle-Accompanied Fission Of 252Cf(sf) And 235U(nth,f)

NASA Astrophysics Data System (ADS)

Kopatch, Yu N.; Tishchenko, V.; Speransky, M.; Mutterer, M.; Gönnenwein, F.; Jesinger, P.; Gagarski, A. M.; von Kalben, J.; Kojouharov, I.; Lubkiewics, E.; Mezentseva, Z.; Nezvishevsky, V.; Petrov, G. A.; Schaffner, H.; Scharma, H.; Trzaska, W. H.; Wollersheim, H.-J.

2005-11-01

In recent multi-parameter studies of spontaneous and thermal neutron induced fission, 252Cf(sf) and 235U(nth,f) respectively, the energies and emission angles of fission fragments and light charged particles were measured. Fragments were detected by an energy and angle sensitive twin ionization chamber while the light charged particles were identified by a series of ΔE-Erest telescopes. Up to Be the light particle isotopes could be disentangled. In addition, in the 252Cf(sf) experiment, gammas emitted by the fragments were analyzed by a pair of large-volume segmented clover Ge detectors. Here the main interest is to study the γ-decay and the anisotropy of gammas emitted by fragments and light particles. On the other hand, the high count rates achieved in the U-experiment performed at the high flux reactor of the ILL, Grenoble, should allow to explore fragment-particle correlations in very rare events like quaternary fission. At the present stage of data evaluation, yields and energy distributions of light particles are available. For the present contribution in particular the yields of Be-isotopes for the two reactions studied are compared and discussed. For 252Cf(sf) these isotopic yields were hitherto not known.

78 FR 21567 - Installation of Radiation Alarms for Rooms Housing Neutron Sources

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-11

... [Docket No. PRM-73-15; NRC-2011-0251] Installation of Radiation Alarms for Rooms Housing Neutron Sources... amend its regulations to require the installation of radiation alarms for rooms housing neutron sources... alarms for rooms housing neutron sources. The petitioner stated that the use of alarms can be effective...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelley, R.P.; Lewis, J.M.; Murer, D.

Previous work has measured the neutron response of pressurized {sup 4}He scintillation detectors, however these studies only examine the response as a function of incident neutron energy. Since the detection mechanism in {sup 4}He detectors is elastic scattering, and the interacting neutron will only deposit a fraction of its incident kinetic energy in the detector gas, an examination of the response of the detector output to deposited energy is necessary to transform these detectors into instruments for neutron spectrometry. Using a combined time-of-flight (TOF) and coincidence scattering method, this paper further characterizes the {sup 4}He light response to fast neutronsmore » by examining the scintillation light yield as a function of deposited energy, measuring the light response up to 5 MeV. These {sup 4}He detectors are simple in design, and are manufactured by Arktis Radiation Detectors in several sizes. The specific model used in this experiment had an active volume 20 cm long with an inner diameter of 4.4 cm, giving a total active volume of 304 cm{sup 3}. The key components include the active volume, filled with 150 bar of helium-4 gas, and photomultiplier tubes (PMTs) mounted at either end of the active volume. The detector body is made of stainless steel. The detector response was experimentally measured using a two-detector coincidence arrangement with a {sup 252}Cf source. Two {sup 4}He detectors were vertically mounted, and the source was placed at a horizontal distance from the center of the bottom detector, forming a right angle. By requiring coincidence between the two detectors, it was confirmed that each neutron interacting in the second (top) detector must first have undergone a scattering interaction in the first (bottom) detector, and the time-of-flight (TOF) technique could then be used to determine the energy of the neutron as it traveled between the two detectors by the difference in time between the two detector events. More importantly, with the scattering angle known, the amount of energy deposited by the neutron in the bottom detector (ER) was also calculated using kinematic scattering equations. This deposited recoil energy was then compared to the corresponding light output for each event to form a deposited energy scintillation light response matrix. Similarly, the system's insensitivity to gammas and its ability to reject gammas by pulse shape discrimination (PSD) are often cited as an important advantage, although a detailed analysis of these capabilities has not yet been performed. This work therefore quantified these parameters in order to further characterize these detectors for future mixed radiation field measurements. Gamma sources were measured spanning a range of gamma-ray energies from 0.122 MeV to 1.332 MeV, including {sup 57}Co, {sup 137}Cs, {sup 54}Mn, and {sup 60}Co. Each source was counted by the {sup 4}He detector and the background subtracted. Taking the ratio of the number of events detected during the experimental source measurement to the number of gammas predicted by MCNPX to pass through the detector volume yields the detector's intrinsic gamma efficiency. The difference between this fraction and unity is therefore a measure of the detector's ability to ignore interfering gamma rays, defined as its inherent gamma rejection rate. The ability of post-processing PSD algorithms to further reduce the number of gammas is also investigated and quantified. Finally, it has been noted that the scintillation signal from a single neutron event can be separated in time into two components: the fast component is a sharp peak that exists on the order of nanoseconds; the slow component is a series of smaller pulses, stretched out over four microseconds. Whereas previous research has exclusively focused on the energy information contained in the slow component, this work demonstrates that the fast component is also sensitive to neutron energy, and the entire scintillation signal can therefore be used. In conclusion, the relationship of fast neutron {sup 4}He scintillation detectors to deposited neutron energy was explored, and will be combined with previous works that measured the scintillation response to incident neutron energy in order to develop a neutron spectrometer. Similarly, the ability of these {sup 4}He detectors to reject interfering gamma rays was also quantified, and so will enable this spectrometer to be deployed in mixed radiation field measurements. Finally, while previous works with these detectors have focused on an analysis of the slow scintillation component, it was demonstrated in this work that the fast component also contains significant energy information.« less

Lithium and boron based semiconductors for thermal neutron counting

NASA Astrophysics Data System (ADS)

Kargar, Alireza; Tower, Joshua; Hong, Huicong; Cirignano, Leonard; Higgins, William; Shah, Kanai

2011-09-01

Thermal neutron detectors in planar configuration were fabricated from LiInSe2 and B2Se3 crystals grown at RMD Inc. All fabricated semiconductor devices were characterized for the current-voltage (I-V) characteristic and neutron counting measurement. Pulse height spectra were collected from 241AmBe (neutron source on all samples), as well as 137Cs and 60Co gamma ray sources. In this study, the resistivity of all crystals is reported and the collected pulse height spectra are presented for fabricated devices. Note that, the 241AmBe neutron source was custom designed with polyethylene around the source as the neutron moderator, mainly to thermalize the fast neutrons before reaching the detectors. Both LiInSe2 and B2Se3 devices showed response to thermal neutrons of the 241AmBe source.

In-beam spectroscopic study of 244Cf

NASA Astrophysics Data System (ADS)

Konki, J.; Sulignano, B.; Greenlees, P. T.; Theisen, Ch.; Auranen, K.; Badran, H.; Briselet, R.; Cox, D. M.; Defranchi Bisso, F.; Dobaczewski, J.; Grahn, T.; Herzán, A.; Herzberg, R.-D.; Julin, R.; Juutinen, S.; Khuyagbaatar, J.; Leino, M.; Lightfoot, A.; Pakarinen, J.; Papadakis, P.; Partanen, J.; Rahkila, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Shi, Y.; Smolen, M.; Sorri, J.; Stolze, S.; Uusitalo, J.

2018-02-01

The ground-state rotational band of the neutron-deficient californium (Z =98 ) isotope 244Cf was identified for the first time and measured up to a tentative spin and parity of Iπ=20+ . The observation of the rotational band indicates that the nucleus is deformed. The kinematic and dynamic moments of inertia were deduced from the measured γ -ray transition energies. The behavior of the dynamic moment of inertia revealed an up-bend due to a possible alignment of coupled nucleons in high-j orbitals starting at a rotational frequency of about ℏ ω =0.20 MeV . The results were compared with the systematic behavior of the even-even N =146 isotones as well as with available theoretical calculations that have been performed for nuclei in the region.

Measuring soil moisture near soil surface ... minor differences due to neutron source type

Treesearch

Robert R. Ziemer; Irving Goldberg; Norman A. MacGillivray

1967-01-01

Abstract - Moisture measurements were made in three media--paraffin, water, saturated sand--with four neutron moisture meters, each containing 226-radium-beryllium, 227-actinium-beryllium, 239-plutonium-beryllium, or 241-americium-beryllium neutron sources. Variability in surface detection by the different sources may be due to differences in neutron sources, in...

Characterization of a high repetition-rate laser-driven short-pulsed neutron source

NASA Astrophysics Data System (ADS)

Hah, J.; Nees, J. A.; Hammig, M. D.; Krushelnick, K.; Thomas, A. G. R.

2018-05-01

We demonstrate a repetitive, high flux, short-pulsed laser-driven neutron source using a heavy-water jet target. We measure neutron generation at 1/2 kHz repetition rate using several-mJ pulse energies, yielding a time-averaged neutron flux of 2 × 105 neutrons s‑1 (into 4π steradians). Deuteron spectra are also measured in order to understand source characteristics. Analyses of time-of-flight neutron spectra indicate that two separate populations of neutrons, ‘prompt’ and ‘delayed’, are generated at different locations. Gamma-ray emission from neutron capture 1H(n,γ) is also measured to confirm the neutron flux.

Influence of Neutron Sources and 10B Concentration on Boron Neutron Capture Therapy for Shallow and Deeper Non-small Cell Lung Cancer.

PubMed

Yu, Haiyan; Tang, Xiaobin; Shu, Diyun; Liu, Yuanhao; Geng, Changran; Gong, Chunhui; Hang, Shuang; Chen, Da

2017-03-01

Boron Neutron Capture Therapy (BNCT) is a radiotherapy that combines biological targeting and high Linear Energy Transfer (LET). It is considered a potential therapeutic approach for non-small cell lung cancer (NSCLC). It could avoid the inaccurate treatment caused by the lung motion during radiotherapy, because the dose deposition mainly depends on the boron localization and neutron source. Thus, B concentration and neutron sources are both principal factors of BNCT, and they play significant roles in the curative effect of BNCT for different cases. The purpose was to explore the feasibility of BNCT treatment for NSCLC with either of two neutron sources (the epithermal reactor at the Massachusetts Institute of Technology named "MIT source" and the accelerator neutron source designed in Argentina named "MEC source") and various boron concentrations. Shallow and deeper lung tumors were defined in the Chinese hybrid radiation phantom, and the Monte Carlo method was used to calculate the dose to tumors and healthy organs. The MEC source was more appropriate to treat the shallow tumor (depth of 6 cm) with a shorter treatment time. However, the MIT source was more suitable for deep lung tumor (depth of 9 cm) treatment, as the MEC source is more likely to exceed the skin dose limit. Thus, a neutron source consisting of more fast neutrons is not necessarily suitable for deep treatment of lung tumors. Theoretical distribution of B in tumors and organs at risk (especially skin) was obtained to meet the treatable requirement of BNCT, which may provide the references to identify the feasibility of BNCT for the treatment of lung cancer using these two neutron sources in future clinical applications.

Applications of compact accelerator-driven neutron sources: An updated assessment from the perspective of materials research in Italy

DOE PAGES

Andreani, C.; Anderson, I. S.; Carpenter, J. M.; ...

2014-12-24

In 2005 the International Atomic Energy Agency (IAEA) in Vienna published a report [1] on ‘Development Opportunities of Small and Medium Scale Accelerator Driven Neutron Sources’ which summarized the prospect of smaller sources in supporting the large spallation neutron sources for materials characterization and instrumentation, a theme advocated by Bauer, Clausen, Mank, and Mulhauser in previous publications [2-4]. In 2010 the Union for Compact Accelerator-driven Neutron Sources (UCANS) was established [5], galvanizing cross-disciplinary collaborations on new source and neutronics development and expanded applications based on both slow-neutron scattering and other neutron-matter interactions of neutron energies ranging from 10⁻⁶ to 10²more » MeV [6]. Here, we first cover the recent development of ongoing and prospective projects of compact accelerator-driven neutron sources (CANS) but concentrate on prospective accelerators currently proposed in Italy. Two active R&D topics, irradiation effects on electronics and cultural heritage studies, are chosen to illustrate the impact of state-of-the-art CANS on these programs with respect to the characteristics and complementarity of the accelerator and neutronics systems as well as instrumentation development.« less

Enhancement of ionization efficiency of mass spectrometric analysis from non-electrospray ionization friendly solvents with conventional and novel ionization techniques.

PubMed

Jiang, Ping; Lucy, Charles A

2015-10-15

Electrospray ionization mass spectrometry (ESI-MS) has significantly impacted the analysis of complex biological and petroleum samples. However ESI-MS has limited ionization efficiency for samples in low dielectric and low polarity solvents. Addition of a make-up solvent through a T union or electrospray solvent through continuous flow extractive desorption electrospray ionization (CF-EDESI) enable ionization of analytes in non-ESI friendly solvents. A conventional make-up solvent addition setup was used and a CF-EDESI source was built for ionization of nitrogen-containing standards in hexane or hexane/isopropanol. Factors affecting the performance of both sources have been investigated and optimized. Both the make-up solvent addition and CF-EDESI improve the ionization efficiency for heteroatom compounds in non-ESI friendly solvents. Make-up solvent addition provides higher ionization efficiency than CF-EDESI. Neither the make-up solvent addition nor the CF-EDESI eliminates ionization suppression of nitrogen-containing compounds caused by compounds of the same chemical class. Copyright © 2015 Elsevier B.V. All rights reserved.

The development of an energy-independent personnel neutron dosimeter using CR-39

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doremus, S.W.

The addition of specialized (n,{alpha}) radiators to a standard polyethylene/CR-39 (PE/CR-39) neutron dosimetry system was evaluated for improved response to low energy neutrons. Specialized radiators consisting of poly(vinyl alcohol) complexed with boron (natural and enriched boron-10) and poly(acrylic acid) complexed with lithium (enriched lithium-6) were evaluated. The complexion of boron with poly(vinyl alcohol) was accomplished by incorporation or surface coating. The complexion of lithium with poly(acrylic acid) was exclusively performed by incorporation. The dosimeter was designed such that the specialized radiator was in contact with the CR-39 detector (i.e., the specialized radiator was sandwiched between the CR-39 detector and polyethylenemore » radiator). The neutron response of this dosimetry system was investigated using {sup 252}Cf (moderated and bare) spontaneous fission neutrons. Detectors were chemically etched and then read with a Nikon OPTIPHOT microscope. The mean response (tracks {center dot} field{sup {minus}1}) of detectors treated with specialized (n,{alpha}) radiators were evaluated against PE/CR-39 controls. The results of this investigation demonstrate that PE/CR-39 dosimeters equipped with specialized (n,{alpha}) radiators have a noticeable response to low energy neutrons that in many instances is significantly greater than that of the controls. The addition of specialized radiators to this dosimetry system did not effect (diminish) its response to fast neutrons.« less

Toward achieving flexible and high sensitivity hexagonal boron nitride neutron detectors

NASA Astrophysics Data System (ADS)

Maity, A.; Grenadier, S. J.; Li, J.; Lin, J. Y.; Jiang, H. X.

2017-07-01

Hexagonal boron nitride (h-BN) detectors have demonstrated the highest thermal neutron detection efficiency to date among solid-state neutron detectors at about 51%. We report here the realization of h-BN neutron detectors possessing one order of magnitude enhancement in the detection area but maintaining an equal level of detection efficiency of previous achievement. These 3 mm × 3 mm detectors were fabricated from 50 μm thick freestanding and flexible 10B enriched h-BN (h-10BN) films, grown by metal organic chemical vapor deposition followed by mechanical separation from sapphire substrates. Mobility-lifetime results suggested that holes are the majority carriers in unintentionally doped h-BN. The detectors were tested under thermal neutron irradiation from californium-252 (252Cf) moderated by a high density polyethylene moderator. A thermal neutron detection efficiency of ˜53% was achieved at a bias voltage of 200 V. Conforming to traditional solid-state detectors, the realization of h-BN epilayers with enhanced electrical transport properties is the key to enable scaling up the device sizes. More specifically, the present results revealed that achieving an electrical resistivity of greater than 1014 Ωṡcm and a leakage current density of below 3 × 10-10 A/cm2 is needed to fabricate large area h-BN detectors and provided guidance for achieving high sensitivity solid state neutron detectors based on h-BN.

Normalization of a collimated 14.7 MeV neutron source in a neutron spectrometry system for benchmark experiments

NASA Astrophysics Data System (ADS)

Ofek, R.; Tsechanski, A.; Shani, G.

1988-05-01

In the present study a method used to normalize a collimated 14.7 MeV neutron beam is introduced. It combined a measurement of the fast neutron scalar flux passing through the collimator, using a copper foil activation, with a neutron transport calculation of the foil activation per unit source neutron, carried out by the discrete-ordinates transport code DOT 4.2. The geometry of the collimated neutron beam is composed of a D-T neutron source positioned 30 cm in front of a 6 cm diameter collimator, through a 120 cm thick paraffin wall. The neutron flux emitted from the D-T source was counted by an NE-213 scintillator, simultaneously with the irradiation of the copper foil. Thus, the determination of the normalization factor of the D-T source is used for an absolute flux calibration of the NE-213 scintillator. The major contributions to the uncertainty in the determination of the normalization factor, and their origins, are discussed.

Electronic neutron sources for compensated porosity well logging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, A. X.; Antolak, A. J.; Leung, K. -N.

2012-08-01

The viability of replacing Americium–Beryllium (Am–Be) radiological neutron sources in compensated porosity nuclear well logging tools with D–T or D–D accelerator-driven neutron sources is explored. The analysis consisted of developing a model for a typical well-logging borehole configuration and computing the helium-3 detector response to varying formation porosities using three different neutron sources (Am–Be, D–D, and D–T). The results indicate that, when normalized to the same source intensity, the use of a D–D neutron source has greater sensitivity for measuring the formation porosity than either an Am–Be or D–T source. The results of the study provide operational requirements that enablemore » compensated porosity well logging with a compact, low power D–D neutron generator, which the current state-of-the-art indicates is technically achievable.« less

Spallation Neutron Source reaches megawatt power

ScienceCinema

Dr. William F. Brinkman

2017-12-09

The Department of Energy's Spallation Neutron Source (SNS), already the world's most powerful facility for pulsed neutron scattering science, is now the first pulsed spallation neutron source to break the one-megawatt barrier. "Advances in the materials sciences are fundamental to the development of clean and sustainable energy technologies. In reaching this milestone of operating power, the Spallation Neutron Source is providing scientists with an unmatched resource for unlocking the secrets of materials at the molecular level," said Dr. William F. Brinkman, Director of DOE's Office of Science.

Canadian infants' nutrient intakes from complementary foods during the first year of life

PubMed Central

2010-01-01

Background Complementary feeding is currently recommended after six months of age, when the nutrients in breast milk alone are no longer adequate to support growth. Few studies have examined macro- and micro-nutrient intakes from complementary foods (CF) only. Our purpose was to assess the sources and nutritional contribution of CF over the first year of life. Methods In July 2003, a cross-sectional survey was conducted on a nationally representative sample of mothers with infants aged three to 12 months. The survey was administered evenly across all regions of the country and included a four-day dietary record to assess infants' CF intakes in household (tablespoon) measures (breast milk and formula intakes excluded). Records from 2,663 infants were analyzed for nutrient and CF food intake according to 12 categories. Mean daily intakes for infants at each month of age from CF were pooled and compared to the Dietary Reference Intakes for the respective age range. Results At three months of age, 83% of infants were already consuming infant cereals. Fruits and vegetables were among the most common foods consumed by infants at all ages, while meats were least common at all ages except 12 months. Macro- and micro-nutrient intakes from CF generally increased with age. All mean nutrient intakes, except vitamin D and iron, met CF recommendations at seven to 12 months. Conclusions Complementary foods were introduced earlier than recommended. Although mean nutrient intakes from CF at six to 12 months appear to be adequate among Canadian infants, further attention to iron and vitamin D intakes and sources may be warranted. PMID:20565759

Late-time emission of prompt fission γ rays

DOE PAGES

Talou, Patrick; Kawano, Toshihiko; Stetcu, Ionel; ...

2016-12-22

The emission of prompt fission γ rays within a few nanoseconds to a few microseconds following the scission point is studied in the Hauser-Feshbach formalism applied to the deexcitation of primary excited fission fragments. Neutron and γ-ray evaporations from fully accelerated fission fragments are calculated in competition at each stage of the decay, and the role of isomers in the fission products, before β decay, is analyzed. The time evolution of the average total γ-ray energy, the average total γ-ray multiplicity, and the fragment-specific γ-ray spectra is presented in the case of neutron-induced fission reactions of 235U and 239Pu, asmore » well as spontaneous fission of 252Cf. The production of specific isomeric states is calculated and compared to available experimental data. About 7% of all prompt fission γ rays are predicted to be emitted between 10 ns and 5 μs following fission, in the case of 235U and 239Pu( nth,f) reactions, and up to 3% in the case of 252Cf spontaneous fission. The cumulative average total γ-ray energy increases by 2% to 5% in the same time interval. Lastly, those results are shown to be robust against significant changes in the model input parameters.« less

Prompt fission γ-ray data from spontaneous fission and the mechanism of fission-fragment de-excitation

NASA Astrophysics Data System (ADS)

Oberstedt, Stephan; Dragic, Aleksandar; Gatera, Angelique; Göök, Alf; Hambsch, Franz-Josef; Oberstedt, Andreas

2017-09-01

The investigation of prompt γ-ray emission in nuclear fission has a great relevance for the assessment of prompt heat generation in a reactor core and for the better understanding of the de-excitation mechanism of fission fragments. Some years ago experimental data was scarce and available only from a few fission reactions, 233,235U(nth, f), 239Pu(nth, f), and 252Cf(sf). Initiated by a high priority data request published by the OECD/NEA a dedicated prompt fission γ-ray measurement program is being conducted at the Joint Research Centre Geel. In recent years we obtained new and accurate prompt fission γ-ray spectrum (PFGS) characteristics (average number of photons per fission, average total energy per fission and mean photon energy) from 252Cf(sf), 235U(nth, f) and 239,241Pu(nth, f) within 2% of uncertainty. In order to understand the dependence of prompt fission γ-ray emission on the compound nuclear mass and excitation energy, we started a first measurement campaign on spontaneously fissioning plutonium and curium isotopes. Results on PFGS characteristics from 240,242Pu(sf) show a dependence on the fragment mass distribution rather than on the average prompt neutron multiplicity, pointing to a more complex competition between prompt fission γ-ray and neutron emission.

Popcorn-Shaped FexO (Wüstite) Nanoparticles from a Single-Source Precursor: Colloidal Synthesis and Magnetic Properties

PubMed Central

2018-01-01

Colloidal nanoparticles (NPs) with myriads of compositions and morphologies have been synthesized and characterized in recent years. For wüstite FexO, however, obtaining phase-pure NPs with homogeneous morphologies have remained challenging. Herein, we report the colloidal synthesis of phase-pure FexO (x ≈ 0.94) popcorn-shaped NPs by decomposition of a single-source precursor, [Fe3(μ3-O)(CF3COO)(μ-CF3COO)6(H2O)2]·CF3COOH. The popcorn shape and multigrain structure had been reconstructed using high-angle annular dark-field scanning transmission electron micrograph (HAADF-STEM) tomography. This morphology offers a large surface area and internal channels and prevents further agglomeration and thermal tumbling of the subparticles. [Fe3(μ3-O)(CF3COO)(μ-CF3COO)6(H2O)2]·CF3COOH behaves as an antiferromagnetic triangle whose magnetic frustration is mitigated by the low symmetry of the complex. The popcorn-shaped FexO NPs show the typical wüstite antiferromagnetic transition at approximately 200 K, but behave very differently to their bulk counterpart below 200 K. The magnetization curves show a clear, unsymmetrical hysteresis, which arises from a combined effect of the superparamagnetic behavior and exchange bias. PMID:29606798

Popcorn-Shaped Fe x O (Wüstite) Nanoparticles from a Single-Source Precursor: Colloidal Synthesis and Magnetic Properties.

PubMed

Guntlin, Christoph P; Ochsenbein, Stefan T; Wörle, Michael; Erni, Rolf; Kravchyk, Kostiantyn V; Kovalenko, Maksym V

2018-02-27

Colloidal nanoparticles (NPs) with myriads of compositions and morphologies have been synthesized and characterized in recent years. For wüstite Fe x O, however, obtaining phase-pure NPs with homogeneous morphologies have remained challenging. Herein, we report the colloidal synthesis of phase-pure Fe x O ( x ≈ 0.94) popcorn-shaped NPs by decomposition of a single-source precursor, [Fe 3 (μ 3 -O)(CF 3 COO)(μ-CF 3 COO) 6 (H 2 O) 2 ]·CF 3 COOH. The popcorn shape and multigrain structure had been reconstructed using high-angle annular dark-field scanning transmission electron micrograph (HAADF-STEM) tomography. This morphology offers a large surface area and internal channels and prevents further agglomeration and thermal tumbling of the subparticles. [Fe 3 (μ 3 -O)(CF 3 COO)(μ-CF 3 COO) 6 (H 2 O) 2 ]·CF 3 COOH behaves as an antiferromagnetic triangle whose magnetic frustration is mitigated by the low symmetry of the complex. The popcorn-shaped Fe x O NPs show the typical wüstite antiferromagnetic transition at approximately 200 K, but behave very differently to their bulk counterpart below 200 K. The magnetization curves show a clear, unsymmetrical hysteresis, which arises from a combined effect of the superparamagnetic behavior and exchange bias.

Multiple source associated particle imaging for simultaneous capture of multiple projections

DOEpatents

Bingham, Philip R; Hausladen, Paul A; McConchi, Seth M; Mihalczo, John T; Mullens, James A

2013-11-19

Disclosed herein are representative embodiments of methods, apparatus, and systems for performing neutron radiography. For example, in one exemplary method, an object is interrogated with a plurality of neutrons. The plurality of neutrons includes a first portion of neutrons generated from a first neutron source and a second portion of neutrons generated from a second neutron source. Further, at least some of the first portion and the second portion are generated during a same time period. In the exemplary method, one or more neutrons from the first portion and one or more neutrons from the second portion are detected, and an image of the object is generated based at least in part on the detected neutrons from the first portion and the detected neutrons from the second portion.

A large 2D PSD for thermal neutron detection

NASA Astrophysics Data System (ADS)

Knott, R. B.; Smith, G. C.; Watt, G.; Boldeman, J. W.

1997-02-01

A 2D PSD based on a MWPC has been constructed for a small angle neutron scattering instrument. The active area of the detector was 640 × 640 mm 2. To meet the specifications for neutron detection efficiency and spatial resolution, and to minimise parallax, the gas mixture was 190 kPa 3He plus 100 kPa CF 4, and the active volume had a thickness of 30 mm. The design maximum neutron count rate of the detector was 10 5 events per secod. The (calculated) neutron detection efficiency was 60% for 2 Å neutrons and the (measured) neutron energy resolution on the anode grid was typically 20% (fwhm). The location of a neutron detection event within the active area was determined using the wire-by-wire method: the spatial resolution (5 × 5 mm 2) was thereby defined by the wire geometry. A 16-channel charge-sensitive preamplifier/amplifier/comparator module has been developed with a channel sensitivity of 0.1 V/fC, noise line width of 0.4 fC (fwhm) and channel-to-channel cross-talk of less than 5%. The Proportional Counter Operating System (PCOS III) (LeCroy Corp, USA) was used for event encoding. The ECL signals produced by the 16 channel modules were latched in PCOS III by a trigger pulse from the anode and the fast encoders produce a position and width for each event. The information was transferred to a UNIX workstation for accumulation and online display.

Cyclotron-based neutron source for BNCT

NASA Astrophysics Data System (ADS)

Mitsumoto, T.; Yajima, S.; Tsutsui, H.; Ogasawara, T.; Fujita, K.; Tanaka, H.; Sakurai, Y.; Maruhashi, A.

2013-04-01

Kyoto University Research Reactor Institute (KURRI) and Sumitomo Heavy Industries, Ltd. (SHI) have developed a cyclotron-based neutron source for Boron Neutron Capture Therapy (BNCT). It was installed at KURRI in Osaka prefecture. The neutron source consists of a proton cyclotron named HM-30, a beam transport system and an irradiation & treatment system. In the cyclotron, H- ions are accelerated and extracted as 30 MeV proton beams of 1 mA. The proton beams is transported to the neutron production target made by a beryllium plate. Emitted neutrons are moderated by lead, iron, aluminum and calcium fluoride. The aperture diameter of neutron collimator is in the range from 100 mm to 250 mm. The peak neutron flux in the water phantom is 1.8×109 neutrons/cm2/sec at 20 mm from the surface at 1 mA proton beam. The neutron source have been stably operated for 3 years with 30 kW proton beam. Various pre-clinical tests including animal tests have been done by using the cyclotron-based neutron source with 10B-p-Borono-phenylalanine. Clinical trials of malignant brain tumors will be started in this year.

