MCNP-REN - A Monte Carlo Tool for Neutron Detector Design Without Using the Point Model

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

Abhold, M.E.; Baker, M.C.

1999-07-25

The development of neutron detectors makes extensive use of the predictions of detector response through the use of Monte Carlo techniques in conjunction with the point reactor model. Unfortunately, the point reactor model fails to accurately predict detector response in common applications. For this reason, the general Monte Carlo N-Particle code (MCNP) was modified to simulate the pulse streams that would be generated by a neutron detector and normally analyzed by a shift register. This modified code, MCNP - Random Exponentially Distributed Neutron Source (MCNP-REN), along with the Time Analysis Program (TAP) predict neutron detector response without using the pointmore » reactor model, making it unnecessary for the user to decide whether or not the assumptions of the point model are met for their application. MCNP-REN is capable of simulating standard neutron coincidence counting as well as neutron multiplicity counting. Measurements of MOX fresh fuel made using the Underwater Coincidence Counter (UWCC) as well as measurements of HEU reactor fuel using the active neutron Research Reactor Fuel Counter (RRFC) are compared with calculations. The method used in MCNP-REN is demonstrated to be fundamentally sound and shown to eliminate the need to use the point model for detector performance predictions.« less

High-field neutral beam injection for improving the Q of a gas dynamic trap-based fusion neutron source

NASA Astrophysics Data System (ADS)

Zeng, Qiusun; Chen, Dehong; Wang, Minghuang

2017-12-01

In order to improve the fusion energy gain (Q) of a gas dynamic trap (GDT)-based fusion neutron source, a method in which the neutral beam is obliquely injected at a higher magnetic field position rather than at the mid-plane of the GDT is proposed. This method is beneficial for confining a higher density of fast ions at the turning point in the zone with a higher magnetic field, as well as obtaining a higher mirror ratio by reducing the mid-plane field rather than increasing the mirror field. In this situation, collision scattering loss of fast ions with higher density will occur and change the confinement time, power balance and particle balance. Using an updated calculation model with high-field neutral beam injection for a GDT-based fusion neutron source conceptual design, we got four optimal design schemes for a GDT-based fusion neutron source in which Q was improved to two- to three-fold compared with a conventional design scheme and considering the limitation for avoiding plasma instabilities, especially the fire-hose instability. The distribution of fast ions could be optimized by building a proper magnetic field configuration with enough space for neutron shielding and by multi-beam neutral particle injection at different axial points.

D-T Neutron Skyshine Experiments at JAERI/FNS

NASA Astrophysics Data System (ADS)

Nishitani, Takeo; Ochiai, Kentaro; Yoshida, Shigeo; Tanaka, Ryohei; Wakisaka, Masashi; Nakao, Makoto; Sato, Satoshi; Yamauchi, Michinori; Hori, Jun-Ichi; Takahashi, Akito; Kaneko, Jun-Ichi; Sawamura, Teruko

The D-T neutron skyshine experiments have been carried out at the Fusion Neutronics Source (FNS) of JAERI with the neutron yield of ˜1.7×1011n/s. The concrete thickness of the roof and the wall of a FNS target room are 1.15 and 2 m, respectively. The FNS skyshine port with a size of 0.9 × 0.9 m2 was open during the experimental period.The radiation dose rate outside the target room was measured as far as about 550 m away from the D-T target point with a spherical rem-counter. The highest neutron dose was about 0.5 μSv/hr at a distance of 30 m from the D-T target point and the dose rate was attenuated to 0.002 μSv/hr at a distance of 550 m. The measured neutron dose distribution was analyzed with Monte Carlo code MCNP-4B and a simple line source model. The MCNP calculation overestimates the neutron dose in the distance range larger than 250 m. The neutron spectra were evaluated with a 3He detector with different thickness of polyethylene neutron moderators. Secondary gamma-rays were measured with high purity Ge detectors and NaI scintillation detectors.

Study on beam geometry and image reconstruction algorithm in fast neutron computerized tomography at NECTAR facility

NASA Astrophysics Data System (ADS)

Guo, J.; Bücherl, T.; Zou, Y.; Guo, Z.

2011-09-01

Investigations on the fast neutron beam geometry for the NECTAR facility are presented. The results of MCNP simulations and experimental measurements of the beam distributions at NECTAR are compared. Boltzmann functions are used to describe the beam profile in the detection plane assuming the area source to be set up of large number of single neutron point sources. An iterative algebraic reconstruction algorithm is developed, realized and verified by both simulated and measured projection data. The feasibility for improved reconstruction in fast neutron computerized tomography at the NECTAR facility is demonstrated.

IMPROVEMENTS IN THE THERMAL NEUTRON CALIBRATION UNIT, TNF2, AT LNMRI/IRD.

PubMed

Astuto, A; Fernandes, S S; Patrão, K C S; Fonseca, E S; Pereira, W W; Lopes, R T

2018-02-21

The standard thermal neutron flux unit, TNF2, in the Brazilian National Ionizing Radiation Metrology Laboratory was rebuilt. Fluence is still achieved by moderating of four 241Am-Be sources with 0.6 TBq each. The facility was again simulated and redesigned with graphite core and paraffin added graphite blocks surrounding it. Simulations using the MCNPX code on different geometric arrangements of moderator materials and neutron sources were performed. The resulting neutron fluence quality in terms of intensity, spectrum and cadmium ratio was evaluated. After this step, the system was assembled based on the results obtained from the simulations and measurements were performed with equipment existing in LNMRI/IRD and by simulated equipment. This work focuses on the characterization of a central chamber point and external points around the TNF2 in terms of neutron spectrum, fluence and ambient dose equivalent, H*(10). This system was validated with spectra measurements, fluence and H*(10) to ensure traceability.

Neutron Imaging Control Report: FY 2016

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

Gibson, D. J.

2016-11-30

During the 2016 fiscal year, work began on the supervision and control systems for the neutron source currently under construction in the B194 accelerator caves. This source relies on a deuteron beam colliding with a high-speed stream of deuterium gas to create neutrons, which poses significant technical challenges. To help overcome those challenges, an integrated, operator-focused control architecture is required to collect and assimilate disparate data from a variety of measurement points, as well as provide the means to remotely control the system hardware.

Neutron streak camera

DOEpatents

Wang, C.L.

1981-05-14

Apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon.

Neutron streak camera

DOEpatents

Wang, Ching L.

1983-09-13

Apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon.

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

Analysis of neutron and gamma-ray streaming along the maze of NRCAM thallium production target room.

PubMed

Raisali, G; Hajiloo, N; Hamidi, S; Aslani, G

2006-08-01

Study of the shield performance of a thallium-203 production target room has been investigated in this work. Neutron and gamma-ray equivalent dose rates at various points of the maze are calculated by simulating the transport of streaming neutrons, and photons using Monte Carlo method. For determination of neutron and gamma-ray source intensities and their energy spectrum, we have applied SRIM 2003 and ALICE91 computer codes to Tl target and its Cu substrate for a 145 microA of 28.5 MeV protons beam. The MCNP/4C code has been applied with neutron source term in mode n p to consider both prompt neutrons and secondary gamma-rays. Then the code is applied for the prompt gamma-rays as the source term. The neutron-flux energy spectrum and equivalent dose rates for neutron and gamma-rays in various positions in the maze have been calculated. It has been found that the deviation between calculated and measured dose values along the maze is less than 20%.

New constraints on neutron star models of gamma-ray bursts. II - X-ray observations of three gamma-ray burst error boxes

NASA Technical Reports Server (NTRS)

Boer, M.; Hurley, K.; Pizzichini, G.; Gottardi, M.

1991-01-01

Exosat observations are presented for 3 gamma-ray-burst error boxes, one of which may be associated with an optical flash. No point sources were detected at the 3-sigma level. A comparison with Einstein data (Pizzichini et al., 1986) is made for the March 5b, 1979 source. The data are interpreted in the framework of neutron star models and derive upper limits for the neutron star surface temperatures, accretion rates, and surface densities of an accretion disk. Apart from the March 5b, 1979 source, consistency is found with each model.

Neutron streak camera

DOEpatents

Wang, C.L.

1983-09-13

Disclosed is an apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon. 4 figs.

The suite of small-angle neutron scattering instruments at Oak Ridge National Laboratory

DOE PAGES

Heller, William T.; Cuneo, Matthew J.; Debeer-Schmitt, Lisa M.; ...

2018-02-21

Oak Ridge National Laboratory is home to the High Flux Isotope Reactor (HFIR), a high-flux research reactor, and the Spallation Neutron Source (SNS), the world's most intense source of pulsed neutron beams. The unique co-localization of these two sources provided an opportunity to develop a suite of complementary small-angle neutron scattering instruments for studies of large-scale structures: the GP-SANS and Bio-SANS instruments at the HFIR and the EQ-SANS and TOF-USANS instruments at the SNS. This article provides an overview of the capabilities of the suite of instruments, with specific emphasis on how they complement each other. As a result, amore » description of the plans for future developments including greater integration of the suite into a single point of entry for neutron scattering studies of large-scale structures is also provided.« less

The suite of small-angle neutron scattering instruments at Oak Ridge National Laboratory

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

Heller, William T.; Cuneo, Matthew J.; Debeer-Schmitt, Lisa M.

Oak Ridge National Laboratory is home to the High Flux Isotope Reactor (HFIR), a high-flux research reactor, and the Spallation Neutron Source (SNS), the world's most intense source of pulsed neutron beams. The unique co-localization of these two sources provided an opportunity to develop a suite of complementary small-angle neutron scattering instruments for studies of large-scale structures: the GP-SANS and Bio-SANS instruments at the HFIR and the EQ-SANS and TOF-USANS instruments at the SNS. This article provides an overview of the capabilities of the suite of instruments, with specific emphasis on how they complement each other. As a result, amore » description of the plans for future developments including greater integration of the suite into a single point of entry for neutron scattering studies of large-scale structures is also provided.« less

Calibration of neutron detectors on the Joint European Torus.

PubMed

Batistoni, Paola; Popovichev, S; Conroy, S; Lengar, I; Čufar, A; Abhangi, M; Snoj, L; Horton, L

2017-10-01

The present paper describes the findings of the calibration of the neutron yield monitors on the Joint European Torus (JET) performed in 2013 using a 252 Cf source deployed inside the torus by the remote handling system, with particular regard to the calibration of fission chambers which provide the time resolved neutron yield from JET plasmas. The experimental data obtained in toroidal, radial, and vertical scans are presented. These data are first analysed following an analytical approach adopted in the previous neutron calibrations at JET. In this way, a calibration function for the volumetric plasma source is derived which allows us to understand the importance of the different plasma regions and of different spatial profiles of neutron emissivity on fission chamber response. Neutronics analyses have also been performed to calculate the correction factors needed to derive the plasma calibration factors taking into account the different energy spectrum and angular emission distribution of the calibrating (point) 252 Cf source, the discrete positions compared to the plasma volumetric source, and the calibration circumstances. All correction factors are presented and discussed. We discuss also the lessons learnt which are the basis for the on-going 14 MeV neutron calibration at JET and for ITER.

The first IEC fusion industrial neutron generator and developments

NASA Astrophysics Data System (ADS)

Sved, John

1999-06-01

Inertial Electrostatic Confinement fusion grade plasma containment has been sporadically researched since the early 1960's. In the 1990's the work of G. H. Miley and his team at the University of Illinios, Fusion Studies Laboratory, Champaign-Urbana has stimulated a collaboration with industry. The development and test program for the first industrial IEC neutron generator has progressed to the point where an endurance test is under way to demonstrate at least 10,000 hours of operational life of the sealed chamber device without servicing. The market entry goals of steady 107 D-D n/s CW output with an air-cooled system have been achieved. DASA has invested in the development of the industrial product and the continuing basic research at the UI-FSL. The complete DASA FusionStar IEC-PS1 point source neutron generator set is described with emphasis on the interfaces to user NAA systems. The next product developments are pulsed neutron operations and higher fusion reaction rates of up to 1010 by means of affordable add-ons to the basic IEC-PS system. The production engineering experience gained will next be applied to a more challenging line source variant of the IEC. Beyond neutron and proton sources, several other IEC applications are being developed.

Does the finite size of the proto-neutron star preclude supernova neutrino flavor scintillation due to turbulence?

DOE PAGES

Kneller, James P.; Mauney, Alex W.

2013-08-23

Here, the transition probabilities describing the evolution of a neutrino with a given energy along some ray through a turbulent supernova profile are random variates unique to each ray. If the proto-neutron-star source of the neutrinos were a point, then one might expect the evolution of the turbulence would cause the flavor composition of the neutrinos to vary in time i.e. the flavor would scintillate. But in reality the proto-neutron star is not a point source—it has a size of order ˜10km, so the neutrinos emitted from different points at the source will each have seen different turbulence. The finitemore » source size will reduce the correlation of the flavor transition probabilities along different trajectories and reduce the magnitude of the flavor scintillation. To determine whether the finite size of the proto-neutron star will preclude flavor scintillation, we calculate the correlation of the neutrino flavor transition probabilities through turbulent supernova profiles as a function of the separation δx between the emission points. The correlation will depend upon the power spectrum used for the turbulence, and we consider two cases: when the power spectrum is isotropic, and the more realistic case of a power spectrum which is anisotropic on large scales and isotropic on small. Although it is dependent on a number of uncalibrated parameters, we show the supernova neutrino source is not of sufficient size to significantly blur flavor scintillation in all mixing channels when using an isotropic spectrum, and this same result holds when using an anisotropic spectrum, except when we greatly reduce the similarity of the turbulence along parallel trajectories separated by ˜10km or less.« less

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.

Hybrid Skyshine Calculations for Complex Neutron and Gamma-Ray Sources

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

Shultis, J. Kenneth

2000-10-15

A two-step hybrid method is described for computationally efficient estimation of neutron and gamma-ray skyshine doses far from a shielded source. First, the energy and angular dependence of radiation escaping into the atmosphere from a source containment is determined by a detailed transport model such as MCNP. Then, an effective point source with this energy and angular dependence is used in the integral line-beam method to transport the radiation through the atmosphere up to 2500 m from the source. An example spent-fuel storage cask is analyzed with this hybrid method and compared to detailed MCNP skyshine calculations.

Energy resolution of pulsed neutron beam provided by the ANNRI beamline at the J-PARC/MLF

NASA Astrophysics Data System (ADS)

Kino, K.; Furusaka, M.; Hiraga, F.; Kamiyama, T.; Kiyanagi, Y.; Furutaka, K.; Goko, S.; Hara, K. Y.; Harada, H.; Harada, M.; Hirose, K.; Kai, T.; Kimura, A.; Kin, T.; Kitatani, F.; Koizumi, M.; Maekawa, F.; Meigo, S.; Nakamura, S.; Ooi, M.; Ohta, M.; Oshima, M.; Toh, Y.; Igashira, M.; Katabuchi, T.; Mizumoto, M.; Hori, J.

2014-02-01

We studied the energy resolution of the pulsed neutron beam of the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) at the Japan Proton Accelerator Research Complex/Materials and Life Science Experimental Facility (J-PARC/MLF). A simulation in the energy region from 0.7 meV to 1 MeV was performed and measurements were made at thermal (0.76-62 meV) and epithermal energies (4.8-410 eV). The neutron energy resolution of ANNRI determined by the time-of-flight technique depends on the time structure of the neutron pulse. We obtained the neutron energy resolution as a function of the neutron energy by the simulation in the two operation modes of the neutron source: double- and single-bunch modes. In double-bunch mode, the resolution deteriorates above about 10 eV because the time structure of the neutron pulse splits into two peaks. The time structures at 13 energy points from measurements in the thermal energy region agree with those of the simulation. In the epithermal energy region, the time structures at 17 energy points were obtained from measurements and agree with those of the simulation. The FWHM values of the time structures by the simulation and measurements were found to be almost consistent. In the single-bunch mode, the energy resolution is better than about 1% between 1 meV and 10 keV at a neutron source operation of 17.5 kW. These results confirm the energy resolution of the pulsed neutron beam produced by the ANNRI beamline.

Physicsdesign point for a 1MW fusion neutron source

NASA Astrophysics Data System (ADS)

Woodruff, Simon; Melnik, Paul; Sieck, Paul; Stuber, James; Romero-Talamas, Carlos; O'Bryan, John; Miller, Ronald

2016-10-01

We are developing a design point for a spheromak experiment heated by adiabatic compression for use as a compact neutron source. We utilize the CORSICA and NIMROD MHD codes as well as analytic modeling to assess a concept with target parameters R0 =0.5m, Rf =0.17m, T0 =1keV, Tf =8keV, n0 =2e20m-3 and nf = 5e21m-3, with radial convergence of C =R0/Rf =3. We present results from CORSICA showing the placement of coils and passive structure to ensure stability during compression. We specify target parameters for the compression in terms of plasma beta, formation efficiency and energy confinement. We present results simulations of magnetic compression using the NIMROD code to examine the role of rotation on the stability and confinement of the spheromak as it is compressed. Supported by DARPA Grant N66001-14-1-4044 and IAEA CRP on Compact Fusion Neutron Sources.

A Northern Sky Survey for Point-like Sources of EeV Neutral Particles with the Telescope Array Experiment

NASA Astrophysics Data System (ADS)

Abbasi, R. U.; Abe, M.; Abu-Zayyad, T.; Allen, M.; Anderson, R.; Azuma, R.; Barcikowski, E.; Belz, J. W.; Bergman, D. R.; Blake, S. A.; Cady, R.; Chae, M. J.; Cheon, B. G.; Chiba, J.; Chikawa, M.; Cho, W. R.; Fujii, T.; Fukushima, M.; Goto, T.; Hanlon, W.; Hayashi, Y.; Hayashida, N.; Hibino, K.; Honda, K.; Ikeda, D.; Inoue, N.; Ishii, T.; Ishimori, R.; Ito, H.; Ivanov, D.; Jui, C. C. H.; Kadota, K.; Kakimoto, F.; Kalashev, O.; Kasahara, K.; Kawai, H.; Kawakami, S.; Kawana, S.; Kawata, K.; Kido, E.; Kim, H. B.; Kim, J. H.; Kim, J. H.; Kitamura, S.; Kitamura, Y.; Kuzmin, V.; Kwon, Y. J.; Lan, J.; Lim, S. I.; Lundquist, J. P.; Machida, K.; Martens, K.; Matsuda, T.; Matsuyama, T.; Matthews, J. N.; Minamino, M.; Mukai, K.; Myers, I.; Nagasawa, K.; Nagataki, S.; Nakamura, T.; Nonaka, T.; Nozato, A.; Ogio, S.; Ogura, J.; Ohnishi, M.; Ohoka, H.; Oki, K.; Okuda, T.; Ono, M.; Oshima, A.; Ozawa, S.; Park, I. H.; Pshirkov, M. S.; Rodriguez, D. C.; Rubtsov, G.; Ryu, D.; Sagawa, H.; Sakurai, N.; Sampson, A. L.; Scott, L. M.; Shah, P. D.; Shibata, F.; Shibata, T.; Shimodaira, H.; Shin, B. K.; Smith, J. D.; Sokolsky, P.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Stroman, T. A.; Suzawa, T.; Takamura, M.; Takeda, M.; Takeishi, R.; Taketa, A.; Takita, M.; Tameda, Y.; Tanaka, H.; Tanaka, K.; Tanaka, M.; Thomas, S. B.; Thomson, G. B.; Tinyakov, P.; Tkachev, I.; Tokuno, H.; Tomida, T.; Troitsky, S.; Tsunesada, Y.; Tsutsumi, K.; Uchihori, Y.; Udo, S.; Urban, F.; Vasiloff, G.; Wong, T.; Yamane, R.; Yamaoka, H.; Yamazaki, K.; Yang, J.; Yashiro, K.; Yoneda, Y.; Yoshida, S.; Yoshii, H.; Zollinger, R.; Zundel, Z.

2015-05-01

We report on the search for steady point-like sources of neutral particles around 1018 eV between 2008 and 2013 May with the scintillator SD of the Telescope Array experiment. We found overall no significant point-like excess above 0.5 EeV in the northern sky. Subsequently, we also searched for coincidence with the Fermi bright Galactic sources. No significant coincidence was found within the statistical uncertainty. Hence, we set an upper limit on the neutron flux that corresponds to an averaged flux of 0.07 km-2 yr-1 for E\\gt 1 EeV in the northern sky at the 95% confidence level. This is the most stringent flux upper limit in a northern sky survey assuming point-like sources. The upper limit at the 95% confidence level on the neutron flux from Cygnus X-3 is also set to 0.2 km-2 yr-1 for E\\gt 0.5 EeV. This is an order of magnitude lower than previous flux measurements.

NEUTRONIC REACTOR CORE INSTRUMENT

DOEpatents

Mims, L.S.

1961-08-22

A multi-purpose instrument for measuring neutron flux, coolant flow rate, and coolant temperature in a nuclear reactor is described. The device consists essentially of a hollow thimble containing a heat conducting element protruding from the inner wall, the element containing on its innermost end an amount of fissionsble materinl to function as a heat source when subjected to neutron flux irradiation. Thermocouple type temperature sensing means are placed on the heat conducting element adjacent the fissionable material and at a point spaced therefrom, and at a point on the thimble which is in contact with the coolant fluid. The temperature differentials measured between the thermocouples are determinative of the neutron flux, coolant flow, and temperature being measured. The device may be utilized as a probe or may be incorporated in a reactor core. (AE C)

Beyond Californium-A Neutron Generator Alternative for Dosimetry and Instrument Calibration in the U.S.

PubMed

Piper, Roman K; Mozhayev, Andrey V; Murphy, Mark K; Thompson, Alan K

2017-09-01

Evaluations of neutron survey instruments, area monitors, and personal dosimeters rely on reference neutron radiations, which have evolved from the heavy reliance on (α,n) sources to a shared reliance on (α,n) and the spontaneous fission neutrons of californium-252 (Cf). Capable of producing high dose equivalent rates from an almost point source geometry, the characteristics of Cf are generally more favorable when compared to the use of (α,n) and (γ,n) sources or reactor-produced reference neutron radiations. Californium-252 is typically used in two standardized configurations: unmoderated, to yield a fission energy spectrum; or with the capsule placed within a heavy-water moderating sphere to produce a softened spectrum that is generally considered more appropriate for evaluating devices used in nuclear power plant work environments. The U.S. Department of Energy Cf Loan/Lease Program, a longtime origin of affordable Cf sources for research, testing and calibration, was terminated in 2009. Since then, high-activity sources have become increasingly cost-prohibitive for laboratories that formerly benefited from that program. Neutron generators, based on the D-T and D-D fusion reactions, have become economically competitive with Cf and are recognized internationally as important calibration and test standards. Researchers from the National Institute of Standards and Technology and the Pacific Northwest National Laboratory are jointly considering the practicality and technical challenges of implementing neutron generators as calibration standards in the U.S. This article reviews the characteristics of isotope-based neutron sources, possible isotope alternatives to Cf, and the rationale behind the increasing favor of electronically generated neutron options. The evaluation of a D-T system at PNNL has revealed characteristics that must be considered in adapting generators to the task of calibration and testing where accurate determination of a dosimetric quantity is necessary. Finally, concepts are presented for modifying the generated neutron spectra to achieve particular targeted spectra, simulating Cf or workplace environments.

Monte Carlo simulation of moderator and reflector in coal analyzer based on a D-T neutron generator.

PubMed

Shan, Qing; Chu, Shengnan; Jia, Wenbao

2015-11-01

Coal is one of the most popular fuels in the world. The use of coal not only produces carbon dioxide, but also contributes to the environmental pollution by heavy metals. In prompt gamma-ray neutron activation analysis (PGNAA)-based coal analyzer, the characteristic gamma rays of C and O are mainly induced by fast neutrons, whereas thermal neutrons can be used to induce the characteristic gamma rays of H, Si, and heavy metals. Therefore, appropriate thermal and fast neutrons are beneficial in improving the measurement accuracy of heavy metals, and ensure that the measurement accuracy of main elements meets the requirements of the industry. Once the required yield of the deuterium-tritium (d-T) neutron generator is determined, appropriate thermal and fast neutrons can be obtained by optimizing the neutron source term. In this article, the Monte Carlo N-Particle (MCNP) Transport Code and Evaluated Nuclear Data File (ENDF) database are used to optimize the neutron source term in PGNAA-based coal analyzer, including the material and shape of the moderator and neutron reflector. The optimized targets include two points: (1) the ratio of the thermal to fast neutron is 1:1 and (2) the total neutron flux from the optimized neutron source in the sample increases at least 100% when compared with the initial one. The simulation results show that, the total neutron flux in the sample increases 102%, 102%, 85%, 72%, and 62% with Pb, Bi, Nb, W, and Be reflectors, respectively. Maximum optimization of the targets is achieved when the moderator is a 3-cm-thick lead layer coupled with a 3-cm-thick high-density polyethylene (HDPE) layer, and the neutron reflector is a 27-cm-thick hemispherical lead layer. Copyright © 2015 Elsevier Ltd. All rights reserved.

On the Possibility of Creating a Point-Like Neutron Source

NASA Astrophysics Data System (ADS)

Golubev, S. V.; Skalyga, V. A.; Izotov, I. V.; Sidorov, A. V.; Razin, S. V.; Shaposhnikov, R. A.; Lapin, R. L.; Bokhanov, A. F.; Kazakov, M. Yu.

2018-03-01

We consider the possibility of creating a compact high-power neutron generator with a small emitting area (of the order of 100 μm) and a neutron yield of 1010s-1 on the basis of a deuterium-deuterium fusion reaction (or 1012 s-1 on the basis of a deuterium-tritium fusion reaction). The fusion takes place under bombardment of a deuterium- (or tritium-) saturated target by a high-current (about 100 mA) focused deuterium ion beam with an energy of 100 keV. The ion beam with total current at a level of hundreds of milliamperes and small emittance (less than 0.1 π·mm·mrad), which is crucial for sharp focusing, can be generated by a quasi-gas-dynamic ion source of a new generation created on the basis of a discharge in an open magnetic trap sustained by high-power electromagnetic radiation of the millimeter wavelength range under electron cyclotron resonance conditions. Simulations of the focusing system for the experimentally obtained ion beam show the possibility to create a deuterium ion beam with a transverse size of 200 μm on the neutron-forming target. Prospects for using such a neutron source for neutron tomography are discussed.

A Search for Point Sources of EeV Neutrons

NASA Astrophysics Data System (ADS)

Pierre Auger Collaboration; Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; 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.; Antiči'c, T.; Aramo, C.; Arganda, E.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Balzer, M.; Barber, K. B.; Barbosa, A. F.; Bardenet, R.; Barroso, S. L. C.; Baughman, B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellétoile, A.; Bellido, J. A.; BenZvi, S.; 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.; Bruijn, R.; Buchholz, P.; Bueno, A.; Buroker, L.; Burton, R. E.; Caballero-Mora, K. S.; Caccianiga, B.; Caramete, L.; Caruso, R.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chirinos Diaz, J.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cook, H.; Cooper, M. J.; Coppens, J.; Cordier, A.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; De Donato, C.; de Jong, S. J.; De La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; de Vries, K. D.; del Peral, L.; del Río, M.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Díaz Castro, M. L.; Diep, P. N.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; Ebr, J.; Engel, R.; Erdmann, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fliescher, S.; Fracchiolla, C. E.; Fraenkel, E. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Gaior, R.; Gamarra, R. F.; Gambetta, S.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Gascon Bravo, A.; Gemmeke, H.; Ghia, P. L.; Giller, M.; Gitto, J.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; Gookin, B.; Gorgi, A.; Gouffon, P.; Grashorn, E.; Grebe, S.; Griffith, N.; Grigat, M.; Grillo, A. F.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Herve, A. E.; Hojvat, C.; Hollon, N.; Holmes, V. C.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Ionita, F.; Italiano, A.; Jansen, S.; Jarne, C.; Jiraskova, S.; Josebachuili, M.; Kadija, K.; Kampert, K. H.; Karhan, P.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kelley, J. L.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapp, J.; Koang, D.-H.; Kotera, K.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kulbartz, J. K.; Kunka, N.; La Rosa, G.; Lachaud, C.; LaHurd, D.; Latronico, L.; Lauer, R.; 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.; Macolino, C.; Maldera, S.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, J.; Marin, V.; Maris, I. C.; Marquez Falcon, H. R.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mazur, P. O.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Mertsch, P.; Meurer, C.; Meyhandan, R.; Mi'canovi'c, S.; Micheletti, M. I.; Minaya, I. A.; Miramonti, L.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Moreno, J. C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Nhung, P. T.; Niechciol, M.; Niemietz, L.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nožka, L.; Oehlschläger, J.; Olinto, A.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Parente, G.; Parizot, E.; Parra, A.; Pastor, S.; Paul, T.; Pech, M.; Peķala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Petrera, S.; Petrolini, A.; Petrov, Y.; Pfendner, C.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Ponce, V. H.; Pontz, M.; Porcelli, A.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rivera, H.; Rizi, V.; Roberts, J.; Rodrigues de Carvalho, W.; Rodriguez, G.; Rodriguez Cabo, I.; Rodriguez Martino, J.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Rouillé-d'Orfeuil, B.; Roulet, E.; Rovero, A. C.; Rühle, C.; Saftoiu, A.; Salamida, F.; Salazar, H.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarkar, S.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Scholten, O.; Schoorlemmer, H.; Schovancova, J.; Schovánek, P.; Schröder, F.; Schulte, S.; Schuster, D.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Silva Lopez, H. H.; Sima, O.; 'Smiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Srivastava, Y. N.; Stanic, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Šuša, T.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Tapia, A.; Tartare, M.; Taşcău, O.; Tcaciuc, R.; Thao, N. T.; Thomas, D.; Tiffenberg, J.; Timmermans, C.; Tkaczyk, W.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Travnicek, P.; Tridapalli, D. B.; Tristram, G.; 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 Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Wahlberg, H.; Wahrlich, P.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Westerhoff, S.; Whelan, B. J.; Widom, A.; Wieczorek, G.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Wommer, M.; Wundheiler, B.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano Garcia, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.

2012-12-01

A thorough search of the sky exposed at the Pierre Auger Cosmic Ray Observatory reveals no statistically significant excess of events in any small solid angle that would be indicative of a flux of neutral particles from a discrete source. The search covers from -90° to +15° in declination using four different energy ranges above 1 EeV (1018 eV). The method used in this search is more sensitive to neutrons than to photons. The upper limit on a neutron flux is derived for a dense grid of directions for each of the four energy ranges. These results constrain scenarios for the production of ultrahigh energy cosmic rays in the Galaxy.

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

Oak Ridge Spallation Neutron Source (ORSNS) target station design integration

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

McManamy, T.; Booth, R.; Cleaves, J.

1996-06-01

The conceptual design for a 1- to 3-MW short pulse spallation source with a liquid mercury target has been started recently. The design tools and methods being developed to define requirements, integrate the work, and provide early cost guidance will be presented with a summary of the current target station design status. The initial design point was selected with performance and cost estimate projections by a systems code. This code was developed recently using cost estimates from the Brookhaven Pulsed Spallation Neutron Source study and experience from the Advanced Neutron Source Project`s conceptual design. It will be updated and improvedmore » as the design develops. Performance was characterized by a simplified figure of merit based on a ratio of neutron production to costs. A work breakdown structure was developed, with simplified systems diagrams used to define interfaces and system responsibilities. A risk assessment method was used to identify potential problems, to identify required research and development (R&D), and to aid contingency development. Preliminary 3-D models of the target station are being used to develop remote maintenance concepts and to estimate costs.« less

Benchmarking shielding simulations for an accelerator-driven spallation neutron source

DOE PAGES

Cherkashyna, Nataliia; Di Julio, Douglas D.; Panzner, Tobias; ...

2015-08-09

The shielding at an accelerator-driven spallation neutron facility plays a critical role in the performance of the neutron scattering instruments, the overall safety, and the total cost of the facility. Accurate simulation of shielding components is thus key for the design of upcoming facilities, such as the European Spallation Source (ESS), currently in construction in Lund, Sweden. In this paper, we present a comparative study between the measured and the simulated neutron background at the Swiss Spallation Neutron Source (SINQ), at the Paul Scherrer Institute (PSI), Villigen, Switzerland. The measurements were carried out at several positions along the SINQ monolithmore » wall with the neutron dosimeter WENDI-2, which has a well-characterized response up to 5 GeV. The simulations were performed using the Monte-Carlo radiation transport code Geant4, and include a complete transport from the proton beam to the measurement locations in a single calculation. An agreement between measurements and simulations is about a factor of 2 for the points where the measured radiation dose is above the background level, which is a satisfactory result for such simulations spanning many energy regimes, different physics processes and transport through several meters of shielding materials. The neutrons contributing to the radiation field emanating from the monolith were confirmed to originate from neutrons with energies above 1 MeV in the target region. The current work validates Geant4 as being well suited for deep-shielding calculations at accelerator-based spallation sources. We also extrapolate what the simulated flux levels might imply for short (several tens of meters) instruments at ESS.« less

Neutron Science TeraGrid Gateway

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

Lynch, Vickie E; Chen, Meili; Cobb, John W

The unique contributions of the Neutron Science TeraGrid Gateway (NSTG) are the connection of national user facility instrument data sources to the integrated cyberinfrastructure of the National Science FoundationTeraGrid and the development of a neutron science gateway that allows neutron scientists to use TeraGrid resources to analyze their data, including comparison of experiment with simulation. The NSTG is working in close collaboration with the Spallation Neutron Source (SNS) at Oak Ridge as their principal facility partner. The SNS is a next-generation neutron source. It has completed construction at a cost of $1.4 billion and is ramping up operations. The SNSmore » will provide an order of magnitude greater flux than any previous facility in the world and will be available to all of the nation's scientists, independent of funding source, on a peer-reviewed merit basis. With this new capability, the neutron science community is facing orders of magnitude larger data sets and is at a critical point for data analysis and simulation. There is a recognized need for new ways to manage and analyze data to optimize both beam time and scientific output. The TeraGrid is providing new capabilities in the gateway for simulations using McStas and a fitting service on distributed TeraGrid resources to improved turnaround. NSTG staff are also exploring replicating experimental data in archival storage. As part of the SNS partnership, the NSTG provides access to gateway support, cyberinfrastructure outreach, community development, and user support for the neutron science community. This community includes not only SNS staff and users but extends to all the major worldwide neutron scattering centers.« less

Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons

PubMed Central

Achyuthan, Komandoor E.; Allen, Matthew; Denton, Michele L. B.; Siegal, Michael P.; Manginell, Ronald P.

2017-01-01

Abstract Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here the microfabrication of gadolinium (Gd) conversion material–based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation–induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-doped aluminum cap layer atop Gd. The resultant coatings were stable for at least 6 years, demonstrating excellent stability and product shelf-life. Depositing Gd directly on the diode surface eliminated the air gap, leading to a 200-fold increase in electron capture efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICEs with energies of 72, 132 and 174 keV. Results are reported for neutron reflection and moderation by polyethylene for enhanced sensitivity, and γ- and X-ray elimination for improved specificity. The optimal Gd thickness was 10.4 μm for a 300 μm-thick partially depleted diode of 300 mm2 active surface area. Fast detection (within 10 min) at a neutron source-to-diode distance of 11.7 cm was achieved with this configuration. All ICE energies along with γ-ray and Kα,β X-rays were modeled to emphasize correlations between experiment and theory. Semi-conductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources. PMID:28369631

Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons

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

Pfeifer, Kent B.; Achyuthan, Komandoor E.; Allen, Matthew

Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here in this study, the microfabrication of gadolinium (Gd) conversion material–based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation–induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-dopedmore » aluminum cap layer atop Gd. The resultant coatings were stable for at least 6 years, demonstrating excellent stability and product shelf-life. Depositing Gd directly on the diode surface eliminated the air gap, leading to a 200-fold increase in electron capture efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICEs with energies of 72, 132 and 174 keV. Results are reported for neutron reflection and moderation by polyethylene for enhanced sensitivity, and γ- and X-ray elimination for improved specificity. The optimal Gd thickness was 10.4 μm for a 300 μm-thick partially depleted diode of 300 mm 2 active surface area. Fast detection (within 10 min) at a neutron source-to-diode distance of 11.7 cm was achieved with this configuration. All ICE energies along with γ-ray and K α,β X-rays were modeled to emphasize correlations between experiment and theory. Semi-conductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources.« less

Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons

DOE PAGES

Pfeifer, Kent B.; Achyuthan, Komandoor E.; Allen, Matthew; ...

2017-03-25

Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here in this study, the microfabrication of gadolinium (Gd) conversion material–based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation–induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-dopedmore » aluminum cap layer atop Gd. The resultant coatings were stable for at least 6 years, demonstrating excellent stability and product shelf-life. Depositing Gd directly on the diode surface eliminated the air gap, leading to a 200-fold increase in electron capture efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICEs with energies of 72, 132 and 174 keV. Results are reported for neutron reflection and moderation by polyethylene for enhanced sensitivity, and γ- and X-ray elimination for improved specificity. The optimal Gd thickness was 10.4 μm for a 300 μm-thick partially depleted diode of 300 mm 2 active surface area. Fast detection (within 10 min) at a neutron source-to-diode distance of 11.7 cm was achieved with this configuration. All ICE energies along with γ-ray and K α,β X-rays were modeled to emphasize correlations between experiment and theory. Semi-conductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources.« less

SU-E-T-21: A D-D Based Neutron Generator System for Boron Neutron Capture Therapy: A Feasibility Study

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

Hsieh, M; Liu, Y; Nie, L

2015-06-15

Purpose: To investigate the feasibility of a deuterium-deuterium (DD) neutron generator for application in boron neutron capture therapy (BNCT) of brain cancer Methods: MCNP simulations were performed using a head phantom and a monoenergetic neutron source, which resembles the point source in a DD generator that emits 2.45-MeV neutrons. Source energies ranging from 5eV to 2.45MeV were simulated to determine the optimal treatment energy. The phantom consisted of soft tissue, brain tissue, skull, skin layer, and a brain tumor of 5 cm in diameter. Tumor depth was varied from 5–10 cm. Boron-10 concentrations of 10 ppm, 15 ppm, and 30more » ppm were used in the soft/brain tissues, skin, and tumor, respectively. The neutron flux required to deliver 60 Gy to the tumor as well as the normal tissue doses were determined. Results: Beam energies between 5eV and 10keV obtained doses with the highest dose ratios (3.3–25.9) between the tumor and the brain at various depths. The dose ratio with 2.45-MeV neutrons ranged from 0.8–6.6. To achieve the desired tumor dose in 40 minutes, the required neutron flux for a DD generator was between 8.8E10 and 5.2E11 n/s and the resulting brain dose was between 2.3 and 18 Gy, depending on the tumor depth. The skin and soft tissue doses were within acceptable tolerances. The boron-neutron interaction accounted for 54–58% of the total dose. Conclusion: This study shows that the DD neutron generator can be a feasible neutron source for BNCT. The required neutron flux for treatment is achievable with the current DD neutron technology. With a well-designed beam shaping assembly and treatment geometry, the neutron flux can be further improved and a 60-Gy prescription can be accurately delivered to the target while maintaining tolerable normal tissue doses. Further experimental studies will be developed and conducted to validate the simulation results.« less

Method for measuring multiple scattering corrections between liquid scintillators

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

Verbeke, J. M.; Glenn, A. M.; Keefer, G. J.

2016-04-11

In this study, a time-of-flight method is proposed to experimentally quantify the fractions of neutrons scattering between scintillators. An array of scintillators is characterized in terms of crosstalk with this method by measuring a californium source, for different neutron energy thresholds. The spectral information recorded by the scintillators can be used to estimate the fractions of neutrons multiple scattering. With the help of a correction to Feynman's point model theory to account for multiple scattering, these fractions can in turn improve the mass reconstruction of fissile materials under investigation.

Gamma-ray burst theory: Back to the drawing board

NASA Technical Reports Server (NTRS)

Harding, Alice K.

1994-01-01

Gamma-ray bursts have always been intriguing sources to study in terms of particle acceleration, but not since their discovery two decades ago has the theory of these objects been in such turmoil. Prior to the launch of Compton Gamma-Ray Observatory and observations by Burst and Transient Source Experiment (BATSE), there was strong evidence pointing to magnetized Galactic neutron stars as the sources of gamma-ray bursts. However, since BATSE the observational picture has changed dramatically, requiring much more distant and possibly cosmological sources. I review the history of gamma-ray burst theory from the era of growing consensus for nearby neutron stars to the recent explosion of halo and cosmological models and the impact of the present confusion on the particle acceleration problem.

