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

Thermal-hydraulic simulation of mercury target concepts for a pulsed spallation neutron source

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

Siman-Tov, M.; Wendel, M.; Haines, J.

1996-06-01

The Oak Ridge Spallation Neutron Source (ORSNS) is a high-power, accelerator-based pulsed spallation neutron source being designed by a multi-laboratory team led by Oak Ridge National Laboratory to achieve very high fluxes of neutrons for scientific experiments. The ORSNS is projected to have a 1 MW proton beam upgradable to 5 MW. About 60% of the beam power (1-5 MW, 17-83 kJ/pulse in 0.5 microsec at 60 cps) is deposited in the liquid metal (mercury) target having the dimensions of 65x30x10 cm (about 19.5 liter). Peak steady state power density is about 150 and 785 MW/m{sup 3} for 1 MWmore » and 5 MW beam respectively, whereas peak pulsed power density is as high as 5.2 and 26.1 GW/m{sup 3}, respectively. The peak pulse temperature rise rate is 14 million C/s (for 5 MW beam) whereas the total pulse temperature rise is only 7 C. In addition to thermal shock and materials compatibility, key feasibility issues for the target are related to its thermal-hydraulic performance. This includes proper flow distribution, flow reversals, possible {open_quotes}hot spots{close_quotes} and the challenge of mitigating the effects of thermal shock through possible injection of helium bubbles throughout the mercury volume or other concepts. The general computational fluid dynamics (CFD) code CFDS-FLOW3D was used to simulate the thermal and flow distribution in three preliminary concepts of the mercury target. Very initial CFD simulation of He bubbles injection demonstrates some potential for simulating behavior of He bubbles in flowing mercury. Much study and development will be required to be able to `predict`, even in a crude way, such a complex phenomena. Future direction in both design and R&D is outlined.« less

IPNS upgrade: A feasibility study

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

NONE

1995-04-01

Many of Argonne National Laboratory`s (ANL`s) scientific staff members were very active in R&D work related to accelerator-based spoliation sources in the 1970s and early 1980s. In 1984, the Seitz/Eastman Panel of the National Academy of Sciences reviewed U.S. materials science research facilities. One of the recommendations of this panel was that the United States build a reactor-based steady-state source, the Advanced Neutron Source (ANS), at Oak Ridge National Laboratory. Subsequently, R&D activities related to the design of an accelerator-based source assumed a lower priority. The resumption of pulsed-source studies in this country started simultaneously with design activities in Europemore » aimed at the European Spallation Source (ESS). The European Community funded a workshop in September 1991 to define the parameters of the ESS. Participants in this workshop included both accelerator builders and neutron source users. A consortium of European countries has proposed to build a 5-MW pulsed source, and a feasibility study is currently under way. Soon after the birth of the ESS, a small group at ANL set about bringing themselves up to date on pulsed-source information since 1984 and studied the feasibility of upgrading ANL`s Intense Pulsed Neutron Source (IPNS) to 1 MW by means of a rapidly cycling synchrotron that could be housed, along with its support facilities, in existing buildings. In early 1993, the Kohn panel recommended that (1) design and construction of the ANS should be completed according to the proposed project schedule and (2) development of competitive proposals for cost-effective design and construction of a 1-MW pulsed spallation source should be authorized immediately.« less

Longitudinal space charge compensation at PSR

NASA Astrophysics Data System (ADS)

Neri, Filippo

1998-11-01

The longitudinal space-charge force in neutron spallation source compressor ring or other high intensity proton storage rings can be compensated by introducing an insert in the ring. The effect of the inductor is to cancel all or part of the space charge potential, because it is capacitive. The Proton Storage Ring at Los Alamos National Laboratory is a compressor ring used to produce short pulses of spallation neutrons. Inductive inserts design for space charge compensation at the Los Alamos Proton Storage Ring is described.

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

Abudureyimu, Reheman; Huang, Chunning; Liu, Yun

We report on a first experimental demonstration of locking a doubly-resonant Fabry-Perot cavity to burst-mode picosecond ultraviolet (UV) pulses by using a temperature controlled dispersion compensation method. This technique will eventually enable the intra cavity power enhancement of burst-mode 402.5MHz/50ps UV laser pulses with a MW level peak power required for the laser assisted H- beam stripping experiment at the Spallation Neutron Source.

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.

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.

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

Overview of ten-year operation of the superconducting linear accelerator at the Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Kim, S.-H.; Afanador, R.; Barnhart, D. L.; Crofford, M.; Degraff, B. D.; Doleans, M.; Galambos, J.; Gold, S. W.; Howell, M. P.; Mammosser, J.; McMahan, C. J.; Neustadt, T. S.; Peters, C.; Saunders, J. W.; Strong, W. H.; Vandygriff, D. J.; Vandygriff, D. M.

2017-04-01

The Spallation Neutron Source (SNS) has acquired extensive operational experience of a pulsed proton superconducting linear accelerator (SCL) as a user facility. Numerous lessons have been learned in its first 10 years operation to achieve a stable and reliable operation of the SCL. In this paper, an overview of the SNS SCL design, qualification of superconducting radio frequency (SRF) cavities and ancillary subsystems, an overview of the SNS cryogenic system, the SCL operation including SCL output energy history and downtime statistics, performance stability of the SRF cavities, efforts for SRF cavity performance recovery and improvement at the SNS, and maintenance activities for cryomodules are introduced.

Overview of ten-year operation of the superconducting linear accelerator at the Spallation Neutron Source

DOE PAGES

Kim, Sang-Ho; Afanador, Ralph; Barnhart, Debra L.; ...

2017-02-04

The Spallation Neutron Source (SNS) has acquired extensive operational experience of a pulsed proton superconducting linear accelerator (SCL) as a user facility. Numerous lessons have been learned in its first 10 years operation to achieve a stable and reliable operation of the SCL. In this paper, an overview of the SNS SCL design, qualification of superconducting radio frequency (SRF) cavities and ancillary subsystems, an overview of the SNS cryogenic system, the SCL operation including SCL output energy history and downtime statistics, performance stability of the SRF cavities, efforts for SRF cavity performance recovery and improvement at the SNS, and maintenancemore » activities for cryomodules are introduced.« less

Overview of ten-year operation of the superconducting linear accelerator at the Spallation Neutron Source

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

Kim, Sang-Ho; Afanador, Ralph; Barnhart, Debra L.

The Spallation Neutron Source (SNS) has acquired extensive operational experience of a pulsed proton superconducting linear accelerator (SCL) as a user facility. Numerous lessons have been learned in its first 10 years operation to achieve a stable and reliable operation of the SCL. In this paper, an overview of the SNS SCL design, qualification of superconducting radio frequency (SRF) cavities and ancillary subsystems, an overview of the SNS cryogenic system, the SCL operation including SCL output energy history and downtime statistics, performance stability of the SRF cavities, efforts for SRF cavity performance recovery and improvement at the SNS, and maintenancemore » activities for cryomodules are introduced.« less

Design of the low energy beam transport line for the China spallation neutron source

NASA Astrophysics Data System (ADS)

Li, Jin-Hai; Ouyang, Hua-Fu; Fu, Shi-Nian; Zhang, Hua-Shun; He, Wei

2008-03-01

The design of the China Spallation Neutron Source (CSNS) low-energy beam transport (LEBT) line, which locates between the ion source and the radio-frequency quadrupole (RFQ), has been completed with the TRACE3D code. The design aims at perfect matching, primary chopping, a small emittance growth and sufficient space for beam diagnostics. The line consists of three solenoids, three vacuum chambers, two steering magnets and a pre-chopper. The total length of LEBT is about 1.74 m. This LEBT is designed to transfer 20 mA of H-pulsed beam from the ion source to the RFQ. An induction cavity is adopted as the pre-chopper. The electrostatic octupole steerer is discussed as a candidate. A four-quadrant aperture for beam scraping and beam position monitoring is designed.

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.

The Spallation Neutron Source accelerator system design

NASA Astrophysics Data System (ADS)

Henderson, S.; Abraham, W.; Aleksandrov, A.; Allen, C.; Alonso, J.; Anderson, D.; Arenius, D.; Arthur, T.; Assadi, S.; Ayers, J.; Bach, P.; Badea, V.; Battle, R.; Beebe-Wang, J.; Bergmann, B.; Bernardin, J.; Bhatia, T.; Billen, J.; Birke, T.; Bjorklund, E.; Blaskiewicz, M.; Blind, B.; Blokland, W.; Bookwalter, V.; Borovina, D.; Bowling, S.; Bradley, J.; Brantley, C.; Brennan, J.; Brodowski, J.; Brown, S.; Brown, R.; Bruce, D.; Bultman, N.; Cameron, P.; Campisi, I.; Casagrande, F.; Catalan-Lasheras, N.; Champion, M.; Champion, M.; Chen, Z.; Cheng, D.; Cho, Y.; Christensen, K.; Chu, C.; Cleaves, J.; Connolly, R.; Cote, T.; Cousineau, S.; Crandall, K.; Creel, J.; Crofford, M.; Cull, P.; Cutler, R.; Dabney, R.; Dalesio, L.; Daly, E.; Damm, R.; Danilov, V.; Davino, D.; Davis, K.; Dawson, C.; Day, L.; Deibele, C.; Delayen, J.; DeLong, J.; Demello, A.; DeVan, W.; Digennaro, R.; Dixon, K.; Dodson, G.; Doleans, M.; Doolittle, L.; Doss, J.; Drury, M.; Elliot, T.; Ellis, S.; Error, J.; Fazekas, J.; Fedotov, A.; Feng, P.; Fischer, J.; Fox, W.; Fuja, R.; Funk, W.; Galambos, J.; Ganni, V.; Garnett, R.; Geng, X.; Gentzlinger, R.; Giannella, M.; Gibson, P.; Gillis, R.; Gioia, J.; Gordon, J.; Gough, R.; Greer, J.; Gregory, W.; Gribble, R.; Grice, W.; Gurd, D.; Gurd, P.; Guthrie, A.; Hahn, H.; Hardek, T.; Hardekopf, R.; Harrison, J.; Hatfield, D.; He, P.; Hechler, M.; Heistermann, F.; Helus, S.; Hiatt, T.; Hicks, S.; Hill, J.; Hill, J.; Hoff, L.; Hoff, M.; Hogan, J.; Holding, M.; Holik, P.; Holmes, J.; Holtkamp, N.; Hovater, C.; Howell, M.; Hseuh, H.; Huhn, A.; Hunter, T.; Ilg, T.; Jackson, J.; Jain, A.; Jason, A.; Jeon, D.; Johnson, G.; Jones, A.; Joseph, S.; Justice, A.; Kang, Y.; Kasemir, K.; Keller, R.; Kersevan, R.; Kerstiens, D.; Kesselman, M.; Kim, S.; Kneisel, P.; Kravchuk, L.; Kuneli, T.; Kurennoy, S.; Kustom, R.; Kwon, S.; Ladd, P.; Lambiase, R.; Lee, Y. Y.; Leitner, M.; Leung, K.-N.; Lewis, S.; Liaw, C.; Lionberger, C.; Lo, C. C.; Long, C.; Ludewig, H.; Ludvig, J.; Luft, P.; Lynch, M.; Ma, H.; MacGill, R.; Macha, K.; Madre, B.; Mahler, G.; Mahoney, K.; Maines, J.; Mammosser, J.; Mann, T.; Marneris, I.; Marroquin, P.; Martineau, R.; Matsumoto, K.; McCarthy, M.; McChesney, C.; McGahern, W.; McGehee, P.; Meng, W.; Merz, B.; Meyer, R.; Meyer, R.; Miller, B.; Mitchell, R.; Mize, J.; Monroy, M.; Munro, J.; Murdoch, G.; Musson, J.; Nath, S.; Nelson, R.; Nelson, R.; O`Hara, J.; Olsen, D.; Oren, W.; Oshatz, D.; Owens, T.; Pai, C.; Papaphilippou, I.; Patterson, N.; Patterson, J.; Pearson, C.; Pelaia, T.; Pieck, M.; Piller, C.; Plawski, T.; Plum, M.; Pogge, J.; Power, J.; Powers, T.; Preble, J.; Prokop, M.; Pruyn, J.; Purcell, D.; Rank, J.; Raparia, D.; Ratti, A.; Reass, W.; Reece, K.; Rees, D.; Regan, A.; Regis, M.; Reijonen, J.; Rej, D.; Richards, D.; Richied, D.; Rode, C.; Rodriguez, W.; Rodriguez, M.; Rohlev, A.; Rose, C.; Roseberry, T.; Rowton, L.; Roybal, W.; Rust, K.; Salazer, G.; Sandberg, J.; Saunders, J.; Schenkel, T.; Schneider, W.; Schrage, D.; Schubert, J.; Severino, F.; Shafer, R.; Shea, T.; Shishlo, A.; Shoaee, H.; Sibley, C.; Sims, J.; Smee, S.; Smith, J.; Smith, K.; Spitz, R.; Staples, J.; Stein, P.; Stettler, M.; Stirbet, M.; Stockli, M.; Stone, W.; Stout, D.; Stovall, J.; Strelo, W.; Strong, H.; Sundelin, R.; Syversrud, D.; Szajbler, M.; Takeda, H.; Tallerico, P.; Tang, J.; Tanke, E.; Tepikian, S.; Thomae, R.; Thompson, D.; Thomson, D.; Thuot, M.; Treml, C.; Tsoupas, N.; Tuozzolo, J.; Tuzel, W.; Vassioutchenko, A.; Virostek, S.; Wallig, J.; Wanderer, P.; Wang, Y.; Wang, J. G.; Wangler, T.; Warren, D.; Wei, J.; Weiss, D.; Welton, R.; Weng, J.; Weng, W.-T.; Wezensky, M.; White, M.; Whitlatch, T.; Williams, D.; Williams, E.; Wilson, K.; Wiseman, M.; Wood, R.; Wright, P.; Wu, A.; Ybarrolaza, N.; Young, K.; Young, L.; Yourd, R.; Zachoszcz, A.; Zaltsman, A.; Zhang, S.; Zhang, W.; Zhang, Y.; Zhukov, A.

2014-11-01

The Spallation Neutron Source (SNS) was designed and constructed by a collaboration of six U.S. Department of Energy national laboratories. The SNS accelerator system consists of a 1 GeV linear accelerator and an accumulator ring providing 1.4 MW of proton beam power in microsecond-long beam pulses to a liquid mercury target for neutron production. The accelerator complex consists of a front-end negative hydrogen-ion injector system, an 87 MeV drift tube linear accelerator, a 186 MeV side-coupled linear accelerator, a 1 GeV superconducting linear accelerator, a 248-m circumference accumulator ring and associated beam transport lines. The accelerator complex is supported by ~100 high-power RF power systems, a 2 K cryogenic plant, ~400 DC and pulsed power supply systems, ~400 beam diagnostic devices and a distributed control system handling ~100,000 I/O signals. The beam dynamics design of the SNS accelerator is presented, as is the engineering design of the major accelerator subsystems.

Initial observations of cavitation-induced erosion of liquid metal spallation target vessels at the Spallation Neutron Source

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

McClintock, David A; Riemer, Bernie; Ferguson, Phillip D

2012-01-01

During operation of the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory the mechanical properties of the AISI 316L target module are altered by high-energy neutron and proton radiation. The interior surfaces of the target vessel are also damaged by cavitation-induced erosion, which results from repetitive rapid heating of the liquid mercury by high-energy proton beam pulses. Until recently no observations of cavitation-induced erosion were possible for conditions prototypical to the SNS. Post irradiation examination (PIE) of the first and second operational SNS targets was performed to gain insight into the radiation-induced changes in mechanical properties of the 316Lmore » target material and the extent of cavitation-induced erosion to the target vessel inner surfaces. Observations of cavitation-induced erosion of the first and second operational SNS target modules are presented here, including images of the target vessel interiors and specimens removed from the target beam-entrance regions.« less

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.

In-situ structural integrity evaluation for high-power pulsed spallation neutron source - Effects of cavitation damage on structural vibration

NASA Astrophysics Data System (ADS)

Wan, Tao; Naoe, Takashi; Futakawa, Masatoshi

2016-01-01

A double-wall structure mercury target will be installed at the high-power pulsed spallation neutron source in the Japan Proton Accelerator Research Complex (J-PARC). Cavitation damage on the inner wall is an important factor governing the lifetime of the target-vessel. To monitor the structural integrity of the target vessel, displacement velocity at a point on the outer surface of the target vessel is measured using a laser Doppler vibrometer (LDV). The measured signals can be used for evaluating the damage inside the target vessel because of cyclic loading and cavitation bubble collapse caused by pulsed-beam induced pressure waves. The wavelet differential analysis (WDA) was applied to reveal the effects of the damage on vibrational cycling. To reduce the effects of noise superimposed on the vibration signals on the WDA results, analysis of variance (ANOVA) and analysis of covariance (ANCOVA), statistical methods were applied. Results from laboratory experiments, numerical simulation results with random noise added, and target vessel field data were analyzed by the WDA and the statistical methods. The analyses demonstrated that the established in-situ diagnostic technique can be used to effectively evaluate the structural response of the target vessel.

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

The European scene regarding spallation neutron sources

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

Bauer, G.S.

1996-06-01

In Europe, a short pulse spallation neutron source, ISIS, has been operating for over 10 years, working its way up to a beam power level of 200 kW. A continuous source, SINQ, designed for a beam power of up to 1 MW, is scheduled to start operating at the end of 1996, and a detailed feasibility study has been completed for a 410 kW short pulse source, AUSTRON. Each of these sources seems to have settled for a target concept which is at or near the limits of its feasibility: The ISIS depleted uranium plate targets, heavy water cooled andmore » Zircaloy clad, have so far not shown satisfactory service time and operation is likely to continue with a Ta-plate target, which, in the past has been used successfully for the equivalent of one full-beam-year before it was taken out of service due to degrading thermal properties. SINQ will initially use a rod target, made of Zircaloy only, but plans exist to move on to clad lead rods as quickly as possible. Apart from the not yet explored effect of hydrogen and helium production, there are also concerns about the generation of 7-Be in the cooling water from the spallation of oxygen, which might result in undesirably high radioactivity in the cooling plant room. A Liquid metal target, also under investigation for SINQ, would not only reduce this problem to a level of about 10 %, but would also minimize the risk of radiolytic corrosion in the beam interaction zone. Base on similar arguments, AUSTRON has been designed for edge cooled targets, but thermal and stress analyses show, that this concept is not feasible at higher power levels.« less

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

Generation of negative pressures and spallation phenomena in diamond exposed to a picosecond laser pulse

NASA Astrophysics Data System (ADS)

Abrosimov, S. A.; Bazhulin, A. P.; Bol'shakov, A. P.; Konov, V. I.; Krasyuk, I. K.; Pashinin, P. P.; Ral'chenko, V. G.; Semenov, A. Yu; Sovyk, D. N.; Stuchebryukhov, I. A.; Fortov, V. E.; Khishchenko, K. V.; Khomich, A. A.

2014-06-01

The spallation phenomena in poly- and single-crystal synthetic diamonds have been experimentally investigated. A shockwave impact on a target was implemented using a 70-ps laser pulse in the Kamerton-T facility. The ablation pressure of 0.66 TPa on the front target surface was formed by pulsed radiation of a neodymium phosphate glass laser (second harmonic λ = 0.527 mm, pulse energy 2.5 J) with an intensity as high as 2 × 1013 W cm-2. The maximum diamond spall strength σ* ≈ 16.5 GPa is found to be 24% of the theoretical ultimate strength. Raman scattering data indicate that a small amount of crystalline diamond in the spallation region on the rear side of the target is graphitised.

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

Spallation-induced roughness promoting high spatial frequency nanostructure formation on Cr

NASA Astrophysics Data System (ADS)

Abou-Saleh, A.; Karim, E. T.; Maurice, C.; Reynaud, S.; Pigeon, F.; Garrelie, F.; Zhigilei, L. V.; Colombier, J. P.

2018-04-01

Interaction of ultrafast laser pulses with metal surfaces in the spallation regime can result in the formation of anisotropic nanoscale surface morphology commonly referred to as laser-induced periodic surface structures (LIPSS) or ripples. The surface structures generated by a single pulse irradiation of monocrystalline Cr samples are investigated experimentally and computationally for laser fluences that produce high spatial frequency nanostructures in the multi-pulse irradiation regime. Electron microscopy reveals distinct response of samples with different crystallographic surface orientations, with (100) surfaces exhibiting the formation of more refined nanostructure by a single pulse irradiation and a more pronounced LIPSS after two laser pulses as compared to (110) surfaces. A large-scale molecular dynamics simulation of laser interaction with a (100) Cr target provides detailed information on processes responsible for spallation of a liquid layer, redistribution of molten material, and rapid resolidification of the target. The nanoscale roughness of the resolidified surface predicted in the simulation features elongated frozen nanospikes, nanorims and nanocavities with dimensions and surface density similar to those in the surface morphology observed for (100) Cr target with atomic force microscopy. The results of the simulation suggest that the types, sizes and dimensions of the nanoscale surface features are defined by the competition between the evolution of transient liquid structures generated in the spallation process and the rapid resolidification of the surface region of the target. The spallation-induced roughness is likely to play a key role in triggering the generation of high-frequency LIPSS upon irradiation by multiple laser pulses.

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.

γ-Ray background sources in the VESUVIO spectrometer at ISIS spallation neutron source

NASA Astrophysics Data System (ADS)

Pietropaolo, A.; Perelli Cippo, E.; Gorini, G.; Tardocchi, M.; Schooneveld, E. M.; Andreani, C.; Senesi, R.

2009-09-01

An investigation of the gamma background was carried out in the VESUVIO spectrometer at the ISIS spallation neutron source. This study, performed with a yttrium-aluminum-perovskite (YAP) scintillator, follows high resolution pulse height measurements of the gamma background carried out on the same instrument with the use of a high-purity germanium detector. In this experimental work, a mapping of the gamma background was attempted, trying to find the spatial distribution and degree of directionality of the different contributions identified in the previous study. It is found that the gamma background at low times is highly directional and mostly due to the gamma rays generated in the moderator-decoupler system. The other contributions, consistently to the findings of a previous experiment, are identified as a nearly isotropic one due to neutron absorption in the walls of the experimental hall, and a directional one coming from the beam dump.

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.

Proceedings of the international workshop on the technology and thermal hydraulics of heavy liquid metals (Hg, Pb, Bi, and their eutectics)

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

Appleton, B.R.; Bauer, G.S.

1996-06-01

The International Workshop on the Technology and Thermal Hydraulics of Heavy Liquid Metals (Schruns Workshop) was organized to assess the R&D and technology problems associated with designing and building a heavy liquid metal target for a spallation neutron source. The European scientific community is completing a feasibility study for a future, accelerator-based, pulsed spallation neutron source that would deliver a beam power of 5 megawatts (MW) to a target. They have concluded that a liquid metal target is preferable to conventional solid targets for handling the extreme radiation environments, high heat loads, and pulsed power. Similarly, the ORNL has beenmore » funded by the DOE to design a high-power, pulsed spallation neutron source that would begin operation at about 1 MW but that could be upgraded to significantly higher powers in the future. Again, the most feasible target design appears to be a liquid metal target. Since the expertise needed to consider these problems resides in a number of disparate disciplines not normally covered by existing conferences, this workshop was organized to bring a small number of scientists and engineers together to assess the opportunities for building such a target. The objectives and goals of the Schruns Workshop were to: review and share existing information on the science and technology of heavy liquid metal systems. Evaluate the opportunities and limitations of materials compatibility, thermal hydraulics and heat transfer, chemical reactions, corrosion, radiation effects, liquid-gas mixtures, systems designs, and circuit components for a heavy liquid metal target. Establish the critical R & D and technology that is necessary to construct a liquid metal target. Explore opportunities for cooperative R & D among members of the international community that could expedite results, and share expertise and resources. Selected papers are indexed separately for inclusion in the Energy Science and Technology Database.« less

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.

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.

Development of the front end test stand and vessel for extraction and source plasma analyses negative hydrogen ion sources at the Rutherford Appleton Laboratory.

PubMed

Lawrie, S R; Faircloth, D C; Letchford, A P; Perkins, M; Whitehead, M O; Wood, T; Gabor, C; Back, J

2014-02-01

The ISIS pulsed spallation neutron and muon facility at the Rutherford Appleton Laboratory (RAL) in the UK uses a Penning surface plasma negative hydrogen ion source. Upgrade options for the ISIS accelerator system demand a higher current, lower emittance beam with longer pulse lengths from the injector. The Front End Test Stand is being constructed at RAL to meet the upgrade requirements using a modified ISIS ion source. A new 10% duty cycle 25 kV pulsed extraction power supply has been commissioned and the first meter of 3 MeV radio frequency quadrupole has been delivered. Simultaneously, a Vessel for Extraction and Source Plasma Analyses is under construction in a new laboratory at RAL. The detailed measurements of the plasma and extracted beam characteristics will allow a radical overhaul of the transport optics, potentially yielding a simpler source configuration with greater output and lifetime.

ICANS-XIV. The fourteenth meeting of the international collaboration on advanced neutron sources.

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

Carpenter, J. M., ed.; Tobin, C. A., ed.

1999-02-10

The meeting began with a reception on Sunday evening. Monday's plenary sessions included status reports on the four operating spallation neutron sources, IPNS, ISIS, KENS, and the Lujan Center; on the INR source under construction at Troitsk; on the IBR-2 pulsed reactor at Dubna; and on proposals for five new installations. We also heard reports on spin-off activities: the ASTE tests (liquid mercury target tests at the AGS accelerator at Brookhaven), the ACoM activities (developments aimed to provide cold moderators suitable for high-power pulsed sources), and the International Workshop on Cold Moderators for Pulsed Neutron Sources, held in September 1997more » at Argonne. Jose Alonso and Bob Macek delivered enlightening invited talks overviewing linear accelerators and rings for spallation neutron sources. The rest of the meeting was devoted to targets and moderators and to instrumentation in a normal rotation of ICANS topics. There were altogether 84 oral reports and 23 poster presentations. On Tuesday and on Wednesday morning, we divided into separate series of sessions on Instrumentation and on Targets and Moderators. In the first, we had reports and discussions on instrumentation and techniques, on computer software, on instrument suites, and on new instruments and equipment. In the second series were sessions on liquid target systems, on solid target systems, on neutron production and target physics, on moderator physics and performance, and on target and moderator neutronics. The Tuesday evening meetings went on until 10:00, making for a 14-hour working day. That everyone willingly endured the long hours is a credit to the dedication of the attendees. On Wednesday afternoon, we boarded buses for the 1-hour trip to Argonne, where attendees toured IPNS and the Advanced Photon Source. Returning to Starved Rock, we enjoyed boat rides on the Illinois River and then a barbecue banquet dinner at the Lodge. All day Thursday and Friday morning, the attendees, in small working groups, discussed next-generation powder diffractometers, critical heat flux limitations on solid targets, monte carlo instrument simulation, prospects for high- and low-energy spectroscopy, small angle scattering and reflectometry, and the roles of solid and liquid targets in high-power pulsed spallation sources. Representatives of the laboratories participating in ICANS met Thursday evening to discuss the outcome of ICANS XIV and to decide whether, where, and when the next meeting would take place. They agreed to meet again in about 2 years in Japan. After the lunch break on Friday, the working group chairs presented the findings of their groups to the participants in a final plenary session, and the meeting adjourned with good feelings of accomplishment.« less

The National Spallation Neutron Source Target Station.

NASA Astrophysics Data System (ADS)

Gabriel, T. A.

1997-05-01

The technologies that are being utilized to design and build a state-of-the-art high powered (>= 1 MW), short pulsed (<= 1 μsec), and reliable spallation neutron source target station are discussed. The protons which directly and indirectly produce the neutrons will be obtained from a 1 GeV proton accelerator composed of an ion gun, rfq, linac, and storage ring. Many scientific and technical disciplines are required to produce a successful target station. These disciplines include engineering, remote handling, neutronics, materials, thermal hydraulics, shock analysis, etc. In the areas of engineering and remote handling special emphasis is being given to rapid and efficient assembly and disassembly of critical parts of the target station. In the neutronics area, emphasis is being given to neutron yield and pulse optimization from the moderators, and heating and activation rates throughout the station. Development of structural materials to withstand aggressive radiation environments and that are compatible with other materials is also an important area. Thermal hydraulics and shock analysis are being closely studied since large amounts of energy are being deposited in small volumes in relatively short time periods (< 1 μsec). These areas will be expanded upon in the paper.

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.

Fiber Optic Picosecond Laser Pulse Transmission Line for Hydrogen Ion Beam Profile Measurement

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

Liu, Yun; Huang, Chunning; Aleksandrov, Alexander V

2013-01-01

We present a fiber optic laser pulse transmission line for non-intrusive longitudinal profile measurement of the hydrogen ion (H-) beam at the front-end of the Spallation Neutron Source (SNS) accelerator. The 80.5 MHz, 2.5 ps, multi-killowatt optical pulses are delivered to the accelerator beam line through a large mode area polarization maintaining optical fiber to ensure a high measurement stability. The transmission efficiency, output laser beam quality, pulse jitter and pulse width broadening over a 100-ft fiber line are experimentally investigated. A successful measurement of the H- beam microbunch (~130 ps) profile is obtained. Our experiment is the first demonstrationmore » of particle beam profile diagnostics using fiber optic laser pulse transmission line.« 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.

Core Vessel Insert Handling Robot for the Spallation Neutron Source

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

Graves, Van B; Dayton, Michael J

2011-01-01

The Spallation Neutron Source provides the world's most intense pulsed neutron beams for scientific research and industrial development. Its eighteen neutron beam lines will eventually support up to twenty-four simultaneous experiments. Each beam line consists of various optical components which guide the neutrons to a particular instrument. The optical components nearest the neutron moderators are the core vessel inserts. Located approximately 9 m below the high bay floor, these inserts are bolted to the core vessel chamber and are part of the vacuum boundary. They are in a highly radioactive environment and must periodically be replaced. During initial SNS construction,more » four of the beam lines received Core Vessel Insert plugs rather than functional inserts. Remote replacement of the first Core Vessel Insert plug was recently completed using several pieces of custom-designed tooling, including a highly complicated Core Vessel Insert Robot. The design of this tool are discussed.« less

A target development program for beamhole spallation neutron sources in the megawatt range

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

Bauer, G.S.; Atchison, F.

1995-10-01

Spallation sources as an alternative to fission neutron sources have been operating successfully up to 160 kW of beam power. With the next generation of these facilities aiming at the medium power range between 0.5 and 5 MW, loads on the targets will be high enough to make present experience of little relevance. With the 0.6 MW continuous facility SINQ under construction, and a 5 MW pulsed facility (ESS) under study in Europe, a research and development program is about to be started which aimes at assessing the limits of stationary and moving solid targets and the feasibility and potentialmore » benefits of flowing liquid metal targets. Apart from theoretical work and examination of existing irradiated material, including used targets from ISIS, it is intended to take advantage of the SINQ solid rod target design to improve the relevant data base by building the target in such a way that individual rods can be equipped as irradiation capsules.« less

Deformation dynamics and spallation strength of aluminium under a single-pulse action of a femtosecond laser

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

Ashitkov, Sergei I; Komarov, P S; Ovchinnikov, A V

An interferometric method is developed and realised using a frequency-modulated pulse for diagnosing a dynamics of fast deformations with a spatial and temporal resolution under the action of a single laser pulse. The dynamics of a free surface of a submicron-thick aluminium film is studied under an action of the ultrashort compression pulse with the amplitude of up to 14 GPa, excited by a femtosecond laser heating of the target surface layer. The spallation strength of aluminium was determined at a record high deformation rate of 3 Multiplication-Sign 10{sup 9} s{sup -1}. (extreme light fields and their applications)

Negative pressures and spallation in water drops subjected to nanosecond shock waves

DOE PAGES

Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.; ...

2016-05-16

Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below –100 MPamore » were reached in the drops. As a result, we model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.« less

Conceptual design of the time-of-flight backscattering spectrometer MIRACLES, at the European Spallation Source

NASA Astrophysics Data System (ADS)

Tsapatsaris, N.; Lechner, R. E.; Markó, M.; Bordallo, H. N.

2016-08-01

In this work, we present the conceptual design of the backscattering time-of-flight spectrometer MIRACLES approved for construction at the long-pulse European Spallation Source (ESS). MIRACLES's unparalleled combination of variable resolution, high flux, extended energy, and momentum transfer (0.2-6 Å-1) ranges will open new avenues for neutron backscattering spectroscopy. Its remarkable flexibility can be attributed to 3 key elements: the long-pulse time structure and low repetition rate of the ESS neutron source, the chopper cascade that tailors the moderator pulse in the primary part of the spectrometer, and the bent Si(111) analyzer crystals arranged in a near-backscattering geometry in the secondary part of the spectrometer. Analytical calculations combined with instrument Monte-Carlo simulations show that the instrument will provide a variable elastic energy resolution, δ(ħ ω), between 2 and 32 μeV, when using a wavelength of λ ≈ 6.267 Å (Si(111)-reflection), with an energy transfer range, ħ ω, centered at the elastic line from -600 to +600 μeV. In addition, when selecting λ ≈ 2.08 Å (i.e., the Si(333)-reflection), δ(ħ ω) can be relaxed to 300 μeV and ħ ω from about 10 meV in energy gain to ca -40 meV in energy loss. Finally, the dynamic wavelength range of MIRACLES, approximately 1.8 Å, can be shifted within the interval of 2-20 Å to allow the measurement of low-energy inelastic excitations.

Conceptual design of the time-of-flight backscattering spectrometer, MIRACLES, at the European Spallation Source.

PubMed

Tsapatsaris, N; Lechner, R E; Markó, M; Bordallo, H N

2016-08-01

In this work, we present the conceptual design of the backscattering time-of-flight spectrometer MIRACLES approved for construction at the long-pulse European Spallation Source (ESS). MIRACLES's unparalleled combination of variable resolution, high flux, extended energy, and momentum transfer (0.2-6 Å(-1)) ranges will open new avenues for neutron backscattering spectroscopy. Its remarkable flexibility can be attributed to 3 key elements: the long-pulse time structure and low repetition rate of the ESS neutron source, the chopper cascade that tailors the moderator pulse in the primary part of the spectrometer, and the bent Si(111) analyzer crystals arranged in a near-backscattering geometry in the secondary part of the spectrometer. Analytical calculations combined with instrument Monte-Carlo simulations show that the instrument will provide a variable elastic energy resolution, δ(ħ ω), between 2 and 32 μeV, when using a wavelength of λ ≈ 6.267 Å (Si(111)-reflection), with an energy transfer range, ħ ω, centered at the elastic line from -600 to +600 μeV. In addition, when selecting λ ≈ 2.08 Å (i.e., the Si(333)-reflection), δ(ħ ω) can be relaxed to 300 μeV and ħ ω from about 10 meV in energy gain to ca -40 meV in energy loss. Finally, the dynamic wavelength range of MIRACLES, approximately 1.8 Å, can be shifted within the interval of 2-20 Å to allow the measurement of low-energy inelastic excitations.

Mercury target R&D for the Oak Ridge spallation neutron source

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

Haines, J.R.; DiStefano, J.; Farrell, K.

1996-06-01

The conceptual design for the Oak Ridge Spallation Neutron Source (ORSNS) incorporates liquid mercury as its reference target material. A flowing liquid target was selected mainly because of the increased power handling capability possible with the convective transport process. The major reasons for choosing mercury as the liquid target material are because it: (1) is a liquid at room temperature, (2) has good heat transport properties, and (3) has a high atomic number and mass density resulting in high neutron yield and source brightness. Since liquid targets are not widely utilized in presently operating accelerator targets and because of themore » challenges posed by the intense, pulsed thermal energy deposition ({approximately}20-100 kJ deposited during each 1-10 {mu}s pulse), considerable R&D is planned for the mercury target concept. The key feasibility issue that will be addressed in early R&D efforts are the effects of the thermal shock environment, which will include development and testing of approaches to mitigate these effects. Materials compatiblity and ES&H issues associated with the use of liquid mercury are also of major importance in early R&D efforts. A brief description of the mercury target design concept, results of initial evaluations of its performance characteristics, identification of its critical issues, and an outline of the R&D program aimed at addressing these issues will be presented.« less

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.

Applications of a micro-pixel chamber (μPIC) based, time-resolved neutron imaging detector at pulsed neutron beams

NASA Astrophysics Data System (ADS)

Parker, J. D.; Harada, M.; Hattori, K.; Iwaki, S.; Kabuki, S.; Kishimoto, Y.; Kubo, H.; Kurosawa, S.; Matsuoka, Y.; Miuchi, K.; Mizumoto, T.; Nishimura, H.; Oku, T.; Sawano, T.; Shinohara, T.; Suzuki, J.-I.; Takada, A.; Tanimori, T.; Ueno, K.; Ikeno, M.; Tanaka, M.; Uchida, T.

2014-04-01

The realization of high-intensity, pulsed spallation neutron sources such as J-PARC in Japan and SNS in the US has brought time-of-flight (TOF) based neutron techniques to the fore and spurred the development of new detector technologies. When combined with high-resolution imaging, TOF-based methods become powerful tools for direct imaging of material properties, including crystal structure/internal strain, isotopic/temperature distributions, and internal and external magnetic fields. To carry out such measurements in the high-intensities and high gamma backgrounds found at spallation sources, we have developed a new time-resolved neutron imaging detector employing a micro-pattern gaseous detector known as the micro-pixel chamber (μPIC) coupled with a field-programmable-gate-array-based data acquisition system. The detector combines 100μm-level (σ) spatial and sub-μs time resolutions with low gamma sensitivity of less than 10-12 and a rate capability on the order of Mcps (mega-counts-per-second). Here, we demonstrate the application of our detector to TOF-based techniques with examples of Bragg-edge transmission and neutron resonance transmission imaging (with computed tomography) carried out at J-PARC. We also consider the direct imaging of magnetic fields with our detector using polarized neutrons.

Influence of deposited nanoparticles on the spall strength of metals under the action of picosecond pulses of shock compression

NASA Astrophysics Data System (ADS)

Ebel, A. A.; Mayer, A. E.

2018-01-01

Molecular dynamic simulations of the generation and propagation of shock pulses of picosecond duration initiated by nanoscale impactors, and their interaction with the rear surface is carried out for aluminum and copper. It is shown that the presence of deposited nanoparticles on the rear surface increases the threshold value of the impact intensity leading to the rear spallation. The interaction of a shock wave with nanoparticles leads to severe plastic deformation in the surface layer of the metal including nanoparticles. A part of the compression pulse energy is expended on the plastic deformation, which suppresses the spall fracture. Spallation threshold substantially increases at large diameters of deposited nanoparticles, but instability develops on the rear surface of the target, which is accompanied by ejection of droplets. The instability disrupts the integrity of the rear surface, though the loss of integrity occurs through the ejection of mass, rather than a spallation.

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.

Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

DOE PAGES

Gallmeier, F. X.; Lu, W.; Riemer, B. W.; ...

2016-06-14

We identified candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared tomore » the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm 2 to 20 × 20 mm 2. Furthermore, this increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. Our first effort decoupled group moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.« less

Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

NASA Astrophysics Data System (ADS)

Gallmeier, F. X.; Lu, W.; Riemer, B. W.; Zhao, J. K.; Herwig, K. W.; Robertson, J. L.

2016-06-01

Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm2 to 20 × 20 mm2. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments' sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.

Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

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

Gallmeier, F. X.; Lu, W.; Riemer, B. W.

We identified candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared tomore » the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm 2 to 20 × 20 mm 2. Furthermore, this increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. Our first effort decoupled group moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.« less

Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

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

Gallmeier, F. X., E-mail: gallmeierfz@ornl.gov; Lu, W.; Riemer, B. W.

Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis comparedmore » to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm{sup 2} to 20 × 20 mm{sup 2}. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.« less

New controller for high voltage converter modulator at spallation neutron source

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

Wezensky, Mark W; Brown, David L; Lee, Sung-Woo

2017-01-01

The Spallation Neutron Source (SNS) has developed a new control system for the High Voltage Convertor Modulator (HVCM) at the SNS to replace the original control system which is approaching obsolescence. The original system was based on controllers for similar high voltage systems that were already in use [1]. The new controller, based on National Instruments PXI/FlexRIO Field Programmable Gate Array (FPGA) platform, offers enhancements such as modular construction, flexibility and non-proprietary software. The new controller also provides new capabilities like various methods for modulator pulse flattening, waveform capture, and first fault detection. This paper will discuss the design ofmore » the system, including the human machine interface, based on lessons learned at the SNS and other projects. It will also discuss performance and other issues related to its operation in an accelerator facility which requires high availability. To date, 73% of the operational HVCMs have been upgraded to with the new controller, and the remainder are scheduled for completion by mid-2017.« less

The CENNS-10 liquid argon detector to measure CEvNS at the Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Tayloe, R.

2018-04-01

The COHERENT collaboration is deploying a suite of low-energy detectors in a low-background corridor of the ORNL Spallation Neutron Source (SNS) to measure coherent elastic neutrino-nucleus scattering (CEvNS) on an array of nuclear targets employing different detector technologies. A measurement of CEvNS on different nuclei will test the N2-dependence of the CEvNS cross section and further the physics reach of the COHERENT effort. The first step of this program has been realized recently with the observation of CEvNS in a 14.6 kg CsI detector. Operation and deployment of Ge and NaI detectors are also underway. A 22 kg, single-phase, liquid argon detector (CENNS-10) started data-taking in Dec. 2016 and will provide results on CEvNS from a lighter nucleus. Initial results indicate that light output, pulse-shape discrimination, and background suppression are sufficient for a measurement of CEvNS on argon.

Comparison of different target material options for the European Spallation Source based on certain aspects related to the final disposal

NASA Astrophysics Data System (ADS)

Kókai, Zsófia; Török, Szabina; Zagyvai, Péter; Kiselev, Daniela; Moormann, Rainer; Börcsök, Endre; Zanini, Luca; Takibayev, Alan; Muhrer, Günter; Bevilacqua, Riccardo; Janik, József

2018-02-01

Different target options have been examined for the European Spallation Source, which is under construction in Lund, Sweden. During the design update phase, parameters and characteristics for the target design have been optimized not only for neutronics but also with respect to the waste characteristics related to the final disposal of the target. A rotating, solid tungsten target was eventually selected as baseline concept; the other options considered included mercury and lead-bismuth (LBE) targets suitable for a pulsed source. Since the licensee is obliged to present a decommissioning plan even before the construction phase starts, the radioactive waste category of the target after full operation time is of crucial importance. The results obtained from a small survey among project partners of 7th Framework Program granted by EU 202247 contract have been used. Waste characteristics of different potential spallation target materials were compared. Based on waste index, the tungsten target is the best alternative and the second one is the mercury target. However, all alternatives have HLW category after a 10 year cooling. Based on heat generation alone all of the options would be below the HLW limit after this cooling period. The LBE is the least advantageous alternative based on waste index and heat generation comparison. These results can be useful in compiling the licensing documents of the ESS facility as the target alternatives can be compared from various aspects related to their disposal.

Molecular dynamics simulation of shock wave and spallation phenomena in metal foils irradiated by femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Zhakhovsky, Vasily; Demaske, Brian; Inogamov, Nail; Oleynik, Ivan

2010-03-01

Femtosecond laser irradiation of metals is an effective technique to create a high-pressure frontal layer of 100-200 nm thickness. The associated ablation and spallation phenomena can be studied in the laser pump-probe experiments. We present results of a large-scale MD simulation of ablation and spallation dynamics developing in 1,2,3μm thick Al and Au foils irradiated by a femtosecond laser pulse. Atomic-scale mechanisms of laser energy deposition, transition from pressure wave to shock, reflection of the shock from the rear-side of the foil, and the nucleation of cracks in the reflected tensile wave, having a very high strain rate, were all studied. To achieve a realistic description of the complex phenomena induced by strong compression and rarefaction waves, we developed new embedded atom potentials for Al and Au based on cold pressure curves. MD simulations revealed the complex interplay between spallation and ablation processes: dynamics of spallation depends on the pressure profile formed in the ablated zone at the early stage of laser energy absorption. It is shown that the essential information such as material properties at high strain rate and spall strength can be extracted from the simulated rear-side surface velocity as a function of time.

Space charge tune shift, fast resonance traversal, and current limits in circular accelerators

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

Rees, G.H.

1996-06-01

Space charge tune shifts, fast resonance traversals, and current limits are important design issues for low energy, high power circular accelerators. Areas of interest are accumulator rings and fast cycling synchrotrons, and typical applications are for pulsed spallation neutron sources, heavy ion fusion storage ring drivers, and booster injectors for high energy proton and ion facilities. Aspects of the three topics are discussed in the paper. {copyright} {ital 1996 American Institute of Physics.}

Laser and optical system for laser assisted hydrogen ion beam stripping at SNS

DOE PAGES

Liu, Y.; Rakhman, A.; Menshov, A.; ...

2016-12-01

A high-efficiency laser assisted hydrogen ion (H-) beam stripping was recently successfully carried out in the Spallation Neutron Source (SNS) accelerator. The experiment was not only an important step toward foil-less H- stripping for charge exchange injection, it also set up a first example of using megawatt ultraviolet (UV) laser source in an operational high power proton accelerator facility. This study reports in detail the design, installation, and commissioning result of a macro-pulsed multi-megawatt UV laser system and laser beam transport line for the laser stripping experiment.

Laser and optical system for laser assisted hydrogen ion beam stripping at SNS

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

Liu, Y.; Rakhman, A.; Menshov, A.

A high-efficiency laser assisted hydrogen ion (H-) beam stripping was recently successfully carried out in the Spallation Neutron Source (SNS) accelerator. The experiment was not only an important step toward foil-less H- stripping for charge exchange injection, it also set up a first example of using megawatt ultraviolet (UV) laser source in an operational high power proton accelerator facility. This study reports in detail the design, installation, and commissioning result of a macro-pulsed multi-megawatt UV laser system and laser beam transport line for the laser stripping experiment.

Cavitation damage prediction for spallation target vessels by assessment of acoustic vibration

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

Futakawa, Masatoshi; Kogawa, Hiroyuki; Hasegawa, Shoichi

2008-01-01

Liquid-mercury target systems for MW-class spallation neutron sources are being developed around the world. Proton beams are used to induce the spallation reaction. At the moment the proton beam hits the target, pressure waves are generated in the 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. In order to estimate the cavitation erosion, i.e. the pitting damage formed by the collapse of cavitation bubbles, off-beam tests were performed by using an electric magnetic impact testing machine (MIMTM), which can impose equivalentmore » pressure pulses in mercury. The damage potential was defined based on the relationship between the pitting damage and the time-integrated acoustic vibration induced by impact due to the bubble collapses. Additionally, the damage potential was measured in on-beam tests carried out by using the proton beam at WNR (Weapons Neutron Research) facility in Los Alamos Neutron Science Center (LANSCE). In this paper, the concept of the damage potential, the relationship between the pitting damage formation and the damage potential both in off-beam and on-beam tests is shown.« less

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.

HIGH POWER BEAM DUMP AND TARGET / ACCELERATOR INTERFACE PROCEDURES

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

Blokland, Willem; Plum, Michael A; Peters, Charles C

Satisfying operational procedures and limits for the beam target interface is a critical concern for high power operation at spallation neutron sources. At the Oak Ridge Spallation Neutron Source (SNS) a number of protective measures are instituted to ensure that the beam position, beam size and peak intensity are within acceptable limits at the target and high power Ring Injection Dump (RID). The high power beam dump typically handles up to 50 100 kW of beam power and its setup is complicated by the fact that there are two separate beam components simultaneously directed to the dump. The beam onmore » target is typically in the 800-1000 kW average power level, delivered in sub- s 60 Hz pulses. Setup techniques using beam measurements to quantify the beam parameters at the target and dump will be described. However, not all the instrumentation used for the setup and initial qualification is available during high power operation. Additional techniques are used to monitor the beam during high power operation to ensure the setup conditions are maintained, and these are also described.« less

H(-) ion source developments at the SNS.

PubMed

Welton, R F; Stockli, M P; Murray, S N; Pennisi, T R; Han, B; Kang, Y; Goulding, R H; Crisp, D W; Sparks, D O; Luciano, N P; Carmichael, J R; Carr, J

2008-02-01

The U.S. Spallation Neutron Source (SNS) will require substantially higher average and pulse H(-) beam currents than can be produced from conventional ion sources such as the base line SNS source. H(-) currents of 40-50 mA (SNS operations) and 70-100 mA (power upgrade project) with a rms emittance of 0.20-0.35pi mm mrad and a approximately 7% duty factor will be needed. We are therefore investigating several advanced ion source concepts based on rf plasma excitation. First, the performance characteristics of an external antenna source based on an Al(2)O(3) plasma chamber combined with an external multicusp magnetic configuration, an elemental Cs system, and plasma gun will be discussed. Second, the first plasma measurements of a helicon-driven H(-) ion source will also be presented.

H- ion source developments at the SNSa)

NASA Astrophysics Data System (ADS)

Welton, R. F.; Stockli, M. P.; Murray, S. N.; Pennisi, T. R.; Han, B.; Kang, Y.; Goulding, R. H.; Crisp, D. W.; Sparks, D. O.; Luciano, N. P.; Carmichael, J. R.; Carr, J.

2008-02-01

The U.S. Spallation Neutron Source (SNS) will require substantially higher average and pulse H- beam currents than can be produced from conventional ion sources such as the base line SNS source. H- currents of 40-50mA (SNS operations) and 70-100mA (power upgrade project) with a rms emittance of 0.20-0.35πmmmrad and a ˜7% duty factor will be needed. We are therefore investigating several advanced ion source concepts based on rf plasma excitation. First, the performance characteristics of an external antenna source based on an Al2O3 plasma chamber combined with an external multicusp magnetic configuration, an elemental Cs system, and plasma gun will be discussed. Second, the first plasma measurements of a helicon-driven H- ion source will also be presented.

Specific features of single-pulse femtosecond laser micron and submicron ablation of a thin silver film coated with a micron-thick photoresist layer

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

Zayarnyi, D A; Ionin, A A; Kudryashov, S I

Specific features of ablation of a thin silver film with a 1-μm-thick layer of a highly transparent photoresist and the same film without a photoresist layer under single tightly focused femtosecond laser pulses in the visible range (515 nm) are experimentally investigated. Interference effects of internal modification of the photoresist layer, its spallation ablation from the film surface and formation of through hollow submicron channels in the resist without its spallation but with ablation of the silver film lying under the resist are found and discussed. (extreme light fields and their applications)

Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement

DOE PAGES

Rakhman, Abdurahim; Wang, Yang; Garcia, Frances; ...

2014-01-01

A compact optical correlator system that measures both the autocorrelation between two infrared (IR) lights and the cross-correlation between an IR and an ultraviolet (UV) light using a single nonlinear optical crystal has been designed and experimentally demonstrated. The rapid scanning of optical delay line, switching between auto and cross-correlations, crystal angle tuning, and data acquisition and processing are all computer controlled. Pulse widths of an IR light from a mode-locked laser are measured by the correlator and the results are compared with a direct measurement using a high-speed photodetector system. The correlator has been used to study the parametermore » dependence of the pulse width of a macropulse UV laser designed for laser-assisted hydrogen ion (H-) beam stripping for the Spallation Neutron Source at Oak Ridge National Laboratory.« less

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.

The effects of shockwave profile shape and shock obliquity on spallation in Cu and Ta: kinetic and stress-state effects on damage evolution(u)

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

Gray, George T

2010-12-14

Widespread research over the past five decades has provided a wealth of experimental data and insight concerning shock hardening and the spallation response of materials subjected to square-topped shock-wave loading profiles. Less quantitative data have been gathered on the effect of direct, in-contact, high explosive (HE)-driven Taylor wave (or triangular-wave) loading profile shock loading on the shock hardening, damage evolution, or spallation response of materials. Explosive loading induces an impulse dubbed a 'Taylor Wave'. This is a significantly different loading history than that achieved by a square-topped impulse in terms of both the pulse duration at a fixed peak pressure,more » and a different unloading strain rate from the peak Hugoniot state achieved. The goal of this research is to quantify the influence of shockwave obliquity on the spallation response of copper and tantalum by subjecting plates of each material to HE-driven sweeping detonation-wave loading and quantify both the wave propagation and the post-mortem damage evolution. This talk will summarize our current understanding of damage evolution during sweeping detonation-wave spallation loading in Cu and Ta and show comparisons to modeling simulations. The spallation responses of Cu and Ta are both shown to be critically dependent on the shockwave profile and the stress-state of the shock. Based on variations in the specifics of the shock drive (pulse shape, peak stress, shock obliquity) and sample geometry in Cu and Ta, 'spall strength' varies by over a factor of two and the details of the mechanisms of the damage evolution is seen to vary. Simplistic models of spallation, such as P{sub min} based on 1-D square-top shock data lack the physics to capture the influence of kinetics on damage evolution such as that operative during sweeping detonation loading. Such considerations are important for the development of predictive models of damage evolution and spallation in metals and alloys.« less

A compact 10 kW solid-state RF power amplifier at 352 MHz

NASA Astrophysics Data System (ADS)

Dancila, Dragos; Hoang Duc, Long; Jobs, Magnus; Holmberg, Måns; Hjort, Adam; Rydberg, Anders; Ruber, Roger

2017-07-01

A compact 10 kW RF power amplifier at 352 MHz was developed at FREIA for the European Spallation Source, ESS. The specifications of ESS for the conception of amplifiers are related to its pulsed operation: 3.5 ms pulse length and a duty cycle of 5%. The realized amplifier is composed of eight kilowatt level modules, combined using a planar Gysel 8-way combiner. The combiner has a low insertion loss of only 0.2 dB, measured at 10 kW peak power. Each module is built around a commercially available LDMOS transistor in a singleended architecture. During the final tests, a total output peak power of 10.5 kW was measured.