Response Functions for Neutron Skyshine Analyses

NASA Astrophysics Data System (ADS)

Gui, Ah Auu

Neutron and associated secondary photon line-beam response functions (LBRFs) for point monodirectional neutron sources and related conical line-beam response functions (CBRFs) for azimuthally symmetric neutron sources are generated using the MCNP Monte Carlo code for use in neutron skyshine analyses employing the internal line-beam and integral conical-beam methods. The LBRFs are evaluated at 14 neutron source energies ranging from 0.01 to 14 MeV and at 18 emission angles from 1 to 170 degrees. The CBRFs are evaluated at 13 neutron source energies in the same energy range and at 13 source polar angles (1 to 89 degrees). The response functions are approximated by a three parameter formula that is continuous in source energy and angle using a double linear interpolation scheme. These response function approximations are available for a source-to-detector range up to 2450 m and for the first time, give dose equivalent responses which are required for modern radiological assessments. For the CBRF, ground correction factors for neutrons and photons are calculated and approximated by empirical formulas for use in air-over-ground neutron skyshine problems with azimuthal symmetry. In addition, a simple correction procedure for humidity effects on the neutron skyshine dose is also proposed. The approximate LBRFs are used with the integral line-beam method to analyze four neutron skyshine problems with simple geometries: (1) an open silo, (2) an infinite wall, (3) a roofless rectangular building, and (4) an infinite air medium. In addition, two simple neutron skyshine problems involving an open source silo are analyzed using the integral conical-beam method. The results obtained using the LBRFs and the CBRFs are then compared with MCNP results and results of previous studies.

NetCDF-CF: Supporting Earth System Science with Data Access, Analysis, and Visualization

NASA Astrophysics Data System (ADS)

Davis, E.; Zender, C. S.; Arctur, D. K.; O'Brien, K.; Jelenak, A.; Santek, D.; Dixon, M. J.; Whiteaker, T. L.; Yang, K.

2017-12-01

NetCDF-CF is a community-developed convention for storing and describing earth system science data in the netCDF binary data format. It is an OGC recognized standard with numerous existing FOSS (Free and Open Source Software) and commercial software tools can explore, analyze, and visualize data that is stored and described as netCDF-CF data. To better support a larger segment of the earth system science community, a number of efforts are underway to extend the netCDF-CF convention with the goal of increasing the types of data that can be represented as netCDF-CF data. This presentation will provide an overview and update of work to extend the existing netCDF-CF convention. It will detail the types of earth system science data currently supported by netCDF-CF and the types of data targeted for support by current netCDF-CF convention development efforts. It will also describe some of the tools that support the use of netCDF-CF compliant datasets, the types of data they support, and efforts to extend them to handle the new data types that netCDF-CF will support.

Accelerator based epithermal neutron source

NASA Astrophysics Data System (ADS)

Taskaev, S. Yu.

2015-11-01

We review the current status of the development of accelerator sources of epithermal neutrons for boron neutron capture therapy (BNCT), a promising method of malignant tumor treatment. Particular attention is given to the source of epithermal neutrons on the basis of a new type of charged particle accelerator: tandem accelerator with vacuum insulation and lithium neutron-producing target. It is also shown that the accelerator with specialized targets makes it possible to generate fast and monoenergetic neutrons, resonance and monoenergetic gamma-rays, alpha-particles, and positrons.

Spectrometers for compact neutron sources

NASA Astrophysics Data System (ADS)

Voigt, J.; Böhm, S.; Dabruck, J. P.; Rücker, U.; Gutberlet, T.; Brückel, T.

2018-03-01

We discuss the potential for neutron spectrometers at novel accelerator driven compact neutron sources. Such a High Brilliance Source (HBS) relies on low energy nuclear reactions, which enable cryogenic moderators in very close proximity to the target and neutron optics at comparably short distances from the moderator compared to existing sources. While the first effect aims at increasing the phase space density of a moderator, the second allows the extraction of a large phase space volume, which is typically requested for spectrometer applications. We find that competitive spectrometers can be realized if (a) the neutron production rate can be synchronized with the experiment repetition rate and (b) the emission characteristics of the moderator can be matched to the phase space requirements of the experiment. MCNP simulations for protons or deuterons on a Beryllium target with a suitable target/moderator design yield a source brightness, from which we calculate the sample fluxes by phase space considerations for different types of spectrometers. These match closely the figures of todays spectrometers at medium flux sources. Hence we conclude that compact neutron sources might be a viable option for next generation neutron sources.

Neutron range spectrometer

DOEpatents

Manglos, S.H.

1988-03-10

A neutron range spectrometer and method for determining the neutron energy spectrum of a neutron emitting source are disclosed. Neutrons from the source are colliminated along a collimation axis and a position sensitive neutron counter is disposed in the path of the collimated neutron beam. The counter determines positions along the collimation axis of interactions between the neutrons in the neutron beam and a neutron-absorbing material in the counter. From the interaction positions, a computer analyzes the data and determines the neutron energy spectrum of the neutron beam. The counter is preferably shielded and a suitable neutron-absorbing material is He-3. 1 fig.

Overview of the Neutron Radiography and Computed Tomography at the Oak Ridge National Laboratory and Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bilheux, Hassina Z; Bilheux, Jean-Christophe; Tremsin, Anton S

2015-01-01

The Oak Ridge National Laboratory (ORNL) Neutron Sciences Directorate (NScD) has installed a neutron imaging (NI) beam line at the High Flux Isotope Reactor (HFIR) cold guide hall. The CG-1D beam line produces cold neutrons for a broad range of user research spanning from engineering to material research, additive manufacturing, vehicle technologies, archaeology, biology, and plant physiology. Recent efforts have focused on increasing flux and spatial resolution. A series of selected engineering applications is presented here. Historically and for more than four decades, neutron imaging (NI) facilities have been installed exclusively at continuous (i.e. reactor-based) neutron sources rather than atmore » pulsed sources. This is mainly due to (1) the limited number of accelerator-based facilities and therefore the fierce competition for beam lines with neutron scattering instruments, (2) the limited flux available at accelerator-based neutron sources and finally, (3) the lack of high efficiency imaging detector technology capable of time-stamping pulsed neutrons with sufficient time resolution. Recently completed high flux pulsed proton-driven neutron sources such as the ORNL Spallation Neutron Source (SNS) at ORNL and the Japanese Spallation Neutron Source (JSNS) of the Japan Proton Accelerator Research Complex (J-PARC) in Japan produce high neutron fluxes that offer new and unique opportunities for NI techniques. Pulsed-based neutron imaging facilities RADEN and IMAT are currently being built at J-PARC and the Rutherford National Laboratory in the U.K., respectively. ORNL is building a pulsed neutron imaging beam line called VENUS to respond to the U.S. based scientific community. A team composed of engineers, scientists and designers has developed a conceptual design of the future VENUS imaging instrument at the SNS.« less

Recent advances in laser-driven neutron sources

NASA Astrophysics Data System (ADS)

Alejo, A.; Ahmed, H.; Green, A.; Mirfayzi, S. R.; Borghesi, M.; Kar, S.

2016-11-01

Due to the limited number and high cost of large-scale neutron facilities, there has been a growing interest in compact accelerator-driven sources. In this context, several potential schemes of laser-driven neutron sources are being intensively studied employing laser-accelerated electron and ion beams. In addition to the potential of delivering neutron beams with high brilliance, directionality and ultra-short burst duration, a laser-driven neutron source would offer further advantages in terms of cost-effectiveness, compactness and radiation confinement by closed-coupled experiments. Some of the recent advances in this field are discussed, showing improvements in the directionality and flux of the laser-driven neutron beams.

Neutron activation analysis system

DOEpatents

Taylor, M.C.; Rhodes, J.R.

1973-12-25

A neutron activation analysis system for monitoring a generally fluid media, such as slurries, solutions, and fluidized powders, including two separate conduit loops for circulating fluid samples within the range of radiation sources and detectors is described. Associated with the first loop is a neutron source that emits s high flux of slow and thermal neutrons. The second loop employs a fast neutron source, the flux from which is substantially free of thermal neutrons. Adjacent to both loops are gamma counters for spectrographic determination of the fluid constituents. Other gsmma sources and detectors are arranged across a portion of each loop for deterMining the fluid density. (Official Gazette)

Electron Attachment to Halomethanes at High Temperature: CH2CI2, CF2CI2, CH3CI, and CF3CI Attachment Rate Constants up to 1100 K

DTIC Science & Technology

2009-08-01

hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and...attachment reactions: 390i 50 meV (CH:Cl;). 124* 20 meV (CF2CI2), 670 + 70 meV (CH3CI), and 406±50 meV (CF,C1). Comparisons are made with existing data ...Research Laboratory, 29 Randolph Road, Hanscom Air Force Base . Massachusetts 01731-3010, USA (Received 15 May 2009; accepted 4 August 2009; published

Chandra Reveals Nest of Tight Binaries in Dense Cluster

NASA Astrophysics Data System (ADS)

2001-05-01

Scientists have gazed into an incredibly dense star cluster with NASA's Chandra X-ray Observatory and identified a surprising bonanza of binary stars, including a large number of rapidly rotating neutron stars. The discovery may help explain how one of the oldest structures in our Galaxy evolved over its lifetime. By combining Chandra, Hubble Space Telescope, and ground-based radio data, the researchers conducted an important survey of the binary systems that dominate the dynamics of 47 Tucanae, a globular cluster about 12 billion years old located in our Milky Way galaxy. Most of the binaries in 47 Tucanae are systems in which a normal, Sun-like companion orbits a collapsed star, either a white dwarf or a neutron star. White dwarf stars are dense, burnt-out remnants of stars like the Sun, while neutron stars are even denser remains of a more massive star. When matter from a nearby star falls onto either a white dwarf or a neutron star, as in the case with the binaries in 47 Tucanae, X-rays are produced. 47 Tuc This composite image shows relation of the Chandra image of 47 Tucanae to ground-based, optical observations. "This Chandra image provides the first complete census of compact binaries in the core of a globular cluster," said Josh Grindlay of the Harvard-Smithsonian Center for Astrophysics (CfA) and lead author of the report that appears in the May 18 issue of Science. "The relative number of neutron stars versus white dwarfs in these binaries tell us about the development of the first stars in the cluster, and the binaries themselves are key to the evolution of the entire cluster core." Many of the binaries in 47 Tucanae are exotic systems never before seen in such large quantities. Perhaps the most intriguing are the "millisecond pulsars", which contain neutron stars that are rotating extremely rapidly, between 100 to nearly 1000 times a second. "The Chandra data, in conjunction with radio observations, indicate that there are many more millisecond pulsars than we would expect based on the number of their likely progenitors we found," said co-author Peter Edmonds, also of the CfA. "While there is a general consensus on how some of the millisecond pulsars form, these new data suggest that there need to be other methods to create them." In addition to the millisecond pulsars, Chandra also detected other important populations of binary systems, including those with white dwarf stars and normal stars, and others where pairs of normal stars undergo large flares induced by their close proximity. The Chandra data also indicate an apparent absence of a central black hole. Stellar-sized mass black holes -- those about five to ten times as massive as the Sun -- have apparently not coalesced to the center of the star cluster. All or most stellar-sized black holes that formed over the lifetime of the cluster have likely been ejected by their slingshot encounters with binaries deep in the cluster core. "These results show that binary star systems are a source of gravitational energy which ejects stellar mass black holes and prevents the collapse of the cluster’s core to a more massive, central black hole," said the CfA's Craig Heinke. "In other words, binary systems - not black holes - are the dynamical heat engines that drive the evolution of globular clusters." Chandra observed 47 Tucanae on March 16-17, 2000, for a period of 74,000 seconds with the Advanced CCD Imaging Spectrometer (ACIS). The ACIS X-ray camera was developed for NASA by Penn State and the Massachusetts Institute of Technology. The High Energy Transmission Grating Spectrometer was built by MIT. NASA's Marshall Space Flight Center in Huntsville, AL, manages the Chandra program. TRW, Inc., Redondo Beach, California, is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, MA. Images associated with this release are available on the World Wide Web at: http://chandra.harvard.edu AND http://chandra.nasa.gov

Performance verification of an epithermal neutron flux monitor using accelerator-based BNCT neutron sources

NASA Astrophysics Data System (ADS)

Guan, X.; Murata, I.; Wang, T.

2017-09-01

The performance of an epithermal neutron flux monitor developed for boron neutron capture therapy (BNCT) is verified by Monte Carlo simulations using accelerator-based neutron sources (ABNSs). The results indicate that the developed epithermal neutron flux monitor works well and it can be efficiently used in practical applications to measure the epithermal neutron fluxes of ABNSs in a high accuracy.

Calculations to support JET neutron yield calibration: Modelling of neutron emission from a compact DT neutron generator

NASA Astrophysics Data System (ADS)

Čufar, Aljaž; Batistoni, Paola; Conroy, Sean; Ghani, Zamir; Lengar, Igor; Milocco, Alberto; Packer, Lee; Pillon, Mario; Popovichev, Sergey; Snoj, Luka; JET Contributors

2017-03-01

At the Joint European Torus (JET) the ex-vessel fission chambers and in-vessel activation detectors are used as the neutron production rate and neutron yield monitors respectively. In order to ensure that these detectors produce accurate measurements they need to be experimentally calibrated. A new calibration of neutron detectors to 14 MeV neutrons, resulting from deuterium-tritium (DT) plasmas, is planned at JET using a compact accelerator based neutron generator (NG) in which a D/T beam impinges on a solid target containing T/D, producing neutrons by DT fusion reactions. This paper presents the analysis that was performed to model the neutron source characteristics in terms of energy spectrum, angle-energy distribution and the effect of the neutron generator geometry. Different codes capable of simulating the accelerator based DT neutron sources are compared and sensitivities to uncertainties in the generator's internal structure analysed. The analysis was performed to support preparation to the experimental measurements performed to characterize the NG as a calibration source. Further extensive neutronics analyses, performed with this model of the NG, will be needed to support the neutron calibration experiments and take into account various differences between the calibration experiment and experiments using the plasma as a source of neutrons.

Gyrotron-driven high current ECR ion source for boron-neutron capture therapy neutron generator

NASA Astrophysics Data System (ADS)

Skalyga, V.; Izotov, I.; Golubev, S.; Razin, S.; Sidorov, A.; Maslennikova, A.; Volovecky, A.; Kalvas, T.; Koivisto, H.; Tarvainen, O.

2014-12-01

Boron-neutron capture therapy (BNCT) is a perspective treatment method for radiation resistant tumors. Unfortunately its development is strongly held back by a several physical and medical problems. Neutron sources for BNCT currently are limited to nuclear reactors and accelerators. For wide spread of BNCT investigations more compact and cheap neutron source would be much more preferable. In present paper an approach for compact D-D neutron generator creation based on a high current ECR ion source is suggested. Results on dense proton beams production are presented. A possibility of ion beams formation with current density up to 600 mA/cm2 is demonstrated. Estimations based on obtained experimental results show that neutron target bombarded by such deuteron beams would theoretically yield a neutron flux density up to 6·1010 cm-2/s. Thus, neutron generator based on a high-current deuteron ECR source with a powerful plasma heating by gyrotron radiation could fulfill the BNCT requirements significantly lower price, smaller size and ease of operation in comparison with existing reactors and accelerators.

Negative ion-driven associated particle neutron generator

DOE PAGES

Antolak, A. J.; Leung, K. N.; Morse, D. H.; ...

2015-10-09

We describe an associated particle neutron generator that employs a negative ion source to produce high neutron flux from a small source size. Furthermore, negative ions produced in an rf-driven plasma source are extracted through a small aperture to form a beam which bombards a positively biased, high voltage target electrode. Electrons co-extracted with the negative ions are removed by a permanent magnet electron filter. The use of negative ions enables high neutron output (100% atomic ion beam), high quality imaging (small neutron source size), and reliable operation (no high voltage breakdowns). Finally, the neutron generator can operate in eithermore » pulsed or continuous-wave (cw) mode and has been demonstrated to produce 10 6 D-D n/s (equivalent to similar to 10 8 D-T n/s) from a 1 mm-diameter neutron source size to facilitate high fidelity associated particle imaging.« less

Tectonic activity as a significant source of crustal tetrafluoromethane emissions to the atmosphere: observations in groundwaters along the San Andreas Fault

USGS Publications Warehouse

Deeds, Daniel A.; Kulongoski, Justin T.; Muhle, Jens; Weiss, Ray F.

2015-01-01

Tetrafluoromethane (CF4) concentrations were measured in 14 groundwater samples from the Cuyama Valley, Mil Potrero and Cuddy Valley aquifers along the Big Bend section of the San Andreas Fault System (SAFS) in California to assess whether tectonic activity in this region is a significant source of crustal CF4 to the atmosphere. Dissolved CF4 concentrations in all groundwater samples but one were elevated with respect to estimated recharge concentrations including entrainment of excess air during recharge (CreCre; ∼30 fmol kg−1 H2O), indicating subsurface addition of CF4 to these groundwaters. Groundwaters in the Cuyama Valley contain small CF4 excesses (0.1–9 times CreCre), which may be attributed to an in situ release from weathering and a minor addition of deep crustal CF4 introduced to the shallow groundwater through nearby faults. CF4 excesses in groundwaters within 200 m of the SAFS are larger (10–980 times CreCre) and indicate the presence of a deep crustal flux of CF4 that is likely associated with the physical alteration of silicate minerals in the shear zone of the SAFS. Extrapolating CF4 flux rates observed in this study to the full extent of the SAFS (1300 km × 20–100 km) suggests that the SAFS potentially emits (0.3–1)×10−1 kg(0.3–1)×10−1 kg CF4 yr−1 to the Earth's surface. For comparison, the chemical weathering of ∼7.5×104 km2∼7.5×104 km2 of granitic rock in California is estimated to release (0.019–3.2)×10−1 kg(0.019–3.2)×10−1 kg CF4 yr−1. Tectonic activity is likely an important, and potentially the dominant, driver of natural emissions of CF4 to the atmosphere. Variations in preindustrial atmospheric CF4 as observed in paleo-archives such as ice cores may therefore represent changes in both continental weathering and tectonic activity, including changes driven by variations in continental ice cover during glacial–interglacial transitions.

Cyclotron-based neutron source for BNCT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitsumoto, T.; Yajima, S.; Tsutsui, H.

2013-04-19

Kyoto University Research Reactor Institute (KURRI) and Sumitomo Heavy Industries, Ltd. (SHI) have developed a cyclotron-based neutron source for Boron Neutron Capture Therapy (BNCT). It was installed at KURRI in Osaka prefecture. The neutron source consists of a proton cyclotron named HM-30, a beam transport system and an irradiation and treatment system. In the cyclotron, H- ions are accelerated and extracted as 30 MeV proton beams of 1 mA. The proton beams is transported to the neutron production target made by a beryllium plate. Emitted neutrons are moderated by lead, iron, aluminum and calcium fluoride. The aperture diameter of neutronmore » collimator is in the range from 100 mm to 250 mm. The peak neutron flux in the water phantom is 1.8 Multiplication-Sign 109 neutrons/cm{sup 2}/sec at 20 mm from the surface at 1 mA proton beam. The neutron source have been stably operated for 3 years with 30 kW proton beam. Various pre-clinical tests including animal tests have been done by using the cyclotron-based neutron source with {sup 10}B-p-Borono-phenylalanine. Clinical trials of malignant brain tumors will be started in this year.« less

Neutron Yield With a Pulsed Surface Flashover Deuterium Source

NASA Astrophysics Data System (ADS)

Guethlein, G.; Falabella, S.; Sampayan, S. E.; Meyer, G.; Tang, V.; Kerr, P.

2009-03-01

As a step towards developing an ultra compact D-D neutron source for various defense and homeland security applications, a compact, low average power ion source is needed. Towards that end, we are testing a high current, pulsed surface flashover ion source, with deuterated titanium as the spark contacts. Neutron yield and source lifetime data will be presented using a low voltage (<100 kV) deuterated target. With 20 ns spark drive pulses we have shown >106 neutrons/s with 1 kHz PRF

A study of intrinsic statistical variation for low-energy nuclear recoils in liquid xenon detector for dark matter searches

NASA Astrophysics Data System (ADS)

Wang, Lu; Wei, Wenzhao; Mei, Dongming; Cubed Collaboration

2015-10-01

Noble liquid xenon experiments, such as XENON100, LUX, XENON 1-Ton, and LZ are large dark matter experiments directly searches for weakly interacting massive particles (WIMPs). One of the most important features is to discriminate nuclear recoils from electronic recoils. Detector response is generally calibrated with different radioactive sources including 83mKr, tritiated methane, 241AmBe, 252Cf, and DD-neutrons. The electronic recoil and nuclear recoil bands have been determined by these calibrations. However, the width of nuclear recoil band needs to be fully understood. We derive a theoretical model to understand the correlation of the width of nuclear recoil band and intrinsic statistical variation. In addition, we conduct experiments to validate the theoretical model. In this paper, we present the study of intrinsic statistical variation contributing to the width of nuclear recoil band. DE-FG02-10ER46709 and the state of South Dakota.

Studies of PuF sub 6 and transplutonic materials' critical properties for space high power nuclear pumped lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, A.G.; Miller, M.S.

1991-01-01

All space missions require a reliable, compact source of energy. This paper describes preliminary neutronics studies of pocket'' reactor concepts employing PuF{sub 6} and transplutonic materials as fuels for space high power/energy Nuclear Pumped Lasers (NPLs). Previous research has studied NPL reactor concepts with thin fuel layers, aerosol fuels and gaseous UF{sub 6}. The total reactor volumes for compact reactors with these types of fuels typically range from 3 m{sup 3} to 50 m{sup 3}. By employing PuF{sub 6} and transplutonic fuels at the same low densities, a calculated value for Keff of 1.2 has been achieved for conditions ofmore » 900 K and 5 atm, with total reactor volumes of 1.5 m{sup 3} for PuF{sub 6}, 0.51 m{sup 3} for Am-242m, 0.58 m{sup 3} for Cm-245 and 0.63 m{sup 3} for Cf-249.« less

γ -soft Ba 146 and the role of nonaxial shapes at N ≈ 90

DOE PAGES

Mitchell, A. J.; Lister, C. J.; McCutchan, E. A.; ...

2016-01-12

Low-spin states in the neutron-rich, N = 90 nuclide 146Ba were populated following β decay of 146Cs , with the goal of clarifying the development of deformation in barium isotopes through delineation of their nonyrast structures. Fission fragments of 146Cs were extracted from a 1.7-Ci 252Cf source and mass selected using the CAlifornium Rare Ion Breeder Upgrade (CARIBU) facility. Low-energy ions were deposited at the center of a box of thin β detectors, surrounded by a highly efficient high-purity Ge array. The new 146Ba decay scheme now contains 31 excited levels extending up to ~2.5 MeV excitation energy, double whatmore » was previously known. These data are compared to predictions from the interacting boson approximation (IBA) model. It appears that the abrupt shape change found at N = 90 in Sm and Gd is much more gradual in Ba and Ce, due to an enhanced role of the γ degree of freedom.« less

Key metrics for HFIR HEU and LEU models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ilas, Germina; Betzler, Benjamin R.; Chandler, David

This report compares key metrics for two fuel design models of the High Flux Isotope Reactor (HFIR). The first model represents the highly enriched uranium (HEU) fuel currently in use at HFIR, and the second model considers a low-enriched uranium (LEU) interim design fuel. Except for the fuel region, the two models are consistent, and both include an experiment loading that is representative of HFIR's current operation. The considered key metrics are the neutron flux at the cold source moderator vessel, the mass of 252Cf produced in the flux trap target region as function of cycle time, the fast neutronmore » flux at locations of interest for material irradiation experiments, and the reactor cycle length. These key metrics are a small subset of the overall HFIR performance and safety metrics. They were defined as a means of capturing data essential for HFIR's primary missions, for use in optimization studies assessing the impact of HFIR's conversion from HEU fuel to different types of LEU fuel designs.« less

Methods for absorbing neutrons

DOEpatents

Guillen, Donna P [Idaho Falls, ID; Longhurst, Glen R [Idaho Falls, ID; Porter, Douglas L [Idaho Falls, ID; Parry, James R [Idaho Falls, ID

2012-07-24

A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.

Neutron scatter camera

DOEpatents

Mascarenhas, Nicholas; Marleau, Peter; Brennan, James S.; Krenz, Kevin D.

2010-06-22

An instrument that will directly image the fast fission neutrons from a special nuclear material source has been described. This instrument can improve the signal to background compared to non imaging neutron detection techniques by a factor given by ratio of the angular resolution window to 4.pi.. In addition to being a neutron imager, this instrument will also be an excellent neutron spectrometer, and will be able to differentiate between different types of neutron sources (e.g. fission, alpha-n, cosmic ray, and D-D or D-T fusion). Moreover, the instrument is able to pinpoint the source location.

Neutron Decay Electron Injection into the Magnetosphere.

DTIC Science & Technology

1982-03-01

1000 Seconds After a Fission Burst, AFWL-TR-78-4 (November, 1978). 3. Hess, Wilmot N., The Radiation Belt and Magnetosphere, Toronto: Blaisdell Pub. Co...0a z w :3 1.-- w Ix -j L ccz I-- -i Ui)z L) 0 x La I- z) La La x . 4 I z 0. 1- ua CD cn I- 4 0)-- Cw m LaE Cf . w- La w z- L ZI--V 1- 0 La IM w z 0 x 0...mD (a "- U) :3-4 La 0 -0 M ..jZ z IM Ix Z in zci o Z L M0 2 EnC woo >- I- c La V~)P) Z -0 -0 Z 0 ik: co u x U) 4. w cD-4 lz La >-ix - Cf ) wI- xL (lI I

New evidence that a large proportion of human blood plasma cell-free DNA is localized in exosomes

PubMed Central

Jiang, Chao; Krzyzanowski, Gary D.; Ryan, Wayne L.

2017-01-01

Cell-free DNA (cfDNA) in blood is used as a source of genetic material for noninvasive prenatal and cancer diagnostic assays in clinical practice. Recently we have started a project for new biomarker discovery with a view to developing new noninvasive diagnostic assays. While reviewing literature, it was found that exosomes may be a rich source of biomarkers, because exosomes play an important role in human health and disease. While characterizing exosomes found in human blood plasma, we observed the presence of cfDNA in plasma exosomes. Plasma was obtained from blood drawn into K3EDTA tubes. Exosomes were isolated from cell-free plasma using a commercially available kit. Sizing and enumeration of exosomes were done using electron microscopy and NanoSight particle counter. NanoSight and confocal microscopy was used to demonstrate the association between dsDNA and exosomes. DNA extracted from plasma and exosomes was measured by a fluorometric method and a droplet digital PCR (ddPCR) method. Size of extracellular vesicles isolated from plasma was heterogeneous and showed a mean value of 92.6 nm and a mode 39.7 nm. A large proportion of extracellular vesicles isolated from plasma were identified as exosomes using a fluorescence probe specific for exosomes and three protein markers, Hsp70, CD9 and CD63, that are commonly used to identify exosome fraction. Fluorescence dye that stain dsDNA showed the association between exosomes and dsDNA. Plasma cfDNA concentration analysis showed more than 93% of amplifiable cfDNA in plasma is located in plasma exosomes. Storage of a blood sample showed significant increases in exosome count and exosome DNA concentration. This study provide evidence that a large proportion of plasma cfDNA is localized in exosomes. Exosome release from cells is a metabolic energy dependent process, thus suggesting active release of cfDNA from cells as a source of cfDNA in plasma. PMID:28850588

New evidence that a large proportion of human blood plasma cell-free DNA is localized in exosomes.

PubMed

Fernando, M Rohan; Jiang, Chao; Krzyzanowski, Gary D; Ryan, Wayne L

2017-01-01

Cell-free DNA (cfDNA) in blood is used as a source of genetic material for noninvasive prenatal and cancer diagnostic assays in clinical practice. Recently we have started a project for new biomarker discovery with a view to developing new noninvasive diagnostic assays. While reviewing literature, it was found that exosomes may be a rich source of biomarkers, because exosomes play an important role in human health and disease. While characterizing exosomes found in human blood plasma, we observed the presence of cfDNA in plasma exosomes. Plasma was obtained from blood drawn into K3EDTA tubes. Exosomes were isolated from cell-free plasma using a commercially available kit. Sizing and enumeration of exosomes were done using electron microscopy and NanoSight particle counter. NanoSight and confocal microscopy was used to demonstrate the association between dsDNA and exosomes. DNA extracted from plasma and exosomes was measured by a fluorometric method and a droplet digital PCR (ddPCR) method. Size of extracellular vesicles isolated from plasma was heterogeneous and showed a mean value of 92.6 nm and a mode 39.7 nm. A large proportion of extracellular vesicles isolated from plasma were identified as exosomes using a fluorescence probe specific for exosomes and three protein markers, Hsp70, CD9 and CD63, that are commonly used to identify exosome fraction. Fluorescence dye that stain dsDNA showed the association between exosomes and dsDNA. Plasma cfDNA concentration analysis showed more than 93% of amplifiable cfDNA in plasma is located in plasma exosomes. Storage of a blood sample showed significant increases in exosome count and exosome DNA concentration. This study provide evidence that a large proportion of plasma cfDNA is localized in exosomes. Exosome release from cells is a metabolic energy dependent process, thus suggesting active release of cfDNA from cells as a source of cfDNA in plasma.