Assessment of Laser-Driven Pulsed Neutron Sources for Poolside Neutron-based Advanced NDE – A Pathway to LANSCE-like Characterization at INL

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

Roth, Markus; Vogel, Sven C.; Bourke, Mark Andrew M.

A variety of opportunities for characterization of fresh nuclear fuels using thermal (~25meV) and epithermal (~10eV) neutrons have been documented at Los Alamos National Laboratory. They include spatially resolved non-destructive characterization of features, isotopic enrichment, chemical heterogeneity and stoichiometry. The LANSCE spallation neutron source is well suited in neutron fluence and temporal characteristics for studies of fuels. However, recent advances in high power short pulse lasers suggest that compact neutron sources might, over the next decade, become viable at a price point that would permit their consideration for poolside characterization on site at irradiation facilities. In a laser-driven neutron sourcemore » the laser is used to accelerate deuterium ions into a beryllium target where neutrons are produced. At this time, the technology is new and their total neutron production is approximately four orders of magnitude less than a facility like LANSCE. However, recent measurements on a sub-optimized system demonstrated >10 10 neutrons in sub-nanosecond pulses in predominantly forward direction. The compactness of the target system compared to a spallation target may allow exchanging the target during a measurement to e.g. characterize a highly radioactive sample with thermal, epithermal, and fast neutrons as well as hard X-rays, thus avoiding sample handling. At this time several groups are working on laser-driven neutron production and are advancing concepts for lasers, laser targets, and optimized neutron target/moderator systems. Advances in performance sufficient to enable poolside fuels characterization with LANSCE-like fluence on sample within a decade may be possible. This report describes the underlying physics and state-of-the-art of the laser-driven neutron production process from the perspective of the DOE/NE mission. It also discusses the development and understanding that will be necessary to provide customized capability for characterization of irradiated fuels. Potential operational advantages compared to a spallation neutron source include reduced shielding complexity, reduced energy requirements, and a production target free of fission products. Contributors to this report include experts in laser-driven neutron production (Roth, Fernandez), laser design (Haefner, Siders, Leemans), laser target design (Glenzer), spallation target/moderator design (Mocko), neutron instrumentation and characterization applications (Vogel, Bourke).« less

A possible explanation of the parallel tracks in kilohertz quasi-periodic oscillations from low-mass-X-ray binaries

NASA Astrophysics Data System (ADS)

Shi, Chang-Sheng; Zhang, Shuang-Nan; Li, Xiang-Dong

2018-05-01

We recalculate the modes of the magnetohydrodynamics (MHD) waves in the MHD model (Shi, Zhang & Li 2014) of the kilohertz quasi-periodic oscillations (kHz QPOs) in neutron star low mass X-ray binaries (NS-LMXBs), in which the compressed magnetosphere is considered. A method on point-by-point scanning for every parameter of a normal LMXBs is proposed to determine the wave number in a NS-LMXB. Then dependence of the twin kHz QPO frequencies on accretion rates (\\dot{M}) is obtained with the wave number and magnetic field (B*) determined by our method. Based on the MHD model, a new explanation of the parallel tracks, i.e. the slowly varying effective magnetic field leads to the shift of parallel tracks in a source, is presented. In this study, we obtain a simple power-law relation between the kHz QPO frequencies and \\dot{M}/B_{\\ast }^2 in those sources. Finally, we study the dependence of kHz quasi-periodic oscillation frequencies on the spin, mass and radius of a neutron star. We find that the effective magnetic field, the spin, mass and radius of a neutron star lead to the parallel tracks in different sources.

How to improve the irradiation conditions for the International Fusion Materials Irradiation Facility

NASA Astrophysics Data System (ADS)

Daum, Eric

2000-12-01

The accelerator-based intense D-Li neutron source International Fusion Materials Irradiation Facility (IFMIF) provides very suitable irradiation conditions for fusion materials development with the attractive option of accelerated irradiations. Investigations show that a neutron moderator made of tungsten and placed in the IFMIF test cell can further improve the irradiation conditions. The moderator softens the IFMIF neutron spectrum by enhancing the fraction of low energy neutrons. For displacement damage, the ratio of point defects to cascades is more DEMO relevant and for tritium production in Li-based breeding ceramic materials it leads to a preferred production via the 6Li(n,t) 4He channel as it occurs in a DEMO breeding blanket.

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.

The LBM program at the EPFL/LOTUS Facility

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

File, J.; Jassby, D.L.; Tsang, F.Y.

1986-11-01

An experimental program of neutron transport studies of the Lithium Blanket Module (LBM) is being carried out with the LOTUS point-neutron source facility at Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland. Preliminary experiments use passive neutron dosimetry within the fuel rods in the LBM central zone, as well as, both thermal extraction and dissolution methods to assay tritium bred in Li/sub 2/O diagnostic wafers and LBM pellets. These measurements are being compared and reconciled with each other and with the predictions of two-dimensional discrete-ordinates and continuous-energy Monte-Carlo analyses of the Lotus/LBM system.

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

Active Detection of Shielded Special Nuclear Material in the Presence of Variable High Backgrounds Using a Mixed Photon-Neutron Source

NASA Astrophysics Data System (ADS)

Martin, Philip N.; Clemett, Ceri D.; Hill, Cassie; O'Malley, John; Campbell, Ben

This paper describes and compares two approaches to the analysis of active interrogation data containing high photon backgrounds associated with mixed photon-neutron source flash active interrogation. Results from liquid scintillation detectors (EJ301/EJ309) fielded at the Naval Research Laboratory (NRL), in collaboration with the Atomic Weapons Establishment (AWE), using the NRL Mercury Inductive Voltage Adder (IVA) operating in both a photon and mixed photon-neutron mode at a Depleted Uranium (DU) target are presented. The standard approach applying a Figure of Merit (FOM) consisting of background sigma above background is compared with an approach looking to fit only the time-decaying photon signal with standard delayed photon emission from ∼10-MeV end-point-energy Bremsstrahlung photofission of DU. Examples where each approach does well and less well are presented together with a discussion of the relative limitations of both approaches to the type of mixed photon-neutron flash active interrogation being considered.

Shielding analyses of an AB-BNCT facility using Monte Carlo simulations and simplified methods

NASA Astrophysics Data System (ADS)

Lai, Bo-Lun; Sheu, Rong-Jiun

2017-09-01

Accurate Monte Carlo simulations and simplified methods were used to investigate the shielding requirements of a hypothetical accelerator-based boron neutron capture therapy (AB-BNCT) facility that included an accelerator room and a patient treatment room. The epithermal neutron beam for BNCT purpose was generated by coupling a neutron production target with a specially designed beam shaping assembly (BSA), which was embedded in the partition wall between the two rooms. Neutrons were produced from a beryllium target bombarded by 1-mA 30-MeV protons. The MCNP6-generated surface sources around all the exterior surfaces of the BSA were established to facilitate repeated Monte Carlo shielding calculations. In addition, three simplified models based on a point-source line-of-sight approximation were developed and their predictions were compared with the reference Monte Carlo results. The comparison determined which model resulted in better dose estimation, forming the basis of future design activities for the first ABBNCT facility in Taiwan.

Hundred joules plasma focus device as a potential pulsed source for in vitro cancer cell irradiation

NASA Astrophysics Data System (ADS)

Jain, J.; Moreno, J.; Andaur, R.; Armisen, R.; Morales, D.; Marcelain, K.; Avaria, G.; Bora, B.; Davis, S.; Pavez, C.; Soto, L.

2017-08-01

Plasma focus devices may arise as useful source to perform experiments aimed to study the effects of pulsed radiation on human cells in vitro. In the present work, a table top hundred joules plasma focus device, namely "PF-400J", was adapted to irradiate colorectal cancer cell line, DLD-1. For pulsed x-rays, the doses (energy absorbed per unit mass, measured in Gy) were measured using thermoluminescence detectors (TLD-100 dosimeters). The neutron fluence and the average energy were used to estimate the pulsed neutron doses. Fifty pulses of x-rays (0.12 Gy) and fifty pulses of neutrons (3.5 μGy) were used to irradiate the cancer cells. Irradiation-induced DNA damage and cell death were assessed at different time points after irradiation. Cell death was observed using pulsed neutron irradiation, at ultralow doses. Our results indicate that the PF-400J can be used for in vitro assessment of the effect of pulsed radiation in cancer cell research.

Interpretation of small-angle diffraction experiments on opal-like photonic crystals

NASA Astrophysics Data System (ADS)

Marlow, F.; Muldarisnur, M.; Sharifi, P.; Zabel, H.

2011-08-01

Comprehensive structural information on artificial opals involving the deviations from the strongly dominating face-centered cubic structure is still missing. Recent structure investigations with neutrons and synchrotron sources have shown a high degree of order but also a number of unexpected scattering features. Here, we point out that the exclusion of the allowed 002-type diffraction peaks by a small atomic form factor is not obvious and that surface scattering has to be included as a possible source for the diffraction peaks. Our neutron diffraction data indicate that surface scattering is the main reason for the smallest-angle peaks in the diffraction patterns.

Characteristics of a heavy water photoneutron source in boron neutron capture therapy

NASA Astrophysics Data System (ADS)

Danial, Salehi; Dariush, Sardari; M. Salehi, Jozani

2013-07-01

Bremsstrahlung photon beams produced by medical linear accelerators are currently the most commonly used method of radiation therapy for cancerous tumors. Photons with energies greater than 8-10 MeV potentially generate neutrons through photonuclear interactions in the accelerator's treatment head, patient's body, and treatment room ambient. Electrons impinging on a heavy target generate a cascade shower of bremsstrahlung photons, the energy spectrum of which shows an end point equal to the electron beam energy. By varying the target thickness, an optimum thickness exists for which, at the given electron energy, maximum photon flux is achievable. If a source of high-energy photons i.e. bremsstrahlung, is conveniently directed to a suitable D2O target, a novel approach for production of an acceptable flux of filterable photoneturons for boron neutron capture therapy (BNCT) application is possible. This study consists of two parts. 1. Comparison and assessment of deuterium photonuclear cross section data. 2. Evaluation of the heavy water photonuclear source.

Detectors Requirements for the ODIN Beamline at ESS

NASA Astrophysics Data System (ADS)

Morgano, Manuel; Lehmann, Eberhard; Strobl, Markus

The upcoming high intensity pulsed spallationneutron source ESS, now in construction in Sweden, will provide unprecedented opportunities for neutron science worldwide. In particular, neutron imaging will benefit from the time structure of the source and its high brilliance. These features will unlock new opportunities at the imaging beamline ODIN, but only if suitable detectors are employed and, in some cases, upgraded. In this paper, we highlight the current state-of-the-art for neutron imaging detectors, pointing out that, while no single presently existing detector can fulfill all the requirements currently needed to exploit the source to its limits, the wide range of applications of ODIN can be successfully covered by a suite of current state-of-the-art detectors. Furthermore we speculate on improvements to the current detector technologies that would expand the range of the existing detectors and application range and we outline a strategy to have the best possible combined system for the foreseen day 1 operations of ODIN in 2019.

Scintillation detector efficiencies for neutrons in the energy region above 20 MeV

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

Dickens, J.K.

1991-01-01

The computer program SCINFUL (for SCINtillator FUL1 response) is a program designed to provide a calculated complete pulse-height response anticipated for neutrons being detected by either an NE-213 (liquid) scintillator or an NE-110 (solid) scintillator in the shape of a right circular cylinder. The point neutron source may be placed at any location with respect to the detector, even inside of it. The neutron source may be monoenergetic, or Maxwellian distributed, or distributed between chosen lower and upper bounds. The calculational method uses Monte Carlo techniques, and it is relativistically correct. Extensive comparisons with a variety of experimental data havemore » been made. There is generally overall good agreement (less than 10% differences) of results for SCINFUL calculations with measured integral detector efficiencies for the design incident neutron energy range of 0.1 to 80 MeV. Calculations of differential detector responses, i.e. yield versus response pulse height, are generally within about 5% on the average for incident neutron energies between 16 and 50 MeV and for the upper 70% of the response pulse height. For incident neutron energies between 50 and 80 MeV, the calculated shape of the response agrees with measurements, but the calculations tend to underpredict the absolute values of the measured responses. Extension of the program to compute responses for incident neutron energies greater than 80 MeV will require new experimental data on neutron interactions with carbon. 32 refs., 6 figs., 2 tabs.« less

Scintillation detector efficiencies for neutrons in the energy region above 20 MeV

NASA Astrophysics Data System (ADS)

Dickens, J. K.

The computer program SCINFUL (for SCINtillator FUL1 response) is a program designed to provide a calculated complete pulse-height response anticipated for neutrons being detected by either an NE-213 (liquid) scintillator or an NE-110 (solid) scintillator in the shape of a right circular cylinder. The point neutron source may be placed at any location with respect to the detector, even inside of it. The neutron source may be monoenergetic, or Maxwellian distributed, or distributed between chosen lower and upper bounds. The calculational method uses Monte Carlo techniques, and it is relativistically correct. Extensive comparisons with a variety of experimental data were made. There is generally overall good agreement (less than 10 pct. differences) of results for SCINFUL calculations with measured integral detector efficiencies for the design incident neutron energy range of 0.1 to 80 MeV. Calculations of differential detector responses, i.e., yield versus response pulse height, are generally within about 5 pct. on the average for incident neutron energies between 16 and 50 MeV and for the upper 70 pct. of the response pulse height. For incident neutron energies between 50 and 80 MeV, the calculated shape of the response agrees with measurements, but the calculations tend to underpredict the absolute values of the measured responses. Extension of the program to compute responses for incident neutron energies greater than 80 MeV will require new experimental data on neutron interactions with carbon.

Spallation neutron production and the current intra-nuclear cascade and transport codes

NASA Astrophysics Data System (ADS)

Filges, D.; Goldenbaum, F.; Enke, M.; Galin, J.; Herbach, C.-M.; Hilscher, D.; Jahnke, U.; Letourneau, A.; Lott, B.; Neef, R.-D.; Nünighoff, K.; Paul, N.; Péghaire, A.; Pienkowski, L.; Schaal, H.; Schröder, U.; Sterzenbach, G.; Tietze, A.; Tishchenko, V.; Toke, J.; Wohlmuther, M.

A recent renascent interest in energetic proton-induced production of neutrons originates largely from the inception of projects for target stations of intense spallation neutron sources, like the planned European Spallation Source (ESS), accelerator-driven nuclear reactors, nuclear waste transmutation, and also from the application for radioactive beams. In the framework of such a neutron production, of major importance is the search for ways for the most efficient conversion of the primary beam energy into neutron production. Although the issue has been quite successfully addressed experimentally by varying the incident proton energy for various target materials and by covering a huge collection of different target geometries --providing an exhaustive matrix of benchmark data-- the ultimate challenge is to increase the predictive power of transport codes currently on the market. To scrutinize these codes, calculations of reaction cross-sections, hadronic interaction lengths, average neutron multiplicities, neutron multiplicity and energy distributions, and the development of hadronic showers are confronted with recent experimental data of the NESSI collaboration. Program packages like HERMES, LCS or MCNPX master the prevision of reaction cross-sections, hadronic interaction lengths, averaged neutron multiplicities and neutron multiplicity distributions in thick and thin targets for a wide spectrum of incident proton energies, geometrical shapes and materials of the target generally within less than 10% deviation, while production cross-section measurements for light charged particles on thin targets point out that appreciable distinctions exist within these models.

Synchrotron VUV-UV and positron lifetime spectroscopy study of vacancy-type defects in reactor neutron-irradiated MgO.nAl2O3 (n = 2)

NASA Astrophysics Data System (ADS)

Rahman, Abu Zayed Mohammad Saliqur; Cao, Xingzhong; Wang, Baoyi; Evslin, Jarah; Xu, Qiu; Atobe, Kozo

2016-12-01

We investigated neutron-irradiation-induced point defects in spinel single crystals using a synchrotron VUV-UV source and positron lifetime spectroscopy. Photoexcitation (PE) spectra near 230 nm and their corresponding photoluminescence (PL) spectra at 475 nm were attributed to F-centers. With increasing irradiation temperature and fluence, PE efficiency and PL intensity decreased dramatically. Positron lifetimes (PLT) of neutron-irradiated and non-irradiated samples were measured to identify the cation vacancies. A PLT measurement of 250 ps was obtained in a neutron-irradiated (20 K) sample which is tentatively attributed to an aluminum monovacancy. Decreasing PLT with higher irradiation indicates the formation of oxygen-vacancy complex centers.

Mathematical Investigation of Gamma Ray and Neutron Absorption Grid Patterns for Homeland Defense Related Fourier Imaging Systems

NASA Technical Reports Server (NTRS)

Boccio, Dona

2003-01-01

Terrorist suitcase nuclear devices typically using converted Soviet tactical nuclear warheads contain several kilograms of plutonium. This quantity of plutonium emits a significant number of gamma rays and neutrons as it undergoes radioactive decay. These gamma rays and neutrons normally penetrate ordinary matter to a significant distance. Unfortunately this penetrating quality of the radiation makes imaging with classical optics impractical. However, this radiation signature emitted by the nuclear source may be sufficient to be imaged from low-flying aerial platforms carrying Fourier imaging systems. The Fourier imaging system uses a pair of co-aligned absorption grids to measure a selected range of spatial frequencies from an object. These grids typically measure the spatial frequency in only one direction at a time. A grid pair that looks in all directions simultaneously would be an improvement over existing technology. A number of grid pairs governed by various parameters were investigated to solve this problem. By examining numerous configurations, it became apparent that an appropriate spiral pattern could be made to work. A set of equations was found to describe a grid pattern that produces straight fringes. Straight fringes represent a Fourier transform of a point source at infinity. An inverse Fourier transform of this fringe pattern would provide an accurate image (location and intensity) of a point source.

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)

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.

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.

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. )

Background-Source Cosmic-Photon Elevation Scaling and Cosmic-Neutron/Photon Date Scaling in MCNP6

NASA Astrophysics Data System (ADS)

Tutt, J.; Anderson, C.; McKinney, G.

Cosmic neutron and photon fluxes are known to scale exponentially with elevation. Consequently, cosmic neutron elevation scaling was implemented for use with the background-source option shortly after its introduction into MCNP6, whereby the neutron flux weight factor was adjusted by the elevation scaling factor when the user-specified elevation differed from the selected background.dat grid-point elevation. At the same time, an elevation scaling factor was suggested for the cosmic photon flux, however, cosmic photon elevation scaling is complicated by the fact that the photon background consists of two components: cosmic and terrestrial. Previous versions of the background.dat file did not provide any way to separate these components. With Rel. 4 of this file in 2015, two new columns were added that provide the energy grid and differential cosmic photon flux separately from the total photon flux. Here we show that the cosmic photon flux component can now be scaled independently and combined with the terrestrial component to form the total photon flux at a user-specified elevation in MCNP6. Cosmic background fluxes also scale with the solar cycle due to solar modulation. This modulation has been shown to be nearly sinusoidal over time, with an inverse effect - increased modulation leads to a decrease in cosmic fluxes. This effect was initially included with the cosmic source option in MCNP6 and has now been extended for use with the background source option when: (1) the date is specified in the background.dat file, and (2) when the user specifies a date on the source definition card. A description of the cosmic-neutron/photon date scaling feature will be presented along with scaling results for past and future date extrapolations.

RADIOISOTOPES USED IN PHARMACY. 5. IONIZING RADIATION IN PHARMACEUTICAL ANALYSIS (in Danish)

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

Kristensen, K.

1962-09-01

The use of radioisotope methods for analyzing drugs is reviewed. It is pointed out that heretofore most methods have been based on isotope dilution principles whereas in the future radioactivation analysis, especially with neutron sources, offers great possibilities. (BBB)

Background-Source Cosmic-Photon Elevation Scaling and Cosmic-Neutron/Photon Date Scaling in MCNP6

DOE PAGES

Tutt, James Robert; Anderson, Casey Alan; McKinney, Gregg Walter

2017-10-26

Here, cosmic neutron and photon fluxes are known to scale exponentially with elevation. Consequently, cosmic neutron elevation scaling was implemented for use with the background-source option shortly after its introduction into MCNP6, whereby the neutron flux weight factor was adjusted by the elevation scaling factor when the user-specified elevation differed from the selected background.dat grid-point elevation. At the same time, an elevation scaling factor was suggested for the cosmic photon flux, however, cosmic photon elevation scaling is complicated by the fact that the photon background consists of two components: cosmic and terrestrial. Previous versions of the background.dat file did notmore » provide any way to separate these components. With Rel. 4 of this file in 2015, two new columns were added that provide the energy grid and differential cosmic photon flux separately from the total photon flux. Here we show that the cosmic photon flux component can now be scaled independently and combined with the terrestrial component to form the total photon flux at a user-specified elevation in MCNP6.« less

Background-Source Cosmic-Photon Elevation Scaling and Cosmic-Neutron/Photon Date Scaling in MCNP6

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

Tutt, James Robert; Anderson, Casey Alan; McKinney, Gregg Walter

Here, cosmic neutron and photon fluxes are known to scale exponentially with elevation. Consequently, cosmic neutron elevation scaling was implemented for use with the background-source option shortly after its introduction into MCNP6, whereby the neutron flux weight factor was adjusted by the elevation scaling factor when the user-specified elevation differed from the selected background.dat grid-point elevation. At the same time, an elevation scaling factor was suggested for the cosmic photon flux, however, cosmic photon elevation scaling is complicated by the fact that the photon background consists of two components: cosmic and terrestrial. Previous versions of the background.dat file did notmore » provide any way to separate these components. With Rel. 4 of this file in 2015, two new columns were added that provide the energy grid and differential cosmic photon flux separately from the total photon flux. Here we show that the cosmic photon flux component can now be scaled independently and combined with the terrestrial component to form the total photon flux at a user-specified elevation in MCNP6.« less

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.

FASTER 3: A generalized-geometry Monte Carlo computer program for the transport of neutrons and gamma rays. Volume 1: Summary report

NASA Technical Reports Server (NTRS)

Jordan, T. M.

1970-01-01

The theory used in FASTER-III, a Monte Carlo computer program for the transport of neutrons and gamma rays in complex geometries, is outlined. The program includes the treatment of geometric regions bounded by quadratic and quadric surfaces with multiple radiation sources which have specified space, angle, and energy dependence. The program calculates, using importance sampling, the resulting number and energy fluxes at specified point, surface, and volume detectors. It can also calculate minimum weight shield configuration meeting a specified dose rate constraint. Results are presented for sample problems involving primary neutron, and primary and secondary photon, transport in a spherical reactor shield configuration.

Sci-Sat AM: Brachy - 04: Neutron production around a radiation therapy linac bunker - monte carlo simulations and physical measurements.

PubMed

Khatchadourian, R; Davis, S; Evans, M; Licea, A; Seuntjens, J; Kildea, J

2012-07-01

Photoneutrons are a major component of the equivalent dose in the maze and near the door of linac bunkers. Physical measurements and Monte Carlo (MC) calculations of neutron dose are key for validating bunker design with respect to health regulations. We attempted to use bubble detectors and a 3 He neutron spectrometer to measure neutron equivalent dose and neutron spectra in the maze and near the door of one of our bunkers. We also ran MC simulations with MCNP5 to measure the neutron fluence in the same region. Using a point source of neutrons, a Clinac 1800 linac operating at 10 MV was simulated and the fluence measured at various locations of interest. We describe the challenges faced when measuring dose with bubble detectors in the maze and the complexity of photoneutron spectrometry with linacs operating in pulsed mode. Finally, we report on the development of a userfriendly GUI for shielding calculations based on the NCRP 151 formalism. © 2012 American Association of Physicists in Medicine.

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.

Evidence for a Broad Relativistic Iron Line from the Neutron Star LMXB Ser X-1

NASA Technical Reports Server (NTRS)

Bhattacharyya, Sudip; Strohmayer, Tod E.

2007-01-01

We report on an analysis of XMM-Newton data from the neutron star low mass X-ray binary (LMXB) Serpens X-1 (Ser X-1). Spectral analysis of EPIC PN data indicates that the previously known broad iron Ka emission line in this source has a significantly skewed structure with a moderately extended red wing. The asymmetric shape of the line is well described with the laor and diskline models in XSPEC, which strongly supports an inner accretion disk origin of the line. To our knowledge this is the first strong evidence for a relativistic line in a neutron star LMXB. This finding suggests that the broad lines seen in other neutron star LMXBs likely originate from the inner disk as well. Detailed study of such lines opens up a new way to probe neutron star parameters and their strong gravitational fields. The laor model describes the line from Ser X-1 somewhat better than diskline, and suggests that the inner accretion disk radius is less than 6GM/c(exp 2). This is consistent with the weak magnetic fields of LMXBs, and may point towards a high compactness and rapid spin of the neutron star. Finally, the inferred source inclination angle in the approximate range 50-60 deg is consistent with the lack of dipping from Ser X-1.

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.

Flux trap effect study in a sub-critical neutron assembly using activation methods

NASA Astrophysics Data System (ADS)

Routsonis, K.; Stoulos, S.; Clouvas, A.; Catsaros, N.; Varvayianni, M.; Manolopoulou, M.

2016-09-01

The neutron flux trap effect was experimentally studied in the subcritical assembly of the Atomic and Nuclear Physics Laboratory of the Aristotle University of Thessaloniki, using delayed gamma neutron activation analysis. Measurements were taken within the natural uranium fuel grid, in vertical levels symmetrical to the Am-Be neutron source, before and after the removal of fuel elements, permitting likewise a basic study of the vertical flux profile. Three identical flux traps of diamond shape were created by removing four fuel rods for each one. Two (n, γ) reactions and one (n, p) threshold reaction were selected for thermal, epithermal and fast flux study. Results of thermal and epithermal flux obtained through the 197Au (n, γ) 198Au and 186W (n, γ) 187W reactions, with and without Cd covers, to differentiate between the two flux regions. The 58Ni (n, p) 58Co reaction was used for the fast flux determination. An interpolation technique based on local procedures was applied to fit the cross sections data and the neutron flux spectrum. End results show a maximum thermal flux increase of 105% at the source level, pointing to a high potential to increase in the available thermal flux for future experiments. The increase in thermal flux is not accompanied by a comparable decrease in epithermal or fast flux, since thermal flux gain is higher than epithermal and fast neutron flux loss. So, the neutron reflection is mainly responsible for the thermal neutron increase, contributing to 89% at the central axial position.

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 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...

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.

Nakedly singular non-vacuum gravitating equilibrium states

NASA Astrophysics Data System (ADS)

Woszczyna, Andrzej; Kutschera, Marek; Kubis, Sebastian; Czaja, Wojciech; Plaszczyk, Piotr; Golda, Zdzisław A.

2016-01-01

Non-vacuum static spherically symmetric spacetimes with central point-like repulsive gravity sources are investigated. Both the symmetries of spacetime and the degree of irregularity of curvature invariants, are the same as for the Schwarzschild case. The equilibrium configurations are modelled using the neutron star polytrope equation of state.

SKYSHINEIII. Calculating Effects of Structure Design on Neutron Dose Rates in Air

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

Lampley, C.M.; Andrews, C.M.; Wells, M.B.

1988-12-01

SKYSHINE was designed to aid in the evaluation of the effects of structure geometry on the gamma-ray dose rate at given detector positions outside of a building housing gamma-ray sources. The program considers a rectangular structure enclosed by four walls and a roof. Each of the walls and the roof of the building may be subdivided into up to nine different areas, representing different materials or different thicknesses of the same material for those positions of the wall or roof. Basic sets of iron and concrete slab transmission and reflection data for 6.2 MeV gamma-rays are part of the SKYSHINEmore » block data. These data, as well as parametric air transport data for line-beam sources at a number of energies between 0.6 MeV and 6.2 MeV and ranges to 3750 ft, are used to estimate the various components of the gamma-ray dose rate at positions outside of the building. The gamma-ray source is assumed to be a 6.2 MeV point-isotropic source. SKYSHINE-III provides an increase in versatility over the original SKYSHINE code in that it addresses both neutron and gamma-ray point sources. In addition, the emitted radiation may be characterized by an energy emission spectrum defined by the user. A new SKYSHINE data base is also included.« less

Impacts of the Detection of Cassiopeia A Point Source.

PubMed

Umeda; Nomoto; Tsuruta; Mineshige

2000-05-10

Very recently the Chandra first light observation discovered a point-like source in the Cassiopeia A supernova remnant. This detection was subsequently confirmed by the analyses of the archival data from both ROSAT and Einstein observations. Here we compare the results from these observations with the scenarios involving both black holes (BHs) and neutron stars (NSs). If this point source is a BH, we offer as a promising model a disk-corona type model with a low accretion rate in which a soft photon source at approximately 0.1 keV is Comptonized by higher energy electrons in the corona. If it is an NS, the dominant radiation observed by Chandra most likely originates from smaller, hotter regions of the stellar surface, but we argue that it is still worthwhile to compare the cooler component from the rest of the surface with cooling theories. We emphasize that the detection of this point source itself should potentially provide enormous impacts on the theories of supernova explosion, progenitor scenario, compact remnant formation, accretion to compact objects, and NS thermal evolution.

Neutron Reflectometry and Small Angle Neutron Scattering of ABC Miktoarm Terpolymer Thin-Films

NASA Astrophysics Data System (ADS)

Arras, Matthias M. L.; Wang, Weiyu; Mahalik, Jyoti P.; Hong, Kunlun; Sumpter, Bobby G.; Smith, Gregory S.; Chernyy, Sergey; Kim, Hyeyoung; Russell, Thomas P.

Due to the constraint of the junction point in miktoarm terpolymers, where three chains meet, ABC miktoarm terpolymers are promising to obtain nanostructured, long-range ordered materials. We present details of the thin-film structure of ABC miktoarm terpolymers in the poly(styrene), poly(isoprene), poly(2-vinylpyridine) (PS-PI-P2VP) system, investigated by neutron reflectometry and small angle neutron scattering. To this end, we synthesized partially deuterated versions of the PS-PI-P2VP and investigated annealed samples, spin-coated to various thicknesses of the bulk repeat period. Furthermore, we investigated the structural change upon selective blending with homopolymers or fullerenes. We find that thin-film constraints on the morphology can vanish after only twice the repetition period. In addition, it is indicated that nanoparticles improve the ordering in these systems, however, this seems to be not necessarily true for homopolymer blending. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

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.

Neutron measurements in near-Earth orbit with COMPTEL

NASA Technical Reports Server (NTRS)

Morris, D. J.; Aarts, H.; Bennett, K.; Lockwood, J. A.; Mcconnell, M. L.; Ryan, J. M.; Schoenfelder, V.; Steinle, H.; Peng, X.

1995-01-01

The fast neutron flux in near-Earth orbit has been measured with the COMPTEL instrument on the Compton Gamma Ray Observatory (CGRO). For this measurement one of COMPTEL's seven liquid scintillator modules was used as an uncollimated neutron detector with threshold of 12.8 MeV. The measurements cover a range of 4.8 to 15.5 GV in vertical cutoff rigidity and 3 deg to 177 deg in spacecraft geocenter zenith angle. One of the measurements occurred near the minimum of the deepest Forbush decrease ever observed by ground-level neutron monitors. After correction for solar modulation, the total flux is well fitted by separable functions in rigidity and zenith angle. With the spacecraft pointed near the nadir the flux is consistent with balloon measurements of the atmospheric neutron albedo. The flux varies by about a factor of 4 between the extremes of rigidity and a factor of 2 between the extremes of zenith angle. The effect of the spacecraft mass in shielding the detector from the atmospheric neutron albedo is much more important than its role as a source of additional secondary neutrons. The neutron spectral hardness varies little with rigidity or zenith angle and lies in the range spanned by earlier atmospheric neutron albedo measurements.

The S-Process Branching-Point at 205PB

NASA Astrophysics Data System (ADS)

Tonchev, Anton; Tsoneva, N.; Bhatia, C.; Arnold, C. W.; Goriely, S.; Hammond, S. L.; Kelley, J. H.; Kwan, E.; Lenske, H.; Piekarewicz, J.; Raut, R.; Rusev, G.; Shizuma, T.; Tornow, W.

2017-09-01

Accurate neutron-capture cross sections for radioactive nuclei near the line of beta stability are crucial for understanding s-process nucleosynthesis. However, neutron-capture cross sections for short-lived radionuclides are difficult to measure due to the fact that the measurements require both highly radioactive samples and intense neutron sources. We consider photon scattering using monoenergetic and 100% linearly polarized photon beams to obtain the photoabsorption cross section on 206Pb below the neutron separation energy. This observable becomes an essential ingredient in the Hauser-Feshbach statistical model for calculations of capture cross sections on 205Pb. The newly obtained photoabsorption information is also used to estimate the Maxwellian-averaged radiative cross section of 205Pb(n,g)206Pb at 30 keV. The astrophysical impact of this measurement on s-process nucleosynthesis will be discussed. This work was performed under the auspices of US DOE by LLNL under Contract DE-AC52-07NA27344.

Preparation and characteristics of epoxy/clay/B4C nanocomposite at high concentration of boron carbide for neutron shielding application

NASA Astrophysics Data System (ADS)

Kiani, Mohammad Amin; Ahmadi, Seyed Javad; Outokesh, Mohammad; Adeli, Ruhollah; Mohammadi, Aghil

2017-12-01

In this research, the characteristics of the prepared samples in epoxy matrix by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), as well as scanning electron microscope (SEM) are evaluated. Meanwhile, the obtained mechanical properties of the specimen are investigated. Thermogravimetric analysis (TGA) is also employed to evaluate the thermal degradation of manufactured nanocomposites. The thermal neutron absorption properties of nanocomposites containing 3 wt% of montmorillonite nanoclay (closite30B) have been studied experimentally, using an Am-Be point source. Mechanical tests reveal that the higher B4C concentrations, the more tensile strengths, but lower Young's modulus in all samples under consideration. TGA analysis also shows that thermal stability of the nanocomposite, increases in presence of B4C. Finally, neutron absorption analysis shows that increasing the B4C concentration leads to a nonlinearly build-up of neutron absorption cross section.

Enhancement of neutron radiation dose by the addition of sulphur-33 atoms.

PubMed

Porras, I

2008-04-07

The use of neutrons in radiotherapy allows the possibility of producing nuclear reactions in a specific target inserted in the medium. (10)B is being used to induce reactions (n, alpha), a technique called boron neutron capture therapy. I have studied the possibility of inducing a similar reaction using the nucleus of (33)S, for which the reaction cross section presents resonances for keV neutrons, the highest peak occurring at 13.5 keV. Here shown, by means of Monte Carlo simulation of point-like sources of neutrons in this energy range, is an enhancement effect on the absorbed dose in water by the addition of (33)S atoms. In addition to this, as the range of the alpha particle is of the order of a mammalian cell size, the energy deposition via this reaction results mainly inside the cells adjacent to the interaction site. The main conclusion of the present work is that the insertion of these sulphur atoms in tumoral cells would enhance the effect of neutron irradiation in the keV range.

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.

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.

Laser fusion neutron source employing compression with short pulse lasers

DOEpatents

Sefcik, Joseph A; Wilks, Scott C

2013-11-05

A method and system for achieving fusion is provided. The method includes providing laser source that generates a laser beam and a target that includes a capsule embedded in the target and filled with DT gas. The laser beam is directed at the target. The laser beam helps create an electron beam within the target. The electron beam heats the capsule, the DT gas, and the area surrounding the capsule. At a certain point equilibrium is reached. At the equilibrium point, the capsule implodes and generates enough pressure on the DT gas to ignite the DT gas and fuse the DT gas nuclei.

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.

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

Preliminary skyshine calculations for the Poloidal Diverter Tokamak Experiment

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

Nigg, D.W.; Wheeler, F.J.

1981-01-01

The Poloidal Diverter Experiment (PDX) facility at Princeton University is the first operating tokamak to require substantial radiation shielding. A calculational model has been developed to estimate the radiation dose in the PDX control room and at the site boundary due to the skyshine effect. An efficient one-dimensional method is used to compute the neutron and capture gamma leakage currents at the top surface of the PDX roof shield. This method employs an S /SUB n/ calculation in slab geometry and, for the PDX, is superior to spherical models found in the literature. If certain conditions are met, the slabmore » model provides the exact probability of leakage out the top surface of the roof for fusion source neutrons and for capture gamma rays produced in the PDX floor and roof shield. The model also provides the correct neutron and capture gamma leakage current spectra and angular distributions, averaged over the top roof shield surface. For the PDX, this method is nearly as accurate as multidimensional techniques for computing the roof leakage and is much less costly. The actual neutron skyshine dose is computed using a Monte Carlo model with the neutron source at the roof surface obtained from the slab S /SUB n/ calculation. The capture gamma dose is computed using a simple point-kernel single-scatter method.« less

Modeling GW170817 based on numerical relativity and its implications

NASA Astrophysics Data System (ADS)

Shibata, Masaru; Fujibayashi, Sho; Hotokezaka, Kenta; Kiuchi, Kenta; Kyutoku, Koutarou; Sekiguchi, Yuichiro; Tanaka, Masaomi

2017-12-01

Gravitational-wave observation together with a large number of electromagnetic observations shows that the source of the latest gravitational-wave event, GW170817, detected primarily by advanced LIGO, is the merger of a binary neutron star. We attempt to interpret this observational event based on our results of numerical-relativity simulations performed so far, paying particular attention to the optical and infrared observations. We finally reach a conclusion that this event is described consistently by the presence of a long-lived hypermassive or supramassive neutron star as the merger remnant because (i) significant contamination by lanthanide elements along our line of sight to this source can be avoided by the strong neutrino irradiation from it and (ii) it could play a crucial role in producing an ejecta component of appreciable mass with fast motion in the postmerger phase. We also point out that (I) the neutron-star equation of state has to be sufficiently stiff (i.e., the maximum mass of cold spherical neutron stars, Mmax, has to be appreciably higher than 2 M⊙) in order for a long-lived massive neutron star to be formed as the merger remnant for the binary systems of GW170817, for which the initial total mass is ≳2.73 M⊙ , and (II) the absence of optical counterparts associated with relativistic ejecta suggests a not-extremely-high value of Mmax approximately as 2.15 - 2.25 M⊙ .

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...

Footprint Characteristics of Cosmic-Ray Neutron Sensors for Soil Moisture Monitoring

NASA Astrophysics Data System (ADS)

Schrön, Martin; Köhli, Markus; Zreda, Marek; Dietrich, Peter; Zacharias, Steffen

2015-04-01

Cosmic-ray neutron sensing is a unique and an increasingly accepted method to monitor the effective soil water content at the field scale. The technology is famous for its low maintenance, non-invasiveness, continuous measurement, and most importantly, for its large footprint. Being more representative than point data and finer resolved than remote-sensing products, cosmic-ray neutron derived soil moisture products provide unrivaled advantage for mesoscale hydrologic and land surface models. The method takes advantage of neutrons induced by cosmic radiation which are extraordinarily sensitive to hydrogen and behave like a hot gas. Information about nearby water sources are quickly mixed in a domain of tens of hectares in air. Since experimental determination of the actual spatial extent is hardly possible, scientists have applied numerical models to address the footprint characteristics. We have revisited previous neutron transport simulations and present a modified conceptual design and refined physical assumptions. Our revised study reveals new insights into probing distance and water sensitivity of detected neutrons under various environmental conditions. These results sharpen the range of interpretation concerning the spatial extent of integral soil moisture products derived from cosmic-ray neutron counts. Our findings will have important impact on calibration strategies, on scales for data assimilation and on the interpolation of soil moisture data derived from mobile cosmic-ray neutron surveys.

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.

Spectral Models of Neutron Star Magnetospheres

NASA Technical Reports Server (NTRS)

Romani, Roger W.

1997-01-01

We revisit the association of unidentified Galactic plane EGRET sources with tracers of recent massive star formation and death. Up-to-date catalogs of OB associations, SNR's, young pulsars, H2 regions and young open clusters were used in finding counterparts for a recent list of EGRET sources. It has been argued for some time that EGRET source positions are correlated with SNR's and OB associations as a class; we extend such analyses by finding additional counterparts and assessing the probability of individual source identifications. Among the several scenarios relating EGRET sources to massive stars, we focus on young neutron stars as the origin of the gamma-ray emission. The characteristics of the candidate identifications are compared to the known gamma-ray pulsar sample and to detailed Galactic population syntheses using our outer gap pulsar model of gamma-ray emission. Both the spatial distribution and luminosity function of the candidates are in good agreement with the model predictions; we infer that young pulsars can account for the bulk of the excess low latitude EGRET sources. We show that with this identification, the gamma-ray point sources provide an important new window into the history of recent massive star death in the solar neighborhood.