New opportunities in quasi elastic neutron scattering spectroscopy

NASA Astrophysics Data System (ADS)

Mezei, F.; Russina, M.

2001-07-01

The high energy resolution usually required in quasi elastic neutron scattering (QENS) spectroscopy is commonly achieved by the use of cold neutrons. This is one of the important research areas where the majority of current work is done on instruments on continuous reactor sources. One particular reason for this is the capability of continuous source time-of-flight spectrometers to use instrumental parameters optimally adapted for best data collection efficiency in each experiment. These parameters include the pulse repetition rate and the length of the pulses to achieve optimal balance between resolution and intensity. In addition, the disc chopper systems used provide perfect symmetrical line shapes with no tails and low background. Recent development of a set of novel techniques enhance the efficiency of cold neutron spectroscopy on existing and future spallation sources in a dramatic fashion. These techniques involve the use of extended pulse length, high intensity coupled moderators, disc chopper systems and advanced neutron optical beam delivery, and they will enable Lujan center at Los Alamos to surpass the best existing reactor instruments in time-of-flight QENS work by more than on order of magnitude in terms of beam flux on the sample. Other applications of the same techniques will allow us to combine advantages of backscattering spectroscopy on continuous and pulsed sources in order to deliver μeV resolution in a very broad energy transfer range.

A high-rate 10B-loaded liquid scintillation detector for parity-violation studies in neutron resonances

NASA Astrophysics Data System (ADS)

Yen, Yi-Fen; Bowman, J. D.; Bolton, R. D.; Crawford, B. E.; Delheij, P. P. J.; Hart, G. W.; Haseyama, T.; Frankle, C. M.; Iinuma, M.; Knudson, J. N.; Masaike, A.; Masuda, Y.; Matsuda, Y.; Mitchell, G. E.; Penttilä, S. I.; Roberson, N. R.; Seestrom, S. J.; Sharapov, E.; Shimizu, H. M.; Smith, D. A.; Stephenson, S. L.; Szymanski, J. J.; Yoo, S. H.; Yuan, V. W.

2000-06-01

We have developed a large-area 10B-loaded liquid scintillation detector for parity-violation studies in neutron resonances with high instantaneous neutron fluxes from the LANSCE short-pulse spallation source. The detector has an efficiency of 95%, 85% and 71% at neutron energies of 10, 100 and 1000 eV, respectively. The neutron mean capture time in the detector is (416±5) ns. We describe the detector and the current-mode signal processing system, that can handle neutron rates up to 500 MHz.

Determination of the axial-vector weak coupling constant with ultracold neutrons.

PubMed

Liu, J; Mendenhall, M P; Holley, A T; Back, H O; Bowles, T J; Broussard, L J; Carr, R; Clayton, S; Currie, S; Filippone, B W; García, A; Geltenbort, P; Hickerson, K P; Hoagland, J; Hogan, G E; Hona, B; Ito, T M; Liu, C-Y; Makela, M; Mammei, R R; Martin, J W; Melconian, D; Morris, C L; Pattie, R W; Pérez Galván, A; Pitt, M L; Plaster, B; Ramsey, J C; Rios, R; Russell, R; Saunders, A; Seestrom, S J; Sondheim, W E; Tatar, E; Vogelaar, R B; VornDick, B; Wrede, C; Yan, H; Young, A R

2010-10-29

A precise measurement of the neutron decay β asymmetry A₀ has been carried out using polarized ultracold neutrons from the pulsed spallation ultracold neutron source at the Los Alamos Neutron Science Center. Combining data obtained in 2008 and 2009, we report A₀ = -0.119 66±0.000 89{-0.001 40}{+0.001 23}, from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon g{A}/g{V}=-1.275 90{-0.004 45}{+0.004 09}.

Small Gas Bubble Experiment for Mitigation of Cavitation Damage and Pressure Waves in Short-pulse Mercury Spallation Targets

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

Wendel, Mark W; Felde, David K; Sangrey, Robert L

2014-01-01

Populations of small helium gas bubbles were introduced into a flowing mercury experiment test loop to evaluate mitigation of beam-pulse induced cavitation damage and pressure waves. The test loop was developed and thoroughly tested at the Spallation Neutron Source (SNS) prior to irradiations at the Los Alamos Neutron Science Center - Weapons Neutron Research Center (LANSCE-WNR) facility. Twelve candidate bubblers were evaluated over a range of mercury flow and gas injection rates by use of a novel optical measurement technique that accurately assessed the generated bubble size distributions. Final selection for irradiation testing included two variations of a swirl bubblermore » provided by Japan Proton Accelerator Research Complex (J-PARC) collaborators and one orifice bubbler developed at SNS. Bubble populations of interest consisted of sizes up to 150 m in radius with achieved gas void fractions in the 10^-5 to 10^-4 range. The nominal WNR beam pulse used for the experiment created energy deposition in the mercury comparable to SNS pulses operating at 2.5 MW. Nineteen test conditions were completed each with 100 pulses, including variations on mercury flow, gas injection and protons per pulse. The principal measure of cavitation damage mitigation was surface damage assessment on test specimens that were manually replaced for each test condition. Damage assessment was done after radiation decay and decontamination by optical and laser profiling microscopy with damaged area fraction and maximum pit depth being the more valued results. Damage was reduced by flow alone; the best mitigation from bubble injection was between half and a quarter that of flow alone. Other data collected included surface motion tracking by three laser Doppler vibrometers (LDV), loop wall dynamic strain, beam diagnostics for charge and beam profile assessment, embedded hydrophones and pressure sensors, and sound measurement by a suite of conventional and contact microphones.« less

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

Peplov, Vladimir V; Saethre, Robert B

The Spallation Neutron Source (SNS) Linac Low Energy Beam Transport (LEBT) chopper system provides fast chopping of the H- ion beam in the LEBT structure. Four identical pulsed power supplies (pulsers) create a series of 2.5 kV pulses to the four deflection electrodes floating on the focusing voltage of -50 kV. Each pulser is connected to the electrode through the network which consists of high voltage (HV) cables, a blocking capacitor, HV feed-through connectors, current-limiting resistors and transient voltage suppressors. Effective beam chopping requires minimal rise/fall time of the rectangular HV pulses on the load. In the present configuration thesemore » values are approximately 100 ns. Methods of reducing rise/fall time on the LEBT electrodes are discussed. Results of simulation and comparative measurements of the original and upgraded system on the test stand are presented. Furthermore, the effect of these changes on reliability degradation caused by arcing in the LEBT structure is discussed.« less

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

Hurd, Alan J; Rhyne, James J; Lewis, Paul S

This two-day workshop will engage the international neutron scattering community to vet and improve the Lujan Center Strategic Plan 2007-2013 (SP07). Sponsored by the LANL SC Program Office and the University of California, the workshop will be hosted by LANSCE Professor Sunny Sinha (UCSD). Endorsement by the Spallation Neutron Source will be requested. The discussion will focus on the role that the Lujan Center will play in the national neutron scattering landscape assuming full utilization of beamlines, a refurbished LANSCE, and a 1.4-MW SNS. Because the Lujan Strategic Plan is intended to set the stage for the Signature Facility eramore » at LANSCE, there will be some discussion of the long-pulse spallation source at Los Alamos. Breakout groups will cover several new instrument concepts, upgrades to present instruments, expanded sample environment capabilities, and a look to the future. The workshop is in keeping with a request by BES to update the Lujan strategic plan in coordination with the SNS and the broader neutron community. Workshop invitees will be drawn from the LANSCE User Group and a broad cross section of the US, European, and Pacific Rim neutron scattering research communities.« less

Narrow linewidth picosecond UV pulsed laser with mega-watt peak power.

PubMed

Huang, Chunning; Deibele, Craig; Liu, Yun

2013-04-08

We demonstrate a master oscillator power amplifier (MOPA) burst mode laser system that generates 66 ps/402.5 MHz pulses with mega-watt peak power at 355 nm. The seed laser consists of a single frequency fiber laser (linewidth < 5 KHz), a high bandwidth electro-optic modulator (EOM), a picosecond pulse generator, and a fiber based preamplifier. A very high extinction ratio (45 dB) has been achieved by using an adaptive bias control of the EOM. The multi-stage Nd:YAG amplifier system allows a uniformly temporal shaping of the macropulse with a tunable pulse duration. The light output from the amplifier is converted to 355 nm, and over 1 MW peak power is obtained when the laser is operating in a 5-μs/10-Hz macropulse mode. The laser output has a transform-limited spectrum with a very narrow linewidth of individual longitudinal modes. The immediate application of the laser system is the laser-assisted hydrogen ion beam stripping for the Spallation Neutron Source (SNS).

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

Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.

Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below –100 MPamore » were reached in the drops. As a result, we model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.« less

Condensed-matter research at the Los Alamos pulsed neutron source (WNR)

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

Eckert, J.

1982-01-01

The experimental program at the WNR in condensed matter research at present is aimed principally at utilizing the high epithermal neutron flux available at a spallation neutron source. Interesting new results have been obtained in several areas including hydrogen vibrations in metals, chemical vibrational spectroscopy and the structure of liquids. For example, extensive vibrational spectra were obtained of hydrogen in Nb which could be described in terms of a three-dimensional localized anharmonic oscillator, deuterium substitution methods were used to determine the variation with 0-0 distance of the hydrogen bending mode frequency in extremely short intramolecular hydrogen bonds, and model-independent partialmore » structure factors were determined for liquid water.« less

Self-healing effect of spallation damageability

NASA Astrophysics Data System (ADS)

Buravova, S. N.

2017-10-01

The self-healing effect has been found in a study of the microstructure of the bands of localized deformation. It has been shown that interstitial elements (O, C) and the particles of a doping phase migrate to the zone of growing spallation damageability from the matrix material. When considering the wave pattern of the process of localization, it has been ascertained that the formation of bands of localized deformation is accompanied by the process of reverberation which is characterized by the formation of periodically repeated compression-extension cycles. A weak attenuation of the reverberation has led to an increase in the duration of the deformation pulse of the sample by two to three orders of magnitude compared with the time of the initial compression pulse.

Development of a 33 kV, 20 A long pulse converter modulator for high average power klystron

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

Reghu, T.; Mandloi, V.; Shrivastava, Purushottam

Research, design, and development of high average power, long pulse modulators for the proposed Indian Spallation Neutron Source are underway at Raja Ramanna Centre for Advanced Technology. With this objective, a prototype of long pulse modulator capable of delivering 33 kV, 20 A at 5 Hz repetition rate has been designed and developed. Three Insulated Gate Bipolar Transistors (IGBT) based switching modules driving high frequency, high voltage transformers have been used to generate high voltage output. The IGBT based switching modules are shifted in phase by 120° with respect to each other. The switching frequency is 25 kHz. Pulses ofmore » 1.6 ms pulse width, 80 μs rise time, and 70 μs fall time have been achieved at the modulator output. A droop of ±0.6% is achieved using a simple segmented digital droop correction technique. The total fault energy transferred to the load during fault has been measured by conducting wire burn tests and is found to be within 3.5 J.« less

Development of a 33 kV, 20 A long pulse converter modulator for high average power klystron

NASA Astrophysics Data System (ADS)

Reghu, T.; Mandloi, V.; Shrivastava, Purushottam

2014-05-01

Research, design, and development of high average power, long pulse modulators for the proposed Indian Spallation Neutron Source are underway at Raja Ramanna Centre for Advanced Technology. With this objective, a prototype of long pulse modulator capable of delivering 33 kV, 20 A at 5 Hz repetition rate has been designed and developed. Three Insulated Gate Bipolar Transistors (IGBT) based switching modules driving high frequency, high voltage transformers have been used to generate high voltage output. The IGBT based switching modules are shifted in phase by 120° with respect to each other. The switching frequency is 25 kHz. Pulses of 1.6 ms pulse width, 80 μs rise time, and 70 μs fall time have been achieved at the modulator output. A droop of ±0.6% is achieved using a simple segmented digital droop correction technique. The total fault energy transferred to the load during fault has been measured by conducting wire burn tests and is found to be within 3.5 J.

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

Sns Moderator Poison Design and Experiment Validation of the Moderator Performance

NASA Astrophysics Data System (ADS)

Lu, W.; Iverson, E. B.; Ferguson, P. D.; Crabtree, J. A.; Gallmeier, F. X.; Remec, I.; Baxter, D. V.; Lavelle, C. M.

2009-08-01

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory reached 180 kW in August 2007, becoming the brightest pulsed neutron source in the world. At its full power of 1.4 MW, SNS will have thermal neutron fluxes approximately an order of magnitude greater than any existing pulsed spallation source. It thus brings a serious challenge to the lifetime of the moderator poison sheets. The SNS moderators are integrated with the inner reflector plug (IRP) at a cost of $2 million a piece. A replacement of the IRP presents a significant drawback to the facility due to the activation and the operation cost. Although there are many factors limiting the lifetime of the IRP, such as radiation damage to the structural material and helium production in beryllium, the limiting factor is the lifetime of the moderator poison sheets. The current operating target system of SNS was built with thick Gd poison sheets at a projected lifetime of 3 years. A recent design based on the MCNPX calculation proposed to replace the Gd poison sheets with even thicker Cd poison sheets, aiming to extend the poison sheet lifetime from 3 to 4 years accompanied by an approximate 5% gain of the moderator performance. An experiment was carried out to verify the calculated moderator performance at the Low Energy Neutron Source (LENS), Indiana University, where the spectra of two polyethylene moderators were measured. The moderators are Cd-decoupled and are poisoned with 0.8 mm Gd and 1.2 mm Cd, respectively. The preliminary analysis of the experiment data shows that the characteristics of the measured spectra of the Gd- and Cd-poisoned moderators agree well with what the calculation predicted. A better moderator performance is observed in the Cd-poisoned moderator. The measured ratio of Cd over Gd on the moderator performance is in a reasonable agreement with the calculation. Further investigation is underway for a better understanding of the difference between the experiment and the calculation.

European Neutrons form Parasitic Research to Global Strategy: Realizing Plans for a Transnational European Spallation Source in the Wake of the Cold War

NASA Astrophysics Data System (ADS)

Kaiserfeld, Thomas

2016-03-01

Studies of Big Science have early on focused on instrumentation and scientific co-operation in large organizations, later on to take into account symbolic values and specific research styles while more recently also involving the relevance of commercial interests and economic development as well as the assimilation of research traditions. In accordance with these transformed practices, this presentation will analyze how an organization with the purpose of realizing a Big-Science facility, The European Spallation Source, has successfully managed to present the project as relevant to different national and international policy-makers, to the community of European neutron researchers as well as to different industrial interests. All this has been achieved in a research-policy environment, which has been the subject to drastic transformations, from calls to engage researchers from the former eastern bloc in the early 1990s via competition with American and Asian researchers at the turn of the century 2000 to intensified demands on business applications. During this process, there has also been fierce competition between different potential sites in the U.K., Germany, Spain, Hungary and Sweden, not once, but twice. The project has in addition been plagued by withdrawals of key actors as well as challenging problems in the field of spallation-source construction. Nevertheless, the European Spallation Source has survived from the early 1990s until today, now initiating the construction process at Lund in southern Sweden. In this presentation, the different measures taken and arguments raised by the European Spallation Source project in order to realize the facility will be analysed. Especially the different designs of the European Spallation Source will be analysed as responses to external demands and threats.

Beam modulation: A novel ToF-technique for high resolution diffraction at the Beamline for European Materials Engineering Research (BEER)

NASA Astrophysics Data System (ADS)

Rouijaa, M.; Kampmann, R.; Šaroun, J.; Fenske, J.; Beran, P.; Müller, M.; Lukáš, P.; Schreyer, A.

2018-05-01

The Beamline for European Materials Engineering Research (BEER) is under construction at the European Spallation Source (ESS) in Lund, Sweden. A basic requirement on BEER is to make best use of the long ESS pulse (2.86 ms) for engineering investigations. High-resolution diffraction, however, demands timing resolution up to 0.1% corresponding to a pulse length down to about 70 μs for the case of thermal neutrons (λ ∼ 1.8 Å). Such timing resolution can be achieved by pulse shaping techniques cutting a short section out of the long pulse, and thus paying for resolution by strong loss of intensity. In contrast to this, BEER proposes a novel operation mode called pulse modulation technique based on a new chopper design, which extracts several short pulses out of the long ESS pulse, and hence leads to a remarkable gain of intensity compared to nowadays existing conventional pulse shaping techniques. The potential of the new technique can be used with full advantage for investigating strains and textures of highly symmetric materials. Due to its instrument design and the high brilliance of the ESS pulse, BEER is expected to become the European flagship for engineering research for strain mapping and texture analysis.

Performance of the LANSCE H^- Source and Low Energy Transport at Higher Peak Current

NASA Astrophysics Data System (ADS)

Pillai, Chandra; Stevens, Ralph; Fitzgerald, Daniel; Garnett, Robert; Ingllas, William; Merrill, Frank; Rybarcyk, Larry; Sander, Oscar

1997-05-01

The Los Alamos Neutron Science Center (LANSCE) 800 MeV linac facility uses a multicusp field, surface ion source to produce H^- beam for delivery to the Proton Storage Ring (PSR) and to the Weapon Neutron Research (WNR) areas. The source typically operates at a duty factor of 9.4% delivering a peak current of about 14 mA into the 750 keV LEBT. Each beam macropulse is chopped to create a sequence of 360 ns pulse, each with a 100 ns ``extraction notch'' for injection into PSR. The average current delivered to the short-pulse spallation target is nominally 70μA. One goal of the present PSR upgrade projects is an increase in the average beam current to 200μA. This will be accomplished by a combination of increased repetition rate (to 30 Hz), upgraded PSR bunchers, and a brighter H^- ion source that will produce higher peak current with lower beam emittance. The present ion source and injector system was studied to investigate the beam qualities of the source and the performance of the low energy transpot. The performance of the ion source at higher currents and the change in beam parameters in the low energy transport compared to those in the standard source conditions will be presented.

Surface plasma source with saddle antenna radio frequency plasma generator.

PubMed

Dudnikov, V; Johnson, R P; Murray, S; Pennisi, T; Piller, C; Santana, M; Stockli, M; Welton, R

2012-02-01

A prototype RF H(-) surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA∕kW. Control experiments with H(-) beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.

H- radio frequency source development at the Spallation Neutron Source.

PubMed

Welton, R F; Dudnikov, V G; Gawne, K R; Han, B X; Murray, S N; Pennisi, T R; Roseberry, R T; Santana, M; Stockli, M P; Turvey, M W

2012-02-01

The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent ∼38 mA peak current in the linac and an availability of ∼90%. H(-) beam pulses (∼1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, ∼60 kW) of a copper antenna that has been encased with a thickness of ∼0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of ∼99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of ∼75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance∕installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to ∼100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.

Detection of supernova neutrinos at spallation neutron sources

NASA Astrophysics Data System (ADS)

Huang, Ming-Yang; Guo, Xin-Heng; Young, Bing-Lin

2016-07-01

After considering supernova shock effects, Mikheyev-Smirnov-Wolfenstein effects, neutrino collective effects, and Earth matter effects, the detection of supernova neutrinos at the China Spallation Neutron Source is studied and the expected numbers of different flavor supernova neutrinos observed through various reaction channels are calculated with the neutrino energy spectra described by the Fermi-Dirac distribution and the “beta fit” distribution respectively. Furthermore, the numerical calculation method of supernova neutrino detection on Earth is applied to some other spallation neutron sources, and the total expected numbers of supernova neutrinos observed through different reactions channels are given. Supported by National Natural Science Foundation of China (11205185, 11175020, 11275025, 11575023)

Pressure waves in liquid mercury target from pulsed heat loads and the possible way controlling their effects

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

Ni, L.; Skala, K.

1996-06-01

In ESS project liquid metals are selected as the main target for the pulsed spallation neutron source. Since the very high instantaneous energy is deposited on the heavy molten target in a very short period time, pressure waves are generated. They travel through the liquid and cause high stress in the container. Also, additional stress should be considered in the wall which is the result of direct heating of the target window. These dynamic processes were simulated with computational codes with the static response being analized first. The total resulting dynamic wall stress has been found to have exceeded themore » design stress for the selected container material. Adding a small amount of gas bubbles in the liquid could be a possible way to reduce the pressure waves.« less

Lorentz Force Detuning Analysis of the SNS Accelerating Cavities

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

R. Mitchell; K. Matsumoto; G. Ciovati

2001-09-01

The Spallation Neutron Source (SNS) project incorporates a superconducting radio-frequency (SRF) accelerator for the final section of the pulsed mode linac Cavities with geometrical {beta} values of {beta} = 0.61 and {beta} = 0.81 are utilized in the SRF section, and are constructed out of thin-walled niobium with stiffener rings welded between the cells near the iris. The welded titanium helium vessel and tuner assembly restrains the cavity beam tubes Cavities with {beta} values less than one have relatively steep and flat side-walls making the cavities susceptible to Ised RF induces cyclic Lorentz pressures that mechanically excite the cavities, producingmore » a dynamic Lorentz force detuning different from a continuous RF system. The amplitude of the dynamic detuning for a given cavity design is a function of the mechanical damping, stiffness of the tuner/helium vessel assembly, RF pulse profile, and the RF pulse rate. This paper presents analysis and testing results to date, and indicates areas where more investigation is required.« less

Higher Order Mode Analysis of the SNS Superconducting Linac

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

M. Doleans; D. Jeon; S. Kim

2001-06-01

Higher order modes (HOM's) of monopoles, dipoles, quadrupoles and sextupoles in {beta} = 0.61 and {beta} = 0.81 6-cell superconducting (SC) cavities for the Spallation Neutron Source (SNS) project, have been found up to about 3 GHz and their properties such as R/Q, trapping possibility, etc have been figured out in concerning with the manufacturing imperfection. Main issues of HOM's are beam instabilities (published separately) and HOM induced power especially from TM monopoles. The time structure of SNS beam has three different time scales of pulses, which are micro-pulse, midi-pulse and macropulse. Each time structure will generate resonances. When amore » mode is near these resonance frequencies, the induced voltage could be large and accordingly the resulting HOM power, too. In order to understand the effects from such a complex beam time structure on the mode excitation and resulting HOM power, analytic expressions are developed. With these analytic expressions, the induced HOM voltage and HOM power were calculated by assuming external Q for each HOM.« less

The ESS neutrino facility for CP violation discovery

NASA Astrophysics Data System (ADS)

Baussan, Eric; Bouquerel, Elian; Dracos, Marcos

2017-09-01

The comparatively large value of the neutrino mixing angle θ 13 measured in 2012 by neutrino reactor experiments has opened the possibility to observe for the first time CP violation in the leptonic sector. The measured value of θ 13 also privileges the 2nd oscillation maximum for the discovery of CP violation instead of the usually used 1st oscillation maximum. The sensitivity at the 2nd oscillation maximum is about three times higher than at the 1st oscillation maximum implying a significantly lower sensitivity to systematic errors. Measuring at the 2nd oscillation maximum necessitates a very intense neutrino beam with the appropriate energy. The world’s most intense pulsed spallation neutron source, the European Spallation Source, has a proton linac with 5 MW power and 2 GeV energy. This linac also has the potential to become the proton driver of the world’s most intense neutrino beam with very high potential for the discovery of neutrino CP violation. The physics performance of that neutrino Super Beam in conjunction with a megaton Water Cherenkov neutrino detector installed ca 1000 m down in a mine at a distance of about 500 km from ESS has been evaluated. In addition, the use of such a detector will make it possible to extent the physics program to proton decay, atmospheric neutrinos and astrophysics searches. The ESS proton linac upgrade, the accumulator ring needed for proton pulse compression, the target station optimization and the physics potential are described. In addition to the production of neutrinos, this facility will also be a copious source of muons which could be used to feed a low energy nuSTORM facility, a future neutrino factory or a muon collider. The ESS linac, under construction, will reach full operation at 5 MW by 2023 after which the upgrades for the neutrino facility could start.

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

Fedrigo, Anna, E-mail: anna.fedrigo@nbi.ku.dk; Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche, 50019 Sesto Fiorentino; European Spallation Source ESS AB, SE-221 00 Lund

VESPA, Vibrational Excitation Spectrometer with Pyrolytic-graphite Analysers, aims to probe molecular excitations via inelastic neutron scattering. It is a thermal high resolution inverted geometry time-of-flight instrument designed to maximise the use of the long pulse of the European Spallation Source. The wavelength frame multiplication technique was applied to provide simultaneously a broad dynamic range (about 0-500 meV) while a system of optical blind choppers allows to trade flux for energy resolution. Thanks to its high flux, VESPA will allow the investigation of dynamical and in situ experiments in physical chemistry. Here we describe the design parameters and the corresponding McStasmore » simulations.« less

Introduction to spallation physics and spallation-target design

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

Russell, G.J.; Pitcher, E.J.; Daemen, L.L.

1995-10-01

When coupled with the spallation process in appropriate target materials, high-power accelerators can be used to produce large numbers of neutrons, thus providing an alternate method to the use of nuclear reactors for this purpose. Spallation offers exciting new possibilities for generating intense neutron fluxes for a variety of applications, including: (a) spallation-neutron sources for materials science research; (b) accelerator-based production of tritium; (c) accelerator-based transmutation of waste; (d) accelerator-based destruction of plutonium; and (e) radioisotope production for medical and energy applications. Target design plays a key role in these applications, with neutron production/leakage being strongly dependent on the incidentmore » particle type and energy, and target material and geometry.« less

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

Laser lift-off scribing of the CZTSe thin-film solar cells at different pulse durations

DOE PAGES

Markauskas, Edgaras; Gečys, Paulius; Repins, Ingrid; ...

2017-04-27

Here, the transition to fully sized solar modules requires additional three-step laser structuring processes to preserve small-scale cell efficiencies over the large areas. The adjacent cell isolation (the P3 scribe) was found to be the most sensitive process in the case of laser induced damage. The laser induced layer lift-off mechanism seems to be a very attractive process for the P3 patterning, since almost all the laser affected material is removed by mechanical spallation. However, a laser induced layer spallation behavior together with scribe electrical validation under the different laser pulse durations was not investigated extensively in the past. Therefore,more » we report our novel results on the P2 and P3 laser lift-off processing of the Cu 2ZnSn(S, Se 4) (CZTSe) thin-film solar cells covering the pulse duration range from 300 fs to 60 ps. Shorter sub-ps pulses enabled us to process smaller P2 and P3 craters, although the lift-off threshold fluences were higher compared to the longer ps pulses. In the case of the layer lift-off, the laser radiation had to penetrate through the layer stack down to the CZTSe/Mo interface. At shorter sub-ps pulses, the nonlinear effects triggered absorption of the laser radiation in the bulk of the material, resulting in increased damage of the CZTSe layer. The Raman measurements confirmed the CZTSe surface stoichiometry changes for shorter pulses. Furthermore, shorter pulses induced higher electrical conductivity of a scribe, resulting in lower photo-electrical efficiency during the mini-module simulation. In the case of the P3 lift-off scribing, the 10 ps pulses were more favorable than shorter femtosecond pulses.« less

Laser lift-off scribing of the CZTSe thin-film solar cells at different pulse durations

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

Markauskas, Edgaras; Gečys, Paulius; Repins, Ingrid

Here, the transition to fully sized solar modules requires additional three-step laser structuring processes to preserve small-scale cell efficiencies over the large areas. The adjacent cell isolation (the P3 scribe) was found to be the most sensitive process in the case of laser induced damage. The laser induced layer lift-off mechanism seems to be a very attractive process for the P3 patterning, since almost all the laser affected material is removed by mechanical spallation. However, a laser induced layer spallation behavior together with scribe electrical validation under the different laser pulse durations was not investigated extensively in the past. Therefore,more » we report our novel results on the P2 and P3 laser lift-off processing of the Cu 2ZnSn(S, Se 4) (CZTSe) thin-film solar cells covering the pulse duration range from 300 fs to 60 ps. Shorter sub-ps pulses enabled us to process smaller P2 and P3 craters, although the lift-off threshold fluences were higher compared to the longer ps pulses. In the case of the layer lift-off, the laser radiation had to penetrate through the layer stack down to the CZTSe/Mo interface. At shorter sub-ps pulses, the nonlinear effects triggered absorption of the laser radiation in the bulk of the material, resulting in increased damage of the CZTSe layer. The Raman measurements confirmed the CZTSe surface stoichiometry changes for shorter pulses. Furthermore, shorter pulses induced higher electrical conductivity of a scribe, resulting in lower photo-electrical efficiency during the mini-module simulation. In the case of the P3 lift-off scribing, the 10 ps pulses were more favorable than shorter femtosecond pulses.« less

H- Ion Sources for High Intensity Proton Drivers

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

Johnson, Rolland Paul; Dudnikov, Vadim

2015-02-20

Existing RF Surface Plasma Sources (SPS) for accelerators have specific efficiencies for H + and H - ion generation around 3 to 5 mA/cm 2 per kW, where about 50 kW of RF power is typically needed for 50 mA beam current production. The Saddle Antenna (SA) SPS described here was developed to improve H- ion production efficiency, reliability and availability for pulsed operation as used in the ORNL Spallation Neutron Source . At low RF power, the efficiency of positive ion generation in the plasma has been improved to 200 mA/cm 2 per kW of RF power at 13.56more » MHz. Initial cesiation of the SPS was performed by heating cesium chromate cartridges by discharge as was done in the very first versions of the SPS. A small oven to decompose cesium compounds and alloys was developed and tested. After cesiation, the current of negative ions to the collector was increased from 1 mA to 10 mA with RF power 1.5 kW in the plasma (6 mm diameter emission aperture) and up to 30 mA with 4 kW RF power in the plasma and 250 Gauss longitudinal magnetic field. The ratio of electron current to negative ion current was improved from 30 to 2. Stable generation of H- beam without intensity degradation was demonstrated in the aluminum nitride (AlN) discharge chamber for 32 days at high discharge power in an RF SPS with an external antenna. Some modifications were made to improve the cooling and cesiation stability. The extracted collector current can be increased significantly by optimizing the longitudinal magnetic field in the discharge chamber. While this project demonstrated the advantages of the pulsed version of the SA RF SPS as an upgrade to the ORNL Spallation Neutron Source, it led to a possibility for upgrades to CW machines like the many cyclotrons used for commercial applications. Four appendices contain important details of the work carried out under this grant.« less

Microstructural probing of ferritic/martensitic steels using internal transmutation-based positron source

NASA Astrophysics Data System (ADS)

Krsjak, Vladimir; Dai, Yong

2015-10-01

This paper presents the use of an internal 44Ti/44Sc radioisotope source for a direct microstructural characterization of ferritic/martensitic (f/m) steels after irradiation in targets of spallation neutron sources. Gamma spectroscopy measurements show a production of ∼1MBq of 44Ti per 1 g of f/m steels irradiated at 1 dpa (displaced per atom) in the mixed proton-neutron spectrum at the Swiss spallation neutron source (SINQ). In the decay chain 44Ti → 44Sc → 44Ca, positrons are produced together with prompt gamma rays which enable the application of different positron annihilation spectroscopy (PAS) analyses, including lifetime and Doppler broadening spectroscopy. Due to the high production yield, long half-life and relatively high energy of positrons of 44Ti, this methodology opens up new potential for simple, effective and inexpensive characterization of radiation induced defects in f/m steels irradiated in a spallation target.

A NEW DIFFERENTIAL AND ERRANT BEAM CURRENT MONITOR FOR THE SNS* ACCELERATOR

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

Blokland, Willem; Peters, Charles C

2013-01-01

A new Differential and errant Beam Current Monitor (DBCM) is being implemented for both the Spallation Neutron Source's Medium Energy Beam Transport (MEBT) and the Super Conducting Linac (SCL) accelerator sections. These new current monitors will abort the beam when the difference between two toroidal pickups exceeds a threshold. The MEBT DBCM will protect the MEBT chopper target, while the SCL DBCM will abort beam to minimize fast beam losses in the SCL cavities. The new DBCM will also record instances of errant beam, such as beam dropouts, to assist in further optimization of the SNS Accelerator. A software Errantmore » Beam Monitor was implemented on the regular BCM hardware to study errant beam pulses. The new system will take over this functionality and will also be able to abort beam on pulse-to-pulse variations. Because the system is based on the FlexRIO hardware and programmed in LabVIEW FPGA, it will be able to abort beam in about 5 us. This paper describes the development, implementation, and initial test results of the DBCM, as well as errant beam examples.« less

The ^58,60Ni(n,α) Reactions from Threshold to 50 MeV

NASA Astrophysics Data System (ADS)

Haight, R. C.; Bateman, F. B.; Sterbenz, S. M.; Chadwick, M. B.; Young, P. G.; Grimes, S. M.; Wasson, O. A.; Vonach, H.; Maier-Komor, P.

1996-10-01

Information on nuclear level densities over a wide range of excitation energies can be obtained from data on (n,α) reactions.(M. B. Chadwick et al., this meeting) We have measured α-particle emission cross sections, angular distributions and emission spectra for neutrons up to 50 MeV on targets of ^58Ni and ^60Ni using the pulsed spallation source of fast neutrons at the Los Alamos Neutron Science Center. The results will be compared with our previous measurements on ^59Co.(S. M. Grimes et al., Nuclear Science and Engineering in press) The possibilities of extending this method to much heavier nuclides will be discussed.

Operation and reactivity measurements of an accelerator driven subcritical TRIGA reactor

NASA Astrophysics Data System (ADS)

O'Kelly, David Sean

Experiments were performed at the Nuclear Engineering Teaching Laboratory (NETL) in 2005 and 2006 in which a 20 MeV linear electron accelerator operating as a photoneutron source was coupled to the TRIGA (Training, Research, Isotope production, General Atomics) Mark II research reactor at the University of Texas at Austin (UT) to simulate the operation and characteristics of a full-scale accelerator driven subcritical system (ADSS). The experimental program provided a relatively low-cost substitute for the higher power and complexity of internationally proposed systems utilizing proton accelerators and spallation neutron sources for an advanced ADSS that may be used for the burning of high-level radioactive waste. Various instrumentation methods that permitted ADSS neutron flux monitoring in high gamma radiation fields were successfully explored and the data was used to evaluate the Stochastic Pulsed Feynman method for reactivity monitoring.

Possibility of a crossed-beam experiment involving slow-neutron capture by unstable nuclei - ``rapid-process tron''

NASA Astrophysics Data System (ADS)

Yamazaki, T.; Katayama, I.; Uwamino, Y.

1993-02-01

The possibility of a crossed beam facility of slow neutrons capturing unstable nuclei is examined in connection with the Japanese Hadron Project. With a pulsed proton beam of 50 Hz repetition and with a 100 μA average beam current, one obtains a spallation neutron source of 2.4 × 10 8 thermal neutrons/cm 3/spill over a 60 cm length with a 3 ms average duration time by using a D 2O moderator. By confining radioactive nuclei of 10 9 ions in a beam circulation ring of 0.3 MHz revolution frequency, so that nuclei pass through the neutron source, one obtains a collision luminosity of 3.9 × 10 24/cm 2/s. A new research domain aimed at studying rapid processes in nuclear genetics in a laboratory will be created.

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

Next Generation H- Ion Sources for the SNS

NASA Astrophysics Data System (ADS)

Welton, R. F.; Stockli, M. P.; Murray, S. N.; Crisp, D.; Carmichael, J.; Goulding, R. H.; Han, B.; Tarvainen, O.; Pennisi, T.; Santana, M.

2009-03-01

The U.S. Spallation Neutron Source (SNS) is the leading accelerator-based, pulsed neutron-scattering facility, currently in the process of ramping up neutron production. In order to insure meeting operational requirements as well as providing for future facility beam power upgrades, a multifaceted H- ion source development program is ongoing. This work discusses several aspects of this program, specifically the design and first beam measurements of an RF-driven, external antenna H- ion source based on an A1N ceramic plasma chamber, elemental and chromate Cs-systems, and plasma ignition gun. Unanalyzed beam currents of up to ˜100 mA (60 Hz, 1 ms) have been observed and sustained currents >60 mA (60 Hz, 1 ms) have been demonstrated on the test stand. Accelerated beam currents of ˜40 mA have also been demonstrated into the SNS front end. Data are also presented describing the first H- beam extraction experiments from a helicon plasma generator based on the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) engine design.

Oxidative Recession, Sulfur Release, and Al203 Spallation for Y-Doped Alloys

NASA Technical Reports Server (NTRS)

Smialek, James L.

2001-01-01

Second-order spallation phenomena have been noted for Y-doped Rene'N5 after long term oxidation at 1150 degrees C. The reason for this behavior has not been conclusively identified. A mass equivalence analysis has shown that the surface recession resulting from oxidation has the potential of releasing about 0.15 monolayer of sulfur for every 1 mg/sq cm of oxygen reacted for an alloy containing 5 ppmw of sulfur. This amount is significant in comparison to levels that have been shown to result in first-order spallation behavior for undoped alloys. Oxidative recession is therefore speculated to be a contributing source of sulfur and second-order spallation for Y-doped alloys.

Jet formation in spallation of metal film from substrate under action of femtosecond laser pulse

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

Inogamov, N. A., E-mail: nailinogamov@googlemail.com; Zhakhovskii, V. V.; Khokhlov, V. A.

2015-01-15

It is well known that during ablation by an ultrashort laser pulse, the main contribution to ablation of the substance is determined not by evaporation, but by the thermomechanical spallation of the substance. For identical metals and pulse parameters, the type of spallation is determined by film thickness d{sub f}. An important gauge is metal heating depth d{sub T} at the two-temperature stage, at which electron temperature is higher than ion temperature. We compare cases with d{sub f} < d{sub T} (thin film) and d{sub f} ≫ d{sub T} (bulk target). Radius R{sub L} of the spot of heating bymore » an optical laser is the next (after d{sub f}) important geometrical parameter. The morphology of film bulging in cases where d{sub f} < d{sub T} on the substrate (blistering) changes upon a change in radius R{sub L} in the range from diffraction limit R{sub L} ∼ λ to high values of R{sub L} ≫ λ, where λ ∼ 1 μm is the wavelength of optical laser radiation. When d{sub f} < d{sub T}, R{sub L} ∼ λ, and F{sub abs} > F{sub m}, gold film deposited on the glass target acquires a cupola-shaped blister with a miniature frozen nanojet in the form of a tip on the circular top of the cupola (F{sub abs} and F{sub m} are the absorbed energy and the melting threshold of the film per unit surface area of the film). A new physical mechanism leading to the formation of the nanojet is proposed.« less

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.

The thermal triple-axis-spectrometer EIGER at the continuous spallation source SINQ

NASA Astrophysics Data System (ADS)

Stuhr, U.; Roessli, B.; Gvasaliya, S.; Rønnow, H. M.; Filges, U.; Graf, D.; Bollhalder, A.; Hohl, D.; Bürge, R.; Schild, M.; Holitzner, L.; Kaegi, C.,; Keller, P.; Mühlebach, T.

2017-05-01

EIGER is the new thermal triple-axis-spectrometer at the continuous spallation SINQ at PSI. The shielding of the monochromator consists only of non- or low magnetizable materials, which allows the use of strong magnetic fields with the instrument. This shielding reduces the high energy neutron contamination to a comparable level of thermal spectrometers at reactor sources. The instrument design, the performance and first results of the spectrometer are presented.

Probing light sterile neutrino signatures at reactor and Spallation Neutron Source neutrino experiments

NASA Astrophysics Data System (ADS)

Kosmas, T. S.; Papoulias, D. K.; Tórtola, M.; Valle, J. W. F.

2017-09-01

We investigate the impact of a fourth sterile neutrino at reactor and Spallation Neutron Source neutrino detectors. Specifically, we explore the discovery potential of the TEXONO and COHERENT experiments to subleading sterile neutrino effects through the measurement of the coherent elastic neutrino-nucleus scattering event rate. Our dedicated χ2-sensitivity analysis employs realistic nuclear structure calculations adequate for high purity sub-keV threshold Germanium detectors.

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

Recent progress on beam stability study in the PSR

NASA Astrophysics Data System (ADS)

Wang, Tai-Sen F.; Channell, Paul J.; Cooper, Richard K.; Fitzgerald, Daniel H.; Hardek, Tom; Hutson, Richard; Jason, Andrew J.; Macek, Robert J.; Plum, Michael A.; Wilkinson, Carol

A fast transverse instability has been observed in the Los Alamos Proton Storage Ring (PSR) when the injected beam intensity reaches more than 2 (times) 10(exp 13) protons per pulse. Understanding the cause and control of this instability has taken on new importance as the neutron-scattering community considers the next generation of accelerator-driven spallation-neutron sources, which call for peak-proton intensities of 10(exp 14) per pulse or higher. Previous observations and theoretical studies indicate that the instability in the PSR is most likely driven by electrons trapped within the proton beam. Recent studies using an experimental electron-clearing system and voltage-biased pinger-electrodes for electron clearing and collection support this hypothesis. Experiments have also been performed to study the instability threshold when varying the electron production rate. Theoretical studies include a computer simulation of a simplified model for the e -- p instability and the investigation of possible electron confinement in the ring-element magnetic fields. This paper reports some recent results from these studies.

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.

Development and Characterization of a High-Energy Neutron Time-of-Flight Imaging System

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

Madden, Amanda Christine; Schirato, Richard C.; Swift, Alicia L.

We present that Los Alamos National Laboratory has developed a prototype of a high-energy neutron time-of-flight imaging system for the non-destructive evaluation of dense, massive, and/or high atomic number objects. High-energy neutrons provide the penetrating power, and thus the high dynamic range necessary to image internal features and defects of such objects. The addition of the time gating capability allows for scatter rejection when paired with a pulsed monoenergetic beam, or neutron energy selection when paired with a pulsed broad-spectrum neutron source. The Time Gating to Reject Scatter and Select Energy (TiGReSSE) system was tested at the Los Alamos Neutronmore » Science Center’s (LANSCE) Weapons Nuclear Research (WNR) facility, a spallation neutron source, to provide proof of concept measurements and to characterize the instrument response. This paper will show results of several objects imaged during this run cycle. In addition, results from system performance metrics such as the Modulation Transfer Function and the Detective Quantum Efficiency measured as a function of neutron energy, characterize the current system performance and inform the next generation of neutron imaging instrument.« less

Development and Characterization of a High-Energy Neutron Time-of-Flight Imaging System

DOE PAGES

Madden, Amanda Christine; Schirato, Richard C.; Swift, Alicia L.; ...

2017-02-09

We present that Los Alamos National Laboratory has developed a prototype of a high-energy neutron time-of-flight imaging system for the non-destructive evaluation of dense, massive, and/or high atomic number objects. High-energy neutrons provide the penetrating power, and thus the high dynamic range necessary to image internal features and defects of such objects. The addition of the time gating capability allows for scatter rejection when paired with a pulsed monoenergetic beam, or neutron energy selection when paired with a pulsed broad-spectrum neutron source. The Time Gating to Reject Scatter and Select Energy (TiGReSSE) system was tested at the Los Alamos Neutronmore » Science Center’s (LANSCE) Weapons Nuclear Research (WNR) facility, a spallation neutron source, to provide proof of concept measurements and to characterize the instrument response. This paper will show results of several objects imaged during this run cycle. In addition, results from system performance metrics such as the Modulation Transfer Function and the Detective Quantum Efficiency measured as a function of neutron energy, characterize the current system performance and inform the next generation of neutron imaging instrument.« less

Comments on the possibility of cavitation in liquid metal targets for pulsed spallation neutron sources

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

Carpenter J.M.

When short pulses of protons strike the volume of a liquid target, the rapid heating produces a pressurized region which relaxes as the pressure wave propagates outward. Skala and Bauer have modeled the effects of the pressure wave impinging on the container walls of a liquid mercury target under ESS conditions. They find that high pressures and high wall stresses result if the medium is uniform, nearly incompressible liquid. The pressure and the stresses are much reduced if the liquid contains bubbles of helium, due to their high compressibility. However, according to the calculation, the pressure still reaches an atmospheremore » or so at the surface, which reflects the compressive wave as a rarefaction wave of the same magnitude. Even such modest underpressures can lead to the growth of bubbles (cavitation) at or near the surface, which can collapse violently and erode the container surface. It is necessary to avoid this. Leighton provides a wide ranging discussion of pressure waves in bubbly media, which may provide insights into the nature and control of cavitation phenomena. The paper surveys some of the relevant information from that source.« less

The ESS spoke cavity cryomodules

NASA Astrophysics Data System (ADS)

Bousson, Sebastien; Darve, Christine; Duthil, Patxi; Elias, Nuno; Molloy, Steve; Reynet, Denis; Thermeau, Jean-Pierre

2014-01-01

The European Spallation Source (ESS) is a multi-disciplinary research centre under design and construction in Lund, Sweden. This new facility is funded by a collaboration of 17 European countries and is expected to be up to 30 times brighter than today's leading facilities and neutron sources. The ESS will enable new opportunities for researchers in the fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics. A 5 MW long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle), and the beam current is 62.5 mA. It is composed of one string of spoke cavity cryomodule and two strings of elliptical cavity cryomodules. This paper introduces the thermo-mechanical design and expected operation of the ESS spoke cavity cryomodules. These cryomodules contain two double spoke bulk Niobium cavities operating at 2 K and at a frequency of 352.21 MHz. The superconducting section of the Spoke Linac accelerates the beam from 90 MeV to 220 MeV. A Spoke Cavity Cryomodule Technology Demonstrator will be built and tested in order to validate the ESS series production.

The ESS elliptical cavity cryomodules

NASA Astrophysics Data System (ADS)

Darve, Christine; Bosland, Pierre; Devanz, Guillaume; Olivier, Gilles; Renard, Bertrand; Thermeau, Jean-Pierre

2014-01-01

The European Spallation Source (ESS) is a multi-disciplinary research centre under design and construction in Lund, Sweden. This new facility is funded by a collaboration of 17 European countries and is expected to be up to 30 times brighter than today's leading facilities and neutron sources. The ESS will enable new opportunities for researchers in the fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics. A 5 MW long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms, the repetition frequency is 14 Hz (4 % duty cycle), and the beam current is 62.5 mA. The superconducting section of the Linac accelerates the beam from 80 MeV to 2.0 GeV. It is composed of one string of spoke cavity cryomodule and two strings of elliptical cavity cryomodules. These cryomodules contain four elliptical Niobium cavities operating at 2 K and at a frequency of 704.42 MHz. This paper introduces the thermo-mechanical design, the prototyping and the expected operation of the ESS elliptical cavity cryomodules. An Elliptical Cavity Cryomodule Technology Demonstrator (ECCTD) will be built and tested in order to validate the ESS series production.

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

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.

Irradiation of amorphous Ta42Si13N45 film with a femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Romano, V.; Meier, M.; Theodore, N. D.; Marble, D. K.; Nicolet, M.-A.

2011-07-01

Films of 260 nm thickness, with atomic composition Ta42Si13N45, on 4″ silicon wafers, have been irradiated in air with single laser pulses of 200 femtoseconds duration and 800 nm wave length. As sputter-deposited, the films are structurally amorphous. A laterally truncated Gaussian beam with a near-uniform fluence of ˜0.6 J/cm2 incident normally on such a film ablates 23 nm of the film. Cross-sectional transmission electron micrographs show that the surface of the remaining film is smooth and flat on a long-range scale, but contains densely distributed sharp nanoprotrusions that sometimes surpass the height of the original surface. Dark field micrographs of the remaining material show no nanograins. Neither does glancing angle X-ray diffraction with a beam illuminating many diffraction spots. By all evidence, the remaining film remains amorphous after the pulsed femtosecond irradiation. The same single pulse, but with an enhanced and slightly peaked fluence profile, creates a spot with flat peripheral terraces whose lateral extents shrink with depth, as scanning electron and atomic force micrographs revealed. Comparison of the various figures suggests that the sharp nanoprotrusions result from an ejection of material by brittle fraction and spallation, not from ablation by direct beam-solid interaction. Conditions under which spallation should dominate over ablation are discussed.

X-ray microtomography study of the spallation response in Ta-W

NASA Astrophysics Data System (ADS)

McDonald, Samuel; Cotton, Matthew; Millett, Jeremy; Bourne, Neil; Withers, Philip

2013-06-01

The response of metallic materials to high strain-rate (impact) loading is of interest to a number of communities. Traditionally, the largest driver has been the military, in its need to understand armour and resistance to ballistic attack. More recently, industries such as aerospace (foreign object damage, bird strike, etc.), automotive (crash-worthiness) and satellite protection (orbital debris) have all appreciated the necessity of such information. It is therefore important to understand the dynamic tensile or spallation response, and in particular to be able to observe in three-dimensions, and in a non-invasive manner, the physical damage present in the spalled region post-impact. The current study presents plate impact experiments investigating the spallation damage response of recovered targets of the tantalum alloy Ta-2.5%W. Using X-ray microtomography the damage resulting from differing impact conditions (impact velocity/stress, pulse duration) is compared and characterised in 3-D. Combined with free surface velocity measurements, the tensile failure mechanisms during dynamic loading have been identified.

The status of the SNS external antenna ion source and spare RFQ test facility

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

Welton, R. F., E-mail: welton@ornl.gov; Aleksandrov, A. V.; Han, B. X.

The Oak Ridge National Laboratory operates the Spallation Neutron Source, consisting of a H{sup −} ion source, a 1 GeV linac and an accumulator ring. The accumulated <1 μs-long, ∼35 A beam pulses are extracted from the ring at 60 Hz and directed onto a liquid Hg target. Spalled neutrons are directed to ∼20 world class instruments. Currently, the facility operates routinely with ∼1.2 MW of average beam power, which soon will be raised to 1.4 MW. A future upgrade with a second target station calls for raising the power to 2.8 MW. This paper describes the status of twomore » accelerator components expected to play important roles in achieving these goals: a recently acquired RFQ accelerator and the external antenna ion source. Currently, the RFQ is being conditioned in a newly constructed 2.5 MeV Integrated Test Facility (ITF) and the external antenna source is also being tested on a separate test stand. This paper presents the results of experiments and the testing of these systems.« less

Improved neutron-gamma discrimination for a {sup 6}Li-glass neutron detector using digital signal analysis methods

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

Wang, C. L., E-mail: wangc@ornl.gov; Riedel, R. A.

2016-01-15

A {sup 6}Li-glass scintillator (GS20) based neutron Anger camera was developed for time-of-flight single-crystal diffraction instruments at Spallation Neutron Source. Traditional Pulse-Height Analysis (PHA) for Neutron-Gamma Discrimination (NGD) resulted in the neutron-gamma efficiency ratio (defined as NGD ratio) on the order of 10{sup 4}. The NGD ratios of Anger cameras need to be improved for broader applications including neutron reflectometers. For this purpose, six digital signal analysis methods of individual waveforms acquired from photomultiplier tubes were proposed using (i) charge integration, (ii) pulse-amplitude histograms, (iii) power spectrum analysis combined with the maximum pulse-amplitude, (iv) two event parameters (a{sub 1}, b{submore » 0}) obtained from a Wiener filter, (v) an effective amplitude (m) obtained from an adaptive least-mean-square filter, and (vi) a cross-correlation coefficient between individual and reference waveforms. The NGD ratios are about 70 times those from the traditional PHA method. Our results indicate the NGD capabilities of neutron Anger cameras based on GS20 scintillators can be significantly improved with digital signal analysis methods.« less

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.

Radiation effects in structural materials of spallation targets

NASA Astrophysics Data System (ADS)

Jung, P.

2002-02-01

Effects of radiation damage by protons and neutrons in structural materials of spallation neutron sources are reviewed. Effects of atomic displacements, defect mobility and transmutation products, especially hydrogen and helium, on physical and mechanical properties are discussed. The most promising candidate materials (austenitic stainless steels, ferritic/martensitic steels and refractory alloys) are compared, and needed investigations are identified.