Measurement of Ultracold Neutrons Produced by Using Doppler-shifted Bragg Reflection at a Pulsed-neutron Source

DOE R&D Accomplishments Database

Brun, T. O.; Carpenter, J. M.; Krohn, V. E.; Ringo, G. R.; Cronin, J. W.; Dombeck, T. W.; Lynn, J. W.; Werner, S. A.

1979-01-01

Ultracold neutrons (UCN) have been produced at the Argonne pulsed-neutron source by the Doppler shift of 400-m/s neutrons Bragg reflected from a moving crystal. The peak density of UCN produced at the crystal exceeds 0.1 n/cm{sup 3}.

Neutron Detector Signal Processing to Calculate the Effective Neutron Multiplication Factor of Subcritical Assemblies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Talamo, Alberto; Gohar, Yousry

2016-06-01

This report describes different methodologies to calculate the effective neutron multiplication factor of subcritical assemblies by processing the neutron detector signals using MATLAB scripts. The subcritical assembly can be driven either by a spontaneous fission neutron source (e.g. californium) or by a neutron source generated from the interactions of accelerated particles with target materials. In the latter case, when the particle accelerator operates in a pulsed mode, the signals are typically stored into two files. One file contains the time when neutron reactions occur and the other contains the times when the neutron pulses start. In both files, the timemore » is given by an integer representing the number of time bins since the start of the counting. These signal files are used to construct the neutron count distribution from a single neutron pulse. The built-in functions of MATLAB are used to calculate the effective neutron multiplication factor through the application of the prompt decay fitting or the area method to the neutron count distribution. If the subcritical assembly is driven by a spontaneous fission neutron source, then the effective multiplication factor can be evaluated either using the prompt neutron decay constant obtained from Rossi or Feynman distributions or the Modified Source Multiplication (MSM) method.« less

Experimental demonstration of a compact epithermal neutron source based on a high power laser

NASA Astrophysics Data System (ADS)

Mirfayzi, S. R.; Alejo, A.; Ahmed, H.; Raspino, D.; Ansell, S.; Wilson, L. A.; Armstrong, C.; Butler, N. M. H.; Clarke, R. J.; Higginson, A.; Kelleher, J.; Murphy, C. D.; Notley, M.; Rusby, D. R.; Schooneveld, E.; Borghesi, M.; McKenna, P.; Rhodes, N. J.; Neely, D.; Brenner, C. M.; Kar, S.

2017-07-01

Epithermal neutrons from pulsed-spallation sources have revolutionised neutron science allowing scientists to acquire new insight into the structure and properties of matter. Here, we demonstrate that laser driven fast (˜MeV) neutrons can be efficiently moderated to epithermal energies with intrinsically short burst durations. In a proof-of-principle experiment using a 100 TW laser, a significant epithermal neutron flux of the order of 105 n/sr/pulse in the energy range of 0.5-300 eV was measured, produced by a compact moderator deployed downstream of the laser-driven fast neutron source. The moderator used in the campaign was specifically designed, by the help of MCNPX simulations, for an efficient and directional moderation of the fast neutron spectrum produced by a laser driven source.

Planned Closeout of the Cf-252 Loan/Lease Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sherman, Steven R; Patton, Bradley D

2012-09-01

New funding is sought to pursue planned closeout of the Cf-252 Loan Program. The work will be performed in phases. In the initial phase, users will be surveyed to determine whether they wish to take ownership of sources in their possession, or return them. In the second phase, sources will be recalled from non-DOE entities, and source ownership transfers will be performed. In the third phase, the remaining sources from DOE entities will be recalled. Initial funding of $350K is sought to fund the first phase, and to plan execution of the remaining phases given information collected from user surveys.

Sensitivity Analysis of Cf-252 (sf) Neutron and Gamma Observables in CGMF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carter, Austin Lewis; Talou, Patrick; Stetcu, Ionel

CGMF is a Monte Carlo code that simulates the decay of primary fission fragments by emission of neutrons and gamma rays, according to the Hauser-Feshbach equations. As the CGMF code was recently integrated into the MCNP6.2 transport code, great emphasis has been placed on providing optimal parameters to CGMF such that many different observables are accurately represented. Of these observables, the prompt neutron spectrum, prompt neutron multiplicity, prompt gamma spectrum, and prompt gamma multiplicity are crucial for accurate transport simulations of criticality and nonproliferation applications. This contribution to the ongoing efforts to improve CGMF presents a study of the sensitivitymore » of various neutron and gamma observables to several input parameters for Californium-252 spontaneous fission. Among the most influential parameters are those that affect the input yield distributions in fragment mass and total kinetic energy (TKE). A new scheme for representing Y(A,TKE) was implemented in CGMF using three fission modes, S1, S2 and SL. The sensitivity profiles were calculated for 17 total parameters, which show that the neutron multiplicity distribution is strongly affected by the TKE distribution of the fragments. The total excitation energy (TXE) of the fragments is shared according to a parameter RT, which is defined as the ratio of the light to heavy initial temperatures. The sensitivity profile of the neutron multiplicity shows a second order effect of RT on the mean neutron multiplicity. A final sensitivity profile was produced for the parameter alpha, which affects the spin of the fragments. Higher values of alpha lead to higher fragment spins, which inhibit the emission of neutrons. Understanding the sensitivity of the prompt neutron and gamma observables to the many CGMF input parameters provides a platform for the optimization of these parameters.« less

SELF-REACTIVATING NEUTRON SOURCE FOR A NEUTRONIC REACTOR

DOEpatents

Newson, H.W.

1959-02-01

Reactors of the type employing beryllium in a reflector region around the active portion and to a neutron source for use therewith are discussed. The neutron source is comprised or a quantity of antimony permanently incorporated in, and as an integral part of, the reactor in or near the beryllium reflector region. During operation of the reactor the natural occurring antimony isotope of atomic weight 123 absorbs neutrons and is thereby transformed to the antimony isotope of atomic weight 124, which is radioactive and emits gamma rays. The gamma rays react with the beryllium to produce neutrons. The beryllium and antimony thus cooperate to produce a built in neutron source which is automatically reactivated by the operation of the reactor itself and which is of sufficient strength to maintain the slow neutron flux at a sufficiently high level to be reliably measured during periods when the reactor is shut down.

SU-F-T-183: Design of a Beam Shaping Assembly of a Compact DD-Based Boron Neutron Capture Therapy System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsieh, M; Liu, Y; Nie, L

Purpose: To design a beam shaping assembly (BSA) to shape the 2.45-MeV neutrons produced by a deuterium-deuterium (DD) neutron generator and to optimize the beam output for boron neutron capture therapy of brain tumors Methods: MCNP is used for this simulation study. The simulation model consists of a neutron surface source that resembles an actual DD source and is surrounded by a BSA. The neutron source emits 2.45-MeV neutrons isotropically. The BSA is composed of a moderator, reflector, collimator and filter. Various types of materials and geometries are tested for each component to optimize the neutron output. Neutron characteristics aremore » measured with an 2×2×2-cm{sup 3} air-equivalent cylinder at the beam exit. The ideal BSA is determined by evaluating the in-air parameters, which include epithermal neutron per source neutron, fast neutron dose per epithermal neutron, and photon dose per epithermal neutron. The parameter values are compared to those recommended by the IAEA. Results: The ideal materials for reflector and thermal neutron filter were lead and cadmium, respectively. The thickness for reflector was 43 cm and for filter was 0.5 mm. At present, the best-performing moderator has 25 cm of AlF{sub 3} and 5 cm of MgF{sub 2}. This layout creates a neutron spectrum that has a peak at approximately 10 keV and produces 1.35E-4 epithermal neutrons per source neutron per cm{sup 2}. Additional neutron characteristics, fast neutrons per epithermal neutron and photon per epithermal neutron, are still under investigation. Conclusion: Working is ongoing to optimize the final layout of the BSA. The neutron spectrum at the beam exit window of the final configuration will have the maximum number of epithermal neutrons and limited photon and fast neutron contaminations within the recommended values by IAEA. Future studies will also include phantom experiments to validate the simulation results.« less

Compact D-D/D-T neutron generators and their applications

NASA Astrophysics Data System (ADS)

Lou, Tak Pui

2003-10-01

Neutron generators based on the 2H(d,n)3He and 3H(d,n)4He fusion reactions are the most commonly available neutron sources. The applications of current commercial neutron generators are often limited by their low neutron yield and their short operational lifetime. A new generation of D-D/D-T fusion-based neutron generators has been designed at Lawrence Berkeley National Laboratory (LBNL) by using high current ion beams hitting on a self-loading target that has a large surface area to dissipate the heat load. This thesis describes the rationale behind the new designs and their potential applications. A survey of other neutron sources is presented to show their advantages and disadvantages compared to the fusion-based neutron generator. A prototype neutron facility was built at LBNL to test these neutron generators. High current ion beams were extracted from an RF-driven ion source to produce neutrons. With an average deuteron beam current of 24 mA and an energy of 100 keV, a neutron yield of >109 n/s has been obtained with a D-D coaxial neutron source. Several potential applications were investigated by using computer simulations. The computer code used for simulations and the variance reduction techniques employed were discussed. A study was carried out to determine the neutron flux and resolution of a D-T neutron source in thermal neutron scattering applications for condensed matter experiments. An error analysis was performed to validate the scheme used to predict the resolution. With a D-T neutron yield of 1014 n/s, the thermal neutron flux at the sample was predicted to be 7.3 x 105 n/cm2s. It was found that the resolution of cold neutrons was better than that of thermal neutrons when the duty factor is high. This neutron generator could be efficiently used for research and educational purposes at universities. Additional applications studied were positron production and Boron Neutron Capture Therapy (BNCT). The neutron flux required for positron production could not be provided with a single D-T neutron generator. Therefore, a subcritical fission multiplier was designed to increase the neutron yield. The neutron flux was increased by a factor of 25. A D-D driven fission multiplier was also studied for BNCT and a gain of 17 was obtained. The fission multiplier system gain was shown to be limited by the neutron absorption in the fuel and the reduction of source brightness. A brief discussion was also given regarding the neutron generator applications for fast neutron brachytherapy and neutron interrogation systems. It was concluded that new designs of compact D-D/D-T neutron generators are feasible and that superior quality neutron beams could be produced and used for various applications.

CORRECTIONS ASSOCIATED WITH ON-PHANTOM CALIBRATIONS OF NEUTRON PERSONAL DOSEMETERS.

PubMed

Hawkes, N P; Thomas, D J; Taylor, G C

2016-09-01

The response of neutron personal dosemeters as a function of neutron energy and angle of incidence is typically measured by mounting the dosemeters on a slab phantom and exposing them to neutrons from an accelerator-based or radionuclide source. The phantom is placed close to the source (75 cm) so that the effect of scattered neutrons is negligible. It is usual to mount several dosemeters on the phantom together. Because the source is close, the source distance and the neutron incidence angle vary significantly over the phantom face, and each dosemeter may receive a different dose equivalent. This is particularly important when the phantom is angled away from normal incidence. With accelerator-produced neutrons, the neutron energy and fluence vary with emission angle relative to the charged particle beam that produces the neutrons, contributing further to differences in dose equivalent, particularly when the phantom is located at other than the straight-ahead position (0° to the beam). Corrections for these effects are quantified and discussed in this article. © Crown copyright 2015.

Characteristics comparison between a cyclotron-based neutron source and KUR-HWNIF for boron neutron capture therapy

NASA Astrophysics Data System (ADS)

Tanaka, H.; Sakurai, Y.; Suzuki, M.; Masunaga, S.; Kinashi, Y.; Kashino, G.; Liu, Y.; Mitsumoto, T.; Yajima, S.; Tsutsui, H.; Maruhashi, A.; Ono, K.

2009-06-01

At Kyoto University Research Reactor Institute (KURRI), 275 clinical trials of boron neutron capture therapy (BNCT) have been performed as of March 2006, and the effectiveness of BNCT has been revealed. In order to further develop BNCT, it is desirable to supply accelerator-based epithermal-neutron sources that can be installed near the hospital. We proposed the method of filtering and moderating fast neutrons, which are emitted from the reaction between a beryllium target and 30-MeV protons accelerated by a cyclotron accelerator, using an optimum moderator system composed of iron, lead, aluminum and calcium fluoride. At present, an epithermal-neutron source is under construction from June 2008. This system consists of a cyclotron accelerator, beam transport system, neutron-yielding target, filter, moderator and irradiation bed. In this article, an overview of this system and the properties of the treatment neutron beam optimized by the MCNPX Monte Carlo neutron transport code are presented. The distribution of biological effect weighted dose in a head phantom compared with that of Kyoto University Research Reactor (KUR) is shown. It is confirmed that for the accelerator, the biological effect weighted dose for a deeply situated tumor in the phantom is 18% larger than that for KUR, when the limit dose of the normal brain is 10 Gy-eq. The therapeutic time of the cyclotron-based neutron sources are nearly one-quarter of that of KUR. The cyclotron-based epithermal-neutron source is a promising alternative to reactor-based neutron sources for treatments by BNCT.

Enhancement of discharge performance of Li/CF x cell by thermal treatment of CF x cathode material

NASA Astrophysics Data System (ADS)

Zhang, Sheng S.; Foster, Donald; Read, Jeffrey

In this work we demonstrate that the thermal treatment of CF x cathode material just below the decomposition temperature can enhance discharge performance of Li/CF x cells. The performance enhancement becomes more effective when heating a mixture of CF x and citric acid (CA) since CA serves as an extra carbon source. Discharge experiments show that the thermal treatment not only reduces initial voltage delay, but also raises discharge voltage. Whereas the measurement of powder impedance indicates the thermal treatment does not increase electronic conductivity of CF x material. Based on these facts, we propose that the thermal treatment results in a limited decomposition of CF x, which yields a subfluorinated carbon (CF x- δ), instead of a highly conductive carbon. In the case of CF x/AC mixture, the AC provides extra carbon that reacts with F 2 and fluorocarbon radicals generated by the thermal decomposition of CF x to form subfluorinated carbon. The process of thermal treatment is studied by thermogravimetric analysis and X-ray diffraction, and the effect of treatment conditions such as heating temperature, heating time and CF x/CA ratio on the discharge performance of CF x cathode is discussed. As an example, a Li/CF x cell using CF x treated with CA at 500 °C under nitrogen for 2 h achieved theretical specific capacity when being discharged at C/5. Impedance analysis indicates that the enhanced performance is attributed to a significant reduction in the cell reaction resistance.

A z-pinch photo-pumped pulsed atomic iodine laser

NASA Astrophysics Data System (ADS)

Stone, D. H.; Saunders, D. P.; Clark, M. C.

1984-03-01

A pulsed atomic iodine laser (CF3I) was designed and constructed using a coaxial xenon flash lamp as a pump source. The flash lamp was operated at low pressure to obtain pulse compression via xenon self-pinch. Electrical and optical diagnostics were performed for various xenon and CF3I pressures. Calorimeter data and burn patterns were obtained for the laser. Time-resolved spectroscopic data were taken throughout the CF3I pump band.

A Targeted Search for Point Sources of EeV Neutrons

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Samarai, I. Al; Albuquerque, I. F. M.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Aramo, C.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Barber, K. B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, B.; Caccianiga, L.; Candusso, M.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Cester, R.; Chavez, A. G.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Colalillo, R.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Criss, A.; Cronin, J.; Curutiu, A.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; de Jong, S. J.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Di Matteo, A.; Diaz, J. C.; Díaz Castro, M. L.; Diep, P. N.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; Dova, M. T.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Fang, K.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fernandes, M.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fox, B. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Fuji, T.; Gaior, R.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Garilli, G.; Gascon Bravo, A.; Gate, F.; Gemmeke, H.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Glaser, C.; Glass, H.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; Gookin, B.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grebe, S.; Griffith, N.; Grillo, A. F.; Grubb, T. D.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Hasankiadeh, Q. D.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Hollon, N.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Isar, P. G.; Islo, K.; Jandt, I.; Jansen, S.; Jarne, C.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kunka, N.; La Rosa, G.; LaHurd, D.; Latronico, L.; Lauer, R.; Lauscher, M.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Malacari, M.; Maldera, S.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, V.; Mariş, I. C.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, A. J.; Matthews, J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Messina, S.; Meyhandan, R.; Mićanović, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morello, C.; Moreno, J. C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, L.; Ochilo, L.; Olinto, A.; Oliveira, M.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Papenbreer, P.; Parente, G.; Parra, A.; Pastor, S.; Paul, T.; Pech, M.; Peķala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Peters, C.; Petrera, S.; Petrolini, A.; Petrov, Y.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porcelli, A.; Porowski, C.; Privitera, P.; Prouza, M.; Purrello, V.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rizi, V.; Roberts, J.; Rodrigues de Carvalho, W.; Rodriguez Cabo, I.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Roulet, E.; Rovero, A. C.; Rühle, C.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarmento, R.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Scholten, O.; Schoorlemmer, H.; Schovánek, P.; Schulz, A.; Schulz, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Squartini, R.; Srivastava, Y. N.; Stanič, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Taborda, O. A.; Tapia, A.; Tartare, M.; Thao, N. T.; Theodoro, V. M.; Tiffenberg, J.; Timmermans, C.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Torralba Elipe, G.; Torres Machado, D.; Travnicek, P.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van den Berg, A. M.; van Velzen, S.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Vlcek, B.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Whelan, B. J.; Widom, A.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Wykes, S.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.; Auger Collaboration101, The Pierre

2014-07-01

A flux of neutrons from an astrophysical source in the Galaxy can be detected in the Pierre Auger Observatory as an excess of cosmic-ray air showers arriving from the direction of the source. To avoid the statistical penalty for making many trials, classes of objects are tested in combinations as nine "target sets," in addition to the search for a neutron flux from the Galactic center or from the Galactic plane. Within a target set, each candidate source is weighted in proportion to its electromagnetic flux, its exposure to the Auger Observatory, and its flux attenuation factor due to neutron decay. These searches do not find evidence for a neutron flux from any class of candidate sources. Tabulated results give the combined p-value for each class, with and without the weights, and also the flux upper limit for the most significant candidate source within each class. These limits on fluxes of neutrons significantly constrain models of EeV proton emission from non-transient discrete sources in the Galaxy.

A route to the brightest possible neutron source?

PubMed

Taylor, Andrew; Dunne, Mike; Bennington, Steve; Ansell, Stuart; Gardner, Ian; Norreys, Peter; Broome, Tim; Findlay, David; Nelmes, Richard

2007-02-23

We review the potential to develop sources for neutron scattering science and propose that a merger with the rapidly developing field of inertial fusion energy could provide a major step-change in performance. In stark contrast to developments in synchrotron and laser science, the past 40 years have seen only a factor of 10 increase in neutron source brightness. With the advent of thermonuclear ignition in the laboratory, coupled to innovative approaches in how this may be achieved, we calculate that a neutron source three orders of magnitude more powerful than any existing facility can be envisaged on a 20- to 30-year time scale. Such a leap in source power would transform neutron scattering science.

Study of neutron generation in the compact tokamak TUMAN-3M in support of a tokamak-based fusion neutron source

NASA Astrophysics Data System (ADS)

Kornev, V. A.; Askinazi, L. G.; Belokurov, A. A.; Chernyshev, F. V.; Lebedev, S. V.; Melnik, A. D.; Shabelsky, A. A.; Tukachinsky, A. S.; Zhubr, N. A.

2017-12-01

The paper presents DD neutron flux measurements in neutron beam injection (NBI) experiments aimed at the optimization of target plasma and heating beam parameters to achieve maximum neutron flux in the TUMAN-3M compact tokamak. Two ion sources of different design were used, which allowed the separation of the beam’s energy and power influence on the neutron rate. Using the database of experiments performed with the two ion sources, an empirical scaling was derived describing the neutron rate dependence on the target plasma and heating beam parameters. Numerical modeling of the neutron rate in the NBI experiments performed using the ASTRA transport code showed good agreement with the scaling.

International workshop on cold neutron sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, G.J.; West, C.D.

1991-08-01

The first meeting devoted to cold neutron sources was held at the Los Alamos National Laboratory on March 5--8, 1990. Cosponsored by Los Alamos and Oak Ridge National Laboratories, the meeting was organized as an International Workshop on Cold Neutron Sources and brought together experts in the field of cold-neutron-source design for reactors and spallation sources. Eighty-four people from seven countries attended. Because the meeting was the first of its kind in over forty years, much time was spent acquainting participants with past and planned activities at reactor and spallation facilities worldwide. As a result, the meeting had more ofmore » a conference flavor than one of a workshop. The general topics covered at the workshop included: Criteria for cold source design; neutronic predictions and performance; energy deposition and removal; engineering design, fabrication, and operation; material properties; radiation damage; instrumentation; safety; existing cold sources; and future cold sources.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nigg, D.W.; Mitchell, H.E.; Harker, Y.D.

Therapeutically-useful epithermal-neutron beams for BNCT are currently generated by nuclear reactors. Various accelerator-based neutron sources for BNCT have been proposed and some low intensity prototypes of such sources, generally featuring the use of proton beams and beryllium or lithium targets have been constructed. This paper describes an alternate approach to the realization of a clinically useful accelerator-based source of epithermal neutrons for BNCT that reconciles the often conflicting objectives of target cooling, neutron beam intensity, and neutron beam spectral purity via a two stage photoneutron production process.

Synfuel production in nuclear reactors

DOEpatents

Henning, C.D.

Apparatus and method for producing synthetic fuels and synthetic fuel components by using a neutron source as the energy source, such as a fusion reactor. Neutron absorbers are disposed inside a reaction pipe and are heated by capturing neutrons from the neutron source. Synthetic fuel feedstock is then placed into contact with the heated neutron absorbers. The feedstock is heated and dissociates into its constituent synfuel components, or alternatively is at least preheated sufficiently to use in a subsequent electrolysis process to produce synthetic fuels and synthetic fuel components.

Apparatus and method for quantitative assay of generic transuranic wastes from nuclear reactors

DOEpatents

Caldwell, J.T.; Kunz, W.E.; Atencio, J.D.

1982-03-31

A combination of passive and active neutron measurements which yields quantitative information about the isotopic composition of transuranic wastes from nuclear power or weapons material manufacture reactors is described. From the measurement of prompt and delayed neutron emission and the incidence of two coincidentally emitted neutrons from induced fission of fissile material in the sample, one can quantify /sup 233/U, /sup 235/U and /sup 239/Pu isotopes in waste samples. Passive coincidence counting, including neutron multiplicity measurement and determination of the overall passive neutron flux additionally enables the separate quantitative evaluation of spontaneous fission isotopes such as /sup 240/Pu, /sup 244/Cm and /sup 252/Cf, and the spontaneous alpha particle emitter /sup 241/Am. These seven isotopes are the most important constituents of wastes from nuclear power reactors and once the mass of each isotope present is determined by the apparatus and method of the instant invention, the overall alpha particle activity can be determined to better than 1 nCi/g from known radioactivity data. Therefore, in addition to the quantitative analysis of the waste sample useful for later reclamation purposes, the alpha particle activity can be determined to decide whether permanent low-level burial is appropriate for the waste sample.

Apparatus and method for quantitative assay of generic transuranic wastes from nuclear reactors

DOEpatents

Caldwell, John T.; Kunz, Walter E.; Atencio, James D.

1984-01-01

A combination of passive and active neutron measurements which yields quantitative information about the isotopic composition of transuranic wastes from nuclear power or weapons material manufacture reactors is described. From the measurement of prompt and delayed neutron emission and the incidence of two coincidentally emitted neutrons from induced fission of fissile material in the sample, one can quantify .sup.233 U, .sup.235 U and .sup.239 Pu isotopes in waste samples. Passive coincidence counting, including neutron multiplicity measurement and determination of the overall passive neutron flux additionally enables the separate quantitative evaluation of spontaneous fission isotopes such as .sup.240 Pu, .sup.244 Cm and .sup.252 Cf, and the spontaneous alpha particle emitter .sup.241 Am. These seven isotopes are the most important constituents of wastes from nuclear power reactors and once the mass of each isotope present is determined by the apparatus and method of the instant invention, the overall alpha particle activity can be determined to better than 1 nCi/g from known radioactivity data. Therefore, in addition to the quantitative analysis of the waste sample useful for later reclamation purposes, the alpha particle activity can be determined to decide whether "permanent" low-level burial is appropriate for the waste sample.

Fast fission neutron detection using the Cherenkov effect

NASA Astrophysics Data System (ADS)

Millard, Matthew James

The Cherenkov effect in optically clear media of varying indices of refraction and composition was investigated for quantification of fast neutrons. The ultimate application of the proposed detection system is criticality monitoring. The optically clear medium, composed of select target nuclei, was coupled to a photomultiplier tube. Neutron reaction products of the target nuclei contained within the optical medium emit beta particles and gamma rays that produce Cherenkov photons within the medium which can be detected. Assessed media include quartz (SiO2), sapphire (Al2O3), spinel (MgAl2O4), and zinc sulfide (ZnS), which were irradiated with un-moderated 252Cf. Monte Carlo N-Particle (MCNP) code simulations were conducted to quantify the neutron flux incident on the media. High resolution gamma-ray spectroscopic measurements of the samples were conducted to verify the MCNP estimate. The threshold reactions of interest were 28Si (n, p) 28Al, 27 Al (n, p) 27Mg, 24Mg(n, p)24 Na, and 64Zn(n, p)64Cu which have neutron reaction cross sections in the 1 to 10 MeV range on the order of 0.1 barn. The detection system offers a unique way to measure a criticality event; it can count in place, making retrieval by emergency personnel unnecessary.

Estimation of Confidence Intervals for Multiplication and Efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verbeke, J

2009-07-17

Helium-3 tubes are used to detect thermal neutrons by charge collection using the {sup 3}He(n,p) reaction. By analyzing the time sequence of neutrons detected by these tubes, one can determine important features about the constitution of a measured object: Some materials such as Cf-252 emit several neutrons simultaneously, while others such as uranium and plutonium isotopes multiply the number of neutrons to form bursts. This translates into unmistakable signatures. To determine the type of materials measured, one compares the measured count distribution with the one generated by a theoretical fission chain model. When the neutron background is negligible, the theoreticalmore » count distributions can be completely characterized by a pair of parameters, the multiplication M and the detection efficiency {var_epsilon}. While the optimal pair of M and {var_epsilon} can be determined by existing codes such as BigFit, the uncertainty on these parameters has not yet been fully studied. The purpose of this work is to precisely compute the uncertainties on the parameters M and {var_epsilon}, given the uncertainties in the count distribution. By considering different lengths of time tagged data, we will determine how the uncertainties on M and {var_epsilon} vary with the different count distributions.« less

Bayesian estimation of dose thresholds

NASA Technical Reports Server (NTRS)

Groer, P. G.; Carnes, B. A.

2003-01-01

An example is described of Bayesian estimation of radiation absorbed dose thresholds (subsequently simply referred to as dose thresholds) using a specific parametric model applied to a data set on mice exposed to 60Co gamma rays and fission neutrons. A Weibull based relative risk model with a dose threshold parameter was used to analyse, as an example, lung cancer mortality and determine the posterior density for the threshold dose after single exposures to 60Co gamma rays or fission neutrons from the JANUS reactor at Argonne National Laboratory. The data consisted of survival, censoring times and cause of death information for male B6CF1 unexposed and exposed mice. The 60Co gamma whole-body doses for the two exposed groups were 0.86 and 1.37 Gy. The neutron whole-body doses were 0.19 and 0.38 Gy. Marginal posterior densities for the dose thresholds for neutron and gamma radiation were calculated with numerical integration and found to have quite different shapes. The density of the threshold for 60Co is unimodal with a mode at about 0.50 Gy. The threshold density for fission neutrons declines monotonically from a maximum value at zero with increasing doses. The posterior densities for all other parameters were similar for the two radiation types.

A large 2D PSD for thermal neutron detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knott, R.B.; Watt, G.; Boldeman, J.W.

1996-12-31

A 2D PSD based on a MWPC has been constructed for a small angle neutron scattering instrument. The active area of the detector was 640 x 640 mm{sup 2}. To meet the specifications for neutron detection efficiency and spatial resolution, and to minimize parallax, the gas mixture was 190 kPa {sup 3}He plus 100 kPa CF{sub 4} and the active volume had a thickness of 30 mm. The design maximum neutron count-rate of the detector was 10{sup 5} events per second. The (calculated) neutron detection efficiency was 60% for 2{angstrom} neutrons and the (measured) neutron energy resolution on the anodemore » grid was typically 20% (fwhm). The location of a neutron detection event within the active area was determined using the wire-by-wire method: the spatial resolution (5 x 5 mm{sup 2}) was thereby defined by the wire geometry. A 16 channel charge-sensitive preamplifier/amplifier/comparator module has been developed with a channel sensitivity of 0.1 V/fC, noise linewidth of 0.4 fC (fwhm) and channel-to-channel cross-talk of less than 5%. The Proportional Counter Operating System (PCOS III) (LeCroy Corp USA) was used for event encoding. The ECL signals produced by the 16 channel modules were latched in PCOS III by a trigger pulse from the anode and the fast encoders produce a position and width for each event. The information was transferred to a UNIX workstation for accumulation and online display.« less

D-D neutron generator development at LBNL.