Generic guide concepts for the European Spallation Source

NASA Astrophysics Data System (ADS)

Zendler, C.; Martin Rodriguez, D.; Bentley, P. M.

2015-12-01

The construction of the European Spallation Source (ESS) faces many challenges from the neutron beam transport point of view: the spallation source is specified as being driven by a 5 MW beam of protons, each with 2 GeV energy, and yet the requirements in instrument background suppression relative to measured signal vary between 10-6 and 10-8. The energetic particles, particularly above 20 MeV, which are expected to be produced in abundance in the target, have to be filtered in order to make the beamlines safe, operational and provide good quality measurements with low background. We present generic neutron guides of short and medium length instruments which are optimised for good performance at minimal cost. Direct line of sight to the source is avoided twice, with either the first point out of line of sight or both being inside the bunker (20 m) to minimise shielding costs. These guide geometries are regarded as a baseline to define standards for instruments to be constructed at ESS. They are used to find commonalities and develop principles and solutions for common problems. Lastly, we report the impact of employing the over-illumination concept to mitigate losses from random misalignment passively, and that over-illumination should be used sparingly in key locations to be effective. For more widespread alignment issues, a more direct, active approach is likely to be needed.

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...

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

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.

Rhodium self-powered neutron detector as a suitable on-line thermal neutron flux monitor in BNCT treatments

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

Miller, Marcelo E.; Sztejnberg, Manuel L.; Gonzalez, Sara J.

2011-12-15

Purpose: A rhodium self-powered neutron detector (Rh SPND) has been specifically developed by the Comision Nacional de Energia Atomica (CNEA) of Argentina to measure locally and in real time thermal neutron fluxes in patients treated with boron neutron capture therapy (BNCT). In this work, the thermal and epithermal neutron response of the Rh SPND was evaluated by studying the detector response to two different reactor spectra. In addition, during clinical trials of the BNCT Project of the CNEA, on-line neutron flux measurements using the specially designed detector were assessed. Methods: The first calibration of the detector was done with themore » well-thermalized neutron spectrum of the CNEA RA-3 reactor thermal column. For this purpose, the reactor spectrum was approximated by a Maxwell-Boltzmann distribution in the thermal energy range. The second calibration was done at different positions along the central axis of a water-filled cylindrical phantom, placed in the mixed thermal-epithermal neutron beam of CNEA RA-6 reactor. In this latter case, the RA-6 neutron spectrum had been well characterized by both calculation and measurement, and it presented some marked differences with the ideal spectrum considered for SPND calibrations at RA-3. In addition, the RA-6 neutron spectrum varied with depth in the water phantom and thus the percentage of the epithermal contribution to the total neutron flux changed at each measurement location. Local (one point-position) and global (several points-positions) and thermal and mixed-field thermal neutron sensitivities were determined from these measurements. Thermal neutron flux was also measured during BNCT clinical trials within the irradiation fields incident on the patients. In order to achieve this, the detector was placed on patient's skin at dosimetric reference points for each one of the fields. System stability was adequate for this kind of measurement. Results: Local mixed-field thermal neutron sensitivities and global thermal and mixed-field thermal neutron sensitivities derived from measurements performed at the RA-6 were compared and no significant differences were found. Global RA-6-based thermal neutron sensitivity showed agreement with pure thermal neutron sensitivity measurements performed in the RA-3 spectrum. Additionally, the detector response proved nearly unchanged by differences in neutron spectra from real (RA-6 BNCT beam) and ideal (considered for calibration calculations at RA-3) neutron source descriptions. The results confirm that the special design of the Rh SPND can be considered as having a pure thermal response for neutron spectra with epithermal-to-thermal flux ratios up to 12%. In addition, the linear response of the detector to thermal flux allows the use of a mixed-field thermal neutron sensitivity of 1.95 {+-} 0.05 x 10{sup -21} A n{sup -1}{center_dot}cm{sup 2}{center_dot}s. This sensitivity can be used in spectra with up to 21% epithermal-to-thermal flux ratio without significant error due to epithermal neutron and gamma induced effects. The values of the measured fluxes in clinical applications had discrepancies with calculated results that were in the range of -25% to +30%, which shows the importance of a local on-line independent measurement as part of a treatment planning quality control system. Conclusions: The usefulness of the CNEA Rh SPND for the on-line local measurement of thermal neutron flux on BNCT patients has been demonstrated based on an appropriate neutron spectra calibration and clinical applications.« less

Rhodium self-powered neutron detector as a suitable on-line thermal neutron flux monitor in BNCT treatments.

PubMed

Miller, Marcelo E; Sztejnberg, Manuel L; González, Sara J; Thorp, Silvia I; Longhino, Juan M; Estryk, Guillermo

2011-12-01

A rhodium self-powered neutron detector (Rh SPND) has been specifically developed by the Comisión Nacional de Energía Atómica (CNEA) of Argentina to measure locally and in real time thermal neutron fluxes in patients treated with boron neutron capture therapy (BNCT). In this work, the thermal and epithermal neutron response of the Rh SPND was evaluated by studying the detector response to two different reactor spectra. In addition, during clinical trials of the BNCT Project of the CNEA, on-line neutron flux measurements using the specially designed detector were assessed. The first calibration of the detector was done with the well-thermalized neutron spectrum of the CNEA RA-3 reactor thermal column. For this purpose, the reactor spectrum was approximated by a Maxwell-Boltzmann distribution in the thermal energy range. The second calibration was done at different positions along the central axis of a water-filled cylindrical phantom, placed in the mixed thermal-epithermal neutron beam of CNEA RA-6 reactor. In this latter case, the RA-6 neutron spectrum had been well characterized by both calculation and measurement, and it presented some marked differences with the ideal spectrum considered for SPND calibrations at RA-3. In addition, the RA-6 neutron spectrum varied with depth in the water phantom and thus the percentage of the epithermal contribution to the total neutron flux changed at each measurement location. Local (one point-position) and global (several points-positions) and thermal and mixed-field thermal neutron sensitivities were determined from these measurements. Thermal neutron flux was also measured during BNCT clinical trials within the irradiation fields incident on the patients. In order to achieve this, the detector was placed on patient's skin at dosimetric reference points for each one of the fields. System stability was adequate for this kind of measurement. Local mixed-field thermal neutron sensitivities and global thermal and mixed-field thermal neutron sensitivities derived from measurements performed at the RA-6 were compared and no significant differences were found. Global RA-6-based thermal neutron sensitivity showed agreement with pure thermal neutron sensitivity measurements performed in the RA-3 spectrum. Additionally, the detector response proved nearly unchanged by differences in neutron spectra from real (RA-6 BNCT beam) and ideal (considered for calibration calculations at RA-3) neutron source descriptions. The results confirm that the special design of the Rh SPND can be considered as having a pure thermal response for neutron spectra with epithermal-to-thermal flux ratios up to 12%. In addition, the linear response of the detector to thermal flux allows the use of a mixed-field thermal neutron sensitivity of 1.95 ± 0.05 × 10(-21) A n(-1)[middle dot]cm² [middle dot]s. This sensitivity can be used in spectra with up to 21% epithermal-to-thermal flux ratio without significant error due to epithermal neutron and gamma induced effects. The values of the measured fluxes in clinical applications had discrepancies with calculated results that were in the range of -25% to +30%, which shows the importance of a local on-line independent measurement as part of a treatment planning quality control system. The usefulness of the CNEA Rh SPND for the on-line local measurement of thermal neutron flux on BNCT patients has been demonstrated based on an appropriate neutron spectra calibration and clinical applications.

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

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

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.

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.

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.

Investigation of three-dimensional localisation of radioactive sources using a fast organic liquid scintillator detector

NASA Astrophysics Data System (ADS)

Gamage, K. A. A.; Joyce, M. J.; Taylor, G. C.

2013-04-01

In this paper we discuss the possibility of locating radioactive sources in space using a scanning-based method, relative to the three-dimensional location of the detector. The scanning system comprises an organic liquid scintillator detector, a tungsten collimator and an adjustable equatorial mount. The detector output is connected to a bespoke fast digitiser (Hybrid Instruments Ltd., UK) which streams digital samples to a personal computer. A radioactive source has been attached to a vertical wall and the data have been collected in two stages. In the first case, the scanning system was placed a couple of metres away from the wall and in the second case it moved few centimetres from the previous location, parallel to the wall. In each case data were collected from a grid of measurement points (set of azimuth angles for set of elevation angles) which covered the source on the wall. The discrimination of fast neutrons and gamma rays, detected by the organic liquid scintillator detector, is carried out on the basis of pulse gradient analysis. Images are then produced in terms of the angular distribution of events for total counts, gamma rays and neutrons for both cases. The three-dimensional location of the neutron source can be obtained by considering the relative separation of the centres of the corresponding images of angular distribution of events. The measurements have been made at the National Physical Laboratory, Teddington, Middlesex, UK.

An Information-Theoretical Approach to Image Resolution Applied to Neutron Imaging Detectors Based Upon Individual Discriminator Signals

NASA Astrophysics Data System (ADS)

Clergeau, Jean-François; Ferraton, Matthieu; Guérard, Bruno; Khaplanov, Anton; Piscitelli, Francesco; Platz, Martin; Rigal, Jean-Marie; Van Esch, Patrick; Daullé, Thibault

2017-01-01

1D or 2D neutron position sensitive detectors with individual wire or strip readout using discriminators have the advantage of being able to treat several neutron impacts partially overlapping in time, hence reducing global dead time. A single neutron impact usually gives rise to several discriminator signals. In this paper, we introduce an information-theoretical definition of image resolution. Two point-like spots of neutron impacts with a given distance between them act as a source of information (each neutron hit belongs to one spot or the other), and the detector plus signal treatment is regarded as an imperfect communication channel that transmits this information. The maximal mutual information obtained from this channel as a function of the distance between the spots allows to define a calibration-independent measure of position resolution. We then apply this measure to quantify the power of position resolution of different algorithms treating these individual discriminator signals which can be implemented in firmware. The method is then applied to different detectors existing at the ILL. Center-of-gravity methods usually improve the position resolution over best-wire algorithms which are the standard way of treating these signals.

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.

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.

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.

The GAMMA Ray Sky as Seen by Fermi: Opening a New Window on the High Energy Space Environment

DTIC Science & Technology

2009-01-01

pulsars , stars whose repeating emissions can be used as ultra-precise chronometers. Measurement of gamma radiation provides unique insight...diffuse glow are a number of bright point sources, mostly gamma ray pulsars — rotating, magnetized neutron stars — as discussed below. The bright sources...important early discoveries of Fermi have been from objects in our galaxy. The LAT has discovered 12 new pulsars that seem to be visible only in gamma

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)

An ultraluminous X-ray source powered by an accreting neutron star.

PubMed

Bachetti, M; Harrison, F A; Walton, D J; Grefenstette, B W; Chakrabarty, D; Fürst, F; Barret, D; Beloborodov, A; Boggs, S E; Christensen, F E; Craig, W W; Fabian, A C; Hailey, C J; Hornschemeier, A; Kaspi, V; Kulkarni, S R; Maccarone, T; Miller, J M; Rana, V; Stern, D; Tendulkar, S P; Tomsick, J; Webb, N A; Zhang, W W

2014-10-09

The majority of ultraluminous X-ray sources are point sources that are spatially offset from the nuclei of nearby galaxies and whose X-ray luminosities exceed the theoretical maximum for spherical infall (the Eddington limit) onto stellar-mass black holes. Their X-ray luminosities in the 0.5-10 kiloelectronvolt energy band range from 10(39) to 10(41) ergs per second. Because higher masses imply less extreme ratios of the luminosity to the isotropic Eddington limit, theoretical models have focused on black hole rather than neutron star systems. The most challenging sources to explain are those at the luminous end of the range (more than 10(40) ergs per second), which require black hole masses of 50-100 times the solar value or significant departures from the standard thin disk accretion that powers bright Galactic X-ray binaries, or both. Here we report broadband X-ray observations of the nuclear region of the galaxy M82 that reveal pulsations with an average period of 1.37 seconds and a 2.5-day sinusoidal modulation. The pulsations result from the rotation of a magnetized neutron star, and the modulation arises from its binary orbit. The pulsed flux alone corresponds to an X-ray luminosity in the 3-30 kiloelectronvolt range of 4.9 × 10(39) ergs per second. The pulsating source is spatially coincident with a variable source that can reach an X-ray luminosity in the 0.3-10 kiloelectronvolt range of 1.8 × 10(40) ergs per second. This association implies a luminosity of about 100 times the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects.

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.

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.

Study of the effects of neutron irradiation on silicon strip detectors

NASA Astrophysics Data System (ADS)

Guibellino, P.; Panizza, G.; Hall, G.; Sotthibandhu, S.; Ziock, H. J.; Ferguson, P.; Sommer, W. F.; Edwards, M.; Cartiglia, N.; Hubbard, B.; Lesloe, J.; Pitzl, D.; O'Shaughnessy, K.; Rowe, W.; Sadoziski, H. F.-W.; Seiden, A.; Spencer, E.

1992-05-01

Silicon strip detectors and test structures were exposed to neutron fluences up to Φ = 6.1 × 10 14 n/cm 2, using the ISIS neutron source at the Rutherford Appleton Laboratory (UK). In this paper we report some of our results concerning the effects of displacement damage, with a comparison of devices made of silicon of different resistivity. The various samples exposed showed a very similar dependence of the leakage current on the fluence received. We studied the change of effective doping concentration, and observed a behaviour suggesting the onset of type inversion at a fluence of ˜ 2.0 × 10 13 n/cm 2, a value which depends on the initial doping concentration. The linear increase of the depletion voltage for fluences higher than the inversion point could eventually determine the maximum fluence tolerable by silicon detectors.

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.

THE EFFECT OF TRANSIENT ACCRETION ON THE SPIN-UP OF MILLISECOND PULSARS

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

Bhattacharyya, Sudip; Chakrabarty, Deepto, E-mail: sudip@tifr.res.in

A millisecond pulsar is a neutron star that has been substantially spun up by accretion from a binary companion. A previously unrecognized factor governing the spin evolution of such pulsars is the crucial effect of nonsteady or transient accretion. We numerically compute the evolution of accreting neutron stars through a series of outburst and quiescent phases, considering the drastic variation of the accretion rate and the standard disk–magnetosphere interaction. We find that, for the same long-term average accretion rate, X-ray transients can spin up pulsars to rates several times higher than can persistent accretors, even when the spin-down due tomore » electromagnetic radiation during quiescence is included. We also compute an analytical expression for the equilibrium spin frequency in transients, by taking spin equilibrium to mean that no net angular momentum is transferred to the neutron star in each outburst cycle. We find that the equilibrium spin rate for transients, which depends on the peak accretion rate during outbursts, can be much higher than that for persistent sources. This explains our numerical finding. This finding implies that any meaningful study of neutron star spin and magnetic field distributions requires the inclusion of the transient accretion effect, since most accreting neutron star sources are transients. Our finding also implies the existence of a submillisecond pulsar population, which is not observed. This may point to the need for a competing spin-down mechanism for the fastest-rotating accreting pulsars, such as gravitational radiation.« less

Tritium assay of Li sub 2 O pellets in the LBM/LOTUS experiments

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

Quanci, J.; Azam, S.; Bertone, P.

1986-01-01

One of the objectives of the Lithium Blanket Module (LBM) program is to test the ability of advanced neutronics codes to model the tritium breeding characteristics of a fusion blanket exposed to a toroidal fusion neutron source. The LBM consists of over 20,000 cylindrical lithium oxide pellets and numerous diagnostic pellets and wafers. The LBM has been irradiated at the Ecole Polytechnique Federale de Lausanne (EPFL) LOTUS facility with a Haefely sealed neutron generator that gives a point deuterium-tritium neutron source up to 5 {times} 10{sup 12} 14-MeV n/s. Both Princeton Plasma Physics Laboratory (PPL) and EPFL assayed the tritiummore » bred at various positions in the LBM. EPFL employed a dissolution technique while PPL recovered the tritium by a thermal extraction method. EPFL uses 0.38-g, 75% TD, lithium oxide diagnostic wafers to evaluate the tritium bred in the LBM. PPPL employs a thermal extraction method to determine the tritium bred in lithium oxide samples. In the initial experiments, diagnostic pellets and wafers were placed at five locations in the LBM central removable test rod at distances of 3, 9, 21, 36, and 48 cm from the front face of the module. The two sets of data for the tritium bred in the LBM along its centerline as a function of distance from the front face of the module were compared with each other, and with the predictions of two-dimensional neutronics codes. 1 ref.« less

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

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

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.

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.

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.

Safety and control of accelerator-driven subcritical systems

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

Rief, H.; Takahashi, H.

1995-10-01

To study control and safety of accelertor driven nuclear systems, a one point kinetic model was developed and programed. It deals with fast transients as a function of reactivity insertion. Doppler feedback, and the intensity of an external neutron source. The model allows for a simultaneous calculation of an equivalent critical reactor. It was validated by a comparison with a benchmark specified by the Nuclear Energy Agency Committee of Reactor Physics. Additional features are the possibility of inserting a linear or quadratic time dependent reactivity ramp which may account for gravity induced accidents like earthquakes, the possibility to shut downmore » the external neutron source by an exponential decay law of the form exp({minus}t/{tau}), and a graphical display of the power and reactivity changes. The calculations revealed that such boosters behave quite benignly even if they are only slightly subcritical.« less

ON THE MASS DISTRIBUTION AND BIRTH MASSES OF NEUTRON STARS

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

Oezel, Feryal; Psaltis, Dimitrios; Santos Villarreal, Antonio

We investigate the distribution of neutron star masses in different populations of binaries, employing Bayesian statistical techniques. In particular, we explore the differences in neutron star masses between sources that have experienced distinct evolutionary paths and accretion episodes. We find that the distribution of neutron star masses in non-recycled eclipsing high-mass binaries as well as of slow pulsars, which are all believed to be near their birth masses, has a mean of 1.28 M{sub Sun} and a dispersion of 0.24 M{sub Sun }. These values are consistent with expectations for neutron star formation in core-collapse supernovae. On the other hand,more » double neutron stars, which are also believed to be near their birth masses, have a much narrower mass distribution, peaking at 1.33 M{sub Sun }, but with a dispersion of only 0.05 M{sub Sun }. Such a small dispersion cannot easily be understood and perhaps points to a particular and rare formation channel. The mass distribution of neutron stars that have been recycled has a mean of 1.48 M{sub Sun} and a dispersion of 0.2 M{sub Sun }, consistent with the expectation that they have experienced extended mass accretion episodes. The fact that only a very small fraction of recycled neutron stars in the inferred distribution have masses that exceed {approx}2 M{sub Sun} suggests that only a few of these neutron stars cross the mass threshold to form low-mass black holes.« less

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

Exploiting Fission Chain Reaction Dynamics to Image Fissile Materials

NASA Astrophysics Data System (ADS)

Chapman, Peter Henry

Radiation imaging is one potential method to verify nuclear weapons dismantlement. The neutron coded aperture imager (NCAI), jointly developed by Oak Ridge National Laboratory (ORNL) and Sandia National Laboratories (SNL), is capable of imaging sources of fast (e.g., fission spectrum) neutrons using an array of organic scintillators. This work presents a method developed to discriminate between non-multiplying (i.e., non-fissile) neutron sources and multiplying (i.e., fissile) neutron sources using the NCAI. This method exploits the dynamics of fission chain-reactions; it applies time-correlated pulse-height (TCPH) analysis to identify neutrons in fission chain reactions. TCPH analyzes the neutron energy deposited in the organic scintillator vs. the apparent neutron time-of-flight. Energy deposition is estimated from light output, and time-of-flight is estimated from the time between the neutron interaction and the immediately preceding gamma interaction. Neutrons that deposit more energy than can be accounted for by their apparent time-of-flight are identified as fission chain-reaction neutrons, and the image is reconstructed using only these neutron detection events. This analysis was applied to measurements of weapons-grade plutonium (WGPu) metal and 252Cf performed at the Nevada National Security Site (NNSS) Device Assembly Facility (DAF) in July 2015. The results demonstrate it is possible to eliminate the non-fissile 252Cf source from the image while preserving the fissileWGPu source. TCPH analysis was also applied to additional scenes in which theWGPu and 252Cf sources were measured individually. The results of these separate measurements further demonstrate the ability to remove the non-fissile 252Cf source and retain the fissileWGPu source. Simulations performed using MCNPX-PoliMi indicate that in a one hour measurement, solid spheres ofWGPu are retained at a 1sigma level for neutron multiplications M -˜ 3.0 and above, while hollowWGPu spheres are retained for M -˜ 2.7 and above.

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.

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.

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.

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...

Tritium assay of Li/sub 2/O in the LBM/LOTUS experiments

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

Quanci, J.; Azam, S.; Bertone, P.

1986-11-01

The Lithium Blanket Module (LBM) is an assembly of over 20,000 cylindrical lithium oxide pellets in an array representative of a limited-coverage breeding zone for a toroidal fusion device. A principal objective of the LBM program is to test the ability of advanced neutronics coding to model the tritium breeding characteristics of a fusion device blanket. The LBM has been irradiated at the Ecole Polytechnique Federale de Lausanne (EPFL) LOTUS facility with a 14 MeV point-neutron source. Princeton Plasma Physics Laboratory (PPPL) and EPFL assayed the tritium bred in lithium oxide diagnostic samples placed at various positions in the LBM.more » PPPL employed a thermal extraction technique while EPFL used a dissolution method. The results for the assay are reported and compared to MCNP Monte Carlo neutronics calculations for the LBM/LOTUS system.« less

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).

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.

Beam dynamics studies of a 30 MeV RF linac for neutron production

NASA Astrophysics Data System (ADS)

Nayak, B.; Krishnagopal, S.; Acharya, S.

2018-02-01

Design of a 30 MeV, 10 Amp RF linac as neutron source has been carried out by means of ASTRA simulation code. Here we discuss details of design simulations for three different cases i.e Thermionic , DC and RF photocathode guns and compare them as injectors to a 30 MeV RF linac for n-ToF production. A detailed study on choice of input parameters of the beam from point of view of transmission efficiency and beam quality at the output have been described. We found that thermionic gun isn't suitable for this application. Both DC and RF photocathode gun can be used. RF photocathode gun would be of better performance.

Determination of elements in hospital waste with neutron activation analysis method

NASA Astrophysics Data System (ADS)

Dwijananti, P.; Astuti, B.; Alwiyah; Fianti

2018-03-01

The producer of the biggest B3 waste is hospital. The waste is from medical and laboratory activities. The purpose of this study is to determine the elements contained in the liquid waste from hospital and calculate the levels of these elements. This research was done by analysis of the neutron activation conducted at BATAN Yogyakarta. The neutron activation analysis is divided into two stages: activation of the samples using neutron sources of reactor Kartini, then chopping by using a set of tools, gamma spectrometer with HPGe detector. Qualitative and quantitative analysis were done by matching the gamma spectrum peak to the Neutron Activation Table. The sample was taken from four points of the liquid waste treatment plant (WWTP) Bhakti Wira Tamtama Semarang hospital. The results showed that the samples containing elements of Cr, Zn, Fe, Co, and Na, with the levels of each element is Cr (0.033 - 0.075) mg/L, Zn (0.090 - 1.048) mg/L, Fe (2.937-37.743) mg/L, Co (0.005-0.023) mg/L, and Na (61.088-116.330) mg/L. Comparing to the standard value, the liquid is safe to the environment.

Generation of the neutron response function of an NE213 scintillator for fusion applications

NASA Astrophysics Data System (ADS)

Binda, F.; Eriksson, J.; Ericsson, G.; Hellesen, C.; Conroy, S.; Nocente, M.; Sundén, E. Andersson; JET Contributors

2017-09-01

In this work we present a method to evaluate the neutron response function of an NE213 liquid scintillator. This method is particularly useful when the proton light yield function of the detector has not been measured, since it is based on a proton light yield function taken from literature, MCNPX simulations, measurements of gamma-rays from a calibration source and measurements of neutrons from fusion experiments with ohmic plasmas. The inclusion of the latter improves the description of the proton light yield function in the energy range of interest (around 2.46 MeV). We apply this method to an NE213 detector installed at JET, inside the radiation shielding of the magnetic proton recoil (MPRu) spectrometer, and present the results from the calibration along with some examples of application of the response function to perform neutron emission spectroscopy (NES) of fusion plasmas. We also investigate how the choice of the proton light yield function affects the NES analysis, finding that the result does not change significantly. This points to the fact that the method for the evaluation of the neutron response function is robust and gives reliable results.

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.

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.

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.

Soil Moisture Estimation Across Scales with Mobile Sensors for Cosmic-Ray Neutrons from the Ground and Air

NASA Astrophysics Data System (ADS)

Schrön, Martin; Köhler, Mandy; Bannehr, Lutz; Köhli, Markus; Fersch, Benjamin; Rebmann, Corinna; Mai, Juliane; Cuntz, Matthias; Kögler, Simon; Schröter, Ingmar; Wollschläger, Ute; Oswald, Sascha; Dietrich, Peter; Zacharias, Steffen

2016-04-01

Soil moisture is a key variable for environmental sciences, but its determination at various scales and depths is still an open challenge. Cosmic-ray neutron sensing has become a well accepted and unique method to monitor an effective soil water content, covering tens of hectares in area and tens of centimeters in depth. The technology is famous for its low maintanance, non-invasiveness, continous measurement, and most importantly its large footprint and penetration depth. Beeing more representative than point data, and finer resolved plus deeper penetrating than remote-sensing products, cosmic-ray neutron derived soil moisture products provide unrivaled advantage for agriculture, regional hydrologic and land surface models. The method takes advantage of omnipresent neutrons which are extraordinarily sensitive to hydrogen in soil, plants, snow and air. Unwanted hydrogen sources in the footprint can be excluded by local calibration to extract the pure soil water information. However, this procedure is not feasible for mobile measurements, where neutron detectors are mounted on a car to do catchment-scale surveys. As a solution to that problem, we suggest strategies to correct spatial neutron data with the help of available spatial data of soil type, landuse and vegetation. We further present results of mobile rover campaigns at various scales and conditions, covering small sites from 0.2 km2 to catchments of 100 km2 area, and complex terrain from agricultural fields, urban areas, forests, to snowy alpine sites. As the rover is limited to accessible roads, we further investigated the applicability of airborne measurements. First tests with a gyrocopter at 150 to 200m heights proofed the concept of airborne neutron detection for environmental sciences. Moreover, neutron transport simulations confirm an improved areal coverage during these campaigns. Mobile neutron measurements at the ground or air are a promising tool for the detection of water sources across many scales. The method has a great potential to improve spatial performance of hydrological models, and help to assess regional soil moisture states for agriculture and flood risk management.

Gadolinium for neutron detection in current nuclear instrumentation research: A review

NASA Astrophysics Data System (ADS)

Dumazert, J.; Coulon, R.; Lecomte, Q.; Bertrand, G. H. V.; Hamel, M.

2018-02-01

Natural gadolinium displays a number of remarkable physical properties: it is a rare earth element, composed of seven stable or quasi-stable isotopes, with an exceptionally high magnetization and a Curie point near room temperature. Its use in the field of nuclear instrumentation historically relates to its efficiency as a neutron poison in power reactors. Gadolinium is indeed the naturally occurring element with the highest interaction probability with neutrons at thermal energy, shared between Gd-157 (15.65%, 254000 b cross section) and Gd-155 (14.8%, 60900 b) isotopes. Considering that neutron capture results in an isotopic change, followed by a radiative rearrangement of nuclear and atomic structures, Gd may be embodied not merely as a neutron poison but as a neutron converter into a prompt photon and an electron source term. Depending on the nature and energy of the reaction products (from a few-keV Auger electrons up to 8 MeV gamma rays) that the detector aims at isolating as an indirect neutron signature, a variety of sensor media and counting methods have been introduced during the last decades. This review first draws a theoretical description of the radiative cascade following Gd(n , γ) capture. The cascade may be subdivided into regions of interest, each corresponding to dedicated detection designs and optimizations whose current status is detailed. This inventory has allowed the authors to extract and benchmark key figures of merit for the definition of a detection scheme: neutron attenuation, neutron sensitivity (cps/nv), gamma rejection, neutron detection limit in a mixed field, intrinsic or extrinsic moderation, and transportability. On this basis, the authors have identified promising paths for Gd-based neutron detection in contemporary instrumentation.

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.

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

The likely optical counterpart of X-ray transient KS 1731-260

NASA Astrophysics Data System (ADS)

Wijnands, Rudy; Groot, Paul J.; Miller, Jon J.; Markwardt, Craig; Lewin, Walter H. G.; van der Klis, Michiel

2001-07-01

During our 27 March 2001 Chandra observation of the neutron star X-ray transient KS 1731-260, two X-ray sources were detected (Wijnands et al. 2001, ApJL submitted, astro-ph/0107380). One of those sources is very likely a star in the USNO A2.0 optical catalog (Monet et al. 1998, USNO-SA2.0, U.S. Naval Observatory, Washington DC) and in the Two Micron All Sky Survey (2MASS) point source catalog with a position (from 2MASS) of R.A = 17h34m12.70s, Dec. -26d05m48.4s (+/- 0.2 arcseconds).

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.

Neutron coincidence counting based on time interval analysis with one- and two-dimensional Rossi-alpha distributions: an application for passive neutron waste assay

NASA Astrophysics Data System (ADS)

Bruggeman, M.; Baeten, P.; De Boeck, W.; Carchon, R.

1996-02-01

Neutron coincidence counting is commonly used for the non-destructive assay of plutonium bearing waste or for safeguards verification measurements. A major drawback of conventional coincidence counting is related to the fact that a valid calibration is needed to convert a neutron coincidence count rate to a 240Pu equivalent mass ( 240Pu eq). In waste assay, calibrations are made for representative waste matrices and source distributions. The actual waste however may have quite different matrices and source distributions compared to the calibration samples. This often results in a bias of the assay result. This paper presents a new neutron multiplicity sensitive coincidence counting technique including an auto-calibration of the neutron detection efficiency. The coincidence counting principle is based on the recording of one- and two-dimensional Rossi-alpha distributions triggered respectively by pulse pairs and by pulse triplets. Rossi-alpha distributions allow an easy discrimination between real and accidental coincidences and are aimed at being measured by a PC-based fast time interval analyser. The Rossi-alpha distributions can be easily expressed in terms of a limited number of factorial moments of the neutron multiplicity distributions. The presented technique allows an unbiased measurement of the 240Pu eq mass. The presented theory—which will be indicated as Time Interval Analysis (TIA)—is complementary to Time Correlation Analysis (TCA) theories which were developed in the past, but is from the theoretical point of view much simpler and allows a straightforward calculation of deadtime corrections and error propagation. Analytical expressions are derived for the Rossi-alpha distributions as a function of the factorial moments of the efficiency dependent multiplicity distributions. The validity of the proposed theory is demonstrated and verified via Monte Carlo simulations of pulse trains and the subsequent analysis of the simulated data.

Performance of the full size nGEM detector for the SPIDER experiment

NASA Astrophysics Data System (ADS)

Muraro, A.; Croci, G.; Albani, G.; Claps, G.; Cavenago, M.; Cazzaniga, C.; Dalla Palma, M.; Grosso, G.; Murtas, F.; Pasqualotto, R.; Perelli Cippo, E.; Rebai, M.; Tardocchi, M.; Tollin, M.; Gorini, G.

2016-03-01

The ITER neutral beam test facility under construction in Padova will host two experimental devices: SPIDER, a 100 kV negative H/D RF beam source, and MITICA, a full scale, 1 MeV deuterium beam injector. SPIDER will start operations in 2016 while MITICA is expected to start during 2019. Both devices feature a beam dump used to stop the produced deuteron beam. Detection of fusion neutrons produced between beam-deuterons and dump-implanted deuterons will be used as a means to resolve the horizontal beam intensity profile. The neutron detection system will be placed right behind the beam dump, as close to the neutron emitting surface as possible thus providing the map of the neutron emission on the beam dump surface. The system uses nGEM neutron detectors. These are Gas Electron Multiplier detectors equipped with a cathode that also serves as neutron-proton converter foil. The cathode is designed to ensure that most of the detected neutrons at a point of the nGEM surface are emitted from the corresponding beamlet footprint (with dimensions of about 40×22 mm2) on the dump front surface. The size of the nGEM detector for SPIDER is 352 mm×200 mm. Several smaller size prototypes have been successfully made in the last years and the experience gained on these detectors has led to the production of the full size detector for SPIDER during 2014. This nGEM has a read-out board made of 256 pads (arranged in a 16×16 matrix) each with a dimension of 22 mm×13 mm. This paper describes the production of this detector and its tests (in terms of beam profile reconstruction capability, uniformity over the active area, gamma rejection capability and time stability) performed on the ROTAX beam-line at the ISIS spallation source (Didcot-UK).

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

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.

Gravity and Extreme Magnetism SMEX

NASA Technical Reports Server (NTRS)

Swank, Jean; Kallman, Timothy R.; Jahoda, Keith M.

2008-01-01

Gas accreting ont,o black holes and neutron stars form a dynamic system generating X-rays with spectroscopic signatures and varying on time scales determined by the system. The radiation from various parts of these systems is surely polarized and compact sources have been calculated to give rise to net polarization from the unresolved sum of the radiation from the systems. Polarization has been looked to for some time as also bearing the imprint of strong gravity and providing complementary information that could resolve ambiguities between the physical models that can give rise to frequencies, time delays, and spectra. In the cases of both stellar black holes and supermassive black holes the net polarizations predicted for probable disk and corona models are less than 10 needed. This sensitivity can be achieved, even for sources as faint as 1 milliCrab, in the Gravity and Extreme Magnetism SMEX (GEMS) mission that uses foil mirrors and Time Projection Chamber detectors. Similarities have been pointed out between the timing and the spectral characteristics of low mass X-ray binaries and stellar black hole sources. Polarization measurements for these sources could play a role in determining the configuration of the disk and the neutron star.

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.

Cross-Section Measurements of the Kr86(γ,n) Reaction to Probe the s-Process Branching at Kr85

NASA Astrophysics Data System (ADS)

Raut, R.; Tonchev, A. P.; Rusev, G.; Tornow, W.; Iliadis, C.; Lugaro, M.; Buntain, J.; Goriely, S.; Kelley, J. H.; Schwengner, R.; Banu, A.; Tsoneva, N.

2013-09-01

We have carried out photodisintegration cross-section measurements on Kr86 using monoenergetic photon beams ranging from the neutron separation energy, Sn=9.86MeV, to 13 MeV. We combine our experimental Kr86(γ,n)Kr85 cross section with results from our recent Kr86(γ,γ') measurement below the neutron separation energy to obtain the complete nuclear dipole response of Kr86. The new experimental information is used to predict the neutron capture cross section of Kr85, an important branching point nucleus on the abundance flow path during s-process nucleosynthesis. Our new and more precise Kr85(n,γ)Kr86 cross section allows us to produce more precise predictions of the Kr86 abundance from s-process models. In particular, we find that the models of the s process in asymptotic giant branch stars of mass <1.5M⊙, where the C13 neutron source burns convectively rather than radiatively, represent a possible solution for the highest Kr86∶Kr82 ratios observed in meteoritic stardust SiC grains.

Cross-section measurements of the 86Kr(γ,n) reaction to probe the s-process branching at 85Kr.

PubMed

Raut, R; Tonchev, A P; Rusev, G; Tornow, W; Iliadis, C; Lugaro, M; Buntain, J; Goriely, S; Kelley, J H; Schwengner, R; Banu, A; Tsoneva, N

2013-09-13

We have carried out photodisintegration cross-section measurements on 86Kr using monoenergetic photon beams ranging from the neutron separation energy, S(n) = 9.86  MeV, to 13 MeV. We combine our experimental 86Kr(γ,n)85Kr cross section with results from our recent 86Kr(γ,γ') measurement below the neutron separation energy to obtain the complete nuclear dipole response of 86Kr. The new experimental information is used to predict the neutron capture cross section of 85Kr, an important branching point nucleus on the abundance flow path during s-process nucleosynthesis. Our new and more precise 85Kr(n,γ)86Kr cross section allows us to produce more precise predictions of the 86Kr abundance from s-process models. In particular, we find that the models of the s process in asymptotic giant branch stars of mass <1.5M⊙, where the 13C neutron source burns convectively rather than radiatively, represent a possible solution for the highest 86Kr:82Kr ratios observed in meteoritic stardust SiC grains.

Optimization of a multi-channel parabolic guide for the material science diffractometer STRESS-SPEC at FRM II

NASA Astrophysics Data System (ADS)

Rebelo Kornmeier, Joana; Ostermann, Andreas; Hofmann, Michael; Gibmeier, Jens

2014-02-01

Neutron strain diffractometers usually use slits to define a gauge volume within engineering samples. In this study a multi-channel parabolic neutron guide was developed to be used instead of the primary slit to minimise the loss of intensity and vertical definition of the gauge volume when using slits placed far away from the measurement position in bulky components. The major advantage of a focusing guide is that the maximum flux is not at the exit of the guide as for a slit system but at the focal point relatively far away from the exit of the guide. Monte Carlo simulations were used to optimise the multi-channel parabolic guide with respect to the instrument characteristics of the diffractometer STRESS-SPEC at the FRM II neutron source. Also the simulations are in excellent agreement with experimental measurements using the optimised multi-channel parabolic guide at the neutron diffractometer. In addition the performance of the guide was compared to the standard slit setup at STRESS-SPEC using a single bead weld sample used in earlier round robin tests for residual strain measurements.

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.

Effect of Using Thorium Molten Salts on the Neutronic Performance of PACER

NASA Astrophysics Data System (ADS)

Acır, Adem; Übeyli, Mustafa

2010-04-01

Utilization of nuclear explosives can produce a significant amount of energy which can be converted into electricity via a nuclear fusion power plant. An important fusion reactor concept using peaceful nuclear explosives is called as PACER which has an underground containment vessel to handle the nuclear explosives safely. In this reactor, Flibe has been considered as a working coolant for both tritium breeding and heat transferring. However, the rich neutron source supplied from the peaceful nuclear explosives can be used also for fissile fuel production. In this study, the effect of using thorium molten salts on the neutronic performance of the PACER was investigated. The computations were performed for various coolants bearing thorium and/or uranium-233 with respect to the molten salt zone thickness in the blanket. Results pointed out that an increase in the fissile content of the salt increased the neutronic performance of the reactor remarkably. In addition, higher energy production was obtained with thorium molten salts compared to the pure mode of the reactor. Moreover, a large quantity of 233U was produced in the blanket in all cases.

Polarized Neutron Studies on Antiferromagnetic Single Crystals: Technical Report No. 4

DOE R&D Accomplishments Database

Nathans, R.; Riste, T.; Shirane, G.; Shull, C.G.

1958-11-26

The theory of neutron scattering by magnetic crystals as given by Halpern and Johnson predicts changes in the polarization state of the neutron beam upon scattering which depend upon the relative orientation of the neutron polarization vector and the crystal magnetic axis. This was investigated experimentally with a polarized beam spectrometer using single crystals of Cr{sub 2}O{sub 3} and alpha - Fe{sub 2}O{sub 3} in which reside unique antiferromagnetic axes. Studies were made on several different reflections in both crystals for a number of different temperatures both below and above the Neel point. Results support the theoretical predictions and indicate directions for the moments in these crystals consistent with previous work. A more detailed study of the polarization changes in the (111) reflection in alpha - Fe{sub 2}O{sub 3} at room temperature on application of a magnetic field was carried out, The results indicate that the principal source of the parasitic ferromagnetism in hematite is essentially independent of the orientation of the antiferromagnetic domains within the crystal.

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.