Water content contribution in calculus phantom ablation during Q-switched Tm:YAG laser lithotripsy.

PubMed

Zhang, Jian J; Rajabhandharaks, Danop; Xuan, Jason Rongwei; Wang, Hui; Chia, Ray W J; Hasenberg, Tom; Kang, Hyun Wook

2015-01-01

Q-switched (QS) Tm:YAG laser ablation mechanisms on urinary calculi are still unclear to researchers. Here, dependence of water content in calculus phantom on calculus ablation performance was investigated. White gypsum cement was used as a calculus phantom model. The calculus phantoms were ablated by a total 3-J laser pulse exposure (20 mJ, 100 Hz, 1.5 s) and contact mode with N=15 sample size. Ablation volume was obtained on average 0.079, 0.122, and 0.391  mm3 in dry calculus in air, wet calculus in air, and wet calculus in-water groups, respectively. There were three proposed ablation mechanisms that could explain the effect of water content in calculus phantom on calculus ablation performance, including shock wave due to laser pulse injection and bubble collapse, spallation, and microexplosion. Increased absorption coefficient of wet calculus can cause stronger spallation process compared with that caused by dry calculus; as a result, higher calculus ablation was observed in both wet calculus in air and wet calculus in water. The test result also indicates that the shock waves generated by short laser pulse under the in-water condition have great impact on the ablation volume by Tm:YAG QS laser.

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

Spallation processes and nuclear interaction products of cosmic rays.

PubMed

Silberberg, R; Tsao, C H

1990-08-01

Most cosmic-ray nuclei heavier than helium have suffered nuclear collisions in the interstellar gas, with transformation of nuclear composition. The isotopic and elemental composition at the sources has to be inferred from the observed composition near the Earth. The source composition permits tests of current ideas on sites of origin, nucleosynthesis in stars, evolution of stars, the mixing and composition of the interstellar medium and injection processes prior to acceleration. The effects of nuclear spallation, production of radioactive nuclides and the time dependence of their decay provide valuable information on the acceleration and propagation of cosmic rays, their nuclear transformations, and their confinement time in the Galaxy. The formation of spallation products that only decay by electron capture and are relatively long-lived permits an investigation of the nature and density fluctuations (like clouds) of the interstellar medium. Since nuclear collisions yield positrons, antiprotons, gamma rays and neutrinos, we shall discuss these topics briefly.

Operational performance characteristics of the WISH detector array on the ISIS spallation neutron source

NASA Astrophysics Data System (ADS)

Duxbury, D.; Khalyavin, D.; Manuel, P.; Raspino, D.; Rhodes, N.; Schooneveld, E.; Spill, E.

2014-12-01

The performance of the position sensitive neutron detector array of the WISH diffractometer is discussed. WISH (Wide angle In a Single Histogram) is one of the seven instruments currently available for users on the second target station (TS2) of the ISIS spallation neutron source, and is used mainly for magnetic studies of materials. WISH is instrumented with an array of 10 detector panels, covering an angular range of 320o, orientated in two semi-cylindrical annuli around a central sample position at a radius of 2.2m. In total the 10 detector panels are composed of 1520 3He based position sensitive detector tubes. Each tube has an active length of one metre, a diameter of 8mm and is filled with 3He at 15 bar. The specification for the WISH detectors included a neutron detection efficiency of 50% at a neutron wavelength of 1Å with good gamma rejection. A position resolution better than 8 mm FWHM along the length of the tubes was also required which has been met experimentally. Results obtained from the detector arrays showing pulse height and positional information both prior to and post installation are shown. The first 5 of the 10 detector panels have been operational since 2009, and comparable diffraction data from powder and single crystal samples taken from the remaining 5 panels (installation completed in 2013) shows that we have a detector array with a highly stable performance which is easily assembled and maintained. Finally some real user data is shown, highlighting the excellent quality of data attainable with this instrument.

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

Tsapatsaris, N., E-mail: nikolaos.tsapatsaris@esss.se, E-mail: ruep.lechner@gmail.com, E-mail: bordallo@nbi.ku.dk; Bordallo, H. N., E-mail: nikolaos.tsapatsaris@esss.se, E-mail: ruep.lechner@gmail.com, E-mail: bordallo@nbi.ku.dk; European Spallation Source ERIC, Tunavägen 24, 22100 Lund

In this work, we present the conceptual design of the backscattering time-of-flight spectrometer MIRACLES approved for construction at the long-pulse European Spallation Source (ESS). MIRACLES’s unparalleled combination of variable resolution, high flux, extended energy, and momentum transfer (0.2–6 Å{sup −1}) ranges will open new avenues for neutron backscattering spectroscopy. Its remarkable flexibility can be attributed to 3 key elements: the long-pulse time structure and low repetition rate of the ESS neutron source, the chopper cascade that tailors the moderator pulse in the primary part of the spectrometer, and the bent Si(111) analyzer crystals arranged in a near-backscattering geometry in themore » secondary part of the spectrometer. Analytical calculations combined with instrument Monte-Carlo simulations show that the instrument will provide a variable elastic energy resolution, δ(ħ ω), between 2 and 32 μeV, when using a wavelength of λ ≈ 6.267 Å (Si(111)-reflection), with an energy transfer range, ħ ω, centered at the elastic line from −600 to +600 μeV. In addition, when selecting λ ≈ 2.08 Å (i.e., the Si(333)-reflection), δ(ħ ω) can be relaxed to 300 μeV and ħ ω from about 10 meV in energy gain to ca −40 meV in energy loss. Finally, the dynamic wavelength range of MIRACLES, approximately 1.8 Å, can be shifted within the interval of 2–20 Å to allow the measurement of low-energy inelastic excitations.« less

Ductility recovery in structural materials for spallation targets by post-irradiation annealing

NASA Astrophysics Data System (ADS)

Chen, J.; Jung, P.; Rödig, M.; Ullmaier, H.; Bauer, G. S.

2005-08-01

Low temperature irradiation embrittlement is one of the major criteria to determine the lifetime of spallation targets. Embrittlement is especially high at low service temperatures, e.g. 250 °C in liquid-mercury sources. It was the aim of the present study to investigate the effect of post-irradiation annealing on the mechanical properties of irradiated structural materials. The specimens used were obtained from spent target components of operating spallation facilities (Los Alamos Neutron Science Center, LANSCE, and the Spallation Neutron Source at Rutherford-Appleton Laboratory, ISIS). The investigated materials include a nickel-based alloy (IN718), an austenitic stainless steel (AISI 304L), a martensitic stainless steel (DIN 1.4926) and a refractory metal (Ta) which experienced 800 MeV proton irradiation to fluences of several 10 25 p/m 2. The specimens were annealed from 300 °C to 700 °C for 1 to 10 h, respectively, and their mechanical property changes were subsequently investigated at room temperature and 250 °C by tensile testing and fracture surface analysis conducted by scanning electron microscopy (SEM). The results showed that the ductility recovered to a large degree in 304L and DIN 1.4926 materials while their strength remained almost unchanged. Especially for DIN 1.4926, the ductility recovery is remarkable already at 400 °C. Together with its favorable thermo-mechanical properties, this makes martensitic steel a candidate for structural materials of spallation targets.

Beam commission of the high intensity proton source developed at INFN-LNS for the European Spallation Source

NASA Astrophysics Data System (ADS)

Neri, L.; Celona, L.; Gammino, S.; Miraglia, A.; Leonardi, O.; Castro, G.; Torrisi, G.; Mascali, D.; Mazzaglia, M.; Allegra, L.; Amato, A.; Calabrese, G.; Caruso, A.; Chines, F.; Gallo, G.; Longhitano, A.; Manno, G.; Marletta, S.; Maugeri, A.; Passarello, S.; Pastore, G.; Seminara, A.; Spartà, A.; Vinciguerra, S.

2017-07-01

At the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud (INFN-LNS) the beam commissioning of the high intensity Proton Source for the European Spallation Source (PS-ESS) started in November 2016. Beam stability at high current intensity is one of the most important parameter for the first steps of the ongoing commissioning. Promising results were obtained since the first source start with a 6 mm diameter extraction hole. The increase of the extraction hole to 8 mm allowed improving PS-ESS performances and obtaining the values required by the ESS accelerator. In this work, extracted beam current characteristics together with Doppler shift and emittance measurements are presented, as well as the description of the next phases before the installation at ESS in Lund.

Integrated modeling/analyses of thermal-shock effects in SNS targets

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

Taleyarkhan, R.P.; Haines, J.

1996-06-01

In a spallation neutron source (SNS), extremely rapid energy pulses are introduced in target materials such as mercury, lead, tungsten, uranium, etc. Shock phenomena in such systems may possibly lead to structural material damage beyond the design basis. As expected, the progression of shock waves and interaction with surrounding materials for liquid targets can be quite different from that in solid targets. The purpose of this paper is to describe ORNL`s modeling framework for `integrated` assessment of thermal-shock issues in liquid and solid target designs. This modeling framework is being developed based upon expertise developed from past reactor safety studies,more » especially those related to the Advanced Neutron Source (ANS) Project. Unlike previous separate-effects modeling approaches employed (for evaluating target behavior when subjected to thermal shocks), the present approach treats the overall problem in a coupled manner using state-of-the-art equations of state for materials of interest (viz., mercury, tungsten and uranium). That is, the modeling framework simultaneously accounts for localized (and distributed) compression pressure pulse generation due to transient heat deposition, the transport of this shock wave outwards, interaction with surrounding boundaries, feedback to mercury from structures, multi-dimensional reflection patterns & stress induced (possible) breakup or fracture.« less

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

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.

The ESS Superconducting RF Cavity and Cryomodule Cryogenic Processes

NASA Astrophysics Data System (ADS)

Darve, C.; Elias, N.; Molloy, S.; Bosland, P.; Renard, B.; Bousson, S.; Olivier, G.; Reynet, D.; Thermeau, J. P.

The European Spallation Source (ESS) is one of Europe's largest research infrastructures, tobring new insights to the grand challenges of science and innovation in fields as diverse as material and life sciences, energy, environmental technology, cultural heritage,solid-state and fundamental physics by the end of the decade. The collaborative project is funded by a collaboration of 17 European countries and is under design and construction in Lund, Sweden. A 5 MW, long pulse proton accelerator is used to reach this goal. The pulsed length is 2.86 ms and the repetition frequency is 14 Hz (4% duty cycle). The choice of SRF technology is a key element in the development of the ESS linear accelerator (linac). The superconducting linacis composed of one section of spoke cavity cryomodules(352.21 MHz) and two sections of elliptical cavity cryomodules (704.42 MHz). These cryomodules contain niobium SRF cavities operating at 2 K, cooled by the accelerator cryoplantthrough the cryogenic distribution system. This paper presents the superconducting RF cavity and cryomodule cryogenic processes, which are developed for the technology demonstrators and to be ultimately integrated for the ESS tunnel operation.

Study on induced radioactivity of China Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Wu, Qing-Biao; Wang, Qing-Bin; Wu, Jing-Min; Ma, Zhong-Jian

2011-06-01

China Spallation Neutron Source (CSNS) is the first High Energy Intense Proton Accelerator planned to be constructed in China during the State Eleventh Five-Year Plan period, whose induced radioactivity is very important for occupational disease hazard assessment and environmental impact assessment. Adopting the FLUKA code, the authors have constructed a cylinder-tunnel geometric model and a line-source sampling physical model, deduced proper formulas to calculate air activation, and analyzed various issues with regard to the activation of different tunnel parts. The results show that the environmental impact resulting from induced activation is negligible, whereas the residual radiation in the tunnels has a great influence on maintenance personnel, so strict measures should be adopted.

Observations of Space Charge effects in the Spallation Neutron Source Accumulator Ring

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

Potts III, Robert E; Cousineau, Sarah M; Holmes, Jeffrey A

2012-01-01

The Spallation Neutron Source accumulator ring was designed to allow independent control of the transverse beam distribution in each plane. However, at high beam intensities, nonlinear space charge forces can strongly influence the final beam distribution and compromise our ability to independently control the transverse distributions. In this study we investigate the evolution of the beam at intensities of up to ~8x10^13 ppp through both simulation and experiment. Specifically, we analyze the evolution of the beam distribution for beams with different transverse aspect ratios and tune splits. We present preliminary results of simulations of our experiments.

Recent performance of and plasma outage studies with the SNS H{sup −} source

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

Stockli, M. P., E-mail: stockli@ornl.gov; Han, B.; Murray, S. N.

2016-02-15

Spallation Neutron Source ramps to higher power levels that can be sustained with high availability. The goal is 1.4 MW despite a compromised radio frequency quadrupole (RFQ), which requires higher radio frequency power than design levels to approach the nominal beam transmission. Unfortunately at higher power the RFQ often loses its thermal stability, a problem apparently enhanced by beam losses and high influxes of hydrogen. Delivering as much H{sup −} beam as possible with the least amount of hydrogen led to plasma outages. The root cause is the dense 1-ms long ∼55-kW 2-MHz plasma pulses reflecting ∼90% of the continuousmore » ∼300 W, 13-MHz power, which was mitigated with a 4-ms filter for the reflected power signal and an outage resistant, slightly detuned 13-MHz match. Lowering the H{sub 2} gas also increased the H{sup −} beam current to ∼55 mA and increased the RFQ transmission by ∼7% (relative)« less

Surface ablation of aluminum and silicon by ultrashort laser pulses of variable width

NASA Astrophysics Data System (ADS)

Zayarny, D. A.; Ionin, A. A.; Kudryashov, S. I.; Makarov, S. V.; Kuchmizhak, A. A.; Vitrik, O. B.; Kulchin, Yu. N.

2016-06-01

Single-shot thresholds of surface ablation of aluminum and silicon via spallative ablation by infrared (IR) and visible ultrashort laser pulses of variable width τlas (0.2-12 ps) have been measured by optical microscopy. For increasing laser pulse width τlas < 3 ps, a drastic (threefold) drop of the ablation threshold of aluminum has been observed for visible pulses compared to an almost negligible threshold variation for IR pulses. In contrast, the ablation threshold in silicon increases threefold with increasing τlas for IR pulses, while the corresponding thresholds for visible pulses remained almost constant. In aluminum, such a width-dependent decrease in ablation thresholds has been related to strongly diminished temperature gradients for pulse widths exceeding the characteristic electron-phonon thermalization time. In silicon, the observed increase in ablation thresholds has been ascribed to two-photon IR excitation, while in the visible range linear absorption of the material results in almost constant thresholds.

Measurement of interface strength by a laser spallation technique

NASA Astrophysics Data System (ADS)

Gupta, V.; Argon, A. S.; Parks, D. M.; Cornie, J. A.

A LASER spallation experiment has been developed to measure the strength of planar interfaces between a substrate and a thin coating (in the thickness range of 0.3-3 μm). In this technique a laser pulse of a high enough energy and a pre-determined duration is converted into a pressure pulse of a critical amplitude and width that is sent through the substrate toward the free surface with the coating. The reflected tensile wave from the free surface of the coating pries-off the coating. The critical stress amplitude that accomplishes the removal of the coating is determined from a computer simulation of the process. The simulation itself is verified by means of a piezo-electric crystal probe that is capable of mapping out the profile of the stress pulse generated by the laser pulse. Interface strength values ranging from 3.7 to 10.5 GPa were determined for the Si/SiC system. For the interfaces between pyrolytic graphite and SiC coatings an average strength of 7.2 GPA was measured, while the corresponding interface strength between a Pitch-55 type ribbon with a fiber-like morphology and SiC coatings was found to be 0.23 GPa. Intrinsic strengths of SiC coatings and Si crystal were also determined using this technique. These were, on the average, 8.6 GPa for Si crystals and 11.9 GPa for a SiC coating. Furthermore, the potential of the laser technique to determine the interface toughness was also demonstrated, provided well-characterizable flaws can be planted on the interface.

Improvements to the internal and external antenna H(-) ion sources at the Spallation Neutron Source.

PubMed

Welton, R F; Dudnikov, V G; Han, B X; Murray, S N; Pennisi, T R; Pillar, C; Santana, M; Stockli, M P; Turvey, M W

2014-02-01

The Spallation Neutron Source (SNS), a large scale neutron production facility, routinely operates with 30-40 mA peak current in the linac. Recent measurements have shown that our RF-driven internal antenna, Cs-enhanced, multi-cusp ion sources injects ∼55 mA of H(-) beam current (∼1 ms, 60 Hz) at 65-kV into a Radio Frequency Quadrupole (RFQ) accelerator through a closely coupled electrostatic Low-Energy Beam Transport system. Over the last several years a decrease in RFQ transmission and issues with internal antennas has stimulated source development at the SNS both for the internal and external antenna ion sources. This report discusses progress in improving internal antenna reliability, H(-) yield improvements which resulted from modifications to the outlet aperture assembly (applicable to both internal and external antenna sources) and studies made of the long standing problem of beam persistence with the external antenna source. The current status of the external antenna ion source will also be presented.

Editorial

NASA Astrophysics Data System (ADS)

Mansur, Louis K.

2018-08-01

The Thirteenth International Workshop on Spallation Materials Technology (IWSMT-13) was held at Chattanooga, Tennessee, October 30 to November 4, 2016. The meeting was organized by Oak Ridge National Laboratory, with participation from the Belgian Nuclear Research Centre, Chinese Academy of Sciences, European Spallation Source, Japan Atomic Energy Agency, Los Alamos National Laboratory, Paul Scherrer Institut, Rutherford Appleton Laboratory and other institutes. The meeting included 52 presentations, of which 9 peer-reviewed full papers are published in this special issue.

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

Anderson, David E.

The JEMA modulator was originally developed for the European Spallation Source (ESS) when Spain was under consideration as a location for the ESS facility. Discussions ensued and the Spallation Neutron Source Research Accelerator Division agreed to form a collaboration with ESS-Bilbao (ESS-B) consortium to provide services for specifying the requirements for a version of the modulator capable of operating twelve 550 kW klystrons, monitoring the technical progress on the contract with JEMA, installing and commissioning the modulator at SNS, and performing a 30 day full power test. This work was recently completed, and this report discusses those activities with primarymore » emphasis on the installation and testing activities.« less

Practical in-situ determination of ortho-para hydrogen ratios via fiber-optic based Raman spectroscopy

DOE PAGES

Sutherland, Liese -Marie; Knudson, James N.; Mocko, Michal; ...

2015-12-17

An experiment was designed and developed to prototype a fiber-optic-based laser system, which measures the ratio of ortho-hydrogen to para-hydrogen in an operating neutron moderator system at the Los Alamos Neutron Science Center (LANSCE) spallation neutron source. Preliminary measurements resulted in an ortho to para ratio of 3.06:1, which is within acceptable agreement with the previously published ratio. As a result, the successful demonstration of Raman Spectroscopy for this measurement is expected to lead to a practical method that can be applied for similar in-situ measurements at operating neutron spallation sources.

Practical in-situ determination of ortho-para hydrogen ratios via fiber-optic based Raman spectroscopy

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

Sutherland, Liese -Marie; Knudson, James N.; Mocko, Michal

An experiment was designed and developed to prototype a fiber-optic-based laser system, which measures the ratio of ortho-hydrogen to para-hydrogen in an operating neutron moderator system at the Los Alamos Neutron Science Center (LANSCE) spallation neutron source. Preliminary measurements resulted in an ortho to para ratio of 3.06:1, which is within acceptable agreement with the previously published ratio. As a result, the successful demonstration of Raman Spectroscopy for this measurement is expected to lead to a practical method that can be applied for similar in-situ measurements at operating neutron spallation sources.

The Spallation Neutron Source (SNS) project accelerator systems

NASA Astrophysics Data System (ADS)

Holmes, Jeffrey A.; Alonso, Jose R.

1999-06-01

The SNS will be the world's leading accelerator-based neutron-scattering research facility when it begins operation in 2005. By delivering 1-MW of beam power to a heavy-metal target in short (<1 μs) bursts of 1-GeV protons, the SNS will provide intense neutron beams with flux levels at least a factor of five over present spallation sources. A multi-laboratory (LBNL, LANL, BNL, ANL and ORNL) collaboration, led by Oak Ridge National Laboratory, has developed a reference design that addresses the challenging technology issues associated with this project. This paper discusses the requirements, issues, and constraints that led to the present design choices.

Evolution in boron-based GEM detectors for diffraction measurements: from planar to 3D converters

NASA Astrophysics Data System (ADS)

Albani, Giorgia; Perelli Cippo, Enrico; Croci, Gabriele; Muraro, Andrea; Schooneveld, Erik; Scherillo, Antonella; Hall-Wilton, Richard; Kanaki, Kalliopi; Höglund, Carina; Hultman, Lars; Birch, Jens; Claps, Gerardo; Murtas, Fabrizio; Rebai, Marica; Tardocchi, Marco; Gorini, Giuseppe

2016-11-01

The so-called ‘3He-crisis’ has motivated the neutron detector community to undertake an intense R&D programme in order to develop technologies alternative to standard 3He tubes and suitable for neutron detection systems in future spallation sources such as the European spallation source (ESS). Boron-based GEM (gas electron multiplier) detectors are a promising ‘3He-free’ technology for thermal neutron detection in neutron scattering experiments. In this paper the evolution of boron-based GEM detectors from planar to 3D converters with an application in diffraction measurements is presented. The use of 3D converters coupled with GEMs allows for an optimization of the detector performances. Three different detectors were used for diffraction measurements on the INES instrument at the ISIS spallation source. The performances of the GEM-detectors are compared with those of conventional 3He tubes installed on the INES instrument. The conceptual detector with the 3D converter used in this paper reached a count rate per unit area of about 25% relative to the currently installed 3He tube. Its timing resolution is similar and the signal-to-background ratio (S/B) is 2 times lower.

GRAIN-SCALE FAILURE IN THERMAL SPALLATION DRILLING

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

Walsh, S C; Lomov, I; Roberts, J J

2012-01-19

Geothermal power promises clean, renewable, reliable and potentially widely-available energy, but is limited by high initial capital costs. New drilling technologies are required to make geothermal power financially competitive with other energy sources. One potential solution is offered by Thermal Spallation Drilling (TSD) - a novel drilling technique in which small particles (spalls) are released from the rock surface by rapid heating. While TSD has the potential to improve drilling rates of brittle granitic rocks, the coupled thermomechanical processes involved in TSD are poorly described, making system control and optimization difficult for this drilling technology. In this paper, we discussmore » results from a new modeling effort investigating thermal spallation drilling. In particular, we describe an explicit model that simulates the grain-scale mechanics of thermal spallation and use this model to examine existing theories concerning spalling mechanisms. We will report how borehole conditions influence spall production, and discuss implications for macro-scale models of drilling systems.« less

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.

R&D of A MW-class solid-target for a spallation neutron source

NASA Astrophysics Data System (ADS)

Kawai, Masayoshi; Furusaka, Michihiro; Kikuchi, Kenji; Kurishita, Hiroaki; Watanabe, Ryuzo; Li, Jing-Feng; Sugimoto, Katsuhisa; Yamamura, Tsutomu; Hiraoka, Yutaka; Abe, Katsunori; Hasegawa, Akira; Yoshiie, Masatoshi; Takenaka, Hiroyuki; Mishima, Katsuichiro; Kiyanagi, Yoshiaki; Tanabe, Tetsuo; Yoshida, Naoaki; Igarashi, Tadashi

2003-05-01

R&D for a MW-class solid target composed of tungsten was undertaken to produce a pulsed intense neutron source for a future neutron scattering-facility. In order to solve the corrosion of tungsten, tungsten target blocks were clad with tantalum by means of HIP'ing, brazing and electrolytic coating in a molten salt bath. The applicability of the HIP'ing method was tested through fabricating target blocks for KENS (spallation neutron source at KEK). A further investigation to certify the optimum HIP conditions was made with the small punch test method. The results showed that the optimum temperature was 1500 °C at which the W/Ta interface gave the strongest fracture strength. In the case of the block with a hole for thermocouple, it was found that the fabrication preciseness of a straight hole and a tantalum sheath influenced the results. The development of a tungsten stainless-steel alloy was tried to produce a bare tungsten target, using techniques in powder metallurgy. Corrosion tests for various tungsten alloys were made while varying the water temperature and velocity. The mass loss of tungsten in very slow water at 180 °C was as low as 0.022 mg/y, but increased remarkably with water velocity. Simulation experiments for radiation damage to supplement the STIP-III experiments were made to investigate material hardening by hydrogen and helium, and microstructures irradiated by electrons. Both experiments showed consistent results on the order of the dislocation numbers and irradiation hardness among the different tungsten materials. Thermal-hydraulic designs were made for two types of solid target system of tungsten: slab and rod geometry as a function of the proton beam power. The neutronic performance of a solid target system was compared with that of mercury target based on Monte Carlo calculations by using the MCNP code.

Time-resolved microscopy reveals the driving mechanism of particle formation during ultrashort pulse laser ablation of dentin-like ivory

NASA Astrophysics Data System (ADS)

Domke, Matthias; Gavrilova, Anna; Rapp, Stephan; Frentzen, Matthias; Meister, Joerg; Huber, Heinz P.

2015-07-01

In dental health care, the application of ultrashort laser pulses enables dental tissue ablation free from thermal side effects, such as melting and cracking. However, these laser types create undesired micro- and nanoparticles, which might cause a health risk for the patient or surgeon. The aim of this study was to investigate the driving mechanisms of micro- and nanoparticle formation during ultrashort pulse laser ablation of dental tissue. Time-resolved microscopy was chosen to observe the ablation dynamics of mammoth ivory after irradiation with 660 fs laser pulses. The results suggest that nanoparticles might arise in the excited region. The thermal expansion of the excited material induces high pressure in the surrounding bulk tissue, generating a pressure wave. The rarefaction wave behind this pressure wave causes spallation, leading to ejection of microparticles.

Working group summary report on effects of pulsed operation

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

Gabriel, T.A.; Ni, L.

1996-06-01

In a short pulsed spallation neutron source, extremely high energy ({approx_gt}1 GeV) proton beam pulses are injected into a liquid metal target in a very short period of time ({approximately}1 {mu}sec) at a high repetition rate ({approximately}50 Hertz). The beam energy will be deposited in the target materials (such as mercury or lead) and converted into heat. It causes a sudden temperature rise and resulting pressure wave. This pressure wave travels through the liquid, reaches the steel container wall and may possibly lead to material damage due to induced stress. Almost all participants agreed that the shock problem due tomore » the short pulse operation in the liquid metal target could be serious and could present a challenging problem. It was determined that the following points need to be addressed: (1) equation of state for mercury (2) code validation and benchmark experiments (3) shock effects on the entire target system (4) two phase flow by gas injection. All these investigations should be carried out in the framework of international cooperation. Two small scaled Hg pressure pulse tests are planned at ORNL to provide insight into the pressure wave propagation and thermal shock effects. One experiment will use exploding wires to generate the pulse pressure, the other the electron beam at ORELA. Also PSI, LANL, CERN (ISOLDE facility), INR and IPPE could contribute to the experimental methods for producing shock. The necessary R&D for bubble injection might be performed at PSI, RIGA, ORNL or Ben-Gurion University. All of the above experiments can possibly yield benchmarking data which is absolutely necessary for code validation.« less

Cavitation Damage Experiments for Mercury Spallation Targets At the LANSCE WNR in 2008

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

Riemer, Bernie; Wendel, Mark W; Felde, David K

2010-01-01

Proton beam experiments investigating cavitation damage in short pulse mercury spallation targets were performed at LANSCE WNR in July of 2008. They included two main areas for investigation: damage dependence on mercury velocity using geometry more prototypic to the SNS target than previously employed and damage dependence on incident proton beam flux intensity. The flow dependence experiment employed six test targets with mercury velocity in the channel ranging from 0 to more than 4 m/s. Each was hit with 100 WNR beam pulses with peak proton flux equivalent to that of SNS operating at 2.7 MW. Damage dependence on incidentmore » proton beam flux intensity was also investigated with three intensity levels used on simple rectangular shaped targets without mercury flow. Intensity variation was imposed by focusing the beam differently while maintaining protons per pulse. This kept total energy deposited in each target constant. A fourth test target was hit with various beams: constant protons and varied spot size; constant spot size and varied protons. No damage will be assessed in this case. Instead, acoustic emissions associated with cavitation collapse were measured by laser Doppler vibrometer (LDV) from readings of exterior vessel motions as well as by mercury wetted acoustic transducers. This paper will provide a description of the experiment and present available results. Damage assessment will require several months before surface analysis can be completed and was not available in time for IWSMT-9.« less

Non-invasive characterisation of SIX Japanese hand-guards (tsuba)

NASA Astrophysics Data System (ADS)

Barzagli, Elisa; Grazzi, Francesco; Civita, Francesco; Scherillo, Antonella; Pietropaolo, Antonino; Festa, Giulia; Zoppi, Marco

2013-12-01

In this work we present a systematic study of Japanese sword hand-guards ( tsuba) carried out by means of non-invasive techniques using neutrons. Several tsuba from different periods, belonging to the Japanese Section of the Stibbert Museum, were analysed using an innovative approach to characterise the bulk of the samples, coupling two neutron techniques, namely Time of Flight Neutron Diffraction (ToF-ND) and Nuclear Resonance Capture Analysis (NRCA). The measurements were carried out on the same instrument: the INES beam-line at the ISIS spallation pulsed neutron source (UK). NRCA analysis allows identifying the elements present in the sample gauge volume, while neutron diffraction is exploited to quantify the phase distribution and other micro-structural parameters of the metal specimen. The results show that all samples are made of high-quality metal, either steel or copper alloy, with noticeable changes in composition and working techniques, depending on the place and time of manufacturing.

High efficiency laser-assisted H - charge exchange for microsecond duration beams

DOE PAGES

Cousineau, Sarah; Rakhman, Abdurahim; Kay, Martin; ...

2017-12-26

Laser-assisted stripping is a novel approach to H - charge exchange that overcomes long-standing limitations associated with the traditional, foil-based method of producing high-intensity, time-structured beams of protons. This paper reports on the first successful demonstration of the laser stripping technique for microsecond duration beams. The experiment represents a factor of 1000 increase in the stripped pulse duration compared with the previous proof-of-principle demonstration. The central theme of the experiment is the implementation of methods to reduce the required average laser power such that high efficiency stripping can be accomplished for microsecond duration beams using conventional laser technology. In conclusion,more » the experiment was performed on the Spallation Neutron Source 1 GeV H - beam using a 1 MW peak power UV laser and resulted in ~95% stripping efficiency.« less

High efficiency laser-assisted H - charge exchange for microsecond duration beams

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

Cousineau, Sarah; Rakhman, Abdurahim; Kay, Martin

Laser-assisted stripping is a novel approach to H - charge exchange that overcomes long-standing limitations associated with the traditional, foil-based method of producing high-intensity, time-structured beams of protons. This paper reports on the first successful demonstration of the laser stripping technique for microsecond duration beams. The experiment represents a factor of 1000 increase in the stripped pulse duration compared with the previous proof-of-principle demonstration. The central theme of the experiment is the implementation of methods to reduce the required average laser power such that high efficiency stripping can be accomplished for microsecond duration beams using conventional laser technology. In conclusion,more » the experiment was performed on the Spallation Neutron Source 1 GeV H - beam using a 1 MW peak power UV laser and resulted in ~95% stripping efficiency.« less

Method of using deuterium-cluster foils for an intense pulsed neutron source

DOEpatents

Miley, George H.; Yang, Xiaoling

2013-09-03

A method is provided for producing neutrons, comprising: providing a converter foil comprising deuterium clusters; focusing a laser on the foil with power and energy sufficient to cause deuteron ions to separate from the foil; and striking a surface of a target with the deuteron ions from the converter foil with energy sufficient to cause neutron production by a reaction selected from the group consisting of D-D fusion, D-T fusion, D-metal nuclear spallation, and p-metal. A further method is provided for assembling a plurality of target assemblies for a target injector to be used in the previously mentioned manner. A further method is provided for producing neutrons, comprising: splitting a laser beam into a first beam and a second beam; striking a first surface of a target with the first beam, and an opposite second surface of the target with the second beam with energy sufficient to cause neutron production.

New large volume hydrothermal reaction cell for studying chemical processes under supercritical hydrothermal conditions using time-resolved in situ neutron diffraction.

PubMed

Ok, Kang Min; O'Hare, Dermot; Smith, Ronald I; Chowdhury, Mohammed; Fikremariam, Hanna

2010-12-01

The design and testing of a new large volume Inconel pressure cell for the in situ study of supercritical hydrothermal syntheses using time-resolved neutron diffraction is introduced for the first time. The commissioning of this new cell is demonstrated by the measurement of the time-of-flight neutron diffraction pattern for TiO(2) (Anatase) in supercritical D(2)O on the POLARIS diffractometer at the United Kingdom's pulsed spallation neutron source, ISIS, Rutherford Appleton Laboratory. The sample can be studied over a wide range of temperatures (25-450 °C) and pressures (1-355 bar). This novel apparatus will now enable us to study the kinetics and mechanisms of chemical syntheses under extreme environments such as supercritical water, and in particular to study the crystallization of a variety of technologically important inorganic materials.

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.

Incineration of nuclear waste by accelerator

NASA Astrophysics Data System (ADS)

Martino, J.; Fioni, G.; Leray, S.

1998-10-01

An important international effort is devoted to find a suitable solution to incinerate radioactive nuclear waste issued from conventional power plants and from nuclear disarmament. Practically all innovative projects consist of a sub critical system driven by an external neutron source obtained by spallation induced by a high intensity proton accelerator irradiating a heavy target. New nuclear data measurements are necessary for the realization of these systems, in particular a good knowledge of the spallation process and of the neutron cross sections for transuranic elements are essential.

Numerical Simulations of Thermo-Mechanical Processes during Thermal Spallation Drilling for Geothermal Reservoirs

NASA Astrophysics Data System (ADS)

Vogler, D.; Walsh, S. D. C.; Rudolf von Rohr, P.; Saar, M. O.

2017-12-01

Drilling expenses constitute a significant share of the upfront capital costs and thereby the associated risks of geothermal energy production. This is especially true for deep boreholes, as drilling costs per meter increase significantly with depth. Thermal spallation drilling is a relatively new drilling technique, particularly suited to the hard crystalline (e.g., basement) rocks in which many deep geothermal resources are located. The method uses a hot jet-flame to rapidly heat the rock surface, which leads to large temperature gradients in the rock. These temperature gradients cause localized thermal stresses that, in combination with the in situ stress field, lead to the formation and ejection of spalls. These spalls are then transported out of the borehole with the drilling mud. Thermal spallation not only in principle enables much faster rates of penetration than traditional rotary drilling, but is also contact-less, which significantly reduces the long tripping times associated with conventional rotary head drilling. We present numerical simulations investigating the influence of rock heterogeneities on the thermal spallation process. Special emphasis is put on different mineral compositions, stress regimes, and heat sources.

SINQ layout, operation, applications and R&D to high power

NASA Astrophysics Data System (ADS)

Bauer, G. S.; Dai, Y.; Wagner, W.

2002-09-01

Since 1997, the Paul Scherrer Institut (PSI) is operating a 1 MW class research spallation neutron source, named SINQ. SINQ is driven by a cascade of three accelerators, the final stage being a 590 MeV isochronous ring cyclotron which delivers a beam current of 1.8 mA at an rf-frequency of 51 MHz. Since for neutron production this is essentially a dc-device, SINQ is a continuous neutron source and is optimized in its design for high time average neutron flux. This makes the facility similar to a research reactor in terms of utilization, but, in terms of beam power, it is, by a large margin, the most powerful spallation neutron source currently in operation world wide. As a consequence, target load levels prevail in SINQ which are beyond the realm of existing experience, demanding a careful approach to the design and operation of a high power target. While the best neutronic performance of the source is expected for a liquid lead-bismuth eutectic target, no experience with such systems exists. For this reason a staged approach has been embarked upon, starting with a heavy water cooled rod target of Zircaloy-2 and proceeding via steel clad lead rods towards the final goal of a target optimised in both, neutronic performance and service life time. Experience currently accruing with a test target containing sample rods with different materials specimens will help to select the proper structural material and make dependable life time estimates accounting for the real operating conditions that prevail in the facility. In parallel, both theoretical and experimental work is going on within the MEGAPIE (MEGAwatt Pilot Experiment) project, a joint initiative by six European research institutions and JAERI (Japan), DOE (USA) and KAERI (Korea), to design, build, operate and explore a liquid lead-bismuth spallation target for 1MW of beam power, taking advantage of the existing spallation neutron facility SINQ.

Spallation as a dominant source of pusher-fuel and hot-spot mix in inertial confinement fusion capsules

DOE PAGES

Orth, Charles D.

2016-02-23

We suggest that a potentially dominant but previously neglected source of pusher-fuel and hot-spot “mix” may have been the main degradation mechanism for fusion energy yields of modern inertial confinement fusion (ICF) capsules designed and fielded to achieve high yields — not hydrodynamic instabilities. This potentially dominant mix source is the spallation of small chunks or “grains” of pusher material into the fuel regions whenever (1) the solid material adjacent to the fuel changes its phase by nucleation, and (2) this solid material spalls under shock loading and sudden decompression. Finally, we describe this mix mechanism, support it with simulationsmore » and experimental evidence, and explain how to eliminate it and thereby allow higher yields for ICF capsules and possibly ignition at the National Ignition Facility.« less

rf improvements for Spallation Neutron Source H- ion source.

PubMed

Kang, Y W; Fuja, R; Goulding, R H; Hardek, T; Lee, S-W; McCarthy, M P; Piller, M C; Shin, K; Stockli, M P; Welton, R F

2010-02-01

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering approximately 38 mA H(-) beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

Moderator Demonstration Facility Design and Optimization

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

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

2017-02-01

The Spallation Neutron Source (SNS) facility at Oak Ridge National Laboratory (ORNL) is implementing a Moderator Demonstration Facility (MDF) to demonstrate the performance characteristics of advanced moderators central to the Second Target Station (STS) for SNS. The MDF will use the "spare" front-end installation within the SNS accelerator support complex – an ion source, radio-frequency quadrupole (RFQ) accelerator, and medium-energy beam transport (MEBT) chopper - to provide a 2.5 MeV proton beam of peak current 50 mA and maximum pulse length of less than 10 s at a repetition rate of no more than 60 Hz to a suitable neutron-producingmore » target to demonstrate those aspects of moderator performance necessary to meet the goals of the STS design e ort. The accelerator beam parameters are not open to variation beyond that described above - they are fixed by the nature of the spare front-end installation (the Integrated Test Stand Facility; ITSF). Accordingly, there are some neutronic challenges in developing prototypic moderator illumination from a very non-prototypic primary neutron source; the spallation source we are attempting to mimic has an extended neutron source volume approximately 40 cm long (in the direction of the proton beam), approximately 10 cm wide (horizontally transverse to the proton beam) and approximately 5 cm high (vertically transverse to the proton beam), and an isotropic evaporation energy spectrum with mean energy above 1 MeV. In contrast, the primary neutron source available from the 7Li(p,n) reaction (the most prolific at 2.5 MeV proton energy by more than an order of magnitude) is strongly anisotropic, with an energy spectrum that is both strongly dependent on emission angle and kinematically limited to less than 700 keV, and the interaction zone between the incident protons and any target material (neutron-producing or not) is intrinsically limited to a few tens of microns. The MDF will be unique and innovative amongst the world’s moderator test facilities in that it will be intended to be very prototypic in terms of "moderator illumination" - the spatial variation of the neutron flux entering the moderator itself - as well as capable of testing so-called high-brightness moderators in a wing configuration.« less

Detection of spallation neutrons and protons using the (nat)Cd activation technique in transmutation experiments at Dubna.

PubMed

Manolopoulou, M; Stoulos, S; Fragopoulou, M; Brandt, R; Westmeier, W; Krivopustov, M; Sosnin, A; Zamani, M

2006-07-01

Various spallation sources have been used to transmute long-lived radioactive waste, mostly making use of the wide energy neutron fluence. In addition to neutrons, a large number of protons and gamma rays are also emitted from these sources. In this paper (nat)Cd is proved to be a useful activation detector for determining both thermal-epithermal neutron as well as secondary proton fluences. The fluences measured with (nat)Cd compared with other experimental data and calculations of DCM-DEM code were found to be in reasonable agreement. An accumulation of thermal-epithermal neutrons around the center of the target (i.e. after approx. 10 cm) and of secondary protons towards the end of the target is observed.

Simulation of a beam rotation system for a spallation source

NASA Astrophysics Data System (ADS)

Reiss, Tibor; Reggiani, Davide; Seidel, Mike; Talanov, Vadim; Wohlmuther, Michael

2015-04-01

With a nominal beam power of nearly 1 MW on target, the Swiss Spallation Neutron Source (SINQ), ranks among the world's most powerful spallation neutron sources. The proton beam transport to the SINQ target is carried out exclusively by means of linear magnetic elements. In the transport line to SINQ the beam is scattered in two meson production targets and as a consequence, at the SINQ target entrance the beam shape can be described by Gaussian distributions in transverse x and y directions with tails cut short by collimators. This leads to a highly nonuniform power distribution inside the SINQ target, giving rise to thermal and mechanical stresses. In view of a future proton beam intensity upgrade, the possibility of homogenizing the beam distribution by means of a fast beam rotation system is currently under investigation. Important aspects which need to be studied are the impact of a rotating proton beam on the resulting neutron spectra, spatial flux distributions and additional—previously not present—proton losses causing unwanted activation of accelerator components. Hence a new source description method was developed for the radiation transport code MCNPX. This new feature makes direct use of the results from the proton beam optics code TURTLE. Its advantage to existing MCNPX source options is that all phase space information and correlations of each primary beam particle computed with TURTLE are preserved and transferred to MCNPX. Simulations of the different beam distributions together with their consequences in terms of neutron production are presented in this publication. Additionally, a detailed description of the coupling method between TURTLE and MCNPX is provided.

RF H-minus ion source development in China spallation neutron source

NASA Astrophysics Data System (ADS)

Chen, W.; Ouyang, H.; Xiao, Y.; Liu, S.; Lü, Y.; Cao, X.; Huang, T.; Xue, K.

2017-08-01

China Spallation Neutron Source (CSNS) phase-I project currently uses a Penning surface plasma H- ion source, which has a life time of several weeks with occasional sparks between high voltage electrodes. To extend the life time of the ion source and prepare for the CSNS phase-II, we are trying to develop a RF negative hydrogen ion source with external antenna. The configuration of the source is similar to the DESY external antenna ion source and SNS ion source. However several changes are made to improve the stability and the life time. Firstly, Si3N4 ceramic with high thermal shock resistance, and high thermal conductivity is used for plasma chamber, which can endure an average power of 2000W. Secondly, the water-cooled antenna is brazed on the chamber to improve the energy efficiency. Thirdly, cesium is injected directly to the plasma chamber if necessary, to simplify the design of the converter and the extraction. Area of stainless steel exposed to plasma is minimized to reduce the sputtering and degassing. Instead Mo, Ta, and Pt coated materials are used to face the plasma, which makes the self-cleaning of the source possible.

Impedance measurements of the extraction kicker system for the rapid cycling synchrotron of China Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Huang, Liang-Sheng; Wang, Sheng; Liu, Yu-Dong; Li, Yong; Liu, Ren-Hong; Xiao, Ou-Zheng

2016-04-01

The fast extraction kicker system is one of the most important accelerator components and the main source of impedance in the Rapid Cycling Synchrotron of the China Spallation Neutron Source. It is necessary to understand the kicker impedance before its installation into the tunnel. Conventional and improved wire methods are employed in the impedance measurement. The experimental results for the kicker impedance are explained by comparison with simulation using CST PARTICLE STUDIO. The simulation and measurement results confirm that the window-frame ferrite geometry and the end plate are the important structures causing coupling impedance. It is proved in the measurements that the mismatching from the power form network to the kicker leads to a serious oscillation sideband of the longitudinal and vertical impedance and the oscillation can be reduced by ferrite absorbing material. Supported by National Natural Science Foundation of China (11175193, 11275221)

Radiative neutron capture as a counting technique at pulsed spallation neutron sources: a review of current progress

NASA Astrophysics Data System (ADS)

Schooneveld, E. M.; Pietropaolo, A.; Andreani, C.; Perelli Cippo, E.; Rhodes, N. J.; Senesi, R.; Tardocchi, M.; Gorini, G.

2016-09-01

Neutron scattering techniques are attracting an increasing interest from scientists in various research fields, ranging from physics and chemistry to biology and archaeometry. The success of these neutron scattering applications is stimulated by the development of higher performance instrumentation. The development of new techniques and concepts, including radiative capture based neutron detection, is therefore a key issue to be addressed. Radiative capture based neutron detectors utilize the emission of prompt gamma rays after neutron absorption in a suitable isotope and the detection of those gammas by a photon counter. They can be used as simple counters in the thermal region and (simultaneously) as energy selector and counters for neutrons in the eV energy region. Several years of extensive development have made eV neutron spectrometers operating in the so-called resonance detector spectrometer (RDS) configuration outperform their conventional counterparts. In fact, the VESUVIO spectrometer, a flagship instrument at ISIS serving a continuous user programme for eV inelastic neutron spectroscopy measurements, is operating in the RDS configuration since 2007. In this review, we discuss the physical mechanism underlying the RDS configuration and the development of associated instrumentation. A few successful neutron scattering experiments that utilize the radiative capture counting techniques will be presented together with the potential of this technique for thermal neutron diffraction measurements. We also outline possible improvements and future perspectives for radiative capture based neutron detectors in neutron scattering application at pulsed neutron sources.

Improved design of proton source and low energy beam transport line for European Spallation Source

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

Neri, L., E-mail: neri@lns.infn.it; Celona, L.; Gammino, S.

2014-02-15

The design update of the European Spallation Source (ESS) accelerator is almost complete and the construction of the prototype of the microwave discharge ion source able to provide a proton beam current larger than 70 mA to the 3.6 MeV Radio Frequency Quadrupole (RFQ) started. The source named PS-ESS (Proton Source for ESS) was designed with a flexible magnetic system and an extraction system able to merge conservative solutions with significant advances. The ESS injector has taken advantage of recent theoretical updates and new plasma diagnostics tools developed at INFN-LNS (Laboratori Nazionali del Sud, Istituto Nazionale di Fisica Nucleare). Themore » design strategy considers the PS-ESS and the low energy beam transport line as a whole, where the proton beam behaves like an almost neutralized non-thermalized plasma. Innovative solutions have been used as hereinafter described. Thermo-mechanical optimization has been performed to withstand the chopped beam and the misaligned focused beam over the RFQ input collimator; the results are reported here.« less

rf improvements for Spallation Neutron Source H- ion sourcea)

NASA Astrophysics Data System (ADS)

Kang, Y. W.; Fuja, R.; Goulding, R. H.; Hardek, T.; Lee, S.-W.; McCarthy, M. P.; Piller, M. C.; Shin, K.; Stockli, M. P.; Welton, R. F.

2010-02-01

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering ˜38 mA H- beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

Overview of the Conceptual Design of the Future VENUS Neutron Imaging Beam Line at the Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Bilheux, Hassina; Herwig, Ken; Keener, Scott; Davis, Larry

VENUS (Versatile Neutron Imaging Beam line at the Spallation Neutron Source) will be a world-class neutron-imaging instrument that will uniquely utilize the Spallation Neutron Source (SNS) time-of-flight (TOF) capabilities to measure and characterize objects across several length scales (mm to μm). When completed, VENUS will provide academia, industry and government laboratories with the opportunity to advance scientific research in areas such as energy, materials, additive manufacturing, geosciences, transportation, engineering, plant physiology, biology, etc. It is anticipated that a good portion of the VENUS user community will have a strong engineering/industrial research focus. Installed at Beam line 10 (BL10), VENUS will be a 25-m neutron imaging facility with the capability to fully illuminate (i.e., umbra illumination) a 20 cm x 20 cm detector area. The design allows for a 28 cm x 28 cm field of view when using the penumbra to 80% of the full illumination flux. A sample position at 20 m will be implemented for magnification measurements. The optical components are comprised of a series of selected apertures, T0 and bandwidth choppers, beam scrapers, a fast shutter to limit sample activation, and flight tubes filled with Helium. Techniques such as energy selective, Bragg edge and epithermal imaging will be available at VENUS.

Calculation Package: Derivation of Facility-Specific Derived Air Concentration (DAC) Values in Support of Spallation Neutron Source Operations

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

McLaughlin, David A

Derived air concentration (DAC) values for 175 radionuclides* produced at the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source (SNS), but not listed in Appendix A of 10 CFR 835 (01/01/2009 version), are presented. The proposed DAC values, ranging between 1 E-07 {micro}Ci/mL and 2 E-03 {micro}Ci/mL, were calculated in accordance with the recommendations of the International Commission on Radiological Protection (ICRP), and are intended to support an exemption request seeking regulatory relief from the 10 CFR 835, Appendix A, requirement to apply restrictive DACs of 2E-13 {micro}Ci/mL and 4E-11 {micro}Ci/mL and for non-listed alpha and non-alpha-emitting radionuclides, respectively.

Dynamic fracture of tantalum under extreme tensile stress.

PubMed

Albertazzi, Bruno; Ozaki, Norimasa; Zhakhovsky, Vasily; Faenov, Anatoly; Habara, Hideaki; Harmand, Marion; Hartley, Nicholas; Ilnitsky, Denis; Inogamov, Nail; Inubushi, Yuichi; Ishikawa, Tetsuya; Katayama, Tetsuo; Koyama, Takahisa; Koenig, Michel; Krygier, Andrew; Matsuoka, Takeshi; Matsuyama, Satoshi; McBride, Emma; Migdal, Kirill Petrovich; Morard, Guillaume; Ohashi, Haruhiko; Okuchi, Takuo; Pikuz, Tatiana; Purevjav, Narangoo; Sakata, Osami; Sano, Yasuhisa; Sato, Tomoko; Sekine, Toshimori; Seto, Yusuke; Takahashi, Kenjiro; Tanaka, Kazuo; Tange, Yoshinori; Togashi, Tadashi; Tono, Kensuke; Umeda, Yuhei; Vinci, Tommaso; Yabashi, Makina; Yabuuchi, Toshinori; Yamauchi, Kazuto; Yumoto, Hirokatsu; Kodama, Ryosuke

2017-06-01

The understanding of fracture phenomena of a material at extremely high strain rates is a key issue for a wide variety of scientific research ranging from applied science and technological developments to fundamental science such as laser-matter interaction and geology. Despite its interest, its study relies on a fine multiscale description, in between the atomic scale and macroscopic processes, so far only achievable by large-scale atomic simulations. Direct ultrafast real-time monitoring of dynamic fracture (spallation) at the atomic lattice scale with picosecond time resolution was beyond the reach of experimental techniques. We show that the coupling between a high-power optical laser pump pulse and a femtosecond x-ray probe pulse generated by an x-ray free electron laser allows detection of the lattice dynamics in a tantalum foil at an ultrahigh strain rate of [Formula: see text] ~2 × 10 8 to 3.5 × 10 8 s -1 . A maximal density drop of 8 to 10%, associated with the onset of spallation at a spall strength of ~17 GPa, was directly measured using x-ray diffraction. The experimental results of density evolution agree well with large-scale atomistic simulations of shock wave propagation and fracture of the sample. Our experimental technique opens a new pathway to the investigation of ultrahigh strain-rate phenomena in materials at the atomic scale, including high-speed crack dynamics and stress-induced solid-solid phase transitions.