PubMed

Reijonen, J; Gicquel, F; Hahto, S K; King, M; Lou, T-P; Leung, K-N

2005-01-01

The plasma and ion source technology group in Lawrence Berkeley National Laboratory is developing advanced, next generation D-D neutron generators. There are three distinctive developments, which are discussed in this presentation, namely, multi-stage, accelerator-based axial neutron generator, high-output co-axial neutron generator and point source neutron generator. These generators employ RF-induction discharge to produce deuterium ions. The distinctive feature of RF-discharge is its capability to generate high atomic hydrogen species, high current densities and stable and long-life operation. The axial neutron generator is designed for applications that require fast pulsing together with medium to high D-D neutron output. The co-axial neutron generator is aimed for high neutron output with cw or pulsed operation, using either the D-D or D-T fusion reaction. The point source neutron generator is a new concept, utilizing a toroidal-shaped plasma generator. The beam is extracted from multiple apertures and focus to the target tube, which is located at the middle of the generator. This will generate a point source of D-D, T-T or D-T neutrons with high output flux. The latest development together with measured data will be discussed in this article.

Accelerating fissile material detection with a neutron source

DOEpatents

Rowland, Mark S.; Snyderman, Neal J.

2018-01-30

A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly to count neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source. The system includes a Poisson neutron generator for in-beam interrogation of a possible fissile neutron source and a DC power supply that exhibits electrical ripple on the order of less than one part per million. Certain voltage multiplier circuits, such as Cockroft-Walton voltage multipliers, are used to enhance the effective of series resistor-inductor circuits components to reduce the ripple associated with traditional AC rectified, high voltage DC power supplies.

Fusion pumped laser

DOEpatents

Pappas, D.S.

1987-07-31

The apparatus of this invention may comprise a system for generating laser radiation from a high-energy neutron source. The neutron source is a tokamak fusion reactor generating a long pulse of high-energy neutrons and having a temperature and magnetic field effective to generate a neutron flux of at least 10/sup 15/ neutrons/cm/sup 2//center dot/s. Conversion means are provided adjacent the fusion reactor at a location operable for converting the high-energy neutrons to an energy source with an intensity and energy effective to excite a preselected lasing medium. A lasing medium is spaced about and responsive to the energy source to generate a population inversion effective to support laser oscillations for generating output radiation. 2 figs., 2 tabs.

Sensitivity Studies and Experimental Evaluation for Optimizing Transcurium Isotope Production

DOE PAGES

Hogle, Susan L.; Alexander, Charles W.; Burns, Jonathan D.; ...

2017-03-01

This work applies to recent initiatives at the Radiochemical Engineering Development Center at Oak Ridge National Laboratory to optimize the production of transcurium isotopes in the High Flux Isotope Reactor in such a way as to prolong the use of high quality heavy curium feedstock. By studying the sensitivity of fission and transmutation reaction rates to the neutron flux spectrum a means of increasing the fraction of (n,γ) reactions per neutron absorption is explored. Filter materials which preferentially absorb neutrons at energies considered detrimental to optimal transcurium production are identified and transmutation rates are examined with high energy resolution. Experimentalmore » capsules are irradiated employing filter materials and the resulting fission and activation products studied to validate the filtering methodology. Improvement is seen in the production efficiency of heavier curium isotopes in 244Cm and 245Cm targets, and potentially in production of 252Cf from mixed californium targets. Finally, further analysis is recommended to evaluate longer duration irradiations more representative of typical transcurium production.« less

Phase 3 experiments of the JAERI/USDOE collaborative program on fusion blanket neutronics. Volume 1: Experiment

NASA Astrophysics Data System (ADS)

Oyama, Yukio; Konno, Chikara; Ikeda, Yujiro; Maekawa, Fujio; Kosako, Kazuaki; Nakamura, Tomoo; Maekawa, Hiroshi; Youssef, Mahmoud Z.; Kumar, Anil; Abdou, Mohamed A.

1994-02-01

A pseudo-line source has been realized by using an accelerator based D-T point neutron source. The pseudo-line source is obtained by time averaging of continuously moving point source or by superposition of finely distributed point sources. The line source is utilized for fusion blanket neutronics experiments with an annular geometry so as to simulate a part of a tokamak reactor. The source neutron characteristics were measured for two operational modes for the line source, continuous and step-wide modes, with the activation foil and the NE213 detectors, respectively. In order to give a source condition for a successive calculational analysis on the annular blanket experiment, the neutron source characteristics was calculated by a Monte Carlo code. The reliability of the Monte Carlo calculation was confirmed by comparison with the measured source characteristics. The shape of the annular blanket system was a rectangular with an inner cavity. The annular blanket was consist of 15 mm-thick first wall (SS304) and 406 mm-thick breeder zone with Li2O at inside and Li2CO3 at outside. The line source was produced at the center of the inner cavity by moving the annular blanket system in the span of 2 m. Three annular blanket configurations were examined; the reference blanket, the blanket covered with 25 mm thick graphite armor and the armor-blanket with a large opening. The neutronics parameters of tritium production rate, neutron spectrum and activation reaction rate were measured with specially developed techniques such as multi-detector data acquisition system, spectrum weighting function method and ramp controlled high voltage system. The present experiment provides unique data for a higher step of benchmark to test a reliability of neutronics design calculation for a realistic tokamak reactor.

Assessment of the neutron cross section database for mercury for the ORNL spallation source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leal, L.C.; Spencer, R.R.; Ingersoll, D.T.

1996-06-01

Neutron source generation based on a high energy particle accelerator has been considered as an alternative to the canceled Advanced Neutron Source project at Oak Ridge National Laboratory. The proposed technique consists of a spallation neutron source in which neutrons are produced via the interaction of high-energy charged particles in a heavy metal target. Preliminary studies indicate that liquid mercury bombarded with GeV protons provides an excellent neutron source. Accordingly, a survey has been made of the available neutron cross-section data. Since it is expected that spectral modifiers, specifically moderators, will also be incorporated into the source design, the surveymore » included thermal energy, resonance region, and high energy data. It was found that data of individual isotopes were almost non-existent and that the only evaluation found for the natural element had regions of missing data or discrepant data. Therefore, it appears that to achieve the desired degree of accuracy in the spallation source design it is necessary to re-evaluate the mercury database including making new measurements. During the presentation the currently available data will be presented and experiments proposed which can lead to design quality cross sections.« less

Beam shaping assembly of a D-T neutron source for BNCT and its dosimetry simulation in deeply-seated tumor

NASA Astrophysics Data System (ADS)

Faghihi, F.; Khalili, S.

2013-08-01

This article involves two aims for BNCT. First case includes a beam shaping assembly estimation for a D-T neutron source to find epi-thermal neutrons which are the goal in the BNCT. Second issue is the percent depth dose calculation in the adult Snyder head phantom. Monte-Carlo simulations and verification of a suggested beam shaping assembly (including internal neutron multiplier, moderator, filter, external neutron multiplier, collimator, and reflector dimensions) for thermalizing a D-T neutron source as well as increasing neutron flux are carried out and our results are given herein. Finally, we have simulated its corresponding doses for treatment planning of a deeply-seated tumor.

Characterization of the neutron irradiation system for use in the Low-Dose-Rate Irradiation Facility at Sandia National Laboratories.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franco, Manuel

The objective of this work was to characterize the neutron irradiation system consisting of americium-241 beryllium (241AmBe) neutron sources placed in a polyethylene shielding for use at Sandia National Laboratories (SNL) Low Dose Rate Irradiation Facility (LDRIF). With a total activity of 0.3 TBq (9 Ci), the source consisted of three recycled 241AmBe sources of different activities that had been combined into a single source. The source in its polyethylene shielding will be used in neutron irradiation testing of components. The characterization of the source-shielding system was necessary to evaluate the radiation environment for future experiments. Characterization of the sourcemore » was also necessary because the documentation for the three component sources and their relative alignment within the Special Form Capsule (SFC) was inadequate. The system consisting of the source and shielding was modeled using Monte Carlo N-Particle transport code (MCNP). The model was validated by benchmarking it against measurements using multiple techniques. To characterize the radiation fields over the full spatial geometry of the irradiation system, it was necessary to use a number of instruments of varying sensitivities. First, the computed photon radiography assisted in determining orientation of the component sources. With the capsule properly oriented inside the shielding, the neutron spectra were measured using a variety of techniques. A N-probe Microspec and a neutron Bubble Dosimeter Spectrometer (BDS) set were used to characterize the neutron spectra/field in several locations. In the third technique, neutron foil activation was used to ascertain the neutron spectra. A high purity germanium (HPGe) detector was used to characterize the photon spectrum. The experimentally measured spectra and the MCNP results compared well. Once the MCNP model was validated to an adequate level of confidence, parametric analyses was performed on the model to optimize for potential experimental configurations and neutron spectra for component irradiation. The final product of this work is a MCNP model validated by measurements, an overall understanding of neutron irradiation system including photon/neutron transport and effective dose rates throughout the system, and possible experimental configurations for future irradiation of components.« less

Prompt-gamma neutron activation analysis system design: Effects of D-T versus D-D neutron generator source selection

USDA-ARS?s Scientific Manuscript database

Prompt-gamma neutron activation (PGNA) analysis is used for the non-invasive measurement of human body composition. Advancements in portable, compact neutron generator design have made those devices attractive as neutron sources. Two distinct generators are available: D-D with 2.5 MeV and D-T with...

Measurement of the ambient gamma dose equivalent and kerma from the small 252Cf source at 1 meter and the small 60Co source at 2 meters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carl, W. F.

NASA Langley Research Center requested a measurement and determination of the ambient gamma dose equivalent rate and kerma at 100 cm from the 252Cf source and determination of the ambient gamma dose equivalent rate and kerma at 200 cm from the 60Co source for the Radiation Budget Instrument Experiment (Rad-X). An Exradin A6 ion chamber with Shonka air-equivalent plastic walls in combination with a Supermax electrometer were used to measure the exposure rate and free-in-air kerma rate of the two sources at the requested distances. The measured gamma exposure, kerma, and dose equivalent rates are tabulated.

The design of a multisource americium-beryllium (Am-Be) neutron irradiation facility using MCNP for the neutronic performance calculation.

PubMed

Sogbadji, R B M; Abrefah, R G; Nyarko, B J B; Akaho, E H K; Odoi, H C; Attakorah-Birinkorang, S

2014-08-01

The americium-beryllium neutron irradiation facility at the National Nuclear Research Institute (NNRI), Ghana, was re-designed with four 20 Ci sources using Monte Carlo N-Particle (MCNP) code to investigate the maximum amount of flux that is produced by the combined sources. The results were compared with a single source Am-Be irradiation facility. The main objective was to enable us to harness the maximum amount of flux for the optimization of neutron activation analysis and to enable smaller sample sized samples to be irradiated. Using MCNP for the design construction and neutronic performance calculation, it was realized that the single-source Am-Be design produced a thermal neutron flux of (1.8±0.0007)×10(6) n/cm(2)s and the four-source Am-Be design produced a thermal neutron flux of (5.4±0.0007)×10(6) n/cm(2)s which is a factor of 3.5 fold increase compared to the single-source Am-Be design. The criticality effective, k(eff), of the single-source and the four-source Am-Be designs were found to be 0.00115±0.0008 and 0.00143±0.0008, respectively. Copyright © 2014 Elsevier Ltd. All rights reserved.

Development of An Epi-thermal Neutron Field for Fundamental Researches for BNCT with A DT Neutron Source

NASA Astrophysics Data System (ADS)

Osawa, Yuta; Imoto, Shoichi; Kusaka, Sachie; Sato, Fuminobu; Tanoshita, Masahiro; Murata, Isao

2017-09-01

Boron Neutron Capture Therapy (BNCT) is known to be a new promising cancer therapy suppressing influence against normal cells. In Japan, Accelerator Based Neutron Sources (ABNS) are being developed for BNCT. For the spread of ABNS based BNCT, we should characterize the neutron field beforehand. For this purpose, we have been developing a low-energy neutron spectrometer based on 3He position sensitive proportional counter. In this study, a new intense epi-thermal neutron field was developed with a DT neutron source for verification of validity of the spectrometer. After the development, the neutron field characteristics were experimentally evaluated by using activation foils. As a result, we confirmed that an epi-thermal neutron field was successfully developed suppressing fast neutrons substantially. Thereafter, the neutron spectrometer was verified experimentally. In the verification, although a measured detection depth distribution agreed well with the calculated distribution by MCNP, the unfolded spectrum was significantly different from the calculated neutron spectrum due to contribution of the side neutron incidence. Therefore, we designed a new neutron collimator consisting of a polyethylene pre-collimator and boron carbide neutron absorber and confirmed numerically that it could suppress the side incident neutrons and shape the neutron flux to be like a pencil beam.

A compact neutron scatter camera for field deployment

DOE PAGES

Goldsmith, John E. M.; Gerling, Mark D.; Brennan, James S.

2016-08-23

Here, we describe a very compact (0.9 m high, 0.4 m diameter, 40 kg) battery operable neutron scatter camera designed for field deployment. Unlike most other systems, the configuration of the sixteen liquid-scintillator detection cells are arranged to provide omnidirectional (4π) imaging with sensitivity comparable to a conventional two-plane system. Although designed primarily to operate as a neutron scatter camera for localizing energetic neutron sources, it also functions as a Compton camera for localizing gamma sources. In addition to describing the radionuclide source localization capabilities of this system, we demonstrate how it provides neutron spectra that can distinguish plutonium metalmore » from plutonium oxide sources, in addition to the easier task of distinguishing AmBe from fission sources.« less

Neutron Radiation Characteristics of Plutonium Dioxide Fuel

NASA Technical Reports Server (NTRS)

Taherzadeh, M.

1972-01-01

The major sources of neutrons from plutonium dioxide nuclear fuel are considered in detail. These sources include spontaneous fission of several of the Pu isotopes, reactions with low Z impurities in the fuel, and reactions with O-18. For spontaneous fission neutrons a value of (1.95 plus or minus 0.07) X 1,000 n/s/q PuO2 is obtained. The neutron yield from (alpha, neutron) reactions with oxygen is calculated by integrating the reaction rate equation over all alpha particle energies and all center-of-mass angles. The results indicate a neutron emission rate of (1.42 plus or minus 0.32) X 10,000 n/s/q PuO2. The neutron yield from (alpha, neutron) reactions with low Z impurities in the fuel is presented in tabular form for one part per million of each impurity. The total neutron flux emitted from a particular fuel geometry is estimated by adding the neutron yield due to the induced fission to the other neutron sources.

Measurements of the total cross section of natBe with thermal neutrons from a photo-neutron source

NASA Astrophysics Data System (ADS)

Liu, L. X.; Wang, H. W.; Ma, Y. G.; Cao, X. G.; Cai, X. Z.; Chen, J. G.; Zhang, G. L.; Han, J. L.; Zhang, G. Q.; Hu, J. F.; Wang, X. H.; Li, W. J.; Yan, Z.; Fu, H. J.

2017-11-01

The total neutron cross sections of natural beryllium in the neutron energy region of 0.007 to 0.1 eV were measured by using a time-of-flight (TOF) technique at the Shanghai Institute of Applied Physics (SINAP). The low energy neutrons were obtained by moderating the high energy neutrons from a pulsed photo-neutron source generated from a 16 MeV electron linac. The time dependent neutron background component was determined by employing the 12.8 cm boron-loaded polyethylene (PEB) (5% w.t.) to block neutron TOF path and using the Monte Carlo simulation methods. The present data was compared with the fold Harvey data with the response function of the photo-neutron source (PNS, phase-1). The present measurement of total cross section of natBe for thermal neutrons based on PNS has been developed for the acquisition of nuclear data needed for the Thorium Molten Salt Reactor (TMSR).

CRADA Final Report for CRADA Number NFE-08-01671 Materials for Advanced Turbocharger Designs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maziasz, P. J.; Wilson, M.

2014-11-28

Results were obtained on residual stresses in the weld of the steel shaft to the Ni-based superalloy turbine wheel for turbochargers. Neutron diffraction studies at the HFIR Residual Stress Facility showed asymmetric tensile stresses after electron-beam welding of the wheel and shaft. A post-weld heat-treatment was found to relieve and reduce the residual stresses. Results were also obtained on cast CF8C-Plus steel as an upgrade alternative to cast irons (SiMo, Ni-resist) for higher temperature capability and performance for the turbocharger housing. CF8C-Plus steel has demonstrated creep-rupture resistance at 600-950oC, and is more creep-resistant than HK30Nb, but lacks oxidation-resistance at 800oCmore » and above in 10% water vapor. New modified CF8C-Plus Cu/W steels with Cr and Ni additions show better oxidation resistance at 800oC in 10% water vapor, and have capability to higher temperatures. For automotive gasoline engine turbocharger applications, higher temperatures are required, so at the end of this project, testing began at 1000oC and above.« less

New method of a "point-like" neutron source creation based on sharp focusing of high-current deuteron beam onto deuterium-saturated target for neutron tomography

NASA Astrophysics Data System (ADS)

Golubev, S.; Skalyga, V.; Izotov, I.; Sidorov, A.

2017-02-01

A possibility of a compact powerful point-like neutron source creation is discussed. Neutron yield of the source based on deuterium-deuterium (D-D) reaction is estimated at the level of 1011 s-1 (1013 s-1 for deuterium-tritium reaction). The fusion takes place due to bombardment of deuterium- (or tritium) loaded target by high-current focused deuterium ion beam with energy of 100 keV. The ion beam is formed by means of high-current quasi-gasdynamic ion source of a new generation based on an electron cyclotron resonance (ECR) discharge in an open magnetic trap sustained by powerful microwave radiation. The prospects of proposed generator for neutron tomography are discussed. Suggested method is compared to the point-like neutron sources based on a spark produced by powerful femtosecond laser pulses.

Program of Fundamental-Interaction Research for the Ultracold-Neutron Source at the the WWR-M Reactor

NASA Astrophysics Data System (ADS)

Serebrov, A. P.

2018-03-01

The use of ultracold neutrons opens unique possibilities for studying fundamental interactions in particles physics. Searches for the neutron electric dipole moment are aimed at testing models of CP violation. A precise measurement of the neutron lifetime is of paramount importance for cosmology and astrophysics. Considerable advances in these realms can be made with the aid of a new ultracold-neutron (UCN) supersource presently under construction at Petersburg Nuclear Physics Institute. With this source, it would be possible to obtain an UCN density approximately 100 times as high as that at currently the best UCN source at the high-flux reactor of the Institute Laue-Langevin (ILL, Grenoble, France). To date, the design and basic elements of the source have been prepared, tests of a full-scale source model have been performed, and the research program has been developed. It is planned to improve accuracy in measuring the neutron electric dipole moment by one order of magnitude to a level of 10-27 to 10-28 e cm. This is of crucial importance for particle physics. The accuracy in measuring the neutron lifetime can also be improved by one order of magnitude. Finally, experiments that would seek neutron-antineutron oscillations by employing ultracold neutrons will become possible upon reaching an UCN density of 103 to 104 cm-3. The current status of the source and the proposed research program are discussed.

Development of Measurement Methods for Detection of Special Nuclear Materials using D-D Pulsed Neutron Source

NASA Astrophysics Data System (ADS)

Misawa, Tsuyoshi; Takahashi, Yoshiyuki; Yagi, Takahiro; Pyeon, Cheol Ho; Kimura, Masaharu; Masuda, Kai; Ohgaki, Hideaki

2015-10-01

For detection of hidden special nuclear materials (SNMs), we have developed an active neutron-based interrogation system combined with a D-D fusion pulsed neutron source and a neutron detection system. In the detection scheme, we have adopted new measurement techniques simultaneously; neutron noise analysis and neutron energy spectrum analysis. The validity of neutron noise analysis method has been experimentally studied in the Kyoto University Critical Assembly (KUCA), and was applied to a cargo container inspection system by simulation.

Simulated and measured neutron/gamma light output distribution for poly-energetic neutron/gamma sources

NASA Astrophysics Data System (ADS)

Hosseini, S. A.; Zangian, M.; Aghabozorgi, S.

2018-03-01

In the present paper, the light output distribution due to poly-energetic neutron/gamma (neutron or gamma) source was calculated using the developed MCNPX-ESUT-PE (MCNPX-Energy engineering of Sharif University of Technology-Poly Energetic version) computational code. The simulation of light output distribution includes the modeling of the particle transport, the calculation of scintillation photons induced by charged particles, simulation of the scintillation photon transport and considering the light resolution obtained from the experiment. The developed computational code is able to simulate the light output distribution due to any neutron/gamma source. In the experimental step of the present study, the neutron-gamma discrimination based on the light output distribution was performed using the zero crossing method. As a case study, 241Am-9Be source was considered and the simulated and measured neutron/gamma light output distributions were compared. There is an acceptable agreement between the discriminated neutron/gamma light output distributions obtained from the simulation and experiment.

Deuterium-lithium plasma as a source of fusion neutrons

NASA Astrophysics Data System (ADS)

Chirkov, A. Yu; Vesnin, V. R.

2017-11-01

The concepts of deuterium-tritium (D-T) fusion neutron source are currently developed for hybrid fusion-fission systems and the waste transmutation ones. The need to use tritium technologies is a deterrent factor in this promising direction of energy production. Potential possibilities of using systems that do not require tritium developments are of a significant interest. A deuterium-deuterium (D-D) reaction is considered for the use in demonstration fusion neutron sources. The product of this reaction is tritium, which will burn in the plasma with the emission of fast neutrons. D-D reaction is significantly slower then D-T reaction. Present study shows an increase in neutron yield using a powerful injection of the beam of deuterium atoms. The reactions of the deuterium with lithium isotopes are considered. In some of these reactions, fast neutrons can be obtained. The results of the calculation of the neutron yield from the deuterium lithium plasma are discussed. The estimates of the parameters needed for the realization of a source of fusion neutrons are presented.

New band structures in Neutron-Rich Mo and Ru Isotopes

DOE PAGES

Hamilton, J. H.; Luoa, Y. X.; Zhu, S. J.; ...

2009-01-01

Rotational bands in 110,112Ru and 108Mo have been investigated by means of γ-γ-γ and γ-γ(θ) coincidences of prompt γ rays emitted in the spontaneous fission of 252Cf. New ΔI = 1 negative parity doublet bands are found. These bands in 110,112Ru and 108Mo have all the properties expected for chiral vibrations. Microscopic calculations that combine the TAC meanfield with random phase approximation support this interpretation.

Synthesis of superheavy elements at the Dubna gas-filled recoil separator

NASA Astrophysics Data System (ADS)

Voinov, A. A.

2016-12-01

A survey of experiments at the Dubna gas-filled recoil separator (Laboratory of Nuclear Reactions, JINR, Dubna) aimed at the detection and study of the "island of stability" of superheavy nuclei produced in complete fusion reactions of 48Ca ions and 238U-249Cf target nuclei is given. The problems of synthesis of superheavy nuclei, methods for their identification, and investigation of their decay properties, including the results of recent experiments at other separators (SHIP, BGS, TASCA) and chemical setups, are discussed. The studied properties of the new nuclei, the isotopes of elements 112-118, as well as the properties of their decay products, indicate substantial growth of stability of the heaviest nuclei with increasing number of neutrons in the nucleus as the magic number of neutrons N = 184 is approached.

The 11/2{sup -}[505] neutron extruder orbital in {sup 159}Sm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urban, W.; Faculty of Physics, University of Warsaw, ul. Hoza 69, PL-00-681 Warsaw; Pinston, J. A.

Excited states in {sup 159}Sm, populated following the spontaneous fission of {sup 252}Cf have been studied by means of {gamma} spectroscopy, using the Gammasphere array. In {sup 159}Sm we have identified an isomeric level with a half-life of T{sub 1/2}=116(8) ns at an excitation energy of 1276.8 keV and observed a rotational band on top of this isomer. On the basis of the observed properties of the isomer and the band on top of it we propose that the 1276.8-keV level in {sup 159}Sm corresponds to the 11/2{sup -}[505] neutron extruder configuration. The new excitation scheme of {sup 159}Sm ismore » compared to quasiparticle rotor model calculations.« less

Neutron source

DOEpatents

Cason, J.L. Jr.; Shaw, C.B.

1975-10-21

A neutron source which is particularly useful for neutron radiography consists of a vessel containing a moderating media of relatively low moderating ratio, a flux trap including a moderating media of relatively high moderating ratio at the center of the vessel, a shell of depleted uranium dioxide surrounding the moderating media of relatively high moderating ratio, a plurality of guide tubes each containing a movable source of neutrons surrounding the flux trap, a neutron shield surrounding one part of each guide tube, and at least one collimator extending from the flux trap to the exterior of the neutron source. The shell of depleted uranium dioxide has a window provided with depleted uranium dioxide shutters for each collimator. Reflectors are provided above and below the flux trap and on the guide tubes away from the flux trap.

Detecting Shielded Special Nuclear Materials Using Multi-Dimensional Neutron Source and Detector Geometries

NASA Astrophysics Data System (ADS)

Santarius, John; Navarro, Marcos; Michalak, Matthew; Fancher, Aaron; Kulcinski, Gerald; Bonomo, Richard

2016-10-01

A newly initiated research project will be described that investigates methods for detecting shielded special nuclear materials by combining multi-dimensional neutron sources, forward/adjoint calculations modeling neutron and gamma transport, and sparse data analysis of detector signals. The key tasks for this project are: (1) developing a radiation transport capability for use in optimizing adaptive-geometry, inertial-electrostatic confinement (IEC) neutron source/detector configurations for neutron pulses distributed in space and/or phased in time; (2) creating distributed-geometry, gas-target, IEC fusion neutron sources; (3) applying sparse data and noise reduction algorithms, such as principal component analysis (PCA) and wavelet transform analysis, to enhance detection fidelity; and (4) educating graduate and undergraduate students. Funded by DHS DNDO Project 2015-DN-077-ARI095.

Investigation of some possible changes in Am-Be neutron source configuration in order to increase the thermal neutron flux using Monte Carlo code

NASA Astrophysics Data System (ADS)

Basiri, H.; Tavakoli-Anbaran, H.

2018-01-01

Am-Be neutrons source is based on (α, n) reaction and generates neutrons in the energy range of 0-11 MeV. Since the thermal neutrons are widely used in different fields, in this work, we investigate how to improve the source configuration in order to increase the thermal flux. These suggested changes include a spherical moderator instead of common cylindrical geometry, a reflector layer and an appropriate materials selection in order to achieve the maximum thermal flux. All calculations were done by using MCNP1 Monte Carlo code. Our final results indicated that a spherical paraffin moderator, a layer of beryllium as a reflector can efficiently increase the thermal neutron flux of Am-Be source.

Characterization of the Multi-Blade 10B-based detector at the CRISP reflectometer at ISIS for neutron reflectometry at ESS

NASA Astrophysics Data System (ADS)

Piscitelli, F.; Mauri, G.; Messi, F.; Anastasopoulos, M.; Arnold, T.; Glavic, A.; Höglund, C.; Ilves, T.; Lopez Higuera, I.; Pazmandi, P.; Raspino, D.; Robinson, L.; Schmidt, S.; Svensson, P.; Varga, D.; Hall-Wilton, R.

2018-05-01

The Multi-Blade is a Boron-10-based gaseous thermal neutron detector developed to face the challenge arising in neutron reflectometry at neutron sources. Neutron reflectometers are challenging instruments in terms of instantaneous counting rate and spatial resolution. This detector has been designed according to the requirements given by the reflectometers at the European Spallation Source (ESS) in Sweden. The Multi-Blade has been installed and tested on the CRISP reflectometer at the ISIS neutron and muon source in U.K.. The results on the detailed detector characterization are discussed in this manuscript.

Active Interrogation of Sensitive Nuclear Material Using Laser Driven Neutron Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Favalli, Andrea; Roth, Markus

2015-05-01

An investigation of the viability of a laser-driven neutron source for active interrogation is reported. The need is for a fast, movable, operationally safe neutron source which is energy tunable and has high-intensity, directional neutron production. Reasons for the choice of neutrons and lasers are set forth. Results from the interrogation of an enriched U sample are shown.

Radioprotective effects of cimetidine on rats irradiated by long-term, low-dose-rate neutrons and 60Co γ-rays.