SU-E-T-90: Accuracy of Calibration of Lithium-6 and -7 Enriched LiF TLDs for Neutron Measurements in High Energy Radiotherapy

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

Keehan, S; Franich, R; Taylor, M

Purpose: To determine the potential error involved in the interpretation of neutron measurements from medical linear accelerators (linacs) using TLD-600H and TLD-700H if standard AmBe and {sup 252}Cf neutron sources are used for calibration without proper inclusion of neutron energy spectrum information. Methods: The Kerma due to neutrons can be calculated from the energy released by various nuclear interactions (elastic and inelastic scatter, (n,α), (n,p), (n,d), (n,t), (n,2n), etc.). The response of each TLD can be considered the sum of the neutron and gamma components; each proportional to the Kerma. Using the difference between the measured TLD responses and themore » ratio of the calculated Kerma for each material, the neutron component of the response can be calculated. The Monte Carlo code MCNP6 has been used to calculate the neutron energy spectra resulting from photonuclear interactions in a Varian 21EX linac. TLDs have been exposed to the mixed (γ-n) field produced by a linac and AmBe and {sup 252}Cf standard neutron sources. Results: For dosimetry of neutrons from AmBe or {sup 252}Cf sources, assuming TLD-700H insensitivity to neutrons will Result in 10% or 20% overestimation of neutron doses respectively.For dosimetry of neutrons produced in a Varian 21EX, applying a calibration factor derived from a standard AmBe or {sup 252}Cf source will Result in an overestimation of neutron fluence, by as much as a factor of 47.The assumption of TLD-700H insensitivity to neutrons produced by linacs leads to a negligible error due to the extremely high Kerma ratio (600H/700H) of 3000 for the assumed neutron spectrum. Conclusion: Lithium-enriched TLDs calibrated with AmBe and/or {sup 252}Cf neutron sources are not accurate for use under the neutron energy spectrum produced by a medical linear accelerator.« less

The D-D Neutron Generator as an Alternative to Am(Li) Isotopic Neutron Source in the Active Well Coincidence Counter

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

McElroy, Robert Dennis; Cleveland, Steven L.

The 235U mass assay of bulk uranium items, such as oxide canisters, fuel pellets, and fuel assemblies, is not achievable by traditional gamma-ray assay techniques due to the limited penetration of the item by the characteristic 235U gamma rays. Instead, fast neutron interrogation methods such as active neutron coincidence counting must be used. For international safeguards applications, the most commonly used active neutron systems, the Active Well Coincidence Counter (AWCC), Uranium Neutron Collar (UNCL) and 252Cf Shuffler, rely on fast neutron interrogation using an isotopic neutron source [i.e., 252Cf or Am(Li)] to achieve better measurement accuracies than are possible usingmore » gamma-ray techniques for high-mass, high-density items. However, the Am(Li) sources required for the AWCC and UNCL systems are no longer manufactured, and newly produced systems rely on limited supplies of sources salvaged from disused instruments. The 252Cf shuffler systems rely on the use of high-output 252Cf sources, which while still available have become extremely costly for use in routine operations and require replacement every five to seven years. Lack of a suitable alternative neutron interrogation source would leave a potentially significant gap in the safeguarding of uranium processing facilities. In this work, we made use of Oak Ridge National Laboratory’s (ORNL’s) Large Volume Active Well Coincidence Counter (LV-AWCC) and a commercially available deuterium-deuterium (D-D) neutron generator to examine the potential of the D-D neutron generator as an alternative to the isotopic sources. We present the performance of the LV-AWCC with D-D generator for the assay of 235U based on the results of Monte Carlo N-Particle (MCNP) simulations and measurements of depleted uranium (DU), low enriched uranium (LEU), and highly enriched uranium (HEU) items.« less

Performance comparison of NE213 detectors for their application in moisture measurement

PubMed

Naqvi; Nagadi; Rehman; Kidwai

2000-10-01

The pulse shape discrimination (PSD) characteristic and neutron detection efficiency of NE213 detectors have been measured for their application in moisture measurements using 252Cf and 241Am-Be sources. In PSD studies, neutron peak to valley (Pn/V) ratio and figure of merit M were measured at four different bias values for cylindrical 50, 125 and 250 mm diameter NE213 detectors. The result of this study has shown that better PSD performance with the NE213 detector can be achieved with a smaller volume detector in conjunction with a neutron source with smaller gamma-ray/neutron ratio. The neutron detection efficiency of the 125 mm diameter NE213 detector for 241Am-Be and 252Cf source spectra was determined at 0.85, 1.25 and 1.75 MeV bias energies using the experimental neutron detection efficiency data of the same detector over 0.1-10 MeV energy range. Due to different energy spectra of the 241Am-Be and 252Cf sources, integrated efficiency of the 125 mm diameter NE213 detector for the two sources shows bias dependence. At smaller bias, 252Cf source has larger efficiency but as the bias is increased, the detector has larger efficiency for 241Am-Be source. This study has revealed that NE213 detector has better performance (such as PSD and neutron detection efficiency) in simultaneous detection of neutron and gamma-rays in moisture measurements, if it is used in conjunction with 241Am-Be source at higher detector bias.

Design of a setup for 252Cf neutron source for storage and analysis purpose

NASA Astrophysics Data System (ADS)

Hei, Daqian; Zhuang, Haocheng; Jia, Wenbao; Cheng, Can; Jiang, Zhou; Wang, Hongtao; Chen, Da

2016-11-01

252Cf is a reliable isotopic neutron source and widely used in the prompt gamma ray neutron activation analysis (PGNAA) technique. A cylindrical barrel made by polymethyl methacrylate contained with the boric acid solution was designed for storage and application of a 5 μg 252Cf neutron source. The size of the setup was optimized with Monte Carlo code. The experiments were performed and the results showed the doses were reduced with the setup and less than the allowable limit. The intensity and collimating radius of the neutron beam could also be adjusted through different collimator.

Interplay Between Theory and Observation

NASA Astrophysics Data System (ADS)

Hebb Swank, Jean

2013-01-01

In the early 1970’s, after the rocket flights had identified some sources, Uhuru was surveying the sky, and neutron stars, black holes, supernova remnants, clusters of galaxies had been tentatively identified as responsible. Coming from a theoretical particle physics background, I was especially interested in the astrophysical manifestations of fundamental physics in neutron stars and black holes, and history shows the exciting interplay between theory and observation. OSO-8 provided my first example of an observation that made a clear simple identification; the cooling black body spectrum with constant radius strongly pointed to a neutron star as the source. The instrument had enough area, energy resolution and time resolution to see it. Unbeknownst to me, thermonuclear flashes of accreting material had been predicted and they had been proposed as the explanation for bursts. At the next level of detail, to accurately determine mass, to account for emissivity (the color correction) and general relativity, and use the observations to determine mass and radius, and the nuclear fuel, many other parameters play a role. RXTE was designed to answer many of the questions developed as a consequence of earlier missions. One of them was the question of whether the neutron stars in the bursts were spun up pulsars and whether the low frequency quasi-periodic pulsations (QPO) seen with EXOSAT and Ginga were interactions of the accretion disk and a pulsar. RXTE’s first observations of low mass x-ray binaries showed the kilohertz quasi-periodic oscillations and the burst oscillations. The PCA had the area and the time resolution to see them. I should have known that kilohertz QPO had also been predicted. Again, while some aspects are simple, at the next level, for both neutron stars and black holes, many other parameters and questions of interpretation must be considered. These especially affect the ability to use the sources identified as black holes to understand their influence on space-time. It was to look at these sources with a different tool that the Gravity and Extreme Magnetism SMEX GEMS was proposed. Its termination because of cost predictions is an example of the severe practical difficulties of astrophysics.

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

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.

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.

Effects of phonon broadening on x-ray near-edge spectra in molecular crystals

NASA Astrophysics Data System (ADS)

Vinson, John; Jach, Terrence; Elam, Tim; Denlinger, Jonathon

2014-03-01

Calculations of near-edge x-ray spectra are often carried out using the average atomic coordinates from x-ray or neutron scattering experiments or from density functional theory (DFT) energy minimization. This neglects disorder from thermal and zero-point vibrations. Here we look at the nitrogen K-edge of ammonium chloride and ammonium nitrate, comparing Bethe-Salpeter calculations of absorption and fluorescence to experiment. We find that intra-molecular vibrational effects lead to significant, non-uniform broadening of the spectra, and that for some features zero-point motion is the primary source of the observed shape.

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.

The Probing In-Situ With Neutron and Gamma Rays (PING) Instrument for Planetary Composition Measurements

NASA Technical Reports Server (NTRS)

Parsons, A.; Bodnarik, J.; Evans, L.; McClanahan, T.; Namkung, M.; Nowicki, S.; Schweitzer, J.; Starr, R.

2012-01-01

The Probing In situ with Neutrons and Gamma rays (PING) instrument (formerly named PNG-GRAND) [I] experiment is an innovative application of the active neutron-gamma ray technology successfully used in oil field well logging and mineral exploration on Earth over many decades. The objective of our active neutron-gamma ray technology program at NASA Goddard Space Flight Center (NASA/GSFC) is to bring PING to the point where it can be flown on a variety of surface lander or rover missions to the Moon, Mars, Venus, asteroids, comets and the satellites of the outer planets and measure their bulk surface and subsurface elemental composition without the need to drill into the surface. Gamma-Ray Spectrometers (GRS) have been incorporated into numerous orbital planetary science missions. While orbital measurements can map a planet, they have low spatial and elemental sensitivity due to the low surface gamma ray emission rates reSUlting from using cosmic rays as an excitation source, PING overcomes this limitation in situ by incorporating a powerful neutron excitation source that permits significantly higher elemental sensitivity elemental composition measurements. PING combines a 14 MeV deuterium-tritium Pulsed Neutron Generator (PNG) with a gamma ray spectrometer and two neutron detectors to produce a landed instrument that can determine the elemental composition of a planet down to 30 - 50 cm below the planet's surface, The penetrating nature of .5 - 10 MeV gamma rays and 14 MeV neutrons allows such sub-surface composition measurements to be made without the need to drill into or otherwise disturb the planetary surface, thus greatly simplifying the lander design, We are cun'ently testing a PING prototype at a unique outdoor neutron instrumentation test facility at NASA/GSFC that provides two large (1.8 m x 1.8 m x ,9 m) granite and basalt test formations placed outdoors in an empty field, Since an independent trace elemental analysis has been performed on both these Columbia River basalt and Concord Gray granite materials, these large samples present two known standards with which to compare PING's experimentally measured elemental composition results, We will present both gamma ray and neutron experimental results from PING measurements of the granite and basalt test formations in various layering configurations and compare the results to the known composition.

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.

In situ calibration of neutron activation system on the large helical device

NASA Astrophysics Data System (ADS)

Pu, N.; Nishitani, T.; Isobe, M.; Ogawa, K.; Kawase, H.; Tanaka, T.; Li, S. Y.; Yoshihashi, S.; Uritani, A.

2017-11-01

In situ calibration of the neutron activation system on the Large Helical Device (LHD) was performed by using an intense 252Cf neutron source. To simulate a ring-shaped neutron source, we installed a railway inside the LHD vacuum vessel and made a train loaded with the 252Cf source run along a typical magnetic axis position. Three activation capsules loaded with thirty pieces of indium foils stacked with total mass of approximately 18 g were prepared. Each capsule was irradiated over 15 h while the train was circulating. The activation response coefficient (9.4 ± 1.2) × 10-8 of 115In(n, n')115mIn reaction obtained from the experiment is in good agreement with results from three-dimensional neutron transport calculations using the Monte Carlo neutron transport simulation code 6. The activation response coefficients of 2.45 MeV birth neutron and secondary 14.1 MeV neutron from deuterium plasma were evaluated from the activation response coefficient obtained in this calibration experiment with results from three-dimensional neutron calculations using the Monte Carlo neutron transport simulation code 6.

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.

Hardy Star Survives Supernova Blast

NASA Image and Video Library

2014-03-20

This composite image contains data from Chandra (purple) that provides evidence for the survival of a companion star from the blast of a supernova explosion. Chandra's X-rays reveal a point-like source in the supernova remnant at the location of a massive star. The data suggest that mass is being pulled away from the massive star towards a neutron star or a black hole companion. If confirmed, this would be only the third binary system containing both a massive star and a neutron star or black hole ever found in the aftermath of a supernova. This supernova remnant is found embedded in clouds of ionized hydrogen, which are shown in optical light (yellow and cyan) from the MCELS survey, along with additional optical data from the DSS (white).

LMC P3

NASA Image and Video Library

2016-10-10

This composite image contains data from Chandra (purple) that provides evidence for the survival of a companion star from the blast of a supernova explosion. Chandra's X-rays reveal a point-like source in the supernova remnant at the location of a massive star. The data suggest that mass is being pulled away from the massive star towards a neutron star or a black hole companion. If confirmed, this would be only the third binary system containing both a massive star and a neutron star or black hole ever found in the aftermath of a supernova. This supernova remnant is found embedded in clouds of ionized hydrogen, which are shown in optical light (yellow and cyan) from the MCELS survey, along with additional optical data from the DSS (white).

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.

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.

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.

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

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 yield and induced radioactivity: a study of 235-MeV proton and 3-GeV electron accelerators.

PubMed

Hsu, Yung-Cheng; Lai, Bo-Lun; Sheu, Rong-Jiun

2016-01-01

This study evaluated the magnitude of potential neutron yield and induced radioactivity of two new accelerators in Taiwan: a 235-MeV proton cyclotron for radiation therapy and a 3-GeV electron synchrotron serving as the injector for the Taiwan Photon Source. From a nuclear interaction point of view, neutron production from targets bombarded with high-energy particles is intrinsically related to the resulting target activation. Two multi-particle interaction and transport codes, FLUKA and MCNPX, were used in this study. To ensure prediction quality, much effort was devoted to the associated benchmark calculations. Comparisons of the accelerators' results for three target materials (copper, stainless steel and tissue) are presented. Although the proton-induced neutron yields were higher than those induced by electrons, the maximal neutron production rates of both accelerators were comparable according to their respective beam outputs during typical operation. Activation products in the targets of the two accelerators were unexpectedly similar because the primary reaction channels for proton- and electron-induced activation are (p,pn) and (γ,n), respectively. The resulting residual activities and remnant dose rates as a function of time were examined and discussed. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Object Tracking Vision System for Mapping the UCN τ Apparatus Volume

NASA Astrophysics Data System (ADS)

Lumb, Rowan; UCNtau Collaboration

2016-09-01

The UCN τ collaboration has an immediate goal to measure the lifetime of the free neutron to within 0.1%, i.e. about 1 s. The UCN τ apparatus is a magneto-gravitational ``bottle'' system. This system holds low energy, or ultracold, neutrons in the apparatus with the constraint of gravity, and keeps these low energy neutrons from interacting with the bottle via a strong 1 T surface magnetic field created by a bowl-shaped array of permanent magnets. The apparatus is wrapped with energized coils to supply a magnetic field throughout the ''bottle'' volume to prevent depolarization of the neutrons. An object-tracking stereo-vision system will be presented that precisely tracks a Hall probe and allows a mapping of the magnetic field throughout the volume of the UCN τ bottle. The stereo-vision system utilizes two cameras and open source openCV software to track an object's 3-d position in space in real time. The desired resolution is +/-1 mm resolution along each axis. The vision system is being used as part of an even larger system to map the magnetic field of the UCN τ apparatus and expose any possible systematic effects due to field cancellation or low field points which could allow neutrons to depolarize and possibly escape from the apparatus undetected. Tennessee Technological University.

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

Transport calculation of neutrons leaked to the surroundings of the facilities by the JCO criticality accident in Tokai-mura.

PubMed

Imanaka, T

2001-09-01

A transport calculation of the neutrons leaked to the environment by the JCO criticality accident was carried out based on three-dimensional geometrical models of the buildings within the JCO territory. Our work started from an initial step to simulate the leakage process of neutrons from the precipitation tank, and proceeded to a step to calculate the neutron propagation throughout the JCO facilities. The total fission number during the accident in the precipitation tank was evaluated to be 2.5 x 10(18) by comparing the calculated neutron-induced activities per 235U fission with the measured values in a stainless-steel net sample taken 2 m from the precipitation tank. Shield effects by various structures within the JCO facilities were evaluated by comparing the present results with a previous calculation using two-dimensional models which suppose a point source of the fission spectrum in the air above the ground without any shield structures. The shield effect by the precipitation tank, itself, was obtained to be a factor of 3. The shield factor by the conversion building varied between 1.1 and 2, depending on the direction from the building. The shield effect by the surrounding buildings within the JCO territory was between I and 5, also depending on the direction.

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.

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

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.

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

James, S St.; Argento, D; Stewart, R

Purpose: The University of Washington Medical Center offers neutron therapy for the palliative and definitive treatment of selected cancers. In vivo field verification has the potential to improve the safe and effective delivery of neutron therapy. We propose a portal imaging method that relies on the creation of positron emitting isotopes (11C and 15O) through (n, 2n) reactions with a PMMA plate placed below the patient. After field delivery, the plate is retrieved from the vault and imaged using a reader that detects annihilation photons. The spatial pattern of activity produced in the PMMA plate provides information to reconstruct themore » neutron fluence map needed to confirm treatment delivery. Methods: We used MCNP to simulate the accumulation of 11C activity in a slab of PMMA 2 mm thick, and GATE was used to simulate the sensitivity and spatial resolution of a prototype imaging system. BGO crystal thicknesses of 1 cm, 2 cm and 3 cm were simulated with detector separations of 2 cm. Crystal pitches of 2 mm and 4 mm were evaluated. Back-projection of the events was used to create a planar image. The spatial resolution was taken to be the FWHM of the reconstructed point source image. Results: The system sensitivity for a point source in the center of the field of view was found to range from 58% for 1 cm thick BGO with 2 mm crystal pitch to 74% for the 3 cm thick BGO crystals with 4 mm crystal pitch. The spatial resolution at the center of the field of view was found to be 1.5 mm for the system with 2 mm crystal pitch and 2.8 mm for the system with the 4 mm crystal pitch. Conclusion: BGO crystals with 4 mm crystal pitch and 3 cm length would offer the best sensitivity reader.« 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

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

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.

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

Mass Measurements beyond the Major r-Process Waiting Point {sup 80}Zn

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

Baruah, S.; Herlert, A.; Schweikhard, L.

2008-12-31

High-precision mass measurements on neutron-rich zinc isotopes {sup 71m,72-81}Zn have been performed with the Penning trap mass spectrometer ISOLTRAP. For the first time, the mass of {sup 81}Zn has been experimentally determined. This makes {sup 80}Zn the first of the few major waiting points along the path of the astrophysical rapid neutron-capture process where neutron-separation energy and neutron-capture Q-value are determined experimentally. The astrophysical conditions required for this waiting point and its associated abundance signatures to occur in r-process models can now be mapped precisely. The measurements also confirm the robustness of the N=50 shell closure for Z=30.

Performance analysis of fusion nuclear-data benchmark experiments for light to heavy materials in MeV energy region with a neutron spectrum shifter

NASA Astrophysics Data System (ADS)

Murata, Isao; Ohta, Masayuki; Miyamaru, Hiroyuki; Kondo, Keitaro; Yoshida, Shigeo; Iida, Toshiyuki; Ochiai, Kentaro; Konno, Chikara

2011-10-01

Nuclear data are indispensable for development of fusion reactor candidate materials. However, benchmarking of the nuclear data in MeV energy region is not yet adequate. In the present study, benchmark performance in the MeV energy region was investigated theoretically for experiments by using a 14 MeV neutron source. We carried out a systematical analysis for light to heavy materials. As a result, the benchmark performance for the neutron spectrum was confirmed to be acceptable, while for gamma-rays it was not sufficiently accurate. Consequently, a spectrum shifter has to be applied. Beryllium had the best performance as a shifter. Moreover, a preliminary examination of whether it is really acceptable that only the spectrum before the last collision is considered in the benchmark performance analysis. It was pointed out that not only the last collision but also earlier collisions should be considered equally in the benchmark performance analysis.

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.

Construction of monoenergetic neutron calibration fields using 45Sc(p, n)45Ti reaction at JAEA.

PubMed

Tanimura, Y; Saegusa, J; Shikaze, Y; Tsutsumi, M; Shimizu, S; Yoshizawa, M

2007-01-01

The 8 and 27 keV monoenergetic neutron calibration fields have been developed by using (45)Sc(p, n)(45)Ti reaction. Protons from a 4-MV Pelletron accelerator are used to bombard a thin scandium target evaporated onto a platinum disc. The proton energies are finely adjusted to the resonance to generate the 8 and 27 keV neutrons by applying a high voltage to the target assemblies. The neutron energies were measured using the time-of-flight method with a lithium glass scintillation detector. The neutron fluences at a calibration point located at 50 cm from the target were evaluated using Bonner spheres. A long counter was placed at 2.2 m from the target and at 60 degrees to the direction of the proton beam in order to monitor the fluence at the calibration point. Fluence and dose equivalent rates at the calibration point are sufficient to calibrate many types of the neutron survey metres.

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.

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.

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.

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

Updating the orbital ephemeris of the dipping source XB 1254-690 and the distance to the source

NASA Astrophysics Data System (ADS)

Gambino, Angelo F.; Iaria, Rosario; Di Salvo, Tiziana; Matranga, Marco; Burderi, Luciano; Pintore, Fabio; Riggio, Alessandro; Sanna, Andrea

2017-09-01

XB 1254-690 is a dipping low mass X-ray binary system hosting a neutron star and showing type I X-ray bursts. We aim at obtaining a more accurate orbital ephemeris and at constraining the orbital period derivative of the system for the first time. In addition, we want to better constrain the distance to the source in order to locate the system in a well defined evolutive scenario. We apply, for the first time, an orbital timing technique to XB 1254-690, using the arrival times of the dips present in the light curves that have been collected during 26 yr of X-ray pointed observations acquired from different space missions. We estimate the dip arrival times using a statistical method that weights the count-rate inside the dip with respect to the level of persistent emission outside the dip. We fit the obtained delays as a function of the orbital cycles both with a linear and a quadratic function. We infer the orbital ephemeris of XB 1254-690, improving the accuracy of the orbital period with respect to previous estimates. We infer a mass of M 2 = 0.42 ± 0.04 M ʘ for the donor star, in agreement with estimations already present in literature, assuming that the star is in thermal equilibrium while it transfers part of its mass via the inner Lagrangian point, and assuming a neutron star mass of 1.4 M ʘ. Using these assumptions, we also constrain the distance to the source, finding a value of 7.6 ± 0.8 kpc. Finally, we discuss the evolution of the system, suggesting that it is compatible with a conservative mass transfer driven by magnetic braking.

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

Incorporating delayed neutrons into the point-model equations routinely used for neutron coincidence counting in nuclear safeguards

DOE PAGES

Croft, Stephen; Favalli, Andrea

2016-09-21

Here, we extend the familiar Bӧhnel point-model equations, which are routinely used to interpret neutron coincidence counting rates, by including the contribution of delayed neutrons. After developing the necessary equations we use them to show, by providing some numerical results, what the quantitative impact of neglecting delayed neutrons is across the full range of practical nuclear safeguards applications. The influence of delayed neutrons is predicted to be small for the types of deeply sub-critical assay problems which concern the nuclear safeguards community, smaller than uncertainties arising from other factors. This is most clearly demonstrated by considering the change in themore » effective (α,n)-to-spontaneous fission prompt-neutron ratio that the inclusion of delayed neutrons gives rise to. That the influence of delayed neutrons is small is fortunate, and our results justify the long standing practice of simply neglecting them in the analysis of field measurements.« less

FIFRELIN - TRIPOLI-4® coupling for Monte Carlo simulations with a fission model. Application to shielding calculations

NASA Astrophysics Data System (ADS)

Petit, Odile; Jouanne, Cédric; Litaize, Olivier; Serot, Olivier; Chebboubi, Abdelhazize; Pénéliau, Yannick

2017-09-01

TRIPOLI-4® Monte Carlo transport code and FIFRELIN fission model have been coupled by means of external files so that neutron transport can take into account fission distributions (multiplicities and spectra) that are not averaged, as is the case when using evaluated nuclear data libraries. Spectral effects on responses in shielding configurations with fission sampling are then expected. In the present paper, the principle of this coupling is detailed and a comparison between TRIPOLI-4® fission distributions at the emission of fission neutrons is presented when using JEFF-3.1.1 evaluated data or FIFRELIN data generated either through a n/g-uncoupled mode or through a n/g-coupled mode. Finally, an application to a modified version of the ASPIS benchmark is performed and the impact of using FIFRELIN data on neutron transport is analyzed. Differences noticed on average reaction rates on the surfaces closest to the fission source are mainly due to the average prompt fission spectrum. Moreover, when working with the same average spectrum, a complementary analysis based on non-average reaction rates still shows significant differences that point out the real impact of using a fission model in neutron transport simulations.

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

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.

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

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.

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.

Behind the Scenes of the Spallation Neutron Source – The Linear Accelerator

ScienceCinema

Galambos, John

2018-06-25

The Spallation Neutron Source at Oak Ridge National Laboratory is a one-of-a-kind research facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development. Take a look inside the facility's linear accelerator.

FABRICATION OF NEUTRON SOURCES

DOEpatents

Birden, J.H.

1959-04-21

A method is presented for preparing a neutron source from polonium-210 and substances, such as beryllium and boron, characterized by emission of neutrons upon exposure to alpha particles from the polonium. According to the invention, a source is prepared by placing powdered beryllium and a platinum foil electroplated with polonium-2;.0 in a beryllium container. The container is sealed and then heated by induction to a temperature of 450 to 1100 deg C to volatilize the polonium off the foil into the powder. The heating step is terminated upon detection of a maximum in the neutron flux level.

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.

Solution-grown crystals for neutron radiation detectors, and methods of solution growth

DOEpatents

Zaitseva, Natalia P; Hull, Giulia; Cherepy, Nerine J; Payne, Stephen A; Stoeffl, Wolfgang

2012-06-26

A method according to one embodiment includes growing an organic crystal from solution, the organic crystal exhibiting a signal response signature for neutrons from a radioactive source. A system according to one embodiment includes an organic crystal having physical characteristics of formation from solution, the organic crystal exhibiting a signal response signature for neutrons from a radioactive source; and a photodetector for detecting the signal response of the organic crystal. A method according to another embodiment includes growing an organic crystal from solution, the organic crystal being large enough to exhibit a detectable signal response signature for neutrons from a radioactive source. An organic crystal according to another embodiment includes an organic crystal having physical characteristics of formation from solution, the organic crystal exhibiting a signal response signature for neutrons from a radioactive source, wherein the organic crystal has a length of greater than about 1 mm in one dimension.

Three-dimensional reconstruction of neutron, gamma-ray, and x-ray sources using spherical harmonic decomposition

NASA Astrophysics Data System (ADS)

Volegov, P. L.; Danly, C. R.; Fittinghoff, D.; Geppert-Kleinrath, V.; Grim, G.; Merrill, F. E.; Wilde, C. H.

2017-11-01

Neutron, gamma-ray, and x-ray imaging are important diagnostic tools at the National Ignition Facility (NIF) for measuring the two-dimensional (2D) size and shape of the neutron producing region, for probing the remaining ablator and measuring the extent of the DT plasmas during the stagnation phase of Inertial Confinement Fusion implosions. Due to the difficulty and expense of building these imagers, at most only a few two-dimensional projections images will be available to reconstruct the three-dimensional (3D) sources. In this paper, we present a technique that has been developed for the 3D reconstruction of neutron, gamma-ray, and x-ray sources from a minimal number of 2D projections using spherical harmonics decomposition. We present the detailed algorithms used for this characterization and the results of reconstructed sources from experimental neutron and x-ray data collected at OMEGA and NIF.

History of Chandra X-Ray Observatory

NASA Image and Video Library

2003-01-22

This Chandra X-ray observatory image of M83 shows numerous point-like neutron stars and black hole x-ray sources scattered throughout the disk of this spiral galaxy. The bright nuclear region of the galaxy glows prominently due to a burst of star formation that is estimated to have begun about 20 million years ago in the galaxy's time frame. The nuclear region, enveloped by a 7 million degree Celsius gas cloud of carbon, neon, magnesium, silicon, and sulfur atoms, contains a much higher concentration of neutron stars and black holes than the rest of the galaxy. Hot gas with a slightly lower temperature of 4 million degrees observed along the spiral arms of the galaxy suggests that star formation in this region may be occurring at a more sedate rate.

Fusion pumped laser

DOEpatents

Pappas, Daniel S.

1989-01-01

Apparatus is provided for generating energy in the form of laser radiation. A tokamak fusion reactor is provided for generating a long, or continuous, pulse of high-energy neutrons. The tokamak design provides a temperature and a magnetic field which is effective to generate a neutron flux of at least 10.sup.15 neutrons/cm.sup.2.s. A conversion medium receives neutrons from the tokamak and converts the high-energy neutrons to an energy source with an intensity and an energy effective to excite a preselected lasing medium. The energy source typically comprises fission fragments, alpha particles, and radiation from a fission event. A lasing medium is provided which is responsive to the energy source to generate a population inversion which is effective to support laser oscillations for generating output radiation.

Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

DOE PAGES

Ito, Takeyasu M.; Adamek, E. R.; Callahan, N. B.; ...

2018-01-29

We report 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 densitymore » measured at the exit of the biological shield was 184(32) UCN / cm 3, a fourfold increase from the highest previously reported. Finally, the polarized UCN density stored in an external chamber was measured to be 39(7) UCN / cm 3, which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of σ(d n) = 3 × 10 -27 e cm.« less

Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

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

Ito, Takeyasu M.; Adamek, E. R.; Callahan, N. B.

We report 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 densitymore » measured at the exit of the biological shield was 184(32) UCN / cm 3, a fourfold increase from the highest previously reported. Finally, the polarized UCN density stored in an external chamber was measured to be 39(7) UCN / cm 3, which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of σ(d n) = 3 × 10 -27 e cm.« less

Progress in Mirror-Based Fusion Neutron Source Development.

PubMed

Anikeev, A V; Bagryansky, P A; Beklemishev, A D; Ivanov, A A; Kolesnikov, E Yu; Korzhavina, M S; Korobeinikova, O A; Lizunov, A A; Maximov, V V; Murakhtin, S V; Pinzhenin, E I; Prikhodko, V V; Soldatkina, E I; Solomakhin, A L; Tsidulko, Yu A; Yakovlev, D V; Yurov, D V

2015-12-04

The Budker Institute of Nuclear Physics in worldwide collaboration has developed a project of a 14 MeV neutron source for fusion material studies and other applications. The projected neutron source of the plasma type is based on the gas dynamic trap (GDT), which is a special magnetic mirror system for plasma confinement. Essential progress in plasma parameters has been achieved in recent experiments at the GDT facility in the Budker Institute, which is a hydrogen (deuterium) prototype of the source. Stable confinement of hot-ion plasmas with the relative pressure exceeding 0.5 was demonstrated. The electron temperature was increased up to 0.9 keV in the regime with additional electron cyclotron resonance heating (ECRH) of a moderate power. These parameters are the record for axisymmetric open mirror traps. These achievements elevate the projects of a GDT-based neutron source on a higher level of competitive ability and make it possible to construct a source with parameters suitable for materials testing today. The paper presents the progress in experimental studies and numerical simulations of the mirror-based fusion neutron source and its possible applications including a fusion material test facility and a fusion-fission hybrid system.

Model-Based Least Squares Reconstruction of Coded Source Neutron Radiographs: Integrating the ORNL HFIR CG1D Source Model

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

Santos-Villalobos, Hector J; Gregor, Jens; Bingham, Philip R

2014-01-01

At the present, neutron sources cannot be fabricated small and powerful enough in order to achieve high resolution radiography while maintaining an adequate flux. One solution is to employ computational imaging techniques such as a Magnified Coded Source Imaging (CSI) system. A coded-mask is placed between the neutron source and the object. The system resolution is increased by reducing the size of the mask holes and the flux is increased by increasing the size of the coded-mask and/or the number of holes. One limitation of such system is that the resolution of current state-of-the-art scintillator-based detectors caps around 50um. Tomore » overcome this challenge, the coded-mask and object are magnified by making the distance from the coded-mask to the object much smaller than the distance from object to detector. In previous work, we have shown via synthetic experiments that our least squares method outperforms other methods in image quality and reconstruction precision because of the modeling of the CSI system components. However, the validation experiments were limited to simplistic neutron sources. In this work, we aim to model the flux distribution of a real neutron source and incorporate such a model in our least squares computational system. We provide a full description of the methodology used to characterize the neutron source and validate the method with synthetic experiments.« less

Fission meter and neutron detection using poisson distribution comparison

DOEpatents

Rowland, Mark S; Snyderman, Neal J

2014-11-18

A neutron detector system and method 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. Comparison of the observed neutron count distribution with a Poisson distribution is performed to distinguish fissile material from non-fissile material.

Multi-source irradiation facility with improved space configuration for neutron activation analysis: Design optimization.

PubMed

Kotb, N A; Solieman, Ahmed H M; El-Zakla, T; Amer, T Z; Elmeniawi, S; Comsan, M N H

2018-05-01

A neutron irradiation facility consisting of six 241 Am-Be neutron sources of 30 Ci total activity and 6.6 × 10 7 n/s total neutron yield is designed. The sources are embedded in a cubic paraffin wax, which plays a dual role as both moderator and reflector. The sample passage and irradiation channel are represented by a cylindrical path of 5 cm diameter passing through the facility core. The proposed design yields a high degree of space symmetry and thermal neutron homogeneity within 98% of flux distribution throughout the irradiated spherical sample of 5 cm diameter. The obtained thermal neutron flux is 8.0 × 10 4 n/cm 2 .s over the sample volume, with thermal-to-fast and thermal-to-epithermal ratios of 1.20 and 3.35, respectively. The design is optimized for maximizing the thermal neutron flux at sample position using the MCNP-5 code. The irradiation facility is supposed to be employed principally for neutron activation analysis. Copyright © 2018 Elsevier Ltd. All rights reserved.

New opportunities for quasielastic and inelastic neutron scattering at steady-state sources using mechanical selection of the incident and final neutron energy

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

Mamantov, Eugene

2015-06-12

We propose a modification of the neutron wide-angle velocity selector (WAVES) device that enables inelastic (in particular, quasielastic) scattering measurements not relying on the neutron time-of-flight. The proposed device is highly suitable for a steady-state neutron source, somewhat similar to a triple-axis spectrometer, but with simultaneous selection of the incident and final neutron energy over a broad range of scattering momentum transfer. Both the incident and final neutron velocities are defined by the WAVES geometry and rotation frequency. The variable energy transfer is achieved through the natural variation of the velocity of the transmitted neutrons as a function of themore » scattering angle component out of the equatorial plane.« less

A Compact Self-Driven Liquid Lithium Loop for Industrial Neutron Generation

NASA Astrophysics Data System (ADS)

Stemmley, Steven; Szott, Matt; Kalathiparambil, Kishor; Ahn, Chisung; Jurczyk, Brian; Ruzic, David

2017-10-01

A compact, closed liquid lithium loop has been developed at the University of Illinois to test and utilize the Li-7(d,n) reaction. The liquid metal loop is housed in a stainless steel trench module with embedded heating and cooling. The system was designed to handle large heat and particle fluxes for use in neutron generators as well as fusion devices, solely operating via thermo-electric MHD. The objectives of this project are two-fold, 1) produce a high energy, MeV-level, neutron source and 2) provide a self-healing, low Z, low recycling plasma facing component. The flowing volume will keep a fresh, clean, lithium surface allowing Li-7(d,n) reactions to occur as well as deuterium adsorption in the fluid, increasing the overall neutron output. Expected yields of this system are 107 n/s for 13.5 MeV neutrons and 108 n/s for 2.45 MeV neutrons. Previous work has shown that using a tapered trench design prevents dry out and allows for an increase in velocity of the fluid at the particle strike point. For heat fluxes on the order of 10's MW/m2, COMSOL models have shown that high enough velocities ( 70 cm/s) are attainable to prevent significant lithium evaporation. Future work will be aimed at addressing wettability issues of lithium in the trenches, experimentally determine the velocities required to prevent dry out, and determine the neutron output of the system. The preliminary results and discussion will be presented. DOE SBIR project DE-SC0013861.

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.

Design of thermal neutron beam based on an electron linear accelerator for BNCT.

PubMed

Zolfaghari, Mona; Sedaghatizadeh, Mahmood

2016-12-01

An electron linear accelerator (Linac) can be used for boron neutron capture therapy (BNCT) by producing thermal neutron flux. In this study, we used a Varian 2300 C/D Linac and MCNPX.2.6.0 code to simulate an electron-photoneutron source for use in BNCT. In order to decelerate the produced fast neutrons from the photoneutron source, which optimize the thermal neutron flux, a beam-shaping assembly (BSA) was simulated. After simulations, a thermal neutron flux with sharp peak at the beam exit was obtained in the order of 3.09×10 8 n/cm 2 s and 6.19×10 8 n/cm 2 s for uranium and enriched uranium (10%) as electron-photoneutron sources respectively. Also, in-phantom dose analysis indicates that the simulated thermal neutron beam can be used for treatment of shallow skin melanoma in time of about 85.4 and 43.6min for uranium and enriched uranium (10%) respectively. Copyright © 2016. Published by Elsevier Ltd.

Boron selenide semiconductor detectors for thermal neutron counting

NASA Astrophysics Data System (ADS)

Kargar, Alireza; Tower, Joshua; Cirignano, Leonard; Shah, Kanai

2013-09-01

Thermal neutron detectors in planar configuration were fabricated from B2Se3 (Boron Selenide) crystals grown at RMD Inc. All fabricated semiconductor devices were characterized for the current-voltage (I-V) characteristic and neutron counting measurement. In this study, the resistivity of crystals is reported and the collected pulse height spectra are presented for devices irradiated with the 241AmBe neutron source. Long-term stability of the B2Se3 devices for neutron detection under continuous bias and without being under continuous bias was investigated and the results are reported. The B2Se3 devices showed response to thermal neutrons of the 241AmBe source.

Determination of Moisture Content in Coke with 239Pu-Be Neutron Source and BGO Scintillation Gamma Detector

NASA Astrophysics Data System (ADS)

Grozdanov, D. N.; Aliyev, F. A.; Hramco, C.; Kopach, Yu. N.; Bystritsky, V. M.; Skoy, V. R.; Gundorin, N. A.; Ruskov, I. N.

2018-03-01

A series of experiments has been conducted at the Frank Laboratory of Neutron Physics (FLNP) of the Joint Institute for Nuclear Research (JINR) in order to study the possibility of determining the moisture content of coke using a standard neutron source. The proposed method is based on a measurement of the spectrum of prompt γ rays emitted when samples are irradiated by fast and/or thermal neutrons. The moisture content is determined from the area of the peaks of characteristic γ rays produced in the radiative capture of thermal neutrons by the proton ( E γ = 2.223 MeV) and inelastic scattering of fast neutrons by 16O (Eγ = 6.109 MeV). The 239Pu-Be neutron source (< E n > 4.5 MeV) with an intensity of 5 × 106 n/s was used to irradiate the samples under study. A scintillation detector based on a BGO crystal was used to register the characteristic γ radiation from the inelastic fast neutron scattering and slow (thermal) neutron capture. This paper presents the results of humidity measurement in the range of 2-50% [1, 2].

Calibration of a Silver Detector using a PuBe Source

DTIC Science & Technology

2012-06-14

solid state mechanisms [12]. If the source used for calibration has a known neutron flux , the detector efficiency can be determine by allowing a neutron ...between the normalized neutron flux at the different silver foil locations compared to the flux at the bottom right detector location. The differences are... neutron detection system used at the FRCHX to determine the nominal calibration factors. The type of silver detector used in the FRCHX experiment

Experimental validation of a coupled neutron-photon inverse radiation transport solver

NASA Astrophysics Data System (ADS)

Mattingly, John; Mitchell, Dean J.; Harding, Lee T.

2011-10-01

Sandia National Laboratories has developed an inverse radiation transport solver that applies nonlinear regression to coupled neutron-photon deterministic transport models. The inverse solver uses nonlinear regression to fit a radiation transport model to gamma spectrometry and neutron multiplicity counting measurements. The subject of this paper is the experimental validation of that solver. This paper describes a series of experiments conducted with a 4.5 kg sphere of α-phase, weapons-grade plutonium. The source was measured bare and reflected by high-density polyethylene (HDPE) spherical shells with total thicknesses between 1.27 and 15.24 cm. Neutron and photon emissions from the source were measured using three instruments: a gross neutron counter, a portable neutron multiplicity counter, and a high-resolution gamma spectrometer. These measurements were used as input to the inverse radiation transport solver to evaluate the solver's ability to correctly infer the configuration of the source from its measured radiation signatures.