Dynamic fracture of tantalum under extreme tensile stress

PubMed Central

Albertazzi, Bruno; Ozaki, Norimasa; Zhakhovsky, Vasily; Faenov, Anatoly; Habara, Hideaki; Harmand, Marion; Hartley, Nicholas; Ilnitsky, Denis; Inogamov, Nail; Inubushi, Yuichi; Ishikawa, Tetsuya; Katayama, Tetsuo; Koyama, Takahisa; Koenig, Michel; Krygier, Andrew; Matsuoka, Takeshi; Matsuyama, Satoshi; McBride, Emma; Migdal, Kirill Petrovich; Morard, Guillaume; Ohashi, Haruhiko; Okuchi, Takuo; Pikuz, Tatiana; Purevjav, Narangoo; Sakata, Osami; Sano, Yasuhisa; Sato, Tomoko; Sekine, Toshimori; Seto, Yusuke; Takahashi, Kenjiro; Tanaka, Kazuo; Tange, Yoshinori; Togashi, Tadashi; Tono, Kensuke; Umeda, Yuhei; Vinci, Tommaso; Yabashi, Makina; Yabuuchi, Toshinori; Yamauchi, Kazuto; Yumoto, Hirokatsu; Kodama, Ryosuke

2017-01-01

The understanding of fracture phenomena of a material at extremely high strain rates is a key issue for a wide variety of scientific research ranging from applied science and technological developments to fundamental science such as laser-matter interaction and geology. Despite its interest, its study relies on a fine multiscale description, in between the atomic scale and macroscopic processes, so far only achievable by large-scale atomic simulations. Direct ultrafast real-time monitoring of dynamic fracture (spallation) at the atomic lattice scale with picosecond time resolution was beyond the reach of experimental techniques. We show that the coupling between a high-power optical laser pump pulse and a femtosecond x-ray probe pulse generated by an x-ray free electron laser allows detection of the lattice dynamics in a tantalum foil at an ultrahigh strain rate of ε. ~2 × 108 to 3.5 × 108 s−1. A maximal density drop of 8 to 10%, associated with the onset of spallation at a spall strength of ~17 GPa, was directly measured using x-ray diffraction. The experimental results of density evolution agree well with large-scale atomistic simulations of shock wave propagation and fracture of the sample. Our experimental technique opens a new pathway to the investigation of ultrahigh strain-rate phenomena in materials at the atomic scale, including high-speed crack dynamics and stress-induced solid-solid phase transitions. PMID:28630909

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

Albertazzi, Bruno; Ozaki, Norimasa; Zhakhovsky, Vasily

The understanding of fracture phenomena of a material at extremely high strain rates is a key issue for a wide variety of scientific research ranging from applied science and technological developments to fundamental science such as laser-matter interaction and geology. Despite its interest, its study relies on a fine multiscale description, in between the atomic scale and macroscopic processes, so far only achievable by large-scale atomic simulations. Direct ultrafast real-time monitoring of dynamic fracture (spallation) at the atomic lattice scale with picosecond time resolution was beyond the reach of experimental techniques. We show that the coupling between a high-power opticalmore » laser pump pulse and a femtosecond x-ray probe pulse generated by an x-ray free electron laser allows detection of the lattice dynamics in a tantalum foil at an ultrahigh strain rate of Embedded Image ~2 × 10 8 to 3.5 × 10 8 s -1. A maximal density drop of 8 to 10%, associated with the onset of spallation at a spall strength of ~17 GPa, was directly measured using x-ray diffraction. The experimental results of density evolution agree well with large-scale atomistic simulations of shock wave propagation and fracture of the sample. Our experimental technique opens a new pathway to the investigation of ultrahigh strain-rate phenomena in materials at the atomic scale, including high-speed crack dynamics and stress-induced solid-solid phase transitions.« less

New Insights into the Explosion Source from SPE

NASA Astrophysics Data System (ADS)

Patton, H. J.

2015-12-01

Phase I of the Source Physics Experiments (SPE) is a series of chemical explosions at varying depths and yields detonated in the same emplacement hole on Climax stock, a granitic pluton located on the Nevada National Security Site. To date, four of the seven planned tests have been conducted, the last in May 2015, called SPE-4P, with a scaled depth of burial of 1549 m/kt1/3 in order to localize the source in time and space. Surface ground motions validated that the source medium did not undergo spallation, and a key experimental objective was achieved where SPE-4P is the closest of all tests in the series to a pure monopole source and will serve as an empirical Green's function for analysis against other SPE tests. A scientific objective of SPE is to understand mechanisms of rock damage for generating seismic waves, particularly surface and S waves, including prompt damage under compressive stresses and "late-time" damage under tensile stresses. Studies have shown that prompt damage can explain ~75% of the seismic moment for some SPE tests. Spallation is a form of late-time damage and a facilitator of damage mechanisms under tensile stresses including inelastic brittle deformation and shear dilatancy on pre-existing faults or joints. As an empirical Green's function, SPE-4P allows the study of late-time damage mechanisms on other SPE tests that induce spallation and late-time damage, and I'll discuss these studies. The importance for nuclear monitoring cannot be overstated because new research shows that damage mechanisms can affect surface wave magnitude Ms more than tectonic release, and are a likely factor related to anomalous mb-Ms behavior for North Korean tests.

Double differential cross section calculations for 16O and 90Zr elements

NASA Astrophysics Data System (ADS)

Demirkol, İ.

2018-04-01

Double differential cross sections in proton induced reactions on 90Zr and O2 (inert matrix fuel) is calculated at the bombarding energies between 29 and 300 MeV. The proton-induced nuclear reaction cross section data can be used in technical applications such as the isotope production alternatives, spallation reactions for production of neutrons in spallation neutron source, etc. In this study, the cascade excition model including the effect of preequilibrium is used to calculate the differential cross section. Then, the obtained results are discussed and compared with available experimental data.

Single-shot femtosecond laser ablation of gold surface in air and isopropyl alcohol

NASA Astrophysics Data System (ADS)

Kudryashov, S. I.; Saraeva, I. N.; Lednev, V. N.; Pershin, S. M.; Rudenko, A. A.; Ionin, A. A.

2018-05-01

Single-shot IR femtosecond-laser ablation of gold surfaces in ambient air and liquid isopropyl alcohol was studied by scanning electron microscopy characterization of crater topographies and time-resolved optical emission spectroscopy of ablative plumes in regimes, typical for non-filamentary and non-fragmentation laser production of nanoparticle sols. Despite one order of magnitude shorter (few nanoseconds) lifetimes and almost two orders of magnitude lower intensities of the quenched ablative plume emission in the alcohol ambient at the same peak laser fluence, craters for the dry and wet conditions appeared with rather similar nanofoam-like spallative topographies and the same thresholds. These facts envision the underlying surface spallation as one of the basic ablation mechanisms relevant for both dry and wet advanced femtosecond laser surface nano/micro-machining and texturing, as well as for high-throughput femtosecond laser ablative production of colloidal nanoparticles by MHz laser-pulse trains via their direct nanoscale jetting from the nanofoam in air and fluid environments.

Student Tutorials II

NASA Astrophysics Data System (ADS)

Student Tutorials

2006-05-01

(Open to all conferees) Lunch followed by a tour of the Spallation Neutron Source and Center for Nanophase Materials at of Oak Ridge National Laboratory. Buses leave from the University of Tenessee-Knoxville Nielsen Physics Building.

RF Conditioning and Testing of Fundamental Power Couplers for SNS Superconducting Cavity Production

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

M. Stirbet; G.K. Davis; M. A. Drury

The Spallation Neutron Source (SNS) makes use of 33 medium beta (0.61) and 48 high beta (0.81) superconducting cavities. Each cavity is equipped with a fundamental power coupler, which should withstand the full klystron power of 550 kW in full reflection for the duration of an RF pulse of 1.3 msec at 60 Hz repetition rate. Before assembly to a superconducting cavity, the vacuum components of the coupler are submitted to acceptance procedures consisting of preliminary quality assessments, cleaning and clean room assembly, vacuum leak checks and baking under vacuum, followed by conditioning and RF high power testing. Similar acceptancemore » procedures (except clean room assembly and baking) were applied for the airside components of the coupler. All 81 fundamental power couplers for SNS superconducting cavity production have been RF power tested at JLAB Newport News and, beginning in April 2004 at SNS Oak Ridge. This paper gives details of coupler processing and RF high power-assessed performances.« less

Immersive Visual Analytics for Transformative Neutron Scattering Science

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

Steed, Chad A; Daniel, Jamison R; Drouhard, Margaret

The ORNL Spallation Neutron Source (SNS) provides the most intense pulsed neutron beams in the world for scientific research and development across a broad range of disciplines. SNS experiments produce large volumes of complex data that are analyzed by scientists with varying degrees of experience using 3D visualization and analysis systems. However, it is notoriously difficult to achieve proficiency with 3D visualizations. Because 3D representations are key to understanding the neutron scattering data, scientists are unable to analyze their data in a timely fashion resulting in inefficient use of the limited and expensive SNS beam time. We believe a moremore » intuitive interface for exploring neutron scattering data can be created by combining immersive virtual reality technology with high performance data analytics and human interaction. In this paper, we present our initial investigations of immersive visualization concepts as well as our vision for an immersive visual analytics framework that could lower the barriers to 3D exploratory data analysis of neutron scattering data at the SNS.« less

Superconducting thermal neutron detectors

NASA Astrophysics Data System (ADS)

Merlo, V.; Pietropaolo, A.; Celentano, G.; Cirillo, M.; Lucci, M.; Ottaviani, I.; Salvato, M.; Scherillo, A.; Schooneveld, E. M.; Vannozzi, A.

2016-09-01

A neutron detection concept is presented that is based on superconductive niobium nitride (NbN) strips coated by a boron (B) layer. The working principle is well described by a hot spot mechanism: upon the occurrence of the nuclear reactions n + 10B → α + 7Li + 2.8 MeV, the energy released by the secondary particles into the strip induces a superconducting-normal state transition. The latter is recognized as a voltage signal which is the evidence of the incident neutron. The above described detection principle has been experimentally assessed and verified by irradiating the samples with a pulsed neutron beam at the ISIS spallation neutron source (UK). It is found that the boron coated superconducting strips, kept at a temperature T below 11K and current-biased below the critical current IC, are driven into the normal state upon thermal neutron irradiation. Measurements on the counting rate of the device are presented and the basic physical features of the detector are discussed and compared to those of a borated Nb superconducting strip.

Ablation of gold irradiated by femtosecond laser pulse: Experiment and modeling

NASA Astrophysics Data System (ADS)

Ashitkov, S. I.; Komarov, P. S.; Zhakhovsky, V. V.; Petrov, Yu V.; Khokhlov, V. A.; Yurkevich, A. A.; Ilnitsky, D. K.; Inogamov, N. A.; Agranat, M. B.

2016-11-01

We report on the ablation phenomena in gold sample irradiated by femtosecond laser pulses of moderate intensity. Dynamics of optical constants and expansion of a heated surface layer was investigated in a range from picosecond up to subnanosecond using ultrafast interferometry. Also morphology of the ablation craters and value of an ablation threshold (for absorbed fluence) were measured. The experimental data are compared with simulations of mass flows obtained by two-temperature hydrodynamics and molecular dynamics methods. Simulation shows evolution of a thin surface layer pressurized by a laser pulse. Unloading of the pressurized layer proceeds together with electron-ion thermalization, melting, cavitation and spallation of a part of surface liquid layer. The experimental and simulation results on two-temperature physics and on a fracture, surface morphology and strength of liquid gold at a strain rate ∼ 109 s-1 are discussed.

The Manuel Lujan, Jr. Neutron Scattering Center, LANSCE experiment reports: 1990 Run Cycle

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

DiStravolo, M.A.

1991-10-01

This year was the third in which LANSCE ran a formal user program. A call for proposals was issued before the scheduled run cycles, and experiment proposals were submitted by scientists from universities, industry, and other research facilities around the world. An external program advisory committee, which LANSCE shares with the Intense Pulsed Neutron Source (IPNS), Argonne National Laboratory examined the proposals and made recommendations. At LANSCE, neutrons are produced by spallation when a pulsed, 800-MeV proton beam impinges on a tungsten target. The proton pulses are provided by the Clinton P. Anderson Meson Physics Facility (LAMPF) accelerator and anmore » associated Proton Storage Ring (PSR), which can alter the intensity, time structure, and repetition rate of the pulses. The LAMPF protons of Line D are shared between the LANSCE target and the Weapons Neutron Research facility, which results in LANSCE spectrometers being available to external users for unclassified research about 80% of each six-month LAMPF run cycle. Measurements of interest to the Los Alamos National Laboratory may also be performed and may occupy up to an additional 20% of the available beam time. These experiments are reviewed by an internal program advisory committee. One hundred thirty-four proposals were submitted for unclassified research and twelve proposals for research of a programmatic nature to the Laboratory. Our definition of beam availability is when the proton current from the PSR exceeds 50% of the planned value. The PSR ran at 65{mu}A current (average) at 20 Hz for most of 1990. All of the scheduled experiments were performed and experiments in support of the LANSCE research program were accomplished during the discretionary periods.« less

VSI@ESS: Case study for a vibrational spectroscopy instrument at the european spallation source

NASA Astrophysics Data System (ADS)

Zoppi, Marco; Fedrigo, Anna; Celli, Milva; Colognesi, Daniele

2015-01-01

Neutron Vibrational Spectroscopy is a well-established experimental technique where elementary excitations at relatively high frequency are detected via inelastic neutron scattering. This technique attracts a high interest in a large fraction of the scientific community in the fields of chemistry, materials science, physics, and biology, since one of its main applications exploits the large incoherent scattering cross section of the proton with respect to all the other elements, whose dynamics can be spectroscopically detected, even if dissolved in very low concentration in materials composed of much heavier atoms. We have proposed a feasibility study for a Vibrational Spectroscopy Instrument (VSI) at the European Spallation Source ESS. Here, we will summarize the preliminary design calculations and the corresponding McStas simulation results for a possible ToF, Inverted Geometry, VSI beamline.

Determination of the ¹⁴C content in activated steel components from a neutron spallation source and a nuclear power plant.

PubMed

Schumann, Dorothea; Stowasser, Tanja; Volmert, Benjamin; Günther-Leopold, Ines; Linder, Hanspeter; Wieland, Erich

2014-06-03

The (14)C content in activated steel components from the Swiss Nuclear Power Plant (NPP) Gösgen and the Spallation Neutron Source SINQ at the Paul Scherrer Institute is determined using a wet chemistry digestion technique and liquid scintillation counting for (14)C activity measurements. The (14)C activity of an activated fuel assembly steel nut from the NPP is further compared with theoretical predictions made on the basis of a Monte Carlo reactor model for this NPP. Knowledge of the (14)C inventory in these activated steel materials is important in conjunction with future corrosion studies on these materials aimed at identifying the (14)C containing organic compounds possibly formed in the cement-based near field of a repository for radioactive waste.

Experiment Automation with a Robot Arm using the Liquids Reflectometer Instrument at the Spallation Neutron Source

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

Zolnierczuk, Piotr A; Vacaliuc, Bogdan; Sundaram, Madhan

The Liquids Reflectometer instrument installed at the Spallation Neutron Source (SNS) enables observations of chemical kinetics, solid-state reactions and phase-transitions of thin film materials at both solid and liquid surfaces. Effective measurement of these behaviors requires each sample to be calibrated dynamically using the neutron beam and the data acquisition system in a feedback loop. Since the SNS is an intense neutron source, the time needed to perform the measurement can be the same as the alignment process, leading to a labor-intensive operation that is exhausting to users. An update to the instrument control system, completed in March 2013, implementedmore » the key features of automated sample alignment and robot-driven sample management, allowing for unattended operation over extended periods, lasting as long as 20 hours. We present a case study of the effort, detailing the mechanical, electrical and software modifications that were made as well as the lessons learned during the integration, verification and testing process.« less

Moisture-Induced Alumina Scale Spallation: The Hydrogen Factor

NASA Technical Reports Server (NTRS)

Smialek, James L.

2010-01-01

For some time the oxidation community has been concerned with interfacial spallation of protective alumina scales, not just upon immediate cool down, but as a time-delayed phenomenon. Moisture-induced delayed spallation (MIDS) and desktop spallation (DTS) of thermal barrier coatings (TBCs) refer to this process. It is most apparent for relatively adherent alumina scales that have survived initial cool down in a dry environment, have built up considerable thickness and strain energy, and have been somewhat damaged, such as by cyclic oxidation cracking. Indeed, a "sensitive zone" can be described that maximizes the observed effect as a function of all the relevant factors. Moisture has been postulated to serve as a source of interfacial hydrogen embrittlement. Hydrogen is derived from reaction with aluminum in the alloy at an exposed interface. The purpose of this monograph is to trace the close analogy of this phenomenon to other hydrogen-induced effects, such as embrittlement of aluminides and blistering of alloys and anodic alumina films. A formalized, top-down, logic-tree structure is presented as a guide to this discussion. A theoretical basis for interfacial weakening by hydrogen is first cited, as are demonstrations of hydrogen detection as a reaction product or interfacial species. Further support is provided by critical experiments that recreate the moisture effect, but by isolating hydrogen from other potential causative factors. These experiments include tests in H 2-containing atmospheres or cathodic hydrogen charging. Accordingly, they strongly indicate that interfacial hydrogen, derived from moisture, is the key chemical species accounting for delayed alumina scale spallation.

SIMULATION AND MOCKUP OF SNS JET-FLOW TARGET WITH WALL JET FOR CAVITATION DAMAGE MITIGATION

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

Wendel, Mark W; Geoghegan, Patrick J; Felde, David K

2014-01-01

Pressure waves created in liquid mercury pulsed spallation targets at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory induce cavitation damage on the stainless steel target container. The cavitation damage is thought to limit the lifetime of the target for power levels at and above 1 MW. Severe through-wall cavitation damage on an internal wall near the beam entrance window has been observed in spent-targets. Surprisingly though, there is very little damage on the walls that bound an annular mercury channel that wraps around the front and outside of the target. The mercury flow through this channel ismore » characterized by smooth, attached streamlines. One theory to explain this lack of damage is that the uni-directional flow biases the direction of the collapsing cavitation bubble, reducing the impact pressure and subsequent damage. The theory has been reinforced by in-beam separate effects data. For this reason, a second-generation SNS mercury target has been designed with an internal wall jet configuration intended to protect the concave wall where damage has been observed. The wall jet mimics the annular flow channel streamlines, but since the jet is bounded on only one side, the momentum is gradually diffused by the bulk flow interactions as it progresses around the cicular path of the target nose. Numerical simulations of the flow through this jet-flow target have been completed, and a water loop has been assembled with a transparent test target in order to visualize and measure the flow field. This paper presents the wall jet simulation results, as well as early experimental data from the test loop.« less

SPEAR — ToF neutron reflectometer at the Los Alamos Neutron Science Center

NASA Astrophysics Data System (ADS)

Dubey, M.; Jablin, M. S.; Wang, P.; Mocko, M.; Majewski, J.

2011-11-01

This article discusses the Surface ProfilE Analysis Reflectometer (SPEAR), a vertical scattering geometry time-of-flight reflectometer, at the Los Alamos National Laboratory Lujan Neutron Scattering Center. SPEAR occupies flight path 9 and receives spallation neutrons from a polychromatic, pulsed (20Hz) source that pass through a liquid-hydrogen moderator at 20K coupled with a Be filter to shift their energy spectrum. The spallation neutrons are generated by bombarding a tungsten target with 800MeV protons obtained from an accelerator. The process produces an integrated neutron flux of ˜ 3.4×106 cm-2 s-1 at a proton current of 100 μA. SPEAR employs choppers and frame overlap mirrors to obtain a neutron wavelength range of 4.5-16 Å. SPEAR uses a single 200mm long 3He linear position-sensitive detector with ˜ 2 mm FWHM resolution for simultaneous studies of both specular and off-specular scattering. SPEAR's moderated neutrons are collimated into a beam which impinges from above upon a level sample with an average angle of 0.9° to the horizontal, to facilitate air-liquid interface studies. In the vertical direction, the beam converges at the sample position. The neutrons can be further collimated to the desired divergence by finely slitting the beam using a set of two 10B4C slit packages. The instrument is ideally suited to study organic and inorganic thin films with total thicknesses between 5 and 3000 Å in a variety of environments. Specifically designed sample chambers available at the instrument provide the opportunity to study biological systems at the solid-liquid interface. SPEAR's unique experimental capabilities are demonstrated by specific examples in this article. Finally, an outlook for SPEAR and perspectives on future instrumentation are discussed.

Dynamic fracture of tantalum under extreme tensile stress

DOE PAGES

Albertazzi, Bruno; Ozaki, Norimasa; Zhakhovsky, Vasily; ...

2017-06-02

The understanding of fracture phenomena of a material at extremely high strain rates is a key issue for a wide variety of scientific research ranging from applied science and technological developments to fundamental science such as laser-matter interaction and geology. Despite its interest, its study relies on a fine multiscale description, in between the atomic scale and macroscopic processes, so far only achievable by large-scale atomic simulations. Direct ultrafast real-time monitoring of dynamic fracture (spallation) at the atomic lattice scale with picosecond time resolution was beyond the reach of experimental techniques. We show that the coupling between a high-power opticalmore » laser pump pulse and a femtosecond x-ray probe pulse generated by an x-ray free electron laser allows detection of the lattice dynamics in a tantalum foil at an ultrahigh strain rate of Embedded Image ~2 × 10 8 to 3.5 × 10 8 s -1. A maximal density drop of 8 to 10%, associated with the onset of spallation at a spall strength of ~17 GPa, was directly measured using x-ray diffraction. The experimental results of density evolution agree well with large-scale atomistic simulations of shock wave propagation and fracture of the sample. Our experimental technique opens a new pathway to the investigation of ultrahigh strain-rate phenomena in materials at the atomic scale, including high-speed crack dynamics and stress-induced solid-solid phase transitions.« less

Investigation of Spheromak Plasma Cooling through Metallic Liner Spallation during Compression

NASA Astrophysics Data System (ADS)

Ross, Keeton; Mossman, Alex; Young, William; Ivanov, Russ; O'Shea, Peter; Howard, Stephen

2016-10-01

Various magnetic-target fusion (MTF) reactor concepts involve a preliminary magnetic confinement stage, followed by a metallic liner implosion that compresses the plasma to fusion conditions. The process is repeated to produce a pulsed, net-gain energy system. General Fusion, Inc. is pursuing one scheme that involves the compression of spheromak plasmas inside a liner formed by a collapsing vortex of liquid Pb-Li. The compression is driven by focused acoustic waves launched by gas-driven piston impacts. Here we describe a project to exploring the effects of possible liner spallation during compression on the spheromaks temperature, lifetime, and stability. We employ a 1 J, 10 ns pulsed YAG laser at 532nm focused onto a thin film of Li or Al to inject a known quantity of metallic impurities into a spheromak plasma and then measure the response. Diagnostics including visible and ultraviolet spectrometers, ion Doppler, B-probes, and Thomson scattering are used for plasma characterization. We then plan to apply the trends measured under these controlled conditions to evaluate the role of wall impurities during `field shots', where spheromaks are compressed through a chemically driven implosion of an aluminum flux conserver. The hope is that with further study we could more accurately include the effect of wall impurities on the fusion yield of a reactor-scale MTF system. Experimental procedures and results are presented, along with their relation to other liner-driven, MTF schemes. -/a

Simulations towards optimization of a neutron/anti-neutron oscillation experiment at the European Spallation Source

NASA Astrophysics Data System (ADS)

Frost, Matthew; Kamyshkov, Yuri; Castellanos, Luis; Klinkby, Esben; US NNbar Collaboration

2015-04-01

The observation of Neutron/Anti-neutron oscillation would prove the existence of Baryon Number Violation (BNV), and thus an explanation for the dominance of matter over anti-matter in the universe. The latest experiments have shown the oscillation time to be greater than 8.6 x 107 seconds, whereas current theoretical predictions suggest times on the order of 108 to 109 seconds. A neutron oscillation experiment proposed at the European Spallation Source (ESS) would provide sensitivity of more than 1000 times previous experiments performed, thus providing a result well-suited to confirm or deny current theory. A conceptual design of the proposed experiment will be presented, as well as the optimization of key experiment components using Monte-Carlo simulation methods, including the McStas neutron ray-trace simulation package. This work is supported by the Organized Research Units Program funded by The University of Tennessee, Knoxville Office of Research and Engagement.

Low-level rf control of Spallation Neutron Source: System and characterization

NASA Astrophysics Data System (ADS)

Ma, Hengjie; Champion, Mark; Crofford, Mark; Kasemir, Kay-Uwe; Piller, Maurice; Doolittle, Lawrence; Ratti, Alex

2006-03-01

The low-level rf control system currently commissioned throughout the Spallation Neutron Source (SNS) LINAC evolved from three design iterations over 1 yr intensive research and development. Its digital hardware implementation is efficient, and has succeeded in achieving a minimum latency of less than 150 ns which is the key for accomplishing an all-digital feedback control for the full bandwidth. The control bandwidth is analyzed in frequency domain and characterized by testing its transient response. The hardware implementation also includes the provision of a time-shared input channel for a superior phase differential measurement between the cavity field and the reference. A companion cosimulation system for the digital hardware was developed to ensure a reliable long-term supportability. A large effort has also been made in the operation software development for the practical issues such as the process automations, cavity filling, beam loading compensation, and the cavity mechanical resonance suppression.

AC magnetic field measurement using a small flip coil system for rapid cycling AC magnets at the China Spallation Neutron Source (CSNS)

NASA Astrophysics Data System (ADS)

Zhou, Jianxin; Kang, Wen; Li, Shuai; Liu, Yudong; Liu, Yiqin; Xu, Shouyan; Guo, Xiaoling; Wu, Xi; Deng, Changdong; Li, Li; Wu, Yuwen; Wang, Sheng

2018-02-01

The China Spallation Neutron Source (CSNS) has two major accelerator systems, a linear accelerator and a rapid cycling synchrotron (RCS). The RCS accelerator is used to accumulate and accelerate protons from the energy of 80 MeV to the design energy of 1.6 GeV at the repetition rate of 25 Hz, and extract the high energy beam to the target. The main magnets of the RCS accelerator are excited by AC current with DC bias. The magnetic field quality is very important for the RCS accelerator operation, since it should guarantee and focus a circulating beam. In order to characterize the AC magnets, a small flip coil measurement system has been developed and one of each type of AC magnets has been studied. The measurement system and selected measurement results are presented in this paper.

Feasibility and applications of the spin-echo modulation option for a small angle neutron scattering instrument at the European Spallation Source

NASA Astrophysics Data System (ADS)

Kusmin, A.; Bouwman, W. G.; van Well, A. A.; Pappas, C.

2017-06-01

We describe theoretical and practical aspects of spin-echo modulated small-angle neutron scattering (SEMSANS) as well as the potential combination with SANS. Based on the preliminary technical designs of SKADI (a SANS instrument proposed for the European Spallation Source) and a SEMSANS add-on, we assess the practicability, feasibility and scientific merit of a combined SANS and SEMSANS setup by calculating tentative SANS and SEMSANS results for soft matter, geology and advanced material samples that have been previously studied by scattering methods. We conclude that lengths from 1 nm up to 0.01 mm can be observed simultaneously in a single measurement. Thus, the combination of SANS and SEMSANS instrument is suited for the simultaneous observation of a wide range of length scales, e.g. for time-resolved studies of kinetic processes in complex multiscale systems.

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.

Observation of galactic cosmic ray spallation events from the SoHO mission 20-yr operation of LASCO

NASA Astrophysics Data System (ADS)

Koutchmy, S.; Tavabi, E.; Urtado, O.

2018-07-01

A shower of secondary cosmic ray (CR) particles is produced at high altitudes in the Earth's atmosphere, so the primordial galactic cosmic rays (GCRs) are never directly measured outside the Earth magnetosphere and atmosphere. They approach the Earth and other planets in the complex pattern of rigidity's dependence, generally excluded by the magnetosphere. GCRs revealed by images of single nuclear reactions also called spallation events are described here. Such an event was seen on 2015 November 29 using a unique Large Angle and Spectrometric Coronagraphs C3 space coronagraph routine image taken during the Solar and Heliospheric Observatory (SoHO) mission observing uninterruptedly at the Lagrangian L1 point. The spallation signature of a GCR identified well outside the Earth's magnetosphere is obtained for the first time. The resulting image includes different diverging linear `tracks' of varying intensity, leading to a single pixel; this frame identifies the site on the silicon CCD chip of the coronagraph camera. There was no solar flare reported at that time, nor coronal mass ejection and no evidence of optical debris around the spacecraft. More examples of smaller CR events have been discovered through the 20 yr of continuous observations from SoHO. This is the first spallation event from a CR, recorded outside the Earth's magnetosphere. We evaluate the probable energy of these events suggesting a plausible galactic source.

Observation of galactic cosmic ray spallation events from the SoHO mission 20-Year operation of LASCO

NASA Astrophysics Data System (ADS)

Koutchmy, S.; Tavabi, E.; Urtado, O.

2018-05-01

A shower of secondary Cosmic Ray (CR) particles is produced at high altitudes in the Earth's atmosphere, so the primordial Galactic Cosmic Rays (GCRs) are never directly measured outside the Earth magnetosphere and atmosphere. They approach the Earth and other planets in the complex pattern of rigidity's dependence, generally excluded by the magnetosphere. GCRs revealed by images of single nuclear reactions also called spallation events are described here. Such an event was seen on Nov. 29, 2015 using a unique LASCO C3 space coronagraph routine image taken during the Solar and Heliospheric Observatory (SoHO) mission observing uninterruptedly at the Lagrangian L1 point. The spallation signature of a GCR identified well outside the Earth's magnetosphere is obtained for the 1st time. The resulting image includes different diverging linear "tracks" of varying intensity, leading to a single pixel; this frame identifies the site on the silicon CCD chip of the coronagraph camera. There was no solar flare reported at that time, nor Coronal Mass Ejection (CME) and no evidence of optical debris around the spacecraft. More examples of smaller CR events have been discovered through the 20 years of continuous observations from SoHO. This is the first spallation event from a CR, recorded outside the Earth's magnetosphere. We evaluate the probable energy of these events suggesting a plausible galactic source.

Moisture-Induced Alumina Scale Spallation: The Hydrogen Factor

NASA Technical Reports Server (NTRS)

Smialek, James L.

2009-01-01

For some time our community has been concerned with interfacial spallation of protective alumina scales, not just upon immediate cooldown, but as a time-delayed phenomenon. Moisture-induced delayed spallation (MIDS) and desktop spallation (DTS) of TBC's refer to this process. It is most apparent for relatively adherent alumina scales that have survived cool down in a dry environment, built up considerable thickness and strain energy, and have been somewhat damaged, such as by cyclic oxidation cracking. Indeed, a "sweet zone" can be defined that maximizes the observed effect as a function of all the relevant factors. Moisture has been postulated to serve as a source of interfacial hydrogen embrittlement derived from reaction with aluminum in the alloy at an exposed interface. The purpose of this monograph is to trace the close analogy of this phenomenon to other hydrogen effects, such as embrittlement of aluminides and blistering of alloys and anodic alumina films. A formalized, top-down, logic tree structure is presented as a guide to this discussion. A theoretical basis for interfacial weakening by hydrogen is first cited, as are demonstrations of hydrogen as a reaction product or detected interfacial species. Further support is provided by critical experiments that produce the same moisture effect, but by isolating hydrogen from other potential causative factors. These experiments include tests in H2-containing atmospheres or cathodic hydrogen charging.

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

Cosentino, L.; Pappalardo, A.; Piscopo, M.

During 2014, the second experimental area (EAR2) was completed at the n-TOF neutron beam facility at CERN (n-TOF indicates neutron beam measurements by means of time of flight technique). The neutrons are produced via spallation, by means of a high-intensity 20 GeV pulsed proton beam impinging on a thick target. The resulting neutron beam covers the energy range from thermal to several GeV. In this paper, we describe two beam diagnostic devices, both exploiting silicon detectors coupled with neutron converter foils containing {sup 6}Li. The first one is based on four silicon pads and allows monitoring of the neutron beammore » flux as a function of the neutron energy. The second one, in beam and based on position sensitive silicon detectors, is intended for the reconstruction of the beam profile, again as a function of the neutron energy. Several electronic setups have been explored in order to overcome the issues related to the gamma flash, namely, a huge pulse present at the start of each neutron bunch which may blind the detectors for some time. The two devices were characterized with radioactive sources and also tested at the n-TOF facility at CERN. The wide energy and intensity range they proved capable of sustaining made them attractive and suitable to be used in both EAR1 and EAR2 n-TOF experimental areas, where they became immediately operational.« less

Detecting cavitation in mercury exposed to a high-energy pulsed proton beam

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

Manzi, Nicholas J; Chitnis, Parag V; Holt, Ray G

2010-01-01

The Oak Ridge National Laboratory Spallation Neutron Source employs a high-energy pulsed proton beam incident on a mercury target to generate short bursts of neutrons. Absorption of the proton beam produces rapid heating of the mercury, resulting in the formation of acoustic shock waves and the nucleation of cavitation bubbles. The subsequent collapse of these cavitation bubbles promote erosion of the steel target walls. Preliminary measurements using two passive cavitation detectors (megahertz-frequency focused and unfocused piezoelectric transducers) installed in a mercury test target to monitor cavitation generated by proton beams with charges ranging from 0.041 to 4.1 C will bemore » reported on. Cavitation was initially detected for a beam charge of 0.082 C by the presence of an acoustic emission approximately 250 s after arrival of the incident proton beam. This emission was consistent with an inertial cavitation collapse of a bubble with an estimated maximum bubble radius of 0.19 mm, based on collapse time. The peak pressure in the mercury for the initiation of cavitation was predicted to be 0.6 MPa. For a beam charge of 0.41 C and higher, the lifetimes of the bubbles exceeded the reverberation time of the chamber (~300 s), and distinct windows of cavitation activity were detected, a phenomenon that likely resulted from the interaction of the reverberation in the chamber and the cavitation bubbles.« less

General-purpose readout electronics for white neutron source at China Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Wang, Q.; Cao, P.; Qi, X.; Yu, T.; Ji, X.; Xie, L.; An, Q.

2018-01-01

The under-construction White Neutron Source (WNS) at China Spallation Neutron Source is a facility for accurate measurements of neutron-induced cross section. Seven spectrometers are planned at WNS. As the physical objectives of each spectrometer are different, the requirements for readout electronics are not the same. In order to simplify the development of the readout electronics, this paper presents a general method for detector signal readout. This method has advantages of expansibility and flexibility, which makes it adaptable to most detectors at WNS. In the WNS general-purpose readout electronics, signals from any kinds of detectors are conditioned by a dedicated signal conditioning module corresponding to this detector, and then digitized by a common waveform digitizer with high speed and high precision (1 GSPS at 12-bit) to obtain the full waveform data. The waveform digitizer uses a field programmable gate array chip to process the data stream and trigger information in real time. PXI Express platform is used to support the functionalities of data readout, clock distribution, and trigger information exchange between digitizers and trigger modules. Test results show that the performance of the WNS general-purpose readout electronics can meet the requirements of the WNS spectrometers.

Development of a Lead Slowing Down Spectrometer for fission cross section measurements at LANSCE

NASA Astrophysics Data System (ADS)

Rochman, Dimitri; Haight, Robert C.; Wender, Stephen A.; O'Donnell, John M.; Michaudon, Andre; Vieira, Dave J.; Rundberg, Robert S.; Kronenberg, Andreas; Bond, Evelyn; Wilhelmy, Jerry B.; Bredeweg, Todd; Ethvignot, Thierry; Granier, Thierry; Petit, Michael; Danon, Yaron

2004-05-01

The Lead Slowing Down Spectrometer (LSDS) recently installed at the Los Alamos Neutron Science Center (LANSCE) consists of a 1.2 meter cube of lead surrounding a tungsten target, which is bombarded by pulses of 800 MeV protons from the Proton Storage Ring (PSR). Neutrons are produced by spallation from the interaction of the proton pulse with the target. The aim of the LSDS is to keep the neutrons inside the lead volume for few hundreds of microseconds and to slow them down by small steps in energy before they leave the spectrometer. The advantage of the LSDS is the large amount of neutrons available in the lead volume compared to traditional time-of-flight experiments. Driving the LSDS with a pulsed proton beam increases the neutron flux per watt of beam power significantly over similar spectrometers driven by electron linear accelerators. The first measurements to characterize the properties of the LSDS are presented.

Spallation Neutron Source Second Target Station Integrated Systems Update

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

Ankner, John Francis; An, Ke; Blokland, Willem

The Spallation Neutron Source (SNS) was designed from the beginning to accommodate both an accelerator upgrade to increase the proton power and a second target station (STS). Four workshops were organized in 2013 and 2014 to identify key science areas and challenges where neutrons will play a vital role [1-4]. Participants concluded that the addition of STS to the existing ORNL neutron sources was needed to complement the strengths of High Flux Isotope Reactor (HFIR) and the SNS first target station (FTS). To address the capability gaps identified in the workshops, a study was undertaken to identify instrument concepts thatmore » could provide the required new science capabilities. The study outlined 22 instrument concepts and presented an initial science case for STS [5]. These instrument concepts formed the basis of a planning suite of instruments whose requirements determined an initial site layout and moderator selection. An STS Technical Design Report (TDR) documented the STS concept based on those choices [6]. Since issue of the TDR, the STS concept has significantly matured as described in this document.« less

Molecular dynamics studies of thermal dissipation during shock induced spalling

NASA Astrophysics Data System (ADS)

Xiang, Meizhen; Hu, Haibo; Chen, Jun; Liao, Yi

2013-09-01

Under shock loadings, the temperature of materials may vary dramatically during deformation and fracture processes. Thus, thermal effect is important for constructing dynamical failure models. Existing works on thermal dissipation effects are mostly from meso- to macro-scale levels based on phenomenological assumptions. The main purpose of the present work is to provide several atomistic scale perspectives about thermal dissipation during spall fracture by nonequilibrium molecular dynamics simulations on single-crystalline and nanocrystalline Pb. The simulations show that temperature arising starts from the vicinity of voids during spalling. The thermal dissipation rate in void nucleation stage is much higher than that in the later growth and coalescence stages. Both classical spallation and micro-spallation are taken into account. Classical spallation is corresponding to spallation phenomenon where materials keep in solid state during shock compression and release stages, while micro-spallation is corresponding to spallation phenomenon where melting occurs during shock compression and release stages. In classical spallation, whether residuary dislocations are produced in pre-spall stages has significant influences on thermal dissipation rate during void growth and coalescence. The thermal dissipation rates decrease as shock intensity increases. When the shock intensity exceeds the threshold of micro-spallation, the thermal dissipation rate in void nucleation stage drops precipitously. It is found that grain boundaries mainly influence the thermal dissipation rate in void nucleation stage in classical spallation. In micro-spallation, the grain boundary effects are insignificant.

Spallation behaviour of a Zr-bulk metallic glass

NASA Astrophysics Data System (ADS)

Ling, Z.; Huang, X.; Shen, L. T.; Dai, L. H.

2012-08-01

Plate impact experiments have been conducted on a Zr-based bulk metal glass (BMG) using a single stage light gas gun. To understand the spallation process of the material, samples were subjected to dynamic tensile loadings of the same amplitude but different durations. Fractographs of spallation surface and fracture features were characterized and the fracture mechanism of different regions of the spallation surface was discussed. Morphology of the spallation surface in the Zr-BMG exhibited a typical equiaxial cellular pattern and porous microstructure. These experiments revealed that, subjected to hydro-tensile stresses, the microdamage of the spallation occurred in the Zr-BMG is microvoids; the spallation in the Zr-BMG is resulted from nucleation, growth and coalescence of microvoids; and the time needed for these microvoids nucleation is less than 100 ns with a stress amplitude of 3.18 GPa.

Shock Wave Technology and Application: An Update☆

PubMed Central

Rassweiler, Jens J.; Knoll, Thomas; Köhrmann, Kai-Uwe; McAteer, James A.; Lingeman, James E.; Cleveland, Robin O.; Bailey, Michael R.; Chaussy, Christian

2012-01-01

Context The introduction of new lithotripters has increased problems associated with shock wave application. Recent studies concerning mechanisms of stone disintegration, shock wave focusing, coupling, and application have appeared that may address some of these problems. Objective To present a consensus with respect to the physics and techniques used by urologists, physicists, and representatives of European lithotripter companies. Evidence acquisition We reviewed recent literature (PubMed, Embase, Medline) that focused on the physics of shock waves, theories of stone disintegration, and studies on optimising shock wave application. In addition, we used relevant information from a consensus meeting of the German Society of Shock Wave Lithotripsy. Evidence synthesis Besides established mechanisms describing initial fragmentation (tear and shear forces, spallation, cavitation, quasi-static squeezing), the model of dynamic squeezing offers new insight in stone comminution. Manufacturers have modified sources to either enlarge the focal zone or offer different focal sizes. The efficacy of extracorporeal shock wave lithotripsy (ESWL) can be increased by lowering the pulse rate to 60–80 shock waves/min and by ramping the shock wave energy. With the water cushion, the quality of coupling has become a critical factor that depends on the amount, viscosity, and temperature of the gel. Fluoroscopy time can be reduced by automated localisation or the use of optical and acoustic tracking systems. There is a trend towards larger focal zones and lower shock wave pressures. Conclusions New theories for stone disintegration favour the use of shock wave sources with larger focal zones. Use of slower pulse rates, ramping strategies, and adequate coupling of the shock wave head can significantly increase the efficacy and safety of ESWL. PMID:21354696

Cavitation instability in bulk metallic glasses

NASA Astrophysics Data System (ADS)

Dai, L. H.; Huang, X.; Ling, Z.

2015-09-01

Recent experiments have shown that fracture surfaces of bulk metallic glasses (BMGs) usually exhibit an intriguing nanoscale corrugation like fractographic feature mediated by nanoscale void formation. We attribute the onset of this nanoscale corrugation to TTZs (tension transformation zones) mediated cavitation. In our recent study, the spall experiments of Zr-based BMG using a single-stage light gas gun were performed. To uncover the mechanisms of the spallation damage nucleation and evolution, the samples were designed to be subjected to dynamic tensile loadings of identical amplitude but with different durations by making use of the multi-stress pulse and the double-flyer techniques. It is clearly revealed that the macroscopic spall fracture in BMGs originates from the nucleation, growth and coalescence of micro-voids. Then, a microvoid nucleation model of BMGs based on free volume theory is proposed, which indicates that the nucleation of microvoids at the early stage of spallation in BMGs is resulted from diffusion and coalescence of free volume. Furthermore, a theoretical model of void growth in BMGs undergoing remote dynamic hydrostatic tension is developed. The critical condition of cavitation instability is obtained. It is found that dynamic void growth in BMGs can be well controlled by a dimensionless inertial number characterizing the competition between intrinsic and extrinsic time scales. To unveil the atomic-level mechanism of cavitation, a systematic molecular dynamics (MD) simulation of spallation behaviour of a binary metallic glass with different impact velocities was performed. It is found that micro-void nucleation is determined TTZs while the growth is controlled by shear transformation zones (STZs) at atomic scale.

Partial Cross Sections of Neutron-Induced Reactions on nCu at En = 6, 8, 10, 12, 14, and 16 MeV for 0νββ Background Studies

NASA Astrophysics Data System (ADS)

Gooden, M. E.; Fallin, B. A.; Finch, S. W.; Kelley, J. H.; Howell, C. R.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Stanislav, V.

2014-05-01

Partial cross-section measurements of (n,n'γ) reactions on natCu were carried out at TUNL using monoenergetic neutrons at six energies of En = 6, 8, 10, 12, 14, 16 MeV. These studies were performed to provide accurate cross-section data on materials abundant in experimental setups involving HPGe detectors used to search for rare events, like the neutrino-less double-beta decay of 76Ge. Spallation and (α,n) neutrons are expected to cause the largest source of external background in the energy region of interest. At TUNL pulsed neutron beams were produced via the 2H(d,n)3He reaction and the deexcitation γ rays from the reaction natCu(n,xγ) were detected with clover HPGe detectors. Cross-section results for the strongest transtions in 63Cu and 65Cu will be reported, and will compared to model calculations and to data recently obtained at LANL with a white neutron beam.

Neutron optics concept for the materials engineering diffractometer at the ESS

NASA Astrophysics Data System (ADS)

Šaroun, J.; Fenske, J.; Rouijaa, M.; Beran, P.; Navrátil, J.; Lukáš, P.; Schreyer, A.; Strobl, M.

2016-09-01

The Beamline for European Materials Engineering Research (BEER) has been recently proposed to be built at the European Spallation Source (ESS). The presented concept of neutron delivery optics for this instrument addresses the problems of bi-spectral beam extraction from a small moderator, optimization of neutron guides profile for long-range neutron transport and focusing at the sample under various constraints. They include free space before and after the guides, a narrow guide section with gaps for choppers, closing of direct line of sight and cost reduction by optimization of the guides cross-section and coating. A system of slits and exchangeable focusing optics is proposed in order to match various wavelength resolution options provided by the pulse shaping and modulation choppers, which permits to efficiently trade resolution for intensity in a wide range. Simulated performance characteristics such as brilliance transfer ratio are complemented by the analysis of the histories of “useful” neutrons obtained by back tracing neutrons hitting the sample, which helps to optimize some of the neutron guide parameters such as supermirror coating.

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.

Neutron Scattering Facilities

Science.gov Websites

Low Energy Neutron Source (LENS), Indiana University Cyclotron Facility, USA McMaster Nuclear Reactor Research, Gaithersburg, Maryland, USA Peruvian Institute of Nuclear Energy (IPEN), Lima, Peru Spallation Nuclear Science and Technology Organisation, Lucas Heights, Australia High-flux Advanced Neutron

Spin exchange optical pumping based polarized 3He filling station for the Hybrid Spectrometer at the Spallation Neutron Source.

PubMed

Jiang, C Y; Tong, X; Brown, D R; Culbertson, H; Graves-Brook, M K; Hagen, M E; Kadron, B; Lee, W T; Robertson, J L; Winn, B

2013-06-01

The Hybrid Spectrometer (HYSPEC) is a new direct geometry spectrometer at the Spallation Neutron Source at the Oak Ridge National Laboratory. This instrument is equipped with polarization analysis capability with 60° horizontal and 15° vertical detector coverages. In order to provide wide angle polarization analysis for this instrument, we have designed and built a novel polarized (3)He filling station based on the spin exchange optical pumping method. It is designed to supply polarized (3)He gas to HYSPEC as a neutron polarization analyzer. In addition, the station can optimize the (3)He pressure with respect to the scattered neutron energies. The depolarized (3)He gas in the analyzer can be transferred back to the station to be repolarized. We have constructed the prototype filling station. Preliminary tests have been carried out demonstrating the feasibility of the filling station. Here, we report on the design, construction, and the preliminary results of the prototype filling station.

Testing Single Phase IGBT H-Bridge Switch Plates for the High Voltage Converter Modulator at the Spallation Neutron Source

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

Peplov, Vladimir V; Anderson, David E; Solley, Dennis J

2014-01-01

Three IGBT H-bridge switching networks are used in each High Voltage Converter Modulator (HVCM) system at the Spallation Neutron Source (SNS) to generate drive currents to three boost transformer primaries switching between positive and negative bus voltages at 20 kHz. Every switch plate assembly is tested before installing it into an operational HVCM. A Single Phase Test Stand has been built for this purpose, and it is used for adjustment, measurement and testing of different configurations of switch plates. This paper will present a description of the Test Stand configuration and discuss the results of testing switch plates with twomore » different types of IGBT gate drivers currently in use on the HVCM systems. Comparison of timing characteristics of the original and new drivers and the resulting performance reinforces the necessity to replace the original H-bridge network drivers with the upgraded units.« less

Thrust noise minimization in long-term laser ablation of propellant material in the nanosecond and picosecond regime

NASA Astrophysics Data System (ADS)

Lorbeer, Raoul-Amadeus; Scharring, Stefan; Karg, Stephanie; Pastow, Jan; Pastuschka, Lisa; Förster, Daniel Johannes; Eckel, Hans-Albert

2017-01-01

The avoidance of any moving parts in a microthruster exhibits a great potential for low-noise thrust generation in the micronewton range. This is required, e.g., for scientific missions that need attitude and orbit control systems with exquisite precision. Laser ablation propulsion offers the opportunity of permanent inertia-free, electro-optical delivery of laser energy to access the propellant entirely without moving it. New propellant is accessed by ablating the previous surface in layers, essentially damaging the surface with a laser over and over again. The resulting surface properties for different fluences and scanning patterns were investigated for multiple layers of aluminum, copper, and gold. The pulse-length-specific issues of various ablation mechanisms such as vaporization, spallation, and phase explosion are accounted for by the use of a 10-ps laser system and a 500-ps laser system. We show that the surface roughness produced with 500-ps laser pulses is approximately twice the surface roughness generated by using 10-ps laser pulses. Furthermore, with 500-ps pulses, the surface roughness shows low dependency on the fluence for carefully chosen scanning parameters. Therefore, we conclude that laser pulse duration differences in the picosecond and nanosecond regimes will not necessarily alter surface roughness properties.

Design and implementation of a multiaxial loading capability during heating on an engineering neutron diffractometer

DOE PAGES

Benafan, O.; Padula, S. A.; Skorpenske, H. D.; ...

2014-10-02

Here we discuss a gripping capability that was designed, implemented, and tested for in situ neutron diffraction measurements during multiaxial loading and heating on the VULCAN engineering materials diffractometer at the spallation neutron source at Oak Ridge National Laboratory.

RADIATION-RESISTANT FIBER OPTIC STRAIN SENSORS FOR SNS TARGET INSTRUMENTATION

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

Blokland, Willem; Bryan, Jeff; Riemer, Bernie

2016-01-01

Measurement of stresses and strains in the mercury tar-get vessel of the Spallation Neutron Source (SNS) is important to understand the structural dynamics of the target. This work reports the development of radiation-resistant fiber optic strain sensors for the SNS target in-strumentation.

Astrophysical Li-7 as a product of big bang nucleosynthesis and galactic cosmic-ray spallation

NASA Technical Reports Server (NTRS)

Olive, Keith A.; Schramm, David N.

1992-01-01

The astrophysical Li-7 abundance is considered to be largely primordial, while the Be and B abundances are thought to be due to galactic cosmic ray (GCR) spallation reactions on top of a much smaller big bang component. But GCR spallation should also produce Li-7. As a consistency check on the combination of big bang nucleosynthesis and GCR spallation, the Be and B data from a sample of hot population II stars is used to subtract from the measured Li-7 abundance an estimate of the amount generated by GCR spallation for each star in the sample, and then to add to this baseline an estimate of the metallicity-dependent augmentation of Li-7 due to spallation. The singly reduced primordial Li-7 abundance is still consistent with big bang nucleosynthesis, and a single GCR spallation model can fit the Be, B, and corrected Li-7 abundances for all the stars in the sample.

Source amplitudes of NTS explosions inferred from Rayleigh waves at Albuquerque and Tucson. Topical report

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

Bache, T.C.; Rodi, W.L.; Mason, B.F.

1978-06-01

Comparing observed and synthetic seismograms, source amplitudes of NTS explosions are inferred from Rayleigh wave recordings from the WWSSN stations at Albuquerque, New Mexico (ALQ) and Tucson, Arizona (TUC). The potential influence of source complexities, particularly surface spallation and related phenomena, is studied in detail. As described in earlier work by Bache, Rodi and Harkrider, the earth model for the synthetic were converted from observations at ALQ and TUC. The agreement of observed and synthetic seismograms is quite good and is sensitive to important features of the source.

Assessment of In Situ Time Resolved Shock Experiments at Synchrotron Light Sources*

NASA Astrophysics Data System (ADS)

Belak, J.; Ilavsky, J.; Hessler, J. P.

2005-07-01

Prior to fielding in situ time resolved experiments of shock wave loading at the Advanced Photon Source, we have performed feasibility experiments assessing a single photon bunch. Using single and poly-crystal Al, Ti, V and Cu shock to incipient spallation on the gas gun, samples were prepared from slices normal to the spall plane of thickness 100-500 microns. In addition, single crystal Al of thickness 500 microns was shocked to incipient spallation and soft recovered using the LLNL e-gun mini-flyer system. The e-gun mini-flyer impacts the sample target producing a 10's ns flat-top shock transient. Here, we present results for imaging, small-angle scattering (SAS), and diffraction. In particular, there is little SAS away from the spall plane and significant SAS at the spall plane, demonstrating the presence of sub-micron voids. * Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. W-31-109-Eng-38 and work performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.

Spallation Neutron Source Materials Studies

NASA Astrophysics Data System (ADS)

Sommer, W. F.

1998-04-01

Operation of accelerator facilities such as Los Alamos Neutron Science Center (LANSCE), ISIS at Rutherford Appleton Laboratory, the Swiss Institute Neutron Source (SINQ) at Paul Scherrer Institute, and others has provided valuable information on materials performance in high energy particle beams and high energy neutron environments. The Accelerator Production of Tritium (APT) project is sponsoring an extensive series of tests on the effect of spallation neutron source environments to physical and mechanical properties of candidate materials such as nickel-based alloys, stainless steel alloys, aluminum alloys and solid target materials such as tungsten. Measurements of corrosion rates of these candidate materials during irradiation and while in contact with flowing coolant water are being made. The APT tests use the irradiation facility in the beam stop area of the LANSCE accelerator using 800 MeV protons as well as the neutron flux-spectrum generated as these protons interact with targets. The initial irradiations were completed in summer 1997, exposing materials to a fluence approaching 4-6 x 10^21 protons/cm^2. Sample retrieval is now underway. Mechanical properties measurements are being conducted at several laboratories. Studies on components used in service have also been initiated.