PubMed

Jiang, Ding-Wen; Wang, Qing-Rong; Shen, Xian-Rong; He, Ying; Qian, Tian-Tian; Liu, Qiong; Hou, Deng-Yong; Liu, Yu-Ming; Chen, Wei; Ren, Xin; Li, Ke-Xian

2017-01-01

Cimetidine, an antagonist of histamine type II receptors, has shown protective effects against γ-rays or neutrons. However, there have been no reports on the effects of cimetidine against neutrons combined with γ-rays. This study was carried out to evaluate the protective effects of cimetidine on rats exposed to long-term, low-dose-rate neutron and γ-ray combined irradiation (n-γ LDR). Fifty male Sprague-Dawley (SD) rats were randomly divided into 5 groups: the normal control group, radiation model group, 20 mg/(kg · d) cimetidine group, 80 mg/(kg · d) cimetidine group and 160 mg/(kg · d) cimetidine group (10 rats per group). Except for the normal control group, 40 rats were simultaneously exposed to fission neutrons ( 252 Cf, 0.085 mGy/h) for 22 h every day and γ-rays ( 60 Co, 0.097 Gy/h) for 1.03 h once every three days, and the cimetidine groups were administered intragastrically with cimetidine at doses of 20, 80 and 160 mg/kg each day. Peripheral blood WBC of the rats was counted the day following exposure to γ-rays. The rats were anesthetized and sacrificed on the day following exposure to 252 Cf for 28 days. The spleen, thymus, testicle, liver and intestinal tract indexes were evaluated. The DNA content of bone marrow cells and concanavalin A (ConA)-induced lymphocyte proliferation were measured. The frequency of micronuclei in polychromatic erythrocytes (fMNPCEs), superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px) in the serum and liver tissues were detected. The peripheral blood WBC in the cimetidine groups was increased significantly on the 8th day and the 26th day compared with those in the radiation model group. The spleen, thymus and testicle indexes of the cimetidine groups were higher than those of the radiation model group. The DNA content of bone marrow cells and lymphocyte proliferation in the cimetidine groups were increased significantly, and fMNPCE was reduced 1.41-1.77 fold in cimetidine treated groups. The activities of SOD and GSH-Px in the cimetidine groups were increased significantly, and the content of MDA in the cimetidine groups was decreased significantly. The results suggested that cimetidine alleviated damage induced by long-term, low-dose-rate neutron and γ combined irradiation via antioxidation and immunomodulation. Cimetidine might be useful as a potent radioprotector for radiotherapy patients as well as for occupational exposure workers.

Characterization of the high-energy neutron beam of the PRISMA beamline using a diamond detector

NASA Astrophysics Data System (ADS)

Cazzaniga, C.; Frost, C. D.; Minniti, T.; Schooneveld, E.; Perelli Cippo, E.; Tardocchi, M.; Rebai, M.; Gorini, G.

2016-07-01

The high-energy neutron component (En > 10 MeV) of the neutron spectrum of PRISMA, a beam-line at the ISIS spallation source, has been characterized for the first time. Neutron measurements using a Single-crystal Diamond Detector at a short-pulse source are obtained by a combination of pulse height and time of flight analysis. An XY scan provides a 2D map of the high-energy neutron beam which has a diameter of about 40 mm. The high neutron flux, that has been found to be (3.8 ± 0.7) · 105 cm-2s-1 for En > 10 MeV in the centre, opens up for a possible application of the beam-line as a high-energy neutron irradiation position. Results are of interest for the development of the ChipIR beam-line, which will feature an atmospheric-like neutron spectrum for chip irradiation experiment. Furthermore, these results demonstrate that diamond detectors can be used at spallation sources to investigate the transport of high-energy neutrons down instruments which is of interest in general to designers as high-energy neutrons are a source of background in thermal beamlines.

Hard X-ray spectra of neutron stars and black hole candidates

NASA Technical Reports Server (NTRS)

Durouchoux, P.; Mahoney, W.; Clenet, Y.; Ling, J.; Wallyn, P.; Wheaton, W.; Corbet, S.; Chapuis, C.

1997-01-01

The hard X-ray behavior of several X-ray binary systems containing a neutron star or a black hole candidate is analyzed in an attempt to determine the specific signature of these categories of compact objects. Limiting the consideration to two subclasses of neutron stars, Atoll sources and non-pulsating Z sources, it appears that only the Atoll sources have a spectral behavior similar to black holes. It is proposed that Atoll sources are weakly magnetized neutron stars, whereas Z sources are small radius moderate magnetized neutron stars. Large magnetic fields funnel the accreting matter, thus preventing spherical accretion and free fall if the neutron star radius is smaller than the last stable accreting orbit. Weak magnetic fields do not have this effect, and blackbody soft photons from the stellar surface are upscattered on the relativistic infalling matter, leading to excess hard X-rays. This excess is visible in two of the observed Atoll sources and in the spectrum of a black hole candidate. In the case of a Z source, a lack of photons was remarked, providing a possible signature to distinguish between these classes of objects.

14 MeV calibration of JET neutron detectors—phase 1: calibration and characterization of the neutron source

NASA Astrophysics Data System (ADS)

Batistoni, P.; Popovichev, S.; Cufar, A.; Ghani, Z.; Giacomelli, L.; Jednorog, S.; Klix, A.; Lilley, S.; Laszynska, E.; Loreti, S.; Packer, L.; Peacock, A.; Pillon, M.; Price, R.; Rebai, M.; Rigamonti, D.; Roberts, N.; Tardocchi, M.; Thomas, D.; Contributors, JET

2018-02-01

In view of the planned DT operations at JET, a calibration of the JET neutron monitors at 14 MeV neutron energy is needed using a 14 MeV neutron generator deployed inside the vacuum vessel by the JET remote handling system. The target accuracy of this calibration is  ±10% as also required by ITER, where a precise neutron yield measurement is important, e.g. for tritium accountancy. To achieve this accuracy, the 14 MeV neutron generator selected as the calibration source has been fully characterised and calibrated prior to the in-vessel calibration of the JET monitors. This paper describes the measurements performed using different types of neutron detectors, spectrometers, calibrated long counters and activation foils which allowed us to obtain the neutron emission rate and the anisotropy of the neutron generator, i.e. the neutron flux and energy spectrum dependence on emission angle, and to derive the absolute emission rate in 4π sr. The use of high resolution diamond spectrometers made it possible to resolve the complex features of the neutron energy spectra resulting from the mixed D/T beam ions reacting with the D/T nuclei present in the neutron generator target. As the neutron generator is not a stable neutron source, several monitoring detectors were attached to it by means of an ad hoc mechanical structure to continuously monitor the neutron emission rate during the in-vessel calibration. These monitoring detectors, two diamond diodes and activation foils, have been calibrated in terms of neutrons/counts within  ±5% total uncertainty. A neutron source routine has been developed, able to produce the neutron spectra resulting from all possible reactions occurring with the D/T ions in the beam impinging on the Ti D/T target. The neutron energy spectra calculated by combining the source routine with a MCNP model of the neutron generator have been validated by the measurements. These numerical tools will be key in analysing the results from the in-vessel calibration and to derive the response of the JET neutron detectors to DT plasma neutrons starting from the response to the generator neutrons, and taking into account all the calibration circumstances.

Strategy for the absolute neutron emission measurement on ITER.

PubMed

Sasao, M; Bertalot, L; Ishikawa, M; Popovichev, S

2010-10-01

Accuracy of 10% is demanded to the absolute fusion measurement on ITER. To achieve this accuracy, a functional combination of several types of neutron measurement subsystem, cross calibration among them, and in situ calibration are needed. Neutron transport calculation shows the suitable calibration source is a DT/DD neutron generator of source strength higher than 10(10) n/s (neutron/second) for DT and 10(8) n/s for DD. It will take eight weeks at the minimum with this source to calibrate flux monitors, profile monitors, and the activation system.

Development of neutron measurement in high gamma field using new nuclear emulsion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kawarabayashi, J.; Ishihara, K.; Takagi, K.

2011-07-01

To precisely measure the neutron emissions from a spent fuel assembly of a fast breeder reactor, we formed nuclear emulsions based on a non-sensitized Oscillation Project with Emulsion tracking Apparatus (OPERA) film with AgBr grain sizes of 60, 90, and 160 nm. The efficiency for {sup 252}Cf neutron detection of the new emulsion was calculated to be 0.7 x 10{sup -4}, which corresponded to an energy range from 0.3 to 2 MeV and was consistent with a preliminary estimate based on experimental results. The sensitivity of the new emulsion was also experimentally estimated by irradiating with 565 keV and 14more » MeV neutrons. The emulsion with an AgBr grain size of 60 nm had the lowest sensitivity among the above three emulsions but was still sensitive enough to detect protons. Furthermore, the experimental data suggested that there was a threshold linear energy transfer of 15 keV/{mu}m for the new emulsion, below which no silver clusters developed. Further development of nuclear emulsion with an AgBr grain size of a few tens of nanometers will be the next stage of the present study. (authors)« less

Synthesis of Metal-Oxide/Carbon-Fiber Heterostructures and Their Properties for Organic Dye Removal and High-Temperature CO2 Adsorption

NASA Astrophysics Data System (ADS)

Shao, Liangzhi; Nie, Shibin; Shao, Xiankun; Zhang, LinLin; Li, Benxia

2018-03-01

One-dimensional metal-oxide/carbon-fiber (MO/CF) heterostructures were prepared by a facile two-step method using the natural cotton as a carbon source the low-cost commercial metal salts as precursors. The metal oxide nanostructures were first grown on the cotton fibers by a solution chemical deposition, and the metal-oxide/cotton heterostructures were then calcined and carbonized in nitrogen atmosphere. Three typical MO/CF heterostructures of TiO2/CF, ZnO/CF, and Fe2O3/CF were prepared and characterized. The loading amount of the metal oxide nanostructures on carbon fibers can be tuned by controlling the concentration of metal salt in the chemical deposition process. Finally, the performance of the as-obtained MO/CF heterostructures for organic dye removal from water was tested by the photocatalytic degradation under a simulated sunlight, and their properties of high-temperature CO2 adsorption were predicted by the temperature programmed desorption. The present study would provide a desirable strategy for the synthesis of MO/CF heterostructures for various applications.

Calibration factors for the SNOOPY NP-100 neutron dosimeter

NASA Astrophysics Data System (ADS)

Moscu, D. F.; McNeill, F. E.; Chase, J.

2007-10-01

Within CANDU nuclear power facilities, only a small fraction of workers are exposed to neutron radiation. For these individuals, roughly 4.5% of the total radiation equivalent dose is the result of exposure to neutrons. When this figure is considered across all workers receiving external exposure of any kind, only 0.25% of the total radiation equivalent dose is the result of exposure to neutrons. At many facilities, the NP-100 neutron dosimeter, manufactured by Canberra Industries Incorporated, is employed in both direct and indirect dosimetry methods. Also known as "SNOOPY", these detectors undergo calibration, which results in a calibration factor relating the neutron count rate to the ambient dose equivalent rate, using a standard Am-Be neutron source. Using measurements presented in a technical note, readings from the dosimeter for six different neutron fields in six source-detector orientations were used, to determine a calibration factor for each of these sources. The calibration factor depends on the neutron energy spectrum and the radiation weighting factor to link neutron fluence to equivalent dose. Although the neutron energy spectra measured in the CANDU workplace are quite different than that of the Am-Be calibration source, the calibration factor remains constant - within acceptable limits - regardless of the neutron source used in the calibration; for the specified calibration orientation and current radiation weighting factors. However, changing the value of the radiation weighting factors would result in changes to the calibration factor. In the event of changes to the radiation weighting factors, it will be necessary to assess whether a change to the calibration process or resulting calibration factor is warranted.

Correlating ion energies and CF{sub 2} surface production during fluorocarbon plasma processing of silicon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, Ina T.; Zhou Jie; Fisher, Ellen R.

2006-07-01

Ion energy distribution (IED) measurements are reported for ions in the plasma molecular beam source of the imaging of radicals interacting with surfaces (IRIS) apparatus. The IEDs and relative intensities of nascent ions in C{sub 3}F{sub 8} and C{sub 4}F{sub 8} plasma molecular beams were measured using a Hiden PSM003 mass spectrometer mounted on the IRIS main chamber. The IEDs are complex and multimodal, with mean ion energies ranging from 29 to 92 eV. Integrated IEDs provided relative ion intensities as a function of applied rf power and source pressure. Generally, higher applied rf powers and lower source pressures resultedmore » in increased ion intensities and mean ion energies. Most significantly, a comparison to CF{sub 2} surface interaction measurements previously made in our laboratories reveals that mean ion energies are directly and linearly correlated to CF{sub 2} surface production in these systems.« less

Nested Focusing Optics for Compact Neutron Sources

NASA Technical Reports Server (NTRS)

Nabors, Sammy A.

2015-01-01

NASA's Marshall Space Flight Center, the Massachusetts Institute of Technology (MIT), and the University of Alabama Huntsville (UAH) have developed novel neutron grazing incidence optics for use with small-scale portable neutron generators. The technology was developed to enable the use of commercially available neutron generators for applications requiring high flux densities, including high performance imaging and analysis. Nested grazing incidence mirror optics, with high collection efficiency, are used to produce divergent, parallel, or convergent neutron beams. Ray tracing simulations of the system (with source-object separation of 10m for 5 meV neutrons) show nearly an order of magnitude neutron flux increase on a 1-mm diameter object. The technology is a result of joint development efforts between NASA and MIT researchers seeking to maximize neutron flux from diffuse sources for imaging and testing applications.

Development of a Time-tagged Neutron Source for SNM Detection

DOE PAGES

Ji, Qing; Ludewigt, Bernhard; Wallig, Joe; ...

2015-06-18

Associated particle imaging (API) is a powerful technique for special nuclear material (SNM) detection and characterization of fissile material configurations. A sealed-tube neutron generator has been under development by Lawrence Berkeley National Laboratory to reduce the beam spot size on the neutron production target to 1 mm in diameter for a several-fold increase in directional resolution and simultaneously increases the maximum attainable neutron flux. A permanent magnet 2.45 GHz microwave-driven ion source has been adopted in this time-tagged neutron source. This type of ion source provides a high plasma density that allows the use of a sub-millimeter aperture for themore » extraction of a sufficient ion beam current and lets us achieve a much reduced beam spot size on target without employing active focusing. The design of this API generator uses a custom-made radial high voltage insulator to minimize source to neutron production target distance and to provide for a simple ion source cooling arrangement. Preliminary experimental results showed that more than 100 µA of deuterium ions have been extracted, and the beam diameter on the neutron production target is around 1 mm.« less

Neutron generator for BNCT based on high current ECR ion source with gyrotron plasma heating.

PubMed

Skalyga, V; Izotov, I; Golubev, S; Razin, S; Sidorov, A; Maslennikova, A; Volovecky, A; Kalvas, T; Koivisto, H; Tarvainen, O

2015-12-01

BNCT development nowadays is constrained by a progress in neutron sources design. Creation of a cheap and compact intense neutron source would significantly simplify trial treatments avoiding use of expensive and complicated nuclear reactors and accelerators. D-D or D-T neutron generator is one of alternative types of such sources for. A so-called high current quasi-gasdynamic ECR ion source with plasma heating by millimeter wave gyrotron radiation is suggested to be used in a scheme of D-D neutron generator in the present work. Ion source of that type was developed in the Institute of Applied Physics of Russian Academy of Sciences (Nizhny Novgorod, Russia). It can produce deuteron ion beams with current density up to 700-800 mA/cm(2). Generation of the neutron flux with density at the level of 7-8·10(10) s(-1) cm(-2) at the target surface could be obtained in case of TiD2 target bombardment with deuteron beam accelerated to 100 keV. Estimations show that it is enough for formation of epithermal neutron flux with density higher than 10(9) s(-1) cm(-2) suitable for BNCT. Important advantage of described approach is absence of Tritium in the scheme. First experiments performed in pulsed regime with 300 mA, 45 kV deuteron beam directed to D2O target demonstrated 10(9) s(-1) neutron flux. This value corresponds to theoretical estimations and proofs prospects of neutron generator development based on high current quasi-gasdynamic ECR ion source. Copyright © 2015 Elsevier Ltd. All rights reserved.

Characterization of the Energy Spectrum at the Indiana University Neutron Source

DTIC Science & Technology

2011-03-01

CHARACTERIZATION OF THE ENERGY SPECTRUM AT THE INDIANA UNIVERSITY NREP NEUTRON SOURCE THESIS Matthew R. Halstead, Civilian AFIT/GNE/ENP/11-M08...subject to copyright protection in the United States. AFIT/GNE/ENP/11-M08 CHARACTERIZATION OF THE ENERGY SPECTRUM AT THE INDIANA UNIVERSITY NREP NEUTRON...The neutron source at the Indiana University Cyclotron Facility produces neu- trons via proton bombardment of a natural beryllium (100% 9Be) target

X-ray Measurements of a Thermo Scientific P385 DD Neutron Generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

E.H. Seabury; D.L. Chichester; A.J. Caffrey

2001-08-01

Idaho National Laboratory is experimenting with electrical neutron generators, as potential replacements for californium-252 radioisotopic neutron sources in its PINS prompt gamma-ray neutron activation analysis (PGNAA) system for the identification of military chemical warfare agents and explosives. In addition to neutron output, we have recently measured the x-ray output of the Thermo Scientific P385 deuterium-deuterium neutron generator. X-rays are a normal byproduct from a neutron generator and depending on their intensity and energy they can interfere with gamma rays from the object under test, increase gamma-spectrometer dead time, and reduce PGNAA system throughput. The P385 x-ray energy spectrum was measuredmore » with a high-purity germanium (HPGe) detector, and a broad peak is evident at about 70 keV. To identify the source of the x-rays within the neutron generator assembly, it was scanned by collimated scintillation detectors along its long axis. At the strongest x-ray emission points, the generator also was rotated 60° between measurements. The scans show the primary source of x-ray emission from the P385 neutron generator is an area 60 mm from the neutron production target, in the vicinity of the ion source. Rotation of the neutron generator did not significantly alter the x-ray count rate, and the x-ray emission appears to be axially symmetric within the neutron generator.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rees, Brian G.

These are slides from a presentation on the basics of neutrons. A few topics covered are: common origins of terrestrial neutron radiation, neutron sources, neutron energy, interactions, detecting neutrons, gammas from neutron interactions, neutron signatures in gamma-ray spectra, neutrons and NaI, neutron fluence to dose (msV), instruments' response to neutrons.

The neutron flux monitors from 20 keV to 1 MeV for BNCT: performance study using accelerator-based neutron sources

NASA Astrophysics Data System (ADS)

Guan, X. C.; Gong, Y.; Murata, I.; Wang, T. S.

2018-05-01

The performance of the neutron flux monitors from 20 keV to 1 MeV developed for boron neutron capture therapy (BNCT) is studied by Monte Carlo simulations using accelerator-based neutron sources (ABNSs). The results show that the performance of the neutron flux monitors is very satisfactory and they can be efficiently used in practical applications to measure the neutron fluxes from 20 keV to 1 MeV of ABNSs for BNCT to high accuracy.

A laser-induced repetitive fast neutron source applied for gold activation analysis

NASA Astrophysics Data System (ADS)

Lee, Sungman; Park, Sangsoon; Lee, Kitae; Cha, Hyungki

2012-12-01

A laser-induced repetitively operated fast neutron source was developed for applications in laser-driven nuclear physics research. The developed neutron source, which has a neutron yield of approximately 4 × 105 n/pulse and can be operated up to a pulse repetition rate of 10 Hz, was applied for a gold activation analysis. Relatively strong delayed gamma spectra of the activated gold were measured at 333 keV and 355 keV, and proved the possibility of the neutron source for activation analyses. In addition, the nuclear reactions responsible for the measured gamma spectra of gold were elucidated by the 14 MeV fast neutrons resulting from the D(t,n)He4 nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T3.

A laser-induced repetitive fast neutron source applied for gold activation analysis.

PubMed

Lee, Sungman; Park, Sangsoon; Lee, Kitae; Cha, Hyungki

2012-12-01

A laser-induced repetitively operated fast neutron source was developed for applications in laser-driven nuclear physics research. The developed neutron source, which has a neutron yield of approximately 4 × 10(5) n/pulse and can be operated up to a pulse repetition rate of 10 Hz, was applied for a gold activation analysis. Relatively strong delayed gamma spectra of the activated gold were measured at 333 keV and 355 keV, and proved the possibility of the neutron source for activation analyses. In addition, the nuclear reactions responsible for the measured gamma spectra of gold were elucidated by the 14 MeV fast neutrons resulting from the D(t,n)He(4) nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T(3).

Quantitative non-destructive assay of PuBe neutron sources

NASA Astrophysics Data System (ADS)

Lakosi, László; Bagi, János; Nguyen, Cong Tam

2006-02-01

PuBe neutron sources were assayed, using a combination of high resolution γ-spectrometry (HRGS) and neutron correlation technique. In a previous publication [J. Bagi, C. Tam Nguyen, L. Lakosi, Nucl. Instr. and Meth. B 222 (2004) 242] a passive neutron well-counter was reported with 3He tubes embedded in a polyamide (TERRAMID) moderator (lined inside with Cd) surrounding the sources to be measured. Gross and coincidence neutron counting was performed, and the Pu content of the sources was found out from isotope analysis and by adopting specific (α, n) reaction yields of the Pu isotopes and 241Am in Be, based on supplier's information and literature data. The method was further developed and refined. Evaluation algorithm was more precisely worked out. The contribution of secondary (correlated) neutrons to the total neutron output was derived from the coincidence (doubles) count rate and taken into account in assessing the Pu content. A new evaluation of former results was performed. Assay was extended to other PuBe sources, and new results were added. In order to attain higher detection efficiency, a more efficient moderator was also applied, with and without Cd shielding around the assay chamber. Calibration seems possible using neutron measurements only (without γ-spectrometry), based on a correlation between the Pu amount and the coincidence-to-total ratio. It is expected that the method could be used for Pu accountancy and safeguards verification as well as identification and assay of seized, found, or not documented PuBe neutron sources.

The Maturely, Immature Orientale Impact Basin

NASA Astrophysics Data System (ADS)

Cahill, J. T.; Lawrence, D. J.; Stickle, A. M.; Delen, O.; Patterson, G.; Greenhagen, B. T.

2015-12-01

Lunar surface maturity is consistently examined using the NIR optical maturity parameter (OMAT) [1]. However, the NIR only provides a perspective of the upper microns of the lunar surface. Recent studies of Lunar Prospector (LP) and Lunar Reconnaissance Orbiter data sets are now demonstrating additional measures of maturity with sensitivities to greater depths (~2 m) in the regolith. These include thermal infrared, S-band radar, and epithermal neutron data sets [2-4]. Interestingly, each of these parameters is directly comparable to OMAT despite each measuring slightly different aspects of the regolith. This is demonstrated by Lawrence et al. [3] where LP-measured non-polar highlands epithermal neutrons trend well with albedo, OMAT, and the Christensen Feature (CF). Lawrence et al. [3] used these data to derive and map highlands hydrogen (H) which is dominantly a function of H-implantation. With this in mind, areas of enriched-H are mature, while areas of depleted H are immature. Surface roughness as measured by S-band radar [4], also provides a measure of maturity. In this case, the circular polarization ratio (CPR) is high when rough and immature, and low when smooth and mature. Knowing this, one can recognize areas in the non-polar lunar highlands that show contradictory measures of maturity. For example, while many lunar localities show consistently immature albedo, OMAT, CF, CPR, and H concentrations (e.g., Tycho), others do not. Orientale basin is the most prominent example, shown to have immature CPR, CF, and H concentrations despite a relatively mature albedo and OMAT values as well as an old age determination (~3.8 Ga). To better understand how the lunar regolith is weathering in the upper 1-2 m of regolith with time we examine the Orientale basin relative to other highlands regions. [1] Lucey et al. (2000) JGR, 105, 20377; [2] Lucey et al. (2013) LPSC, 44, 2890; [3] Lawrence et al. (2015) Icarus, j.icarus.2015.01.005; [4] Neish et al. (2013) JGR, 118, 2247.

Comparison of intestine and bone marrow radiosensitivity of the BALB/c and the C57BL/6 mouse strains and their B6CF1 offspring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, W.R.; Fry, R.J.; Sallese, A.R.

1987-06-01

The radiosensitivity as measured by LD50/6 or LD50/30 of the F1 hybrid B6CF1 (C57BL/6 X BALB/c) is similar to that of C57BL/6 mice but markedly different from BALB/c. The LD50/6 for BALB/c mice was about 8.8 Gy compared to 16.4 Gy for the B6CF1. The difference in LD50/6 between the parent strains or between BALB/c and the F1 hybrid could not be explained by any differences in crypt cell number, cell cycle time, or transit time. Likewise, the observed differences in the LD50/6 do not appear to result from marked differences in the radiosensitivity of marrow stem cells (CFU-S) sincemore » the D0's for the three genotypes of mice were similar. Also, there were no apparent differences in the red blood cell contents of several enzymes associated with antioxidant defenses. The microcolony assay was used to determine the D0 for the crypt clonogenic cells and the D0 values for 60Co gamma rays were about 0.8 Gy for BALB/c mice and 1.4 Gy for B6CF1 mice. However, the D0 values for JANUS fission neutrons were similar; 0.6 Gy for the BALB/c mice and 0.5 for the B6CF1 mice. A comparison of clonogenic cell kinetics, using prolonged colcemid block to distinguish between slowly and rapidly cycling cells suggest that, normally, the stem cells are slowly cycling in both the BALB/c and the B6CF1 hybrid. However, the stem cells of the B6CF1 appear to go into rapid cell cycle more rapidly than those of the BALB/c following irradiation or prolonged colcemid treatment. The more rapid recovery in intestinal epihelial cell production in the B6CF1 hybrid after irradiation may provide an increased mucosal barrier and may, in part, explain the difference in the response to radiation compared to that in the BALB/c.« less

Evaluation of the Neutron Data Standards

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlson, A. D.; Pronyaev, V. G.; Capote, R.

With the need for improving existing nuclear data evaluations, (e.g., ENDF/B-VIII.0 and JEFF-3.3 releases) the first step was to evaluate the standards for use in such a library. This new standards evaluation made use of improved experimental data and some developments in the methodology of analysis and evaluation. In addition to the work on the traditional standards, this work produced the extension of some energy ranges and includes new reactions that are called reference cross sections. Since the effort extends beyond the traditional standards, it is called the neutron data standards evaluation. This international effort has produced new evaluations ofmore » the following cross section standards: the H(n,n), 6Li(n,t), 10B(n,α), 10B(n,α 1γ), natC(n,n), Au(n,γ), 235U(n,f) and 238U(n,f). Also in the evaluation process the 238U(n,γ) and 239Pu(n,f) cross sections that are not standards were evaluated. Evaluations were also obtained for data that are not traditional standards: the Maxwellian spectrum averaged cross section for the Au(n,γ) cross section at 30 keV; reference cross sections for prompt γ-ray production in fast neutron-induced reactions; reference cross sections for very high energy fission cross sections; the 252Cf spontaneous fission neutron spectrum and the 235U prompt fission neutron spectrum induced by thermal incident neutrons; and the thermal neutron constants. The data and covariance matrices of the uncertainties were obtained directly from the evaluation procedure.« less

Evaluation of the Neutron Data Standards

DOE PAGES

Carlson, A. D.; Pronyaev, V. G.; Capote, R.; ...

2018-02-01

With the need for improving existing nuclear data evaluations, (e.g., ENDF/B-VIII.0 and JEFF-3.3 releases) the first step was to evaluate the standards for use in such a library. This new standards evaluation made use of improved experimental data and some developments in the methodology of analysis and evaluation. In addition to the work on the traditional standards, this work produced the extension of some energy ranges and includes new reactions that are called reference cross sections. Since the effort extends beyond the traditional standards, it is called the neutron data standards evaluation. This international effort has produced new evaluations ofmore » the following cross section standards: the H(n,n), 6Li(n,t), 10B(n,α), 10B(n,α 1γ), natC(n,n), Au(n,γ), 235U(n,f) and 238U(n,f). Also in the evaluation process the 238U(n,γ) and 239Pu(n,f) cross sections that are not standards were evaluated. Evaluations were also obtained for data that are not traditional standards: the Maxwellian spectrum averaged cross section for the Au(n,γ) cross section at 30 keV; reference cross sections for prompt γ-ray production in fast neutron-induced reactions; reference cross sections for very high energy fission cross sections; the 252Cf spontaneous fission neutron spectrum and the 235U prompt fission neutron spectrum induced by thermal incident neutrons; and the thermal neutron constants. The data and covariance matrices of the uncertainties were obtained directly from the evaluation procedure.« less

Evaluation of the Neutron Data Standards

NASA Astrophysics Data System (ADS)

Carlson, A. D.; Pronyaev, V. G.; Capote, R.; Hale, G. M.; Chen, Z.-P.; Duran, I.; Hambsch, F.-J.; Kunieda, S.; Mannhart, W.; Marcinkevicius, B.; Nelson, R. O.; Neudecker, D.; Noguere, G.; Paris, M.; Simakov, S. P.; Schillebeeckx, P.; Smith, D. L.; Tao, X.; Trkov, A.; Wallner, A.; Wang, W.