Searching for X-ray Pulsations from Neutron Stars Using NICER

NASA Astrophysics Data System (ADS)

Ray, Paul S.; Arzoumanian, Zaven; Bogdanov, Slavko; Bult, Peter; Chakrabarty, Deepto; Guillot, Sebastien; Kust Harding, Alice; Ho, Wynn C. G.; Lamb, Frederick K.; Mahmoodifar, Simin; Miller, M. Coleman; Strohmayer, Tod E.; Wilson-Hodge, Colleen A.; Wolff, Michael Thomas

2017-08-01

The Neutron Star Interior Composition Explorer (NICER) presents an exciting new capability for discovering new modulation properties of X-ray emitting neutron stars, including large area, low background, extremely precise absolute time stamps, superb low-energy response and flexible scheduling. The Pulsation Searches and Multiwavelength Coordination working group has designed a 2.5 Ms observing program to search for pulsations and characterize the modulation properties of about 30 known or suspected neutron star sources across a number of source categories. A key early goal will be to search for pulsations from millisecond pulsars that might exhibit thermal pulsations from the surface suitable for pulse profile modeling to constrain the neutron star equation of state. In addition, we will search for pulsations from transitional millisecond pulsars, isolated neutron stars, LMXBs, accretion-powered millisecond pulsars, central compact objects and other sources. We will present our science plan and initial results from the first months of the NICER mission.

Searching for X-ray Pulsations from Neutron Stars Using NICER

NASA Astrophysics Data System (ADS)

Ray, Paul S.; Arzoumanian, Zaven; Gendreau, Keith C.; Bogdanov, Slavko; Bult, Peter; Chakrabarty, Deepto; Chakrabarty, Deepto; Guillot, Sebastien; Harding, Alice; Ho, Wynn C. G.; Lamb, Frederick; Mahmoodifar, Simin; Miller, Cole; Strohmayer, Tod; Wilson-Hodge, Colleen; Wolff, Michael T.; NICER Science Team Working Group on Pulsation Searches and Multiwavelength Coordination

2018-01-01

The Neutron Star Interior Composition Explorer (NICER) presents an exciting new capability for discovering new modulation properties of X-ray emitting neutron stars, including large area, low background, extremely precise absolute time stamps, superb low-energy response and flexible scheduling. The Pulsation Searches and Multiwavelength Coordination working group has designed a 2.5 Ms observing program to search for pulsations and characterize the modulation properties of about 30 known or suspected neutron star sources across a number of source categories. A key early goal will be to search for pulsations from millisecond pulsars that might exhibit thermal pulsations from the surface suitable for pulse profile modeling to constrain the neutron star equation of state. In addition, we will search for pulsations from transitional millisecond pulsars, isolated neutron stars, LMXBs, accretion-powered millisecond pulsars, central compact objects and other sources. We present our science plan and initial results from the first months of the NICER mission.

Development of a compact, rf-driven, pulsed ion source for neutron generation

NASA Astrophysics Data System (ADS)

Perkins, L. T.; Celata, C.; Lee, Y.; Leung, K. N.; Picard, D. S.; Vilaithong, R.; Williams, M. D.; Wutte, D.

1997-02-01

Lawrence Berkeley National Laboratory is currently developing a compact, sealed-accelerator-tube neutron generator capable of producing a neutron flux in the range of 109 to 1010 D-T neutrons per second. The ion source, a miniaturized variation of earlier radio-frequency (rf)-driven multicusp ion sources, is designed to fit within a ˜5 cm diameter borehole. Typical operating parameters include repetition rates up to 100 pps, with pulse widths between 10 and 80 μs (limited only by the available rf power supply) and source pressures as low as ˜5 mTorr. In this configuration, peak extractable hydrogen current densities exceeding 1180 mA/cm2 with H1+ yields over 94% having been achieved.

Neutron threshold activation detectors (TAD) for the detection of fissions

NASA Astrophysics Data System (ADS)

Gozani, Tsahi; Stevenson, John; King, Michael J.

2011-10-01

Prompt fission neutrons are one of the strongest signatures of the fission process. Depending on the fission inducing radiation, their average number ranges from 2.5 to 4 neutrons per fission. They are more energetic and abundant, by about 2 orders of magnitude, than the delayed neutrons (≈3 vs. ≈0.01) that are commonly used as indicators for the presence of fissionable materials. The detection of fission prompt neutrons, however, has to be done in the presence of extremely intense probing radiation that stimulated them. During irradiation, the fission stimulation radiation, X-rays or neutrons, overwhelms the neutron detectors and temporarily incapacitate them. Consequently, by the time the detectors recover from the source radiation, fission prompt neutrons are no longer emitted. In order to measure the prompt fission signatures under these circumstances, special measures are usually taken with the detectors such as heavy shielding with collimation, use of inefficient geometries, high pulse height bias and gamma-neutron separation via pulse-shape discrimination with an appropriate organic scintillator. These attempts to shield the detector from the flash of radiation result in a major loss of sensitivity. It can lead to a complete inability to detect the fission prompt neutrons. In order to overcome the blinding induced background from the source radiation, the detection of prompt fission neutrons needs to occur long after the fission event and after the detector has fully recovered from the source overload. A new approach to achieve this is to detect the delayed activation induced by the fission neutrons. The approach demonstrates a good sensitivity in adverse overload situations (gamma and neutron "flash") where fission prompt neutrons could normally not be detected. The new approach achieves the required temporal separation between the detection of prompt neutrons and the detector overload by the neutron activation of the detector material. The technique, called Threshold Activation Detection (TAD), is to utilize appropriate substances that can be selectively activated by the fission neutrons and not by the source radiation and then measure the radioactively decaying activation products (typically beta and gamma rays) well after the source pulse. The activation material should possess certain properties: a suitable half-life of the order of seconds; an energy threshold below which the numerous source neutrons will not activate it (e.g., 3 MeV); easily detectable activation products (typically >1 MeV beta and gamma rays) and have a usable cross-section for the selected reaction. Ideally the substance would be a part of the scintillator. There are several good material candidates for the TAD, including fluorine, which is a major constituent of available scintillators such as BaF 2, CaF 2 and hydrogen free liquid fluorocarbon. Thus the fluorine activation products, in particular the beta particles, can be measured with a very high efficiency in the detector. The principles, applications and experimental results obtained with the fluorine based TAD are discussed.

Neutron activation analysis traces copper artifacts to geographical point of origin

NASA Technical Reports Server (NTRS)

Conway, M.; Fields, P.; Friedman, A.; Kastner, M.; Metta, D.; Milsted, J.; Olsen, E.

1967-01-01

Impurities remaining in the metallic copper are identified and quantified by spectrographic and neutron activation analysis. Determination of the type of ore used for the copper artifact places the geographic point of origin of the artifact.

Preview of the BATSE Earth Occultation Catalog of Low Energy Gamma Ray Sources

NASA Technical Reports Server (NTRS)

Harmon, B. A.; Wilson, C. A.; Fishman, G. J.; McCollough, M. L.; Robinson, C. R.; Sahi, M.; Paciesas, W. S.; Zhang, S. N.

1999-01-01

The Burst and Transient Source Experiment (BATSE) aboard the Compton Gamma Ray Observatory (CGRO) has been detecting and monitoring point sources in the high energy sky since 1991. Although BATSE is best known for gamma ray bursts, it also monitors the sky for longer-lived sources of radiation. Using the Earth occultation technique to extract flux information, a catalog is being prepared of about 150 sources potential emission in the large area detectors (20-1000 keV). The catalog will contain light curves, representative spectra, and parametric data for black hole and neutron star binaries, active galaxies, and super-nova remnants. In this preview, we present light curves for persistent and transient sources, and also show examples of what type of information can be obtained from the BATSE Earth occultation database. Options for making the data easily accessible as an "on line" WWW document are being explored.

Principles for timing at spallation neutron sources based on developments at LANSCE

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

Nelson, R. O.; Merl, R. B.; Rose, C. R.

2001-01-01

Due to AC-power-grid frequency fluctuations, the designers for accelerator-based spallation-neutron facilities have worked to optimize the conflicting demands of accelerator and neutron chopper performance. For the first time, we are able to quantitatively access the tradeoffs between these two constraints and design or upgrade a facility to optimize total system performance using powerful new simulation techniques. We have modeled timing systems that integrate chopper controllers and chopper hardware and built new systems. Thus, at LANSCE, we now operate multiple chopper systems and the accelerator as simple slaves to a single master-timing-reference generator. Based on this experience we recommend that spallationmore » neutron sources adhere to three principles. First, timing for pulsed sources should be planned starting with extraction at a fixed phase and working backwards toward the leading edge of the beam pulse. Second, accelerator triggers and storage ring extraction commands from neutron choppers offer only marginal benefits to accelerator-based spallation sources. Third, the storage-ring RF should be phase synchronized with neutron choppers to provide extraction without the one orbit timing uncertainty.« less

The National Spallation Neutron Source (NSNS) Project

NASA Astrophysics Data System (ADS)

Appleton, Bill R.

1997-05-01

The need and justification for new sources and instrumentation in neutron science have been firmly established by numerous assessments since the early 1970s by the scientific community and the Department of Energy (DOE). In their 1996 budget, the DOE Office of Energy Research asked ORNL to lead the R&D and conceptual design effort for a next-generation spallation neutron source to be used for neutron scattering. To accomplish this, the NSNS collaboration involving five national laboratories (ANL, BNL, LANL, LBNL, and ORNL) has been formed. The NSNS reference design is for a 1-GeV linac and accumulator ring that delivers 1-MW proton beams in microsend pulses to a mercuty target; neutrons are produced by the spallation reaction, moderated, and guided into an experimental hall for neutron scattering. The design includes the necessary flexibility to upgrade the source in stages to significantly higher powers in the future and to expand the experimental capabilities. This talk will describe the origins at NSNS, the current funding status, progress on the technical design, user community input and the intended uses, and future prospects.

Revised SNAP III Training Manual

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

Moss, Calvin Elroy; Gonzales, Samuel M.; Myers, William L.

The Shielded Neutron Assay Probe (SNAP) technique was developed to determine the leakage neutron source strength of a radioactive object. The original system consisted of an Eberline TM Mini-scaler and discrete neutron detector. The system was operated by obtaining the count rate with the Eberline TM instrument, determining the absolute efficiency from a graph, and calculating the neutron source strength by hand. In 2003 the SNAP III, shown in Figure 1, was designed and built. It required the operator to position the SNAP, and then measure the source-to-detector and detectorto- reflector distances. Next the operator entered the distance measurements andmore » started the data acquisition. The SNAP acquired the required count rate and then calculated and displayed the leakage neutron source strength (NSS). The original design of the SNAP III is described in SNAP III Training Manual (ER-TRN-PLN-0258, Rev. 0, January 2004, prepared by William Baird) This report describes some changes that have been made to the SNAP III. One important change is the addition of a LEMO connector to provide neutron detection output pulses for input to the MC-15. This feature is useful in active interrogation with a neutron generator because the MC-15 has the capability to only record data when it is not gated off by a pulse from the neutron generator. This avoids recording of a lot of data during the generator pulses that are not useful. Another change was the replacement of the infrared RS-232 serial communication output by a similar output via a 4-pin LEMO connector. The current document includes a more complete explanation of how to estimate the amount of moderation around a neutron-emitting source.« less

Source Correlated Prompt Neutron Activation Analysis for Material Identification and Localization

NASA Astrophysics Data System (ADS)

Canion, Bonnie; McConchie, Seth; Landsberger, Sheldon

2017-07-01

This paper investigates the energy spectrum of photon signatures from an associated particle imaging deuterium tritium (API-DT) neutron generator interrogating shielded uranium. The goal is to investigate if signatures within the energy spectrum could be used to indirectly characterize shielded uranium when the neutron signature is attenuated. By utilizing the correlated neutron cone associated with each pixel of the API-DT neutron generator, certain materials can be identified and located via source correlated spectrometry of prompt neutron activation gamma rays. An investigation is done to determine if fission neutrons induce a significant enough signature within the prompt neutron-induced gamma-ray energy spectrum in shielding material to be useful for indirect nuclear material characterization. The signature deriving from the induced fission neutrons interacting with the shielding material was slightly elevated in polyethylene-shielding depleted uranium (DU), but was more evident in some characteristic peaks from the aluminum shielding surrounding DU.

Fast neutron irradiation tests of flash memories used in space environment at the ISIS spallation neutron source

NASA Astrophysics Data System (ADS)

Andreani, C.; Senesi, R.; Paccagnella, A.; Bagatin, M.; Gerardin, S.; Cazzaniga, C.; Frost, C. D.; Picozza, P.; Gorini, G.; Mancini, R.; Sarno, M.

2018-02-01

This paper presents a neutron accelerated study of soft errors in advanced electronic devices used in space missions, i.e. Flash memories performed at the ChipIr and VESUVIO beam lines at the ISIS spallation neutron source. The two neutron beam lines are set up to mimic the space environment spectra and allow neutron irradiation tests on Flash memories in the neutron energy range above 10 MeV and up to 800 MeV. The ISIS neutron energy spectrum is similar to the one occurring in the atmospheric as well as in space and planetary environments, with intensity enhancements varying in the range 108- 10 9 and 106- 10 7 respectively. Such conditions are suitable for the characterization of the atmospheric, space and planetary neutron radiation environments, and are directly applicable for accelerated tests of electronic components as demonstrated here in benchmark measurements performed on flash memories.

Neutron range spectrometer

DOEpatents

Manglos, Stephen H.

1989-06-06

A neutron range spectrometer and method for determining the neutron energy spectrum of a neutron emitting source are disclosed. Neutrons from the source are collimnated 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. The computer solves the following equation in the analysis: ##EQU1## where: N(x).DELTA.x=the number of neutron interactions measured between a position x and x+.DELTA.x, A.sub.i (E.sub.i).DELTA.E.sub.i =the number of incident neutrons with energy between E.sub.i and E.sub.i +.DELTA.E.sub.i, and C=C(E.sub.i)=N .sigma.(E.sub.i) where N=the number density of absorbing atoms in the position sensitive counter means and .sigma. (E.sub.i)=the average cross section of the absorbing interaction between E.sub.i and E.sub.i +.DELTA.E.sub.i.

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

Enhancing the performance of a tensioned metastable fluid detector based active interrogation system for the detection of SNM in <1 m3 containers using a D-D neutron interrogation source in moderated/reflected geometries

NASA Astrophysics Data System (ADS)

Grimes, T. F.; Hagen, A. R.; Archambault, B. C.; Taleyarkhan, R. P.

2018-03-01

This paper describes the development of a SNM detection system for interrogating 1m3 cargos via the combination of a D-D neutron interrogation source (with and without reflectors) and tensioned metastable fluid detectors (TMFDs). TMFDs have been previously shown (Taleyarkhan et al., 2008; Grimes et al., 2015; Grimes and Taleyarkhan, 2016; Archambault et al., 2017; Hagen et al., 2016) to be capable of using Threshold Energy Neutron Analysis (TENA) techniques to reject the ∼2.45 MeV D-D interrogating neutrons while still remaining sensitive to >2.45 MeV neutrons resulting from fission in the target (HEU) material. In order to enhance the performance, a paraffin reflector was included around the accelerator head. This reflector was used to direct neutrons into the package to increase the fission signal, lower the energy of the interrogating neutrons to increase the fission cross-section with HEU, and, also to direct interrogating neutrons away from the detectors in order to enhance the required discrimination between interrogating and fission neutrons. Experiments performed with a 239 Pu-Be neutron source and MnO2 indicated that impressive performance gains could be made by placing a parabolic paraffin moderator between the interrogation source and an air-filled cargo container with HEU placed at the center. However, experiments with other cargo fillers (as specified in the well-known ANSI N42.41-2007 report), and with HEU placed in locations other than the center of the package indicated that other reflector geometries might be superior due to over-"focusing" and the increased solid angle effects due to the accommodation of the moderator geometry. The best performance for the worst case of source location and box fill was obtained by placing the reflector only behind the D-D neutron source rather than in front of it. Finally, it was shown that there could be significant gains in the ability to detect concealed SNM by operating the system in multiple geometric configurations. Worst case scenarios were created by filling the box with hydrogenous material and placing the HEU as far away as possible from the neutron source. The performance of the system in the worst-case scenarios were greatly improved by exchanging the location of the accelerator and the opposite TMFD panel half way through interrogation. Using this operation, scenarios with positions of the concealed SNM that were once the most challenging to successfully detect became readily detectable.

GPU Acceleration of Mean Free Path Based Kernel Density Estimators for Monte Carlo Neutronics Simulations

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

Burke, TImothy P.; Kiedrowski, Brian C.; Martin, William R.

Kernel Density Estimators (KDEs) are a non-parametric density estimation technique that has recently been applied to Monte Carlo radiation transport simulations. Kernel density estimators are an alternative to histogram tallies for obtaining global solutions in Monte Carlo tallies. With KDEs, a single event, either a collision or particle track, can contribute to the score at multiple tally points with the uncertainty at those points being independent of the desired resolution of the solution. Thus, KDEs show potential for obtaining estimates of a global solution with reduced variance when compared to a histogram. Previously, KDEs have been applied to neutronics formore » one-group reactor physics problems and fixed source shielding applications. However, little work was done to obtain reaction rates using KDEs. This paper introduces a new form of the MFP KDE that is capable of handling general geometries. Furthermore, extending the MFP KDE to 2-D problems in continuous energy introduces inaccuracies to the solution. An ad-hoc solution to these inaccuracies is introduced that produces errors smaller than 4% at material interfaces.« less

Validation of SMAP Root Zone Soil Moisture Estimates with Improved Cosmic-Ray Neutron Probe Observations

NASA Astrophysics Data System (ADS)

Babaeian, E.; Tuller, M.; Sadeghi, M.; Franz, T.; Jones, S. B.

2017-12-01

Soil Moisture Active Passive (SMAP) soil moisture products are commonly validated based on point-scale reference measurements, despite the exorbitant spatial scale disparity. The difference between the measurement depth of point-scale sensors and the penetration depth of SMAP further complicates evaluation efforts. Cosmic-ray neutron probes (CRNP) with an approximately 500-m radius footprint provide an appealing alternative for SMAP validation. This study is focused on the validation of SMAP level-4 root zone soil moisture products with 9-km spatial resolution based on CRNP observations at twenty U.S. reference sites with climatic conditions ranging from semiarid to humid. The CRNP measurements are often biased by additional hydrogen sources such as surface water, atmospheric vapor, or mineral lattice water, which sometimes yield unrealistic moisture values in excess of the soil water storage capacity. These effects were removed during CRNP data analysis. Comparison of SMAP data with corrected CRNP observations revealed a very high correlation for most of the investigated sites, which opens new avenues for validation of current and future satellite soil moisture products.

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

Development of beryllium-based neutron target system with three-layer structure for accelerator-based neutron source for boron neutron capture therapy.

PubMed

Kumada, Hiroaki; Kurihara, Toshikazu; Yoshioka, Masakazu; Kobayashi, Hitoshi; Matsumoto, Hiroshi; Sugano, Tomei; Sakurai, Hideyuki; Sakae, Takeji; Matsumura, Akira

2015-12-01

The iBNCT project team with University of Tsukuba is developing an accelerator-based neutron source. Regarding neutron target material, our project has applied beryllium. To deal with large heat load and blistering of the target system, we developed a three-layer structure for the target system that includes a blistering mitigation material between the beryllium used as the neutron generator and the copper heat sink. The three materials were bonded through diffusion bonding using a hot isostatic pressing method. Based on several verifications, our project chose palladium as the intermediate layer. A prototype of the neutron target system was produced. We will verify that sufficient neutrons for BNCT treatment are generated by the device in the near future. Copyright © 2015 Elsevier Ltd. All rights reserved.

Investigation of neutron interactions with Ge detectors

NASA Astrophysics Data System (ADS)

Baginova, Miloslava; Vojtyla, Pavol; Povinec, Pavel P.

2018-07-01

Interactions of neutrons with a high-purity germanium detector were studied experimentally and by simulations using the GEANT4 tool. Elastic and inelastic scattering of fast neutrons as well as neutron capture on Ge nuclei were observed. Peaks induced by inelastic scattering of neutrons on 70Ge, 72Ge, 73Ge, 74Ge and 76Ge were well visible in the γ-ray spectra. In addition, peaks due to inelastic scattering of neutrons on copper and lead nuclei, including the well-known peak of 208Pb at 2614.51 keV, were detected. The GEANT4 simulations showed that the simulated spectrum was in a good agreement with the experimental one. Differences between the simulated and the measured spectra were due to the high γ-ray intensity of the used neutron source, physics implemented in GEANT4 and contamination of the neutron source.

The possible use of a spallation neutron source for neutron capture therapy with epithermal neutrons.

PubMed

Grusell, E; Condé, H; Larsson, B; Rönnqvist, T; Sornsuntisook, O; Crawford, J; Reist, H; Dahl, B; Sjöstrand, N G; Russel, G

1990-01-01

Spallation is induced in a heavy material by 72-MeV protons. The resulting neutrons can be characterized by an evaporation spectrum with a peak energy of less than 2 MeV. The neutrons are moderated in two steps: first in iron and then in carbon. Results from neutron fluence measurements in a perspex phantom placed close to the moderator are presented. Monte Carlo calculations of neutron fluence in a water phantom are also presented under some chosen configurations of spallation source and moderator. The calculations and measurements are in good agreement and show that, for proton currents of less than 0.5 mA, useful thermal-neutron fluences are attainable in the depth of the brain. However, the dose contribution from the unavoidable gamma background component has not been included in the present investigation.

Monte Carlo study on secondary neutrons in passive carbon-ion radiotherapy: identification of the main source and reduction in the secondary neutron dose.

PubMed

Yonai, Shunsuke; Matsufuji, Naruhiro; Kanai, Tatsuaki

2009-10-01

Recent successful results in passive carbon-ion radiotherapy allow the patient to live for a longer time and allow younger patients to receive the radiotherapy. Undesired radiation exposure in normal tissues far from the target volume is considerably lower than that close to the treatment target, but it is considered to be non-negligible in the estimation of the secondary cancer risk. Therefore, it is very important to reduce the undesired secondary neutron exposure in passive carbon-ion radiotherapy without influencing the clinical beam. In this study, the source components in which the secondary neutrons are produced during passive carbon-ion radiotherapy were identified and the method to reduce the secondary neutron dose effectively based on the identification of the main sources without influencing the clinical beam was investigated. A Monte Carlo study with the PHITS code was performed by assuming the beamline at the Heavy-Ion Medical Accelerator in Chiba (HIMAC). At first, the authors investigated the main sources of secondary neutrons in passive carbon-ion radiotherapy. Next, they investigated the reduction in the neutron dose with various modifications of the beamline device that is the most dominant in the neutron production. Finally, they investigated the use of an additional shield for the patient. It was shown that the main source is the secondary neutrons produced in the four-leaf collimator (FLC) used as a precollimator at HIAMC, of which contribution in the total neutron ambient dose equivalent is more than 70%. The investigations showed that the modification of the FLC can reduce the neutron dose at positions close to the beam axis by 70% and the FLC is very useful not only for the collimation of the primary beam but also the reduction in the secondary neutrons. Also, an additional shield for the patient is very effective to reduce the neutron dose at positions farther than 50 cm from the beam axis. Finally, they showed that the neutron dose can be reduced by approximately 70% at any position without influencing the primary beam used in treatment. This study was performed by assuming the HIMAC beamline; however, this study provides important information for reoptimizing the arrangement and the materials of beamline devices and designing a new facility for passive carbon-ion radiotherapy and probably passive proton radiotherapy.

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)

Deuteron nuclear data for the design of accelerator-based neutron sources: Measurement, model analysis, evaluation, and application

NASA Astrophysics Data System (ADS)

Watanabe, Yukinobu; Kin, Tadahiro; Araki, Shouhei; Nakayama, Shinsuke; Iwamoto, Osamu

2017-09-01

A comprehensive research program on deuteron nuclear data motivated by development of accelerator-based neutron sources is being executed. It is composed of measurements of neutron and gamma-ray yields and production cross sections, modelling of deuteron-induced reactions and code development, nuclear data evaluation and benchmark test, and its application to medical radioisotopes production. The goal of this program is to develop a state-of-the-art deuteron nuclear data library up to 200 MeV which will be useful for the design of future (d,xn) neutron sources. The current status and future plan are reviewed.

Neutron imaging with the short-pulse laser driven neutron source at the TRIDENT Laser Facility

DOE PAGES

Guler, Nevzat; Volegov, Petr Lvovich; Favalli, Andrea; ...

2016-10-17

Emerging approaches to short-pulse laser-driven neutron production offer a possible gateway to compact, low cost, and intense broad spectrum sources for a wide variety of applications. They are based on energetic ions, driven by an intense short-pulse laser, interacting with a converter material to produce neutrons via breakup and nuclear reactions. Recent experiments performed with the high-contrast laser at the Trident laser facility of Los Alamos National Laboratory have demonstrated a laser-driven ion acceleration mechanism operating in the regime of relativistic transparency, featuring a volumetric laser-plasma interaction. This mechanism is distinct from previously studied ones that accelerate ions at themore » laser-target surface. The Trident experiments produced an intense beam of deuterons with an energy distribution extending above 100 MeV. This deuteron beam, when directed at a beryllium converter, produces a forward-directed neutron beam with ~5x10 9 n/sr, in a single laser shot, primarily due to deuteron breakup. The neutron beam has a pulse duration on the order of a few nanoseconds with an energy distribution extending from a few hundreds of keV to almost 80 MeV. For the experiments on neutron-source spot-size measurements, our gated neutron imager was setup to select neutrons in the energy range of 2.5 to 35 MeV. The spot size of neutron emission at the converter was measured by two different imaging techniques, using a knife-edge and a penumbral aperture, in two different experimental campaigns. The neutron-source spot size is measured ~1 mm for both experiments. The measurements and analysis reported here give a spatial characterization for this type of neutron source for the first time. In addition, the forward modeling performed provides an empirical estimate of the spatial characteristics of the deuteron ion-beam. Finally, these experimental observations, taken together, provide essential yet unique data to benchmark and verify theoretical work into the basic acceleration mechanism, which remains an ongoing challenge.« less

Neutron imaging with the short-pulse laser driven neutron source at the TRIDENT Laser Facility

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

Guler, Nevzat; Volegov, Petr Lvovich; Favalli, Andrea

Emerging approaches to short-pulse laser-driven neutron production offer a possible gateway to compact, low cost, and intense broad spectrum sources for a wide variety of applications. They are based on energetic ions, driven by an intense short-pulse laser, interacting with a converter material to produce neutrons via breakup and nuclear reactions. Recent experiments performed with the high-contrast laser at the Trident laser facility of Los Alamos National Laboratory have demonstrated a laser-driven ion acceleration mechanism operating in the regime of relativistic transparency, featuring a volumetric laser-plasma interaction. This mechanism is distinct from previously studied ones that accelerate ions at themore » laser-target surface. The Trident experiments produced an intense beam of deuterons with an energy distribution extending above 100 MeV. This deuteron beam, when directed at a beryllium converter, produces a forward-directed neutron beam with ~5x10 9 n/sr, in a single laser shot, primarily due to deuteron breakup. The neutron beam has a pulse duration on the order of a few nanoseconds with an energy distribution extending from a few hundreds of keV to almost 80 MeV. For the experiments on neutron-source spot-size measurements, our gated neutron imager was setup to select neutrons in the energy range of 2.5 to 35 MeV. The spot size of neutron emission at the converter was measured by two different imaging techniques, using a knife-edge and a penumbral aperture, in two different experimental campaigns. The neutron-source spot size is measured ~1 mm for both experiments. The measurements and analysis reported here give a spatial characterization for this type of neutron source for the first time. In addition, the forward modeling performed provides an empirical estimate of the spatial characteristics of the deuteron ion-beam. Finally, these experimental observations, taken together, provide essential yet unique data to benchmark and verify theoretical work into the basic acceleration mechanism, which remains an ongoing challenge.« less

SU-G-IeP4-04: DD-Neutron Source Collimation for Neutron Stimulated Emission Computed Tomography: A Monte Carlo Simulation Study

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

Fong, G; Kapadia, A

Purpose: To optimize collimation and shielding for a deuterium-deuterium (DD) neutron generator for an inexpensive and compact clinical neutron imaging system. The envisioned application is cancer diagnosis through Neutron Stimulated Emission Computed Tomography (NSECT). Methods: Collimator designs were tested with an isotropic 2.5 MeV neutron source through GEANT4 simulations. The collimator is a 52×52×52 cm{sup 3} polyethylene block coupled with a 1 cm lead sheet in sequence. Composite opening was modeled into the collimator to permit passage of neutrons. The opening varied in shape (cylindrical vs. tapered), size (1–5 cm source-side and target-side openings) and aperture placements (13–39 cm frommore » source-side). Spatial and energy distribution of neutrons and gammas were tracked from each collimator design. Parameters analyzed were primary beam width (FWHM), divergence, and efficiency (percent transmission) for different configurations of the collimator. Select resultant outputs were then used for simulated NSECT imaging of a virtual breast phantom containing a 2.5 cm diameter tumor to assess the effect of the collimator on spatial resolution, noise, and scan time. Finally, composite shielding enclosure made of polyethylene and lead was designed and evaluated to block 99.99% of neutron and gamma radiation generated in the system. Results: Analysis of primary beam indicated the beam-width is linear to the aperture size. Increasing source-side opening allowed at least 20% more neutron throughput for all designs relative to the cylindrical openings. Maximum throughput for all designs was 364% relative to cylindrical openings. Conclusion: The work indicates potential for collimating and shielding a DD neutron generator for use in a clinical NSECT system. The proposed collimator designs produced a well-defined collimated neutron beam that can be used to image samples of interest with millimeter resolution. Balance in output efficiency, noise reduction, and scan time should be considered to determine the optimal design for specific NSECT applications.« less

Analysis and optimization of minor actinides transmutation blankets with regards to neutron and gamma sources

NASA Astrophysics Data System (ADS)

Kooymana, Timothée; Buiron, Laurent; Rimpault, Gérald

2017-09-01

Heterogeneous loading of minor actinides in radial blankets is a potential solution to implement minor actinides transmutation in fast reactors. However, to compensate for the lower flux level experienced by the blankets, the fraction of minor actinides to be loaded in the blankets must be increased to maintain acceptable performances. This severely increases the decay heat and neutron source of the blanket assemblies, both before and after irradiation, by more than an order of magnitude in the case of neutron source for instance. We propose here to implement an optimization methodology of the blankets design with regards to various parameters such as the local spectrum or the mass to be loaded, with the objective of minimizing the final neutron source of the spent assembly while maximizing the transmutation performances of the blankets. In a first stage, an analysis of the various contributors to long and short term neutron and gamma source is carried out while in a second stage, relevant estimators are designed for use in the effective optimization process, which is done in the last step. A comparison with core calculations is finally done for completeness and validation purposes. It is found that the use of a moderated spectrum in the blankets can be beneficial in terms of final neutron and gamma source without impacting minor actinides transmutation performances compared to more energetic spectrum that could be achieved using metallic fuel for instance. It is also confirmed that, if possible, the use of hydrides as moderating material in the blankets is a promising option to limit the total minor actinides inventory in the fuel cycle. If not, it appears that focus should be put upon an increased residence time for the blankets rather than an increase in the acceptable neutron source for handling and reprocessing.

Advancing Materials Science using Neutrons at Oak Ridge National Laboratory

ScienceCinema

Carpenter, John

2018-02-14

Jack Carpenter, pioneer of accelerator-based pulsed spallation neutron sources, talks about neutron science at Oak Ridge National Laboratory (ORNL) and a need for a second target station at the Spallation Neutron Source (SNS). ORNL is the Department of Energy's largest multiprogram science and energy laboratory, and is home to two scientific user facilities serving the neutron science research community: the High Flux Isotope Reactor (HFIR) and SNS. HFIR and SNS provide researchers with unmatched capabilities for understanding the structure and properties of materials, macromolecular and biological systems, and the fundamental physics of the neutron. Neutrons provide a window through which to view materials at a microscopic level that allow researchers to develop better materials and better products. Neutrons enable us to understand materials we use in everyday life. Carpenter explains the need for another station to produce long wavelength neutrons, or cold neutrons, to answer questions that are addressed only with cold neutrons. The second target station is optimized for that purpose. Modern technology depends more and more upon intimate atomic knowledge of materials, and neutrons are an ideal probe.

Observation of Neutron Skyshine from an Accelerator Based Neutron Source

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

Franklyn, C. B.

2011-12-13

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 >10{sup 11} n{center_dot}s{sup -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 ismore » 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.« less

The analysis of complex mixed-radiation fields using near real-time imaging.

PubMed

Beaumont, Jonathan; Mellor, Matthew P; Joyce, Malcolm J

2014-10-01

A new mixed-field imaging system has been constructed at Lancaster University using the principles of collimation and back projection to passively locate and assess sources of neutron and gamma-ray radiation. The system was set up at the University of Manchester where three radiation sources: (252)Cf, a lead-shielded (241)Am/Be and a (22)Na source were imaged. Real-time discrimination was used to find the respective components of the neutron and gamma-ray fields detected by a single EJ-301 liquid scintillator, allowing separate images of neutron and gamma-ray emitters to be formed. (252)Cf and (22)Na were successfully observed and located in the gamma-ray image; however, the (241)Am/Be was not seen owing to surrounding lead shielding. The (252)Cf and (241)Am/Be neutron sources were seen clearly in the neutron image, demonstrating the advantage of this mixed-field technique over a gamma-ray-only image where the (241)Am/Be source would have gone undetected. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The investigation of fast neutron Threshold Activation Detectors (TAD)

NASA Astrophysics Data System (ADS)

Gozani, T.; King, M. J.; Stevenson, J.

2012-02-01

The detection of fast neutrons is usually done by liquid hydrogenous organic scintillators, where the separation between the ever present gamma rays and neutrons is achieved by the pulse shape discrimination (PSD). In many practical situation the detection of fast neutrons has to be carried out while the intense source (be it neutrons, gamma rays or x-rays) that creates these neutrons, for example by the fission process, is present. This source, or ``flash'', usually blinds the neutron detectors and temporarily incapacitates them. By the time the detectors recover the prompt neutron signature does not exist. Thus to overcome the blinding background, one needs to search for processes whereby the desired signature, such as fission neutrons could in some way be measured long after the fission occurred and when the neutron detector is fully recovered from the overload. A new approach was proposed and demonstrated a good sensitivity for the detection of fast neutrons in adverse overload situations where normally it could not be done. A temporal separation of the fission event from the prompt neutrons detection is achieved via the activation process. The main idea, called Threshold Activation Detection (or detector)-TAD, is to find appropriate substances that can be selectively activated by the fission neutrons and not by the source radiation, and then measure the radioactively decaying activation products (typically beta and γ-rays) well after the source pulse has ended. The activation material should possess certain properties: a suitable half-life; an energy threshold below which the numerous source neutrons will not activate it (e.g. about 3 MeV); easily detectable activation products and has a usable cross section for the selected reaction. Ideally the substance would be part of the scintillator. There are several good candidates for TAD. The first one we have selected is based on fluorine. One of the major advantages of this element is the fact that it is a major constituent of available scintillators (e.g., BaF2, CaF2, hydrogen free liquid fluorocarbon). Thus the activation products of the fast prompt neutrons, in particular, the beta particles, can be measured with a very high efficiency in the detector. Other detectors and substances were investigated, such as 6Li and even common detectors such as NaI. The principles and experimental results obtained with F, NaI and 6Li based TAD are shown. The various contributing activation products are identified. The insensitivity of the fluorine based TAD to (d,D) neutrons is demonstrated. Ways and means to reduce or subtract the various neutron induced activations of NaI detector are elucidated along with its fast neutron detection capabilities. 6Li could also be a useful TAD.

SOURCE OF PRODUCTS OF NUCLEAR FISSION

DOEpatents

Harteck, P.; Dondes, S.

1960-03-15

A source of fission product recoil energy suitable for use in radiation chemistry is reported. The source consists of thermal neutron irradiated glass wool having a diameter of 1 to 5 microns and containing an isotope fissionable by thermal neutrons, such as U/sup 235/.

Fission meter

DOEpatents

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

2012-04-10

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.

KINETICS OF LOW SOURCE REACTOR STARTUPS. PART II

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

hurwitz, H. Jr.; MacMillan, D.B.; Smith, J.H.

1962-06-01

A computational technique is described for computation of the probability distribution of power level for a low source reactor startup. The technique uses a mathematical model, for the time-dependent probability distribution of neutron and precursor concentration, having finite neutron lifetime, one group of delayed neutron precursors, and no spatial dependence. Results obtained by the technique are given. (auth)

The neutronic design and performance of the Indiana University Cyclotron Facility (IUCF) Low Energy Neutron Source (LENS)

NASA Astrophysics Data System (ADS)

Lavelle, Christopher M.

Neutron scattering research is performed primarily at large-scale facilities. However, history has shown that smaller scale neutron scattering facilities can play a useful role in education and innovation while performing valuable materials research. This dissertation details the design and experimental validation of the LENS TMR as an example for a small scale accelerator driven neutron source. LENS achieves competitive long wavelength neutron intensities by employing a novel long pulse mode of operation, where the neutron production target is irradiated on a time scale comparable to the emission time of neutrons from the system. Monte Carlo methods have been employed to develop a design for optimal production of long wavelength neutrons from the 9Be(p,n) reaction at proton energies ranging from 7 to 13 MeV proton energy. The neutron spectrum was experimentally measured using time of flight, where it is found that the impact of the long pulse mode on energy resolution can be eliminated at sub-eV neutron energies if the emission time distribution of neutron from the system is known. The emission time distribution from the TMR system is measured using a time focussed crystal analyzer. Emission time of the fundamental cold neutron mode is found to be consistent with Monte Carlo results. The measured thermal neutron spectrum from the water reflector is found to be in agreement with Monte Carlo predictions if the scattering kernels employed are well established. It was found that the scattering kernels currently employed for cryogenic methane are inadequate for accurate prediction of the cold neutron intensity from the system. The TMR and neutronic modeling have been well characterized and the source design is flexible, such that it is possible for LENS to serve as an effective test bed for future work in neutronic development. Suggestions for improvements to the design that would allow increased neutron flux into the instruments are provided.

Total Ambient Dose Equivalent Buildup Factor Determination for Nbs04 Concrete.

PubMed

Duckic, Paulina; Hayes, Robert B

2018-06-01

Buildup factors are dimensionless multiplicative factors required by the point kernel method to account for scattered radiation through a shielding material. The accuracy of the point kernel method is strongly affected by the correspondence of analyzed parameters to experimental configurations, which is attempted to be simplified here. The point kernel method has not been found to have widespread practical use for neutron shielding calculations due to the complex neutron transport behavior through shielding materials (i.e. the variety of interaction mechanisms that neutrons may undergo while traversing the shield) as well as non-linear neutron total cross section energy dependence. In this work, total ambient dose buildup factors for NBS04 concrete are calculated in terms of neutron and secondary gamma ray transmission factors. The neutron and secondary gamma ray transmission factors are calculated using MCNP6™ code with updated cross sections. Both transmission factors and buildup factors are given in a tabulated form. Practical use of neutron transmission and buildup factors warrants rigorously calculated results with all associated uncertainties. In this work, sensitivity analysis of neutron transmission factors and total buildup factors with varying water content has been conducted. The analysis showed significant impact of varying water content in concrete on both neutron transmission factors and total buildup factors. Finally, support vector regression, a machine learning technique, has been engaged to make a model based on the calculated data for calculation of the buildup factors. The developed model can predict most of the data with 20% relative error.

NEUTRON MEASURING METHOD AND APPARATUS

DOEpatents

Seaborg, G.T.; Friedlander, G.; Gofman, J.W.

1958-07-29

A fast neutron fission detecting apparatus is described consisting of a source of fast neutrons, an ion chamber containing air, two electrodes within the ion chamber in confronting spaced relationship, a high voltage potential placed across the electrodes, a shield placed about the source, and a suitable pulse annplifier and recording system in the electrode circuit to record the impulse due to fissions in a sannple material. The sample material is coated onto the active surface of the disc electrode and shielding means of a material having high neutron capture capabilities for thermal neutrons are provided in the vicinity of the electrodes and about the ion chamber so as to absorb slow neutrons of thermal energy to effectively prevent their diffusing back to the sample and causing an error in the measurement of fast neutron fissions.