Antideuterons in cosmic rays: sources and discovery potential

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

Herms, Johannes; Ibarra, Alejandro; Vittino, Andrea

Antibaryons are produced in our Galaxy in collisions of high energy cosmic rays with the interstellar medium and in old supernova remnants, and possibly, in exotic sources such as primordial black hole evaporation or dark matter annihilations and decays. The search for signals from exotic sources in antiproton data is hampered by large backgrounds from spallation which, within theoretical errors, can solely account for the current data. Due to the higher energy threshold for antideuteron production, which translates into a suppression of the low energy flux from spallations, antideuteron searches have been proposed as a probe for exotic sources. Wemore » perform in this paper a comprehensive analysis of the antideuteron fluxes at the Earth expected from known and hypothetical sources in our Galaxy, and we calculate their maximal values consistent with current antiproton data from AMS-02. We find that supernova remnants generate a negligible flux, whereas primordial black hole evaporation and dark matter annihilations or decays may dominate the total flux at low energies. On the other hand, we find that the (detection of cosmic antideuterons) would require, for the scenarios studied in this paper and assuming optimistic values of the coalescence momentum and solar modulation, an increase of the experimental sensitivity compared to ongoing and planned instruments by at least a factor of 2. Finally, we briefly comment on the prospects for antihelium-3 detection.« less

MW Spallation Neutron Sources for Fusion Materials Testing

ScienceCinema

Dr. Donald Rej

2018-04-18

Dr. Donald Rej of Los Alamos National Laboratory presents an overview of issues, needs, and performance gaps related to materials testing and how they are being addressed at their facility. Current projects such as the Los Alamos Neutron Science Center (LANSCE) and Matter-Radiation Interactions in Extremes (MaRIE) are also discussed.

America COMPETES Act and the FY2010 Budget

DTIC Science & Technology

2009-06-15

Outstanding Junior Investigator, Nuclear Physics Outstanding Junior Investigator, Fusion Energy Sciences Plasma Physics Junior Faculty Development...Spallation Neutron Source Instrumentation Fellowships, and the Fusion Energy Sciences Graduate Fellowships.2 If members of Congress agree with this...Nuclear Physics Outstanding Junior Investigator, Fusion Energy Sciences Plasma Physics Junior Faculty Development; Advanced Scientific Computing

HEKATE-A novel grazing incidence neutron scattering concept for the European Spallation Source.

PubMed

Glavic, Artur; Stahn, Jochen

2018-03-01

Structure and magnetism at surfaces and buried interfaces on the nanoscale can only be accessed by few techniques, one of which is grazing incidence neutron scattering. While the technique has its strongest limitation in a low signal and large background, due to the low scattering probability and need for high resolution, it can be expected that the high intensity of the European Spallation Source in Lund, Sweden, will make many more such studies possible, warranting a dedicated beamline for this technique. We present an instrument concept, Highly Extended K range And Tunable Experiment (HEKATE), for surface scattering that combines the advantages of two Selene neutron guides with unique capabilities of spatially separated distinct wavelength frames. With this combination, it is not only possible to measure large specular reflectometry ranges, even on free liquid surfaces, but also to use two independent incident beams with tunable sizes and resolutions that can be optimized for the specifics of the investigated samples. Further the instrument guide geometry is tuned for reduction of high energy particle background and only uses low to moderate supermirror coatings for high reliability and affordable cost.

HEKATE—A novel grazing incidence neutron scattering concept for the European Spallation Source

NASA Astrophysics Data System (ADS)

Glavic, Artur; Stahn, Jochen

2018-03-01

Structure and magnetism at surfaces and buried interfaces on the nanoscale can only be accessed by few techniques, one of which is grazing incidence neutron scattering. While the technique has its strongest limitation in a low signal and large background, due to the low scattering probability and need for high resolution, it can be expected that the high intensity of the European Spallation Source in Lund, Sweden, will make many more such studies possible, warranting a dedicated beamline for this technique. We present an instrument concept, Highly Extended K range And Tunable Experiment (HEKATE), for surface scattering that combines the advantages of two Selene neutron guides with unique capabilities of spatially separated distinct wavelength frames. With this combination, it is not only possible to measure large specular reflectometry ranges, even on free liquid surfaces, but also to use two independent incident beams with tunable sizes and resolutions that can be optimized for the specifics of the investigated samples. Further the instrument guide geometry is tuned for reduction of high energy particle background and only uses low to moderate supermirror coatings for high reliability and affordable cost.

Stripper foil failure modes and cures at the Spallation Neutron Source

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

Cousineau, Sarah M; Galambos, John D; Kim, Sang-Ho

2011-01-01

The Spallation Neutron Source comprises a 1 GeV, 1.4 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the $H^0$ excited states created during the $H^-$ charge exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming $H^-$ beam, which circled around to strike the foilmore » bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and strike the foil and bracket. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we detail these and other interesting failure mechanisms and describe the improvements we have made to mitigate them.« less

Stripper foil failure modes and cures at the Oak Rdige Spallation Neutron Source

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

Plum, M.A.; Raparia, D.; Cousineau, S.M.

2011-03-28

The Oak Ridge Spallation Neutron Source comprises a 1 GeV, 1.5 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the H{sup 0} excited states created during the H{sup -} charge-exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming H{sup -} beam, which circled aroundmore » to strike the foil bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and strike the foil and bracket. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we detail these and other interesting failure mechanisms and describe the improvements we have made to mitigate them.« less

HPC simulations of grain-scale spallation to improve thermal spallation drilling

NASA Astrophysics Data System (ADS)

Walsh, S. D.; Lomov, I.; Wideman, T. W.; Potter, J.

2012-12-01

Thermal spallation drilling and related hard-rock hole opening techniques are transformative technologies with the potential to dramatically reduce the costs associated with EGS well drilling and improve the productivity of new and existing wells. In contrast to conventional drilling methods that employ mechanical means to penetrate rock, thermal spallation methods fragment rock into small pieces ("spalls") without contact via the rapid transmission of heat to the rock surface. State-of-the-art constitutive models of thermal spallation employ Weibull statistical failure theory to represent the relationship between rock heterogeneity and its propensity to produce spalls when heat is applied to the rock surface. These models have been successfully used to predict such factors as penetration rate, spall-size distribution and borehole radius from drilling jet velocity and applied heat flux. A properly calibrated Weibull model would permit design optimization of thermal spallation drilling under geothermal field conditions. However, although useful for predicting system response in a given context, Weibull models are by their nature empirically derived. In the past, the parameters used in these models were carefully determined from laboratory tests, and thus model applicability was limited by experimental scope. This becomes problematic, for example, if simulating spall production at depths relevant for geothermal energy production, or modeling thermal spallation drilling in new rock types. Nevertheless, with sufficient computational resources, Weibull models could be validated in the absence of experimental data by explicit small-scale simulations that fully resolve rock grains. This presentation will discuss how high-fidelity simulations can be used to inform Weibull models of thermal spallation, and what these simulations reveal about the processes driving spallation at the grain-scale - in particular, the role that inter-grain boundaries and micro-pores play in the onset and extent of spallation. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Performance of the New Los Alamos UCN Source and Implications for Future Experiments

NASA Astrophysics Data System (ADS)

Makela, Mark; LANL UCN Team

2017-01-01

The Los Alamos Ultracold Neutron (UCN) source was replaced during this past summer and has been commissioned during the last few months. The new source is the result of lessons learned during the 10 year operation of the first UCN source and extensive Monte Carlo analysis. The new source is a spallation driven source based on a solid deuterium UCN moderator similar the previous one. This talk will present an overview of the new source design and the results of commissioning tests. The talk will conclude with a brief overview of the implications of source performance on the neutron lifetime and LANL nEDM experiments. This work was funded by LANL LDRD.

New Result for the β-decay Asymmetry Parameter A0 from the UCNA Experiment

NASA Astrophysics Data System (ADS)

Brown, M. A.-P.; UCNA Collaboration

2017-09-01

The UCNA Experiment at the Ultracold Neutron facility at LANL uses polarized ultracold neutrons (UCN) to determine the neutron β-decay asymmetry parameter A0, the angular correlation between the neutron spin and the decay electron's momentum. A0 further determines λ =gA /gV , which, when combined with the neutron lifetime, permits extraction of the CKM matrix element Vud solely from neutron decay. In the UCNA experiment, UCN are produced in a pulsed, spallation driven solid deuterium source, polarized using a 7 T magnetic field, and transported through an Adiabatic Fast Passage (AFP) spin flipper prior to storage within a 1 T solenoidal spectrometer housing electron detectors at each end. The spin-flipper allows one to form a super-ratio of decay rates for neutron spins aligned parallel and anti-parallel to the 1 T magnetic field, eliminating to first order errors due to variations in the decay rate and detector efficiencies. Leading systematics and analysis techniques from the most recent analysis of data collected from 2011-2013 will be presented. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Award Number DE-SC-0014622.

Operational characteristics of the J-PARC cryogenic hydrogen system for a spallation neutron source

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

Tatsumoto, Hideki; Ohtsu, Kiichi; Aso, Tomokazu

2014-01-29

The J-PARC cryogenic hydrogen system provides supercritical hydrogen with the para-hydrogen concentration of more than 99 % and the temperature of less than 20 K to three moderators so as to provide cold pulsed neutron beams of a higher neutronic performance. Furthermore, the temperature fluctuation of the feed hydrogen stream is required to be within ± 0.25 K. A stable 300-kW proton beam operation has been carried out since November 2012. The para-hydrogen concentrations were measured during the cool-down process. It is confirmed that para-hydrogen always exists in the equilibrium concentration because of the installation of an ortho-para hydrogen convertor.more » Propagation characteristics of temperature fluctuation were measured by temporarily changing the heater power under off-beam condition to clarify the effects of a heater control for thermal compensation on the feed temperature fluctuation. The experimental data gave an allowable temperature fluctuation of ± 1.05 K. It is clarified through a 286-kW and a 524-kW proton beam operations that the heater control would be applicable for the 1-MW proton beam operation by extrapolating from the experimental data.« less

3D Multispecies Nonlinear Perturbative Particle Simulation of Intense Nonneutral Particle Beams (Research supported by the Department of Energy and the Short Pulse Spallation Source Project and LANSCE Division of LANL.)

NASA Astrophysics Data System (ADS)

Qin, Hong; Davidson, Ronald C.; Lee, W. Wei-Li

1999-11-01

The Beam Equilibrium Stability and Transport (BEST) code, a 3D multispecies nonlinear perturbative particle simulation code, has been developed to study collective effects in intense charged particle beams described self-consistently by the Vlasov-Maxwell equations. A Darwin model is adopted for transverse electromagnetic effects. As a 3D multispecies perturbative particle simulation code, it provides several unique capabilities. Since the simulation particles are used to simulate only the perturbed distribution function and self-fields, the simulation noise is reduced significantly. The perturbative approach also enables the code to investigate different physics effects separately, as well as simultaneously. The code can be easily switched between linear and nonlinear operation, and used to study both linear stability properties and nonlinear beam dynamics. These features, combined with 3D and multispecies capabilities, provides an effective tool to investigate the electron-ion two-stream instability, periodically focused solutions in alternating focusing fields, and many other important problems in nonlinear beam dynamics and accelerator physics. Applications to the two-stream instability are presented.

Determination of spallation neutron flux through spectral adjustment techniques

DOE PAGES

Mosby, Michelle A.; Engle, Jonathan Ward; Jackman, Kevin Richard; ...

2016-05-30

The Los Alamos Isotope Production Facility (IPF) creates medical isotopes using a proton beam impinged on a target stack. Spallation neutrons are created in the interaction of the beam with target. The use of these spallation neutrons to produce additional radionuclides has been proposed in this paper. However, the energy distribution and magnitude of the flux is not well understood. Finally, a modified SAND-II spectral adjustment routine has been used with radioactivation foils to determine the differential neutron fluence for these spallation neutrons during a standard IPF production run.

Corrigendum to "Fundamental neutron physics beamline at the spallation neutron source at ORNL" [Nucl. Instrum. Methods Phys. Res. A 773 (2015) 45-51

NASA Astrophysics Data System (ADS)

Fomin, N.; Greene, G. L.; Allen, R. R.; Cianciolo, V.; Crawford, C.; Ito, T. M.; Huffman, P. R.; Iverson, E. B.; Mahurin, R.; Snow, W. M.

2015-07-01

The authors regret that there was an error in the author list of the original publication. The name of author Dr. Ito was misspelled. The correct author list is as above. The authors would like to apologise for any inconvenience caused.

Spallation of Cu by 500- and 1570-MeV. pi. /sup -/

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

Haustein, P.E.; Ruth, T.J.

1978-11-01

Relative yields of 36 products extending from /sup 7/Be to /sup 65/Zn have been measured for the interaction of 500- and 1570-MeV negative pions with Cu. These results are compared with calculations from the ISOBAR model, with earlier studies of Cu spallation with lower (resonance) energy pions, energetic protons, and heavy ions. Relative yield patterns at both ..pi../sup -/ energies show only slight differences when compared to spallation by protons of comparable energy. Calculations from the ISOBAR model adequately reproduce the shapes of the mass yield and charge yield of the experimental data for 500-MeV ..pi../sup -/. The calculation, however,more » overestimates the yield of neutron-rich isotopes from deep spallation. At the 1570-MeV ..pi../sup -/ energy the yield patterns, charge-dispersion, and mass-yield curves are nearly identical to those for 2-GeV proton spallation. These results suggest that pion-nucleon resonance effects probably decrease at higher energies and that limiting fragmentation and factorization concepts may be applied to understanding high-energy pion spallation.« less

Spallation reaction study for fission products in nuclear waste: Cross section measurements for 137Cs and 90Sr on proton and deuteron

NASA Astrophysics Data System (ADS)

Wang, H.; Otsu, H.; Sakurai, H.; Ahn, D. S.; Aikawa, M.; Doornenbal, P.; Fukuda, N.; Isobe, T.; Kawakami, S.; Koyama, S.; Kubo, T.; Kubono, S.; Lorusso, G.; Maeda, Y.; Makinaga, A.; Momiyama, S.; Nakano, K.; Niikura, M.; Shiga, Y.; Söderström, P.-A.; Suzuki, H.; Takeda, H.; Takeuchi, S.; Taniuchi, R.; Watanabe, Ya.; Watanabe, Yu.; Yamasaki, H.; Yoshida, K.

2016-03-01

We have studied spallation reactions for the fission products 137Cs and 90Sr for the purpose of nuclear waste transmutation. The spallation cross sections on the proton and deuteron were obtained in inverse kinematics for the first time using secondary beams of 137Cs and 90Sr at 185 MeV/nucleon at the RIKEN Radioactive Isotope Beam Factory. The target dependence has been investigated systematically, and the cross-section differences between the proton and deuteron are found to be larger for lighter spallation products. The experimental data are compared with the PHITS calculation, which includes cascade and evaporation processes. Our results suggest that both proton- and deuteron-induced spallation reactions are promising mechanisms for the transmutation of radioactive fission products.

Radiation damage calculations for the SINQ Target 5

NASA Astrophysics Data System (ADS)

Wechsler, Monroe S.; Lu, Wei; Dai, Yong

2003-03-01

Calculations are underway of radiation damage (production of displacements, helium, and hydrogen) at Target 5 of the SINQ spallation neutron source at the Paul Scherrer Institute in Switzerland. The target is bombarded by 575-MeV protons, and the spallation-neutron-producing target material is liquid lead. The calculations employ the Monte Carlo code MCNPX (version 2.3.0). The peak proton and neutron fluxes at the aluminum-alloy entrance window are determined to be about 1.9E14 protons/cm2s per mA of incident proton current and 2.4E13 neutrons/cm2s per mA. For a beam exposure of 10 Ahr, the peak damage sustained at the entrance window due to protons and neutrons combined is calculated to be 7.8 dpa, 2000 appmHe, and 4000 appmH. The significance of the damage results for the entrance window and components within Target 5 will be discussed.

Spallation of Cu by. pi. /sup -/ across the T = 1/2 resonances and at high energy

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

Haustein, P.E.

1979-09-01

Relative yields of 11 selected products (/sup 24/Na, /sup 43,44,46,47,48/Sc, /sup 55,56,57,58,60/Co) have been measured for the interaction of 0.6- and 0.9-GeV negative pions with Cu. In addition, the yields of /sup 24/Na and /sup 58/Co from Cu have been measured for 12-GeV ..pi../sup -/. Results at the two lower energies which correspond to the first two isospin T = 1/2 pion-nucleon resonances are compared with earlier studies of Cu spallation by ..pi../sup -/ at energies across the first T = 3/2 resonance, i.e., 50 to 350 MeV. The 12-GeV ..pi../sup -/ results are compared with similar investigations in whichmore » both energetic protons and heavy ions were used. For E/sub ..pi../ > or = 0.5 GeV no evidence of strong resonance effects can be found in the pattern of the spallation yields. As the pion energy is raised a smooth trend of enhanced yields of deep spallation products to near-target yields closely parallels the same trend observed for both high-energy proton and heavy-ion spallation of Cu. These results indicate that at high energy, pi-mesic spallation exhibits the same features of limiting fragmentation and factorization of the isotopic yields that have been observed previously in hadron induced spallation.« less

CHELSI: a portable neutron spectrometer for the 20-800 MeV region.

PubMed

McLean, T D; Olsher, R H; Romero, L L; Miles, L H; Devine, R T; Fallu-Labruyere, A; Grudberg, P

2007-01-01

CHELSI is a CsI-based portable spectrometer being developed at Los Alamos National Laboratory for use in high-energy neutron fields. Based on the inherent pulse shape discrimination properties of CsI(Tl), the instrument flags charged particle events produced via neutron-induced spallation events. Scintillation events are processed in real time using digital signal processing and a conservative estimate of neutron dose rate is made based on the charged particle energy distribution. A more accurate dose estimate can be made by unfolding the 2D charged particle versus pulse height distribution to reveal the incident neutron spectrum from which dose is readily obtained. A prototype probe has been assembled and data collected in quasi-monoenergetic fields at The Svedberg Laboratory (TSL) in Uppsala as well as at the Los Alamos Neutron Science Center (LANSCE). Preliminary efforts at deconvoluting the shape/energy data using empirical response functions derived from time-of-flight measurements are described.

Multi-criteria comparative evaluation of spallation reaction models

NASA Astrophysics Data System (ADS)

Andrianov, Andrey; Andrianova, Olga; Konobeev, Alexandr; Korovin, Yury; Kuptsov, Ilya

2017-09-01

This paper presents an approach to a comparative evaluation of the predictive ability of spallation reaction models based on widely used, well-proven multiple-criteria decision analysis methods (MAVT/MAUT, AHP, TOPSIS, PROMETHEE) and the results of such a comparison for 17 spallation reaction models in the presence of the interaction of high-energy protons with natPb.

Spallation reactions: A successful interplay between modeling and applications

NASA Astrophysics Data System (ADS)

David, J.-C.

2015-06-01

The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200MeV deuterons and 400MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. In the same year, R. Serber described the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a workshop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.

How does spallation microdamage nucleate in bulk amorphous alloys under shock loading?

NASA Astrophysics Data System (ADS)

Huang, X.; Ling, Z.; Zhang, H. S.; Ma, J.; Dai, L. H.

2011-11-01

Specially designed plate-impact experiments have been conducted on a Zr-based amorphous alloy using a single-stage light gas gun. To understand the microdamage nucleation process in the material, the samples are subjected to dynamic tensile loadings of identical amplitude (˜ 3.18 GPa) but with different durations (83-201 ns). A cellular pattern with an equiaxed shape is observed on the spallation surface, which shows that spallation in the tested amorphous alloy is a typical ductile fracture and that microvoids have been nucleated during the process. Based on the observed fracture morphologies of the spallation surface and free-volume theory, we propose a microvoid nucleation model of bulk amorphous alloys. It is found that nucleation of microvoids at the early stage of spallation in amorphous alloys results from diffusion and coalescence of free volume, and that high mean tensile stress plays a dominant role in microvoid nucleation.

Characterization of irradiated AISI 316L stainless steel disks removed from the Spallation Neutron Source

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

Vevera, Bradley J; Hyres, James W; McClintock, David A

2014-01-01

Irradiated AISI 316L stainless steel disks were removed from the Spallation Neutron Source (SNS) for post-irradiation examination (PIE) to assess mechanical property changes due to radiation damage and erosion of the target vessel. Topics reviewed include high-resolution photography of the disk specimens, cleaning to remove mercury (Hg) residue and surface oxides, profile mapping of cavitation pits using high frequency ultrasonic testing (UT), high-resolution surface replication, and machining of test specimens using wire electrical discharge machining (EDM), tensile testing, Rockwell Superficial hardness testing, Vickers microhardness testing, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The effectiveness of the cleaning proceduremore » was evident in the pre- and post-cleaning photography and permitted accurate placement of the test specimens on the disks. Due to the limited amount of material available and the unique geometry of the disks, machine fixturing and test specimen design were critical aspects of this work. Multiple designs were considered and refined during mock-up test runs on unirradiated disks. The techniques used to successfully machine and test the various specimens will be presented along with a summary of important findings from the laboratory examinations.« less

A nuclear method to measure spallation by thermal cycling of protective surface layers

NASA Astrophysics Data System (ADS)

Stroosnijder, M. F.; Macchi, G.

1995-05-01

After a general introduction on spallation by thermal cycling, the principle of Thin Layer Activation (TLA) is outlined. A practical setup to measure spallation of protective surface layers by thermal cycling using TLA is discussed. Its use is illustrated with the study of the spallation behaviour of an advanced thermal barrier coating. It is shown that among the various benefits, TLA has a direct relation to material loss and shows a significant increase in sensitivity over other test methods. Due to its intrinsic properties, TLA can contribute to a greater scientific understanding of material degradation by thermal cycling and it can provide a more reliable assessment of the service lives of technical components.

Data processing workflow for time of flight polarized neutrons inelastic measurements

DOE PAGES

Savici, Andrei T.; Zaliznyak, Igor A.; Ovidiu Garlea, V.; ...

2017-06-01

We discuss the data processing workflow for polarized neutron scattering measurements performed at HYSPEC spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. The effects of the focusing Heusler crystal polarizer and the wide-angle supermirror transmission polarization analyzer are added to the data processing flow of the non-polarized case. The implementation is done using the Mantid software package.

Single-crystal diffraction instrument TriCS at SINQ

NASA Astrophysics Data System (ADS)

Schefer, J.; Könnecke, M.; Murasik, A.; Czopnik, A.; Strässle, Th; Keller, P.; Schlumpf, N.

2000-03-01

The single-crystal diffractometer TriCS at the Swiss Continuous Spallation Source (SINQ) is presently in the commissioning phase. A two-dimensional wire detector produced by EMBL was delivered in March 1999. The instrument is presently tested with a single detector. First measurements on magnetic structures have been performed. The instrument is remotely controlled using JAVA-based software and a UNIX DEC-α host computer.

Source Physics Experiment: Research in Support of Verification and Nonproliferation

DTIC Science & Technology

2011-09-01

designed to provide a carefully controlled seismic and strong motion data set from buried explosions at the Nevada National Security Site (NNSS). The...deposition partitioned into internal (heat and plastic strain) and kinetic (e.g., radiated seismic ) energy, giving more confidence in predicted free...ample information to study dry and water-saturated fractures, local lithology and topography on the radiated seismic wavefield. Spallation on

Polarized neutron scattering on HYSPEC: the HYbrid SPECtrometer at SNS

DOE PAGES

Zaliznyak, Igor A.; Savici, Andrei T.; Ovidiu Garlea, V.; ...

2017-06-20

Here, we describe some of the first polarized neutron scattering measurements performed at HYSPEC [1-4] spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. Furthermore, we discuss details of the instrument setup and the experimental procedures in the mode with full polarization analysis. Examples of polarized neutron diffraction and polarized inelastic neutron data obtained on single crystal samples are presented.

Galactic cosmic ray composition

NASA Technical Reports Server (NTRS)

Meyer, J. P.

1986-01-01

An assessment is given of the galactic cosmic ray source (GCRS) elemental composition and its correlation with first ionization potential. The isotopic composition of heavy nuclei; spallation cross sections; energy spectra of primary nuclei; electrons; positrons; local galactic reference abundances; comparison of solar energetic particles and solar coronal compositions; the hydrogen; lead; nitrogen; helium; and germanium deficiency problems; and the excess of elements are among the topics covered.

Spallation reaction study for the long-lived fission product 107Pd

NASA Astrophysics Data System (ADS)

Wang, He; Otsu, Hideaki; Sakurai, Hiroyoshi; Ahn, DeukSoon; Aikawa, Masayuki; Ando, Takashi; Araki, Shouhei; Chen, Sidong; Nobuyuki, Chiga; Doornenbal, Pieter; Fukuda, Naoki; Isobe, Tadaaki; Kawakami, Shunsuke; Kawase, Shoichiro; Kin, Tadahiro; Kondo, Yosuke; Koyama, Shunpei; Kubono, Shigeru; Maeda, Yukie; Makinaga, Ayano; Matsushita, Masafumi; Matsuzaki, Teiichiro; Michimasa, Shin'ichiro; Momiyama, Satoru; Nagamine, Shunsuke; Nakamura, Takashi; Nakano, Keita; Niikura, Megumi; Ozaki, Tomoyuki; Saito, Atsumi; Saito, Takeshi; Shiga, Yoshiaki; Shikata, Mizuki; Shimizu, Yohei; Shimoura, Susumu; Sumikama, Toshiyuki; Söderström, Pär-Anders; Suzuki, Hiroshi; Takeda, Hiroyuki; Takeuchi, Satoshi; Taniuchi, Ryo; Togano, Yasuhiro; Tsubota, Junichi; Uesaka, Meiko; Watanabe, Yasushi; Watanabe, Yukinobu; Wimmer, Kathrin; Yamamoto, Tatsuya; Yoshida, Koichi

2017-02-01

Spallation reactions for the long-lived fission product 107Pd have been studied for the purpose of nuclear waste transmutation. The cross sections on the proton- and deuteron-induced spallation were obtained at 196 and 118 MeV/nucleon in inverse kinematics at the RIKEN Radioactive Isotope Beam Factory. Both the target and energy dependences of cross sections have been investigated systematically. It was found that the proton-induced cross sections at 196 MeV/nucleon are close to those for deuteron obtained at 118 MeV/nucleon for the light-mass products. The experimental data are compared with the SPACS semi-empirical parameterization and the PHITS calculations including both the intranuclear cascade and evaporation processes. Our data give a design goal of proton/deuteron flux for the transmutation of 107Pd using the spallation reaction. In addition, it is found that the spallation reaction at 118 MeV/nucleon may have an advantage over the 107Pd transmutation because of the low production of other long-lived radioactive isotopes.

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.

Non-Destructive Study of Bulk Crystallinity and Elemental Composition of Natural Gold Single Crystal Samples by Energy-Resolved Neutron Imaging

PubMed Central

Tremsin, Anton S.; Rakovan, John; Shinohara, Takenao; Kockelmann, Winfried; Losko, Adrian S.; Vogel, Sven C.

2017-01-01

Energy-resolved neutron imaging enables non-destructive analyses of bulk structure and elemental composition, which can be resolved with high spatial resolution at bright pulsed spallation neutron sources due to recent developments and improvements of neutron counting detectors. This technique, suitable for many applications, is demonstrated here with a specific study of ~5–10 mm thick natural gold samples. Through the analysis of neutron absorption resonances the spatial distribution of palladium (with average elemental concentration of ~0.4 atom% and ~5 atom%) is mapped within the gold samples. At the same time, the analysis of coherent neutron scattering in the thermal and cold energy regimes reveals which samples have a single-crystalline bulk structure through the entire sample volume. A spatially resolved analysis is possible because neutron transmission spectra are measured simultaneously on each detector pixel in the epithermal, thermal and cold energy ranges. With a pixel size of 55 μm and a detector-area of 512 by 512 pixels, a total of 262,144 neutron transmission spectra are measured concurrently. The results of our experiments indicate that high resolution energy-resolved neutron imaging is a very attractive analytical technique in cases where other conventional non-destructive methods are ineffective due to sample opacity. PMID:28102285

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

Ene, D.; Andersson, K.; Jensen, M.

The European Spallation Source (ESS) will produce tritium via spallation and activation processes during operational activities. Within the location of ESS facility in Lund, Sweden site it is mandatory to demonstrate that the management strategy of the produced tritium ensures the compliance with the country regulation criteria. The aim of this paper is to give an overview of the different aspects of the tritium management in ESS facility. Besides the design parameter study of the helium coolant purification system of the target the consequences of the tritium releasing into the environment were also analyzed. Calculations show that the annual releasemore » of tritium during the normal operations represents a small fraction from the estimated total dose. However, more refined calculations of migration of activated-groundwater should be performed for higher hydraulic conductivities, with the availability of the results on soil examinations. With the assumption of 100% release of tritium to the atmosphere during the occurring of the extreme accidents, it was found as well that the total dose complies with the constraint. (authors)« less

Cosmic ray models for early galactic lithium, beryllium, and boron production

NASA Technical Reports Server (NTRS)

Fields, Brian D.; Olive, Keith A.; Schramm, David N.

1994-01-01

To better understand the early galactic production of Li, Be, and B by cosmic ray spallation and fusion reactions, the dependence of these production rates on cosmic ray models and model parameters is examined. The sensitivity of elemental and isotropic production to the cosmic ray pathlength magnitude and energy dependence, source spectrum spallation kinematics, and cross section uncertainties is studied. Changes in these model features, particularly those features related to confinement, are shown to alter the Be- and B-versus-Fe slopes from a naive quadratic relation. The implications of our results for the diffuse gamma-ray background are examined, and the role of chemical evolution and its relation to our results is noted. It is also noted that the unmeasured high energy behavior of alpha + alpha fusion can lead to effects as large as a factor of 2 in the resultant yields. Future data should enable Population II Li, Be, and B abundances to constrain cosmic ray models for the early Galaxy.

The cold neutron chopper spectrometer at the Spallation Neutron Source—A review of the first 8 years of operation

DOE PAGES

Ehlers, G.; Podlesnyak, A. A.; Kolesnikov, A. I.

2016-09-13

The first eight years of operation of the Cold Neutron Chopper Spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge is being reviewed. The instrument has been part of the facility user program since 2009, and more than 250 individual user experiments have been performed to date. CNCS is an extremely powerful and versatile instrument and offers leading edge performance in terms of beam intensity, energy resolution, and flexibility to trade one for another. In addition, experiments are being routinely performed with the sample at extreme conditions: T ≲ 0.05 K, p ≳ 2 GPa, and B = 8more » T can be achieved individually or in combination. In particular, CNCS is in a position to advance the state of the art with inelastic neutron scattering under pressure, and some of the recent accomplishments in this area will be presented in more detail.« less

Cosmic-ray models for early Galactic Lithium, Beryllium, and Boron production

NASA Technical Reports Server (NTRS)

Fields, Brian D.; Olive, Keith A.; Schramm, David N.

1994-01-01

To understand better the early Galactic production of Li, Be, and B by comsmic-ray spallation and fusion reactions, the dependence of these production rates on cosmic-ray models and model parameters is examined. The sensitivity of elemental and isotopic production to the cosmic-ray path length magnitude and energy dependence, source spectrum, spallation kinematics, and cross section uncertainties is studied. Changes in these model features, particularly those features related to confinement, are shown to alter the Be- and B- versus-Fe slopes from a naive quadratic relation. The implications of our results for the diffuse gamma-ray background are examined, and the role of chemical evolution and its relation to our results is noted. It is also noted that the unmeasured high-energy behavior of alpha + alpha fusion can lead to effects as large as a factor of 2 in the resultant yields. Future data should enable Population II Li, Be, and B abundances to constrain cosmic-ray models for the early Galaxy.

Numerical simulations of stripping effects in high-intensity hydrogen ion linacs

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

Carneiro, J.-P.; /Fermilab; Mustapha, B.

2008-12-01

Numerical simulations of H{sup -} stripping losses from blackbody radiation, electromagnetic fields, and residual gas have been implemented into the beam dynamics code TRACK. Estimates of the stripping losses along two high-intensity H{sup -} linacs are presented: the Spallation Neutron Source linac currently being operated at Oak Ridge National Laboratory and an 8 GeV superconducting linac currently being designed at Fermi National Accelerator Laboratory.

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.

Superconducting Prototype Cavities for the Spallation Neutron Source (SNS) Project

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

Peter Kneisel; John Brawley; Richard Bundy

2001-06-01

The Spallation Neutron Source project includes a superconducting linac section in the energy range from 192 MeV to 1000 MeV. For this energy range two types of cavities are needed with geometrical beta - values of beta = 0.61 and beta = 0.81. An aggressive cavity prototyping program is being pursued at Jlab, which calls for fabricating and testing of four beta = 0.61 cavities and two beta = 0.81 cavities. Both types consist of six cells made from high purity niobium and feature one HOM coupler of the TESLA type on each beam pipe and a port for amore » high power coaxial input coupler. Three of the four beta = 0.61 cavities will be used for a cryomodule test at the end of the year 2001. At this time two cavities of each type have been fabricated and the first tests on the beta = 0.61 cavity exceeded the design values for gradient and Q - value: Eacc = 10.3 MV/m and Q = 6.5 x 10{sup 9} at 2.1K. This paper will describe the cavity design with respect to electrical and mechanical features, the fabrication efforts and the results obtained with the different cavities existing at the time of the conference.« less

Acoustic attenuation, phase and group velocities in liquid-filled pipes II: simulation for Spallation Neutron Sources and planetary exploration.

PubMed

Jiang, Jian; Baik, Kyungmin; Leighton, Timothy G

2011-08-01

This paper uses a finite element method (FEM) to compare predictions of the attenuation and sound speeds of acoustic modes in a fluid-filled pipe with those of the analytical model presented in the first paper in this series. It explains why, when the predictions of the earlier paper were compared with experimental data from a water-filled PMMA pipe, the uncertainties and agreement for attenuation data were worse than those for sound speed data. Having validated the FEM approach in this way, the versatility of FEM is thereafter demonstrated by modeling two practical applications which are beyond the analysis of the earlier paper. These applications model propagation in the mercury-filled steel pipework of the Spallation Neutron Source at the Oak Ridge National Laboratory (Tennessee), and in a long-standing design for acoustic sensors for use on planetary probes. The results show that strong coupling between the fluid and the solid walls means that erroneous interpretations are made of the data if they assume that the sound speed and attenuation in the fluid in the pipe are the same as those that would be measured in an infinite volume of identical fluid, assumptions which are common when such data have previously been interpreted.

Commissioning of cryogenic system for China Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Ye, Bin; He, Chongchao; Li, Na; Ding, Meiying; Wang, Yaqiong; Yu, Zhang; He, Kun

2017-12-01

China Spallation Neutron Source(CSNS) cryogenic system provides supercritical cryogenic hydrogen to neutron moderators, including a helium refrigerator, hydrogen loop and hydrogen safety equipment. The helium refrigerator is provided by Linde with cooling capacity of 2200 W at 20 K. Hydrogen loop system mainly includes cryogenic hydrogen pipes, hydrogen circulator cold-box and accumulator cold-box. Cryogenic hydrogen pump, ortho-para convertor, helium-hydrogen heat-exchanger, hydrogen heater and accumulator are integrated in hydrogen circulation cold-box, and accumulator cold-box. Hydrogen safety equipment includes safety valves, rupture disk, hydrogen sensor, flame detector and other equipment to ensure that cryogenic system in dangerous situations will go down, vents, or takes other measures. The cryogenic system commissioning work includes four steps. First, in order to test the refrigerating capacity of refrigerator, when acceptance testing, refrigerator internal heater was used as thermal load. Second, using simulation load as heat load of moderator, hydrogen loop use helium instead of hydrogen, and cooled down to 20 K, then re-warming and test the leak detection of hydrogen loop system. Third, base on the step 2, using hydrogen as working medium, and optimized the control logic. Forth, cryogenic system with the moderators joint commissioning. Now, cryogenic system is connected with the moderators, and the forth step will be carried out in the near future.

Design progress of cryogenic hydrogen system for China Spallation Neutron Source

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

Wang, G. P.; Zhang, Y.; Xiao, J.

2014-01-29

China Spallation Neutron Source (CSNS) is a large proton accelerator research facility with 100 kW beam power. Construction started in October 2011 and is expected to last 6.5 years. The cryogenic hydrogen circulation is cooled by a helium refrigerator with cooling capacity of 2200 W at 20 K and provides supercritical hydrogen to neutron moderating system. Important progresses of CSNS cryogenic system were concluded as follows. Firstly, process design of cryogenic system has been completed including helium refrigerator, hydrogen loop, gas distribution, and safety interlock. Secondly, an accumulator prototype was designed to mitigate pressure fluctuation caused by dynamic heat loadmore » from neutron moderation. Performance test of the accumulator has been carried out at room and liquid nitrogen temperature. Results show the accumulator with welding bellows regulates hydrogen pressure well. Parameters of key equipment have been identified. The contract for the helium refrigerator has been signed. Mechanical design of the hydrogen cold box has been completed, and the hydrogen pump, ortho-para hydrogen convertor, helium-hydrogen heat exchanger, hydrogen heater, and cryogenic valves are in procurement. Finally, Hydrogen safety interlock has been finished as well, including the logic of gas distribution, vacuum, hydrogen leakage and ventilation. Generally, design and construction of CSNS cryogenic system is conducted as expected.« less

In situ polarized 3He system for the Magnetism Reflectometer at the Spallation Neutron Source.

PubMed

Tong, X; Jiang, C Y; Lauter, V; Ambaye, H; Brown, D; Crow, L; Gentile, T R; Goyette, R; Lee, W T; Parizzi, A; Robertson, J L

2012-07-01

We report on the in situ polarized (3)He neutron polarization analyzer developed for the time-of-flight Magnetism Reflectometer at the Spallation Neutron Source at Oak Ridge National Laboratory. Using the spin exchange optical pumping method, we achieved a (3)He polarization of 76% ± 1% and maintained it for the entire three-day duration of the test experiment. Based on transmission measurements with unpolarized neutrons, we show that the average analyzing efficiency of the (3)He system is 98% for the neutron wavelength band of 2-5 Å. Using a highly polarized incident neutron beam produced by a supermirror bender polarizer, we obtained a flipping ratio of >100 with a transmission of 25% for polarized neutrons, averaged over the wavelength band of 2-5 Å. After the cell was depolarized for transmission measurements, it was reproducibly polarized and this performance was maintained for three weeks. A high quality polarization analysis experiment was performed on a reference sample of Fe/Cr multilayer with strong spin-flip off-specular scattering. Using a combination of the position sensitive detector, time-of-flight method, and the excellent parameters of the (3)He cell, the polarization analysis of the two-dimensional maps of reflected, refracted, and off-specular scattered intensity above and below the horizon were obtained, simultaneously.

The Interstellar 7Li/6Li Ratio in the Diffuse Gas Near IC 443

NASA Astrophysics Data System (ADS)

Ritchey, A. M.; Taylor, C. J.; Federman, S. R.; Lambert, D. L.

2010-11-01

Supernova remnants are believed to be the primary acceleration sites of Galactic cosmic rays (GCR), which are essential to gas-phase interstellar chemistry since they are a major source of ionization in both diffuse and dense environments. The interaction of accelerated particles with interstellar gas will also synthesize isotopes of the light elements Li, Be, and B through the spallation of CNO nuclei (producing all stable LiBeB isotopes) and through α+α fusion (yielding 6Li and 7Li, only). Type II supernovae may provide an additional source of 7Li and 11B during core collapse through neutrino-induced spallation in the He and C shells of the progenitor star (the ν-process). However, direct observational evidence for light element synthesis resulting from cosmic-ray or neutrino-induced spallation is rare. Here, we examine 7Li/6Li isotope ratios along four lines of sight through the supernova remnant IC 443 using observations of the Li I λ6707 doublet made with the Hobby-Eberly Telescope (HET) at McDonald Observatory. The 7Li/6Li ratio in the general interstellar medium is expected to be similar to the ratio of ~12 that characterizes solar system material. A local enhancement in the cosmic-ray flux will act to lower 7Li/6Li, yielding a ratio of ~2 when cosmic rays dominate Li synthesis. Gamma-ray emission from IC 443 provides strong evidence for the interaction of cosmic rays accelerated by the remnant with the ambient atomic and molecular gas. Yet this material has also been contaminated by the ejecta of a Type II supernova, which should be enriched in 7Li. We are seeking 7Li/6Li ratios that are either higher than the solar system ratio as a result of the ν-process or lower due to cosmic-ray spallation. Since the fine structure separation of the Li I doublet is comparable to the isotope shift (~7 km s-1) and each fine structure line is further split into hyperfine components, the velocity structure along the line of sight must be carefully constrained if meaningful 7Li/6Li ratios are to be determined. In our analysis, the strongest components seen in K I and CH are used to synthesize the complex Li I profiles. We will discuss the implications of our results on 7Li/6Li (and Li/K) ratios in the context of Li production by Type II supernovae.

Radiological assessment of target materials for accelerator transmutation of waste (ATW) applications

NASA Astrophysics Data System (ADS)

Vickers, Linda Diane

This dissertation issues the first published document of the radiation absorbed dose rate (rad-h-1) to tissue from radioactive spallation products in Ta, W, Pb, Bi, and LBE target materials used in Accelerator Transmutation of Waste (ATW) applications. No previous works have provided an estimate of the absorbed dose rate (rad-h-1) from activated targets for ATW applications. The results of this dissertation are useful for planning the radiological safety assessment to personnel, and for the design, construction, maintenance, and disposition of target materials of high-energy particle accelerators for ATW applications (Charlton, 1996). In addition, this dissertation provides the characterization of target materials of high-energy particle accelerators for the parameters of: (1) spallation neutron yield (neutrons/proton), (2) spallation products yield (nuclides/proton), (3) energy-dependent spallation neutron fluence distribution, (4) spallation neutron flux, (5) identification of radioactive spallation products for consideration in safety of personnel to high radiation dose rates, and (6) identification of the optimum geometrical dimensions for the target applicable to the maximum radial spallation neutron leakage from the target. Pb and Bi target materials yielded the lowest absorbed dose rates (rad-h -1) for a 10-year irradiation/50-year decay scheme, and would be the preferred target materials for consideration of the radiological safety of personnel during ATW operations. A beneficial characteristic of these target materials is that they do not produce radioactive transuranic isotopes, which have very long half-lives and require special handling and disposition requirements. Furthermore, the targets are not considered High-Level Waste (HLW) such as reactor spent fuel for disposal purposes. It is a basic ATW system requirement that the spallation target after it has been expended should be disposable as Class C low-level radioactive waste. Therefore, the disposal of Pb and Bi targets would be optimally beneficial to the economy and environment. Future studies should relate the target performance to other system parameters, specifically solid and liquid blanket systems that contain the radioactive waste to be transmuted. The methodology of this dissertation may be applied to any target material of a high-energy particle accelerator.

Clock distribution for BaF2 readout electronics at CSNS-WNS

NASA Astrophysics Data System (ADS)

He, Bing; Cao, Ping; Zhang, De-Liang; Wang, Qi; Zhang, Ya-Xi; Qi, Xin-Cheng; An, Qi

2017-01-01

A BaF2 (Barium Fluoride) detector array is designed to precisely measure the (n, γ) cross section at the CSNS-WNS (white neutron source at China Spallation Neutron Source). It is a 4π solid angle-shaped detector array consisting of 92 BaF2 crystal elements. To discriminate signals from the BaF2 detector, a pulse shape discrimination method is used, supported by a waveform digitization technique. There are 92 channels for digitizing. The precision and synchronization of clock distribution restricts the performance of waveform digitizing. In this paper, a clock prototype for the BaF2 readout electronics at CSNS-WNS is introduced. It is based on the PXIe platform and has a twin-stage tree topology. In the first stage, clock is synchronously distributed from the tree root to each PXIe crate through a coaxial cable over a long distance, while in the second stage, the clock is further distributed to each electronic module through a PXIe dedicated differential star bus. With the help of this topology, each tree node can fan out up to 20 clocks with 3U size. Test results show the clock jitter is less than 20 ps, which meets the requirements of the BaF2 readout electronics. Besides, this clock system has the advantages of high density, simplicity, scalability and cost saving, so it can be useful for other clock distribution applications. Supported by National Research and Development plan (2016 YFA0401602) NSAF (U1530111) and National Natural Science Foundation of China (11005107)

Electron-cloud updated simulation results for the PSR, and recent results for the SNS

NASA Astrophysics Data System (ADS)

Pivi, M.; Furman, M. A.

2002-05-01

Recent simulation results for the main features of the electron cloud in the storage ring of the Spallation Neutron Source (SNS) at Oak Ridge, and updated results for the Proton Storage Ring (PSR) at Los Alamos are presented in this paper. A refined model for the secondary emission process including the so called true secondary, rediffused and backscattered electrons has recently been included in the electron-cloud code.

Integrating labview into a distributed computing environment.

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

Kasemir, K. U.; Pieck, M.; Dalesio, L. R.

2001-01-01

Being easy to learn and well suited for a selfcontained desktop laboratory setup, many casual programmers prefer to use the National Instruments Lab-VIEW environment to develop their logic. An ActiveX interface is presented that allows integration into a plant-wide distributed environment based on the Experimental Physics and Industrial Control System (EPICS). This paper discusses the design decisions and provides performance information, especially considering requirements for the Spallation Neutron Source (SNS) diagnostics system.

Study on the Fire Damage Characteristics of the New Qidaoliang Highway Tunnel: Field Investigation with Computational Fluid Dynamics (CFD) Back Analysis

PubMed Central

Lai, Hongpeng; Wang, Shuyong; Xie, Yongli

2016-01-01

In the New Qidaoliang Tunnel (China), a rear-end collision of two tanker trunks caused a fire. To understand the damage characteristics of the tunnel lining structure, in situ investigation was performed. The results show that the fire in the tunnel induced spallation of tunnel lining concrete covering 856 m3; the length of road surface damage reached 650 m; the sectional area had a maximum 4% increase, and the mechanical and electrical facilities were severely damaged. The maximum area loss happened at the fire spot with maximum observed concrete spallation up to a thickness of 35.4 cm. The strength of vault and side wall concrete near the fire source was significantly reduced. The loss of concrete strength of the side wall near the inner surface of tunnel was larger than that near the surrounding rock. In order to perform back analysis of the effect of thermal load on lining structure, simplified numerical simulation using computational fluid dynamics (CFD) was also performed, repeating the fire scenario. The simulated results showed that from the fire breaking out to the point of becoming steady, the tunnel experienced processes of small-scale warming, swirl around fire, backflow, and longitudinal turbulent flow. The influence range of the tunnel internal temperature on the longitudinal downstream was far greater than on the upstream, while the high temperature upstream and downstream of the transverse fire source mainly centered on the vault or the higher vault waist. The temperature of each part of the tunnel near the fire source had no obvious stratification phenomenon. The temperature of the vault lining upstream and downstream near the fire source was the highest. The numerical simulation is found to be in good agreement with the field observations. PMID:27754455

Study on the Fire Damage Characteristics of the New Qidaoliang Highway Tunnel: Field Investigation with Computational Fluid Dynamics (CFD) Back Analysis.

PubMed

Lai, Hongpeng; Wang, Shuyong; Xie, Yongli

2016-10-15

In the New Qidaoliang Tunnel (China), a rear-end collision of two tanker trunks caused a fire. To understand the damage characteristics of the tunnel lining structure, in situ investigation was performed. The results show that the fire in the tunnel induced spallation of tunnel lining concrete covering 856 m³; the length of road surface damage reached 650 m; the sectional area had a maximum 4% increase, and the mechanical and electrical facilities were severely damaged. The maximum area loss happened at the fire spot with maximum observed concrete spallation up to a thickness of 35.4 cm. The strength of vault and side wall concrete near the fire source was significantly reduced. The loss of concrete strength of the side wall near the inner surface of tunnel was larger than that near the surrounding rock. In order to perform back analysis of the effect of thermal load on lining structure, simplified numerical simulation using computational fluid dynamics (CFD) was also performed, repeating the fire scenario. The simulated results showed that from the fire breaking out to the point of becoming steady, the tunnel experienced processes of small-scale warming, swirl around fire, backflow, and longitudinal turbulent flow. The influence range of the tunnel internal temperature on the longitudinal downstream was far greater than on the upstream, while the high temperature upstream and downstream of the transverse fire source mainly centered on the vault or the higher vault waist. The temperature of each part of the tunnel near the fire source had no obvious stratification phenomenon. The temperature of the vault lining upstream and downstream near the fire source was the highest. The numerical simulation is found to be in good agreement with the field observations.

Study of proton- and deuteron-induced spallation reactions on the long-lived fission product 93Zr at 105 MeV/nucleon in inverse kinematics

NASA Astrophysics Data System (ADS)

Kawase, Shoichiro; Nakano, Keita; Watanabe, Yukinobu; Wang, He; Otsu, Hideaki; Sakurai, Hiroyoshi; Ahn, Deuk Soon; Aikawa, Masayuki; Ando, Takashi; Araki, Shouhei; Chen, Sidong; Chiga, Nobuyuki; Doornenbal, Pieter; Fukuda, Naoki; Isobe, Tadaaki; Kawakami, Shunsuke; Kin, Tadahiro; Kondo, Yosuke; Koyama, Shunpei; Kubono, Shigeru; Maeda, Yukie; Makinaga, Ayano; Matsushita, Masafumi; Matsuzaki, Teiichiro; Michimasa, Shin'ichiro; Momiyama, Satoru; Nagamine, Shunsuke; Nakamura, Takashi; Niikura, Megumi; Ozaki, Tomoyuki; Saito, Atsumi; Saito, Takeshi; Shiga, Yoshiaki; Shikata, Mizuki; Shimizu, Yohei; Shimoura, Susumu; Sumikama, Toshiyuki; Söderström, Pär-Anders; Suzuki, Hiroshi; Takeda, Hiroyuki; Takeuchi, Satoshi; Taniuchi, Ryo; Togano, Yasuhiro; Tsubota, Jun'ichi; Uesaka, Meiko; Watanabe, Yasushi; Wimmer, Kathrin; Yamamoto, Tatsuya; Yoshida, Koichi

2017-09-01

Spallation reactions for the long-lived fission product ^{93}Zr have been studied in order to provide basic data necessary for nuclear waste transmutation. Isotopic-production cross sections via proton- and deuteron-induced spallation reactions on ^{93}Zr at 105 MeV/nucleon were measured in inverse kinematics at the RIKEN Radioactive Isotope Beam Factory. Remarkable jumps in isotopic production originating from the neutron magic number N=50 were observed in Zr and Y isotopes. The experimental results were compared to the PHITS calculations considering both the intranuclear cascade and evaporation processes, and the calculations greatly overestimated the measured production yield, corresponding to few-nucleon-removal reactions. The present data suggest that the spallation reaction is a potential candidate for the treatment of ^{93}Zr in spent nuclear fuel.

On the spectrum of stable secondary nuclei in cosmic rays

NASA Astrophysics Data System (ADS)

Blasi, P.

2017-10-01

The ratio of the fluxes of secondary and primary nuclei in cosmic rays has long been used as an indicator of the grammage traversed in the journey of cosmic ray particles throughout the Galaxy. The basic idea is that primary particles are accelerated in astrophysical sources, such as supernova remnant shocks and eventually propagate in the Galactic volume, occasionally interacting with gas, mainly in the disc of the Galaxy, and there they produce secondary nuclei through spallation. At sufficiently high energy, typically ≳100 GeV/n, the ratio of fluxes of the secondary nucleus to that of the main primary nucleus is found to scale as Ek^{-δ }, where Ek is the energy per nucleon (a conserved quantity in spallation reactions) and δ identifies the energy dependence of the diffusion coefficient. The same shock waves that may be responsible for cosmic ray acceleration in the first place also pick up any other charged particle in the upstream, provided being above threshold for injection. The secondary nuclei produced by spallation in the interstellar medium are no exception, hence they also get accelerated. This effect is unavoidable, only its strength may be subject of debate. We compute the spectrum of secondary elements such as boron and lithium taking into account shock reacceleration and compare our predictions with the recent observations of the B/C ratio and preliminary measurements of the boron and lithium flux. Both these sets of data seem to confirm that reacceleration of secondary nuclei indeed plays an important role, thereby affecting the validity of those scaling rules that are often used in cosmic ray physics.

First measurement of the VESUVIO neutron spectrum in the 30-80 MeV energy range using a Proton Recoil Telescope technique

NASA Astrophysics Data System (ADS)

Cazzaniga, C.; Tardocchi, M.; Croci, G.; Frost, C.; Giacomelli, L.; Grosso, G.; Hjalmarsson, A.; Rebai, M.; Rhodes, N. J.; Schooneveld, E. M.; Gorini, G.

2013-11-01

Measurements of the fast neutron energy spectrum at the ISIS spallation source are reported. The measurements were performed with a Proton Recoil Telescope consisting of a thin plastic foil placed in the neutron beam and two scintillator detectors. Results in the neutron energy range 30 MeV < En < 80 MeV are in good agreement with Monte Carlo simulations of the neutron spectrum.