2018-02-01

With the need for improving existing nuclear data evaluations, (e.g., ENDF/B-VIII.0 and JEFF-3.3 releases) the first step was to evaluate the standards for use in such a library. This new standards evaluation made use of improved experimental data and some developments in the methodology of analysis and evaluation. In addition to the work on the traditional standards, this work produced the extension of some energy ranges and includes new reactions that are called reference cross sections. Since the effort extends beyond the traditional standards, it is called the neutron data standards evaluation. This international effort has produced new evaluations of the following cross section standards: the H(n,n), 6Li(n,t), 10B(n,α), 10B(n,α1 γ), natC(n,n), Au(n,γ), 235U(n,f) and 238U(n,f). Also in the evaluation process the 238U(n,γ) and 239Pu(n,f) cross sections that are not standards were evaluated. Evaluations were also obtained for data that are not traditional standards: the Maxwellian spectrum averaged cross section for the Au(n,γ) cross section at 30 keV; reference cross sections for prompt γ-ray production in fast neutron-induced reactions; reference cross sections for very high energy fission cross sections; the 252Cf spontaneous fission neutron spectrum and the 235U prompt fission neutron spectrum induced by thermal incident neutrons; and the thermal neutron constants. The data and covariance matrices of the uncertainties were obtained directly from the evaluation procedure.

Slow neutron mapping technique for level interface measurement

NASA Astrophysics Data System (ADS)

Zain, R. M.; Ithnin, H.; Razali, A. M.; Yusof, N. H. M.; Mustapha, I.; Yahya, R.; Othman, N.; Rahman, M. F. A.

2017-01-01

Modern industrial plant operations often require accurate level measurement of process liquids in production and storage vessels. A variety of advanced level indicators are commercially available to meet the demand, but these may not suit specific need of situations. The neutron backscatter technique is exceptionally useful for occasional and routine determination, particularly in situations such as pressure vessel with wall thickness up to 10 cm, toxic and corrosive chemical in sealed containers, liquid petroleum gas storage vessels. In level measurement, high energy neutrons from 241Am-Be radioactive source are beamed onto a vessel. Fast neutrons are slowed down mostly by collision with hydrogen atoms of material inside the vessel. Parts of thermal neutron are bounced back towards the source. By placing a thermal detector next to the source, these backscatter neutrons can be measured. The number of backscattered neutrons is directly proportional to the concentration of the hydrogen atoms in front of the neutron detector. As the source and detector moved by the matrix around the side of the vessel, interfaces can be determined as long as it involves a change in hydrogen atom concentration. This paper presents the slow neutron mapping technique to indicate level interface of a test vessel.

The performance of the upgraded Los Alamos Neutron Source

NASA Astrophysics Data System (ADS)

Ito, Takeyasu; LANL UCN Source Collaboration

2017-09-01

Los Alamos National Laboratory has been operating an ultracold (UCN) source based on a solid deuterium (SD2) UCN converter driven by spallation neutrons for over 10 years. It has recently been successfully upgraded, by replacing the cryostat that contains the cold neutron moderator, SD2 volume, and vertical UCN guide. The horizontal UCN guide that transports UCN out of the radiation shield was also replaced. The new design reflects lessons learned from the 10+ year long operation of the previous version of the UCN source and is optimized to maximize the cold neutron flux at the SD2 volume, featuring a close coupled cold neutron moderator, and maximize the transport of the UCN to experiments. During the commissioning of the upgraded UCN source, data were collected to measure its performance, including cold neutron spectra as a function of the cold moderator temperature, and the UCN density in a vessel outside the source. In this talk, after a brief overview of the design of the upgraded source, the results of the performance tests and comparison to prediction will be presented. This work was funded by LANL LDRD.

Measurement and simulation for a complementary imaging with the neutron and X-ray beams

NASA Astrophysics Data System (ADS)

Hara, Kaoru Y.; Sato, Hirotaka; Kamiyama, Takashi; Shinohara, Takenao

2017-09-01

By using a composite source system, we measured radiographs of the thermal neutron and keV X-ray in the 45-MeV electron linear accelerator facility at Hokkaido University. The source system provides the alternative beam of neutron and X-ray by switching the production target onto the electron beam axis. In the measurement to demonstrate a complementary imaging, the detector based on a vacuum-tube type neutron color image intensifier was applied to the both beams for dual-purpose. On the other hand, for reducing background in a neutron transmission spectrum, test measurements using a gadolinium-type neutron grid were performed with a cold neutron source at Hokkaido University. In addition, the simulations of the neutron and X-ray transmissions for various substances were performed using the PHITS code. A data analysis procedure for estimating the substance of sample was investigated through the simulations.

Saclay Compact Accelerator-driven Neutron Sources (SCANS)

NASA Astrophysics Data System (ADS)

Marchix, A.; Letourneau, A.; Tran, HN; Chauvin, N.; Menelle, A.; Ott, F.; Schwindling, J.

2018-06-01

For next decade, the European neutron scattering community will face of important changes, as many facilities will close, strictly fission-based sources. This statement mainly concerns France with the planned closure of Orphee and ILL. At CEA-Saclay, the project SONATE has been launched in order to provide a high intensity neutron source in Saclay site, this project is based on Compact Accelerator-driven Neutron Sources technology coupled to high-intensity beams. The goal of SONATE is to develop a 50 kW target, aiming to produce at least a neutron yield of 1013 s-1 in pulse mode with a peak current of 100 mA. We have investigated in this document the best combinations of beam/target which would lead to this substantial neutron yields. Further investigations and tests have to be carry out, especially due to sparse data on thick target and such low-energy beams considered in this document. An intermediate step to the SONATE project is under test and development, called IPHI-NEUTRON, which would lead to provide a small-size neutron facility mainly devoted to neutron imagery for industry. This step is based on the existing 3 MeV proton beam, named IPHI. Best target candidates are Lithium and Beryllium, leading respectively to a neutron yield of about 2.1013 s-1 and 4.1012 s-1.

Study of neutron shielding collimators for curved beamlines at the European Spallation Source

NASA Astrophysics Data System (ADS)

Santoro, V.; DiJulio, D. D.; Ansell, S.; Cherkashyna, N.; Muhrer, G.; Bentley, P. M.

2018-06-01

The European Spallation Source is being constructed in Lund, Sweden and is planned to be the world’s brightest pulsed spallation neutron source for cold and thermal neutron beams (≤ 1 eV). The facility uses a 2 GeV proton beam to produce neutrons from a tungsten target. The neutrons are then moderated in a moderator assembly consisting of both liquid hydrogen and water compartments. Surrounding the moderator are 22 beamports, which view the moderator’s outside surfaces. The beamports are connected to long neutron guides that transport the moderated neutrons to the sample position via reflections. As well as the desired moderated neutrons, fast neutrons coming directly from the target can find their way down the beamlines. These can create unwanted sources of background for the instruments. To mitigate such a kind of background, several instruments will use curved guides to lose direct line-of-sight (LoS) to the moderator and the target. In addition instruments can also use shielding collimators to reduce the amount of fast neutrons further traveling down the guide due to albedo reflections or streaming. Several different materials have been proposed for this purpose. We present the results of a study of different options for collimators and identify the optimal choices that balance cost, background and activation levels.

Feasibility of sealed D-T neutron generator as neutron source for liver BNCT and its beam shaping assembly.

PubMed

Liu, Zheng; Li, Gang; Liu, Linmao

2014-04-01

This paper involves the feasibility of boron neutron capture therapy (BNCT) for liver tumor with four sealed neutron generators as neutron source. Two generators are placed on each side of the liver. The high energy of these emitted neutrons should be reduced by designing a beam shaping assembly (BSA) to make them useable for BNCT. However, the neutron flux decreases as neutrons pass through different materials of BSA. Therefore, it is essential to find ways to increase the neutron flux. In this paper, the feasibility of using low enrichment uranium as a neutron multiplier is investigated to increase the number of neutrons emitted from D-T neutron generators. The neutron spectrum related to our system has a proper epithermal flux, and the fast and thermal neutron fluxes comply with the IAEA recommended values. Copyright © 2014 Elsevier Ltd. All rights reserved.

Neutron coincidence detectors employing heterogeneous materials

DOEpatents

Czirr, J. Bartley; Jensen, Gary L.

1993-07-27

A neutron detector relies upon optical separation of different scintillators to measure the total energy and/or number of neutrons from a neutron source. In pulse mode embodiments of the invention, neutrons are detected in a first detector which surrounds the neutron source and in a second detector surrounding the first detector. An electronic circuit insures that only events are measured which correspond to neutrons first detected in the first detector followed by subsequent detection in the second detector. In spectrometer embodiments of the invention, neutrons are thermalized in the second detector which is formed by a scintillator-moderator and neutron energy is measured from the summed signals from the first and second detectors.

Non-destructive diagnostics of irradiated materials using neutron scattering from pulsed neutron sources

NASA Astrophysics Data System (ADS)

Korenev, Sergey; Sikolenko, Vadim

2004-09-01

The advantage of neutron-scattering studies as compared to the standard X-ray technique is the high penetration of neutrons that allow us to study volume effects. The high resolution of instrumentation on the basis neutron scattering allows measurement of the parameters of lattice structure with high precision. We suggest the use of neutron scattering from pulsed neutron sources for analysis of materials irradiated with pulsed high current electron and ion beams. The results of preliminary tests using this method for Ni foils that have been studied by neutron diffraction at the IBR-2 (Pulsed Fast Reactor at Joint Institute for Nuclear Research) are presented.

Schubert Review 2017 2-page summary of AmBe project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, A.

2017-04-04

Accelerator-based neutron sources to replace Americium Beryllium (AmBe) radiological sources used for oil well logging are needed for safety and security purposes. DT neutron generators have successfully been used in the past for some measurements, but are less sensitive to rock porosity than the AmBe spectrum is. Additionally, the well-logging industry has decades of data calibrated to the AmBe neutron spectrum. Ideally, if this industry were required to use an accelerator source, they would like a similar neutron spectrum to the AmBe source, with a yield of at least 1×10 7 n/s.

Characterization of γ-ray background at IMAT beamline of ISIS Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Festa, G.; Andreani, C.; Arcidiacono, L.; Burca, G.; Kockelmann, W.; Minniti, T.; Senesi, R.

2017-08-01

The environmental γ -ray background on the IMAT beamline at ISIS Spallation Neutron Source, Target Station 2, is characterized via γ spectroscopy. The measurements include gamma exposure at the imaging detector position, along with the gamma background inside the beamline. Present results are discussed and compared with previous measurements recorded at INES and VESUVIO beamlines operating at Target Station 1. They provide new outcome for expanding and optimizing the PGAA experimental capability at the ISIS neutron source for the investigation of materials, engineering components and cultural heritage objects at the ISIS neutron source.

Monte Carlo simulation of thermal neutron flux of americium-beryllium source used in neutron activation analysis

NASA Astrophysics Data System (ADS)

Didi, Abdessamad; Dadouch, Ahmed; Bencheikh, Mohamed; Jai, Otman

2017-09-01

The neutron activation analysis is a method of exclusively elemental analysis. Its implementation of irradiates the sample which can be analyzed by a high neutron flux, this method is widely used in developed countries with nuclear reactors or accelerators of particle. The purpose of this study is to develop a prototype to increase the neutron flux such as americium-beryllium and have the opportunity to produce radioisotopes. Americium-beryllium is a mobile source of neutron activity of 20 curie, and gives a thermal neutron flux of (1.8 ± 0.0007) × 106 n/cm2 s when using water as moderator, when using the paraffin, the thermal neutron flux increases to (2.2 ± 0.0008) × 106 n/cm2 s, in the case of adding two solid beryllium barriers, the distance between them is 24 cm, parallel and symmetrical about the source, the thermal flux is increased to (2.5 ± 0.0008) × 106 n/cm2 s and in the case of multi-source (6 sources), with-out barriers, increases to (1.17 ± 0.0008) × 107 n/cm2 s with a rate of increase equal to 4.3 and with the both barriers flux increased to (1.37 ± 0.0008) × 107 n/cm2 s.

Modulating the Neutron Flux from a Mirror Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryutov, D D

2011-09-01

A 14-MeV neutron source based on a Gas-Dynamic Trap will provide a high flux of 14 MeV neutrons for fusion materials and sub-component testing. In addition to its main goal, the source has potential applications in condensed matter physics and biophysics. In this report, the author considers adding one more capability to the GDT-based neutron source, the modulation of the neutron flux with a desired frequency. The modulation may be an enabling tool for the assessment of the role of non-steady-state effects in fusion devices as well as for high-precision, low-signal basic science experiments favoring the use of the synchronousmore » detection technique. A conclusion is drawn that modulation frequency of up to 1 kHz and modulation amplitude of a few percent is achievable. Limitations on the amplitude of modulations at higher frequencies are discussed.« less

Systematic neutron guide misalignment for an accelerator-driven spallation neutron source

NASA Astrophysics Data System (ADS)

Zendler, C.; Bentley, P. M.

2016-08-01

The European Spallation Source (ESS) is a long pulse spallation neutron source that is currently under construction in Lund, Sweden. A considerable fraction of the 22 planned instruments extend as far as 75-150 m from the source. In such long beam lines, misalignment between neutron guide segments can decrease the neutron transmission significantly. In addition to a random misalignment from installation tolerances, the ground on which ESS is built can be expected to sink with time, and thus shift the neutron guide segments further away from the ideal alignment axis in a systematic way. These systematic errors are correlated to the ground structure, position of buildings and shielding installation. Since the largest deformation is expected close to the target, even short instruments might be noticeably affected. In this study, the effect of this systematic misalignment on short and long ESS beam lines is analyzed, and a possible mitigation by overillumination of subsequent guide sections investigated.

Recent UCN source developments at Los Alamos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seestrom, S.J.; Anaya, J.M.; Bowles, T.J.

The most intense sources of ultra cold neutrons (UCN) have bee built at reactors where the high average thermal neutron flux can overcome the low UCN production rate to achieve usable densities of UCN. At spallation neutron sources the average flux available is much lower than at a reactor, though the peak flux can be comparable or higher. The authors have built a UCN source that attempts to take advantage of the high peak flux available at the short pulse spallation neutron source at the Los Alamos Neutron Science Center (LANSCE) to generate a useful number of UCN. In themore » source UCN are produced by Doppler-shifted Bragg scattering of neutrons to convert 400-m/s neutrons down into the UCN regime. This source was initially tested in 1996 and various improvements were made based on the results of the 1996 running. These improvements were implemented and tested in 1997. In sections 2 and 3 they discuss the improvements that have been made and the resulting source performance. Recently an even more interesting concept was put forward by Serebrov et al. This involves combining a solid Deuterium UCN source, previously studied by Serebrov et al., with a pulsed spallation source to achieve world record UCN densities. They have initiated a program of calculations and measurements aimed at verifying the solid Deuterium UCN source concept. The approach has been to develop an analytical capability, combine with Monte Carlo calculations of neutron production, and perform benchmark experiments to verify the validity of the calculations. Based on the calculations and measurements they plan to test a modified version of the Serebrov UCN factory. They estimate that they could produce over 1,000 UCN/cc in a 15 liter volume, using 1 {micro}amp of 800 MeV protons for two seconds every 500 seconds. They will discuss the result UCN production measurements in section 4.« less

Some neutron and gamma radiation characteristics of plutonium cermet fuel for isotopic power sources

NASA Technical Reports Server (NTRS)

Neff, R. A.; Anderson, M. E.; Campbell, A. R.; Haas, F. X.

1972-01-01

Gamma and neutron measurements on various types of plutonium sources are presented in order to show the effects of O-17, O-18 F-19, Pu-236, age of the fuel, and size of the source on the gamma and neutron spectra. Analysis of the radiation measurements shows that fluorine is the main contributor to the neutron yields from present plutonium-molybdenum cermet fuel, while both fluorine and Pu-236 daughters contribute significantly to the gamma ray intensities.

The need for precise and well-documented experimental data on prompt fission neutron spectra from neutron-induced fission of 239Pu

DOE PAGES

Neudecker, Denise; Taddeucci, Terry Nicholas; Haight, Robert Cameron; ...

2016-01-06

The spectrum of neutrons emitted promptly after 239Pu(n,f)—a so-called prompt fission neutron spectrum (PFNS)—is a quantity of high interest, for instance, for reactor physics and global security. However, there are only few experimental data sets available that are suitable for evaluations. In addition, some of those data sets differ by more than their 1-σ uncertainty boundaries. We present the results of MCNP studies indicating that these differences are partly caused by underestimated multiple scattering contributions, over-corrected background, and inconsistent deconvolution methods. A detailed uncertainty quantification for suitable experimental data was undertaken including these effects, and test-evaluations were performed with themore » improved uncertainty information. The test-evaluations illustrate that the inadequately estimated effects and detailed uncertainty quantification have an impact on the evaluated PFNS and associated uncertainties as well as the neutron multiplicity of selected critical assemblies. A summary of data and documentation needs to improve the quality of the experimental database is provided based on the results of simulations and test-evaluations. Furthermore, given the possibly substantial distortion of the PFNS by multiple scattering and background effects, special care should be taken to reduce these effects in future measurements, e.g., by measuring the 239Pu PFNS as a ratio to either the 235U or 252Cf PFNS.« less

Relationship between blastocoel cell-free DNA and day-5 blastocyst morphology.

PubMed

Rule, Kiersten; Chosed, Renee J; Arthur Chang, T; David Wininger, J; Roudebush, William E

2018-06-04

Cell-free DNA (cfDNA) which is present in the blastocoel cavity of embryos is believed to result from physiological apoptosis during development. This study assessed cfDNA content and caspase-3 protease activity in day-5 IVF blastocysts to determine if there was a correlation with embryo morphology. Day-5 IVF blastocysts were scored according to the Gardner and Schoolcraft system (modified to generate a numerical value) and cfDNA was collected following laser-induced blastocoel collapsing prior to cryopreservation in 25 μL of media. cfDNA was quantified via fluorospectrometry and apoptotic activity was assessed via a caspase-3 protease assay using a fluorescent peptide substrate. Data were compared by linear regression. A total of 32 embryos were evaluated. There was a significant (p < 0.01) and positive correlation (cfDNA = 104.753 + (11.281 × score); R 2  = 0.200) between embryo score and cfDNA content. A significant (p < 0.05) and positive correlation (cfDNA = 115.9 + (0.05 × caspase-3); R 2 = 0.128) was observed between caspase-3 activity and cfDNA levels. There was no significant relationship between caspase-3 activity and embryo morphology score. This study provides further evidence that cfDNA is present in blastocoel fluid, can be quantified, and positively correlates with embryonic morphology. There is also evidence that at least a portion of the cfDNA present is from intracellular contents of embryonic cells that underwent apoptosis. Additional studies are warranted to determine other physiological sources of the cfDNA in blastocyst fluid and to determine the relationship with cfDNA content, embryo morphology, and chromosomal ploidy status plus implantation potential.

Temporal narrowing of neutrons produced by high-intensity short-pulse lasers

DOE PAGES

Higginson, D. P.; Vassura, L.; Gugiu, M. M.; ...

2015-07-28

The production of neutron beams having short temporal duration is studied using ultraintense laser pulses. Laser-accelerated protons are spectrally filtered using a laser-triggered microlens to produce a short duration neutron pulse via nuclear reactions induced in a converter material (LiF). This produces a ~3 ns duration neutron pulse with 10 4 n/MeV/sr/shot at 0.56 m from the laser-irradiated proton source. The large spatial separation between the neutron production and the proton source allows for shielding from the copious and undesirable radiation resulting from the laser-plasma interaction. Finally, this neutron pulse compares favorably to the duration of conventional accelerator sources andmore » should scale up with, present and future, higher energy laser facilities to produce brighter and shorter neutron beams for ultrafast probing of dense materials.« less

Single Crystal Diffuse Neutron Scattering

DOE PAGES

Welberry, Richard; Whitfield, Ross

2018-01-11

Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. Here, we compare three different instruments that have been used bymore » us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source.« less

Single Crystal Diffuse Neutron Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welberry, Richard; Whitfield, Ross

Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. Here, we compare three different instruments that have been used bymore » us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source.« less

Neutrons Flux Distributions of the Pu-Be Source and its Simulation by the MCNP-4B Code

NASA Astrophysics Data System (ADS)

Faghihi, F.; Mehdizadeh, S.; Hadad, K.

Neutron Fluence rate of a low intense Pu-Be source is measured by Neutron Activation Analysis (NAA) of 197Au foils. Also, the neutron fluence rate distribution versus energy is calculated using the MCNP-4B code based on ENDF/B-V library. Theoretical simulation as well as our experimental performance are a new experience for Iranians to make reliability with the code for further researches. In our theoretical investigation, an isotropic Pu-Be source with cylindrical volume distribution is simulated and relative neutron fluence rate versus energy is calculated using MCNP-4B code. Variation of the fast and also thermal neutrons fluence rate, which are measured by NAA method and MCNP code, are compared.

Neutron calibration sources in the Daya Bay experiment

DOE PAGES

Liu, J.; Carr, R.; Dwyer, D. A.; ...

2015-07-09

We describe the design and construction of the low rate neutron calibration sources used in the Daya Bay Reactor Anti-neutrino Experiment. Such sources are free of correlated gamma-neutron emission, which is essential in minimizing induced background in the anti-neutrino detector. Thus, the design characteristics have been validated in the Daya Bay anti-neutrino detector.

High power neutron production targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wender, S.

1996-06-01

The author describes issues of concern in the design of targets and associated systems for high power neutron production facilities. The facilities include uses for neutron scattering, accelerator driven transmutation, accelerator production of tritium, short pulse spallation sources, and long pulse spallation sources. Each of these applications requires a source with different design needs and consequently different implementation in practise.

Neutron radiation characteristics of plutonium dioxide fuel

NASA Technical Reports Server (NTRS)

Taherzadeh, M.

1972-01-01

The major sources of neutrons from plutonium dioxide nuclear fuel are considered in detail. These sources include spontaneous fission of several of the Pu isotopes, (alpha, n) reactions with low Z impurities in the fuel, and (alpha, n) reactions with O-18. For spontaneous fission neutrons a value of (1.95 + or - 0.07) X 1,000 n/s/g PuO2 is obtained. The neutron yield from (alpha, n) reactions with oxygen is calculated by integrating the reaction rate equation over all alpha-particle energies and all center-of-mass angles. The results indicate a neutron emission rate of (1.14 + or - 0.26) X 10,000 n/s/g PuO2. The neutron yield from (alpha, n) reactions with low Z impurities in the fuel is presented in tabular form for one part part per million of each impurity. The total neutron yield due to the combined effects of all the impurities depends upon the fractional weight concentration of each impurity. The total neutron flux emitted from a particular fuel geometry is estimated by adding the neutron yield due to the induced fission to the other neutron sources.

The US Spallation Neutron Source Project

NASA Astrophysics Data System (ADS)

Olsen, David K.

1997-10-01

Slow neutrons, with wavelengths between a few tenths to a few tens of angstroms, are an important probe for condensed-matter physics and are produced with either fission reactors or accelerator-based spallation sources. The Spallation Neutron Source (SNS) is a collaborative project between DOE National Laboratories including LBNL, LANL, BNL, ANL and ORNL to build the next research neutron source in the US. This source will be sited at ORNL and is being designed to serve the needs of the neutron science community well into the next century. The SNS consists of a 1.1-mA H- front end and a 1.0-GeV high-intensity pulsed proton linac. The 1-ms pulses from the linac will be compressed in a 221-m-circumference accumulator ring to produce 600-ns pulses at a 60-Hz rate. This accelerator system will produce spallation neutrons from a 1.0-MW liquid Hg target for a broad spectrum of neutron scattering research with an initial target hall containing 18 instruments. The baseline conceptual design, critical issues, upgrade possibilities, and the collaborative arrangement will be discussed. It is expected that SNS construction will commence in FY99 and, following a seven year project, start operation in 2006.

Forming images with thermal neutrons

NASA Astrophysics Data System (ADS)

Vanier, Peter E.; Forman, Leon

2003-01-01

Thermal neutrons passing through air have scattering lengths of about 20 meters. At further distances, the majority of neutrons emanating from a moderated source will scatter multiple times in the air before being detected, and will not retain information about the location of the source, except that their density will fall off somewhat faster than 1/r2. However, there remains a significant fraction of the neutrons that will travel 20 meters or more without scattering and can be used to create an image of the source. A few years ago, a proof-of-principle "camera" was demonstrated that could produce images of a scene containing sources of thermalized neutrons and could locate a source comparable in strength with an improvised nuclear device at ranges over 60 meters. The instrument makes use of a coded aperture with a uniformly redundant array of openings, analogous to those used in x-ray and gamma cameras. The detector is a position-sensitive He-3 proportional chamber, originally used for neutron diffraction. A neutron camera has many features in common with those designed for non-focusable photons, as well as some important differences. Potential applications include detecting nuclear smuggling, locating non-metallic land mines, assaying nuclear waste, and surveying for health physics purposes.

The angular dependence of pulse shape discrimination and detection sensitivity in cylindrical and cubic EJ-309 organic liquid scintillators

NASA Astrophysics Data System (ADS)

Jones, A. R.; Joyce, M. J.

2017-01-01

Liquid scintillators are used widely for neutron detection and for the assay of nuclear materials. However, due to the constituents of the detector and the nitrogen void within the detector cell, usually incorporated to accommodate any expansion that might occur to avoid leakage, fluctuations in detector response have been observed associated with the orientation of the detector when in use. In this work the angular dependence of the pulse-shape discrimination performance in an EJ309 liquid scintillator has been investigated with 252Cf in terms of the separation of γ -ray and neutron events, described quantitatively by the figure-of-merit. A subtle dependence in terms of pulse-shape discrimination is observed. In contrast, a more significant dependence of detection sensitivity with the angle of orientation is evident.

Program for studying fundamental interactions at the PIK reactor facilities

NASA Astrophysics Data System (ADS)

Serebrov, A. P.; Vassiljev, A. V.; Varlamov, V. E.; Geltenbort, P.; Gridnev, K. A.; Dmitriev, S. P.; Dovator, N. A.; Egorov, A. I.; Ezhov, V. F.; Zherebtsov, O. M.; Zinoviev, V. G.; Ivochkin, V. G.; Ivanov, S. N.; Ivanov, S. A.; Kolomensky, E. A.; Konoplev, K. A.; Krasnoschekova, I. A.; Lasakov, M. S.; Lyamkin, V. A.; Martemyanov, V. P.; Murashkin, A. N.; Neustroev, P. V.; Onegin, M. S.; Petelin, A. L.; Pirozhkov, A. N.; Polyushkin, A. O.; Prudnikov, D. V.; Ryabov, V. L.; Samoylov, R. M.; Sbitnev, S. V.; Fomin, A. K.; Fomichev, A. V.; Zimmer, O.; Cherniy, A. V.; Shoka, I. V.

2016-05-01

A research program aimed at studying fundamental interactions by means of ultracold and polarized cold neutrons at the GEK-4-4' channel of the PIK reactor is presented. The apparatus to be used includes a source of cold neutrons in the heavy-water reflector of the reactor, a source of ultracold neutrons based on superfluid helium and installed in a cold-neutron beam extracted from the GEK-4 channel, and a number of experimental facilities in neutron beams. An experiment devoted to searches for the neutron electric dipole moment and an experiment aimed at a measurement the neutron lifetime with the aid of a large gravitational trap are planned to be performed in a beam of ultracold neutrons. An experiment devoted to measuring neutron-decay asymmetries with the aid of a superconducting solenoid is planned in a beam of cold polarized neutrons from the GEK-4' channel. The second ultracold-neutron source and an experiment aimed at measuring the neutron lifetime with the aid of a magnetic trap are planned in the neutron-guide system of the GEK-3 channel. In the realms of neutrino physics, an experiment intended for sterile-neutrino searches is designed. The state of affairs around the preparation of the experimental equipment for this program is discussed.

Recent skyshine calculations at Jefferson Lab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Degtyarenko, P.