Localization and spectral isolation of special nuclear material using stochastic image reconstruction

NASA Astrophysics Data System (ADS)

Hamel, M. C.; Polack, J. K.; Poitrasson-Rivière, A.; Clarke, S. D.; Pozzi, S. A.

2017-01-01

In this work we present a technique for isolating the gamma-ray and neutron energy spectra from multiple radioactive sources localized in an image. Image reconstruction algorithms for radiation scatter cameras typically focus on improving image quality. However, with scatter cameras being developed for non-proliferation applications, there is a need for not only source localization but also source identification. This work outlines a modified stochastic origin ensembles algorithm that provides localized spectra for all pixels in the image. We demonstrated the technique by performing three experiments with a dual-particle imager that measured various gamma-ray and neutron sources simultaneously. We showed that we could isolate the peaks from 22Na and 137Cs and that the energy resolution is maintained in the isolated spectra. To evaluate the spectral isolation of neutrons, a 252Cf source and a PuBe source were measured simultaneously and the reconstruction showed that the isolated PuBe spectrum had a higher average energy and a greater fraction of neutrons at higher energies than the 252Cf. Finally, spectrum isolation was used for an experiment with weapons grade plutonium, 252Cf, and AmBe. The resulting neutron and gamma-ray spectra showed the expected characteristics that could then be used to identify the sources.

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.

The continued development of the Spallation Neutron Source external antenna H- ion sourcea)

NASA Astrophysics Data System (ADS)

Welton, R. F.; Carmichael, J.; Desai, N. J.; Fuga, R.; Goulding, R. H.; Han, B.; Kang, Y.; Lee, S. W.; Murray, S. N.; Pennisi, T.; Potter, K. G.; Santana, M.; Stockli, M. P.

2010-02-01

The U.S. Spallation Neutron Source (SNS) is an accelerator-based, pulsed neutron-scattering facility, currently in the process of ramping up neutron production. In order to ensure that the SNS will meet its operational commitments as well as provide for future facility upgrades with high reliability, we are developing a rf-driven, H- ion source based on a water-cooled, ceramic aluminum nitride (AlN) plasma chamber. To date, early versions of this source have delivered up to 42 mA to the SNS front end and unanalyzed beam currents up to ˜100 mA (60 Hz, 1 ms) to the ion source test stand. This source was operated on the SNS accelerator from February to April 2009 and produced ˜35 mA (beam current required by the ramp up plan) with availability of ˜97%. During this run several ion source failures identified reliability issues, which must be addressed before the source re-enters production: plasma ignition, antenna lifetime, magnet cooling, and cooling jacket integrity. This report discusses these issues, details proposed engineering solutions, and notes progress to date.

Neutron Imaging Development at China Academy of Engineering Physics (CAEP)

NASA Astrophysics Data System (ADS)

Li, Hang; Wang, Sheng; Cao, Chao; Huo, Heyong; Tang, Bin

Based the China Mianyang Research Reactor (CMRR) and D-T accelerator neutron source, thermal neutron, cold neutron and fast neutron imaging facilities are all installed at China Academy of Engineering Physics (CAEP). Various samples have been imaged by different energy neutrons and shown the neutron imaging application in industry, aerospace and so on. The facilities parameters and recent neutron imaging development will be shown in this paper.

Evaluation of neutron skyshine from a cyclotron

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

Huyashi, K.; Nakamura, T.

1984-06-01

The dose distribution and the spectrum variation of neutrons due to the skyshine effect have been measured with various detectors in the environment surrounding the cyclotron of the Institute for Nuclear Study, University of Tokyo. The source neutrons were produced by stopping a 52-MeV proton beam into a carbon beam stopper and were extracted upward from the opening in the concrete shield surrounding the cyclotron and then leaked into the atmosphere through the cyclotron building. The dose distribution and the spectrum of neutrons near the beam stopper were also measured in order to get information on the skyshine source. Themore » measured skyshine neutron spectra and dose distribution were analyzed with two codes, MMCR2 and SKYSHINE-II, with the result that the calculated results are in good agreement with the experiment. Valuable characteristics of this experiment are the determination of the energy spectrum and dose distribution of source neutron and the measurement of skyshine neutrons from an actual large-scale accelerator building to the exclusion of direct neutrons transported through the air. This experiment must be useful as a kind of benchmark experiment on the skyshine phenomenon.« less

X-rays from radio pulsars - The detection of PSR 1055-52

NASA Technical Reports Server (NTRS)

Cheng, A. F.; Helfand, D. J.

1983-01-01

The short-period pulsar PSR 1055-52 has been detected as a soft X-ray source in the course of an Einstein Observatory survey of radio pulsars. Its X-ray to radio luminosity ratio is about 10,000, although the X-rays are not modulated at the neutron star's rotation frequency. High spatial resolution observations suggest that a significant fraction of the emission comes from an extended region surrounding the pulsar. Several possible scenarios for the origin of both point and extended X-ray emission from isolated neutron stars are investigated: radiation from the hot stellar surface, from hot polar caps, and from an optically thick atmosphere, as well as from a circumstellar nebula emitting thermal bremsstrahlung or synchrotron radiation. It is concluded that the spatial, spectral, and temporal characteristics of this source are most consistent with a model in which relativistic particles generated by the pulsar are radiating synchrotron X-rays in the surrounding magnetic field; i.e., that PSR 1055 is embedded in a mini-Crab nebula. Observational tests of this hypothesis are suggested, and the implications of this result for pulsar evolution are briefly discussed.

Calibration of time of flight detectors using laser-driven neutron source

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

Mirfayzi, S. R.; Kar, S., E-mail: s.kar@qub.ac.uk; Ahmed, H.

2015-07-15

Calibration of three scintillators (EJ232Q, BC422Q, and EJ410) in a time-of-flight arrangement using a laser drive-neutron source is presented. The three plastic scintillator detectors were calibrated with gamma insensitive bubble detector spectrometers, which were absolutely calibrated over a wide range of neutron energies ranging from sub-MeV to 20 MeV. A typical set of data obtained simultaneously by the detectors is shown, measuring the neutron spectrum emitted from a petawatt laser irradiated thin foil.

Calibration of time of flight detectors using laser-driven neutron source.

PubMed

Mirfayzi, S R; Kar, S; Ahmed, H; Krygier, A G; Green, A; Alejo, A; Clarke, R; Freeman, R R; Fuchs, J; Jung, D; Kleinschmidt, A; Morrison, J T; Najmudin, Z; Nakamura, H; Norreys, P; Oliver, M; Roth, M; Vassura, L; Zepf, M; Borghesi, M

2015-07-01

Calibration of three scintillators (EJ232Q, BC422Q, and EJ410) in a time-of-flight arrangement using a laser drive-neutron source is presented. The three plastic scintillator detectors were calibrated with gamma insensitive bubble detector spectrometers, which were absolutely calibrated over a wide range of neutron energies ranging from sub-MeV to 20 MeV. A typical set of data obtained simultaneously by the detectors is shown, measuring the neutron spectrum emitted from a petawatt laser irradiated thin foil.

Calibration of time of flight detectors using laser-driven neutron source

NASA Astrophysics Data System (ADS)

Mirfayzi, S. R.; Kar, S.; Ahmed, H.; Krygier, A. G.; Green, A.; Alejo, A.; Clarke, R.; Freeman, R. R.; Fuchs, J.; Jung, D.; Kleinschmidt, A.; Morrison, J. T.; Najmudin, Z.; Nakamura, H.; Norreys, P.; Oliver, M.; Roth, M.; Vassura, L.; Zepf, M.; Borghesi, M.

2015-07-01

Calibration of three scintillators (EJ232Q, BC422Q, and EJ410) in a time-of-flight arrangement using a laser drive-neutron source is presented. The three plastic scintillator detectors were calibrated with gamma insensitive bubble detector spectrometers, which were absolutely calibrated over a wide range of neutron energies ranging from sub-MeV to 20 MeV. A typical set of data obtained simultaneously by the detectors is shown, measuring the neutron spectrum emitted from a petawatt laser irradiated thin foil.

Simulation and Analysis of Neutron Activation Risk for the IsoDAR High-Intensity Electron Antineutrino Source

NASA Astrophysics Data System (ADS)

Skuhersky, Michael

2013-04-01

IsoDAR (Isotope Decay-At-Rest) is a proposed high-intensity source of electron antineutrinos intended for use in searches for beyond standard model physics, the main analysis being a short baseline search for sterile neutrinos at a kiloton scale liquid scintillator detector. The source uses a compact cyclotron to deliver 600kW of protons at 60 MeV/nucleon in the form of H2^+ onto a Beryllium target which produces a large intermediate energy neutron flux. These neutrons thermalize and capture on a 99.9% pure ^7Li sleeve, which produces ^8Li at rest, which subsequently beta decays producing νe. Due to the high neutron fluxes, large duty factor, and low background environment surrounding the neutrino detector, we need to understand the activation risk and design a shield to minimize this risk allowing for the safe operation of the source. I will report on my neutron activation studies and the benchmarking of Geant4 for these applications.

Fast neutron counting in a mobile, trailer-based search platform

NASA Astrophysics Data System (ADS)

Hayward, Jason P.; Sparger, John; Fabris, Lorenzo; Newby, Robert J.

2017-12-01

Trailer-based search platforms for detection of radiological and nuclear threats are often based upon coded aperture gamma-ray imaging, because this method can be rendered insensitive to local variations in gamma background while still localizing the source well. Since gamma source emissions are rather easily shielded, in this work we consider the addition of fast neutron counting to a mobile platform for detection of sources containing Pu. A proof-of-concept system capable of combined gamma and neutron coded-aperture imaging was built inside of a trailer and used to detect a 252Cf source while driving along a roadway. Neutron detector types employed included EJ-309 in a detector plane and EJ-299-33 in a front mask plane. While the 252Cf gamma emissions were not readily detectable while driving by at 16.9 m standoff, the neutron emissions can be detected while moving. Mobile detection performance for this system and a scaled-up system design are presented, along with implications for threat sensing.

New generation high performance in situ polarized 3He system for time-of-flight beam at spallation sources.

PubMed

Jiang, C Y; Tong, X; Brown, D R; Glavic, A; Ambaye, H; Goyette, R; Hoffmann, M; Parizzi, A A; Robertson, L; Lauter, V

2017-02-01

Modern spallation neutron sources generate high intensity neutron beams with a broad wavelength band applied to exploring new nano- and meso-scale materials from a few atomic monolayers thick to complicated prototype device-like systems with multiple buried interfaces. The availability of high performance neutron polarizers and analyzers in neutron scattering experiments is vital for understanding magnetism in systems with novel functionalities. We report the development of a new generation of the in situ polarized 3 He neutron polarization analyzer for the Magnetism Reflectometer at the Spallation Neutron Source at Oak Ridge National Laboratory. With a new optical layout and laser system, the 3 He polarization reached and maintained 84% as compared to 76% in the first-generation system. The polarization improvement allows achieving the transmission function varying from 50% to 15% for the polarized neutron beam with the wavelength band of 2-9 Angstroms. This achievement brings a new class of experiments with optimal performance in sensitivity to very small magnetic moments in nano systems and opens up the horizon for its applications.

MTS-6 detectors calibration by using ²³⁹Pu-Be neutron source.

PubMed

Wrzesień, Małgorzata; Albiniak, Łukasz; Al-Hameed, Hiba

2017-10-17

Thermoluminescent detectors, type MTS-6, containing isotope ⁶Li (lithium) are sensitive in the range of thermal neutron energy; the ²³⁹Pu-Be (plutonium-and-beryllium) source emits neutrons in the energy range from 1 to 11 MeV. These seemingly contradictory elements may be combined by using the paraffin moderator, a determined density of thermal neutrons in the paraffin block and a conversion coefficient neutron flux to kerma, not forgetting the simultaneous registration of the photon radiation inseparable from the companion neutron radiation. The main aim of this work is to present the idea of calibration of thermoluminescent detectors that consist of a ⁶Li isotope, by using ²³⁹Pu-Be neutron radiation source. In this work, MTS-6 and MTS-7 thermoluminescent detectors and a plutonium-and-beryllium (²³⁹Pu-Be) neutron source were used. Paraffin wax fills the block, acting as a moderator. The calibration idea was based on the determination of dose equivalent rate based on the average kerma rate calculated taking into account the empirically determined function describing the density of thermal neutron flux in the paraffin block and a conversion coefficient neutron flux to kerma. The calculated value of the thermal neutron flux density was 1817.5 neutrons/cm²/s and the average value of kerma rate determined on this basis amounted to 244 μGy/h, and the dose equivalent rate 610 μSv/h. The calculated value allowed for the assessment of the length of time of exposure of the detectors directly in the paraffin block. The calibration coefficient for the used batch of detectors is (6.80±0.42)×10^-7 Sv/impulse. Med Pr 2017;68(6):705-710. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

Bioenvironmental Engineer’s Guide to Ionizing Radiation

DTIC Science & Technology

2005-10-01

mercury x-rays 186 (4 % ) - y Ra -226 radon x-rays Luminous Products, Neutron (tl/2: 1600 y) Alpha photons from daughters: Sources (w/ Be ) Rn-222, Po...Radioisotope Thermoelectric (t1,2: 88 y) Generators Pu-239 Alpha uranium x-rays Nuclear Weapons, Neutron (t1 /2: 2.4 x 104 y) Sources (w/ Be ...Calibration Am-241 .60 (36 %) - Static Eliminators, Chemical (h2: 432 y) Alpha n Agent Detectors, Neutron neptunium x-rays Sources (w/ Be ) 11 October 2005

High spatial resolution detection of low-energy electrons using an event-counting method, application to point projection microscopy

NASA Astrophysics Data System (ADS)

Salançon, Evelyne; Degiovanni, Alain; Lapena, Laurent; Morin, Roger

2018-04-01

An event-counting method using a two-microchannel plate stack in a low-energy electron point projection microscope is implemented. 15 μm detector spatial resolution, i.e., the distance between first-neighbor microchannels, is demonstrated. This leads to a 7 times better microscope resolution. Compared to previous work with neutrons [Tremsin et al., Nucl. Instrum. Methods Phys. Res., Sect. A 592, 374 (2008)], the large number of detection events achieved with electrons shows that the local response of the detector is mainly governed by the angle between the hexagonal structures of the two microchannel plates. Using this method in point projection microscopy offers the prospect of working with a greater source-object distance (350 nm instead of 50 nm), advancing toward atomic resolution.

Isotopic composition and neutronics of the Okelobondo natural reactor

NASA Astrophysics Data System (ADS)

Palenik, Christopher Samuel

The Oklo-Okelobondo and Bangombe uranium deposits, in Gabon, Africa host Earth's only known natural nuclear fission reactors. These 2 billion year old reactors represent a unique opportunity to study used nuclear fuel over geologic periods of time. The reactors in these deposits have been studied as a means by which to constrain the source term of fission product concentrations produced during reactor operation. The source term depends on the neutronic parameters, which include reactor operation duration, neutron flux and the neutron energy spectrum. Reactor operation has been modeled using a point-source computer simulation (Oak Ridge Isotope Generation and Depletion, ORIGEN, code) for a light water reactor. Model results have been constrained using secondary ionization mass spectroscopy (SIMS) isotopic measurements of the fission products Nd and Te, as well as U in uraninite from samples collected in the Okelobondo reactor zone. Based upon the constraints on the operating conditions, the pre-reactor concentrations of Nd (150 ppm +/- 75 ppm) and Te (<1 ppm) in uraninite were estimated. Related to the burnup measured in Okelobondo samples (0.7 to 13.8 GWd/MTU), the final fission product inventories of Nd (90 to 1200 ppm) and Te (10 to 110 ppm) were calculated. By the same means, the ranges of all other fission products and actinides produced during reactor operation were calculated as a function of burnup. These results provide a source term against which the present elemental and decay abundances at the fission reactor can be compared. Furthermore, they provide new insights into the extent to which a "fossil" nuclear reactor can be characterized on the basis of its isotopic signatures. In addition, results from the study of two other natural systems related to the radionuclide and fission product transport are included. A detailed mineralogical characterization of the uranyl mineralogy at the Bangombe uranium deposit in Gabon, Africa was completed to improve geochemical models of the solubility-limiting phase. A study of the competing effects of radiation damage and annealing in a U-bearing crystal of zircon shows that low temperature annealing in actinide-bearing phases is significant in the annealing of radiation damage.

Towards high-resolution neutron imaging on IMAT

NASA Astrophysics Data System (ADS)

Minniti, T.; Tremsin, A. S.; Vitucci, G.; Kockelmann, W.

2018-01-01

IMAT is a new cold-neutron imaging facility at the neutron spallation source ISIS at the Rutherford Appleton Laboratory, U.K.. The ISIS pulsed source enables energy-selective and energy-resolved neutron imaging via time-of-flight (TOF) techniques, which are available in addition to the white-beam neutron radiography and tomography options. A spatial resolution of about 50 μm for white-beam neutron radiography was achieved early in the IMAT commissioning phase. In this work we have made the first steps towards achieving higher spatial resolution. A white-beam radiography with 18 μm spatial resolution was achieved in this experiment. This result was possible by using the event counting neutron pixel detector based on micro-channel plates (MCP) coupled with a Timepix readout chip with 55 μm sized pixels, and by employing an event centroiding technique. The prospects for energy-selective neutron radiography for this centroiding mode are discussed.

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.

Study of different solutes for determination of neutron source strength based on the water bath

NASA Astrophysics Data System (ADS)

Khabaz, Rahim

2018-09-01

Time required for activation to saturation and background measurement is considered a limitation of strength determination of radionuclide neutron sources using manganese bath system (MBS). The objective of this research was to evaluate the other solutes based on water bath for presentation of the suitable replacement with MBS. With the aid Monte Carlo simulation, for three neutron sources, having different neutron spectra, immersed in six aqueous solutions, i.e., Na2SO4, VOSO4, MnSO4, Rh2(SO4)3, In2(SO4)3, I2O5, the correction factors in all nuclei of solutions for neutron losses with different process were obtained. The calculations results indicate that the Rh2(SO4)3 and VOSO4 are best options for replacing with MnSO4.

Using ISS Telescopes for Electromagnetic Follow-up of Gravitational Wave Detections of NS-NS and NS-BH Mergers

NASA Technical Reports Server (NTRS)

Camp, J.; Barthelmy, S.; Blackburn, L.; Carpenter, K. G.; Gehrels, N.; Kanner, J.; Marshall, F. E.; Racusin, J. L.; Sakamoto, T.

2013-01-01

The International Space Station offers a unique platform for rapid and inexpensive deployment of space telescopes. A scientific opportunity of great potential later this decade is the use of telescopes for the electromagnetic follow-up of ground-based gravitational wave detections of neutron star and black hole mergers. We describe this possibility for OpTIIX, an ISS technology demonstration of a 1.5 m diffraction limited optical telescope assembled in space, and ISS-Lobster, a wide-field imaging X-ray telescope now under study as a potential NASA mission. Both telescopes will be mounted on pointing platforms, allowing rapid positioning to the source of a gravitational wave event. Electromagnetic follow-up rates of several per year appear likely, offering a wealth of complementary science on the mergers of black holes and neutron stars.

Concept of DT fuel cycle for a fusion neutron source

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

Anan'ev, S.; Spitsyn, A.V.; Kuteev, B.V.

2015-03-15

A concept of DT-fusion neutron source (FNS) with the neutron yield higher than 10{sup 18} neutrons per second is under design in Russia. Such a FNS is of interest for many applications: 1) basic and applied research (neutron scattering, etc); 2) testing the structural materials for fusion reactors; 3) control of sub-critical nuclear systems and 4) nuclear waste processing (including transmutation of minor actinides). This paper describes the fuel cycle concept of a compact fusion neutron source based on a small spherical tokamak (FNS-ST) with a MW range of DT fusion power and considers the key physics issues of thismore » device. The major and minor radii are ∼0.5 and ∼0.3 m, magnetic field ∼1.5 T, heating power less than 15 MW and plasma current 1-2 MA. The system provides the fuel mixture with equal fractions of D and T (D:T = 1:1) for all FNS technology systems. (authors)« less

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.

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

Marleau, Peter; Reyna, David

In this work we investigate a method that confirms the operability of neutron detectors requiring neither radiological sources nor radiation-generating devices. This is desirable when radiological sources are not available, but confidence in the functionality of the instrument is required. The “source”, based on the production of neutrons in high-Z materials by muons, provides a tagged, low-background and consistent rate of neutrons that can be used to check the functionality of or calibrate a detector. Using a Monte Carlo guided optimization, an experimental apparatus was designed and built to evaluate the feasibility of this technique. Through a series of trialmore » measurements in a variety of locations we show that gated muon-induced neutrons appear to provide a consistent source of neutrons (35.9 ± 2.3 measured neutrons/10,000 muons in the instrument) under normal environmental variability (less than one statistical standard deviation for 10,000 muons) with a combined environmental + statistical uncertainty of ~18% for 10,000 muons. This is achieved in a single 21-22 minute measurement at sea level.« less

Experiment on search for neutron-antineutron oscillations using a projected UCN source at the WWR-M reactor

NASA Astrophysics Data System (ADS)

Fomin, A. K.; Serebrov, A. P.; Zherebtsov, O. M.; Leonova, E. N.; Chaikovskii, M. E.

2017-01-01

We propose an experiment on search for neutron-antineutron oscillations based on the storage of ultracold neutrons (UCN) in a material trap. The sensitivity of the experiment mostly depends on the trap size and the amount of UCN in it. In Petersburg Nuclear Physics Institute (PNPI) a high-intensity UCN source is projected at the WWR-M reactor, which must provide UCN density 2-3 orders of magnitude higher than existing sources. The results of simulations of the designed experimental scheme show that the sensitivity can be increased by ˜ 10-40 times compared to sensitivity of previous experiment depending on the model of neutron reflection from walls.

On three-dimensional reconstruction of a neutron/x-ray source from very few two-dimensional projections

DOE PAGES

Volegov, P. L.; Danly, C. R.; Merrill, F. E.; ...

2015-11-24

The neutron imaging system at the National Ignition Facility is an important diagnostic tool for measuring the two-dimensional size and shape of the source of neutrons produced in the burning deuterium-tritium plasma during the stagnation phase of inertial confinement fusion implosions. Few two-dimensional projections of neutronimages are available to reconstruct the three-dimensionalneutron source. In our paper, we present a technique that has been developed for the 3Dreconstruction of neutron and x-raysources from a minimal number of 2D projections. Here, we present the detailed algorithms used for this characterization and the results of reconstructedsources from experimental data collected at Omega.

Neutron reflecting supermirror structure

DOEpatents

Wood, J.L.

1992-12-01

An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources. 2 figs.

Neutron reflecting supermirror structure

DOEpatents

Wood, James L.

1992-01-01

An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources.

Neutron spectroscopy with scintillation detectors using wavelets

NASA Astrophysics Data System (ADS)

Hartman, Jessica

The purpose of this research was to study neutron spectroscopy using the EJ-299-33A plastic scintillator. This scintillator material provided a novel means of detection for fast neutrons, without the disadvantages of traditional liquid scintillation materials. EJ-299-33A provided a more durable option to these materials, making it less likely to be damaged during handling. Unlike liquid scintillators, this plastic scintillator was manufactured from a non-toxic material, making it safer to use, as well as easier to design detectors. The material was also manufactured with inherent pulse shape discrimination abilities, making it suitable for use in neutron detection. The neutron spectral unfolding technique was developed in two stages. Initial detector response function modeling was carried out through the use of the MCNPX Monte Carlo code. The response functions were developed for a monoenergetic neutron flux. Wavelets were then applied to smooth the response function. The spectral unfolding technique was applied through polynomial fitting and optimization techniques in MATLAB. Verification of the unfolding technique was carried out through the use of experimentally determined response functions. These were measured on the neutron source based on the Van de Graff accelerator at the University of Kentucky. This machine provided a range of monoenergetic neutron beams between 0.1 MeV and 24 MeV, making it possible to measure the set of response functions of the EJ-299-33A plastic scintillator detector to neutrons of specific energies. The response of a plutonium-beryllium (PuBe) source was measured using the source available at the University of Nevada, Las Vegas. The neutron spectrum reconstruction was carried out using the experimentally measured response functions. Experimental data was collected in the list mode of the waveform digitizer. Post processing of this data focused on the pulse shape discrimination analysis of the recorded response functions to remove the effects of photons and allow for source characterization based solely on the neutron response. The unfolding technique was performed through polynomial fitting and optimization techniques in MATLAB, and provided an energy spectrum for the PuBe source.

Neutron monitoring and electrode calorimetry experiments in the HIP-1 Hot Ion Plasma

NASA Technical Reports Server (NTRS)

Reinmann, J. J.; Layman, R. W.

1977-01-01

Results are presented for two diagnostic procedures on HIP-1: neutron diagnostics to determine where neutrons originated within the plasma discharge chamber and electrode calorimetry to measure the steady-state power absorbed by the two anodes and cathodes. Results are also reported for a hot-ion plasma formed with a continuous-cathode rod, one that spans the full length of the test section, in place of the two hollow cathodes. The outboard neutron source strength increased relative to that at the midplane when (1) the cathode tips were moved farther outboard, (2) the anode diameters were increased, and (3) one of the anodes was removed. The distribution of neutron sources within the plasma discharge chamber was insensitive to the division of current between the two cathodes. For the continuous cathode, increasing the discharge current increased the midplane neutron source strength relative to the outboard source strength. Each cathode absorbed from 12 to 15 percent of the input power regardless of the division of current between the cathodes. The anodes absorbed from 20 to 40 percent of the input power. The division of power absorption between the anodes varied with plasma operating conditions and electrode placement.

Photonuclear Contributions to SNS Pulse Shapes

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

McClanahan, Tucker C.; Iverson, Erik B.; Gallmeier, Franz X.

Short-pulsed sources like the Spallation Neutron Source (SNS) and ISIS produce bursts of neutron pulses at rates of 10-60 Hz, with sub-microsecond proton pulses impacting on high-Z target materials. Moderators are grouped around the target to receive the fast neutrons generated from spallation reactions to moderate them effciently to thermal and sub-thermal energies and to feed narrow neutron pulses to neutron scattering instruments. The scattering instruments use the neutrons as a probe for material investigations, and make use of time-of-flight (TOF) methods for resolving the neutron energy. The energy resolution of scattering instruments depends on the narrow time-structure of themore » neutron pulses, while neutrons in the long tail of the emission time distributions can degrade the instrument performance and add undesired background to measurements. The SNS neutronics team is investigating a possible source term impacting the background at short-pulsed spallation sources. The ISIS TS2 project claims to have significantly reduced neutron scattering instrument background levels by the elimination or reduction of iron shielding in the target-moderator-reflector assembly. An alternative hypothesis, also proposed by ISIS, suggests that this apparent reduction arises from moving beamline shielding away from the neutron guide channels, reducing albedo down the beamlines. In both hypotheses, the background neutrons in question are believed to be generated by photonuclear reactions. If the background neutrons are indeed generated via photonuclear channels, then they are generated in a time-dependent fashion, since most of the high-energy photons capable of inducing photonuclear production are gone within a few microseconds following the proton pulse. To evaluate this e ect, we have enabled photonuclear reactions in a series of studies for the SNS first target station (FTS) taking advantage of its Monte Carlo model. Using a mixture of ENDF/B VII.0 and TENDL-2014 photonuclear cross sections available and the CEM03 physics model within MCNPX 2.6.0 in the simulation, we are able to estimate the impact of photoneutron production on both overall neutron production and delayed neutron production. We find that a significant number of photon-induced neutrons are produced a few milliseconds after the proton pulse, following prompt gamma emission through the capture of neutrons in the slowing-down and thermalization processes. We name these "slowing-down delayed neutrons" to distinguish them from either "activation-delayed neutrons" or "beta-delayed neutrons." The beta-delayed and activation-delayed neutrons were not part of this study, and will be addressed elsewhere. While these other delayed neutron channels result in the time-independent (constant) production of fast neutrons outside of the prompt pulse, the slowing-down delayed neutrons also a ect the shape of the pulses. Although numerically insignificant in most cases, we describe a set of scenarios related to T0-chopper operation in which the slowing-down delayed neutrons may be important.« less

Raw neutron scattering data for strain measurement of hydraulically loaded granite and marble samples in triaxial stress state

DOE Data Explorer

Polsky, Yarom

2014-05-23

This entry contains raw data files from experiments performed on the Vulcan beamline at the Spallation Neutron Source at Oak Ridge National Laboratory using a pressure cell. Cylindrical granite and marble samples were subjected to confining pressures of either 0 psi or approximately 2500 psi and internal pressures of either 0 psi, 1500 psi or 2500 psi through a blind axial hole at the center of one end of the sample. The sample diameters were 1.5" and the sample lengths were 6". The blind hole was 0.25" in diameter and 3" deep. One set of experiments measured strains at points located circumferentially around the center of the sample with identical radii to determine if there was strain variability (this would not be expected for a homogeneous material based on the symmetry of loading). Another set of experiments measured load variation across the radius of the sample at a fixed axial and circumferential location. Raw neutron diffraction intensity files and experimental parameter descriptions are included.

Growing Larger Crystals for Neutron Diffraction

NASA Technical Reports Server (NTRS)

Pusey, Marc

2003-01-01

Obtaining crystals of suitable size and high quality has been a major bottleneck in macromolecular crystallography. With the advent of advanced X-ray sources and methods the question of size has rapidly dwindled, almost to the point where if one can see the crystal then it was big enough. Quality is another issue, and major national and commercial efforts were established to take advantage of the microgravity environment in an effort to obtain higher quality crystals. Studies of the macromolecule crystallization process were carried out in many labs in an effort to understand what affected the resultant crystal quality on Earth, and how microgravity improved the process. While technological improvements are resulting in a diminishing of the minimum crystal size required, neutron diffraction structural studies still require considerably larger crystals, by several orders of magnitude, than X-ray studies. From a crystal growth physics perspective there is no reason why these 'large' crystals cannot be obtained: the question is generally more one of supply than limitations mechanism. This talk will discuss our laboratory s current model for macromolecule crystal growth, with highlights pertaining to the growth of crystals suitable for neutron diffraction studies.

Optimal moderator materials at various proton energies considering photon dose rate after irradiation for an accelerator-driven ⁹Be(p, n) boron neutron capture therapy neutron source.

PubMed

Hashimoto, Y; Hiraga, F; Kiyanagi, Y

2015-12-01

We evaluated the accelerator beam power and the neutron-induced radioactivity of (9)Be(p, n) boron neutron capture therapy (BNCT) neutron sources having a MgF2, CaF2, or AlF3 moderator and driven by protons with energy from 8 MeV to 30 MeV. The optimal moderator materials were found to be MgF2 for proton energies less than 10 MeV because of lower required accelerator beam power and CaF2 for higher proton energies because of lower photon dose rate at the treatment position after neutron irradiation. Copyright © 2015 Elsevier Ltd. All rights reserved.

A 23-GROUP NEUTRON THERMALIZATION CROSS SECTION LIBRARY

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

Doctor, R.D.; Boling, M.A.

1963-07-15

A set of 23-group neutron cross sections for use in the calculation of neutron thermalization and thermal neutron spectral effects in SNAP reactors is compiled. The sources and methods used to obtain the cross sections are described. (auth)

SKYSINE-II procedure: calculation of the effects of structure design on neutron, primary gamma-ray and secondary gamma-ray dose rates in air

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

Lampley, C.M.

1979-01-01

An updated version of the SKYSHINE Monte Carlo procedure has been developed. The new computer code, SKYSHINE-II, provides a substantial increase in versatility in that the program possesses the ability to address three types of point-isotropic radiation sources: (1) primary gamma rays, (2) neutrons, and (3) secondary gamma rays. In addition, the emitted radiation may now be characterized by an energy emission spectrum product of a new energy-dependent atmospheric transmission data base developed by Radiation Research Associates, Inc. for each of the three source types described above. Most of the computational options present in the original program have been retainedmore » in the new version. Hence, the SKYSHINE-II computer code provides a versatile and viable tool for the analysis of the radiation environment in the vicinity of a building structure containing radiation sources, situated within the confines of a nuclear power plant. This report describes many of the calculational methods employed within the SKYSHINE-II program. A brief description of the new data base is included. Utilization instructions for the program are provided for operation of the SKYSHINE-II code on the Brookhaven National Laboratory Central Scientific Computing Facility. A listing of the source decks, block data routines, and the new atmospheric transmission data base are provided in the appendices of the report.« 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

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

The high-resolution time-of-flight spectrometer TOFTOF

NASA Astrophysics Data System (ADS)

Unruh, Tobias; Neuhaus, Jürgen; Petry, Winfried

2007-10-01

The TOFTOF spectrometer is a multi-disc chopper time-of-flight spectrometer for cold neutrons at the research neutron source Heinz Maier-Leibnitz (FRM II). After five reactor cycles of routine operation the characteristics of the instrument are reported in this article. The spectrometer features an excellent signal to background ratio due to its remote position in the neutron guide hall, an elaborated shielding concept and an s-shaped curved primary neutron guide which acts i.a. as a neutron velocity filter. The spectrometer is fed with neutrons from the undermoderated cold neutron source of the FRM II leading to a total neutron flux of ˜1010n/cm2/s in the continuous white beam at the sample position distributed over a continuous and particularly broad wavelength spectrum. A high energy resolution is achieved by the use of high speed chopper discs made of carbon-fiber-reinforced plastic. In the combination of intensity, resolution and signal to background ratio the spectrometer offers new scientific prospects in the fields of inelastic and quasielastic neutron scattering.

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

Development of time projection chamber for precise neutron lifetime measurement using pulsed cold neutron beams

NASA Astrophysics Data System (ADS)

Arimoto, Y.; Higashi, N.; Igarashi, Y.; Iwashita, Y.; Ino, T.; Katayama, R.; Kitaguchi, M.; Kitahara, R.; Matsumura, H.; Mishima, K.; Nagakura, N.; Oide, H.; Otono, H.; Sakakibara, R.; Shima, T.; Shimizu, H. M.; Sugino, T.; Sumi, N.; Sumino, H.; Taketani, K.; Tanaka, G.; Tanaka, M.; Tauchi, K.; Toyoda, A.; Tomita, T.; Yamada, T.; Yamashita, S.; Yokoyama, H.; Yoshioka, T.

2015-11-01

A new time projection chamber (TPC) was developed for neutron lifetime measurement using a pulsed cold neutron spallation source at the Japan Proton Accelerator Research Complex (J-PARC). Managing considerable background events from natural sources and the beam radioactivity is a challenging aspect of this measurement. To overcome this problem, the developed TPC has unprecedented features such as the use of polyether-ether-ketone plates in the support structure and internal surfaces covered with 6Li-enriched tiles to absorb outlier neutrons. In this paper, the design and performance of the new TPC are reported in detail.

DETERMINATION OF SPECIFIC NEUTRONIC REACTIVITY

DOEpatents

Dessauer, G.

1960-05-10

A method is given for production-line determination of the specific neutronic reactivity of such objects as individual nuclear fuel or neutron absorber elements and is notable for rapidity and apparatus simplicity. The object is incorporated in a slightly sub-critical chain fission reactive assembly having a discrete neutron source, thereby establishing a K/sub eff/ within the crucial range of 0.95 to 0.995. The range was found to afford, uniquely, flux- transient damped response in a niatter of seconds simultaneously with acceptable analytical sensitivity. The resulting neutron flux measured at a situs spaced from both object and source within the assembly serves as a calibrable indication of said reactivity.

Gadolinium-doped water cerenkov-based neutron and high energy gamma-ray detector and radiation portal monitoring system

DOEpatents

Dazeley, Steven A; Svoboda, Robert C; Bernstein, Adam; Bowden, Nathaniel

2013-02-12

A water Cerenkov-based neutron and high energy gamma ray detector and radiation portal monitoring system using water doped with a Gadolinium (Gd)-based compound as the Cerenkov radiator. An optically opaque enclosure is provided surrounding a detection chamber filled with the Cerenkov radiator, and photomultipliers are optically connected to the detect Cerenkov radiation generated by the Cerenkov radiator from incident high energy gamma rays or gamma rays induced by neutron capture on the Gd of incident neutrons from a fission source. The PMT signals are then used to determine time correlations indicative of neutron multiplicity events characteristic of a fission source.

Construction of 144, 565 keV and 5.0 MeV monoenergetic neutron calibration fields at JAERI.

PubMed

Tanimura, Y; Yoshizawa, M; Saegusa, J; Fujii, K; Shimizu, S; Yoshida, M; Shibata, Y; Uritani, A; Kudo, K

2004-01-01

Monoenergetic neutron calibration fields of 144, 565 keV and 5.0 MeV have been developed at the Facility of Radiation Standards of JAERI using a 4 MV Pelletron accelerator. The 7Li(p,n)7Be and 2H(d,n)3He reactions are employed for neutron production. The neutron energy was measured by the time-of-flight method with a liquid scintillation detector and calculated with the MCNP-ANT code. A long counter is employed as a neutron monitor because of the flat response. The monitor is set up where the influence of inscattered neutrons from devices and their supporting materials at a calibration point is as small as possible. The calibration coefficients from the monitor counts to the neutron fluence at a calibration point were obtained from the reference fluence measured with the transfer instrument of the primary standard laboratory (AIST), a 24.13 cm phi Bonner sphere counter. The traceability of the fields to AIST was established through the calibration.

Evaluation of two-stage system for neutron measurement aiming at increase in count rate at Japan Atomic Energy Agency-Fusion Neutronics Source

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

Shinohara, K., E-mail: shinohara.koji@jaea.go.jp; Ochiai, K.; Sukegawa, A.

In order to increase the count rate capability of a neutron detection system as a whole, we propose a multi-stage neutron detection system. Experiments to test the effectiveness of this concept were carried out on Fusion Neutronics Source. Comparing four configurations of alignment, it was found that the influence of an anterior stage on a posterior stage was negligible for the pulse height distribution. The two-stage system using 25 mm thickness scintillator was about 1.65 times the count rate capability of a single detector system for d-D neutrons and was about 1.8 times the count rate capability for d-T neutrons.more » The results suggested that the concept of a multi-stage detection system will work in practice.« less

Generation of nanosecond neutron pulses in vacuum accelerating tubes

NASA Astrophysics Data System (ADS)

Didenko, A. N.; Shikanov, A. E.; Rashchikov, V. I.; Ryzhkov, V. I.; Shatokhin, V. L.

2014-06-01

The generation of neutron pulses with a duration of 1-100 ns using small vacuum accelerating tubes is considered. Two physical models of acceleration of short deuteron bunches in pulse neutron generators are described. The dependences of an instantaneous neutron flux in accelerating tubes on the parameters of pulse neutron generators are obtained using computer simulation. The results of experimental investigation of short-pulse neutron generators based on the accelerating tube with a vacuum-arc deuteron source, connected in the circuit with a discharge peaker, and an accelerating tube with a laser deuteron source, connected according to the Arkad'ev-Marx circuit, are given. In the experiments, the neutron yield per pulse reached 107 for a pulse duration of 10-100 ns. The resultant experimental data are in satisfactory agreement with the results of computer simulation.

Experimental determination of neutron lifetimes through macroscopic neutron noise in the IPEN/MB-01 reactor

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

Gonnelli, Eduardo; Diniz, Ricardo

2013-05-06

The neutron lifetimes of the core, reflector, and global were experimentally obtained through macroscopic neutron noise in the IPEN/MB-01 reactor for five levels of subcriticality. The theoretical Auto Power Spectral Densities were derived by point kinetic equations taking the reflector effect into account, and one of the approaches consider an additional group of delayed neutrons.

New developments in the McStas neutron instrument simulation package

NASA Astrophysics Data System (ADS)

Willendrup, P. K.; Knudsen, E. B.; Klinkby, E.; Nielsen, T.; Farhi, E.; Filges, U.; Lefmann, K.

2014-07-01

The McStas neutron ray-tracing software package is a versatile tool for building accurate simulators of neutron scattering instruments at reactors, short- and long-pulsed spallation sources such as the European Spallation Source. McStas is extensively used for design and optimization of instruments, virtual experiments, data analysis and user training. McStas was founded as a scientific, open-source collaborative code in 1997. This contribution presents the project at its current state and gives an overview of the main new developments in McStas 2.0 (December 2012) and McStas 2.1 (expected fall 2013), including many new components, component parameter uniformisation, partial loss of backward compatibility, updated source brilliance descriptions, developments toward new tools and user interfaces, web interfaces and a new method for estimating beam losses and background from neutron optics.