Pretest predictions of surface strain and fluid pressures in mercury targets undergoing thermal shock

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

Taleyarkhan, R.P.; Kim, S.H.; Haines, J.

The authors provide a perspective overview of pretest modeling and analysis work related to thermal shock effects in spallation neutron source targets that were designed for conducting thermal shock experiments at the Los Alamos Neutron Science Center (LANSCE). Data to be derived are to be used for benchmarking computational tools as well as to assess the efficacy of optical gauges for monitoring dynamic fluid pressures and phenomena such as the onset of cavitation.

Source Amplitudes of NTS Explosions Inferred from Rayleigh Waves at Albuquerque and Tucson

DTIC Science & Technology

1978-06-01

explosions almost always cause spallation near the free surface (e.g., Eisler and Chilton, 1964). When the spalled material falls back to the surface...spall closure), some impulse is delivered and a large signal associated with spall closure can often be observed on near- field recordings (e.g., Eisler ...made for the extent of the spall region ( Eisler and Chilton, 1964; Viecelli, 1973; Sobel, 1978). Viecelli (1973) studied the data for six explosions

Thermohydraulic behavior of the liquid metal target of a spallation neutron source

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

Takeda, Y.

1996-06-01

The author presents work done on three main problems. (1) Natural circulation in double coaxial cylindircal container: The thermohydraulic behaviour of the liquid metal target of the spallation neutron source at PSI has been investigated. The configuration is a natural-circulation loop in a concentric double-tube-type container. The results show that the natural-circulation loop concept is valid for the design phase of the target construction, and the current specified design criteria will be fulfilled with the proposed parameter values. (2) Flow around the window: Water experiments were performed for geometry optimisation of the window shape of the SINQ container for avoidingmore » generating recirculation zones at peripheral area and the optimal cooling of the central part of the beam entrance window. Flow visualisation technique was mainly used for various window shapes, gap distance between the window and the guide tube edge. (3) Flow in window cooling channels: Flows in narrow gaps of cooling channels of two different types of windows were studied by flow visualisation techniques. One type is a slightly curved round cooling channel and the other is hemispherical shape, both of which have only 2 mm gap distance and the water inlet is located on one side and flows out from the opposite side. In both cases, the central part of the flow area has lower velocity than peripheral area.« less

Design of horizontal test cryostat for testing two 650 MHz cavities: cryogenic considerations

NASA Astrophysics Data System (ADS)

Khare, P.; Gilankar, S.; Kush, P. K.; Lakshminarayanan, A.; Choubey, R.; Ghosh, R.; Jain, A.; Patel, H.; Gupta, P. D.; Hocker, A.; Ozelis, J. P.; Geynisman, M.; Reid, C.; Poloubotko, V.; Mitchell, D.; Peterson, T. J.; Nicol, T. H.

2017-02-01

Horizontal Test Cryostat has been designed for testing two 650 MHz "dressed" Superconducting Radio Frequency (SCRF) cavities in a single testing cycle at Raja Ramanna Centre for Advanced Technology, India (RRCAT) in collaboration with Fermi National Accelerator Laboratory, USA (FNAL). This cryostat will facilitate testing of two 5-cell 650 MHz SCRF cavities, in CW or pulsed regime, for upcoming High Intensity Superconducting Proton Accelerator projects at both countries. Two such HTS facilities are planned, one at RRCAT for Indian Spallation Neutron Source project (ISNS), which is on the horizon, and the other at FNAL, USA. A test cryostat, a part of horizontal test stand-2 (HTS-2) will be set up at RRCAT for Indian project. In order to maximize the utility of this facility, it can also be used to test two dressed 9-cell 1.3 GHz cavities and other similarly-sized devices. The facility assumes, as an input, the availability of liquid nitrogen at 80 K and liquid helium at 4.5 K and 2 K, with a refrigeration capacity of approximately 50 W at 2 K. Design work of cryostat has been completed and now procurement process is in progress. This paper discusses salient features of the cryostat. It also describes different design calculations and ANSYS analysis for cool down of few subsystems like cavity support system and liquid nitrogen cooled thermal radiation shield of horizontal test cryostat..

Moisture-Induced Spallation and Interfacial Hydrogen Embrittlement of Alumina Scales

NASA Technical Reports Server (NTRS)

Smialek, James L.

2005-01-01

Thermal expansion mismatch stresses and interfacial sulfur activity are the major factors producing primary Al2O3 scale spallation on high temperature alloys. However, moisture-induced delayed spallation appears as a secondary, but often dramatic, illustration of an additional mechanistic detail. A historical review of delayed failure of alumina scales and TBC s on superalloys is presented herein. Similarities with metallic phenomena suggest that hydrogen embrittlement from ambient humidity, resulting from the reaction Al+3H2O=Al(OH)3+3H(+)+3e(-), is the operative mechanism. This proposal was tested by standard cathodic hydrogen charging in 1N H2SO4, applied to Rene N5 pre-oxidized at 1150 C for 1000 1-hr cycles, and monitored by weight change, induced current, and microstructure. Here cathodic polarization at -2.0 V abruptly stripped mature Al2O3 scales at the oxide-metal interface. Anodic polarization at +2.0 V, however, produced alloy dissolution. Finally, with no applied voltage, the electrolyte alone produced neither scale spallation nor alloy dissolution. These experiments thus highlight the detrimental effects of hydrogen charging on alumina scale adhesion. It is proposed that interfacial hydrogen embrittlement is produced by moist air and is the root cause of both moisture-induced, delayed scale spallation and desktop TBC failures.

Effects of displacement damage and helium production rates on the nucleation and growth of helium bubbles - Positron annihilation spectroscopy aspects

NASA Astrophysics Data System (ADS)

Krsjak, Vladimir; Degmova, Jarmila; Sojak, Stanislav; Slugen, Vladimir

2018-02-01

Fe-12 wt% Cr model alloy samples were implanted by 250 keV He2+ ions to three different fluencies (3 × 1017, 9 × 1017 and 1.5 × 1018 cm-2) at T < 100 °C. In a depth profile manner, the implantation impact according to defined peak profile was investigated using variable energy slow positrons, with the primary focus on the 2-13 dpa region. The obtained data were compared to published data on Optifer IX steel samples [1] irradiated in the frame of a two-years irradiation program of the Swiss Spallation Neutron Source. Bi-modal defect distribution represented by two defect components in positron lifetime spectrum reveals two distinct helium bubbles growth mechanisms. While at the lower helium production rate of the spallation environment, the bubbles grow primarily by migration and coalescence, at the high production rates of helium in the implanted samples, the results indicate this growth is driven by Ostwald ripening mechanism. A competitive growth process via emission of interstitial atoms (clusters) is discussed in terms of low-temperature He implantations.

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 Particle Accelerator Simulation Code PyORBIT

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

Gorlov, Timofey V; Holmes, Jeffrey A; Cousineau, Sarah M

2015-01-01

The particle accelerator simulation code PyORBIT is presented. The structure, implementation, history, parallel and simulation capabilities, and future development of the code are discussed. The PyORBIT code is a new implementation and extension of algorithms of the original ORBIT code that was developed for the Spallation Neutron Source accelerator at the Oak Ridge National Laboratory. The PyORBIT code has a two level structure. The upper level uses the Python programming language to control the flow of intensive calculations performed by the lower level code implemented in the C++ language. The parallel capabilities are based on MPI communications. The PyORBIT ismore » an open source code accessible to the public through the Google Open Source Projects Hosting service.« 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

SNS Proton Beam Window Disposal

NASA Astrophysics Data System (ADS)

Popova, Irina; Gallmeier, Franz X.; Trotter, Steven

2017-09-01

In order to support the disposal of the proton beam window assembly of the Spallation Neutron Source beamline to the target station, waste classification analyses are performed. The window has a limited life-time due to radiation-induced material damage. Analyses include calculation of the radionuclide inventory and shielding analyses for the transport package/container to ensure that the container is compliant with the transportation and waste management regulations. In order to automate this procedure and minimize manual work a script in Perl language was written.

Mercury Thermal Hydraulic Loop (MTHL) Summary Report

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

Felde, David K.; Crye, Jason Michael; Wendel, Mark W.

2017-03-01

The Spallation Neutron Source (SNS) is a high-power linear accelerator built at Oak Ridge National Laboratory (ORNL) which incorporates the use of a flowing liquid mercury target. The Mercury Thermal Hydraulic Loop (MTHL) was constructed to investigate and verify the heat transfer characteristics of liquid mercury in a rectangular channel. This report provides a compilation of previously reported results from the water-cooled and electrically heated straight and curved test sections that simulate the geometry of the window cooling channel in the target nose region.

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

Lindroos M.; Calaga R.; Bousson S.

In 2003 the joint European effort to design a European Spallation Source (ESS) resulted in a set of reports, and in May 2009 Lund was agreed to be the ESS site. The ESS Scandinavia office has since then worked on setting all the necessary legal and organizational matters in place so that the Design Update and construction can be started in January 2011, in collaboration with European partners. The Design Update phase is expected to end in 2012, to be followed by a construction phase, with first neutrons expected in 2018-2019.

Missing pulse detector for a variable frequency source

DOEpatents

Ingram, Charles B.; Lawhorn, John H.

1979-01-01

A missing pulse detector is provided which has the capability of monitoring a varying frequency pulse source to detect the loss of a single pulse or total loss of signal from the source. A frequency-to-current converter is used to program the output pulse width of a variable period retriggerable one-shot to maintain a pulse width slightly longer than one-half the present monitored pulse period. The retriggerable one-shot is triggered at twice the input pulse rate by employing a frequency doubler circuit connected between the one-shot input and the variable frequency source being monitored. The one-shot remains in the triggered or unstable state under normal conditions even though the source period is varying. A loss of an input pulse or single period of a fluctuating signal input will cause the one-shot to revert to its stable state, changing the output signal level to indicate a missing pulse or signal.

SNS Emittance Scanner, Increasing Sensitivity and Performance through Noise Mitigation ,Design, Implementation and Results

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

Pogge, J.

2006-11-20

The Spallation Neutron Source (SNS) accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The SNS MEBT Emittance Harp consists of 16 X and 16 Y wires, located in close proximity to the RFQ, Source, and MEBT Choppers. Beam Studies for source and LINAC commissioning required an overall increase in sensitivity for halo monitoring and measurement, and at the same time several severe noise sources had to be effectively removed from the harp signals. This paper is an overview of the design approach and techniques used in increasing gainmore » and sensitivity while maintaining a large signal to noise ratio for the emittance scanner device. A brief discussion of the identification of the noise sources, the mechanism for transmission and pick up, how the signals were improved and a summary of results.« less

Multimaterial lamination as a means of retarding penetration and spallation failures in plates

NASA Technical Reports Server (NTRS)

Dibattista, J. D.; Humes, D. H.

1972-01-01

Experimental data are presented which show that hypervelocity impact spallation and penetration failures of a single solid aluminum plate and of a solid aluminum plate spaced a distance behind a Whipple meteor bumper may be retarded by replacing the solid aluminum plate with a laminated plate. Four sets of experiments were conducted. The first set of experiments was conducted with projectile mass and velocity held constant and with polycarbonate cylinders impacted into single plates of different construction. The second set of experiments was done with single plates of various construction and aluminum spherical projectiles of similar mass but different velocities. These two experiments showed that a laminated plate of aluminum and polycarbonate or aluminum and methyl methacrylate could prevent spallation and penetration failures with a lower areal density than either an all-aluminum laminated plate or a solid aluminum plate. The aluminum laminated plate was in turn superior to the solid aluminum plate in resisting spallation and penetration failures. In addition, through an example of 6061-T6 aluminum and methyl methacrylate, it is shown that a laminated structure ballistically superior to its parent materials may be built. The last two sets of experiments were conducted using bumper-protected main walls of solid aluminum and of laminated aluminum and polycarbonate. Again, under hypervelocity impact conditions, the laminated main walls were superior to the solid aluminum main walls in retarding spallation and penetration failures.

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.

Development of a moderator system for the High Brilliance Neutron Source project

NASA Astrophysics Data System (ADS)

Dabruck, J. P.; Cronert, T.; Rücker, U.; Bessler, Y.; Klaus, M.; Lange, C.; Butzek, M.; Hansen, W.; Nabbi, R.; Brückel, T.

2016-11-01

The project for an accelerator based high brilliance neutron source HBS driven by Forschungszentrum Jülich forsees the use of the nuclear Be(p,n) or Be(d,n) reaction with accelerated particles in the lower MeV energy range. The lower neutron production compared to spallation has to be compensated by improving the neutron extraction process and optimizing the brilliance. Design and optimiziation of the moderator system are conducted with MCNP and will be validated with measurements at the AKR-2 training reactor by means of a prototype assembly where, e.g., the effect of different liquid H2 ortho/para ratios will be investigated and controlled in realtime via online heat capacity measurements.

Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

DOE PAGES

Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; ...

2016-01-01

Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. But, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elasticmore » and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. Furthermore, to demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr 64Ni 36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample ( 100 mg).« less

Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

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

Mauro, N. A., E-mail: namauro@noctrl.edu; Vogt, A. J.; Derendorf, K. S.

2016-01-15

Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. However, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elasticmore » and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. To demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr{sub 64}Ni{sub 36} measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample (∼100 mg)« less

Spallation reaction study for fission products in nuclear waste: Cross section measurements for 137Cs, 90Sr and 107Pd on proton and deuteron

NASA Astrophysics Data System (ADS)

Wang, He; Otsu, Hideaki; Sakurai, Hiroyoshi; Ahn, DeukSoon; Aikawa, Masayuki; Ando, Takashi; Araki, Shouhei; Chen, Sidong; Chiga, Nobuyuki; Doornenbal, Pieter; Fukuda, Naoki; Isobe, Tadaaki; Kawakami, Shunsuke; Kawase, Shoichiro; Kin, Tadahiro; Kondo, Yosuke; Koyama, Shupei; Kubono, Shigeru; Maeda, Yukie; Makinaga, Ayano; Matsushita, Masafumi; Matsuzaki, Teiichiro; Michimasa, Shinichiro; Momiyama, Satoru; Nagamine, Shunsuke; Nakamura, Takashi; Nakano, Keita; Niikura, Megumi; Ozaki, Tomoyuki; Saito, Atsumi; Saito, Takeshi; Shiga, Yoshiaki; Shikata, Mizuki; Shimizu, Yohei; Shimoura, Susumu; Sumikama, Toshiyuki; Söderström, Pär-Anders; Suzuki, Hiroshi; Takeda, Hiroyuki; Takeuchi, Satoshi; Taniuchi, Ryo; Togano, Yasuhiro; Tsubota, Junichi; Uesaka, Meiko; Watanabe, Yasushi; Watanabe, Yukinobu; Wimmer, Kathrin; Yamamoto, Tatsuya; Yoshida, Koichi

2017-09-01

Spallation reactions for the long-lived fission products 137Cs, 90Sr and 107Pd have been studied for the purpose of nuclear waste transmutation. The cross sections on the proton- and deuteron-induced spallation were obtained in inverse kinematics at the RIKEN Radioactive Isotope Beam Factory. Both the target and energy dependences of cross sections have been investigated systematically. and the cross-section differences between the proton and deuteron are found to be larger for lighter fragments. The experimental data are compared with the SPACS semi-empirical parameterization and the PHITS calculations including both the intra-nuclear cascade and evaporation processes.

Optically pulsed electron accelerator

DOEpatents

Fraser, John S.; Sheffield, Richard L.

1987-01-01

An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radio frequency powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

Optically pulsed electron accelerator

DOEpatents

Fraser, J.S.; Sheffield, R.L.

1985-05-20

An optically pulsed electron accelerator can be used as an injector for a free electron laser and comprises a pulsed light source, such as a laser, for providing discrete incident light pulses. A photoemissive electron source emits electron bursts having the same duration as the incident light pulses when impinged upon by same. The photoemissive electron source is located on an inside wall of a radiofrequency-powered accelerator cell which accelerates the electron burst emitted by the photoemissive electron source.

Moisture-Induced Delayed Alumina Scale Spallation on a Ni(Pt)Al Coating

NASA Technical Reports Server (NTRS)

Smialek, James L.

2009-01-01

Delayed interfacial scale failure takes place after cooling for samples of a Ni(Pt)Al-coated CMSX4 single crystal superalloy, cycled at 1150 C for up to 2000 hr. One sample exhibited premature coating grain boundary wrinkling, alumina scale spallation to bare metal, and a final weight loss of 3.3 mg/cm2 . Spallation under ambient conditions was monitored with time after cooldown and was found to continue for 24 hr. This produced up to 0.05 mg/cm2 additional loss for each hold, accumulating 0.7 mg/cm 2 (20 percent of the total) over the course of the test. After test termination, water immersion produced an additional 0.15 mg/cm2 loss. (A duplicate sample produced much less wrinkling and time dependent spalling, maintaining a net weight gain.) The results are consistent with the general phenomena of moisture-induced delayed spallation (MIDS) of mature, distressed alumina scales formed on oxidation resistant M-Al alloys. Relative ambient humidity is discussed as the factor controlling adsorbed moisture, reaction with the substrate, and hydrogen effects on interface strength.

Universal odd-even staggering in isotopic fragmentation and spallation cross sections of neutron-rich fragments

NASA Astrophysics Data System (ADS)

Mei, B.; Tu, X. L.; Wang, M.

2018-04-01

An evident odd-even staggering (OES) in fragment cross sections has been experimentally observed in many fragmentation and spallation reactions. However, quantitative comparisons of this OES effect in different reaction systems are still scarce for neutron-rich nuclei near the neutron drip line. By employing a third-order difference formula, the magnitudes of this OES in extensive experimental cross sections are systematically investigated for many neutron-rich nuclei with (N -Z ) from 1 to 23 over a broad range of atomic numbers (Z ≈3 -50 ). A comparison of these magnitude values extracted from fragment cross sections measured in different fragmentation and spallation reactions with a large variety of projectile-target combinations over a wide energy range reveals that the OES magnitude is almost independent of the projectile-target combinations and the projectile energy. The weighted average of these OES magnitudes derived from cross sections accurately measured in different reaction systems is adopted as the evaluation value of the OES magnitude. These evaluated OES magnitudes are recommended to be used in fragmentation and spallation models to improve their predictions for fragment cross sections.

High-efficiency Resonant rf Spin Rotator with Broad Phase Space Acceptance for Pulsed Polarized Cold Neutron Beams

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

Seo, P. -N.; Barron-Palos, L.; Bowman, J. D.

2008-01-01

High precision fundamental neutron physics experiments have been proposed for the intense pulsed spallation neutron beams at JSNS, LANSCE, and SNS to test the standard model and search for new physics. Certain systematic effects in some of these experiments have to be controlled at the few ppb level. The NPD Gamma experiment, a search for the small parity-violating {gamma}-ray asymmetry A{sub Y} in polarized cold neutron capture on parahydrogen, is one example. For the NPD Gamma experiment we developed a radio-frequency resonant spin rotator to reverse the neutron polarization in a 9.5 cm x 9.5 cm pulsed cold neutron beammore » with high efficiency over a broad cold neutron energy range. The effect of the spin reversal by the rotator on the neutron beam phase space is compared qualitatively to rf neutron spin flippers based on adiabatic fast passage. We discuss the design of the spin rotator and describe two types of transmission-based neutron spin-flip efficiency measurements where the neutron beam was both polarized and analyzed by optically polarized {sup 3}He neutron spin filters. The efficiency of the spin rotator was measured at LANSCE to be 98.8 {+-} 0.5% for neutron energies from 3 to 20 meV over the full phase space of the beam. Systematic effects that the rf spin rotator introduces to the NPD Gamma experiment are considered.« less

Thermal barrier coating life prediction model development, phase 2

NASA Technical Reports Server (NTRS)

Meier, Susan Manning; Sheffler, Keith D.; Nissley, David M.

1991-01-01

The objective of this program was to generate a life prediction model for electron-beam-physical vapor deposited (EB-PVD) zirconia thermal barrier coating (TBC) on gas turbine engine components. Specific activities involved in development of the EB-PVD life prediction model included measurement of EB-PVD ceramic physical and mechanical properties and adherence strength, measurement of the thermally grown oxide (TGO) growth kinetics, generation of quantitative cyclic thermal spallation life data, and development of a spallation life prediction model. Life data useful for model development was obtained by exposing instrumented, EB-PVD ceramic coated cylindrical specimens in a jet fueled burner rig. Monotonic compression and tensile mechanical tests and physical property tests were conducted to obtain the EB-PVD ceramic behavior required for burner rig specimen analysis. As part of that effort, a nonlinear constitutive model was developed for the EB-PVD ceramic. Spallation failure of the EB-PVD TBC system consistently occurred at the TGO-metal interface. Calculated out-of-plane stresses were a small fraction of that required to statically fail the TGO. Thus, EB-PVD spallation was attributed to the interfacial cracking caused by in-plane TGO strains. Since TGO mechanical properties were not measured in this program, calculation of the burner rig specimen TGO in-plane strains was performed by using alumina properties. A life model based on maximum in-plane TGO tensile mechanical strain and TGO thickness correlated the burner rig specimen EB-PVD ceramic spallation lives within a factor of about plus or minus 2X.

Hydrodynamic Modeling of Free Surface Interactions and Implications for P and Rg Waves Recorded on the Source Physics Experiments

NASA Astrophysics Data System (ADS)

Larmat, C. S.; Rougier, E.; Knight, E.; Yang, X.; Patton, H. J.

2013-12-01

A goal of the Source Physics Experiments (SPE) is to develop explosion source models expanding monitoring capabilities beyond empirical methods. The SPE project combines field experimentation with numerical modelling. The models take into account non-linear processes occurring from the first moment of the explosion as well as complex linear propagation effects of signals reaching far-field recording stations. The hydrodynamic code CASH is used for modelling high-strain rate, non-linear response occurring in the material near the source. Our development efforts focused on incorporating in-situ stress and fracture processes. CASH simulates the material response from the near-source, strong shock zone out to the small-strain and ultimately the elastic regime where a linear code can take over. We developed an interface with the Spectral Element Method code, SPECFEM3D, that is an efficient implementation on parallel computers of a high-order finite element method. SPECFEM3D allows accurate modelling of wave propagation to remote monitoring distance at low cost. We will present CASH-SPECFEM3D results for SPE1, which was a chemical detonation of about 85 kg of TNT at 55 m depth in a granitic geologic unit. Spallation was observed for SPE1. Keeping yield fixed we vary the depth of the source systematically and compute synthetic seismograms to distances where the P and Rg waves are separated, so that analysis can be performed without concern about interference effects due to overlapping energy. We study the time and frequency characteristics of P and Rg waves and analyse them in regard to the impact of free-surface interactions and rock damage resulting from those interactions. We also perform traditional CMT inversions as well as advanced CMT inversions, developed at LANL to take into account the damage. This will allow us to assess the effect of spallation on CMT solutions as well as to validate our inversion procedure. Further work will aim to validate the developed models with the data recorded on SPEs. This long-term goal requires taking into account the 3D structure and thus a comprehensive characterization of the site.

Miniature multichannel biotelemeter system

NASA Technical Reports Server (NTRS)

Carraway, J. B.; Sumida, J. T. (Inventor)

1974-01-01

A miniature multichannel biotelemeter system is described. The system includes a transmitter where signals from different sources are sampled to produce a wavetrain of pulses. The transmitter also separates signals by sync pulses. The pulses amplitude modulate a radio frequency carrier which is received at a receiver unit. There the sync pulses are detected by a demultiplexer which routes the pulses from each different source to a separate output channel where the pulses are used to reconstruct the signals from the particular source.

Toward high-efficiency and detailed Monte Carlo simulation study of the granular flow spallation target

NASA Astrophysics Data System (ADS)

Cai, Han-Jie; Zhang, Zhi-Lei; Fu, Fen; Li, Jian-Yang; Zhang, Xun-Chao; Zhang, Ya-Ling; Yan, Xue-Song; Lin, Ping; Xv, Jian-Ya; Yang, Lei

2018-02-01

The dense granular flow spallation target is a new target concept chosen for the Accelerator-Driven Subcritical (ADS) project in China. For the R&D of this kind of target concept, a dedicated Monte Carlo (MC) program named GMT was developed to perform the simulation study of the beam-target interaction. Owing to the complexities of the target geometry, the computational cost of the MC simulation of particle tracks is highly expensive. Thus, improvement of computational efficiency will be essential for the detailed MC simulation studies of the dense granular target. Here we present the special design of the GMT program and its high efficiency performance. In addition, the speedup potential of the GPU-accelerated spallation models is discussed.

Determination of neutron multiplication coefficients for fuel elements irradiated by spallation neutrons

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

Bhatia, Chitra; Kumar, V.

2010-02-15

A neutron multiplication coefficient, k{sub eff}, has been estimated for spallation neutron flux using the data of spectrum average cross sections of all absorption, fission, and nonelastic reaction channels of {sup 232}Th, {sup 238}U, {sup 235}U, and {sup 233}U fuel elements. It has been revealed that in spallation neutron flux (i) nonfission, nonabsorption reactions play an important role in the calculation of k{sub eff}, (ii) one can obtain a high value of k{sub eff} even for fertile {sup 232}Th fuel, which is hardly possible in a conventional fast reactor, and (iii) spectrum average absorption cross sections of neutron poisons ofmore » a conventional reactor are relatively very small.« less

Helium (3) Rich Solar Flares

DOE R&D Accomplishments Database

Colgate, S. A.; Audouze, J.; Fowler, W. A.

1977-05-03

The extreme enrichment of {sup 3} He {sup 4} He greater than or equal to 1 in some solar flares as due to spallation and the subsequent confinement of the products in a high temperature, kT approx. = 200 keV, high density, n{sub e} approx. = 3 x 10{sup 15} cm {sup -3} plasma associated with the magnetic instability producing the flare is interpreted. The pinch or filament is a current of high energy protons that creates the spallation and maintains the temperature that produces the high energy x-ray spectrum and depletes other isotopes D, Li, Be, and B as observed. Finally the high temperature plasma is a uniquely efficient spallation target that is powered by the interaction of stellar convection and self generated magnetic field.

Analysis of CRRES PHA Data for Low-Energy-Deposition Events

NASA Technical Reports Server (NTRS)

McNulty, P. J.; Hardage, Donna

2004-01-01

This effort analyzed the low-energy deposition Pulse Height Analyzer (PHA) data from the Combined Release and Radiation Effects Satellite (CRRES). The high-energy deposition data had been previously analyzed and shown to be in agreement with spallation reactions predicted by the Clemson University Proton Interactions in Devices (CUPID) simulation model and existing environmental and orbit positioning models (AP-8 with USAF B-L coordinates). The scope of this project was to develop and improve the CUPID model by increasing its range to lower incident particle energies, and to expand the modeling to include contributions from elastic interactions. Before making changes, it was necessary to identify experimental data suitable for benchmarking the codes; then, the models to the CRRES PHA data could be applied. It was also planned to test the model against available low-energy proton or neutron SEU data obtained with mono-energetic beams.

DANCE : Device for Measurement of (n.g.) Reactions on radioactive Species /

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

Chamberlin, E. P.; Dragowsky, M.; Fowler, Malcolm M.

2001-01-01

DANCE (Device for Advanced Neutron Capture Experiments) is a 4{pi} 162 element BaF{sub 2} array under development at Los Alamos National Laboratory. It is designed to provide high granularity, fast timing and high photon detection efficiency. It will be located at the Los Alamos Neutron Scattering Center where neutrons are produced using 800 MeV proton induced spallation reactions on heavy element production targets. Using the pulsed high neutron fluence available at this facility combined with time of flight techniques it will be possible to make neutron capture measurements in the neutron energy range from eV to 100's of keV onmore » rare and radioactive target material at the milligram and below level. These measurements will provide critically needed data for the interpretation of the astrophysical s-process 'branching point' nuclei as well as information for reactions needed in understanding transmutation processes of radioactive species.« less

Deformation behavior and spall fracture of the Hadfield steel under shock-wave loading

NASA Astrophysics Data System (ADS)

Gnyusov, S. F.; Rotshtein, V. P.; Polevin, S. D.; Kitsanov, S. A.

2011-03-01

Comparative studies of regularities in plastic deformation and fracture of the Hadfield polycrystalline steel upon quasi-static tension, impact failure, and shock-wave loading with rear spall are performed. The SINUS-7 accelerator was used as a shock-wave generator. The electron beam parameters of the accelerator were the following: maximum electron energy was 1.35 MeV, pulse duration at half-maximum was 45 ns, maximum energy density on a target was 3.4·1010 W/cm2, shock-wave amplitude was ~20 GPa, and strain rate was ~106 s-1. It is established that the failure mechanism changes from ductile transgranular to mixed ductile-brittle intergranular one when going from quasi-static tensile and Charpy impact tests to shock-wave loading. It is demonstrated that a reason for the intergranular spallation is the strain localization near the grain boundaries containing a carbide interlayer.

Shielding and Activation Analyses for BTF Facility at SNS

NASA Astrophysics Data System (ADS)

Popova, Irina; Gallmeier, Franz X.

2017-09-01

The beam test facility (BTF), which simulates front end of the Spallation Neutron Source (SNS), has been built at the SNS, and is preparing for commissioning. The BTF has been assembled and will operate in one of service buildings at the site. The 2.5 MeV proton beam, produced in the facility, will be stopped in the beam dump. In order to support BTF project from radiation protection site, neutronics simulations and activation analyses were performed to evaluate the necessary shielding around the facility and radionuclide inventory of the beam stop.

The very low angle detector for high-energy inelastic neutron scattering on the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

Perelli Cippo, E.; Gorini, G.; Tardocchi, M.; Pietropaolo, A.; Andreani, C.; Senesi, R.; Rhodes, N. J.; Schooneveld, E. M.

2008-05-01

The Very Low Angle Detector (VLAD) bank has been installed on the VESUVIO spectrometer at the ISIS spallation neutron source. The new device allows for high-energy inelastic neutron scattering measurements, at energies above 1 eV, maintaining the wave vector transfer lower than 10Å-1. This opens a still unexplored region of the kinematical (q, ω) space, enabling new and challenging experimental investigations in condensed matter. This paper describes the main instrumental features of the VLAD device, including instrument design, detector response, and calibration procedure.

Note: Versatile sample stick for neutron scattering experiments in high electric fields

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

Bartkowiak, M., E-mail: marek.bartkowiak@psi.ch; White, J. S.; Laboratory for Quantum Magnetism, Ecole Polytechnique Fédérale de Lausanne

2014-02-15

We present a versatile high voltage sample stick that fits into all cryomagnets and standard cryostats at the Swiss Spallation Neutron Source, Paul Scherrer Institut, and which provides a low effort route to neutron scattering experiments that combine electric field with low temperature and magnetic field. The stick allows for voltages up to 5 kV and can be easily adapted for different scattering geometries. We discuss the design consideration and thermal behavior of the stick, and give one example to showcase the abilities of the device.

Two-dimensional beam profiles and one-dimensional projections

NASA Astrophysics Data System (ADS)

Findlay, D. J. S.; Jones, B.; Adams, D. J.

2018-05-01

One-dimensional projections of improved two-dimensional representations of transverse profiles of particle beams are proposed for fitting to data from harp-type monitors measuring beam profiles on particle accelerators. Composite distributions, with tails smoothly matched on to a central (inverted) parabola, are shown to give noticeably better fits than single gaussian and single parabolic distributions to data from harp-type beam profile monitors all along the proton beam transport lines to the two target stations on the ISIS Spallation Neutron Source. Some implications for inferring beam current densities on the beam axis are noted.

Lithium synthesis in microquasar accretion.

PubMed

Iocco, Fabio; Pato, Miguel

2012-07-13

We study the synthesis of lithium isotopes in the hot tori formed around stellar mass black holes by accretion of the companion star. We find that sizable amounts of both stable isotopes 6Li and 7Li can be produced, the exact figures varying with the characteristics of the torus and reaching as much as 10(-2) M⊙ for each isotope. This mass output is enough to contaminate the entire Galaxy at a level comparable with the original, pregalactic amount of lithium and to overcome other sources such as cosmic-ray spallation or stellar nucleosynthesis.

WORKER INHALATION DOSE COEFFICIENTS FOR RADIONUCLIDES NOT PREVIOUSLY IDENTIFIED IN ICRP PUBLICATION 68

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

McLaughlin, David A; Schwahn, Scott O

2011-01-01

While inhalation dose coefficients are provided for about 800 radionuclides in International Commission on Radiological Protection (ICRP) Publication 68, many radionuclides of practical dosimetric interest for facilities such as high-energy proton accelerators are not specifically addressed, nor are organ-specific dose coefficients tabulated. The ICRP Publication 68 methodology is used, along with updated radiological decay data and metabolic data, to identify committed equivalent dose coefficients [hT(50)] and committed effective dose coefficients [e(50)] for radionuclides produced at the Oak Ridge National Laboratory s Spallation Neutron Source.

Phonon characteristics of high {Tc} superconductors from neutron Doppler broadening measurements

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

Trela, W.J.; Kwei, G.H.; Lynn, J.E.

Statistical information on the phonon frequency spectrum of materials can be measured by neutron transmission techniques if they contain nuclei with low energy resonances, narrow enough to be Doppler-broadened, in their neutron cross sections. The authors have carried out some measurements using this technique for materials of the lanthanum barium cuprate class, La{sub 2{minus}x}Ba{sub x}CuO{sub 4}. Two samples with slightly different concentrations of oxygen, one being superconductive, the other not, were examined. Pure lanthanum cuprate was also measured. Lanthanum, barium and copper all have relatively low energy narrow resonances. Thus it should be possible to detect differences in the phononsmore » carried by different kinds of atom in the lattice. Neutron cross section measurements have been made with high energy resolution and statistical precision on the 59m flight path of LANSCE, the pulsed spallation neutron source at Los Alamos National Laboratory. Measurements on all three materials were made over a range of temperatures from 15K to 300K, with small steps through the critical temperature region near 27K. No significant changes in the mean phonon energy of the lanthanum atoms were observed near the critical temperature of the super-conducting material. It appears however that the mean phonon energy of lanthanum in the superconductor is considerably higher than that in the non-superconductors. The samples used in this series of experiments were too thin in barium and copper to determine anything significant about their phonon spectra.« less

Spallation backgrounds in Super-Kamiokande are made in muon-induced showers

NASA Astrophysics Data System (ADS)

Li, Shirley Weishi; Beacom, John F.

2015-05-01

Crucial questions about solar and supernova neutrinos remain unanswered. Super-Kamiokande has the exposure needed for progress, but detector backgrounds are a limiting factor. A leading component is the beta decays of isotopes produced by cosmic-ray muons and their secondaries, which initiate nuclear spallation reactions. Cuts of events after and surrounding muon tracks reduce this spallation decay background by ≃ 90 % (at a cost of ≃ 20 % deadtime), but its rate at 6-18 MeV is still dominant. A better way to cut this background was suggested in a Super-Kamiokande paper by Bays et al. [Phys. Rev. D 85, 052007 (2012)] on a search for the diffuse supernova neutrino background. They found that spallation decays above 16 MeV were preceded near the same location by a peak in the apparent Cherenkov light profile from the muon; a more aggressive cut was applied to a limited section of the muon track, leading to decreased background without increased deadtime. We put their empirical discovery on a firm theoretical foundation. We show that almost all spallation decay isotopes are produced by muon-induced showers and that these showers are rare enough and energetic enough to be identifiable. This is the first such demonstration for any detector. We detail how the physics of showers explains the peak in the muon Cherenkov light profile and other Super-K observations. Our results provide a physical basis for practical improvements in background rejection that will benefit multiple studies. For solar neutrinos, in particular, it should be possible to dramatically reduce backgrounds at energies as low as 6 MeV.

Determination of the Secondary Neutron Flux at the Massive Natural Uranium Spallation Target

NASA Astrophysics Data System (ADS)

Zeman, M.; Adam, J.; Baldin, A. A.; Furman, W. I.; Gustov, S. A.; Katovsky, K.; Khushvaktov, J.; Mar`in, I. I.; Novotny, F.; Solnyshkin, A. A.; Tichy, P.; Tsoupko-Sitnikov, V. M.; Tyutyunnikov, S. I.; Vespalec, R.; Vrzalova, J.; Wagner, V.; Zavorka, L.

The flux of secondary neutrons generated in collisions of the 660 MeV proton beam with the massive natural uranium spallation target was investigated using a set of monoisotopic threshold activation detectors. Sandwiches made of thin high-purity Al, Co, Au, and Bi metal foils were installed in different positions across the whole spallation target. The gamma-ray activity of products of (n,xn) and other studied reactions was measured offline with germanium semiconductor detectors. Reaction yields of radionuclides with half-life exceeding 100 min and with effective neutron energy thresholds between 3.6 MeV and 186 MeV provided us with information about the spectrum of spallation neutrons in this energy region and beyond. The experimental neutron flux was determined using the measured reaction yields and cross-sections calculated with the TALYS 1.8 nuclear reaction program and INCL4-ABLA event generator of MCNP6. Neutron spectra in the region of activation sandwiches were also modeled with the radiation transport code MCNPX 2.7. Neutron flux based on excitation functions from TALYS provides a reasonable description of the neutron spectrum inside the spallation target and is in good agreement with Monte-Carlo predictions. The experimental flux that uses INCL4 cross-sections rather underestimates the modeled spectrum in the whole region of interest, but the agreement within few standard deviations was reached as well. The paper summarizes basic principles of the method for determining the spectrum of high-energy neutrons without employing the spectral adjustment routines and points out to the need for model improvements and precise cross-section measurements.

Pairing-energy coefficients of neutron-rich fragments in spallation reactions

NASA Astrophysics Data System (ADS)

Niu, Fei; Ma, Chun-Wang

2018-02-01

The ratio of pairing-energy coefficient to temperature (a p/T) of neutron-rich fragments produced in spallation reactions has been investigated by adopting an isobaric yield ratio method deduced in the framework of a modified Fisher model. A series of spallation reactions, 0.5A and 1A GeV 208Pb + p, 1A GeV 238U + p, 0.5A GeV 136Xe + d, 0.2A, 0.5A and 1A GeV 136Xe + p, and 56Fe + p with incident energy ranging from 0.3A to 1.5A GeV, has been analysed. An obvious odd-even staggering is shown in the fragments with small neutron excess (I ≡ N-Z), and in the relatively small-A fragments which have large I. The values of a p/T for the fragments, with I from 0 to 36, have been found to be in a range from -4 to 4, and most values of a p/T fall in the range from -1 to 1. It is suggested that a small pairing-energy coefficient should be considered in predicting the cross sections of fragments in spallation reactions. It is also concluded that the method proposed in this article is not good for fragments with A/A s > 85% (where A s is the mass number of the spallation system). Supported by National Natural Science Foundation of China (U1732135), Natural Science Foundation of Henan Province (162300410179) and Henan Normal University for the Excellent Youth (154100510007)

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.

Delayed Alumina Scale Spallation on Rene'n5+y: Moisture Effects and Acoustic Emission

NASA Technical Reports Server (NTRS)

Smialek, James L.; Morscher, Gregory N.

2001-01-01

The single crystal superalloy Rene'N5 (with or without Y-doping and hydrogen annealing) was cyclically oxidized at 1150 C for 1000 hours. After considerable scale growth (>= 500 hours), even the adherent alumina scales formed on Y-doped samples exhibited delayed interfacial spallation during subsequent water immersion tests, performed up to one year after oxidation. Spallation was characterized by weight loss, the amount of spalled area, and acoustic emission response. Hydrogen annealing (prior to oxidation) reduced spallation both before and after immersion, but without measurably reducing the bulk sulfur content of the Y-doped alloys. The duration and frequency of sequential, co-located acoustic emission events implied an interfacial crack growth rate at least 10(exp -3) m/s, but possibly higher than 10(exp 2) m/s. This is much greater than classic moisture-assisted slow crack growth rates in bulk alumina (10(exp -6) to 10(exp -3) m/s), which may still have occurred undetected by acoustic emission. An alternative failure sequence is proposed: an incubation process for preferential moisture ingress leads to a local decrease in interfacial toughness, thus allowing fast fracture driven by stored strain energy.

Kinetics of Cyclic Oxidation and Cracking and Finite Element Analysis of MA956 and Sapphire/MA956 Composite System

NASA Technical Reports Server (NTRS)

Lee, Kang N.; Arya, Vinod K.; Halford, Gary R.; Barrett, Charles A.

1996-01-01

Sapphire fiber-reinforced MA956 composites hold promise for significant weight savings and increased high-temperature structural capability, as compared to unreinforced MA956. As part of an overall assessment of the high-temperature characteristics of this material system, cyclic oxidation behavior was studied at 1093 C and 1204 C. Initially, both sets of coupons exhibited parabolic oxidation kinetics. Later, monolithic MA956 exhibited spallation and a linear weight loss, whereas the composite showed a linear weight gain without spallation. Weight loss of the monolithic MA956 resulted from the linking of a multiplicity of randomly oriented and closely spaced surface cracks that facilitated ready spallation. By contrast, cracking of the composite's oxide layer was nonintersecting and aligned nominally parallel with the orientation of the subsurface reinforcing fibers. Oxidative lifetime of monolithic MA956 was projected from the observed oxidation kinetics. Linear elastic, finite element continuum, and micromechanics analyses were performed on coupons of the monolithic and composite materials. Results of the analyses qualitatively agreed well with the observed oxide cracking and spallation behavior of both the MA956 and the Sapphire/MA956 composite coupons.

Two-photon fluorescence bioimaging with an all-semiconductor laser picosecond pulse source.

PubMed

Kuramoto, Masaru; Kitajima, Nobuyoshi; Guo, Hengchang; Furushima, Yuji; Ikeda, Masao; Yokoyama, Hiroyuki

2007-09-15

We have demonstrated successful two-photon excitation fluorescence bioimaging using a high-power pulsed all-semiconductor laser. Toward this purpose, we developed a pulsed light source consisting of a mode-locked laser diode and a two-stage diode laser amplifier. This pulsed light source provided optical pulses of 5 ps duration and having a maximum peak power of over 100 W at a wavelength of 800 nm and a repetition frequency of 500 MHz.

Accelerator driven neutron source design via beryllium target and 208Pb moderator for boron neutron capture therapy in alternative treatment strategy by Monte Carlo method.

PubMed

Khorshidi, Abdollah

2017-01-01

The reactor has increased its area of application into medicine especially boron neutron capture therapy (BNCT); however, accelerator-driven neutron sources can be used for therapy purposes. The present study aimed to discuss an alternative method in BNCT functions by a small cyclotron with low current protons based on Karaj cyclotron in Iran. An epithermal neutron spectrum generator was simulated with 30 MeV proton energy for BNCT purposes. A low current of 300 μA of the proton beam in spallation target concept via 9Be target was accomplished to model neutron spectrum using 208Pb moderator around the target. The graphite reflector and dual layer collimator were planned to prevent and collimate the neutrons produced from proton interactions. Neutron yield per proton, energy distribution, flux, and dose components in the simulated head phantom were estimated by MCNPX code. The neutron beam quality was investigated by diverse filters thicknesses. The maximum epithermal flux transpired using Fluental, Fe, Li, and Bi filters with thicknesses of 7.4, 3, 0.5, and 4 cm, respectively; as well as the epithermal to thermal neutron flux ratio was 161. Results demonstrated that the induced neutrons from a low energy and low current proton may be effective in tumor therapy using 208Pb moderator with average lethargy and also graphite reflector with low absorption cross section to keep the generated neutrons. Combination of spallation-based BNCT and proton therapy can be especially effective, if a high beam intensity cyclotron becomes available.

The negligible chondritic contribution in the lunar soils water.

PubMed

Stephant, Alice; Robert, François

2014-10-21

Recent data from Apollo samples demonstrate the presence of water in the lunar interior and at the surface, challenging previous assumption that the Moon was free of water. However, the source(s) of this water remains enigmatic. The external flux of particles and solid materials that reach the surface of the airless Moon constitute a hydrogen (H) surface reservoir that can be converted to water (or OH) during proton implantation in rocks or remobilization during magmatic events. Our original goal was thus to quantify the relative contributions to this H surface reservoir. To this end, we report NanoSIMS measurements of D/H and (7)Li/(6)Li ratios on agglutinates, volcanic glasses, and plagioclase grains from the Apollo sample collection. Clear correlations emerge between cosmogenic D and (6)Li revealing that almost all D is produced by spallation reactions both on the surface and in the interior of the grains. In grain interiors, no evidence of chondritic water has been found. This observation allows us to constrain the H isotopic ratio of hypothetical juvenile lunar water to δD ≤ -550‰. On the grain surface, the hydroxyl concentrations are significant and the D/H ratios indicate that they originate from solar wind implantation. The scattering distribution of the data around the theoretical D vs. (6)Li spallation correlation is compatible with a chondritic contribution <15%. In conclusion, (i) solar wind implantation is the major mechanism responsible for hydroxyls on the lunar surface, and (ii) the postulated chondritic lunar water is not retained in the regolith.

Preliminary Evaluation of Cavitation-Erosion Resistance of Ti-Alloys in Mercury for the Spallation Neutron Source

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

Pawel, Steven J; Mansur, Louis K

2010-01-01

A number of Ti-based alloys in both the mill-annealed and 20% cold-worked conditions were subjected to sonication conditions in Hg using a vibratory horn to assess relative cavitation-erosion resistance. Weight loss as a function of exposure time was roughly proportional to hardness for all alloys/conditions examined, with Ti-6Al-4V (Ti-Grade 5) and Ti-6Al-2Sn-4Zr-2Mo yielding the best resistance to cavitation-erosion as evidenced by low weight losses and little or no tendency to form pits on the exposed surface. Unalloyed Ti (Ti-Grade 4) and Ti-0.12Pd (Ti-Grade 7) exhibited greater weight losses by a factor or about two and about five, respectively, with Ti-0.12Pdmore » particularly prone to pitting development. The mean erosion rates of the best two Ti-alloys examined here were about a factor of three higher than identically tested 316LN stainless steel following a low temperature carburizing treatment, but this difference is considered minor given that the rate for both materials is very low/manageable and represents a through-thickness property for the Ti-alloys. A nitriding surface treatment was also evaluated as a potential method to further increase the cavitation-erosion resistance of these alloys in Hg, but the selected treatment proved largely ineffective. Recommendations for further work to evaluate the efficacy of Ti-based alloys for use in high-powered targets for the Spallation Neutron Source are given.« less

An environmental-level, real-time, pulsed photon dosemeter.

PubMed

Olsher, R H; Frymire, A; Gregoire, T

2005-01-01

Radiation sources producing short pulses of photon radiation are widespread. Such sources include electron linear accelerators and field emission impulse generators. It is often desirable to measure leakage and skyshine radiation for these sources in real time and at environmental levels as low as 0.02 microSv per pulse. This note provides an overview of the design and performance of a commercial, real-time, pulsed photon dosemeter (PPD) capable of single-pulse dose measurements over the range from 0.02 to 20 microSv. The PPD may also be operated in a multiple-pulse mode that integrates the dose from a train of pulses over a 3 s period. A pulse repetition rate of up to 300 Hz is accommodated.

Nanosecond pulsed laser welding of high carbon steels

NASA Astrophysics Data System (ADS)

Ascari, Alessandro; Fortunato, Alessandro

2014-03-01

The present paper deals with the possibility to exploit low-cost, near infra-red, nanosecond pulsed laser sources in welding of high carbon content thin sheets. The exploitation of these very common sources allows to achieve sound weld beads with a good depth-to-width ratio and very small heat affected zones when the proper process parameters are involved. In particular the role of pulse frequency, pulse duration, peak power and welding speed on the characteristics of the weld beads is studied and the advantage of the application of short-pulse laser sources over traditional long-pulse or continuous wave one is assessed.

PULSED ION SOURCE

DOEpatents

Kilpatrick, W.D.

1959-04-21

A source is presented for producing high intensity pulses of ions with precise time control of pulse initiation. The approach taken is to have one of the electrodes in the source occluded with the gas to be ionized. A trigger electrode is disposed adjacent to the gas filled electrode and is pulsed with a voltage to release the gas. The other structure of the source includes an apertured anode disposed between two cathodes, the gas filled electrode and another electrode. At the same time the gas is released a low voltage pulse is applied between the anode and cathodes to establish an ionizing arc discharge. An electrode adjacent to the arc withdraws the ions.

Conceptual design of an intense positron source based on an LIA

NASA Astrophysics Data System (ADS)

Long, Ji-Dong; Yang, Zhen; Dong, Pan; Shi, Jin-Shui

2012-04-01

Accelerator based positron sources are widely used due to their high intensity. Most of these accelerators are RF accelerators. An LIA (linear induction accelerator) is a kind of high current pulsed accelerator used for radiography. A conceptual design of an intense pulsed positron source based on an LIA is presented in the paper. One advantage of an LIA is its pulsed power being higher than conventional accelerators, which means a higher amount of primary electrons for positron generations per pulse. Another advantage of an LIA is that it is very suitable to decelerate the positron bunch generated by bremsstrahlung pair process due to its ability to adjustably shape the voltage pulse. By implementing LIA cavities to decelerate the positron bunch before it is moderated, the positron yield could be greatly increased. These features may make the LIA based positron source become a high intensity pulsed positron source.

Hydrocode modeling of the spallation process during hypervelocity impacts: Implications for the ejection of Martian meteorites

NASA Astrophysics Data System (ADS)

Kurosawa, Kosuke; Okamoto, Takaya; Genda, Hidenori

2018-02-01

Hypervelocity ejection of material by impact spallation is considered a plausible mechanism for material exchange between two planetary bodies. We have modeled the spallation process during vertical impacts over a range of impact velocities from 6 to 21 km/s using both grid- and particle-based hydrocode models. The Tillotson equations of state, which are able to treat the nonlinear dependence of density on pressure and thermal pressure in strongly shocked matter, were used to study the hydrodynamic-thermodynamic response after impacts. The effects of material strength and gravitational acceleration were not considered. A two-dimensional time-dependent pressure field within a 1.5-fold projectile radius from the impact point was investigated in cylindrical coordinates to address the generation of spalled material. A resolution test was also performed to reject ejected materials with peak pressures that were too low due to artificial viscosity. The relationship between ejection velocity veject and peak pressure Ppeak was also derived. Our approach shows that "late-stage acceleration" in an ejecta curtain occurs due to the compressible nature of the ejecta, resulting in an ejection velocity that can be higher than the ideal maximum of the resultant particle velocity after passage of a shock wave. We also calculate the ejecta mass that can escape from a planet like Mars (i.e., veject > 5 km/s) that matches the petrographic constraints from Martian meteorites, and which occurs when Ppeak = 30-50 GPa. Although the mass of such ejecta is limited to 0.1-1 wt% of the projectile mass in vertical impacts, this is sufficient for spallation to have been a plausible mechanism for the ejection of Martian meteorites. Finally, we propose that impact spallation is a plausible mechanism for the generation of tektites.

Process technology and effects of spallation products: Circuit components, maintenance, and handling

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

Sigg, B.; Haines, S.J.; Dressler, R.

1996-06-01

Working Session D included an assessment of the status of the technology and components required to: (1) remove impurities from the liquid metal (mercury or Pb-Bi) target flow loop including the effects of spallation products, (2) provide the flow parameters necessary for target operations, and (3) maintain the target system. A series of brief presentations were made to focus the discussion on these issues. The subjects of these presentations, and presenters were: (1) Spallation products and solubilities - R. Dressler; (2) Spallation products for Pb-Bi - Y. Orlov; (3) Clean/up/impurity removal components - B. Sigg; (4) {open_quotes}Road-Map{close_quotes} and remote handlingmore » needs - T. McManamy; (5) Remote handling issues and development - M. Holding. The overall conclusion of this session was that, with the exception of (i) spallation product related processing issues, (ii) helium injection and clean-up, and (iii) specialized remote handling equipment, the technology for all other circuit components (excluding the target itself) exists. Operating systems at the Institute of Physics in Riga, Latvia (O. Lielausis) and at Ben-Gurion University in Beer Shiva, Israel (S. Lesin) have demonstrated that other liquid metal circuit components including pumps, heat exchangers, valves, seals, and piping are readily available and have been reliably used for many years. In the three areas listed above, the designs and analysis are not judged to be mature enough to determine whether and what types of technology development are required. Further design and analysis of the liquid metal target system is therefore needed to define flow circuit processing and remote handling equipment requirements and thereby identify any development needs.« less

Method and apparatus for controlling carrier envelope phase

DOEpatents

Chang, Zenghu [Manhattan, KS; Li, Chengquan [Sunnyvale, CA; Moon, Eric [Manhattan, KS

2011-12-06

A chirped pulse amplification laser system. The system generally comprises a laser source, a pulse modification apparatus including first and second pulse modification elements separated by a separation distance, a positioning element, a measurement device, and a feedback controller. The laser source is operable to generate a laser pulse and the pulse modification apparatus operable to modify at least a portion of the laser pulse. The positioning element is operable to reposition at least a portion of the pulse modification apparatus to vary the separation distance. The measurement device is operable to measure the carrier envelope phase of the generated laser pulse and the feedback controller is operable to control the positioning element based on the measured carrier envelope phase to vary the separation distance of the pulse modification elements and control the carrier envelope phase of laser pulses generated by the laser source.