1997-12-01

New calculations of the skyshine dose distribution of neutrons and secondary photons have been performed at Jefferson Lab using the Monte Carlo method. The dose dependence on neutron energy, distance to the neutron source, polar angle of a source neutron, and azimuthal angle between the observation point and the momentum direction of a source neutron have been studied. The azimuthally asymmetric term in the skyshine dose distribution is shown to be important in the dose calculations around high-energy accelerator facilities. A parameterization formula and corresponding computer code have been developed which can be used for detailed calculations of the skyshinemore » dose maps.« less

Curved Waveguide Based Nuclear Fission for Small, Lightweight Reactors

NASA Technical Reports Server (NTRS)

Coker, Robert; Putnam, Gabriel

2012-01-01

The focus of the presented work is on the creation of a system of grazing incidence, supermirror waveguides for the capture and reuse of fission sourced neutrons. Within research reactors, neutron guides are a well known tool for directing neutrons from the confined and hazardous central core to a more accessible testing or measurement location. Typical neutron guides have rectangular, hollow cross sections, which are crafted as thin, mirrored waveguides plated with metal (commonly nickel). Under glancing angles with incoming neutrons, these waveguides can achieve nearly lossless transport of neutrons to distant instruments. Furthermore, recent developments have created supermirror surfaces which can accommodate neutron grazing angles up to four times as steep as nickel. A completed system will form an enclosing ring or spherical resonator system to a coupled neutron source for the purpose of capturing and reusing free neutrons to sustain and/or accelerate fission. While grazing incidence mirrors are a known method of directing and safely using neutrons, no method has been disclosed for capture and reuse of neutrons or sustainment of fission using a circular waveguide structure. The presented work is in the process of fabricating a functional, highly curved, neutron supermirror using known methods of Ni-Ti layering capable of achieving incident reflection angles up to four times steeper than nickel alone. Parallel work is analytically investigating future geometries, mirror compositions, and sources for enabling sustained fission with applicability to the propulsion and energy goals of NASA and other agencies. Should research into this concept prove feasible, it would lead to development of a high energy density, low mass power source potentially capable of sustaining fission with a fraction of the standard critical mass for a given material and a broadening of feasible materials due to reduced rates of release, absorption, and non-fission for neutrons. This advance could be applied to direct propulsion through guided fission products or as a secondary energy source for high impulse electric propulsion. It would help meet national needs for highly efficient energy sources with limited dependence on fossil fuels or conflict materials, and it would improve the use of low grade fissile materials which would help reduce national stockpiles and waste.

Overview of the Neutron experimental facilities at LANSCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mocko, Michal

2016-06-30

This presentation gives an overview of the neutron experimental facilities at LANSCE. The layout is mentioned in detail, with a map of the south-side experimental facilities, information on Target-4 and the Lujan Center. Then it goes into detail about neutron sources, specifically continuous versus pulsed. Target 4 is then discussed. In conclusion, we have introduced the south-side experimental facilities in operation at LANSCE. 1L target and Target 4 provide complementary neutron energy spectra. Two spallation neutron sources taken together cover more than 11 orders of magnitude in neutron energy.

A compact ion source for intense neutron generation

NASA Astrophysics Data System (ADS)

Perkins, Luke Torrilhon

Today, numerous applications for neutrons, beyond those of the nuclear power industry, are beginning to emerge and become viable. From neutron radiography which, not unlike conventional X-rays, can provide an in-depth image through various materials, to neutron radiotherapy, for the treatment of certain forms of cancer, all these applications promise to improve our quality of life. To meet the growing need for neutrons, greater demands are being made on the neutron 'generator' technology, demands for improved neutron output and reliability at reduced physical sizes and costs. One such example in the field of borehole neutron generators, where, through neutron activation analysis, the elemental composition, concentration and location in the surrounding borehole media can be ascertained. These generators, which commonly rely on the fusion of deuterium (D) and tritium (T) at energies of the order of one hundred thousand Volts, seem to defy their physical limitations to provide neutron outputs approaching a billion per second in packages no greater than two inches in diameter. In an attempt to answer this demand, we, at Lawrence Berkeley National Laboratory (LBNL), have begun developing a new generation of neutron generators making use of recent developments in ion source technology. The specific application which motivates this development is in the environmental monitoring field, where pollutants and their concentrations in the subsurface must be assessed. To achieve the desired direction of low-level concentrations and obtain a better directional sensitivity, a neutron output of 109 to 1010 D-T neutrons per second was targeted for generator package which can fit inside a ~5 cm diameter borehole. To accomplish this performance, a radio-frequency (RF)- driven ion source developed at LBNL was adapted to the requirements of this application. The advantages of this type of ion source are its intrinsic ability to tailor the delivery of RF power to the ion source and therefore control the neutron output (pulse width, repetition rate and magnitude) while operating at low pressures (~5 mTorr). In the experimental testing presented herein, a prototype, 5 cm-diameter, inductively driven ion source has produced unsaturated hydrogen beam current densities in excess of 1 A/cm2 and monatomic species fractions in excess of 90%. This satisfactory performance, with respect to the targeted neutron output, was achieved with a 2 MHz, 60 kW pulse of RF to produce a ~20μs plasma pulse at <100 Hz.

Radiological Characterization Technical Report on Californium-252 Sealed Source Transuranic Debris Waste for the Off-Site Source Recovery Project at Los Alamos National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feldman, Alexander

2014-04-24

This document describes the development and approach for the radiological characterization of Cf-252 sealed sources for shipment to the Waste Isolation Pilot Plant. The report combines information on the nuclear material content of each individual source (mass or activity and date of manufacture) with information and data on the radionuclide distributions within the originating nuclear material. This approach allows for complete and accurate characterization of the waste container without the need to take additional measurements. The radionuclide uncertainties, developed from acceptable knowledge (AK) information regarding the source material, are applied to the summed activities in the drum. The AK informationmore » used in the characterization of Cf-252 sealed sources has been qualified by the peer review process, which has been reviewed and accepted by the Environmental Protection Agency.« less

YAP:Ce scintillator characteristics for neutron detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Viererbl, L.; Klupak, V.; Vins, M.

2015-07-01

YAP:Ce (YAlO{sub 3}:Ce{sup +}, Yttrium Aluminum Perovskite, Ce{sup +} doped) crystals with appropriate converters seem like prospective scintillators for neutron detection. An important aspect for neutron detection with inorganic scintillators is the ability to discriminate neutron radiation from gamma radiation by pulse height of signals. For a detailed measurement of the aspect, a YAP:Ce crystal scintillator with lithium or hydrogen converters and a photomultiplier was used. A plutonium-beryllium neutron source and horizontal neutron channel beams of the LVR-15 research reactor were used as neutron sources. The measurement confirmed the possibility to use the YAP:Ce scintillator for neutron radiation detection. Themore » degree of discrimination between neutron and gamma radiation for different detection configurations was studied. (authors)« less

Triglyceride synthesis in epididymal adipose tissue: contribution of glucose and non-glucose carbon sources.

PubMed

Bederman, Ilya R; Foy, Steven; Chandramouli, Visvanathan; Alexander, James C; Previs, Stephen F

2009-03-06

The obesity epidemic has generated interest in determining the contribution of various pathways to triglyceride synthesis, including an elucidation of the origin of triglyceride fatty acids and triglyceride glycerol. We hypothesized that a dietary intervention would demonstrate the importance of using glucose versus non-glucose carbon sources to synthesize triglycerides in white adipose tissue. C57BL/6J mice were fed either a low fat, high carbohydrate (HC) diet or a high fat, carbohydrate-free (CF) diet and maintained on 2H2O (to determine total triglyceride dynamics) or infused with [6,6-(2)H]glucose (to quantify the contribution of glucose to triglyceride glycerol). The 2H2O labeling data demonstrate that although de novo lipogenesis contributed approximately 80% versus approximately 5% to the pool of triglyceride palmitate in HC- versus CF-fed mice, the epididymal adipose tissue synthesized approximately 1.5-fold more triglyceride in CF- versus HC-fed mice, i.e. 37+/-5 versus 25+/-3 micromolxday(-1). The [6,6-(2)H]glucose labeling data demonstrate that approximately 69 and approximately 28% of triglyceride glycerol is synthesized from glucose in HC- versus CF-fed mice, respectively. Although these data are consistent with the notion that non-glucose carbon sources (e.g. glyceroneogenesis) can make substantial contributions to the synthesis of triglyceride glycerol (i.e. the absolute synthesis of triglyceride glycerol from non-glucose substrates increased from approximately 8 to approximately 26 micromolxday(-1) in HC- versus CF-fed mice), these observations suggest (i) the importance of nutritional status in affecting flux rates and (ii) the operation of a glycerol-glucose cycle.

Research of fundamental interactions with use of ultracold neutrons

NASA Astrophysics Data System (ADS)

Serebrov, A. P.

2017-01-01

Use of ultracold neutrons (UCN) gives unique opportunities of a research of fundamental interactions in physics of elementary particles. Search of the electric dipole moment of a neutron (EDM) aims to test models of CP violation. Precise measurement of neutron lifetime is extremely important for cosmology and astrophysics. Considerable progress in these questions can be reached due to supersource of ultracold neutrons on the basis of superfluid helium which is under construction now in PNPI NRC KI. This source will allow us to increase density of ultracold neutrons approximately by 100 times in respect to the best UCN source at high flux reactor of Institute Laue-Langevin (Grenoble, France). Now the project and basic elements of the source are prepared, full-scale model of the source is tested, the scientific program is developed. Increase in accuracy of neutron EDM measurements by order of magnitude, down to level 10-27 -10-28 e cm is planned. It is highly important for physics of elementary particles. Accuracy of measurement of neutron lifetime can be increased by order of magnitude also. At last, at achievement of UCN density ˜ 103 - 104 cm-3, the experiment search for a neutron-antineutron oscillations using UCN will be possible. The present status of the project and its scientific program will be discussed.

The Macromolecular Neutron Diffractometer MaNDi at the Spallation Neutron Source

DOE PAGES

Coates, Leighton; Cuneo, Matthew J.; Frost, Matthew J.; ...

2015-07-18

The Macromolecular Neutron Diffractometer (MaNDi) is located on beamline 11B of the Spallation Neutron Source at Oak Ridge National Laboratory. Moreover, the instrument is a neutron time-of-flight wavelength-resolved Laue diffractometer optimized to collect diffraction data from single crystals. Finally, the instrument has been designed to provide flexibility in several instrumental parameters, such as beam divergence and wavelength bandwidth, to allow data collection from a range of macromolecular systems.

Fundamental neutron physics beamline at the spallation neutron source at ORNL

DOE PAGES

Fomin, N.; Greene, G. L.; Allen, R. R.; ...

2014-11-04

In this paper, we describe the Fundamental Neutron Physics Beamline (FnPB) facility located at the Spallation Neutron Source at Oak Ridge National Laboratory. The FnPB was designed for the conduct of experiments that investigate scientific issues in nuclear physics, particle physics, astrophysics and cosmology using a pulsed slow neutron beam. Finally, we present a detailed description of the design philosophy, beamline components, and measured fluxes of the polychromatic and monochromatic beams.

Towards a programme of testing and qualification for structural and plasma-facing materials in ‘fusion neutron’ environments

NASA Astrophysics Data System (ADS)

Stork, D.; Heidinger, R.; Muroga, T.; Zinkle, S. J.; Moeslang, A.; Porton, M.; Boutard, J.-L.; Gonzalez, S.; Ibarra, A.

2017-09-01

Materials damage by 14.1MeV neutrons from deuterium-tritium (D-T) fusion reactions can only be characterised definitively by subjecting a relevant configuration of test materials to high-intensity ‘fusion-neutron spectrum sources’, i.e. those simulating closely D-T fusion-neutron spectra. This provides major challenges to programmes to design and construct a demonstration fusion reactor prior to having a large-scale, high-intensity source of such neutrons. In this paper, we discuss the different aspects related to these ‘relevant configuration’ tests, including: • generic issues in materials qualification/validation, comparing safety requirements against those of investment protection; • lessons learned from the fission programme, enabling a reduced fusion materials testing programme; • the use and limitations of presently available possible irradiation sources to optimise a fusion neutron testing program including fission-neutron irradiation of isotopically and chemically tailored steels, ion damage by high-energy helium ions and self-ion beams, or irradiation studies with neutron sources of non-fusion spectra; and • the different potential sources of simulated fusion neutron spectra and the choice using stripping reactions from deuterium-beam ions incident on light-element targets.

Neutron skyshine measurements at Fermilab.

PubMed

Cossairt, J D; Coulson, L V

1985-02-01

Neutron skyshine has been a significant source of environmental radiation exposure at many high-energy proton accelerators. A particularly troublesome source of skyshine neutrons has existed at Fermilab during operation of the 400-GeV high-energy physics program. This paper reports on several measurements of this source made with a DePangher precision long counter at large distances. The spatial distribution of the neutron skyshine can approximately be described as an inverse square law dependence multiplied by an exponential with an approximate attenuation length of 1200 +/- 300 m. The absolute magnitude of the distributions can be matched directly to the conventionally measured absorbed dose distribution near the source.

X-Ray Measurements Of A Thermo Scientific P385 DD Neutron Generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wharton, C. J.; Seabury, E. H.; Chichester, D. L.

2011-06-01

Idaho National Laboratory is experimenting with electrical neutron generators, as potential replacements for californium-252 radioisotopic neutron sources in its PINS prompt gamma-ray neutron activation analysis (PGNAA) system for the identification of military chemical warfare agents and explosives. In addition to neutron output, we have recently measured the x-ray output of the Thermo Scientific P385 deuterium-deuterium neutron generator. X rays are a normal byproduct from neutron generators, but depending on their intensity and energy, x rays can interfere with gamma rays from the object under test, increase gamma-spectrometer dead time, and reduce PGNAA system throughput. The P385 x-ray energy spectrum wasmore » measured with a high-purity germanium (HPGe) detector, and a broad peak is evident at about 70 keV. To identify the source of the x rays within the neutron generator assembly, it was scanned by collimated scintillation detectors along its long axis. At the strongest x-ray emission points, the generator also was rotated 60 deg. between measurements. The scans show the primary source of x-ray emission from the P385 neutron generator is an area 60 mm from the neutron production target, in the vicinity of the ion source. Rotation of the neutron generator did not significantly alter the x-ray count rate, and its x-ray emission appears to be axially symmetric. A thin lead shield, 3.2 mm (1/8 inch) thick, reduced the 70-keV generator x rays to negligible levels.« less

X-Ray Measurements Of A Thermo Scientific P385 DD Neutron Generator

NASA Astrophysics Data System (ADS)

Wharton, C. J.; Seabury, E. H.; Chichester, D. L.; Caffrey, A. J.; Simpson, J.; Lemchak, M.

2011-06-01

Idaho National Laboratory is experimenting with electrical neutron generators, as potential replacements for californium-252 radioisotopic neutron sources in its PINS prompt gamma-ray neutron activation analysis (PGNAA) system for the identification of military chemical warfare agents and explosives. In addition to neutron output, we have recently measured the x-ray output of the Thermo Scientific P385 deuterium-deuterium neutron generator. X rays are a normal byproduct from neutron generators, but depending on their intensity and energy, x rays can interfere with gamma rays from the object under test, increase gamma-spectrometer dead time, and reduce PGNAA system throughput. The P385 x-ray energy spectrum was measured with a high-purity germanium (HPGe) detector, and a broad peak is evident at about 70 keV. To identify the source of the x rays within the neutron generator assembly, it was scanned by collimated scintillation detectors along its long axis. At the strongest x-ray emission points, the generator also was rotated 60° between measurements. The scans show the primary source of x-ray emission from the P385 neutron generator is an area 60 mm from the neutron production target, in the vicinity of the ion source. Rotation of the neutron generator did not significantly alter the x-ray count rate, and its x-ray emission appears to be axially symmetric. A thin lead shield, 3.2 mm (1/8 inch) thick, reduced the 70-keV generator x rays to negligible levels.

Hexagonal Uniformly Redundant Arrays (HURAs) for scintillator based coded aperture neutron imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gamage, K.A.A.; Zhou, Q.

2015-07-01

A series of Monte Carlo simulations have been conducted, making use of the EJ-426 neutron scintillator detector, to investigate the potential of using hexagonal uniformly redundant arrays (HURAs) for scintillator based coded aperture neutron imaging. This type of scintillator material has a low sensitivity to gamma rays, therefore, is of particular use in a system with a source that emits both neutrons and gamma rays. The simulations used an AmBe source, neutron images have been produced using different coded-aperture materials (boron- 10, cadmium-113 and gadolinium-157) and location error has also been estimated. In each case the neutron image clearly showsmore » the location of the source with a relatively small location error. Neutron images with high resolution can be easily used to identify and locate nuclear materials precisely in nuclear security and nuclear decommissioning applications. (authors)« less

Microtron MT 25 as a source of neutrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kralik, M.; Solc, J.; Chvatil, D.

2012-08-15

The objective was to describe Microtron MT25 as a source of neutrons generated by bremsstrahlung induced photonuclear reactions in U and Pb targets. Bremsstrahlung photons were produced by electrons accelerated at energy 21.6 MeV. Spectral fluence of the generated neutrons was calculated with MCNPX code and then experimentally determined at two positions by means of a Bonner spheres spectrometer in which the detector of thermal neutrons was replaced by activation Mn tablets or track detectors CR-39 with a {sup 10}B radiator. The measured neutron spectral fluence and the calculated anisotropy served for the estimation of neutron yield from the targetsmore » and for the determination of ambient dose equivalent rate at the place of measurement. Microtron MT25 is intended as one of the sources for testing neutron sensitive devices which will be sent into the space.« less

Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

NASA Astrophysics Data System (ADS)

Ito, T. M.; Adamek, E. R.; Callahan, N. B.; Choi, J. H.; Clayton, S. M.; Cude-Woods, C.; Currie, S.; Ding, X.; Fellers, D. E.; Geltenbort, P.; Lamoreaux, S. K.; Liu, C.-Y.; MacDonald, S.; Makela, M.; Morris, C. L.; Pattie, R. W.; Ramsey, J. C.; Salvat, D. J.; Saunders, A.; Sharapov, E. I.; Sjue, S.; Sprow, A. P.; Tang, Z.; Weaver, H. L.; Wei, W.; Young, A. R.

2018-01-01

The ultracold neutron (UCN) source at Los Alamos National Laboratory (LANL), which uses solid deuterium as the UCN converter and is driven by accelerator spallation neutrons, has been successfully operated for over 10 years, providing UCN to various experiments, as the first production UCN source based on the superthermal process. It has recently undergone a major upgrade. This paper describes the design and performance of the upgraded LANL UCN source. Measurements of the cold neutron spectrum and UCN density are presented and compared to Monte Carlo predictions. The source is shown to perform as modeled. The UCN density measured at the exit of the biological shield was 184 (32 ) UCN /cm3 , a fourfold increase from the highest previously reported. The polarized UCN density stored in an external chamber was measured to be 39 (7 ) UCN /cm3 , which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of σ (dn) =3 ×10-27e cm .

An Accelerator Neutron Source for BNCT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blue, Thomas, E

2006-03-14

The overall goal of this project was to develop an accelerator-based neutron source (ABNS) for Boron Neutron Capture Therapy (BNCT). Specifically, our goals were to design, and confirm by measurement, a target assembly and a moderator assembly that would fulfill the design requirements of the ABNS. These design requirements were 1) that the neutron field quality be as good as the neutron field quality for the reactor-based neutron sources for BNCT, 2) that the patient treatment time be reasonable, 3) that the proton current required to treat patients in reasonable times be technologially achievable at reasonable cost with good reliability,more » and accelerator space requirements which can be met in a hospital, and finally 4) that the treatment be safe for the patients.« less

Facile one-pot fabrication of nano-Fe3O4/carboxyl-functionalized baker's yeast composites and their application in methylene blue dye adsorption

NASA Astrophysics Data System (ADS)

Du, Zongjun; Zhang, Yue; Li, Zhengjie; Chen, Hui; Wang, Ying; Wang, Guangtu; Zou, Ping; Chen, Huaping; Zhang, Yunsong

2017-01-01

Nano-Fe3O4/carboxyl-functionalized baker's yeast composites (NF/CF-BYs) were prepared for the first time based on the ultrasonic cavitation assisted oxygen implosion method using single Fe2+ as iron source. The series of characterization analysis results showed that the obtained NF/CF-BYs had not only the superparamagnetic properties of nano-Fe3O4, but their surface also had plenty of functional groups (especially carboxyl groups) introduced by strong oxidization. The adsorption properties of NF/CF-BYs for methylene blue (MB) were also evaluated. The results displayed that the uptakes of NF/CF-BYs for MB were higher than that of pristine baker's yeast (P-BYs), and the adsorption process was followed by the pseudo-second-order kinetic model and Langmuir isotherm. The maximum adsorption capacity of NF/CF-BYs for MB was estimated to be 141.75 mg g-1 at pH 6. The regeneration efficiency of the obtained NF/CF-BYs was attained to be more than 90%.

Diffraction in neutron imaging-A review

NASA Astrophysics Data System (ADS)

Woracek, Robin; Santisteban, Javier; Fedrigo, Anna; Strobl, Markus

2018-01-01

Neutron imaging is a highly successful experimental technique ever since adequate neutron sources were available. In general, neutron imaging is performed with a wide wavelength spectrum for best flux conditions in transmission geometry. Neutrons provide outstanding features in the penetration of many structural materials, which often makes them more suited for bulk sample studies than other forms of radiation, often in particular as they are also highly sensitive to some light elements, especially Hydrogen. In contrast to neutron scattering applications, imaging resolves macroscopic structures, nowadays down to, in the best case, below 10 micrometre, directly in real space. However, since more than a decade there is a growing number of techniques and applications in neutron imaging that - supported by powerful neutron sources - are taking advantage of wavelength resolved measurements. In this review we summarize and discuss this outstanding development and how wavelength resolved transmission neutron imaging is successfully exploiting diffraction mechanisms to access crystal structure information in the Angstrom regime, which conventionally is probed in reciprocal space by diffraction techniques. In particular the combination of information gained in real space and on crystallographic length scales makes this neutron imaging technique a valuable tool for a wide range of new applications, while it also qualifies neutron imaging to fully profit from the new generation of powerful pulsed neutron sources.

Characterisation of an accelerator-based neutron source for BNCT versus beam energy

NASA Astrophysics Data System (ADS)

Agosteo, S.; Curzio, G.; d'Errico, F.; Nath, R.; Tinti, R.

2002-01-01

Neutron capture in 10B produces energetic alpha particles that have a high linear energy transfer in tissue. This results in higher cell killing and a higher relative biological effectiveness compared to photons. Using suitably designed boron compounds which preferentially localize in cancerous cells instead of healthy tissues, boron neutron capture therapy (BNCT) has the potential of providing a higher tumor cure rate within minimal toxicity to normal tissues. This clinical approach requires a thermal neutron source, generally a nuclear reactor, with a fluence rate sufficient to deliver tumorcidal doses within a reasonable treatment time (minutes). Thermal neutrons do not penetrate deeply in tissue, therefore BNCT is limited to lesions which are either superficial or otherwise accessible. In this work, we investigate the feasibility of an accelerator-based thermal neutron source for the BNCT of skin melanomas. The source was designed via MCNP Monte Carlo simulations of the thermalization of a fast neutron beam, generated by 7 MeV deuterons impinging on a thick target of beryllium. The neutron field was characterized at several deuteron energies (3.0-6.5 MeV) in an experimental structure installed at the Van De Graaff accelerator of the Laboratori Nazionali di Legnaro, in Italy. Thermal and epithermal neutron fluences were measured with activation techniques and fast neutron spectra were determined with superheated drop detectors (SDD). These neutron spectrometry and dosimetry studies indicated that the fast neutron dose is unacceptably high in the current design. Modifications to the current design to overcome this problem are presented.

The fast neutron fluence and the activation detector activity calculations using the effective source method and the adjoint function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hep, J.; Konecna, A.; Krysl, V.

2011-07-01

This paper describes the application of effective source in forward calculations and the adjoint method to the solution of fast neutron fluence and activation detector activities in the reactor pressure vessel (RPV) and RPV cavity of a VVER-440 reactor. Its objective is the demonstration of both methods on a practical task. The effective source method applies the Boltzmann transport operator to time integrated source data in order to obtain neutron fluence and detector activities. By weighting the source data by time dependent decay of the detector activity, the result of the calculation is the detector activity. Alternatively, if the weightingmore » is uniform with respect to time, the result is the fluence. The approach works because of the inherent linearity of radiation transport in non-multiplying time-invariant media. Integrated in this way, the source data are referred to as the effective source. The effective source in the forward calculations method thereby enables the analyst to replace numerous intensive transport calculations with a single transport calculation in which the time dependence and magnitude of the source are correctly represented. In this work, the effective source method has been expanded slightly in the following way: neutron source data were performed with few group method calculation using the active core calculation code MOBY-DICK. The follow-up neutron transport calculation was performed using the neutron transport code TORT to perform multigroup calculations. For comparison, an alternative method of calculation has been used based upon adjoint functions of the Boltzmann transport equation. Calculation of the three-dimensional (3-D) adjoint function for each required computational outcome has been obtained using the deterministic code TORT and the cross section library BGL440. Adjoint functions appropriate to the required fast neutron flux density and neutron reaction rates have been calculated for several significant points within the RPV and RPV cavity of the VVER-440 reacto rand located axially at the position of maximum power and at the position of the weld. Both of these methods (the effective source and the adjoint function) are briefly described in the present paper. The paper also describes their application to the solution of fast neutron fluence and detectors activities for the VVER-440 reactor. (authors)« less

Characteristics of a RF-Driven Ion Source for a Neutron Generator Used for Associated Particle Imaging

NASA Astrophysics Data System (ADS)

Wu, Ying; Hurley, John P.; Ji, Qing; Kwan, Joe; Leung, Ka-Ngo

2009-03-01

We present recent work on a prototype compact neutron generator for associated particle imaging (API). API uses alpha particles that are produced simultaneously with neutrons in the deuterium-tritium (2D(3T,n)4α) fusion reaction to determine the direction of the neutrons upon exiting the reaction. This method determines the spatial position of each neutron interaction and requires the neutrons to be generated from a small spot in order to achieve high spatial resolution. The ion source for API is designed to produce a focused ion beam with a beam spot diameter of 1-mm or less on the target. We use an axial type neutron generator with a predicted neutron yield of 108 n/s for a 50 μA D/T ion beam current accelerated to 80 kV. The generator utilizes an RF planar spiral antenna at 13.56 MHz to create a highly efficient inductively coupled plasma at the ion source. Experimental results show that beams with an atomic ion fraction of over 80% can be obtained while utilizing only 100 watts of RF power in the ion source. A single acceleration gap with a secondary electron suppression electrode is used in the tube. Experimental results from ion source testing, such as the current density, atomic ion fraction, electron temperature, and electron density will be discussed.

Relative intensities of 2. 5 and 14-MeV source neutrons from comparative responses of U-235 and U-238 detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jassby, D.L.; Hendel, H.W.; Bosch, H.S.

1988-05-01

The response of polyethylene-moderated U-235 fission counters is only weakly dependent on incident neutron energy, while the response of unmoderated U-238 or Th-232 fission counters increases strongly with energy. A given concentration of D-T neutrons in a mixed DT-DD source results in a unique relative detector response that depends on the parameters R14 and R2.5, where R14 is the ratio of the unmoderated U-238 and moderated U-235 detector efficiencies for a pure 14-MeV neutron source, and R2.5 is the corresponding ratio for a pure 2.5 MeV source. We have determined R14 and R2.5 using D-D and D-T neutron generators insidemore » the TFTR vacuum vessel. The results indicate that, for our detector geometry, the ratio of U-238 to U-235 count rates should increase by a factor of about 3 when the fusion neutron source changes from pure D-D to pure D-T. This calibration is being applied to recent TFTR /open quotes/supershot/close quotes/ data, where the uncollided neutron flux in the post-beam phase contains a high proportion of D-T neutrons from the burnup of D-D tritons. 8 refs., 4 figs,. 2 tabs.« less

Representing Simple Geometry Types in NetCDF-CF

NASA Astrophysics Data System (ADS)

Blodgett, D. L.; Koziol, B. W.; Whiteaker, T. L.; Simons, R.

2016-12-01

The Climate and Forecast (CF) metadata convention is well-suited for representing gridded and point-based observational datasets. However, CF currently has no accepted mechanism for representing simple geometry types such as lines and polygons. Lack of support for simple geometries within CF has unintentionally excluded a broad set of geoscientific data types from NetCDF-CF data encodings. For example, hydrologic datasets often contain polygon watershed catchments and polyline stream reaches in addition to point sampling stations and water management infrastructure. The latter has an associated CF specification. In the interest of supporting all simple geometry types within CF, a working group was formed following an EarthCube workshop on Advancing NetCDF-CF [1] to draft a CF specification for simple geometries: points, lines, polygons, and their associated multi-geometry representations [2]. The draft also includes parametric geometry types such as circles and ellipses. This presentation will provide an overview of the scope and content of the proposed specification focusing on mechanisms for representing coordinate arrays using variable length or continuous ragged arrays, capturing multi-geometries, and accounting for type-specific geometry artifacts such as polygon holes/interiors, node ordering, etc. The concepts contained in the specification proposal will be described with a use case representing streamflow in rivers and evapotranspiration from HUC12 watersheds. We will also introduce Python and R reference implementations developed alongside the technical specification. These in-development, open source Python and R libraries convert between commonly used GIS software objects (i.e. GEOS-based primitives) and their associated simple geometry CF representation. [1] http://www.unidata.ucar.edu/events/2016CFWorkshop/[2] https://github.com/bekozi/netCDF-CF-simple-geometry

The accelerator neutron source for boron neutron capture therapy

NASA Astrophysics Data System (ADS)

Kasatov, D.; Koshkarev, A.; Kuznetsov, A.; Makarov, A.; Ostreinov, Yu; Shchudlo, I.; Sorokin, I.; Sycheva, T.; Taskaev, S.; Zaidi, L.