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.

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

Evidence of nuclear fusion neutrons in an extremely small plasma focus device operating at 0.1 Joules

NASA Astrophysics Data System (ADS)

Soto, Leopoldo; Pavéz, Cristián; Moreno, José; Altamirano, Luis; Huerta, Luis; Barbaglia, Mario; Clausse, Alejandro; Mayer, Roberto E.

2017-08-01

We report on D-D fusion neutron emission in a plasma device with an energy input of only 0.1 J, within a range where fusion events have been considered very improbable. The results presented here are the consequence of scaling rules we have derived, thus being the key point to assure the same energy density plasma in smaller devices than in large machines. The Nanofocus (NF)—our device—was designed and constructed at the P4 Lab of the Chilean Nuclear Energy Commission. Two sets of independent measurements, with different instrumentation, were made at two laboratories, in Chile and Argentina. The neutron events observed are 20σ greater than the background. The NF plasma is produced from a pulsed electrical discharge using a submillimetric anode, in a deuterium atmosphere, showing empirically that it is, in fact, possible to heat and compress the plasma. The strong evidence presented here stretches the limits beyond what was expected. A thorough understanding of this could possibly tell us where the theoretical limits actually lie, beyond conjectures. Notwithstanding, a window is thus open for low cost endeavours for basic fusion research. In addition, the development of small, portable, safe nonradioactive neutron sources becomes a feasible issue.

Fast neutron imaging device and method

DOEpatents

Popov, Vladimir; Degtiarenko, Pavel; Musatov, Igor V.

2014-02-11

A fast neutron imaging apparatus and method of constructing fast neutron radiography images, the apparatus including a neutron source and a detector that provides event-by-event acquisition of position and energy deposition, and optionally timing and pulse shape for each individual neutron event detected by the detector. The method for constructing fast neutron radiography images utilizes the apparatus of the invention.

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

Trahan, Alexis Chanel

The objectives of this presentation are to introduce the basic physics of neutron production, interactions and detection; identify the processes that generate neutrons; explain the most common neutron mechanism, spontaneous and induced fission and (a,n) reactions; describe the properties of neutron from different sources; recognize advantages of neutron measurements techniques; recognize common neutrons interactions; explain neutron cross section measurements; describe the fundamental of 3He detector function and designs; and differentiate between passive and active assay techniques.

Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

DOE PAGES

Borges, Nicholas; Losko, Adrian; Vogel, Sven

2018-02-13

The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI) with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. In this work, we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolvedmore » neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 μm pixel size of the detector used for this study, we found a resolution improvement from ~80 μm to ~22 μm using pixel centroiding while fully preserving the energy resolution.« less

Event Centroiding Applied to Energy-Resolved Neutron Imaging at LANSCE

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

Borges, Nicholas; Losko, Adrian; Vogel, Sven

The energy-dependence of the neutron cross section provides vastly different contrast mechanisms than polychromatic neutron radiography if neutron energies can be selected for imaging applications. In recent years, energy-resolved neutron imaging (ERNI) with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as for quantitative density measurements, was pioneered at the Flight Path 5 beam line at LANSCE and continues to be refined. In this work, we present event centroiding, i.e., the determination of the center-of-gravity of a detection event on an imaging detector to allow sub-pixel spatial resolution and apply it to the many frames collected for energy-resolvedmore » neutron imaging at a pulsed neutron source. While event centroiding was demonstrated at thermal neutron sources, it has not been applied to energy-resolved neutron imaging, where the energy resolution requires to be preserved, and we present a quantification of the possible resolution as a function of neutron energy. For the 55 μm pixel size of the detector used for this study, we found a resolution improvement from ~80 μm to ~22 μm using pixel centroiding while fully preserving the energy resolution.« less

New generation non-stationary portable neutron generators for biophysical applications of Neutron Activation Analysis.

PubMed

Marchese, N; Cannuli, A; Caccamo, M T; Pace, C

2017-01-01

Neutron sources are increasingly employed in a wide range of research fields. For some specific purposes an alternative to existing large-scale neutron scattering facilities, can be offered by the new generation of portable neutron devices. This review reports an overview for such recently available neutron generators mainly addressed to biophysics applications with specific reference to portable non-stationary neutron generators applied in Neutron Activation Analysis (NAA). The review reports a description of a typical portable neutron generator set-up addressed to biophysics applications. New generation portable neutron devices, for some specific applications, can constitute an alternative to existing large-scale neutron scattering facilities. Deuterium-Deuterium pulsed neutron sources able to generate 2.5MeV neutrons, with a neutron yield of 1.0×10 6 n/s, a pulse rate of 250Hz to 20kHz and a duty factor varying from 5% to 100%, when combined with solid-state photon detectors, show that this kind of compact devices allow rapid and user-friendly elemental analysis. "This article is part of a Special Issue entitled "Science for Life" Guest Editor: Dr. Austen Angell, Dr. Salvatore Magazù and Dr. Federica Migliardo". Copyright © 2016 Elsevier B.V. All rights reserved.

Developing and Characterizing X-Ray Concentrators for Space-Based Observations with the Neutron Star Interior Composition Explorer

NASA Astrophysics Data System (ADS)

Balsamo, Erin Rose

A long standing need to resolve the equation of state (EOS) of neutron stars motivated the Neutron Star Interior Composition Explorer's (NICER) mission goals, including determining stellar radii to within +/-5%. This can be accomplished by observing the change in photon flux over time from pulsars (rotating neutron stars with a magnetic field) in the soft X-ray energy band (0.2-12.0 keV) using NICER's highly effective photon focusing system comprised of 56 X-ray concentrators (XRC). In this thesis, I prove the efficiency and functionally of the specialized fabrication process which allowed for the success of producing flight ready XRCs in a cost effective manner, which have been shown to exceed mission requirements through ground calibration. I have also conducted simulations of a challenging yet advantageous observation of the closest millisecond pulsar (MSP) which will provide astronomers with useful NICER data to further constrain the EOS. X-rays are focused by grazing incident reflection with incident angles on the order of a degree. The NICER optics were designed as singly-reflecting concentrators with a curved axial profile for improved photon concentration and a sturdy full shell structure for enhanced module stability. I assisted in developing a new substrate forming technique to accommodate these unique design elements. By analyzing hundreds of substrates' profiles post-forming, I found the profiles were copied, on average, to within 4.6% +/- 3.7%, i.e. with >95% accuracy. My ground calibration results and this analysis has shown that the heat shrink tape method is reliable, repeatable, and could be used in future missions to increase production rate and performance. NICER's 6 arcminute field-of-view poses a challenge in resolving the energy spectra and light curves of the closest MSP, PSR J0437-4715, due to the bright nearby X-ray source, the Active Galactic Nucleus (AGN) RX J0437.4-4711, with an angular distance of 4.2 arcmintues from the pulsar. Since the optics function as concentrators, all image resolution is lost. However, due to the energy dependency of the XRC's point spread function (PSF), I have found that the best way to observe the MSP is to point the instrument 2.7 arcmintues off-axis from the pulsar, away from the AGN; the pulsar to AGN flux is maximized at this point. Within the simulations, I carefully consider the multi-dimensional instrument pointing statistics, calibrated XRC PSFs, and a current theory of neutron star emission processes.

Measurement of the absolute neutron beam polarization from a supermirror polarizer and the absolute efficiency of a neutron spin rotator for the NPDGamma experiment using a polarized 3He neutron spin-filter

NASA Astrophysics Data System (ADS)

Musgrave, M. M.; Baeßler, S.; Balascuta, S.; Barrón-Palos, L.; Blyth, D.; Bowman, J. D.; Chupp, T. E.; Cianciolo, V.; Crawford, C.; Craycraft, K.; Fomin, N.; Fry, J.; Gericke, M.; Gillis, R. C.; Grammer, K.; Greene, G. L.; Hamblen, J.; Hayes, C.; Huffman, P.; Jiang, C.; Kucuker, S.; McCrea, M.; Mueller, P. E.; Penttilä, S. I.; Snow, W. M.; Tang, E.; Tang, Z.; Tong, X.; Wilburn, W. S.

2018-07-01

Accurately measuring the neutron beam polarization of a high flux, large area neutron beam is necessary for many neutron physics experiments. The Fundamental Neutron Physics Beamline (FnPB) at the Spallation Neutron Source (SNS) is a pulsed neutron beam that was polarized with a supermirror polarizer for the NPDGamma experiment. The polarized neutron beam had a flux of ∼ 109 neutrons per second per cm2 and a cross sectional area of 10 × 12 cm2. The polarization of this neutron beam and the efficiency of a RF neutron spin rotator installed downstream on this beam were measured by neutron transmission through a polarized 3He neutron spin-filter. The pulsed nature of the SNS enabled us to employ an absolute measurement technique for both quantities which does not depend on accurate knowledge of the phase space of the neutron beam or the 3He polarization in the spin filter and is therefore of interest for any experiments on slow neutron beams from pulsed neutron sources which require knowledge of the absolute value of the neutron polarization. The polarization and spin-reversal efficiency measured in this work were done for the NPDGamma experiment, which measures the parity violating γ-ray angular distribution asymmetry with respect to the neutron spin direction in the capture of polarized neutrons on protons. The experimental technique, results, systematic effects, and applications to neutron capture targets are discussed.

Monte Carlo study on secondary neutrons in passive carbon-ion radiotherapy: Identification of the main source and reduction in the secondary neutron dose

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

Yonai, Shunsuke; Matsufuji, Naruhiro; Kanai, Tatsuaki

Purpose: Recent successful results in passive carbon-ion radiotherapy allow the patient to live for a longer time and allow younger patients to receive the radiotherapy. Undesired radiation exposure in normal tissues far from the target volume is considerably lower than that close to the treatment target, but it is considered to be non-negligible in the estimation of the secondary cancer risk. Therefore, it is very important to reduce the undesired secondary neutron exposure in passive carbon-ion radiotherapy without influencing the clinical beam. In this study, the source components in which the secondary neutrons are produced during passive carbon-ion radiotherapy weremore » identified and the method to reduce the secondary neutron dose effectively based on the identification of the main sources without influencing the clinical beam was investigated. Methods: A Monte Carlo study with the PHITS code was performed by assuming the beamline at the Heavy-Ion Medical Accelerator in Chiba (HIMAC). At first, the authors investigated the main sources of secondary neutrons in passive carbon-ion radiotherapy. Next, they investigated the reduction in the neutron dose with various modifications of the beamline device that is the most dominant in the neutron production. Finally, they investigated the use of an additional shield for the patient. Results: It was shown that the main source is the secondary neutrons produced in the four-leaf collimator (FLC) used as a precollimator at HIAMC, of which contribution in the total neutron ambient dose equivalent is more than 70%. The investigations showed that the modification of the FLC can reduce the neutron dose at positions close to the beam axis by 70% and the FLC is very useful not only for the collimation of the primary beam but also the reduction in the secondary neutrons. Also, an additional shield for the patient is very effective to reduce the neutron dose at positions farther than 50 cm from the beam axis. Finally, they showed that the neutron dose can be reduced by approximately 70% at any position without influencing the primary beam used in treatment. Conclusions: This study was performed by assuming the HIMAC beamline; however, this study provides important information for reoptimizing the arrangement and the materials of beamline devices and designing a new facility for passive carbon-ion radiotherapy and probably passive proton radiotherapy.« less

Chandra Confirmation of a Pulsar Wind Nebula in DA 495

NASA Technical Reports Server (NTRS)

Arzoumanian, Z.; Safi-Harb, S.; Landecker, T.L.; Kothes, R.; Camilo, F.

2008-01-01

As part of a multiwavelength study of the unusual radio supernova remnant DA 495, we present observations made with the Chandra X-ray Observatory. Imaging and spectroscopic analysis confirms the previously detected X-ray source at the heart of the annular radio nebula, establishing the radiative properties of two key emission components: a soft unresolved source with a blackbody temperature of 1 MK consistent with a neutron star, surrounded by a nontherma1 nebula 40" in diameter exhibiting a power-law spectrum with photon index Gamma = 1.63, typical of a pulsar wind nebula. Morphologically, the nebula appears to be slightly extended along a direction, in projection on the sky, previously demonstrated to be of significance in radio and ASCA observations; we argue that this represents the orientation of the pulsar spin axis. At smaller scales, a narrow X-ray feature is seen extending out 5" from the point source, but energetic arguments suggest that it is not the resolved termination shock of the pulsar wind against the ambient medium. Finally, we argue based on synchrotron lifetimes in the nebular magnetic field that DA 495 represents the first example of a pulsar wind nebula in which electromagnetic flux makes up a significant part, together with particle flux, of the neutron star's wind.

Characterization of Point Defects in Lithium Aluminate (LiAlO2) Single Crystals

DTIC Science & Technology

2015-09-17

high-quality neutron detectors since 235U and 239Pu, the two isotopes used to fuel nuclear weapons , both emit neu- trons through spontaneous fission of...dissertation has iden- tified and characterized the major point defects created and induced through x ray and neutron radiation using electron paramagnetic... neutron irradiation is an F+ center; an oxygen vacancy with one trapped electron. This defect has two states, a stable state that survives up to 500 ◦C and

Real-time neutron imaging of gas turbines

NASA Astrophysics Data System (ADS)

Stewart, P. A. E.

1987-06-01

The current status of real-time neutron radiography imaging is briefly reviewed, and results of tests carried out on cold neutron sources are reported. In particular, attention is given to demonstrations of neutron radiography on a running gas turbine engine. The future role of real-time neutron imaging in engineering diagnostics is briefly discussed.

The neutron imaging diagnostic at NIF (invited).

PubMed

Merrill, F E; Bower, D; Buckles, R; Clark, D D; Danly, C R; Drury, O B; Dzenitis, J M; Fatherley, V E; Fittinghoff, D N; Gallegos, R; Grim, G P; Guler, N; Loomis, E N; Lutz, S; Malone, R M; Martinson, D D; Mares, D; Morley, D J; Morgan, G L; Oertel, J A; Tregillis, I L; Volegov, P L; Weiss, P B; Wilde, C H; Wilson, D C

2012-10-01

A neutron imaging diagnostic has recently been commissioned at the National Ignition Facility (NIF). This new system is an important diagnostic tool for inertial fusion studies at the NIF for measuring the size and shape of the burning DT plasma during the ignition stage of Inertial Confinement Fusion (ICF) implosions. The imaging technique utilizes a pinhole neutron aperture, placed between the neutron source and a neutron detector. The detection system measures the two dimensional distribution of neutrons passing through the pinhole. This diagnostic has been designed to collect two images at two times. The long flight path for this diagnostic, 28 m, results in a chromatic separation of the neutrons, allowing the independently timed images to measure the source distribution for two neutron energies. Typically the first image measures the distribution of the 14 MeV neutrons and the second image of the 6-12 MeV neutrons. The combination of these two images has provided data on the size and shape of the burning plasma within the compressed capsule, as well as a measure of the quantity and spatial distribution of the cold fuel surrounding this core.

Analysis of neutron propagation from the skyshine port of a fusion neutron source facility

NASA Astrophysics Data System (ADS)

Wakisaka, M.; Kaneko, J.; Fujita, F.; Ochiai, K.; Nishitani, T.; Yoshida, S.; Sawamura, T.

2005-12-01

The process of neutron leaking from a 14 MeV neutron source facility was analyzed by calculations and experiments. The experiments were performed at the Fusion Neutron Source (FNS) facility of the Japan Atomic Energy Institute, Tokai-mura, Japan, which has a port on the roof for skyshine experiments, and a 3He counter surrounded with a polyethylene moderator of different thicknesses was used to estimate the energy spectra and dose distributions. The 3He counter with a 3-cm-thick moderator was also used for dose measurements, and the doses evaluated by the counter counts and the calculated count-to-dose conversion factor agreed with the calculations to within ˜30%. The dose distribution was found to fit a simple analytical expression, D(r)=Q{exp(-r/λD)}/{r} and the parameters Q and λD are discussed.

Research opportunities with compact accelerator-driven neutron sources

NASA Astrophysics Data System (ADS)

Anderson, I. S.; Andreani, C.; Carpenter, J. M.; Festa, G.; Gorini, G.; Loong, C.-K.; Senesi, R.

2016-10-01

Since the discovery of the neutron in 1932 neutron beams have been used in a very broad range of applications, As an aging fleet of nuclear reactor sources is retired the use of compact accelerator-driven neutron sources (CANS) is becoming more prevalent. CANS are playing a significant and expanding role in research and development in science and engineering, as well as in education and training. In the realm of multidisciplinary applications, CANS offer opportunities over a wide range of technical utilization, from interrogation of civil structures to medical therapy to cultural heritage study. This paper aims to provide the first comprehensive overview of the history, current status of operation, and ongoing development of CANS worldwide. The basic physics and engineering regarding neutron production by accelerators, target-moderator systems, and beam line instrumentation are introduced, followed by an extensive discussion of various evolving applications currently exploited at CANS.

Simultaneous usage of pinhole and penumbral apertures for imaging small scale neutron sources from inertial confinement fusion experiments.

PubMed

Guler, N; Volegov, P; Danly, C R; Grim, G P; Merrill, F E; Wilde, C H

2012-10-01

Inertial confinement fusion experiments at the National Ignition Facility are designed to understand the basic principles of creating self-sustaining fusion reactions by laser driven compression of deuterium-tritium (DT) filled cryogenic plastic capsules. The neutron imaging diagnostic provides information on the distribution of the central fusion reaction region and the surrounding DT fuel by observing neutron images in two different energy bands for primary (13-17 MeV) and down-scattered (6-12 MeV) neutrons. From this, the final shape and size of the compressed capsule can be estimated and the symmetry of the compression can be inferred. These experiments provide small sources with high yield neutron flux. An aperture design that includes an array of pinholes and penumbral apertures has provided the opportunity to image the same source with two different techniques. This allows for an evaluation of these different aperture designs and reconstruction algorithms.

ANALYSIS OF THE MOMENTS METHOD EXPERIMENT

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

Kloster, R.L.

1959-09-01

Monte Cario calculations show the effects of a plane water-air boundary on both fast neutron and gamma dose rates. Multigroup diffusion theory calculation for a reactor source shows the effects of a plane water-air boundary on thermal neutron dose rate. The results of Monte Cario and multigroup calculations are compared with experimental values. The predicted boundary effect for fast neutrons of 7.3% agrees within 16% with the measured effect of 6.3%. The gamma detector did not measure a boundary effect because it lacked sensitivity at low energies. However, the effect predicted for gamma rays of 5 to 10% is asmore » large as that for neutrons. An estimate of the boundary effect for thermal neutrons from a PoBe source is obtained from the results of muitigroup diffusion theory calcuiations for a reactor source. The calculated boundary effect agrees within 13% with the measured values. (auth)« less

A Monte Carlo simulation study for the gamma-ray/neutron dual-particle imager using rotational modulation collimator (RMC).

PubMed

Kim, Hyun Suk; Choi, Hong Yeop; Lee, Gyemin; Ye, Sung-Joon; Smith, Martin B; Kim, Geehyun

2018-03-01

The aim of this work is to develop a gamma-ray/neutron dual-particle imager, based on rotational modulation collimators (RMCs) and pulse shape discrimination (PSD)-capable scintillators, for possible applications for radioactivity monitoring as well as nuclear security and safeguards. A Monte Carlo simulation study was performed to design an RMC system for the dual-particle imaging, and modulation patterns were obtained for gamma-ray and neutron sources in various configurations. We applied an image reconstruction algorithm utilizing the maximum-likelihood expectation-maximization method based on the analytical modeling of source-detector configurations, to the Monte Carlo simulation results. Both gamma-ray and neutron source distributions were reconstructed and evaluated in terms of signal-to-noise ratio, showing the viability of developing an RMC-based gamma-ray/neutron dual-particle imager using PSD-capable scintillators.

Active interrogation using low-energy nuclear reactions

NASA Astrophysics Data System (ADS)

Antolak, Arlyn; Doyle, Barney; Leung, Ka-Ngo; Morse, Daniel; Provencio, Paula

2005-09-01

High-energy photons and neutrons can be used to interrogate for heavily shielded fissile materials inside sealed cargo containers by detecting their prompt and/or delayed fission signatures. The FIND (Fissmat Inspection for Nuclear Detection) active interrogation system is based on a dual neutron+gamma source that uses low-energy (< 500 keV) proton- or deuteron-induced nuclear reactions to produce high intensities of mono-energetic gamma rays and/or neutrons. The source can be operated in either pulsed (e.g., to detect delayed photofission neutrons and gammas) or continuous (e.g., detecting prompt fission signatures) modes. For the gamma-rays, the source target can be segmented to incorporate different (p,γ) isotopes for producing gamma-rays at selective energies, thereby improving the probability of detection. The design parameters for the FIND system are discussed and preliminary accelerator-based measurements of gamma and neutron yields, background levels, and fission signals for several target materials under consideration are presented.

Neutron skyshine from intense 14-MeV neutron source facility

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

Nakamura, T.; Hayashi, K.; Takahashi, A.

1985-07-01

The dose distribution and the spectrum variation of neutrons due to the skyshine effect have been measured with the high-efficiency rem counter, the multisphere spectrometer, and the NE-213 scintillator in the environment surrounding an intense 14-MeV neutron source facility. The dose distribution and the energy spectra of neutrons around the facility used as a skyshine source have also been measured to enable the absolute evaluation of the skyshine effect. The skyshine effect was analyzed by two multigroup Monte Carlo codes, NIMSAC and MMCR-2, by two discrete ordinates S /sub n/ codes, ANISN and DOT3.5, and by the shield structure designmore » code for skyshine, SKYSHINE-II. The calculated results show good agreement with the measured results in absolute values. These experimental results should be useful as benchmark data for shyshine analysis and for shielding design of fusion facilities.« less

A Fast Pulse, High Intensity Neutron Source Based Upon The Dense Plasma Focus

NASA Astrophysics Data System (ADS)

Krishnan, M.; Bures, B.; Madden, R.; Blobner, F.; Elliott, K. Wilson

2009-12-01

Alameda Applied Sciences Corporation (AASC) has built a bench-top source of fast neutrons (˜10-30 ns, 2.45 MeV), that is portable and can be scaled to operate at ˜100 Hz. The source is a Dense Plasma Focus driven by three different capacitor banks: a 40 J/30 kA/100 Hz driver; a 500 J/130 kA/2 Hz driver and a 3 kJ/350 kA/0.5 Hz driver. At currents of ˜130 kA, this source produces ˜1×107 (DD) n/pulse. The neutron pulse widths are ˜10-30 ns and may be controlled by adjusting the DPF electrode geometry and operating parameters. This paper describes the scaling of the fast neutron output with current from such a Dense Plasma Focus source. For each current and driver, different DPF head designs are required to match to the current rise-time, as the operating pressure and anode radius/shape are varied. Doping of the pure D2 gas fill with Ar or Kr was shown earlier to increase the neutron output. Results are discussed in the light of scaling laws suggested by prior literature.

Developments in neutron beam devices and an advanced cold source for the NIST research reactor

NASA Astrophysics Data System (ADS)

Williams, Robert E.; Rowe, J. Michael

2002-01-01

The last 5 yr has been a period of steady growth in instrument capabilities and utilization at the National Institute of Standards and Technology Center for Neutron Research. Since the installation of the liquid hydrogen cold source in 1995, all of the instruments originally planned for the Cold Neutron Research Facility have been completed and made available to users, and three new thermal neutron instruments have been installed. Currently, an advanced cold source is being fabricated that will better couple the reactor core and the existing network of neutron guides. Many improvements are also being made in neutron optics to enhance the beam characteristics of certain instruments. For example, optical filters will be installed that will increase the fluxes at the two 30-m SANS instruments by as much as two. Sets of MgF 2 biconcave lenses have been developed for SANS that have demonstrated a significant improvement in resolution over conventional pinhole collimation. The recently commissioned high-flux backscattering spectrometer incorporates a converging guide, a large spherically focusing monochromator and analyzer, and a novel phase space transform chopper, to achieve very high intensity while maintaining excellent energy resolution. Finally, a prototype low background, doubly focusing neutron monochromator is nearing completion that will be the heart of a new cold neutron spectrometer, as well as two new thermal neutron triple axis spectrometers.

Neutron sources for investigations on extracted beams in Russia

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

Aksenov, V. L.

An overview is presented of the current status and prospects for the development of neutron sources intended for investigations on extracted beams in Russia. The participation of Russia in international scientific organizations is demonstrated.

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.

Evaluation of Am–Li neutron spectra data for active well type neutron multiplicity measurements of uranium

DOE PAGES

Goddard, Braden; Croft, Stephen; Lousteau, Angela; ...

2016-05-25

Safeguarding nuclear material is an important and challenging task for the international community. One particular safeguards technique commonly used for uranium assay is active neutron correlation counting. This technique involves irradiating unused uranium with ( α,n) neutrons from an Am-Li source and recording the resultant neutron pulse signal which includes induced fission neutrons. Although this non-destructive technique is widely employed in safeguards applications, the neutron energy spectra from an Am-Li sources is not well known. Several measurements over the past few decades have been made to characterize this spectrum; however, little work has been done comparing the measured spectra ofmore » various Am-Li sources to each other. This paper examines fourteen different Am-Li spectra, focusing on how these spectra affect simulated neutron multiplicity results using the code Monte Carlo N-Particle eXtended (MCNPX). Two measurement and simulation campaigns were completed using Active Well Coincidence Counter (AWCC) detectors and uranium standards of varying enrichment. The results of this work indicate that for standard AWCC measurements, the fourteen Am-Li spectra produce similar doubles and triples count rates. Finally, the singles count rates varied by as much as 20% between the different spectra, although they are usually not used in quantitative analysis.« less

Characterization of the graphite pile as a source of thermal neutrons

NASA Astrophysics Data System (ADS)

Vykydal, Zdenek; Králík, Miloslav; Jančář, Aleš; Kopecký, Zdeněk; Dressler, Jan; Veškrna, Martin

2015-11-01

A new graphite pile designed to serve as a standard source of thermal neutrons has been built at the Czech Metrology Institute. Actual dimensions of the pile are 1.95 m (W)×1.95 m (L)×2.0 m (H). At its center, there is a measurement channel whose dimensions are 0.4 m×0.4 m×1.25 m (depth). The channel is equipped with a calibration bench, which allows reproducible placement of the tested/calibrated device. At a distance of 80 cm from the channel axis, six holes are symmetrically located allowing the placement of radionuclide neutron sources of Pu-Be and/or Am-Be type. Spatial distribution of thermal neutron fluence in the cavity was calculated in detail with the MCNP neutron transport code. Experimentally, it was measured with two active detectors: a small 3He proportional detector by the French company LMT, type 0.5 NH 1/1 KF, and a silicon pixel detector Timepix with 10B converter foil. The relative values of thermal neutron fluence rate obtained with active detectors were converted to absolute ones using thermal neutron fluence rates measured by means of gold foil activation. The quality of thermal neutron field was characterized by the cadmium ratio.

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

NASA Astrophysics Data System (ADS)

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

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 dramatically in recent years. Neutron generators based on deuteriumtritium (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 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 2-5 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.

Nodal weighting factor method for ex-core fast neutron fluence evaluation

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

Chiang, R. T.

The nodal weighting factor method is developed for evaluating ex-core fast neutron flux in a nuclear reactor by utilizing adjoint neutron flux, a fictitious unit detector cross section for neutron energy above 1 or 0.1 MeV, the unit fission source, and relative assembly nodal powers. The method determines each nodal weighting factor for ex-core neutron fast flux evaluation by solving the steady-state adjoint neutron transport equation with a fictitious unit detector cross section for neutron energy above 1 or 0.1 MeV as the adjoint source, by integrating the unit fission source with a typical fission spectrum to the solved adjointmore » flux over all energies, all angles and given nodal volume, and by dividing it with the sum of all nodal weighting factors, which is a normalization factor. Then, the fast neutron flux can be obtained by summing the various relative nodal powers times the corresponding nodal weighting factors of the adjacent significantly contributed peripheral assembly nodes and times a proper fast neutron attenuation coefficient over an operating period. A generic set of nodal weighting factors can be used to evaluate neutron fluence at the same location for similar core design and fuel cycles, but the set of nodal weighting factors needs to be re-calibrated for a transition-fuel-cycle. This newly developed nodal weighting factor method should be a useful and simplified tool for evaluating fast neutron fluence at selected locations of interest in ex-core components of contemporary nuclear power reactors. (authors)« less

A setup for active neutron analysis of the fissile material content in fuel assemblies of nuclear reactors

NASA Astrophysics Data System (ADS)

Bushuev, A. V.; Kozhin, A. F.; Aleeva, T. B.; Zubarev, V. N.; Petrova, E. V.; Smirnov, V. E.

2016-12-01

An active neutron method for measuring the residual mass of 235U in spent fuel assemblies (FAs) of the IRT MEPhI research reactor is presented. The special measuring stand design and uniform irradiation of the fuel with neutrons along the entire length of the active part of the FA provide high accuracy of determination of the residual 235U content. AmLi neutron sources yield a higher effect/background ratio than other types of sources and do not induce the fission of 238U. The proposed method of transfer of the isotope source in accordance with a given algorithm may be used in experiments where the studied object needs to be irradiated with a uniform fluence.

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

a Compact, Rf-Driven Pulsed Ion Source for Intense Neutron Generation

NASA Astrophysics Data System (ADS)

Perkins, L. T.; Celata, C. M.; Lee, Y.; Leung, K. N.; Picard, D. S.; Vilaithong, R.; Williams, M. D.; Wutte, D.

1997-05-01

Lawrence Berkeley National Laboratory is currently developing a compact, sealed-accelerator-tube neutron generator capable of producing a neutron flux in the range of 109 to 1010 D-T neutrons per second. The ion source, a miniaturized variation of earlier 2 MHz radio-frequency (rf)-driven multicusp ion sources, is designed to fit within a #197# 5 cm diameter borehole. Typical operating parameters include repetition rates up to 100 pps, with pulse widths between 10 and 80 us and source pressures as low as #197# 5 mTorr. In this configuration, peak extractable hydrogen current exceeding 35 mA from a 2 mm diameter aperture together with H1+ yields over 94% have been achieved. The required rf impedance matching network has been miniaturized to #197# 5 cm diameter. The accelerator column is a triode design using the IGUN ion optics codes and allows for electron suppression. Results from the testing of the integrated matching network-ion source-accelerator system will be presented.

Use of the WNR spallation neutron source at LAMPF to determine the absolute efficiency of a neutron scintillation detector

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

Staples, P.A.; Egan, J.J.; Kegel, G.H.R.

1994-06-01

Prompt fission neutron spectrum measurements at the University of Massachusetts Lowell 5.5 MV Van de Graaff accelerator laboratory require that the neutron detector efficiency be well known over a neutron energy range of 100 keV to 20 MeV. The efficiency of the detector, has been determined for energies greater than 5.0 MeV using the Weapons Neutron Research (WNR) white neutron source at the Los Alamos Meson Physics Facility (LAMPF) in a pulsed beam, time-of-flight (TOF) experiment. Carbon matched polyethylene and graphite scatterers were used to obtain a hydrogen spectrum. The detector efficiency was determined using the well known H(n,n) scatteringmore » cross section. Results are compared to the detector efficiency calculation program SCINFUL available from the Radiation Shielding Information Center at Oak Ridge National Laboratory.« less

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.

Characterization of the Shielded Neutron Source at Triangle Universities Nuclear Laboratory

NASA Astrophysics Data System (ADS)

Hobson, Chad; Finch, Sean; Howell, Calvin; Malone, Ron; Tornow, Wernew

2016-09-01

In 2015, Triangle Universities Nuclear Laboratory rebuilt its shielded neutron source (SNS) with the goal of improving neutron beam collimation and reducing neutron and gamma-ray backgrounds. Neutrons are produced via the 2H(d,n)3He reaction and then collimated by heavy shielding to form a beam. The SNS has the ability to produce both a rectangular and circular neutron beam through use of two collimators with different beam apertures. Our work characterized both the neutron beam profiles as well as the neutron and gamma-ray backgrounds at various locations around the SNS. This characterization was performed to provide researchers who use the SNS with beam parameters necessary to plan and conduct an experiment. Vertical and horizontal beam profiles were measured at two different distances from the neutron production cell by scanning a small plastic scintillator across the face of the beam at various energies for each collimator. Background neutron and gamma-ray intensities were measured using time-of-flight techniques at 10 MeV and 16 MeV with the rectangular collimator. We present results on the position and size of neutron beam as well as on the structure and magnitude of the backgrounds.

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.

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

Clarke, S. D.; Hamel, M. C.; Bourne, M. M.

Active interrogation creates an environment that is particularly challenging from a radiation-detection standpoint: the elevated background levels from the source can mask the desired signatures from the SNM. Neutron based interrogation experiments have shown that nanosecond-level timing is required to discriminate induced-fission neutrons from the scattered source neutrons. Previous experiments using high-energy bremsstrahlung X-rays have demonstrated the ability to induce and detect prompt photofission neutrons from single target materials; however, a real-world application would require spectroscopic capability to discern between photofission neutrons emitted by SNM and neutrons emitted by other reactions in non-SNM. Using digital pulseshape discrimination, organic liquid scintillatorsmore » are capable of reliably detecting neutrons in an intense gamma-ray field. Photon misclassification rates as low as 1 in 10 6 have been achieved, which is approaching the level of gaseous neutron detectors such as 3He without the need for neutron moderation. These scintillators also possess nanosecond-timing resolution, making them candidates for both neutron-and photon-driven active interrogation systems. Lastly, we have applied an array of liquid and NaI(Tl) scintillators to successfully image 13.7 kg of HEU interrogated by a DT neutron generator; the system was in the direct presence of the accelerator during the experiment.« less

Detectors for Active Interrogation Applications

NASA Astrophysics Data System (ADS)

Clarke, S. D.; Hamel, M. C.; Bourne, M. M.; Pozzi, S. A.

Active interrogation creates an environment that is particularly challenging from a radiation-detection standpoint: the elevated background levels from the source can mask the desired signatures from the SNM. Neutron based interrogation experiments have shown that nanosecond-level timing is required to discriminate induced-fission neutrons from the scattered source neutrons. Previous experiments using high-energy bremsstrahlung X-rays have demonstrated the ability to induce and detect prompt photofission neutrons from single target materials; however, a real-world application would require spectroscopic capability to discern between photofission neutrons emitted by SNM and neutrons emitted by other reactions in non-SNM. Using digital pulse-shape discrimination, organic liquid scintillators are capable of reliably detecting neutrons in an intense gamma-ray field. Photon misclassification rates as low as 1 in 106 have been achieved, which is approaching the level of gaseous neutron detectors such as 3He without the need for neutron moderation. These scintillators also possess nanosecond-timing resolution, making them candidates for both neutron-and photon-driven active interrogation systems. We have applied an array of liquid and NaI(Tl) scintillators to successfully image 13.7 kg of HEU interrogated by a DT neutron generator; the system was in the direct presence of the accelerator during the experiment.

Neutronic analysis of the 1D and 1E banks reflux detection system

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

Blanchard, A.

1999-12-21

Two H Canyon neutron monitoring systems for early detection of postulated abnormal reflux conditions in the Second Uranium Cycle 1E and 1D Mixer-Settle Banks have been designed and built. Monte Carlo neutron transport simulations using the general purpose, general geometry, n-particle MCNP code have been performed to model expected response of the monitoring systems to varying conditions.The confirmatory studies documented herein conclude that the 1E and 1D neutron monitoring systems are able to achieve adequate neutron count rates for various neutron source and detector configurations, thereby eliminating excessive integration count time. Neutron count rate sensitivity studies are also performed. Conversely,more » the transport studies concluded that the neutron count rates are statistically insensitive to nitric acid content in the aqueous region and to the transition region length. These studies conclude that the 1E and 1D neutron monitoring systems are able to predict the postulated reflux conditions for all examined perturbations in the neutron source and detector configurations. In the cases examined, the relative change in the neutron count rates due to postulated transitions from normal {sup 235}U concentration levels to reflux levels remain satisfactory detectable.« less

Application of the MCNPX-McStas interface for shielding calculations and guide design at ESS

NASA Astrophysics Data System (ADS)

Klinkby, E. B.; Knudsen, E. B.; Willendrup, P. K.; Lauritzen, B.; Nonbøl, E.; Bentley, P.; Filges, U.

2014-07-01

Recently, an interface between the Monte Carlo code MCNPX and the neutron ray-tracing code MCNPX was developed [1, 2]. Based on the expected neutronic performance and guide geometries relevant for the ESS, the combined MCNPX-McStas code is used to calculate dose rates along neutron beam guides. The generation and moderation of neutrons is simulated using a full scale MCNPX model of the ESS target monolith. Upon entering the neutron beam extraction region, the individual neutron states are handed to McStas via the MCNPX-McStas interface. McStas transports the neutrons through the beam guide, and by using newly developed event logging capability, the neutron state parameters corresponding to un-reflected neutrons are recorded at each scattering. This information is handed back to MCNPX where it serves as neutron source input for a second MCNPX simulation. This simulation enables calculation of dose rates in the vicinity of the guide. In addition the logging mechanism is employed to record the scatterings along the guides which is exploited to simulate the supermirror quality requirements (i.e. m-values) needed at different positions along the beam guide to transport neutrons in the same guide/source setup.

Analysis of a Neutronic Experiment on a Simulated Mercury Spallation Neutron Target Assembly Bombarded by Giga-Electron-Volt Protons

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

Maekawa, Fujio; Meigo, Shin-ichiro; Kasugai, Yoshimi

2005-05-15

A neutronic benchmark experiment on a simulated spallation neutron target assembly was conducted by using the Alternating Gradient Synchrotron at Brookhaven National Laboratory and was analyzed to investigate the prediction capability of Monte Carlo simulation codes used in neutronic designs of spallation neutron sources. The target assembly consisting of a mercury target, a light water moderator, and a lead reflector was bombarded by 1.94-, 12-, and 24-GeV protons, and the fast neutron flux distributions around the target and the spectra of thermal neutrons leaking from the moderator were measured in the experiment. In this study, the Monte Carlo particle transportmore » simulation codes NMTC/JAM, MCNPX, and MCNP-4A with associated cross-section data in JENDL and LA-150 were verified based on benchmark analysis of the experiment. As a result, all the calculations predicted the measured quantities adequately; calculated integral fluxes of fast and thermal neutrons agreed approximately within {+-}40% with the experiments although the overall energy range encompassed more than 12 orders of magnitude. Accordingly, it was concluded that these simulation codes and cross-section data were adequate for neutronics designs of spallation neutron sources.« less

Expanding Lorentz and spectrum corrections to large volumes of reciprocal space for single-crystal time-of-flight neutron diffraction

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

Michels-Clark, Tara M.; Savici, Andrei T.; Lynch, Vickie E.

Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next to Bragg diffraction (BD). BD forms a regular sparse grid of intense discrete points in reciprocal space. Traditionally, the intensity of each Bragg peak is extracted by integration of each individual reflection first, followed by application of the required corrections. In contrast, mDS is weak and covers expansive volumes of reciprocal space close to, or between, Bragg reflections. For a representative measurement of the diffuse scattering, multiple sample orientationsmore » are generally required, where many points in reciprocal space are measured multiple times and the resulting data are combined. The common post-integration data reduction method is not optimal with regard to counting statistics. A general and inclusive data processing method is needed. In this contribution, a comprehensive data analysis approach is introduced to correct and merge the full volume of scattering data in a single step, while correctly accounting for the statistical weight of the individual measurements. Lastly, development of this new approach required the exploration of a data treatment and correction protocol that includes the entire collected reciprocal space volume, using neutron time-of-flight or wavelength-resolved data collected at TOPAZ at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Expanding Lorentz and spectrum corrections to large volumes of reciprocal space for single-crystal time-of-flight neutron diffraction

DOE PAGES

Michels-Clark, Tara M.; Savici, Andrei T.; Lynch, Vickie E.; ...