Uplink transmission of a 60-km-reach WDM/OCDM-PON using a spectrum-sliced pulse source

NASA Astrophysics Data System (ADS)

Choi, Yong-Kyu; Hanawa, Masanori; Park, Chang-Soo

2014-02-01

We propose and experimentally demonstrate the uplink transmission of a 60-km-reach wavelength division multiplexing/optical code division multiplexing (WDM/OCDM) passive optical network (PON) using a spectrum-sliced pulse source. As a single light source, a broadband pulse source with a bandwidth of 6.5 nm and a repetition rate of 1.25 GHz is generated at a central office and supplied to a remote node (RN) through a 50-km fiber link. At the RN, narrow-band pulses (as a source for uplink transmission) are obtained by spectrum slicing the broadband pulse source with a cyclic arrayed waveguide grating and are then supplied to all optical network units (ONUs) via 1×4 power splitters and 10-km drop fibers. Eight wavelengths are obtained with a 6.5-nm bandwidth of the broadband pulse source, and the qualities of the pulses with a repetition rate of 1.25 GHz and a pulse width of 45 ps for the eight wavelengths are sufficient for four-chip OCDM encoding at the ONUs. In our experiments, four signals are multiplexed by OCDM at one wavelength, and another encoded signal is also multiplexed by WDM. The bit error rates (BERs) of the signals exhibit error-free transmission (BER<10-9) over a 60-km single-mode fiber at 1.25 Gb/s.

Ablation of film stacks in solar cell fabrication processes

DOEpatents

Harley, Gabriel; Kim, Taeseok; Cousins, Peter John

2013-04-02

A dielectric film stack of a solar cell is ablated using a laser. The dielectric film stack includes a layer that is absorptive in a wavelength of operation of the laser source. The laser source, which fires laser pulses at a pulse repetition rate, is configured to ablate the film stack to expose an underlying layer of material. The laser source may be configured to fire a burst of two laser pulses or a single temporally asymmetric laser pulse within a single pulse repetition to achieve complete ablation in a single step.

Negative pressure and spallation in graphite targets under nano- and picosecond laser irradiation

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

Belikov, R S; Khishchenko, K V; Krasyuk, I K

We present the results of experiments on the spallation phenomena in graphite targets under shock-wave nano- and picosecond irradiation, which have been performed on Kamerton-T (GPI, Moscow, Russia) and PHELIX (GSI, Darmstadt, Germany) laser facilities. In the range of the strain rates of 10{sup 6} – 10{sup 7} s{sup -1}, the data on the dynamic mechanical strength of the material at rapure (spallation) have been for the first time obtained. With a maximal strain rate of 1.4 × 10{sup 7} s{sup -1}, the spall strength of 2.1 GPa is obtained, which constitutes 64% of the theoretical ultimate tensile strength ofmore » graphite. The effect of spallation is observed not only on the rear side of the target, but also on its irradiated (front) surface. With the use of optical and scanning electron microscopes, the morphology of the front and rear surfaces of the targets is studied. By means of Raman scattering of light, the graphite structure both on the target front surface under laser exposure and on its rear side in the spall zone is investigated. A comparison of the dynamic strength of graphite and synthetic diamond is performed. (extreme light fields and their applications)« less

Validation of Monte Carlo simulation of neutron production in a spallation experiment

DOE PAGES

Zavorka, L.; Adam, J.; Artiushenko, M.; ...

2015-02-25

A renewed interest in experimental research on Accelerator-Driven Systems (ADS) has been initiated by the global attempt to produce energy from thorium as a safe(r), clean(er) and (more) proliferation-resistant alternative to the uranium-fuelled thermal nuclear reactors. The ADS research has been actively pursued at the Joint Institute for Nuclear Research (JINR), Dubna, since decades. Most recently, the emission of fast neutrons was experimentally investigated at the massive (m = 512 kg) natural uranium spallation target QUINTA. The target has been irradiated with the relativistic deuteron beams of energy from 0.5 AGeV up to 4 AGeV at the JINR Nuclotron acceleratormore » in numerous experiments since 2011. Neutron production inside the target was studied through the gamma-ray spectrometry measurement of natural uranium activation detectors. Experimental reaction rates for (n,γ), (n,f) and (n,2n) reactions in uranium have provided valuable information about the neutron distribution over a wide range of energies up to some GeV. The experimental data were compared to the predictions of Monte Carlo simulations using the MCNPX 2.7.0 code. In conclusion, the results are presented and potential sources of partial disagreement are discussed later in this work.« less

Multipacting on the trailing edge of proton beam bunches in the PSR and SNS

NASA Astrophysics Data System (ADS)

Danilov, V.; Aleksandrov, A.; Galambos, J.; Jeon, D.; Holmes, J.; Olsen, D.

1999-12-01

The Proton Storage Ring (PSR) in Los Alamos has a fast intensity-limiting instability, which may result from an electron cloud interaction with the circulating proton beam leading to a transverse mode coupling instability. The most probable mechanism of the electron creation is multipacting. Though the effect depends on many parameters, a model is presented which predicts a large electron creation in the vacuum chamber. A comparison of this effect between the PSR in Los Alamos and the Spallation Neutron Source (SNS) in Oak Ridge is given. In addition, several possibilities to reduce multipactor are discussed.

Evaluation of Side Stream Filtration Technology at Oak Ridge National Laboratory

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

Boyd, Brian K.

2014-08-01

This technology evaluation was performed by Pacific Northwest National Laboratory and Oak Ridge National Laboratory on behalf of the Federal Energy Management Program. The objective was to quantify the benefits side stream filtration provides to a cooling tower system. The evaluation assessed the performance of an existing side stream filtration system at a cooling tower system at Oak Ridge National Laboratory’s Spallation Neutron Source research facility. This location was selected because it offered the opportunity for a side-by-side comparison of a system featuring side stream filtration and an unfiltered system.

Deep inelastic neutron scattering on 207Pb and NaHF 2 as a test of a detectors array on the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

Pietropaolo, A.; Senesi, R.

2008-01-01

A prototype array of resonance detectors for deep inelastic neutron scattering experiments has been installed on the VESUVIO spectrometer, at the ISIS spallation neutron source. Deep inelastic neutron scattering measurements on a reference lead sample and on NaHF 2 molecular system are presented. Despite on an explorative level, the results obtained for the values of mean kinetic energy are found in good agreement with the theoretical predictions, thus assessing the potential capability of the device for a routine use on the instrument.

Status of the NPDGamma experiment

NASA Astrophysics Data System (ADS)

Fry, J.; Alarcon, R.; Allen, R.; Askanazi, E.; Balascuta, S.; Barron-Palos, L.; Baeßler, S.; Barzilov, A.; Blessinger, C.; Blyth, D.; Bowman, J. D.; Calarco, J. R.; Chupp, T. E.; Coppola, C. E.; Crawford, C.; Craycraft, K.; Dabaghyan, M.; Evans, D.; Favela, J.; Fieseler, C.; Fomin, N.; Fox, W.; Freedman, S.; Frlež, E.; Fu, C.; Garcia, C.; Garishvili, I.; Gericke, M. T.; Gillis, R. C.; Grammer, K.; Greene, G. L.; Hamblen, J.; Hayes, C.; Hersman, F. W.; Ino, T.; Iverson, E. B.; Jones, G. L.; Kabir, L.; Kucucker, S.; Lauss, B.; Li, Y.; Mahurin, R.; Maldonado-Velazquez, M.; McCrea, M.; Masuda, Y.; Mei, J.; Milburn, R.; Mitchell, G. S.; Mueller, P.; Muto, S.; Musgrave, M.; Nann, H.; Novikov, I.; Page, S.; Parsons, D.; Počanić, D.; Penttilä, S. I.; Ramsay, W. D.; Salas-Bacci, A.; Santra, S.; Seo, P.-N.; Sharapov, E.; Sharma, M.; Simmons, F.; Smith, T.; Snow, W. M.; Stuart, J.; Tang, E.; Tang, Z.; Thomison, J.; Tong, T.; Vanderwerp, J.; Waldecker, S.; Wilburn, W. S.; Xu, W.; Yuan, V.; Zhang, Y.

2017-11-01

The NPDGamma experiment measures the parity-violating (PV) gamma asymmetry from polarized cold neutrons captured on protons at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The (PV) neutron spin asymmetry A γ of photons from polarized cold neutron capture on protons is proportional to the Δ I=1 long range weak meson coupling h_{π }1 between nucleons in the hadronic weak interaction (HWI). Liquid para-hydrogen production data taking concluded in April 2014 and once the background aluminum asymmetry measurements are complete, the PV asymmetry A γ can be extracted. Preliminary results of the analysis of A γ are presented.

Chamber for mechanical testing in H2 with observation by neutron scattering

NASA Astrophysics Data System (ADS)

Connolly, Matthew; Bradley, Peter; Slifka, Andrew; Drexler, Elizabeth

2017-06-01

A gas-pressure chamber has been designed, constructed, and tested at a moderate pressure (3.4 MPa, 500 psi) and has the capability of mechanical loading of steel specimens for neutron scattering measurements. The chamber will allow a variety of in situ neutron scattering measurements: in particular, diffraction, quasielastic scattering, inelastic scattering, and imaging. The chamber is compatible with load frames available at the user facilities at the NIST Center for Neutron Research and Oak Ridge National Laboratory Spallation Neutron Source. A demonstration of neutron Bragg edge imaging using the chamber is presented.

Study of wave form compensation at CSNS/RCS magnets

NASA Astrophysics Data System (ADS)

Xu, S. Y.; Fu, S. N.; Wang, S.; Kang, W.; Qi, X.; Li, L.; Deng, C. D.; Zhou, J. X.

2018-07-01

A method of wave form compensation for magnets of the Rapid Cycling Synchrotron (RCS), which is based on transfer function between magnetic field and exciting current, was investigated on the magnets of RCS of Chinese Spallation Neutron Source (CSNS). By performing wave form compensation, the magnetic field ramping function for RCS magnets can be accurately controlled to the given wave form, which is not limited to sine function. The method of wave form compensation introduced in this paper can be used to reduce the magnetic field tracking errors, and can also be used to accurately control the betatron tune for RCS.

INCREASED UNDERSTANDING OF BEAM LOSSES FROM THE SNS LINAC PROTON EXPERIMENT

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

Aleksandrov, Alexander V; Shishlo, Andrei P; Plum, Michael A

Beam loss is a major concern for high power hadron accelerators such as the Spallation Neutron Source (SNS). An unexpected beam loss in the SNS superconducting linac (SCL) was observed during the power ramp up and early operation. Intra-beam-stripping (IBS) loss, in which interactions between H- particles within the accelerated bunch strip the outermost electron, was recently identified as a possible cause of the beam loss. A set of experiments using proton beam acceleration in the SNS linac was conducted, which supports IBS as the primary beam loss mechanism in the SNS SCL.

A real-time pulsed photon dosimeter

NASA Astrophysics Data System (ADS)

Brown, David; Olsher, Richard H.; Eisen, Yosef; Rodriguez, Joseph F.

1996-02-01

Radiation sources producing short pulses of photon radiation are now widespread. Such sources include electron and proton linear accelerators, betatrons, synchrotrons, and field-emission impulse generators. It is often desirable to measure leakage and skyshine radiation from such sources in real time, on a single-pulse basis as low as 8.7 nGy (1 μR) per pulse. This paper describes the design and performance of a prototype, real-time, pulsed photon dosimeter (PPD) capable of single-pulse dose measurements over the range from 3.5 nGy to 3.5 μGy (0.4 to 400 μR). The PPD may also be operated in a multiple-pulse mode that integrates the dose from a train of radiation pulses over a 3-s period. A pulse repetition rate of up to 300 Hz is accommodated. The design is eminently suitable for packaging as a lightweight, portable, survey meter. The PPD uses a CdWO 4 scintillator optically coupled to a photodiode to generate a charge at the diode output. A pulse amplifier converts the charge to a voltage pulse. A digitizer circuit generates a burst of logic pulses whose number is proportional to the peak value of the voltage pulse. The digitizer output is recorded by a pulse counter and suitably displayed. A prototype PPD was built for testing and evaluation purposes. The performance of the PPD was evaluated with a variety of pulsed photon sources. The dynamic range, energy response, and response to multiple pulses were characterized. The experimental data confirm the viability of the PPD for pulsed photon dosimetry.

Towards higher stability of resonant absorption measurements in pulsed plasmas.

PubMed

Britun, Nikolay; Michiels, Matthieu; Snyders, Rony

2015-12-01

Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called "dynamic source triggering," between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source.

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.

Los Alamos nEDM Experiment and Demonstration of Ramsey's Method on Stored UCNs at the LANL UCN Source

NASA Astrophysics Data System (ADS)

Clayton, Steven; Chupp, Tim; Cude-Woods, Christopher; Currie, Scott; Ito, Takeyasu; Liu, Chen-Yu; Long, Joshua; MacDonald, Stephen; Makela, Mark; O'Shaughnessy, Christopher; Plaster, Brad; Ramsey, John; Saunders, Andy; LANL nEDM Collaboration

2017-09-01

The Los Alamos National Laboratory ultracold neutron (UCN) source was recently upgraded for a factor of 5 improvement in stored density, providing the statistical precision needed for a room temperature neutron electric dipole moment measurement with sensitivity 3 ×10-27 e . cm, a factor 10 better than the limit set by the Sussex-RAL-ILL experiment. Here, we show results of a demonstration of Ramsey's separated oscillatory fields method on stored UCNs at the LANL UCN source and in a geometry relevant for a nEDM measurement. We argue a world-leading nEDM experiment could be performed at LANL with existing technology and a short lead time, providing a physics result with sensitivity intermediate between the current limit set by Sussex-RAL-ILL, and the anticipated limit from the complex, cryogenic nEDM experiment planned for the next decade at the ORNL Spallation Neutron Source (SNS-nEDM). This work was supported by the Los Alamos LDRD Program, Project 20140015DR.

Single-shot, high-resolution, fiber-based phase-diversity photodetection of optical pulses

NASA Astrophysics Data System (ADS)

Dorrer, C.; Waxer, L. J.; Kalb, A.; Hill, E. M.; Bromage, J.

2016-03-01

Temporally characterizing optical pulses is an important task when building, optimizing, and using optical sources. Direct photodetection with high-bandwidth photodiodes and real-time oscilloscopes is only adequate for optical pulses longer than ~10 ps; diagnostics based on indirect strategies are required to characterize femtosecond and sub-10-ps coherent sources. Most of these diagnostics are based on nonlinear optics and can be difficult to implement for the single-shot characterization of nonrepetitive events. A temporal diagnostic based on phase diversity is demonstrated in the context of picosecond high-energy laser systems, where single-shot pulse measurements are required for system safety and interpretation of experimental results. A plurality of ancillary optical pulses obtained by adding known amounts of chromatic dispersion to the pulse under test are directly measured by photodetection and processed to reconstruct the input pulse shape. This high-sensitivity (~50-pJ) diagnostic is based on a pulse replicator composed of fiber splitters and delay fibers, making it possible to operate with fiber sources and free-space sources after fiber coupling. Experimental data obtained with a high-bandwidth real-time oscilloscope demonstrate accurate characterization of pulses from a high-energy chirped-pulse amplification system, even for pulses shorter than the photodetection impulse response.

Analysis of radiation environmental safety for China's Spallation Neutron Source (CSNS)

NASA Astrophysics Data System (ADS)

Wang, Qing-Bin; Wu, Qing-Biao; Ma, Zhong-Jian; Zhang, Qing-Jiang; Li, Nan; Wu, Jing-Min; Liu, Jian; Zhang, Gang

2010-07-01

The China Spallation Neutron Source (CSNS) is going to be located in Dalang Town, Dongguan City in the Guangdong Province. In this paper we report the results of the parameters related with environment safety based on experiential calculations and Monte Carlo simulations. The main project of the accelerator is an under ground construction. On top there is a 0.5 m concrete and 5.0 m soil covering for shielding, which can reduce the dose out of the tunnel's top down to 0.2 μSv/h. For the residents on the boundary of the CSNS, the dose produced by skyshine, which is caused by the penetrated radiation leaking from the top of the accelerator, is no more than 0.68 μSv/a. When CSNS is operating normally, the maximal annual effective dose due to the emission of gas from the tunnel is 2.40×10-3 mSv/a to the public adult, and 2.29×10-3 mSv/a to a child, both values are two orders of magnitude less than the limiting value for control and management. CSNS may give rise to an activation of the soil and groundwater in the nearest tunnels, where the main productions are 3H, 7Be, 22Na, 54Mn, etc. But the specific activity is less than the exempt specific activity in the national standard GB13376-92. So it is safe to say that the environmental impact caused by the activation of soil and groundwater is insignificant. To sum up, for CSNS, as a powerful neutron source device, driven by a high-energy high-current proton accelerator, a lot of potential factors affecting the environment exist. However, as long as effective shieldings for protection are adopted and strict rules are drafted, the environmental impact can be kept under control within the limits of the national standard.

Compact sub-nanosecond pulse seed source with diode laser driven by a high-speed circuit

NASA Astrophysics Data System (ADS)

Wang, Xiaoqian; Wang, Bo; Wang, Junhua; Cheng, Wenyong

2018-06-01

A compact sub-nanosecond pulse seed source with 1550 nm diode laser (DL) was obtained by employing a high-speed circuit. The circuit mainly consisted of a short pulse generator and a short pulse driver. The short pulse generator, making up of a complex programmable logic device (CPLD), a level translator, two programmable delay chips and an AND gate chip, output a triggering signal to control metal-oxide-semiconductor field-effect transistor (MOSFET) switch of the short pulse driver. The MOSFET switch with fast rising time and falling time both shorter than 1 ns drove the DL to emit short optical pulses. Performances of the pulse seed source were tested. The results showed that continuously adjustable repetition frequency ranging from 500 kHz to 100 MHz and pulse duration in the range of 538 ps to 10 ns were obtained, respectively. 537 μW output was obtained at the highest repetition frequency of 100 MHz with the shortest pulse duration of 538 ps. These seed pulses were injected into an fiber amplifier, and no optical pulse distortions were found.

Spallation and fracture resulting from reflected and intersecting stress waves.

NASA Technical Reports Server (NTRS)

Kinslow, R.

1973-01-01

Discussion of the effects of stress waves produced in solid by explosions or high-velocity impacts. These waves rebound from free surfaces in the form of tensile waves that are capable of causing internal fractures or spallation of the material. The high-speed framing camera is shown to be an important tool for observing the stress waves and fracture in transparent targets, and its photographs provide valuable information on the mechanics of fracture.

Record productions establish RF-driven sources as the standard for generating high-duty-factor, high-current H- beams for accelerators (Winner of the ICIS 2017 Brightness Award)

NASA Astrophysics Data System (ADS)

Stockli, Martin P.; Welton, Robert F.; Han, Baoxi

2018-05-01

The Spallation Neutron Source operates reliably at 1.2 MW and will gradually ramp to 1.4 MW. This paper briefly recalls some of the struggles when the unprecedented project was started and ramped to 1 MW over a 3½ year period. This was challenging, especially for the H- ion source and the low-energy beam transport system, which make up the H- injector. It took several more years to push the H- injector to the 1.4 MW requirements, and even longer to reach close to 100% injector availability. An additional breakthrough was the carefully staged, successful extension of the H- source service cycle so that disruptive source changes became rare events. More than 7 A.h of extracted H- ions have been demonstrated with a single source without maintenance, more than twice the single-source quantity of ions produced by any other high-current H- accelerator facility. Achieving the 1.4 MW requirements with close to 100% availability and record-breaking source service cycles were the basis for the 2017 Brightness Award.

[Microsecond Pulsed Hollow Cathode Lamp as Enhanced Excitation Source of Hydride Generation Atomic Fluorescence Spectrometry].

PubMed

Zhang, Shuo

2015-09-01

The spectral, electrical and atomic fluorescence characteristics of As, Se, Sb and Pb hollow cathode lamps (HCLs) powered by a laboratory-built high current microsecond pulse (HCMP) power supply were studied, and the feasibility of using HCMP-HCLs as the excitation source of hydride generation atomic fluorescence spectrometry (HG-AFS) was evaluated. Under the HCMP power supply mode, the As, Se, Sb, Pb HCLs can maintain stable glow discharge at frequency of 100~1000 Hz, pulse width of 4.0~20 μs and pulse current up to 4.0 A. Relationship between the intensity of characteristic emission lines and HCMP power supply parameters, such as pulse current, power supply voltage, pulse width and frequency, was studied in detail. Compared with the conventional pulsed (CP) HCLs used in commercial AFS instruments, HCMP-HCLs have a narrower pulse width and much stronger pulse current. Under the optimized HCMP power supply parameters, the intensity of atomic emission lines of As, Se, Sb HCLs had sharp enhancement and that indicated their capacity of being a novel HG-AFS excitation source. However, the attenuation of atomic lines and enhancement of ionic lines negated such feasibility of HCMP-Pb HCL. Then the HG-AFS analytical capability of using the HCMP-As/Se/Sb HCLs excitation source was established and results showed that the HCMP-HCL is a promising excitation source for HG-AFS.

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

MULTI-CHANNEL ELECTRIC PULSE HEIGHT ANALYZER

DOEpatents

Gallagher, J.D. et al.

1960-11-22

An apparatus is given for converting binary information into coded decimal form comprising means, in combination with a binary adder, a live memory and a source of bigit pulses, for synchronizing the bigit pulses and the adder output pulses; a source of digit pulses synchronized with every fourth bigit pulse; means for generating a conversion pulse in response to the time coincidence of the adder output pulse and a digit pulse: means having a delay equal to two bigit pulse periods coupling the adder output with the memory; means for promptly impressing said conversion pulse on the input of said memory: and means having a delay equal to one bigit pulse period for again impressing the conversion pulse on the input of the memory whereby a fourth bigit adder pulse results in the insertion into the memory of second, third and fourth bigits.

Effects of environment and frequency on the fatigue behavior of the spallation neutron source (SNS) target container material - 316 LN stainless steel

NASA Astrophysics Data System (ADS)

Tian, Hongbo

As the candidate target container material of the new Spallation Neutron Source (SNS) being designed and constructed at the Oak Ridge National Laboratory (ORNL), Type 316 low-carbon nitrogen-added (LN) stainless steel (SS) will operate in an aggressive environment, subjected to intense fluxes of high-energy protons and neutrons while exposed to liquid mercury. The current project is oriented toward materials studies regarding the effects of test environment and frequency on the fatigue behavior of 316 LN SS. In order to study the structural applications of this material and improve the fundamental understanding of the fatigue damage mechanisms, fatigue tests were performed in air and mercury environments at various frequencies and R ratios (R = sigma min/sigmamax, sigmamin and sigmamax are the applied minimum and maximum stresses, respectively). Fatigue data were developed for the structural design and engineering applications of this material. Specifically, high-cycle fatigue tests, fatigue crack-propagation tests, and ultrahigh cycle fatigue tests up to 10 9 cycles were conducted in air and mercury with test frequencies from 10 Hz to 700 Hz. Microstructure characterizations were performed using optical microscopy (OM), scanning-electron microscopy (SEM), and transmission-electron microscopy (TEM). It was found that mercury doesn't seem to have a large impact on the crack-initiation behavior of 316 LN SS. However, the crack-propagation mechanisms in air and mercury are different in some test conditions. Transgranular cracks seem to be the main mechanism in air, and intergranular in mercury. A significant specimen self-heating effect was found during high-cycle faituge. Theoretical calculation was performed to predict temperature responses of the material subjected to cyclic deformation. The predicted cyclic temperature evolution seems to be in good agreement with the experimental results.

Analysis of structure and deformation behavior of AISI 316L tensile specimens from the second operational target module at the Spallation Neutron Source

DOE PAGES

Gussev, Maxim N.; McClintock, David A.; Garner, Frank

2015-08-05

In an earlier publication, tensile testing was performed on specimens removed from the first two operational targets of the Spallation Neutron Source (SNS). There were several anomalous features in the results. First, some specimens had very large elongations (up to 57%) while others had significantly smaller values. Second, there was a larger than the usual amount of data scatter in the elongation results. Third, the stress-strain diagrams of nominally similar specimens spanned a wide range of behavior ranging from expected irradiation-induced hardening to varying levels of force drop after yield point and indirect signs of "traveling deformation wave" behavior associatedmore » with strain-induced martensite formation. To investigate the cause(s) of such variable tensile behavior, several specimens from Target 2, spanning the range of observed tensile behavior, were chosen for detailed microstructural examination using electron backscattering analysis (EBSD). It was also shown that the steel employed in the construction of the target contained an unexpected bimodal grain size distribution, containing very large out-of-specification grains surrounded by necklaces of grains of within-specification sizes. The large grains were frequently comparable to the width of the gauge section of the tensile specimen. Moreover, the propensity to form martensite during deformation was shown to be accelerated by radiation but also to be very sensitive to the relative orientation of the grains with respect to the tensile axis. Specimens having large grains in the gauge that were most favorably oriented for production of martensite strongly exhibited the traveling deformation wave phenomenon, while those specimens with less favorably oriented grains had lesser or no degree of the wave effect, thereby accounting for the larger than expected data scatter.« less

SINGLE EVENT EFFECTS TEST FACILITY AT OAK RIDGE NATIONAL LABORATORY

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

Riemer, Bernie; Gallmeier, Franz X; Dominik, Laura J

2015-01-01

Increasing use of microelectronics of ever diminishing feature size in avionics systems has led to a growing Single Event Effects (SEE) susceptibility arising from the highly ionizing interactions of cosmic rays and solar particles. Single event effects caused by atmospheric radiation have been recognized in recent years as a design issue for avionics equipment and systems. To ensure a system meets all its safety and reliability requirements, SEE induced upsets and potential system failures need to be considered, including testing of the components and systems in a neutron beam. Testing of ICs and systems for use in radiation environments requiresmore » the utilization of highly advanced laboratory facilities that can run evaluations on microcircuits for the effects of radiation. This paper provides a background of the atmospheric radiation phenomenon and the resulting single event effects, including single event upset (SEU) and latch up conditions. A study investigating requirements for future single event effect irradiation test facilities and developing options at the Spallation Neutron Source (SNS) is summarized. The relatively new SNS with its 1.0 GeV proton beam, typical operation of 5000 h per year, expertise in spallation neutron sources, user program infrastructure, and decades of useful life ahead is well suited for hosting a world-class SEE test facility in North America. Emphasis was put on testing of large avionics systems while still providing tunable high flux irradiation conditions for component tests. Makers of ground-based systems would also be served well by these facilities. Three options are described; the most capable, flexible, and highest-test-capacity option is a new stand-alone target station using about one kW of proton beam power on a gas-cooled tungsten target, with dual test enclosures. Less expensive options are also described.« less

Single Event Effects Test Facility Options at the Oak Ridge National Laboratory

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

Riemer, Bernie; Gallmeier, Franz X; Dominik, Laura J

2015-01-01

Increasing use of microelectronics of ever diminishing feature size in avionics systems has led to a growing Single Event Effects (SEE) susceptibility arising from the highly ionizing interactions of cosmic rays and solar particles. Single event effects caused by atmospheric radiation have been recognized in recent years as a design issue for avionics equipment and systems. To ensure a system meets all its safety and reliability requirements, SEE induced upsets and potential system failures need to be considered, including testing of the components and systems in a neutron beam. Testing of integrated circuits (ICs) and systems for use in radiationmore » environments requires the utilization of highly advanced laboratory facilities that can run evaluations on microcircuits for the effects of radiation. This paper provides a background of the atmospheric radiation phenomenon and the resulting single event effects, including single event upset (SEU) and latch up conditions. A study investigating requirements for future single event effect irradiation test facilities and developing options at the Spallation Neutron Source (SNS) is summarized. The relatively new SNS with its 1.0 GeV proton beam, typical operation of 5000 h per year, expertise in spallation neutron sources, user program infrastructure, and decades of useful life ahead is well suited for hosting a world-class SEE test facility in North America. Emphasis was put on testing of large avionics systems while still providing tunable high flux irradiation conditions for component tests. Makers of ground-based systems would also be served well by these facilities. Three options are described; the most capable, flexible, and highest-test-capacity option is a new stand-alone target station using about one kW of proton beam power on a gas-cooled tungsten target, with dual test enclosures. Less expensive options are also described.« less

Helium Bubble Injection Solution To The Cavitation Damage At The Spallation Neutron Source

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

Francis, M. W.; Ruggles, A. E.

2009-03-10

The Spallation Neutron Source (SNS) is one of the largest science projects in the United States, with total cost near 1.4 Billion Dollars. The limiting factor of the facility had always been assumed to be the lifetime of the target window due to radiation damage. After further investigation, the lifetime of the target was determined not to be limited by radiation damage but by cavitation damage. The cavitation damage derives from pressure waves caused by the beam energy deposition. Vapor bubbles form when low to negative pressures occur in the mercury near the stainless steel target window due to wavemore » interaction with the structure. Collapse of these bubbles can focus wave energy in small liquid jets that erode the window surface. Compressibility of the mercury can be enhanced to reduce the amplitude of the pressure wave caused by the beam energy deposition. To enhance compressibility, small (10 to 30 micron diameter) gas bubbles could be injected into the bulk of the mercury. Solubility and diffusivity parameters of inert gas in mercury are required for a complete mechanical simulation and engineering of these strategies. Using current theoretical models, one obtains a theoretical Henry coefficient of helium in mercury on the order of 3.9E15 Pa-molHg/molHe at 300 K. This low solubility was confirmed by a direct, offline experimental method. Mercury was charged with helium and any pressure change was recorded. Any pressure change was attributed to gas going into solution. Therefore, with the sensitivity of the experiment, a lower limit of 9E12 Pa-molHg/molHe was placed on the mercury-helium system. These values guarantee a stable bubble lifetime needed within the SNS mercury target to mitigate cavitation issues.« less

Correlation between simulations and cavitation-induced erosion damage in Spallation Neutron Source target modules after operation

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

Riemer, Bernie; McClintock, David A; Kaminskas, Saulius

2014-01-01

An explicit finite element (FE) technique developed for estimating dynamic strain in the Spallation Neutron Source (SNS) mercury target module vessel is now providing insight into cavitation damage patterns observed in used targets. The technique uses an empirically developed material model for the mercury that describes liquid-like volumetric stiffness combined with a tensile pressure cut-off limit that approximates cavitation. The longest period each point in the mercury is at the tensile cut-off threshold is denoted its saturation time. Now, the pattern of saturation time can be obtained from these simulations and is being positively correlated with observed damage patterns andmore » is interpreted as a qualitative measure of damage potential. Saturation time has been advocated by collaborators at J-Parc as a factor in predicting bubble nuclei growth and collapse intensity. The larger the ratio of maximum bubble size to nucleus, the greater the bubble collapse intensity to be expected; longer saturation times result in greater ratios. With the recent development of a user subroutine for the FE solver saturation time is now provided over the entire mercury domain. Its pattern agrees with spots of damage seen above and below the beam axis on the SNS inner vessel beam window and elsewhere. The other simulation result being compared to observed damage patterns is mercury velocity at the wall. Related R&D has provided evidence for the damage mitigation that higher wall velocity provides. In comparison to observations in SNS targets, inverse correlation of high velocity to damage is seen. In effect, it is the combination of the patterns of saturation time and low velocity that seems to match actual damage patterns.« less

HERSCHEL FINDS EVIDENCE FOR STELLAR WIND PARTICLES IN A PROTOSTELLAR ENVELOPE: IS THIS WHAT HAPPENED TO THE YOUNG SUN?

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

Ceccarelli, C.; López-Sepulcre, A.; Dominik, C.

2014-07-20

There is evidence that the young Sun emitted a high flux of energetic (≥10 MeV) particles. The collisions of these particles with the material at the inner edge of the Protosolar Nebula disk induced spallation reactions that formed short-lived radionuclei, like {sup 10}Be, whose trace is now visible in some meteorites. However, it is poorly known exactly when this happened, and whether and how it affected the solar system. Here, we present indirect evidence for an ejection of energetic particles in the young protostar, OMC-2 FIR 4, similar to that experienced by the young solar system. In this case, the energeticmore » particles collide with the material in the protostellar envelope, enhancing the abundance of two molecular ions, HCO{sup +} and N{sub 2}H{sup +}, whose presence is detected via Herschel observations. The flux of energetic particles at a distance of 1 AU from the emitting source, estimated from the measured abundance ratio of HCO{sup +} and N{sub 2}H{sup +}, can easily account for the irradiation required by meteoritic observations. These new observations demonstrate that the ejection of ≥10 MeV particles is a phenomenon occurring very early in the life of a protostar, before the disappearance of the envelope from which the future star accretes. The whole envelope is affected by the event, which sets constraints on the magnetic field geometry in the source and opens up the possibility that the spallation reactions are not limited to the inner edge of the Protosolar Nebula disk.« less

Fast pulsed operation of a small non-radioactive electron source with continuous emission current control

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

Cochems, P.; Kirk, A. T.; Bunert, E.

Non-radioactive electron sources are of great interest in any application requiring the emission of electrons at atmospheric pressure, as they offer better control over emission parameters than radioactive electron sources and are not subject to legal restrictions. Recently, we published a simple electron source consisting only of a vacuum housing, a filament, and a single control grid. In this paper, we present improved control electronics that utilize this control grid in order to focus and defocus the electron beam, thus pulsing the electron emission at atmospheric pressure. This allows short emission pulses and excellent stability of the emitted electron currentmore » due to continuous control, both during pulsed and continuous operations. As an application example, this electron source is coupled to an ion mobility spectrometer. Here, the pulsed electron source allows experiments on gas phase ion chemistry (e.g., ion generation and recombination kinetics) and can even remove the need for a traditional ion shutter.« less

Simulation of spallation life of metals in relation to operating stresses in the nanosecond loading time range

NASA Astrophysics Data System (ADS)

Makarov, P. V.; Bakeev, R. A.

2015-10-01

Spall fracture of materials is still the only means for investigation of the material life and mechanisms of its fracture in the micro-, nano-, and picosecond time ranges of tensile loading. The phenomenological model based on the concepts of multiscale fracture of materials as nonlinear dynamic systems is shown to satisfactorily describe their life in the given range. The model is employed for the calculation of spallation life.

Chemical isolation of .sup.82 Sr from proton-irradiated Mo targets

DOEpatents

Grant, Patrick M.; Kahn, Milton; O'Brien, Jr., Harold A.

1976-01-01

Spallation reactions are induced in Mo targets with 200-800 MeV protons to produce microcurie to millicurie amounts of a variety of radionuclides. A six-step radiochemical procedure, incorporating precipitation, solvent extractions, and ion exchange techniques, has been developed for the separation and purification of Sr radioactivities from other spallation products and the bulk target material. Radiostrontium can be quantitatively recovered in a sufficiently decontaminated state for use in biomedical generator development.

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 .

A Survey of Students from the National School on Neutron and X-ray Scattering: Communication Habits and Preferences

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

Bryant, Rebecca

2010-12-01

Oak Ridge National Laboratory (ORNL) offers the scientific community unique access to two types of world-class neutron sources at a single site - the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR). The 85-MW HFIR provides one of the highest steady-state neutron fluxes of any research reactor in the world. And the SNS is one of the world's most intense pulse neutron beams. Management of these resources is the responsibility of the Neutron Sciences Directorate (NScD). NScD started conducting the National School on Neutron and X-ray Scattering (NXS) in conjunction with the Advanced Photon Source (APS) atmore » Argonne National Laboratory in 2007. This survey was conducted to determine the most effective ways to reach students with information about what SNS and HFIR offer the scientific community, including content and communication vehicles. The emphasis is on gaining insights into compelling messages and the most effective channels, e.g., Web sites and social media, for communicating with students about neutron science The survey was conducted in two phases using a classic qualitative investigation to confirm language and content followed by a survey designed to quantify issues, assumptions, and working hypotheses. Phase I consisted of a focus group in late June 2010 with students attending NXS. The primary intent of the group was to inform development of an online survey. Phase two consisted of an online survey that was developed and pre-tested in July 2010 and launched on August 9, 2010 and remained in the field until September 9, 2010. The survey achieved an overall response rate of 48% for a total of 157 completions. The objective of this study is to determine the most effective ways to reach students with information about what SNS and HFIR offer the scientific community, including content and communication vehicles. The emphasis is on gaining insights into compelling messages and the most effective channels, e.g., Web sites, social media, for communicating with students about neutron science.« less

Pulse-to-pulse variations in accreting X-ray pulsars

NASA Astrophysics Data System (ADS)

Kretschmar, Peter; Marcu, Diana; Kühnel, Matthias; Klochkov, Dmitry; Pottschmidt, Katja; Staubert, Rüdiger; Wilson-Hodge, Colleen A.; Jenke, Peter A.; Caballero, Isabel; Fürst, Felix

2014-01-01

In most accreting X-ray pulsars, the periodic signal is very clear and easily shows up as soon as data covering sufficient pulse periods (a few ten) are available. The mean pulse profile is often quite typical for a given source and with minor variations repeated and recognisable across observations done years or even decades apart. At the time scale of individual pulses, significant pulse-to-pulse variations are commonly observed. While at low energies some of these variations might be explained by absorption, in the hard X-rays they will reflect changes in the accretion and subsequent emission. The amount of these variations appears to be quite different between sources and contains information about the surrounding material as well ass possibly interactions at the magnetosphere. We investigate such variations for a sample of well-known sources.

Fiber Bragg grating Fabry-Perot cavity sensor based on pulse laser demodulation technique

NASA Astrophysics Data System (ADS)

Gao, Fangfang; Chen, Jianfeng; Liu, Yunqi; Wang, Tingyun

2011-12-01

We demonstrate a fiber laser sensing technique based on fiber Bragg grating Fabry-Perot (FBG-FP) cavity interrogated by pulsed laser, where short pulses generated from active mode-locked erbium-doped fiber ring laser and current modulated DFB laser are adopted. The modulated laser pulses launched into the FBG-FP cavity produce a group of reflected pulses. The optical loss in the cavity can be determined from the power ratio of the first two pulses reflected from the cavity. This technique does not require high reflectivity FBGs and is immune to the power fluctuation of the light source. Two short pulse laser sources were compared experimentally with each other on pulse width, pulse stability, pulse chirp and sensing efficiency.

Scattering-type scanning near-field optical microscopy with low-repetition-rate pulsed light source through phase-domain sampling

PubMed Central

Wang, Haomin; Wang, Le; Xu, Xiaoji G.

2016-01-01

Scattering-type scanning near-field optical microscopy (s-SNOM) allows spectroscopic imaging with spatial resolution below the diffraction limit. With suitable light sources, s-SNOM is instrumental in numerous discoveries at the nanoscale. So far, the light sources have been limited to continuous wave or high-repetition-rate pulsed lasers. Low-repetition-rate pulsed sources cannot be used, due to the limitation of the lock-in detection mechanism that is required for current s-SNOM techniques. Here, we report a near-field signal extraction method that enables low-repetition-rate pulsed light sources. The method correlates scattering signals from pulses with the mechanical phases of the oscillating s-SNOM probe to obtain near-field signal, by-passing the apparent restriction imposed by the Nyquist–Shannon sampling theorem on the repetition rate. The method shall enable s-SNOM with low-repetition-rate pulses with high-peak-powers, such as femtosecond laser amplifiers, to facilitate investigations of strong light–matter interactions and nonlinear processes at the nanoscale. PMID:27748360

Decommissioning and PIE of the MEGAPIE spallation target

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

Latge, C.; Henry, J.; Wohlmuther, M.

2013-07-01

A key experiment in the Accelerated Driven Systems roadmap, the MEGAwatt PIlot Experiment (MEGAPIE) (1 MW) was initiated in 1999 in order to design and build a liquid lead-bismuth spallation target, then to operate it into the Swiss spallation neutron facility SINQ at Paul Scherrer Institute. The target has been designed, manufactured, and tested during integral tests, before irradiation carried out end of 2006. During irradiation, neutron and thermo hydraulic measurements were performed allowing deep interpretation of the experiment and validation of the models used during design phase. The decommissioning, Post Irradiation Examinations and waste management phases were defined properly.more » The phases dedicated to cutting, sampling, cleaning, waste management, samples preparation and shipping to various laboratories were performed by PSI teams: all these phases constitute a huge work, which allows now to perform post-irradiation examination (PIE) of structural material, irradiated in relevant conditions. Preliminary results are presented in the paper, they concern chemical characterization. The following radio-nuclides have been identified by γ-spectrometry: {sup 60}Co, {sup 101}Rh, {sup 102}Rh, {sup 108m}Ag, {sup 110m}Ag, {sup 133}Ba, {sup 172}Hf/Lu, {sup 173}Lu, {sup 194}Hg/Au, {sup 195}Au, {sup 207}Bi. For some of these nuclides the activities can be easily evaluated from γ-spectrometry results ({sup 207}Bi, {sup 194}Hg/Au), while other nuclides can only be determined after chemical separations ({sup 108m}Ag, {sup 110m}Ag, {sup 195}Au, {sup 129}I, {sup 36}Cl and α-emitting {sup 208-210}Po). The concentration of {sup 129}I is lower than expected. The chemical analysis already performed on spallation and corrosion products in the lead-bismuth eutectic (LBE) are very relevant for further applications of LBE as a spallation media and more generally as a coolant.« less

Windows(Registered Trademark)-Based Software Models Cyclic Oxidation Behavior

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Auping, J. V.

2004-01-01

Oxidation of high-temperature aerospace materials is a universal issue for combustion-path components in turbine or rocket engines. In addition to the question of the consumption of material due to growth of protective scale at use temperatures, there is also the question of cyclic effects and spallation of scale on cooldown. The spallation results in the removal of part of the protective oxide in a discontinuous step and thereby opens the way for more rapid oxidation upon reheating. In experiments, cyclic oxidation behavior is most commonly characterized by measuring changes in weight during extended time intervals that include hundreds or thousands of heating and cooling cycles. Weight gains occurring during isothermal scale-growth processes have been well characterized as being parabolic or nearly parabolic functions of time because diffusion controls reaction rates. In contrast, the net weight change in cyclic oxidation is the sum of the effects of the growth and spallation of scale. Typically, the net weight gain in cyclic oxidation is determined only empirically (that is, by measurement), with no unique or straightforward mathematical connection to either the rate of growth or the amount of metal consumed. Thus, there is a need for mathematical modeling to infer spallation mechanisms. COSP is a computer program that models the growth and spallation processes of cyclic oxidation on the basis of a few elementary assumptions that were discussed in COSP: A Computer Model of Cyclic Oxidation, Oxidation of Metals, vol. 36, numbers 1 and 2, 1991, pages 81-112. Inputs to the model include the selection of an oxidation-growth law and a spalling geometry, plus oxide-phase, growth-rate, cycle-duration, and spall-constant parameters. (The spalling fraction is often shown to be a constant factor times the existing amount of scale.) The output of COSP includes the net change in weight, the amounts of retained and spalled oxide, the total amounts of oxygen and metal consumed, and the terminal rates of weight loss and metal consumption.

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)

Radiological Aspects of Heavy Metal Liquid Targets for Accelerator-Driven Systems as Intense Neutron Sources

NASA Astrophysics Data System (ADS)

Gai, E. V.; Ignatyuk, A. V.; Lunev, V. P.; Shubin, Yu. N.

2001-11-01

General problems arising in development of intense neutron sources as a part of accelerator-driven systems and first experience accumulated in IPPE during last several years are briefly discussed. The calculation and analysis of nuclear-physical properties of the targets, such as the accumulation of spallation reaction products, activity and heat release for various versions of heavy liquid metal targets were performed in IPPE. The sensitivity of the results of calculations to the various sets of nuclear data was considered. The main radiology characteristics of the lead-bismuth target, which is now under construction in the frame of ISTC Project # 559, are briefly described. The production of short-lived nuclides was estimated, the total activity and volatile nuclide accumulation, residual heat release, the energies of various decay modes were analysed.

Multiplexer and time duration measuring circuit

DOEpatents

Gray, Jr., James

1980-01-01

A multiplexer device is provided for multiplexing data in the form of randomly developed, variable width pulses from a plurality of pulse sources to a master storage. The device includes a first multiplexer unit which includes a plurality of input circuits each coupled to one of the pulse sources, with all input circuits being disabled when one input circuit receives an input pulse so that only one input pulse is multiplexed by the multiplexer unit at any one time.

Tunable pulsed narrow bandwidth light source

DOEpatents

Powers, Peter E.; Kulp, Thomas J.

2002-01-01

A tunable pulsed narrow bandwidth light source and a method of operating a light source are provided. The light source includes a pump laser, first and second non-linear optical crystals, a tunable filter, and light pulse directing optics. The method includes the steps of operating the pump laser to generate a pulsed pump beam characterized by a nanosecond pulse duration and arranging the light pulse directing optics so as to (i) split the pulsed pump beam into primary and secondary pump beams; (ii) direct the primary pump beam through an input face of the first non-linear optical crystal such that a primary output beam exits from an output face of the first non-linear optical crystal; (iii) direct the primary output beam through the tunable filter to generate a sculpted seed beam; and direct the sculpted seed beam and the secondary pump beam through an input face of the second non-linear optical crystal such that a secondary output beam characterized by at least one spectral bandwidth on the order of about 0.1 cm.sup.-1 and below exits from an output face of the second non-linear optical crystal.

High-power multi-megahertz source of waveform-stabilized few-cycle light

PubMed Central

Pronin, O.; Seidel, M.; Lücking, F.; Brons, J.; Fedulova, E.; Trubetskov, M.; Pervak, V.; Apolonski, A.; Udem, Th.; Krausz, F.

2015-01-01

Waveform-stabilized laser pulses have revolutionized the exploration of the electronic structure and dynamics of matter by serving as the technological basis for frequency-comb and attosecond spectroscopy. Their primary sources, mode-locked titanium-doped sapphire lasers and erbium/ytterbium-doped fibre lasers, deliver pulses with several nanojoules energy, which is insufficient for many important applications. Here we present the waveform-stabilized light source that is scalable to microjoule energy levels at the full (megahertz) repetition rate of the laser oscillator. A diode-pumped Kerr-lens-mode-locked Yb:YAG thin-disk laser combined with extracavity pulse compression yields waveform-stabilized few-cycle pulses (7.7 fs, 2.2 cycles) with a pulse energy of 0.15 μJ and an average power of 6 W. The demonstrated concept is scalable to pulse energies of several microjoules and near-gigawatt peak powers. The generation of attosecond pulses at the full repetition rate of the oscillator comes into reach. The presented system could serve as a primary source for frequency combs in the mid infrared and vacuum UV with unprecedented high power levels. PMID:25939968

Event-Based Processing of Neutron Scattering Data

DOE PAGES

Peterson, Peter F.; Campbell, Stuart I.; Reuter, Michael A.; ...

2015-09-16

Many of the world's time-of-flight spallation neutrons sources are migrating to the recording of individual neutron events. This provides for new opportunities in data processing, the least of which is to filter the events based on correlating them with logs of sample environment and other ancillary equipment. This paper will describe techniques for processing neutron scattering data acquired in event mode that preserve event information all the way to a final spectrum, including any necessary corrections or normalizations. This results in smaller final errors, while significantly reducing processing time and memory requirements in typical experiments. Results with traditional histogramming techniquesmore » will be shown for comparison.« less

Future prospects for measurements of mass hierarchy and CP violation

NASA Astrophysics Data System (ADS)

Lang, Karol

2015-03-01

We present a brief overview of current plans to pursue two challenging goals, resolution of the neutrino mass hierarchy and determination of the CP phase of the PMNS neutrino mixing matrix. Future prospects include large atmospheric experiments, PINGU, ORCA, and INO-ICAL, medium baseline reactor experiments, JUNO and RENO- 50, and long baseline accelerator experiments, LBNE, LBNO, and Hyper-Kamiokande. There are also new initiatives emerging, ESSνSB at the European Spallation Source, and CHIPS in the NuMI neutrino beam. This is a multifaceted, vigorous, and technically difficult world-wide program. It will likely take more than a decade to start reaping its benefits.

Improving the work function of the niobium surface of SRF cavities by plasma processing

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

Tyagi, P. V.; Doleans, M.; Hannah, B.

2016-01-01

An in situ plasma processing technique using chemically reactive oxygen plasma to remove hydrocarbons from superconducting radio frequency cavity surfaces at room temperature was developed at the spallation neutron source, at Oak Ridge National Laboratory. To understand better the interaction between the plasma and niobium surface, surface studies on small samples were performed. In this article, we report the results from those surface studies. The results show that plasma processing removes hydrocarbons from top surface and improves the surface work function by 0.5₋1.0 eV. Improving the work function of RF surface of cavities can help to improve their operational performance.

CSNS computing environment Based on OpenStack

NASA Astrophysics Data System (ADS)

Li, Yakang; Qi, Fazhi; Chen, Gang; Wang, Yanming; Hong, Jianshu

2017-10-01

Cloud computing can allow for more flexible configuration of IT resources and optimized hardware utilization, it also can provide computing service according to the real need. We are applying this computing mode to the China Spallation Neutron Source(CSNS) computing environment. So, firstly, CSNS experiment and its computing scenarios and requirements are introduced in this paper. Secondly, the design and practice of cloud computing platform based on OpenStack are mainly demonstrated from the aspects of cloud computing system framework, network, storage and so on. Thirdly, some improvments to openstack we made are discussed further. Finally, current status of CSNS cloud computing environment are summarized in the ending of this paper.

Foil cycling technique for the VESUVIO spectrometer operating in the resonance detector configuration

NASA Astrophysics Data System (ADS)

Schooneveld, E. M.; Mayers, J.; Rhodes, N. J.; Pietropaolo, A.; Andreani, C.; Senesi, R.; Gorini, G.; Perelli-Cippo, E.; Tardocchi, M.

2006-09-01

This article reports a novel experimental technique, namely, the foil cycling technique, developed on the VESUVIO spectrometer (ISIS spallation source) operating in the resonance detector configuration. It is shown that with a proper use of two foils of the same neutron absorbing material it is possible, in a double energy analysis process, to narrow the width of the instrumental resolution of a spectrometer operating in the resonance detector configuration and to achieve an effective subtraction of the neutron and gamma backgrounds. Preliminary experimental results, obtained from deep inelastic neutron scattering measurements on lead, zirconium hydride, and deuterium chloride samples, are presented.

Dual initiation strip charge apparatus and methods for making and implementing the same

DOEpatents

Jakaboski, Juan-Carlos [Albuquerque, NM; Todd,; Steven, N [Rio Rancho, NM; Polisar, Stephen [Albuquerque, NM; Hughs, Chance [Tijeras, NM

2011-03-22

A Dual Initiation Strip Charge (DISC) apparatus is initiated by a single initiation source and detonates a strip of explosive charge at two separate contacts. The reflection of explosively induced stresses meet and create a fracture and breach a target along a generally single fracture contour and produce generally fragment-free scattering and no spallation. Methods for making and implementing a DISC apparatus provide numerous advantages over previous methods of creating explosive charges by utilizing steps for rapid prototyping; by implementing efficient steps and designs for metering consistent, repeatable, and controlled amount of high explosive; and by utilizing readily available materials.

DANCE : a 4[pi] barium fluoride detector for measuring neutron capture on unstable nuclei /.

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

Ullmann, J. L.; Haight, Robert C.; Hunt, L. F.

2002-01-01

Measurements of neutron capture on unstable nuclei are important for studies of s-process nucleosynthesis, nuclear waste transmutation, and stewardship science. A 160-element, 4{pi} barium fluoride detector array, and associated neutron flight path, is being constructed to make capture measurements at the moderated neutron spallation source at LANSCE. Measurements can be made on as little as 1 mg of sample material over energies from near thermal to near 100 keV. The design of the DANCE array is described and neutron flux measurements from flight path commissioning are shown. The array is expected to be complete by the end of 2002.

Neutron diffraction measurements on a reference metallic sample with a high-efficiency GEM side-on 10B-based thermal neutron detector

NASA Astrophysics Data System (ADS)

Pietropaolo, A.; Claps, G.; Fedrigo, A.; Grazzi, F.; Höglund, C.; Murtas, F.; Scherillo, A.; Schmidt, S.; Schooneveld, E. M.