2016-11-01

The accelerator based epithermal neutron source for Boron Neutron Capture Therapy (BNCT) is proposed, created and used in the Budker Institute of Nuclear Physics. In 2014, with the support of the Russian Science Foundation created the BNCT laboratory for the purpose to the end of 2016 get the neutron flux, suitable for BNCT. For getting 3 mA 2.3 MeV proton beam, was created a new type accelerator - tandem accelerator with vacuum isolation. On this moment, we have a stationary proton beam with 2.3 MeV and current 1.75 mA. Generation of neutrons is carried out by dropping proton beam on to lithium target as a result of threshold reaction 7Li(p,n)7Be. Established facility is a unique scientific installation. It provides a generating of neutron flux, including a monochromatic energy neutrons, gamma radiation, alpha-particles and positrons, and may be used by other research groups for carrying out scientific researches. The article describes an accelerator neutron source, presents and discusses the result of experiments and declares future plans.

Surface physics with cold and thermal neutron reflectometry. Progress report, April 1, 1991--September 30, 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steyerl, A.

1993-09-01

Within the past two and one half years of the project ``Surface Physics With Cold and Thermal Neutron Reflectometry`` a new thermal neutron reflectometer was constructed at the Rhode Island Nuclear Science Center (RINSC). It was used to study various liquid and solid surfaces. Furthermore, neutron reflection experiments were be un at different laboratories in collaboration with Dr. G.P. Fetcher (at Argonne National Laboratory), Dr. T. Russell (IBM Almaden) and Drs. S.K. Satija and A. Karim (at the National Institute for Standards and Technology). The available resources allowed partial construction of an imaging system for ultracold neutrons. It is expectedmore » to provide an extremely high resolution in momentum and energy transfer in surface studies using neutron reflectometry. Much of the work reported here was motivated by the possibility of later implementation at the planned Advanced Neutron Source at Oak Ridge. In a separate project the first concrete plans for an intense source of ultracold neutrons for the Advanced Neutron Source were developed.« less

Scalable Low-Power Deep Machine Learning with Analog Computation

DTIC Science & Technology

2013-07-19

transimpedance amplifier (TIA) that measures the output current 7 V Cf Vbias MP1 MN1 Vdd = 3 V 2.5 V 2.6 V + − Vox = 4.4 V 0.1 V + − 7 V Cf Vbias MP1 MN1 Vddt... amplifier . The amplifier has Cf as its feedback capacitor and the FG voltage Vfg as its input. The two MUXs at the sources of MP1 and MP2 control the...as a simple operational transconductor amplifier (OTA), converts voltage Vout to output current Iout. Vref determines the nominal voltage of Vout

Investigation of the heavy nuclei fission with anomalously high values of the fission fragments total kinetic energy

NASA Astrophysics Data System (ADS)

Khryachkov, Vitaly; Goverdovskii, Andrei; Ketlerov, Vladimir; Mitrofanov, Vecheslav; Sergachev, Alexei

2018-03-01

Binary fission of 232Th and 238U induced by fast neutrons were under intent investigation in the IPPE during recent years. These measurements were performed with a twin ionization chamber with Frisch grids. Signals from the detector were digitized for further processing with a specially developed software. It results in information of kinetic energies, masses, directions and Bragg curves of registered fission fragments. Total statistics of a few million fission events were collected during each experiment. It was discovered that for several combinations of fission fragment masses their total kinetic energy was very close to total free energy of the fissioning system. The probability of such fission events for the fast neutron induced fission was found to be much higher than for spontaneous fission of 252Cf and thermal neutron induced fission of 235U. For experiments with 238U target the energy of incident neutrons were 5 MeV and 6.5 MeV. Close analysis of dependence of fission fragment distribution on compound nucleus excitation energy gave us some explanation of the phenomenon. It could be a process in highly excited compound nucleus which leads the fissioning system from the scission point into the fusion valley with high probability.

Ultracold Neutron Sources

NASA Astrophysics Data System (ADS)

Martin, Jeffery

2016-09-01

The free neutron is an excellent laboratory for searches for physics beyond the standard model. Ultracold neutrons (UCN) are free neutrons that can be confined to material, magnetic, and gravitational traps. UCN are compelling for experiments requiring long observation times, high polarization, or low energies. The challenge of experiments has been to create enough UCN to reach the statistical precision required. Production techniques involving neutron interactions with condensed matter systems have resulted in some successes, and new UCN sources are being pursued worldwide to exploit higher UCN densities offered by these techniques. I will review the physics of how the UCN sources work, along with the present status of the world's efforts. research supported by NSERC, CFI, and CRC.

Time-correlated neutron analysis of a multiplying HEU source

NASA Astrophysics Data System (ADS)

Miller, E. C.; Kalter, J. M.; Lavelle, C. M.; Watson, S. M.; Kinlaw, M. T.; Chichester, D. L.; Noonan, W. A.

2015-06-01

The ability to quickly identify and characterize special nuclear material remains a national security challenge. In counter-proliferation applications, identifying the neutron multiplication of a sample can be a good indication of the level of threat. Currently neutron multiplicity measurements are performed with moderated 3He proportional counters. These systems rely on the detection of thermalized neutrons, a process which obscures both energy and time information from the source. Fast neutron detectors, such as liquid scintillators, have the ability to detect events on nanosecond time scales, providing more information on the temporal structure of the arriving signal, and provide an alternative method for extracting information from the source. To explore this possibility, a series of measurements were performed on the Idaho National Laboratory's MARVEL assembly, a configurable HEU source. The source assembly was measured in a variety of different HEU configurations and with different reflectors, covering a range of neutron multiplications from 2 to 8. The data was collected with liquid scintillator detectors and digitized for offline analysis. A gap based approach for identifying the bursts of detected neutrons associated with the same fission chain was used. Using this approach, we are able to study various statistical properties of individual fission chains. One of these properties is the distribution of neutron arrival times within a given burst. We have observed two interesting empirical trends. First, this distribution exhibits a weak, but definite, dependence on source multiplication. Second, there are distinctive differences in the distribution depending on the presence and type of reflector. Both of these phenomena might prove to be useful when assessing an unknown source. The physical origins of these phenomena can be illuminated with help of MCNPX-PoliMi simulations.

Electron volt spectroscopy on a pulsed neutron source

NASA Astrophysics Data System (ADS)

Newport, R. J.; Penfold, J.; Williams, W. G.

1984-07-01

The principal design aspects of a pulsed source neutron spectrometer in which the scattered neutron energy is determined by a resonance absorption filter difference method are discussed. Calculations of the accessible dynamic range, resolution and spectrum simulations are given for the spectrometer on a high intensity pulsed neutron source, such as the spallation neutron source (SNS) now being constructed at the Rutherford Appleton Laboratory. Special emphasis is made of the advantage gained by placing coarse and fixed energy-sensitive filters before and after the scatterer; these enhance the inelastic/elastic descrimination of the method. A brief description is given of a double difference filter method which gives a superior difference peak shape, as well as a better energy transfer resolution. Finally, some first results of scattering from zirconium hydride, obtained on a test spectrometer, are presented.

Uncertainty quantification in fission cross section measurements at LANSCE

DOE PAGES

Tovesson, F.

2015-01-09

Neutron-induced fission cross sections have been measured for several isotopes of uranium and plutonium at the Los Alamos Neutron Science Center (LANSCE) over a wide range of incident neutron energies. The total uncertainties in these measurements are in the range 3–5% above 100 keV of incident neutron energy, which results from uncertainties in the target, neutron source, and detector system. The individual sources of uncertainties are assumed to be uncorrelated, however correlation in the cross section across neutron energy bins are considered. The quantification of the uncertainty contributions will be described here.

A history of neutrons in biology: the development of neutron protein crystallography at BNL and LANL.

PubMed

Schoenborn, Benno P

2010-11-01

The first neutron diffraction data were collected from crystals of myoglobin almost 42 years ago using a step-scan diffractometer with a single detector. Since then, major advances have been made in neutron sources, instrumentation and data collection and analysis, and in biochemistry. Fundamental discoveries about enzyme mechanisms, biological complex structures, protein hydration and H-atom positions have been and continue to be made using neutron diffraction. The promise of neutrons has not changed since the first crystal diffraction data were collected. Today, with the developments of beamlines at spallation neutron sources and the use of the Laue method for data collection, the field of neutrons in structural biology has renewed vitality.

High-Resolution Fast-Neutron Spectrometry for Arms Control and Treaty Verification

DOE Office of Scientific and Technical Information (OSTI.GOV)

David L. Chichester; James T. Johnson; Edward H. Seabury

2012-07-01

Many nondestructive nuclear analysis techniques have been developed to support the measurement needs of arms control and treaty verification, including gross photon and neutron counting, low- and high-resolution gamma spectrometry, time-correlated neutron measurements, and photon and neutron imaging. One notable measurement technique that has not been extensively studied to date for these applications is high-resolution fast-neutron spectrometry (HRFNS). Applied for arms control and treaty verification, HRFNS has the potential to serve as a complimentary measurement approach to these other techniques by providing a means to either qualitatively or quantitatively determine the composition and thickness of non-nuclear materials surrounding neutron-emitting materials.more » The technique uses the normally-occurring neutrons present in arms control and treaty verification objects of interest as an internal source of neutrons for performing active-interrogation transmission measurements. Most low-Z nuclei of interest for arms control and treaty verification, including 9Be, 12C, 14N, and 16O, possess fast-neutron resonance features in their absorption cross sections in the 0.5- to 5-MeV energy range. Measuring the selective removal of source neutrons over this energy range, assuming for example a fission-spectrum starting distribution, may be used to estimate the stoichiometric composition of intervening materials between the neutron source and detector. At a simpler level, determination of the emitted fast-neutron spectrum may be used for fingerprinting 'known' assemblies for later use in template-matching tests. As with photon spectrometry, automated analysis of fast-neutron spectra may be performed to support decision making and reporting systems protected behind information barriers. This paper will report recent work at Idaho National Laboratory to explore the feasibility of using HRFNS for arms control and treaty verification applications, including simulations and experiments, using fission-spectrum neutron sources to assess neutron transmission through composite low-Z attenuators.« less

Final Report on Developing Microstructure-Property Correlation in Reactor Materials using in situ High-Energy X-rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Meimei; Almer, Jonathan D.; Yang, Yong

2016-01-01

This report provides a summary of research activities on understanding microstructure – property correlation in reactor materials using in situ high-energy X-rays. The report is a Level 2 deliverable in FY16 (M2CA-13-IL-AN_-0403-0111), under the Work Package CA-13-IL-AN_- 0403-01, “Microstructure-Property Correlation in Reactor Materials using in situ High Energy Xrays”, as part of the DOE-NE NEET Program. The objective of this project is to demonstrate the application of in situ high energy X-ray measurements of nuclear reactor materials under thermal-mechanical loading, to understand their microstructure-property relationships. The gained knowledge is expected to enable accurate predictions of mechanical performance of these materialsmore » subjected to extreme environments, and to further facilitate development of advanced reactor materials. The report provides detailed description of the in situ X-ray Radiated Materials (iRadMat) apparatus designed to interface with a servo-hydraulic load frame at beamline 1-ID at the Advanced Photon Source. This new capability allows in situ studies of radioactive specimens subject to thermal-mechanical loading using a suite of high-energy X-ray scattering and imaging techniques. We conducted several case studies using the iRadMat to obtain a better understanding of deformation and fracture mechanisms of irradiated materials. In situ X-ray measurements on neutron-irradiated pure metal and model alloy and several representative reactor materials, e.g. pure Fe, Fe-9Cr model alloy, 316 SS, HT-UPS, and duplex cast austenitic stainless steels (CASS) CF-8 were performed under tensile loading at temperatures of 20-400°C in vacuum. A combination of wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), and imaging techniques were utilized to interrogate microstructure at different length scales in real time while the specimen was subject to thermal-mechanical loading. In addition, in situ X-ray studies were complemented and benchmarked by ex situ characterization using advanced electron microscopy, atom probe tomography (APT) and micro/nano-indentation. The report presented in situ tensile test results on neutron-irradiated pure Fe, Fe-9Cr model alloy, 316 SS and CASS CF-8. These in situ experiments demonstrate the broad applications of the new capability in understanding several outstanding issues related to irradiated materials.« less

Thermal Neutron Imaging Using A New Pad-Based Position Sensitive Neutron Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dioszegi I.; Vanier P.E.; Salwen C.

2016-10-29

Thermal neutrons (with mean energy of 25 meV) have a scattering mean free path of about 20 m in air. Therefore it is feasible to find localized thermal neutron sources up to ~30 m standoff distance using thermal neutron imaging. Coded aperture thermal neutron imaging was developed in our laboratory in the nineties, using He-3 filled wire chambers. Recently a new generation of coded-aperture neutron imagers has been developed. In the new design the ionization chamber has anode and cathode planes, where the anode is composed of an array of individual pads. The charge is collected on each of themore » individual 5x5 mm2 anode pads, (48x48 in total, corresponding to 24x24 cm2 sensitive area) and read out by application specific integrated circuits (ASICs). The high sensitivity of the ASICs allows unity gain operation mode. The new design has several advantages for field deployable imaging applications, compared to the previous generation of wire-grid based neutron detectors. Among these are the rugged design, lighter weight and use of non-flammable stopping gas. For standoff localization of thermalized neutron sources a low resolution (11x11 pixel) coded aperture mask has been fabricated. Using the new larger area detector and the coarse resolution mask we performed several standoff experiments using moderated californium and plutonium sources at Idaho National Laboratory. In this paper we will report on the development and performance of the new pad-based neutron camera, and present long range coded-aperture images of various thermalized neutron sources.« less

Dietary intake of energy-dense, nutrient-poor and nutrient-dense food sources in children with cystic fibrosis.

PubMed

Sutherland, Rosie; Katz, Tamarah; Liu, Victoria; Quintano, Justine; Brunner, Rebecca; Tong, Chai Wei; Collins, Clare E; Ooi, Chee Y

2018-04-30

Prescription of a high-energy, high-fat diet is a mainstay of nutrition management in cystic fibrosis (CF). However, families may be relying on energy-dense, nutrient-poor (EDNP) foods rather than nutrient-dense (ND) foods to meet dietary targets. We aimed to evaluate the relative contribution of EDNP and ND foods to the usual diets of children with CF and identify sociodemographic factors associated with higher EDNP intakes. This is a cross-sectional comparison of children with CF aged 2-18 years and age- and gender-matched controls. Dietary intake was assessed using the Australian Child and Adolescent Eating Survey (ACAES) food frequency questionnaire. Children with CF (n = 80: 37 males; mean age 9.3 years) consumed significantly more EDNP foods than controls (mean age 9.8 years) in terms of both total energy (median [IQR]: 1301 kcal/day (843-1860) vs. 686 kcal/day (480-1032); p < 0.0001), and as a proportion of energy intake (median [IQR]: 44% (34-51) vs. 31% (24-43); p < 0.0001). Although children with CF met their estimated energy requirements (median [IQR]: 158% (124-187) vs. 112% (90-137); p < 0.0001) and their diets were high in fat (median [IQR]: 38% (35-41) vs. 34% (32-36); p < 0.0001), this was largely attributable to EDNP foods. High EDNP intakes (≥10 serves/day) were associated with socioeconomic disadvantage (p = 0.01) and rural residential location (p = 0.03). The energy- and fat-dense CF diet is primarily achieved by overconsumption of EDNP foods, rather than ND sources. This dietary pattern may not be optimal for the future health of children with CF, who are now expected to survive well into adulthood. Copyright © 2018 European Cystic Fibrosis Society. All rights reserved.

Occurrence of Pseudomonas aeruginosa in waters: implications for patients with cystic fibrosis (CF).

PubMed

Caskey, S; Stirling, J; Moore, J E; Rendall, J C

2018-06-01

Chronic Pseudomonas aeruginosa infection is associated with increased morbidity and mortality in patients with cystic fibrosis (CF). Current understanding of risk factors for acquisition is limited and so the aim of this study was to examine a large sample of environmental waters from diverse sources. Environmental water samples (n = 7904) from jacuzzis, hydrants, swimming pools, hot tubs, plunge pools, bottled natural mineral water, taps, springs, ice machines, water coolers, bores and showers were examined for the presence of P. aeruginosa. Pseudomonas aeruginosa was detected in 524/7904 (6·6%) waters examined. Hot tubs (51/243; 20·9%), tap water (3/40; 8%) and jacuzzis (432/5811; 7·4%) were the most likely environments where P. aeruginosa was isolated. Pseudomonas aeruginosa was isolated from bottled water (2/67; 3%). Our study highlights the ubiquitous nature of P. aeruginosa in the environment. Given CF patients are frequently counselled to make lifestyle changes to minimize P. aeruginosa exposure, these results have important implications. In particular, the occurrence of P. aeruginosa in tap water highlights the need to disinfect the CF patients' nebulizer after each use. This study examined a large number of water sources (n = 7904) over a 9-year period for the presence of Pseudomonas aeruginosa. The study highlighted that jacuzzis (n = 5811; 7% positive) and hot tubs had the highest occurrence of this organism (n = 243, 21% positive). Patients with cystic fibrosis (CF) are interested in knowing what water environments are likely to be contaminated with this organism, as this bacterium is an important cause of increased morbidity and mortality in such patients. With such information, CF patients and parents may make informed decisions about lifestyle choice and water environment avoidance. © 2018 The Society for Applied Microbiology.

The perturbation of backscattered fast neutrons spectrum caused by the resonances of C, N and O for possible use in pyromaterial detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abedin, Ahmad Firdaus Zainal, E-mail: firdaus087@gmail.com; Ibrahim, Noorddin; Zabidi, Noriza Ahmad

2015-04-29

Neutron radiation is able to determine the signature of land mine detection based on backscattering energy spectrum of landmine. In this study, the Monte Carlo simulation of backscattered fast neutrons was performed on four basic elements of land mine; hydrogen, nitrogen, oxygen and carbon. The moderation of fast neutrons to thermal neutrons and their resonances cross-section between 0.01 eV until 14 MeV were analysed. The neutrons energies were divided into 29 groups and ten million neutrons particles histories were used. The geometries consist of four main components: neutrons source, detectors, landmine and soil. The neutrons source was placed at the originmore » coordinate and shielded with carbon and polyethylene. Americium/Beryllium neutron source was placed inside lead casing of 1 cm thick and 2.5 cm height. Polyethylene was used to absorb and disperse radiation and was placed outside the lead shield of width 10 cm and height 7 cm. Two detectors were placed between source with distance of 8 cm and radius of 1.9 cm. Detectors of Helium-3 was used for neutron detection as it has high absorption cross section for thermal neutrons. For the anomaly, the physical is in cylinder form with radius of 10 cm and 8.9 cm height. The anomaly is buried 5 cm deep in the bed soil measured 80 cm radius and 53.5 cm height. The results show that the energy spectrum for the four basic elements of landmine with specific pattern which can be used as indication for the presence of landmines.« less

The Fundamental Neutron Physics Beamline at the Spallation Neutron Source.

PubMed

Greene, Geoffrey; Cianciolo, Vince; Koehler, Paul; Allen, Richard; Snow, William Michael; Huffman, Paul; Gould, Chris; Bowman, David; Cooper, Martin; Doyle, John

2005-01-01

The Spallation Neutron Source (SNS), currently under construction at Oak Ridge National Laboratory with an anticipated start-up in early 2006, will provide the most intense pulsed beams of cold neutrons in the world. At a projected power of 1.4 MW, the time averaged fluxes and fluences of the SNS will approach those of high flux reactors. One of the flight paths on the cold, coupled moderator will be devoted to fundamental neutron physics. The fundamental neutron physics beamline is anticipated to include two beam-lines; a broad band cold beam, and a monochromatic beam of 0.89 nm neutrons for ultracold neutron (UCN) experiments. The fundamental neutron physics beamline will be operated as a user facility with experiment selection based on a peer reviewed proposal process. An initial program of five experiments in neutron decay, hadronic weak interaction and time reversal symmetry violation have been proposed.

Characterization of the new neutron imaging and materials science facility IMAT

NASA Astrophysics Data System (ADS)

Minniti, Triestino; Watanabe, Kenichi; Burca, Genoveva; Pooley, Daniel E.; Kockelmann, Winfried

2018-04-01

IMAT is a new cold neutron imaging and diffraction instrument located at the second target station of the pulsed neutron spallation source ISIS, UK. A broad range of materials science and materials testing areas will be covered by IMAT. We present the characterization of the imaging part, including the energy-selective and energy-dispersive imaging options, and provide the basic parameters of the radiography and tomography instrument. In particular, detailed studies on mono and bi-dimensional neutron beam flux profiles, neutron flux as a function of the neutron wavelength, spatial and energy dependent neutron beam uniformities, guide artifacts, divergence and spatial resolution, and neutron pulse widths are provided. An accurate characterization of the neutron beam at the sample position, located 56 m from the source, is required to optimize collection of radiographic and tomographic data sets and for performing energy-dispersive neutron imaging via time-of-flight methods in particular.

Observation of Neutron Skyshine from an Accelerator Based Neutron Source

NASA Astrophysics Data System (ADS)

Franklyn, C. B.

2011-12-01

A key feature of neutron based interrogation systems is the need for adequate provision of shielding around the facility. Accelerator facilities adapted for fast neutron generation are not necessarily suitably equipped to ensure complete containment of the vast quantity of neutrons generated, typically >1011 nṡs-1. Simulating the neutron leakage from a facility is not a simple exercise since the energy and directional distribution can only be approximated. Although adequate horizontal, planar shielding provision is made for a neutron generator facility, it is sometimes the case that vertical shielding is minimized, due to structural and economic constraints. It is further justified by assuming the atmosphere above a facility functions as an adequate radiation shield. It has become apparent that multiple neutron scattering within the atmosphere can result in a measurable dose of neutrons reaching ground level some distance from a facility, an effect commonly known as skyshine. This paper describes a neutron detection system developed to monitor neutrons detected several hundred metres from a neutron source due to the effect of skyshine.

Neutron spectrometry in a mixed field of neutrons and protons with a phoswich neutron detector Part I: response functions for photons and neutrons of the phoswich neutron detector

NASA Astrophysics Data System (ADS)

Takada, M.; Taniguchi, S.; Nakamura, T.; Nakao, N.; Uwamino, Y.; Shibata, T.; Fujitaka, K.

2001-06-01

We have developed a phoswich neutron detector consisting of an NE213 liquid scintillator surrounded by an NE115 plastic scintillator to distinguish photon and neutron events in a charged-particle mixed field. To obtain the energy spectra by unfolding, the response functions to neutrons and photons were obtained by the experiment and calculation. The response functions to photons were measured with radionuclide sources, and were calculated with the EGS4-PRESTA code. The response functions to neutrons were measured with a white neutron source produced by the bombardment of 135 MeV protons onto a Be+C target using a TOF method, and were calculated with the SCINFUL code, which we revised in order to calculate neutron response functions up to 135 MeV. Based on these experimental and calculated results, response matrices for photons up to 20 MeV and neutrons up to 132 MeV could finally be obtained.

Industrial ion source technology

NASA Technical Reports Server (NTRS)

Kaufman, H. R.; Robinson, R. S.

1979-01-01

In reactive ion etching of Si, varying amounts of O2 were added to the CF4 background. The experimental results indicated an etch rate less than that for Ar up to an O2 partial pressure of about .00006 Torr. Above this O2 pressure, the etch rate with CF4 exceeded that with Ar alone. For comparison the random arrival rate of O2 was approximately equal to the ion arrival rate at a partial pressure of about .00002 Torr. There were also ion source and ion pressure gauge maintenance problems as a result of the use of CF4. Large scale (4 sq cm) texturing of Si was accomplished using both Cu and stainless steel seed. The most effective seeding method for this texturing was to surround the sample with large inclined planes. Designing, fabricating, and testing a 200 sq cm rectangular beam ion source was emphasized. The design current density was 6 mA/sq cm with 500 eV argon ions, although power supply limitations permitted operation to only 2 mA/sq cm. The use of multiple rectangular beam ion sources for continuous processing of wider areas than would be possible with a single source was also studied. In all cases investigated, the most uniform coverage was obtained with 0 to 2 cm beam overlay. The maximum departure from uniform processing at optimum beam overlap was found to be +15%.

A comparison of untagged gamma-ray and tagged-neutron yields from 241AmBe and 238PuBe sources.

PubMed

Scherzinger, J; Al Jebali, R; Annand, J R M; Fissum, K G; Hall-Wilton, R; Koufigar, S; Mauritzson, N; Messi, F; Perrey, H; Rofors, E

2017-09-01

Untagged gamma-ray and tagged-neutron yields from 241 AmBe and 238 PuBe mixed-field sources have been measured. Gamma-ray spectroscopy measurements from 1 to 5MeV were performed in an open environment using a CeBr 3 detector and the same experimental conditions for both sources. The shapes of the distributions are very similar and agree well with previous data. Tagged-neutron measurements from 2 to 6MeV were performed in a shielded environment using a NE-213 liquid-scintillator detector for the neutrons and a YAP(Ce) detector to tag the 4.44MeVgamma-rays associated with the de-excitation of the first-excited state of 12 C. Again, the same experimental conditions were used for both sources. The shapes of these distributions are also very similar and agree well with previous data, each other, and the ISO recommendation. Our 238 PuBe source provides approximately 2.6 times more 4.44MeVgamma-rays and 2.4 times more neutrons over the tagged-neutron energy range, the latter in reasonable agreement with the original full-spectrum source-calibration measurements performed at the time of their acquisition. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Indoor Fast Neutron Generator for Biophysical and Electronic Applications

NASA Astrophysics Data System (ADS)

Cannuli, A.; Caccamo, M. T.; Marchese, N.; Tomarchio, E. A.; Pace, C.; Magazù, S.

2018-05-01

This study focuses the attention on an indoor fast neutron generator for biophysical and electronic applications. More specifically, the findings obtained by several simulations with the MCNP Monte Carlo code, necessary for the realization of a shield for indoor measurements, are presented. Furthermore, an evaluation of the neutron spectrum modification caused by the shielding is reported. Fast neutron generators are a valid and interesting available source of neutrons, increasingly employed in a wide range of research fields, such as science and engineering. The employed portable pulsed neutron source is a MP320 Thermo Scientific neutron generator, able to generate 2.5 MeV neutrons with a neutron yield of 2.0 x 106 n/s, a pulse rate of 250 Hz to 20 KHz and a duty factor varying from 5% to 100%. The neutron generator, based on Deuterium-Deuterium nuclear fusion reactions, is employed in conjunction with a solid-state photon detector, made of n-type high-purity germanium (PINS-GMX by ORTEC) and it is mainly addressed to biophysical and electronic studies. The present study showed a proposal for the realization of a shield necessary for indoor applications for MP320 neutron generator, with a particular analysis of the transport of neutrons simulated with Monte Carlo code and described the two main lines of research in which the source will be used.

Prediction of Compressional Wave Velocity Using Regression and Neural Network Modeling and Estimation of Stress Orientation in Bokaro Coalfield, India

NASA Astrophysics Data System (ADS)

Paul, Suman; Ali, Muhammad; Chatterjee, Rima

2018-01-01

Velocity of compressional wave ( V P) of coal and non-coal lithology is predicted from five wells from the Bokaro coalfield (CF), India. Shear sonic travel time logs are not recorded for all wells under the study area. Shear wave velocity ( Vs) is available only for two wells: one from east and other from west Bokaro CF. The major lithologies of this CF are dominated by coal, shaly coal of Barakar formation. This paper focuses on the (a) relationship between Vp and Vs, (b) prediction of Vp using regression and neural network modeling and (c) estimation of maximum horizontal stress from image log. Coal characterizes with low acoustic impedance (AI) as compared to the overlying and underlying strata. The cross-plot between AI and Vp/ Vs is able to identify coal, shaly coal, shale and sandstone from wells in Bokaro CF. The relationship between Vp and Vs is obtained with excellent goodness of fit ( R 2) ranging from 0.90 to 0.93. Linear multiple regression and multi-layered feed-forward neural network (MLFN) models are developed for prediction Vp from two wells using four input log parameters: gamma ray, resistivity, bulk density and neutron porosity. Regression model predicted Vp shows poor fit (from R 2 = 0.28) to good fit ( R 2 = 0.79) with the observed velocity. MLFN model predicted Vp indicates satisfactory to good R2 values varying from 0.62 to 0.92 with the observed velocity. Maximum horizontal stress orientation from a well at west Bokaro CF is studied from Formation Micro-Imager (FMI) log. Breakouts and drilling-induced fractures (DIFs) are identified from the FMI log. Breakout length of 4.5 m is oriented towards N60°W whereas the orientation of DIFs for a cumulative length of 26.5 m is varying from N15°E to N35°E. The mean maximum horizontal stress in this CF is towards N28°E.