2016-03-01

Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next to Bragg diffraction (BD). BD forms a regular sparse grid of intense discrete points in reciprocal space. Traditionally, the intensity of each Bragg peak is extracted by integration of each individual reflection first, followed by application of the required corrections. In contrast, mDS is weak and covers expansive volumes of reciprocal space close to, or between, Bragg reflections. For a representative measurement of the diffuse scattering, multiple sample orientationsmore » are generally required, where many points in reciprocal space are measured multiple times and the resulting data are combined. The common post-integration data reduction method is not optimal with regard to counting statistics. A general and inclusive data processing method is needed. In this contribution, a comprehensive data analysis approach is introduced to correct and merge the full volume of scattering data in a single step, while correctly accounting for the statistical weight of the individual measurements. Lastly, development of this new approach required the exploration of a data treatment and correction protocol that includes the entire collected reciprocal space volume, using neutron time-of-flight or wavelength-resolved data collected at TOPAZ at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

PHOTON SPECTRA IN NPL STANDARD RADIONUCLIDE NEUTRON FIELDS.

PubMed

Roberts, N J

2017-09-23

A HPGe detector has been used to measure the photon spectra from the majority of radionuclide neutron sources in use at NPL (252Cf, 241Am-Be, 241Am-Li, 241Am-B). The HPGe was characterised then modelled to produce a response matrix. The measured pulse height spectra were then unfolded to produce photon fluence spectra. Changes in the photon spectrum with time from a 252Cf source are evident. Spectra from a 2-year-old and 42-year-old 252Cf source are presented showing the change from a continuum to peaks from long-lived isotopes of Cf. Other radionuclide neutron source spectra are also presented and discussed. The new spectra were used to improve the photon to neutron dose equivalent ratios from some earlier work at NPL with GM tubes and EPDs. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Some Experimental and Monte Carlo Investigations of the Plastic Scintillators for the Current Mode Measurements at Pulsed Neutron Sources

NASA Astrophysics Data System (ADS)

Rogov, A.; Pepyolyshev, Yu.; Carta, M.; d'Angelo, A.

Scintillation detector (SD) is widely used in neutron and gamma-spectrometry in a count mode. The organic scintillators for the count mode of the detector operation are investigated rather well. Usually, they are applied for measurement of amplitude and time distributions of pulses caused by single interaction events of neutrons or gamma's with scintillator material. But in a large area of scientific research scintillation detectors can alternatively be used on a current mode by recording the average current from the detector. For example,the measurements of the neutron pulse shape at the pulsed reactors or another pulsed neutron sources. So as to get a rather large volume of experimental data at pulsed neutron sources, it is necessary to use the current mode detector for registration of fast neutrons. Many parameters of the SD are changed with a transition from an accounting mode to current one. For example, the detector efficiency is different in counting and current modes. Many effects connected with time accuracy become substantial. Besides, for the registration of solely fast neutrons, as must be in many measurements, in the mixed radiation field of the pulsed neutron sources, SD efficiency has to be determined with a gamma-radiation shield present. Here is no calculations or experimental data on SD current mode operation up to now. The response functions of the detectors can be either measured in high-precision reference fields or calculated by a computer simulation. We have used the MCNP code [1] and carried out some experiments for investigation of the plastic performances in a current mode. There are numerous programs performing simulating similar to the MCNP code. For example, for neutrons there are [2-4], for photons - [5-8]. However, all known codes to use (SCINFUL, NRESP4, SANDYL, EGS49) have more stringent restrictions on the source, geometry and detector characteristics. In MCNP code a lot of these restrictions are absent and you need only to write special additions for proton and electron recoil and transfer energy to light output. These code modifications allow taking into account all processes in organic scintillator influence the light yield.

Analysis of the propagation of neutrons and gamma-rays from the fast neutron source reactor YAYOI

NASA Astrophysics Data System (ADS)

Yoshida, Shigeo; Murata, Isao; Nakagawa, Tsutomu; Saito, Isao

2011-10-01

The skyshine effect is crucial for designing appropriate shielding. To investigate the skyshine effect, the propagation of neutrons was measured and analyzed at the fast neutron source reactor YAYOI. Pulse height spectra and dose distributions of neutron and secondary gamma-ray were measured outside YAYOI, and analyzed with MCNP-5 and JENDL-3.3. Comparison with the experimental results showed good agreement. Also, a semi-empirical formula was successfully derived to describe the dose distribution. The formulae can be used to predict the skyshine effect at YAYOI, and will be useful for estimating the skyshine effect and designing the shield structure for fusion facilities.

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.

Energy-resolved fast neutron resonance radiography at CSNS

NASA Astrophysics Data System (ADS)

Tan, Zhixin; Tang, Jingyu; Jing, Hantao; Fan, Ruirui; Li, Qiang; Ning, Changjun; Bao, Jie; Ruan, Xichao; Luan, Guangyuan; Feng, Changqin; Zhang, Xianpeng

2018-05-01

The white neutron beamline at the China Spallation Neutron Source will be used mainly for nuclear data measurements. It will be characterized by high flux and broad energy spectra. To exploit the beamline as a neutron imaging source, we propose a liquid scintillator fiber array for fast neutron resonance radiography. The fiber detector unit has a small exposed area, which will limit the event counts and separate the events in time, thus satisfying the requirements for single-event time-of-flight (SEToF) measurement. The current study addresses the physical design criteria for ToF measurement, including flux estimation and detector response. Future development and potential application of the technology are also discussed.

A liquid hydrocarbon deuteron source for neutron generators

NASA Astrophysics Data System (ADS)

Schwoebel, P. R.

2017-06-01

Experimental studies of a deuteron spark source for neutron generators using hydrogen isotope fusion reactions are reported. The ion source uses a spark discharge between electrodes coated with a deuterated hydrocarbon liquid, here Santovac 5, to inhibit permanent electrode erosion and extend the lifetime of high-output neutron generator spark ion sources. Thompson parabola mass spectra show that principally hydrogen and deuterium ions are extracted from the ion source. Hydrogen is the chief residual gas phase species produced due to source operation in a stainless-steel vacuum chamber. The prominent features of the optical emission spectra of the discharge are C+ lines, the hydrogen Balmer Hα-line, and the C2 Swan bands. Operation of the ion source was studied in a conventional laboratory neutron generator. The source delivered an average deuteron current of ˜0.5 A nominal to the target in a 5 μs duration pulse at 1 Hz with target voltages of -80 to -100 kV. The thickness of the hydrocarbon liquid in the spark gap and the consistency thereof from spark to spark influences the deuteron yield and plays a role in determining the beam-focusing characteristics through the applied voltage necessary to break down the spark gap. Higher breakdown voltages result in larger ion beam spots on the target and vice-versa. Because the liquid self-heals and thereby inhibits permanent electrode erosion, the liquid-based source provides long life, with 104 pulses to date, and without clear evidence that, in principle, the lifetime could not be much longer. Initial experiments suggest that an alternative cylindrical target-type generator design can extract approximately 10 times the deuteron current from the source. Preliminary data using the deuterated source liquid as a neutron-producing target are also presented.

The role of neutron star mergers in the chemical evolution of the Galactic halo

NASA Astrophysics Data System (ADS)

Cescutti, G.; Romano, D.; Matteucci, F.; Chiappini, C.; Hirschi, R.

2015-05-01

Context. The dominant astrophysical production site of the r-process elements has not yet been unambiguously identified. The suggested main r-process sites are core-collapse supernovae and merging neutron stars. Aims: We explore the problem of the production site of Eu. We also use the information present in the observed spread in the Eu abundances in the early Galaxy, and not only its average trend. Moreover, we extend our investigations to other heavy elements (Ba, Sr, Rb, Zr) to provide additional constraints on our results. Methods: We adopt a stochastic chemical evolution model that takes inhomogeneous mixing into account. The adopted yields of Eu from merging neutron stars and from core-collapse supernovae are those that are able to explain the average [Eu/Fe]-[Fe/H] trend observed for solar neighbourhood stars, the solar abundance of Eu, and the present-day abundance gradient of Eu along the Galactic disc in the framework of a well-tested homogeneous model for the chemical evolution of the Milky Way. Rb, Sr, Zr, and Ba are produced by both the s- and r-processes. The r-process yields were obtained by scaling the Eu yields described above according to the abundance ratios observed in r-process rich stars. The s-process contribution by spinstars is the same as in our previous papers. Results: Neutron star binaries that merge in less than 10 Myr or neutron star mergers combined with a source of r-process generated by massive stars can explain the spread of [Eu/Fe] in the Galactic halo. The combination of r-process production by neutron star mergers and s-process production by spinstars is able to reproduce the available observational data for Sr, Zr, and Ba. We also show the first predictions for Rb in the Galactic halo. Conclusions: We confirm previous results that either neutron star mergers on a very short timescale or both neutron star mergers and at least a fraction of Type II supernovae have contributed to the synthesis of Eu in the Galaxy. The r-process production of Sr, Zr, and Ba by neutron star mergers - complemented by an s-process production by spinstars - provide results that are compatible with our previous findings based on other r-process sites. We critically discuss the weak and strong points of both neutron star merging and supernova scenarios for producing Eu and eventually suggest that the best solution is probably a mixed one in which both sources produce Eu. In fact, this scenario reproduces the scatter observed in all the studied elements better. Warning, no authors found for 2015A&A...577A.131.

Neutron Scattering Announcements

Science.gov Websites

will be added. We encourage everyone interested in neutron scattering to take full advantage of this neutron source ESS. After an initial layout phase using analytical considerations further assessment of Home Page | Facilities | Reference | Software | Conferences | Announcements | Mailing Lists Neutron

Detection of entrapped moisture in honeycomb sandwich structures

NASA Technical Reports Server (NTRS)

Hallmark, W. B.

1967-01-01

Thermal neutron moisture detection system detects entrapped moisture in intercellular areas of bonded honeycomb sandwich structures. A radium/beryllium fast neutron source bombards a specimen. The emitted thermal neutrons from the target nucleus are detected and counted by a boron trifluoride thermal neutron detector.

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

Thermal neutron calibration channel at LNMRI/IRD.

PubMed

Astuto, A; Salgado, A P; Leite, S P; Patrão, K C S; Fonseca, E S; Pereira, W W; Lopes, R T

2014-10-01

The Brazilian Metrology Laboratory of Ionizing Radiations (LNMRI) standard thermal neutron flux facility was designed to provide uniform neutron fluence for calibration of small neutron detectors and individual dosemeters. This fluence is obtained by neutron moderation from four (241)Am-Be sources, each with 596 GBq, in a facility built with blocks of graphite/paraffin compound and high-purity carbon graphite. This study was carried out in two steps. In the first step, simulations using the MCNPX code on different geometric arrangements of moderator materials and neutron sources were performed. The quality of the resulting neutron fluence in terms of spectrum, cadmium ratio and gamma-neutron ratio was evaluated. In the second step, the system was assembled based on the results obtained on the simulations, and new measurements are being made. These measurements will validate the system, and other intercomparisons will ensure traceability to the International System of Units. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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.

Break Point Distribution on Chromosome 3 of Human Epithelial Cells exposed to Gamma Rays, Neutrons and Fe Ions

NASA Technical Reports Server (NTRS)

Hada, M.; Saganti, P. B.; Gersey, B.; Wilkins, R.; Cucinotta, F. A.; Wu, H.

2007-01-01

Most of the reported studies of break point distribution on the damaged chromosomes from radiation exposure were carried out with the G-banding technique or determined based on the relative length of the broken chromosomal fragments. However, these techniques lack the accuracy in comparison with the later developed multicolor banding in situ hybridization (mBAND) technique that is generally used for analysis of intrachromosomal aberrations such as inversions. Using mBAND, we studied chromosome aberrations in human epithelial cells exposed in vitro to both low or high dose rate gamma rays in Houston, low dose rate secondary neutrons at Los Alamos National Laboratory and high dose rate 600 MeV/u Fe ions at NASA Space Radiation Laboratory. Detailed analysis of the inversion type revealed that all of the three radiation types induced a low incidence of simple inversions. Half of the inversions observed after neutron or Fe ion exposure, and the majority of inversions in gamma-irradiated samples were accompanied by other types of intrachromosomal aberrations. In addition, neutrons and Fe ions induced a significant fraction of inversions that involved complex rearrangements of both inter- and intrachromosome exchanges. We further compared the distribution of break point on chromosome 3 for the three radiation types. The break points were found to be randomly distributed on chromosome 3 after neutrons or Fe ions exposure, whereas non-random distribution with clustering break points was observed for gamma-rays. The break point distribution may serve as a potential fingerprint of high-LET radiation exposure.

Advances in the computation of the Sjöstrand, Rossi, and Feynman distributions

DOE PAGES

Talamo, A.; Gohar, Y.; Gabrielli, F.; ...

2017-02-01

This study illustrates recent computational advances in the application of the Sjöstrand (area), Rossi, and Feynman methods to estimate the effective multiplication factor of a subcritical system driven by an external neutron source. The methodologies introduced in this study have been validated with the experimental results from the KUKA facility of Japan by Monte Carlo (MCNP6 and MCNPX) and deterministic (ERANOS, VARIANT, and PARTISN) codes. When the assembly is driven by a pulsed neutron source generated by a particle accelerator and delayed neutrons are at equilibrium, the Sjöstrand method becomes extremely fast if the integral of the reaction rate frommore » a single pulse is split into two parts. These two integrals distinguish between the neutron counts during and after the pulse period. To conclude, when the facility is driven by a spontaneous fission neutron source, the timestamps of the detector neutron counts can be obtained up to the nanosecond precision using MCNP6, which allows obtaining the Rossi and Feynman distributions.« less

Material issues relating to high power spallation neutron sources

NASA Astrophysics Data System (ADS)

Futakawa, M.

2015-02-01

Innovative researches using neutrons are being performed at the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), in which a mercury target system is installed for MW-class pulse spallation neutron sources. In order to produce neutrons by the spallation reaction, proton beams are injected into the mercury target. At the moment, when the intense proton beam hits the target, pressure waves are generated in mercury because of the abrupt heat deposition. The pressure waves interact with the target vessel, leading to negative pressure that may cause cavitation along the vessel wall, i.e. on the interface between liquid and solid metals. On the other hand, the structural materials are subjected to irradiation damage due to protons and neutrons, very high cycle fatigue damages and so-called "liquid metal embrittlement". That is, the structural materials must be said to be exposed to the extremely severe environments. In the paper, research and development relating to the material issues in the high power spallation neutron sources that has been performed so far at J-PARC is summarized.

Neutron kinetics in moderators and SNM detection through epithermal-neutron-induced fissions

NASA Astrophysics Data System (ADS)

Gozani, Tsahi; King, Michael J.

2016-01-01

Extension of the well-established Differential Die Away Analysis (DDAA) into a faster time domain, where more penetrating epithermal neutrons induce fissions, is proposed and demonstrated via simulations and experiments. In the proposed method the fissions stimulated by thermal, epithermal and even higher-energy neutrons are measured after injection of a narrow pulse of high-energy 14 MeV (d,T) or 2.5 MeV (d,D) source neutrons, appropriately moderated. The ability to measure these fissions stems from the inherent correlation of neutron energy and time ("E-T" correlation) during the process of slowing down of high-energy source neutrons in common moderating materials such as hydrogenous compounds (e.g., polyethylene), heavy water, beryllium and graphite. The kinetic behavior following injection of a delta-function-shaped pulse (in time) of 14 MeV neutrons into such moderators is studied employing MCNPX simulations and, when applicable, some simple "one-group" models. These calculations served as a guide for the design of a source moderator which was used in experiments. Qualitative relationships between slowing-down time after the pulse and the prevailing neutron energy are discussed. A laboratory system consisting of a 14 MeV neutron generator, a polyethylene-reflected Be moderator, a liquid scintillator with pulse-shape discrimination (PSD) and a two-parameter E-T data acquisition system was set up to measure prompt neutron and delayed gamma-ray fission signatures in a 19.5% enriched LEU sample. The measured time behavior of thermal and epithermal neutron fission signals agreed well with the detailed simulations. The laboratory system can readily be redesigned and deployed as a mobile inspection system for SNM in, e.g., cars and vans. A strong pulsed neutron generator with narrow pulse (<75 ns) at a reasonably high pulse frequency could make the high-energy neutron induced fission modality a realizable SNM detection technique.

Neutron production from beam-modifying devices in a modern double scattering proton therapy beam delivery system.

PubMed

Pérez-Andújar, Angélica; Newhauser, Wayne D; Deluca, Paul M

2009-02-21

In this work the neutron production in a passive beam delivery system was investigated. Secondary particles including neutrons are created as the proton beam interacts with beam shaping devices in the treatment head. Stray neutron exposure to the whole body may increase the risk that the patient develops a radiogenic cancer years or decades after radiotherapy. We simulated a passive proton beam delivery system with double scattering technology to determine the neutron production and energy distribution at 200 MeV proton energy. Specifically, we studied the neutron absorbed dose per therapeutic absorbed dose, the neutron absorbed dose per source particle and the neutron energy spectrum at various locations around the nozzle. We also investigated the neutron production along the nozzle's central axis. The absorbed doses and neutron spectra were simulated with the MCNPX Monte Carlo code. The simulations revealed that the range modulation wheel (RMW) is the most intense neutron source of any of the beam spreading devices within the nozzle. This finding suggests that it may be helpful to refine the design of the RMW assembly, e.g., by adding local shielding, to suppress neutron-induced damage to components in the nozzle and to reduce the shielding thickness of the treatment vault. The simulations also revealed that the neutron dose to the patient is predominated by neutrons produced in the field defining collimator assembly, located just upstream of the patient.

Neutron-Star Merger Detected By Many Eyes and Ears

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-10-01

Where were you on Thursday, 17 August 2017? I was in Idaho, getting ready for Monday mornings solar eclipse. What I didnt know was that, at the time, around 70 teams around the world were mobilizing to point their ground- and space-based telescopes at a single patch of sky suspected to host the first gravitational-wave-detected merger of two neutron stars.Sudden Leaps for ScienceThe masses for black holes detected through electromagnetic observations (purple), black holes measured by gravitational-wave observations (blue), neutron stars measured with electromagnetic observations (yellow), and the neutron stars that merged in GW170817 (orange). [LIGO-Virgo/Frank Elavsky/NorthwesternUniversity]The process of science is long and arduous, generally occurring at a slow plod as theorists make predictions, and observations are then used to chip away at these theories, gradually confirming or disproving them. It is rare that science progresses forward in a giant leap, with years upon years of theories confirmed in one fell swoop.14 September 2015 marked the day of one such leap, as the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves for the first time simultaneously verifying that black holes exist, that black-hole binaries exist, and that they can merge on observable timescales, emitting signals that directly confirm the predictions of general relativity.As it turns out, 17 August 2017 was another such day. On this day, LIGO observed a gravitational-wave signal unlike its previous black-hole detections. Instead, this was a signal consistent with the merger of two neutron stars.Artists illustrations of the stellar-merger model for short gamma-ray bursts. In the model, 1) two neutron stars inspiral, 2) they merge and produce a gamma-ray burst, 3) a small fraction of their mass is flung out and radiates as a kilonova, 4) a massive neutron star or black hole with a disk remains after the event. [NASA, ESA, and A. Feild (STScI)]What We PredictedTheoretical models describing the merger of two compact objects predict a chirping gravitational-wave signal as the objects spiral closer and closer. Unlike in a black-hole merger, however, the end of the chirp from merging neutron stars should coincide with a phenomenon known as a short gamma-ray burst: a powerful storm of energetic gamma rays produced as the objects finally collide.According to the models, these gravitational waves and gamma rays will be followed by a kilonova a transient source visible in infrared, optical, and ultraviolet which arises from radioactive decay of heavy elements formed in the collision. This source should gradually decay over a timescale of weeks.Lastly, the merger could create a powerful jet of high-energy particles, which could be visible to us in X-ray and radio wavelengths as it is emitted and interacts with its surrounding environment. We could also detect neutrinos from this outflow.What We Saw (and Didnt See)The localization of the gravitational-wave, gamma-ray, and optical signals of the neutron-star merger detected on 17 August, 2017. [Abbott et al. 2017]So what did we see on 17 August, 2017 and thereafter? Heres what was found by the army of collaborations searching in gravitational waves, electromagnetic signals across the spectrum, and neutrinos:Gravitational WavesThe gravitational-wave signature of a binary neutron-star merger was observed with all three gravitational-wave detectors currently operating as a part of the LIGO-Virgo collaboration. GW170817s signal was in the sensitivity band of these detectors for 100 seconds, arriving first at the Virgo detector in Italy, next at LIGO-Livingston in Louisiana 22 milliseconds later, and finally at LIGO-Hanford in Washington 3 milliseconds after that. These detections localized the source to a region of 31 square degrees at a relatively nearby distance of 130 million light-years, and they identified the binary components to be neutron stars.Gamma-Ray BurstThe Fermi Gamma-Ray Burst Monitor detected a short ( 2-second) gamma-ray burst, GRB170817A, which appears to have occurred 1.7 seconds after the merger indicated by the gravitational-wave signal. This source was later identified by the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) spacecraft as well.Locations of the many observatories that observed the neutron-star merger first detected on 17 August, 2017. [Abbott et al. 2017]Electromagnetic Counterpart and Host GalaxyThough they were initially foiled by the signals location (the localized region of GW170817 only became visible in Chile 10 hours after its detection), the One-Meter, Two-Hemisphere team used the Swope telescope at Las Campanas Observatory in Chile to discover an optical counterpart to the LIGO and Fermi detection, located in the early-type galaxy NGC 4993. Within an hour, five other teams had independently detected the optical source in NGC 4993, with more following after.In the subsequent hours, days, and weeks, observatories across the electromagnetic spectrum monitored the transient. The source soon faded from view in the ultraviolet and gradually reddened in the optical and infrared bands. Delayed X-ray emission was discovered 9 days after the LIGO signal, and a radio counterpart was discovered a week after that.No NeutrinosThough several neutrino observatories searched for high-energy neutrinos in the direction of NGC 4993 in the two-week period following the merger, none were detected.Summary and timeline of the observations of the neutron-star merger detected on 17 August, 2017 relative to the time tc of the gravitational-wave event. Click for a closer look. [Abbott et al. 2017]A Spectacular ConfirmationSo what do these observations tell us? Our model for neutron-star mergers appears to be remarkably successful! The associated detections of gravitational waves and electromagnetic counterparts have confirmed that merging neutron stars produce the expected gravitational-wave signal, that they are the source of gamma-ray bursts, that some of the heaviest elements in the universe are produced during the collision of these stars, and that jets of high-energy particles are created that subsequently interact with their environment.As with any interesting scientific discovery, new points of exploration have arisen we can now wonder why the gamma-ray burst was unusually weak given its close distance, for instance, or why we didnt detect any neutrinos from the outflow.In spite of our new questions, the combination of these recent discoveries provide a resounding verification of our understanding of how compact objects merge. The various signals that began on 17 August, 2017 have simultaneously confirmed a stack of carefully constructed theories that were crafted over decades to explain how seemingly unrelated electromagnetic signals might all tie together. Its a beautiful thing when science works out this well!For more information, check out the ApJL Focus Issue on this result here:Focus on The Electromagnetic Counterpart of the Neutron Star Binary Merger GW170817 CitationAbbott, B.P. et al 2017 ApJL 848 L12. doi:10.3847/2041-8213/aa91c9

Un Détecteur de Neutrons pour la Spectrométrie de Masses Manquantes

NASA Astrophysics Data System (ADS)

Bollini, D.; Buhler-Broglin, A.; Dalpiaz, P.; Massam, T.; Navach, F.; Navarria, F. L.; Schneegans, M. A.; Zichichi, A.

A large (2 × 0.39 m3 plastic scintillator) neutron detector capable to measure with high accuracy the coordinates of the neutron interaction point as well as its time-of-flight is described. As a missing mass spectrometer, it allows to observe for example the η, meson with a mass resolution of ± 4.2 MeV. Nous décrivous un détectcur de neutrons de grand volume sensible (2 x 0,39 m3 de scintillatcur plastique) capable de mesurer avec précision les coordonnées du point d'interaction du neutron détecté ainsi que son temp-de-vol. Employé comme spectrométre de masses manquantes, it permet d'observer par exemple le méson η avec une resolution de ± 4,2 MeY.

New precision measurements of free neutron beta decay with cold neutrons

DOE PAGES

Baeßler, Stefan; Bowman, James David; Penttilä, Seppo I.; ...

2014-10-14

Precision measurements in free neutron beta decay serve to determine the coupling constants of beta decay, and offer several stringent tests of the standard model. This study describes the free neutron beta decay program planned for the Fundamental Physics Beamline at the Spallation Neutron Source at Oak Ridge National Laboratory, and finally puts it into the context of other recent and planned measurements of neutron beta decay observables.

3D target array for pulsed multi-sourced radiography

DOEpatents

Le Galloudec, Nathalie Joelle

2016-02-23

The various technologies presented herein relate to the generation of x-rays and other charged particles. A plurality of disparate source materials can be combined on an array to facilitate fabrication of co-located mixed tips (point sources) which can be utilized to form a polychromatic cloud, e.g., a plurality of x-rays having a range of energies and or wavelengths, etc. The tips can be formed such that the x-rays are emitted in a direction different to other charged particles to facilitate clean x-ray sourcing. Particles, such as protons, can be directionally emitted to facilitate generation of neutrons at a secondary target. The various particles can be generated by interaction of a laser irradiating the array of tips. The tips can be incorporated into a plurality of 3D conical targets, the conical target sidewall(s) can be utilized to microfocus a portion of a laser beam onto the tip material.

Spallation radiation effects in materials

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

Mansur, L.K.; Farrell, K.; Wechsler, M.S.

1996-06-01

Spallation refers to the process whereby particles (chiefly neutrons) are ejected from nuclei upon bombardment by high-energy protons. Spallation neutron sources (SNS`s) use these neutrons for neutron scattering and diffraction research, and SNS`s are proposed as the basis for systems for tritium production and transmutation of nuclear waste. Materials in SNS`s are exposed to the incident proton beam (energies typically about 1000 MeV) and to the spallation neutrons (spectrum of energies extending up to about 1000 MeV). By contrast the fission neutrons in nuclear reactors have an average energy of only about 2 MeV, and the neutrons in fusion reactorsmore » would have energies below about 14 MeV. Furthermore, the protons and neutrons in SNS`s for scattering and diffraction research are pulsed at frequencies of about 10 to 60 Hz, from which significant changes in the kinetics of point and extended defects may be expected. In addition, much higher transmutation rates occur in SNS-irradiated materials, On the whole, then, significant differences in microstructural development and macroscopic properties may result upon exposure in SNS systems, as compared with fission and fusion irradiations. In a more general sense, subjecting materials to new radiation environments has almost routinely led to new discoveries. To the extent that data are avaiable, however, the spallation environment appears to increase the degree of damage without introducing totally new effects. The first part of this presentation is an overview of radiation effects in materials, outlining essential concepts and property changes and their physical bases. This background is followed by a description of SNS irradiation environments and the effects on materials of exposure to these environments. A special discussion is given of the selection of target (e.g., liquid mercury), container (e.g., austenitic stainless steel or ferritic/martensitic steel), and structural materials in SNS systems.« less

Preliminary skyshine calculations for the Poloidal Diverter Tokamak Experiment

NASA Astrophysics Data System (ADS)

Nigg, D. W.; Wheeler, F. J.

1981-01-01

A calculational model is presented to estimate the radiation dose, due to the skyshine effect, in the control room and at the site boundary of the Poloidal Diverter Experiment (PDX) facility at Princeton University which requires substantial radiation shielding. The required composition and thickness of a water-filled roof shield that would reduce this effect to an acceptable level is computed, using an efficient one-dimensional model with an Sn calculation in slab geometry. The actual neutron skyshine dose is computed using a Monte Carlo model with the neutron source at the roof surface obtained from the slab Sn calculation, and the capture gamma dose is computed using a simple point-kernel single-scatter method. It is maintained that the slab model provides the exact probability of leakage out the top surface of the roof and that it is nearly as accurate as and much less costly than multi-dimensional techniques.

Preliminary skyshine calculations for the Poloidal Diverter Tokamak Experiment

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

Nigg, D.W.; Wheeler, F.J.

1981-01-01

A calculational model is presented to estimate the radiation dose, due to the skyshine effect, in the control room and at the site boundary of the Poloidal Diverter Experiment (PDX) facility at Princeton University which requires substantial radiation shielding. The required composition and thickness of a water-filled roof shield that would reduce this effect to an acceptable level is computed, using an efficient one-dimensional model with an Sn calculation in slab geometry. The actual neutron skyshine dose is computed using a Monte Carlo model with the neutron source at the roof surface obtained from the slab Sn calculation, and themore » capture gamma dose is computed using a simple point-kernel single-scatter method. It is maintained that the slab model provides the exact probability of leakage out the top surface of the roof and that it is nearly as accurate as and much less costly than multi-dimensional techniques.« less

Lanthanide/Actinide Opacities

NASA Astrophysics Data System (ADS)

Hungerford, Aimee; Fontes, Christopher J.

2018-06-01

Gravitational wave observations benefit from accompanying electromagnetic signals in order to accurately determine the sky positions of the sources. The ejecta of neutron star mergers are expected to produce such electromagnetic transients, called macronovae (e.g. the recent and unprecedented observation of GW170817). Characteristics of the ejecta include large velocity gradients and the presence of heavy r-process elements, which pose significant challenges to the accurate calculation of radiative opacities and radiation transport. Opacities include a dense forest of bound-bound features arising from near-neutral lanthanide and actinide elements. Here we present an overview of current theoretical opacity determinations that are used by neutron star merger light curve modelers. We will touch on atomic physics and plasma modeling codes that are used to generate these opacities, as well as the limited body of laboratory experiments that may serve as points of validation for these complex atomic physics calculations.

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

McMillan, Kyle; Marleau, Peter; Brubaker, Erik

In coded aperture imaging, one of the most important factors determining the quality of reconstructed images is the choice of mask/aperture pattern. In many applications, uniformly redundant arrays (URAs) are widely accepted as the optimal mask pattern. Under ideal conditions, thin and highly opaque masks, URA patterns are mathematically constructed to provide artifact-free reconstruction however, the number of URAs for a chosen number of mask elements is limited and when highly penetrating particles such as fast neutrons and high-energy gamma-rays are being imaged, the optimum is seldom achieved. In this case more robust mask patterns that provide better reconstructed imagemore » quality may exist. Through the use of heuristic optimization methods and maximum likelihood expectation maximization (MLEM) image reconstruction, we show that for both point and extended neutron sources a random mask pattern can be optimized to provide better image quality than that of a URA.« less

Search for old neutron stars in molecular clouds: Cygnus rift and Cygnus OB7.

NASA Astrophysics Data System (ADS)

Belloni, T.; Zampieri, L.; Campana, S.

1997-03-01

We present the results of a systematic search for old isolated neutron stars (ONSs) in the direction of two giant molecular clouds in Cygnus (Rift and OB7). From theoretical calculations, we expect the detection of a large number of ONSs with the PSPC on board ROSAT. By analyzing the PSPC pointings in the direction of the clouds, we find four sources characterized by count rates (~10^-3^ct/s) and spectral properties consistent with the hypothesis that the X-ray radiation is produced by ONSs and also characterized by the absence of any measurable optical counterpart within their error circle in the digitized red plates of the Palomar All Sky Survey. The importance of follow-up deep observations in the direction of these ONS candidates is discussed. The observational and theoretical approach presented here could be fruitfully applied also to the systematic search for ONSs in other regions of the Galaxy.

SU-F-T-657: In-Room Neutron Dose From High Energy Photon Beams

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

Christ, D; Ding, G

Purpose: To estimate neutron dose inside the treatment room from photodisintegration events in high energy photon beams using Monte Carlo simulations and experimental measurements. Methods: The Monte Carlo code MCNP6 was used for the simulations. An Eberline ESP-1 Smart Portable Neutron Detector was used to measure neutron dose. A water phantom was centered at isocenter on the treatment couch, and the detector was placed near the phantom. A Varian 2100EX linear accelerator delivered an 18MV open field photon beam to the phantom at 400MU/min, and a camera captured the detector readings. The experimental setup was modeled in the Monte Carlomore » simulation. The source was modeled for two extreme cases: a) hemispherical photon source emitting from the target and b) cone source with an angle of the primary collimator cone. The model includes the target, primary collimator, flattening filter, secondary collimators, water phantom, detector and concrete walls. Energy deposition tallies were measured for neutrons in the detector and for photons at the center of the phantom. Results: For an 18MV beam with an open 10cm by 10cm field and the gantry at 180°, the Monte Carlo simulations predict the neutron dose in the detector to be 0.11% of the photon dose in the water phantom for case a) and 0.01% for case b). The measured neutron dose is 0.04% of the photon dose. Considering the range of neutron dose predicted by Monte Carlo simulations, the calculated results are in good agreement with measurements. Conclusion: We calculated in-room neutron dose by using Monte Carlo techniques, and the predicted neutron dose is confirmed by experimental measurements. If we remodel the source as an electron beam hitting the target for a more accurate representation of the bremsstrahlung fluence, it is feasible that the Monte Carlo simulations can be used to help in shielding designs.« less

Modelisation and distribution of neutron flux in radium-beryllium source (226Ra-Be)

NASA Astrophysics Data System (ADS)

Didi, Abdessamad; Dadouch, Ahmed; Jai, Otman

2017-09-01

Using the Monte Carlo N-Particle code (MCNP-6), to analyze the thermal, epithermal and fast neutron fluxes, of 3 millicuries of radium-beryllium, for determine the qualitative and quantitative of many materials, using method of neutron activation analysis. Radium-beryllium source of neutron is established to practical work and research in nuclear field. The main objective of this work was to enable us harness the profile flux of radium-beryllium irradiation, this theoretical study permits to discuss the design of the optimal irradiation and performance for increased the facility research and education of nuclear physics.

METHOD OF PREPARING POLONIUM-BORON SOURCES

DOEpatents

Birden, J.H.

1959-08-01

An improved technique is described for preparation of a polonium-boron neutron source. A selected amount of Po-210 is vaporized into a thin walled nickel container, then the desired amcunt of boron powder is added. After sealing the container, it is heated quickly by induction heating to vaporize the Po-210 and deposit it in the still cool boron powder. The unit is then quickly cooled to prevent revaporization of the Po-210 from the boron. The build-up of neutron emission may be followed by means of a neutron counter in order to terminate the heating at the optimum level of neutron yield.

TORT/MCNP coupling method for the calculation of neutron flux around a core of BWR.

PubMed

Kurosawa, Masahiko

2005-01-01

For the analysis of BWR neutronics performance, accurate data are required for neutron flux distribution over the In-Reactor Pressure Vessel equipments taking into account the detailed geometrical arrangement. The TORT code can calculate neutron flux around a core of BWR in a three-dimensional geometry model, but has difficulties in fine geometrical modelling and lacks huge computer resource. On the other hand, the MCNP code enables the calculation of the neutron flux with a detailed geometry model, but requires very long sampling time to give enough number of particles. Therefore, a TORT/MCNP coupling method has been developed to eliminate the two problems mentioned above in each code. In this method, the TORT code calculates angular flux distribution on the core surface and the MCNP code calculates neutron spectrum at the points of interest using the flux distribution. The coupling method will be used as the DOT-DOMINO-MORSE code system. This TORT/MCNP coupling method was applied to calculate the neutron flux at points where induced radioactivity data were measured for 54Mn and 60Co and the radioactivity calculations based on the neutron flux obtained from the above method were compared with the measured data.

HYSPEC : A CRYSTAL TIME OF FLIGHT HYBRID SPECTROMETER FOR THE SPALLATION NEUTRON SOURCE.

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

SHAPIRO,S.M.; ZALIZNYAK,I.A.

2002-12-30

This document lays out a proposal by the Instrument Development Team (IDT) composed of scientists from leading Universities and National Laboratories to design and build a conceptually new high-flux inelastic neutron spectrometer at the pulsed Spallation Neutron Source (SNS) at Oak Ridge. This instrument is intended to supply users of the SNS and scientific community, of which the IDT is an integral part, with a platform for ground-breaking investigations of the low-energy atomic-scale dynamical properties of crystalline solids. It is also planned that the proposed instrument will be equipped with a polarization analysis capability, therefore becoming the first polarized beammore » inelastic spectrometer in the SNS instrument suite, and the first successful polarized beam inelastic instrument at a pulsed spallation source worldwide. The proposed instrument is designed primarily for inelastic and elastic neutron spectroscopy of single crystals. In fact, the most informative neutron scattering studies of the dynamical properties of solids nearly always require single crystal samples, and they are almost invariably flux-limited. In addition, in measurements with polarization analysis the available flux is reduced through selection of the particular neutron polarization, which puts even more stringent limits on the feasibility of a particular experiment. To date, these investigations have mostly been carried out on crystal spectrometers at high-flux reactors, which usually employ focusing Bragg optics to concentrate the neutron beam on a typically small sample. Construction at Oak Ridge of the high-luminosity spallation neutron source, which will provide intense pulsed neutron beams with time-averaged fluxes equal to those at medium-flux reactors, opens entirely new opportunities for single crystal neutron spectroscopy. Drawing upon experience acquired during decades of studies with both crystal and time-of-flight (TOF) spectrometers, the IDT has developed a conceptual design for a focused-beam, hybrid time-of-flight instrument with a crystal monochromator for the SNS called HYSPEC (an acronym for hybrid spectrometer). The proposed instrument has a potential to collect data more than an order of magnitude faster than existing steady-source spectrometers over a wide range of energy transfer ({h_bar}{omega}) and momentum transfer (Q) space, and will transform the way that data in elastic and inelastic single-crystal spectroscopy are collected. HYSPEC is optimized to provide the highest neutron flux on sample in the thermal and epithermal neutron energy ranges at a good-to-moderate energy resolution. By providing a flux on sample several times higher than other inelastic instruments currently planned for the SNS, the proposed instrument will indeed allow unique ground-breaking measurements, and will ultimately make polarized beam studies at a pulsed spallation source a realistic possibility.« less

Direct detection of albedo neutron decay electrons at the inner edge of the radiation belt and experimental determination of neutron density in near-Earth space

NASA Astrophysics Data System (ADS)

Li, X.; Selesnick, R.; Schiller, Q. A.; Zhang, K.; Zhao, H.; Baker, D. N.; Temerin, M. A.

2017-12-01

The galaxy is filled with cosmic ray particles, mostly protons with kinetic energy above hundreds of mega-electron volts (MeV). Soon after the discovery of Earth's Van Allen radiation belts almost six decades ago, it was recognized that the main source of inner belt protons, with kinetic energies of tens to hundreds of MeV, is Cosmic Ray Albedo Neutron Decay (CRAND). In this process, cosmic rays reaching the upper atmosphere from throughout the galaxy interact with neutral atoms to produce albedo neutrons which, being unstable to 𝛽 decay, are a potential source of geomagnetically trapped protons and electrons. Protons retain most of the neutrons' kinetic energy while the electrons have lower energies, mostly below 1 MeV. The viability of the electron source was, however, uncertain because measurements showed that electron intensity can vary greatly while the neutron decay rate should be almost constant. Recent measurements from the Relativistic Electron and Proton Telescope integrated little experiment (REPTile) onboard the Colorado Student Space Weather Experiment (CSSWE) CubeSat now show that CRAND is the main electron source for the radiation belt near its inner edge, and also contributes to the inner belt elsewhere. Furthermore, measurement of the CRAND electron intensity provides the first experimental determination of the neutron density in near-Earth space, 2x10-9/cm3, confirming earlier theoretical estimates.

ORNL Neutron Sciences Annual Report for 2007

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

Anderson, Ian S; Horak, Charlie M; Counce, Deborah Melinda

2008-07-01

This is the first annual report of the Oak Ridge National Laboratory Neutron Sciences Directorate for calendar year 2007. It describes the neutron science facilities, current developments, and future plans; highlights of the year's activities and scientific research; and information on the user program. It also contains information about education and outreach activities and about the organization and staff. The Neutron Sciences Directorate is responsible for operation of the High Flux Isotope Reactor and the Spallation Neutron Source. The main highlights of 2007 were highly successful operation and instrument commissioning at both facilities. At HFIR, the year began with themore » reactor in shutdown mode and work on the new cold source progressing as planned. The restart on May 16, with the cold source operating, was a significant achievement. Furthermore, measurements of the cold source showed that the performance exceeded expectations, making it one of the world's most brilliant sources of cold neutrons. HFIR finished the year having completed five run cycles and 5,880 MWd of operation. At SNS, the year began with 20 kW of beam power on target; and thanks to a highly motivated staff, we reached a record-breaking power level of 183 kW by the end of the year. Integrated beam power delivered to the target was 160 MWh. Although this is a substantial accomplishment, the next year will bring the challenge of increasing the integrated beam power delivered to 887 MWh as we chart our path toward 5,350 MWh by 2011.« less