2018-03-01

The upgraded version of the GEM side-on thermal neutron detector was successfully tested in a neutron diffraction experiment on a reference sample using the INES diffractometer at the ISIS spallation neutron source, UK. The performance of the new 10B4C-based detector is compared to that of a standard 3He tube, operating at the instrument as a part of the detectors assembly. The results show that the upgraded detector has a better resolution and an efficiency of the same order of magnitude of a 3He-based detector.

Search for Time Reversal Violating Effects: R-Correlation Measurement in Neutron Decay.

PubMed

Bodek, K; Ban, G; Beck, M; Bialek, A; Bryś, T; Czarnecki, A; Fetscher, W; Gorel, P; Kirch, K; Kistryn, St; Kozela, A; Kuźniak, M; Lindroth, A; Naviliat-Cuncic, O; Pulut, J; Serebrov, A; Severijns, N; Stephan, E; Zejma, J

2005-01-01

An experiment aiming at the simultaneous determination of both transversal polarization components of electrons emitted in the decay of free neutrons begins data taking using the polarized cold neutron beam (FUNSPIN) from the Swiss Neutron Spallation Source (SINQ) at the Paul-Scherrer Institute, Villigen. A non-zero value of R due to the e(-) polarization component, which is perpendicular to the plane spanned by the spin of the decaying neutron and the electron momentum, would signal a violation of time reversal symmetry and thus physics beyond the Standard Model. Present status of the project and the results from analysis of the first data sample will be discussed.

Effect of source frequency and pulsing on the SiO2 etching characteristics of dual-frequency capacitive coupled plasma

NASA Astrophysics Data System (ADS)

Kim, Hoe Jun; Jeon, Min Hwan; Mishra, Anurag Kumar; Kim, In Jun; Sin, Tae Ho; Yeom, Geun Young

2015-01-01

A SiO2 layer masked with an amorphous carbon layer (ACL) has been etched in an Ar/C4F8 gas mixture with dual frequency capacitively coupled plasmas under variable frequency (13.56-60 MHz)/pulsed rf source power and 2 MHz continuous wave (CW) rf bias power, the effects of the frequency and pulsing of the source rf power on the SiO2 etch characteristics were investigated. By pulsing the rf power, an increased SiO2 etch selectivity was observed with decreasing SiO2 etch rate. However, when the rf power frequency was increased, not only a higher SiO2 etch rate but also higher SiO2 etch selectivity was observed for both CW and pulse modes. A higher CF2/F ratio and lower electron temperature were observed for both a higher source frequency mode and a pulsed plasma mode. Therefore, when the C 1s binding states of the etched SiO2 surfaces were investigated using X-ray photoelectron spectroscopy (XPS), the increase of C-Fx bonding on the SiO2 surface was observed for a higher source frequency operation similar to a pulsed plasma condition indicating the increase of SiO2 etch selectivity over the ACL. The increase of the SiO2 etch rate with increasing etch selectivity for the higher source frequency operation appears to be related to the increase of the total plasma density with increasing CF2/F ratio in the plasma. The SiO2 etch profile was also improved not only by using the pulsed plasma but also by increasing the source frequency.

Multiple frequency optical mixer and demultiplexer and apparatus for remote sensing

NASA Technical Reports Server (NTRS)

Chen, Jeffrey R. (Inventor)

2010-01-01

A pulsed laser system includes a modulator module configured to provide pulsed electrical signals and a plurality of solid-state seed sources coupled to the modulator module and configured to operate, responsive to the pulsed electrical signals, in a pulse mode. Each of the plurality of solid-state seed sources is tuned to a different frequency channel separated from any adjacent frequency channel by a frequency offset. The pulsed laser system also includes a combiner that combines outputs from each of the solid state seed sources into a single optical path and an optical doubler and demultiplexer coupled to the single optical path and providing each doubled seed frequency on a separate output path.

Multimodal fiber source for nonlinear microscopy based on a dissipative soliton laser

PubMed Central

Lamb, Erin S.; Wise, Frank W.

2015-01-01

Recent developments in high energy femtosecond fiber lasers have enabled robust and lower-cost sources for multiphoton-fluorescence and harmonic-generation imaging. However, picosecond pulses are better suited for Raman scattering microscopy, so the ideal multimodal source for nonlinear microcopy needs to provide both durations. Here we present spectral compression of a high-power femtosecond fiber laser as a route to producing transform-limited picosecond pulses. These pulses pump a fiber optical parametric oscillator to yield a robust fiber source capable of providing the synchronized picosecond pulse trains needed for Raman scattering microscopy. Thus, this system can be used as a multimodal platform for nonlinear microscopy techniques. PMID:26417497

RF synchronized short pulse laser ion source

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

Fuwa, Yasuhiro, E-mail: fuwa@kyticr.kuicr.kyoto-u.ac.jp; Iwashita, Yoshihisa; Tongu, Hiromu

A laser ion source that produces shortly bunched ion beam is proposed. In this ion source, ions are extracted immediately after the generation of laser plasma by an ultra-short pulse laser before its diffusion. The ions can be injected into radio frequency (RF) accelerating bucket of a subsequent accelerator. As a proof-of-principle experiment of the ion source, a RF resonator is prepared and H{sub 2} gas was ionized by a short pulse laser in the RF electric field in the resonator. As a result, bunched ions with 1.2 mA peak current and 5 ns pulse length were observed at themore » exit of RF resonator by a probe.« less

Cross sections for production of the 15.10 MeV and other astrophysically significant gamma-ray lines through excitation and spallation of sup 12 C and sup 16 O with protons

NASA Technical Reports Server (NTRS)

Lang, F. L.; Werntz, C. W.; Crannell, C. J.; Trombka, J. I.; Chang, C. C.

1986-01-01

The ratio of the flux of 15.10-MeV gamma rays to the flux of 4.438-MeV gamma rays resulting from excitation of the corresponding states in C-12 as a sensitive measure of the spectrum of the exciting particles produced in solar flares and other cosmic sources. These gamma rays are produced predominantly by interactions with C-12 and O-16, both of which are relatively abundant in the solar photosphere. Gamma ray production cross sections for proton interactions have been reported previously for all important channels except for the production of 15.10-MeV gamma rays from O-16. The first reported measurement of the 15.10-MeV gamma ray production cross section from p + O-16 is presented here. The University of Maryland cyclotron was employed to produce 40-, 65-, and 86-MeV protons which interacted with CH2 and BeO targets. The resultant gamma ray spectra were measured with a high-purity germanium semiconductor detector at 70, 90, 110, 125, and 140 degrees relative to the direction of the incident beam for each proton energy. Other gamma ray lines resulting from direct excitation and spallation reactions with C-12 and 0-16 were observed as well, and their gamma ray production cross sections described.

Spallative production of Li, Be and B in superbubbles

NASA Astrophysics Data System (ADS)

Parizot, Etienne

We investigate the spallative production of the light elements (Li, Be and B) associated with the evolution of a superbubble (SB) blown by repeated supernova explosions in an OB association. It is shown that if about ten percent of the SN energy can power the acceleration of particles from the material inside the SB, the observed abundances of LiBeB in halo stars, as a function of O, can be explained in a fully consistent way over several decades of metallicity. We investigate two different energy spectra for the EPs: the standard cosmic ray source spectrum and a specific `SB spectrum' as results from Bykov's SB acceleration mechanism. We find that the latter spectrum is more efficient in producing LiBeB, and that the SNR spectrum can be reconciled with the observational data if an imperfect mixing of the SN ejecta with the rest of the SB material and/or a selective acceleration is invoked (enhancing the C and O abundance amongst the EPs by a factor of ˜ 6). One consequence of the model is that the observed linear growth of Be and B abundances as a function of the metallicity expresses a dilution line rather than a continuous, monotonic increase throughout the Galaxy. We also find that the recent 6 Li observations in halo stars fit equally well in the framework of the SB model (see Parizot & Drury, 1999c, for more details).

Pulsed source ion implantation apparatus and method

DOEpatents

Leung, Ka-Ngo

1996-01-01

A new pulsed plasma-immersion ion-implantation apparatus that implants ions in large irregularly shaped objects to controllable depth without overheating the target, minimizing voltage breakdown, and using a constant electrical bias applied to the target. Instead of pulsing the voltage applied to the target, the plasma source, for example a tungsten filament or a RF antenna, is pulsed. Both electrically conducting and insulating targets can be implanted.

Studies on cosmogenic nuclides in meteorites with regard to an application as potential depth indicators

NASA Technical Reports Server (NTRS)

Sarafin, R.; Herpers, U.; Englert, P.; Wieler, R.; Signer, P.; Bonani, G.; Hofmann, H. J.; Morenzoni, E.; Nessi, M.; Suter, M.

1986-01-01

Measurements of stable and radioactive spallation products in meteorites allow to investigate their histories, especially with respect to the exposure to galactic cosmic ray particles and the pre-atmospheric size of the object. While the concentrations of spallation products lead to the determination of exposure and terrestrial ages, production rate ratios are characteristic for the location of the sample in the meteorite. So, one of the aims of this investigation on meteorites is to obtain depth indicators from suitable pairs of cosmogenic nuclides. Because of the different depth profiles for nuclide productions it is necessary to determine the concentrations of a larger number of spallation products in aliquots of a single small sample. Such same sample measurements of Be-10 and light noble gases were performed on 15 ordinary chondrites (7 H- and 8 L-chondrites. Be-10 was determined by accelerator mass spectrometry and the noble gases were measured by static mass spectrometry. The results are summarized and discussed.

PULSED ION SOURCE

DOEpatents

Martina, E.F.

1958-10-14

An improved pulsed ion source of the type where the gas to be ionized is released within the source by momentary heating of an electrode occluded with the gas is presented. The other details of the ion source construction include an electron emitting filament and a positive reference grid, between which an electron discharge is set up, and electrode means for withdrawing the ions from the source. Due to the location of the gas source behind the electrode discharge region, and the positioning of the vacuum exhaust system on the opposite side of the discharge, the released gas is drawn into the electron discharge and ionized in accurately controlled amounts. Consequently, the output pulses of the ion source may be accurately controlled.

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

Ion Source Development at the SNS

NASA Astrophysics Data System (ADS)

Welton, R. F.; Stockli, M. P.; Murray, S. N.; Carr, J.; Carmichael, J.; Goulding, R. H.; Baity, F. W.

2007-08-01

The US Spallation Neutron Source (SNS) has recently begun producing neutrons and is currently on track to becoming a world-leading facility for material science based on neutron scattering. The facility is comprised of an H- ion source, a linear accelerator, an accumulator ring, a liquid-Hg target and a suite of neutron scattering instruments. Over the next several years the average H- current from the ion source will be increased in order to meet the baseline facility requirement of providing 1.4 MW of beam-power to the target and the SNS power upgrade power requirement of 2+ MW on target. Meeting the latter goal will require H- currents of 70-100 mA with an RMS emittance of 0.20-0.35 π mm mrad and a ˜7% duty-factor. To date, the RF-driven-multicusp SNS ion source has only been able to demonstrate sustained operation at 33 mA of beam current at a ˜7% duty-factor. This report details our efforts to develop variations of the current ion source which can meet these requirements. Designs and experimental results are presented for helicon plasma drivers, high-power external antennas, glow-discharge plasma guns and advanced Cs systems.

Dual amplitude pulse generator for radiation detectors

DOEpatents

Hoggan, Jerry M.; Kynaston, Ronnie L.; Johnson, Larry O.

2001-01-01

A pulsing circuit for producing an output signal having a high amplitude pulse and a low amplitude pulse may comprise a current source for providing a high current signal and a low current signal. A gate circuit connected to the current source includes a trigger signal input that is responsive to a first trigger signal and a second trigger signal. The first trigger signal causes the gate circuit to connect the high current signal to a pulse output terminal whereas the second trigger signal causes the gate circuit to connect the low current signal to the pulse output terminal.

Energy deposition calculated by PHITS code in Pb spallation target

NASA Astrophysics Data System (ADS)

Yu, Quanzhi

2016-01-01

Energy deposition in a Pb spallation target irradiated by high energetic protons was calculated by PHITS2.52 code. The validation of the energy deposition and neutron production calculated by PHITS code was performed. Results show good agreements between the simulation results and the experimental data. Detailed comparison shows that for the total energy deposition, PHITS simulation result was about 15% overestimation than that of the experimental data. For the energy deposition along the length of the Pb target, the discrepancy mainly presented at the front part of the Pb target. Calculation indicates that most of the energy deposition comes from the ionizations of the primary protons and the produced secondary particles. With the event generator mode of PHITS, the deposit energy distribution for the particles and the light nulclei is presented for the first time. It indicates that the primary protons with energy more than 100 MeV are the most contributors to the total energy deposition. The energy depositions peaking at 10 MeV and 0.1 MeV, are mainly caused by the electrons, pions, d, t, 3He and also α particles during the cascade process and the evaporation process, respectively. The energy deposition density caused by different proton beam profiles are also calculated and compared. Such calculation and analyses are much helpful for better understanding the physical mechanism of energy deposition in the spallation target, and greatly useful for the thermal hydraulic design of the spallation target.

Solid methane in neutron radiation: Cryogenic moderators and cometary cryo volcanism

NASA Astrophysics Data System (ADS)

Kirichek, O.; Lawson, C. R.; Jenkins, D. M.; Ridley, C. J. T.; Haynes, D. J.

2017-12-01

The effect of ionizing radiation on solid methane has previously been an area of interest in the astrophysics community. In the late 1980s this interest was further boosted by the possibility of using solid methane as a moderating medium in spallation neutron sources. Here we present test results of solid methane moderators commissioned at the ISIS neutron source, and compare them with a model based on the theory of thermal explosion. Good agreement between the moderator test data and our model suggests that the process of radiolysis defect recombination happens at two different temperature ranges: the ;lower temperature; recombination process occurs at around 20 K, with the ;higher temperature; process taking place between 50 and 60 K. We discuss consequences of this mechanism for the designing and operation of solid methane moderators used in advanced neutron sources. We also discuss the possible role of radiolysis defect recombination processes in cryo-volcanism on comets, and suggest an application based on this phenomenon.

Gaussian temporal modulation for the behavior of multi-sinc Schell-model pulses in dispersive media

NASA Astrophysics Data System (ADS)

Liu, Xiayin; Zhao, Daomu; Tian, Kehan; Pan, Weiqing; Zhang, Kouwen

2018-06-01

A new class of pulse source with correlation being modeled by the convolution operation of two legitimate temporal correlation function is proposed. Particularly, analytical formulas for the Gaussian temporally modulated multi-sinc Schell-model (MSSM) pulses generated by such pulse source propagating in dispersive media are derived. It is demonstrated that the average intensity of MSSM pulses on propagation are reshaped from flat profile or a train to a distribution with a Gaussian temporal envelope by adjusting the initial correlation width of the Gaussian pulse. The effects of the Gaussian temporal modulation on the temporal degree of coherence of the MSSM pulse are also analyzed. The results presented here show the potential of coherence modulation for pulse shaping and pulsed laser material processing.

Versatile monolithic 2-micron laser systems

NASA Astrophysics Data System (ADS)

Wysmolek, M.; Steinke, M.; Neumann, J.; Kracht, D.

2018-02-01

To answer a growing demand in development of high power pulsed and continuous wave sources at 2 micron spectral range we have participated in several projects, which resulted in a delivery of versatile monolithic sources providing picosecond, nanosecond and CW laser signal. As an example of pulsed sources we developed all-fiber monolithic devices based on a directly modulated laser diode and gain-switched laser diode to generate nanosecond and picosecond pulses, respectively, which are amplified in the same fiber amplifier chain up to 50 µJ with 96 ps and more than 1 mJ with pulses longer than 35 ns.

Radiation detector spectrum simulator

DOEpatents

Wolf, Michael A.; Crowell, John M.

1987-01-01

A small battery operated nuclear spectrum simulator having a noise source nerates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith generates several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.

Radiation detector spectrum simulator

DOEpatents

Wolf, M.A.; Crowell, J.M.

1985-04-09

A small battery operated nuclear spectrum simulator having a noise source generates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith to generate several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.

Pulsed source ion implantation apparatus and method

DOEpatents

Leung, K.N.

1996-09-24

A new pulsed plasma-immersion ion-implantation apparatus that implants ions in large irregularly shaped objects to controllable depth without overheating the target, minimizing voltage breakdown, and using a constant electrical bias applied to the target. Instead of pulsing the voltage applied to the target, the plasma source, for example a tungsten filament or a RF antenna, is pulsed. Both electrically conducting and insulating targets can be implanted. 16 figs.

PULSED ION SOURCE

DOEpatents

Ford, F.C.; Ruff, J.W.; Zizzo, S.G.; Cook, B.

1958-11-11

An ion source is described adapted for pulsed operation and producing copious quantities of ions with a particular ion egress geometry. The particular source construction comprises a conical member having a conducting surface formed of a metal with a gas occladed therein and narrow non-conducting portions hereon dividing the conducting surface. A high voltage pulse is applied across the conducting surface or producing a discharge across the surface. After the gas ions have been produced by the discharge, the ions are drawn from the source in a diverging conical beam by a specially constructed accelerating electrode.

Random pulse generator

NASA Technical Reports Server (NTRS)

Lindsey, R. S., Jr. (Inventor)

1975-01-01

An exemplary embodiment of the present invention provides a source of random width and random spaced rectangular voltage pulses whose mean or average frequency of operation is controllable within prescribed limits of about 10 hertz to 1 megahertz. A pair of thin-film metal resistors are used to provide a differential white noise voltage pulse source. Pulse shaping and amplification circuitry provide relatively short duration pulses of constant amplitude which are applied to anti-bounce logic circuitry to prevent ringing effects. The pulse outputs from the anti-bounce circuits are then used to control two one-shot multivibrators whose output comprises the random length and random spaced rectangular pulses. Means are provided for monitoring, calibrating and evaluating the relative randomness of the generator.

Self-pulsing in a 2 km single-mode fiber with the seed source broadened via WNS phase modulation

NASA Astrophysics Data System (ADS)

Zha, Congwen; Sun, Yinhong; Wang, Yanshan; Li, Tenglong; Peng, Wanjing; Ma, Yi; Zhang, Kai

2018-03-01

The seed source with spectral linewidth broadening via phase modulation is potential to achieve the higher output power with effective SBS suppression. However, self-pulsing from the amplifier output is harmful. In this work, we study the self-pulsing characteristics in a long single-mode fiber with lower self-pulsing threshold instead of the high power amplifier. We provide a powerful experimental support for the self-pulsing mechanism in high-power narrow-linewidth fiber lasers, which is important for further output power scaling.

Apparatus for coating a surface with a metal utilizing a plasma source

DOEpatents

Brown, I.G.; MacGill, R.A.; Galvin, J.E.

1991-05-07

An apparatus and method are disclosed for coating or layering a surface with a metal utilizing a metal vapor vacuum arc plasma source. The apparatus includes a trigger mechanism for actuating the metal vacuum vapor arc plasma source in a pulsed mode at a predetermined rate. The surface or substrate to be coated or layered is supported in position with the plasma source in a vacuum chamber. The surface is electrically biased for a selected period of time during the pulsed mode of operation of the plasma source. Both the pulsing of the metal vapor vacuum arc plasma source and the electrical biasing of the surface are synchronized for selected periods of time. 10 figures.

Apparatus for coating a surface with a metal utilizing a plasma source

DOEpatents

Brown, Ian G.; MacGill, Robert A.; Galvin, James E.

1991-01-01

An apparatus and method for coating or layering a surface with a metal utilizing a metal vapor vacuum arc plasma source. The apparatus includes a trigger mechanism for actuating the metal vacuum vapor arc plasma source in a pulsed mode at a predetermined rate. The surface or substrate to be coated or layered is supported in position with the plasma source in a vacuum chamber. The surface is electrically biased for a selected period of time during the pulsed mode of operation of the plasma source. Both the pulsing of the metal vapor vacuum arc plasma source and the electrical biasing of the surface are synchronized for selected periods of time.

Method for generating a plasma wave to accelerate electrons

DOEpatents

Umstadter, D.; Esarey, E.; Kim, J.K.

1997-06-10

The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention. 21 figs.

Method for generating a plasma wave to accelerate electrons

DOEpatents

Umstadter, Donald; Esarey, Eric; Kim, Joon K.

1997-01-01

The invention provides a method and apparatus for generating large amplitude nonlinear plasma waves, driven by an optimized train of independently adjustable, intense laser pulses. In the method, optimal pulse widths, interpulse spacing, and intensity profiles of each pulse are determined for each pulse in a series of pulses. A resonant region of the plasma wave phase space is found where the plasma wave is driven most efficiently by the laser pulses. The accelerator system of the invention comprises several parts: the laser system, with its pulse-shaping subsystem; the electron gun system, also called beam source, which preferably comprises photo cathode electron source and RF-LINAC accelerator; electron photo-cathode triggering system; the electron diagnostics; and the feedback system between the electron diagnostics and the laser system. The system also includes plasma source including vacuum chamber, magnetic lens, and magnetic field means. The laser system produces a train of pulses that has been optimized to maximize the axial electric field amplitude of the plasma wave, and thus the electron acceleration, using the method of the invention.

Surface modification to prevent oxide scale spallation

DOEpatents

Stephens, Elizabeth V; Sun, Xin; Liu, Wenning; Stevenson, Jeffry W; Surdoval, Wayne; Khaleel, Mohammad A

2013-07-16

A surface modification to prevent oxide scale spallation is disclosed. The surface modification includes a ferritic stainless steel substrate having a modified surface. A cross-section of the modified surface exhibits a periodic morphology. The periodic morphology does not exceed a critical buckling length, which is equivalent to the length of a wave attribute observed in the cross section periodic morphology. The modified surface can be created using at least one of the following processes: shot peening, surface blasting and surface grinding. A coating can be applied to the modified surface.

Generation of first hard X-ray pulse at Tsinghua Thomson Scattering X-ray Source.

PubMed

Du, Yingchao; Yan, Lixin; Hua, Jianfei; Du, Qiang; Zhang, Zhen; Li, Renkai; Qian, Houjun; Huang, Wenhui; Chen, Huaibi; Tang, Chuanxiang

2013-05-01

Tsinghua Thomson Scattering X-ray Source (TTX) is the first-of-its-kind dedicated hard X-ray source in China based on the Thomson scattering between a terawatt ultrashort laser and relativistic electron beams. In this paper, we report the experimental generation and characterization of the first hard X-ray pulses (51.7 keV) via head-on collision of an 800 nm laser and 46.7 MeV electron beams. The measured yield is 1.0 × 10(6) per pulse with an electron bunch charge of 200 pC and laser pulse energy of 300 mJ. The angular intensity distribution and energy spectra of the X-ray pulse are measured with an electron-multiplying charge-coupled device using a CsI scintillator and silicon attenuators. These measurements agree well with theoretical and simulation predictions. An imaging test using the X-ray pulse at the TTX is also presented.

High reliability low jitter pulse generator

DOEpatents

Savage, Mark E.; Stoltzfus, Brian S.

2013-01-01

A method and concomitant apparatus for generating pulses comprising providing a laser light source, disposing a voltage electrode between ground electrodes, generating laser sparks using the laser light source via laser spark gaps between the voltage electrode and the ground electrodes, and outputting pulses via one or more insulated ground connectors connected to the voltage electrode.

Source-to-sensation level ratio of transmitted biosonar pulses in an echolocating false killer whale.

PubMed

Supin, Alexander Ya; Nachtigall, Paul E; Breese, Marlee

2006-07-01

Transmitted biosonar pulses, and the brain auditory evoked potentials (AEPs) associated with those pulses, were synchronously recorded in a false killer whale Pseudorca crassidens trained to accept suction-cup EEG electrodes and to detect targets by echolocation. AEP amplitude was investigated as a function of the transmitted biosonar pulse source level. For that, a few thousand of the individual AEP records were sorted according to the spontaneously varied amplitude of synchronously recorded biosonar pulses. In each of the sorting bins (in 5-dB steps) AEP records were averaged to extract AEP from noise; AEP amplitude was plotted as a function of the biosonar pulse source level. For comparison, AEPs were recorded to external (in free field) sound pulses of a waveform and spectrum similar to those of the biosonar pulses; amplitude of these AEPs was plotted as a function of sound pressure level. A comparison of these two functions has shown that, depending on the presence or absence of a target, the sensitivity of the whale's hearing to its own transmitted biosonar pulses was 30 to 45 dB lower than might be expected in a free acoustic field.

Shutterless ion mobility spectrometer with fast pulsed electron source

NASA Astrophysics Data System (ADS)

Bunert, E.; Heptner, A.; Reinecke, T.; Kirk, A. T.; Zimmermann, S.

2017-02-01

Ion mobility spectrometers (IMS) are devices for fast and very sensitive trace gas analysis. The measuring principle is based on an initial ionization process of the target analyte. Most IMS employ radioactive electron sources, such as 63Ni or 3H. These radioactive materials have the disadvantage of legal restrictions and the electron emission has a predetermined intensity and cannot be controlled or disabled. In this work, we replaced the 3H source of our IMS with 100 mm drift tube length with our nonradioactive electron source, which generates comparable spectra to the 3H source. An advantage of our emission current controlled nonradioactive electron source is that it can operate in a fast pulsed mode with high electron intensities. By optimizing the geometric parameters and developing fast control electronics, we can achieve very short electron emission pulses for ionization with high intensities and an adjustable pulse width of down to a few nanoseconds. This results in small ion packets at simultaneously high ion densities, which are subsequently separated in the drift tube. Normally, the required small ion packet is generated by a complex ion shutter mechanism. By omitting the additional reaction chamber, the ion packet can be generated directly at the beginning of the drift tube by our pulsed nonradioactive electron source with only slight reduction in resolving power. Thus, the complex and costly shutter mechanism and its electronics can also be omitted, which leads to a simple low-cost IMS-system with a pulsed nonradioactive electron source and a resolving power of 90.

Measurement of proton momentum distributions using a direct geometry instrument

NASA Astrophysics Data System (ADS)

Senesi, R.; Kolesnikov, A. I.; Andreani, C.

2014-12-01

We report the results of inelastic neutron scattering measurements on bulk water and ice using the direct geometry SEQUOIA chopper spectrometer at the Spallation Neutron Source (USA), with incident energy Ei= 6 eV. In this set up the measurements allow to access the Deep Inelastic Neutron Scattering regime. The scattering is centred at the proton recoil energy given by the impulse approximation, and the shape of the recoil peak conveys information on the proton momentum distribution in the system. The comparison with the performance of inverse geometry instruments, such as VESUVIO at the ISIS source (UK), shows that complementary information can be accessed by the use of direct and inverse geometry instruments. Analysis of the neutron Compton profiles shows that the proton kinetic energy in ice at 271 K is larger than in room temperature liquid water, in agreement with previous measurements on VESUVIO.

Light element production by low energy nuclei from massive stars

NASA Technical Reports Server (NTRS)

Vangioni-Flam, E.; Casse, M.; Ramaty, R.

1997-01-01

The Orion complex is a source of gamma rays attributed to the de-excitation of fast carbon and oxygen nuclei excited through interactions with ambient hydrogen and helium. This has consequences for the production and evolution of light isotopes in the Galaxy, as massive stars appear as prolific sources of C-O rich low energy nuclei. The different stages of massive star evolution are considered in relation to the acceleration of nuclei to moderate energies. It is concluded that the low energy nuclear component originating from massive stars plays a larger role than the usual Galactic cosmic rays in shaping the evolution of Li-6, Be-9, B-10 and B-11, especially in the early Galactic evolution. The enhancement of the B-11/B-10 ratio observed in meteorites and in the interstellar medium is attributed to the interaction of low energy carbon nuclei with ambient H and to a lesser degree, to neutrino spallation.

Generation and parametric amplification of broadband chirped pulses in the near-infrared

NASA Astrophysics Data System (ADS)

Marcinkevičiūtė, A.; Michailovas, K.; Butkus, R.

2018-05-01

We demonstrate generation and optical parametric amplification of broadband chirped pulses in the range of 1.8- 2 . 5 μm. The setup is built around Ti:sapphire oscillator as a seed source and 1 kHz Nd:YAG laser system as a pump source. Visible broadband seed pulses are temporally stretched and amplified in a non-collinear optical parametric amplifier before being mixed with fundamental harmonic of the pump laser. Difference frequency generation between positively-chirped broadband pulses centered at 0 . 7 μm and non-chirped narrowband pulses at 1064 nm produces negatively-chirped wide spectral bandwidth pulses in the infrared. After subsequent parametric amplification, pulses with more than 0.5 mJ energy were obtained with spectral bandwidth supporting transform-limited pulse durations as short as 23 fs.

High-Energy, High-Pulse-Rate Light Sources for Enhanced Time-Resolved Tomographic PIV of Unsteady and Turbulent Flows

DTIC Science & Technology

2017-07-31

Report: High-Energy, High-Pulse-Rate Light Sources for Enhanced Time -Resolved Tomographic PIV of Unsteady & Turbulent Flows The views, opinions and/or...reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching...High-Energy, High-Pulse-Rate Light Sources for Enhanced Time -Resolved Tomographic PIV of Unsteady & Turbulent Flows Report Term: 0-Other Email

An ion source for radiofrequency-pulsed glow discharge time-of-flight mass spectrometry

NASA Astrophysics Data System (ADS)

González Gago, C.; Lobo, L.; Pisonero, J.; Bordel, N.; Pereiro, R.; Sanz-Medel, A.

2012-10-01

A Grimm-type glow discharge (GD) has been designed and constructed as an ion source for pulsed radiofrequency GD spectrometry when coupled to an orthogonal time of flight mass spectrometer. Pulse shapes of argon species and analytes were studied as a function of the discharge conditions using a new in-house ion source (UNIOVI GD) and results have been compared with a previous design (PROTOTYPE GD). Different behavior and shapes of the pulse profiles have been observed for the two sources evaluated, particularly for the plasma gas ionic species detected. In the more analytically relevant region (afterglow), signals for 40Ar+ with this new design were negligible, while maximum intensity was reached earlier in time for 41(ArH)+ than when using the PROTOTYPE GD. Moreover, while maximum 40Ar+ signals measured along the pulse period were similar in both sources, 41(ArH)+ and 80(Ar2)+ signals tend to be noticeable higher using the PROTOTYPE chamber. The UNIOVI GD design was shown to be adequate for sensitive direct analysis of solid samples, offering linear calibration graphs and good crater shapes. Limits of detection (LODs) are in the same order of magnitude for both sources, although the UNIOVI source provides slightly better LODs for those analytes with masses slightly higher than 41(ArH)+.

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

Hanada, M., E-mail: hanada.masaya@jaea.go.jp; Kojima, A.; Tobari, H.

In order to realize negative ion sources and accelerators to be applicable to International Thermonuclear Experimental Reactor and JT-60 Super Advanced, a large cesium (Cs)-seeded negative ion source and a multi-aperture and multi-stage electric acceleration have been developed at Japan Atomic Energy Agency (JAEA). Long pulse production and acceleration of the negative ion beams have been independently carried out. The long pulse production of the high current beams has achieved 100 s at the beam current of 15 A by modifying the JT-60 negative ion source. The pulse duration time is increased three times longer than that before the modification.more » As for the acceleration, a pulse duration time has been also extended two orders of magnitudes from 0.4 s to 60 s. The developments of the negative ion source and acceleration at JAEA are well in progress towards the realization of the negative ion sources and accelerators for fusion applications.« less

Characterization of a Surface-Flashover Ion Source with 10-250 ns Pulse Widths

NASA Astrophysics Data System (ADS)

Falabella, S.; Guethlein, G.; Kerr, P. L.; Meyer, G. A.; Morse, J. D.; Sampayan, S.; Tang, V.

2009-03-01

As a step towards developing an ultra compact D-D neutron source for various defense and homeland security applications, a compact ion source is needed. Towards that end, we are testing a pulsed, surface flashover source, with deuterated titanium films deposited on alumina substrates as the electrodes. An electrochemically-etched mask was used to define the electrode areas on the substrate during the sputtered deposition of the titanium films. Deuterium loading of the films was performed in an all metal-sealed vacuum chamber containing a heated stage. Deuterium ion current from the source was determined by measuring the neutrons produced when the ions impacted a deuterium-loaded target held at -90 kV. As the duration of the arc current is varied, it was observed that the integrated deuteron current per pulse initially increases rapidly, then reaches a maximum near a pulse length of 100 ns.

Spectral characteristics of quantum-cascade laser operating at 10.6 μm wavelength for a seed application in laser-produced-plasma extreme UV source.

PubMed

Nowak, Krzysztof M; Ohta, Takeshi; Suganuma, Takashi; Yokotsuka, Toshio; Fujimoto, Junichi; Mizoguchi, Hakaru; Endo, Akira

2012-11-15

In this Letter, we investigate, for the first time to our knowledge, the spectral properties of a quantum-cascade laser (QCL) from a point of view of a new application as a laser seeder for a nanosecond-pulse high-repetition frequency CO(2) laser operating at 10.6 μm wavelength. The motivation for this work is a renewed interest in such a pulse format and wavelength driven by a development of extreme UV (EUV) laser-produced-plasma (LPP) sources. These sources use pulsed multikilowatt CO(2) lasers to drive the EUV-emitting plasmas. Basic spectral performance characteristics of a custom-made QCL chip are measured, such as tuning range and chirp rate. The QCL is shown to have all essential qualities of a robust seed source for a high-repetition nanosecond-pulsed CO(2) laser required by EUV LPP sources.

Micron-size hydrogen cluster target for laser-driven proton acceleration

NASA Astrophysics Data System (ADS)

Jinno, S.; Kanasaki, M.; Uno, M.; Matsui, R.; Uesaka, M.; Kishimoto, Y.; Fukuda, Y.

2018-04-01

As a new laser-driven ion acceleration technique, we proposed a way to produce impurity-free, highly reproducible, and robust proton beams exceeding 100 MeV using a Coulomb explosion of micron-size hydrogen clusters. In this study, micron-size hydrogen clusters were generated by expanding the cooled high-pressure hydrogen gas into a vacuum via a conical nozzle connected to a solenoid valve cooled by a mechanical cryostat. The size distributions of the hydrogen clusters were evaluated by measuring the angular distribution of laser light scattered from the clusters. The data were analyzed mathematically based on the Mie scattering theory combined with the Tikhonov regularization method. The maximum size of the hydrogen cluster at 25 K and 6 MPa in the stagnation state was recognized to be 2.15 ± 0.10 μm. The mean cluster size decreased with increasing temperature, and was found to be much larger than that given by Hagena’s formula. This discrepancy suggests that the micron-size hydrogen clusters were formed by the atomization (spallation) of the liquid or supercritical fluid phase of hydrogen. In addition, the density profiles of the gas phase were evaluated for 25 to 80 K at 6 MPa using a Nomarski interferometer. Based on the measurement results and the equation of state for hydrogen, the cluster mass fraction was obtained. 3D particles-in-cell (PIC) simulations concerning the interaction processes of micron-size hydrogen clusters with high power laser pulses predicted the generation of protons exceeding 100 MeV and accelerating in a laser propagation direction via an anisotropic Coulomb explosion mechanism, thus demonstrating a future candidate in laser-driven proton sources for upcoming multi-petawatt lasers.

SECOND TARGET STATION MODERATOR PERFORMANCE WITH A ROTATING TARGET

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

Remec, Igor; Gallmeier, Franz X; Rennich, Mark J

2016-01-01

Oak Ridge National Laboratory manages and operates the Spallation Neutron Source and the High Flux Isotope Reactor, two of the world's most advanced neutron scattering facilities. Both facilities are funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Science, and are available to researchers from all over the world. Delivering cutting edge science requires continuous improvements and development of the facilities and instruments. The SNS was designed from the outset to accommodate an additional target station, or Second Target Station (STS), and an upgraded accelerator feeding proton beams to STS and the existing First Targetmore » Station (FTS). Upgrade of the accelerator and the design and construction of STS are being proposed. The presently considered STS configuration is driven with short (<1 s) proton pulses at 10 Hz repetition rate and 467 kW proton beam power, and is optimized for high intensity and high resolution long wavelength neutron applications. STS will allow installation of 22 beamlines and will expand and complement the current national neutron scattering capabilities. In 2015 the STS studies were performed for a compact tungsten target; first a stationary tungsten plate target was analyzed to considerable details and then dropped in favor of a rotating target. For both target options the proton beam footprint as small as acceptable from mechanical and heat removal aspects is required to arrive at a compact-volume neutron production zone in the target, which is essential for tight coupling of target and moderators and for achieving high-intensity peak neutron fluxes. This paper will present recent STS work with the emphasis on neutronics and moderator performance.« less

Synthesis of arbitrary pulse waveforms in QCL-seeded ns-pulse CO₂ laser for optimization of an LPP EUV source.

PubMed

Nowak, Krzysztof M; Kurosawa, Yoshiaki; Suganuma, Takashi; Kawasuji, Yasufumi; Nakarai, Hiroaki; Saito, Takashi; Fujimoto, Junichi; Mizoguchi, Hakaru

2016-07-01

One of the unique features of the quantum-cascade-laser-seeded, nanosecond-pulse CO₂ laser, invented for the purpose of generation of extreme UV by laser-produced-plasma, is a robust synthesis of arbitrary pulse waveforms. In the present Letter we report on experimental results that are, to our best knowledge, the first demonstration of such functionality obtainable from nanosecond-pulse CO₂ laser technology. An online pulse duration adjustment within 10-40 ns was demonstrated, and a few exemplary pulse waveforms were synthesized, such as "tophat," "tailspike," and "leadspike" shapes. Such output characteristics may be useful to optimize the performance of LPP EUV source.

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

Influence of sweeping detonation-wave loading on damage evolution during spallation loading of tantalum in both a planar and curved geometry

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

Gray, George Thompson III; Hull, Lawrence Mark; Livescu, Veronica

Widespread research over the past five decades has provided a wealth of experimental data and insight concerning the shock hardening, damage evolution, and the spallation response of materials subjected to square-topped shock-wave loading profiles. However, fewer quantitative studies have been conducted on the effect of direct, in-contact, high explosive (HE)-driven Taylor wave (unsupported shocks) loading on the shock hardening, damage evolution, or spallation response of materials. Systematic studies quantifying the effect of sweeping-detonation wave loading are yet sparser. In this study, the damage evolution and spallation response of Ta is shown to be critically dependent on the peak shock stress,more » the geometry of the sample (flat or curved plate geometry), and the shock obliquity during sweeping-detonation-wave shock loading. Sweepingwave loading in the flat-plate geometry is observed to: a) yield a lower spall strength than previously documented for 1-D supported-shock-wave loading, b) exhibit increased shock hardening as a function of increasing obliquity, and c) lead to an increased incidence of deformation twin formation with increasing shock obliquity. Sweeping-wave loading of a 10 cm radius curved Ta plate is observed to: a) lead to an increase in the shear stress as a function of increasing obliquity, b) display a more developed level of damage evolution, extensive voids and coalescence, and lower spall strength with obliquity in the curved plate than seen in the flat-plate sweeping-detonation wave loading for an equivalent HE loading, and c) no increased propensity for deformation twin formation with increasing obliquity as seen in the flat-plate geometry. The overall observations comparing and contrasting the flat versus curved sweeping-wave spall experiments with 1D loaded spallation behavior suggests a coupled influence of obliquity and geometry on dynamic shock-induced damage evolution and spall strength. Coupled experimental and modeling research to quantify the combined effects of sweeping-wave loading with increasingly complex sample geometries on the shockwave response of materials is clearly crucial to providing the basis for developing and thereafter validation of predictive modeling capability.« less

Small plasma focus as neutron pulsed source for nuclides identification

NASA Astrophysics Data System (ADS)

Milanese, M.; Niedbalski, J.; Moroso, R.; Barbaglia, M.; Mayer, R.; Castillo, F.; Guichón, S.

2013-10-01

In this paper, we present preliminary results on the feasibility of employing a low energy (2 kJ, 31 kV) plasma focus device as a portable source of pulsed neutron beams (2.45 MeV) generated by nuclear fusion reactions D-D, for the "in situ" analysis of substances by nuclear activation. This source has the relevant advantage of being pulsed at requirement, transportable, not permanently radioactive, without radioactive waste, cheap, among others. We prove the feasibility of using this source showing several spectra of the characteristic emission line for manganese, gold, lead, and silver.

Small plasma focus as neutron pulsed source for nuclides identification.

PubMed

Milanese, M; Niedbalski, J; Moroso, R; Barbaglia, M; Mayer, R; Castillo, F; Guichón, S

2013-10-01

In this paper, we present preliminary results on the feasibility of employing a low energy (2 kJ, 31 kV) plasma focus device as a portable source of pulsed neutron beams (2.45 MeV) generated by nuclear fusion reactions D-D, for the "in situ" analysis of substances by nuclear activation. This source has the relevant advantage of being pulsed at requirement, transportable, not permanently radioactive, without radioactive waste, cheap, among others. We prove the feasibility of using this source showing several spectra of the characteristic emission line for manganese, gold, lead, and silver.

Laser post-processing of Inconel 625 made by selective laser melting

NASA Astrophysics Data System (ADS)

Witkin, David; Helvajian, Henry; Steffeney, Lee; Hansen, William

2016-04-01

The effect of laser remelting of surfaces of as-built Selective Laser Melted (SLM) Inconel 625 was evaluated for its potential to improve the surface roughness of SLM parts. Many alloys made by SLM have properties similar to their wrought counterparts, but surface roughness of SLM-made parts is much higher than found in standard machine shop operations. This has implications for mechanical properties of SLM materials, such as a large debit in fatigue properties, and in applications of SLM, where surface roughness can alter fluid flow characteristics. Because complexity and netshape fabrication are fundamental advantages of Additive Manufacturing (AM), post-processing by mechanical means to reduce surface roughness detracts from the potential utility of AM. Use of a laser to improve surface roughness by targeted remelting or annealing offers the possibility of in-situ surface polishing of AM surfaces- the same laser used to melt the powder could be amplitude modulated to smooth the part during the build. The effects of remelting the surfaces of SLM Inconel 625 were demonstrated using a CW fiber laser (IPG: 1064 nm, 2-50 W) that is amplitude modulated with a pulse profile to induce remelting without spallation or ablation. The process achieved uniform depth of melting and improved surface roughness. The results show that with an appropriate pulse profile that meters the heat-load, surface features such as partially sintered powder particles and surface connected porosity can be mitigated via a secondary remelting/annealing event.

Bacterial spores in granite survive hypervelocity launch by spallation: implications for lithopanspermia.

PubMed

Fajardo-Cavazos, Patricia; Langenhorst, Falko; Melosh, H Jay; Nicholson, Wayne L

2009-09-01

Bacterial spores are considered good candidates for endolithic life-forms that could survive interplanetary transport by natural impact processes, i.e., lithopanspermia. Organisms within rock can only embark on an interplanetary journey if they survive ejection from the surface of the donor planet and the associated extremes of compressional shock, heating, and acceleration. Previous simulation experiments have measured each of these three stresses more or less in isolation of one another, and results to date indicate that spores of the model organism Bacillus subtilis can survive each stress applied singly. Few simulations, however, have combined all three stresses simultaneously. Because considerable experimental and theoretical evidence supports a spallation mechanism for launch, we devised an experimental simulation of launch by spallation using the Ames Vertical Gun Range (AVGR). B. subtilis spores were applied to the surface of a granite target that was impacted from above by an aluminum projectile fired at 5.4 km/s. Granite spall fragments were captured in a foam recovery fixture and then recovered and assayed for shock damage by transmission electron microscopy and for spore survival by viability assays. Peak shock pressure at the impact site was calculated to be 57.1 GPa, though recovered spall fragments were only very lightly shocked at pressures of 5-7 GPa. Spore survival was calculated to be on the order of 10(-5), which is in agreement with results of previous static compressional shock experiments. These results demonstrate that endolithic spores can survive launch by spallation from a hypervelocity impact, which lends further evidence in favor of lithopanspermia theory.

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

Kasemir, Kay; Pearson, Matthew R

For several years, the Control System Studio (CS-Studio) Scan System has successfully automated the operation of beam lines at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) and Spallation Neutron Source (SNS). As it is applied to additional beam lines, we need to support simultaneous adjustments of temperatures or motor positions. While this can be implemented via virtual motors or similar logic inside the Experimental Physics and Industrial Control System (EPICS) Input/Output Controllers (IOCs), doing so requires a priori knowledge of experimenters requirements. By adding support for the parallel control of multiple process variables (PVs) to themore » Scan System, we can better support ad hoc automation of experiments that benefit from such simultaneous PV adjustments.« less

High-pressure studies on Ba-doped cobalt perovskites by neutron diffraction

NASA Astrophysics Data System (ADS)

Cao, Huibo; Garlea, Vasile; Wang, Fangwei; Dos Santos, Antonio; Cheng, Zhaohua

2012-02-01

Cobalt perovskite possess rich structural, magnetic and electrical properties depending on the subtle balance of the interactions among the spin, charge, and orbital degrees of freedom. Divalent hole-doped cobalt perovskites LaA^2+CoO3 exhibit structural phase transitions, metal-insulator transitions, and multi-magnetic phase transitions. High-pressure measurement is believed to mimic the size effects of the doped ions. We performed neutron diffraction experiments on selected Ba-doped LaCoO3 under pressures up to 6.3 GPa at SNAP at Spallation Neutron Source of ORNL. This work focuses on the high-pressure effects of the selected Ba-doped samples and the change of the phase diagram with pressure.

S=2 quasi-one-dimensional spin waves in CrCl2

NASA Astrophysics Data System (ADS)

Stone, Matthew; Ehlers, Georg; Granroth, Garrett

2014-03-01

We examine the magnetic excitation spectrum in the S = 2 Heisenberg antiferromagnet CrCl2. Inelastic neutron scattering measurements on powder samples are able to determine the significant exchange interactions in this system. A large anisotropy gap is observed in the spectrum below the Néel temperature and the ratio of the two largest exchange constants is Jc /Jb = 9 . 1 +/- 2 . 2 . However, no sign of a gapped quantum spin liquid excitation was found in the paramagnetic phase. The research was performed at Oak Ridge National Laboratory's Spallation Neutron Source and was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

Experimental Report: ORNL Proposal ID IPTS 8937

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

Mirmelstein, A.

2014-02-03

Neutron scattering experiment was performed using fine-resolution Fermi chopper spectrometer “SEQUOIA” installed at the Spallation Neutron Source, ORNL. Although this spectrometer is designed to measure inelastic neutron scattering spectra, during experiments a signal of elastic scattering is also recorded. The coherent nuclear component of this elastic scattering provides Bragg diffraction pattern of a sample, i.e., CeNi single crystal in our case. Therefore, it is possible to follow the CeNi structural variations as a function of pressure and to register structural phase transition. Measurements were performed at the temperature of 15 K under pressure of zero (ambient pressure at 15 K),more » 400, 800, and 2200 bars.« less

Vacuum System Upgrade for Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) at SNS

DOE PAGES

Stone, Christopher M.; Williams, Derrick C.; Price, Jeremy P.

2016-09-23

The Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) instrument at the Spallation Neutron Source (SNS), Oak Ridge, Tennessee, incorporates a 69m3 detector vessel with a vacuum system which required an upgrade with respect to performance, ease of operation, and maintenance. The upgrade focused on improving pumping performance as well as optimizing system design to minimize opportunity for operational error. This upgrade provided the following practical contributions: Reduced time required to evacuate from atmospheric pressure to 2mTorr from 500-1,000 minutes to 60-70 minutes Provided turn-key automated control with a multi-faceted interlock for personnel and machine safety.

Installation Status of the Electron Beam Profiler for the Fermilab Main Injector

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

Thurman-Keup, R.; Alvarez, M.; Fitzgerald, J.

2015-11-06

The planned neutrino program at Fermilab requires large proton beam intensities in excess of 2 MW. Measuring the transverse profiles of these high intensity beams is challenging and often depends on non-invasive techniques. One such technique involves measuring the deflection of a probe beam of electrons with a trajectory perpendicular to the proton beam. A device such as this is already in use at the Spallation Neutron Source at ORNL and the installation of a similar device is underway in the Main Injector at Fermilab. The present installation status of the electron beam profiler for the Main Injector will bemore » discussed together with some simulations and test stand results.« less

Hybrid systems for transuranic waste transmutation in nuclear power reactors: state of the art and future prospects

NASA Astrophysics Data System (ADS)

Yurov, D. V.; Prikhod'ko, V. V.

2014-11-01

The features of subcritical hybrid systems (HSs) are discussed in the context of burning up transuranic wastes from the U-Pu nuclear fuel cycle. The advantages of HSs over conventional atomic reactors are considered, and fuel cycle closure alternatives using HSs and fast neutron reactors are comparatively evaluated. The advantages and disadvantages of two HS types with neutron sources (NSs) of widely different natures -- nuclear spallation in a heavy target by protons and nuclear fusion in magnetically confined plasma -- are discussed in detail. The strengths and weaknesses of HSs are examined, and demand for them for closing the U-Pu nuclear fuel cycle is assessed.

Neutron total cross-section of hydrogenous and deuterated 1- and 2-propanol and n-butanol measured using the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

Rodríguez Palomino, L. A.; Dawidowski, J.; Márquez Damián, J. I.; Cuello, G. J.; Romanelli, G.; Krzystyniak, M.

2017-10-01

This work presents the total cross sections of a set of normal and deuterated alcohols (hydrogenous 1- and 2-propanol and n-butanol, 1-propanol(OD) and fully deuterated 2-propanol and n-butanol), measured at spectrometer VESUVIO (ISIS spallation neutron source, United Kingdom). Granada's Synthetic Model was applied to describe those systems and a satisfactory agreement with the measured total cross section was achieved in the range of energies from 10-3 to 100 eV. The input parameters of the model were determined from the essential features of the vibrational spectra of the atoms that compose the systems, which were studied using Molecular Dynamics.

Aerodynamic laser-heated contactless furnace for neutron scattering experiments at elevated temperatures

NASA Astrophysics Data System (ADS)

Landron, Claude; Hennet, Louis; Coutures, Jean-Pierre; Jenkins, Tudor; Alétru, Chantal; Greaves, Neville; Soper, Alan; Derbyshire, Gareth

2000-04-01

Conventional radiative furnaces require sample containment that encourages contamination at elevated temperatures and generally need windows which restrict the entrance and exit solid angles required for diffraction and scattering measurements. We describe a contactless windowless furnace based on aerodynamic levitation and laser heating which has been designed for high temperature neutron scattering experiments. Data from initial experiments are reported for crystalline and amorphous oxides at temperatures up to 1900 °C, using the spallation neutron source ISIS together with our laser-heated aerodynamic levitator. Accurate reproduction of thermal expansion coefficients and radial distribution functions have been obtained, demonstrating the utility of aerodynamic levitation methods for neutron scattering methods.

Vacuum System Upgrade for Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) at SNS

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

Stone, Christopher M.; Williams, Derrick C.; Price, Jeremy P.

The Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) instrument at the Spallation Neutron Source (SNS), Oak Ridge, Tennessee, incorporates a 69m3 detector vessel with a vacuum system which required an upgrade with respect to performance, ease of operation, and maintenance. The upgrade focused on improving pumping performance as well as optimizing system design to minimize opportunity for operational error. This upgrade provided the following practical contributions: Reduced time required to evacuate from atmospheric pressure to 2mTorr from 500-1,000 minutes to 60-70 minutes Provided turn-key automated control with a multi-faceted interlock for personnel and machine safety.

A novel small-angle neutron scattering detector geometry

PubMed Central

Kanaki, Kalliopi; Jackson, Andrew; Hall-Wilton, Richard; Piscitelli, Francesco; Kirstein, Oliver; Andersen, Ken H.

2013-01-01

A novel 2π detector geometry for small-angle neutron scattering (SANS) applications is presented and its theoretical performance evaluated. Such a novel geometry is ideally suited for a SANS instrument at the European Spallation Source (ESS). Motivated by the low availability and high price of 3He, the new concept utilizes gaseous detectors with 10B as the neutron converter. The shape of the detector is inspired by an optimization process based on the properties of the conversion material. Advantages over the detector geometry traditionally used on SANS instruments are discussed. The angular and time resolutions of the proposed detector concept are shown to satisfy the requirements of the particular SANS instrument. PMID:24046504

SNS Central Helium Liquefier spare Carbon Bed installation and commissioning

NASA Astrophysics Data System (ADS)

DeGraff, B.; Howell, M.; Kim, S.; Neustadt, T.

2017-12-01

The Spallation Neutron Source (SNS) Central Helium Liquefier (CHL) at Oak Ridge National Laboratory (ORNL) has been without major operations downtime since operations were started back in 2006. This system utilizes a vessel filled with activated carbon as the final major component to remove oil vapor from the compressed helium circuit prior to insertion into the system’s cryogenic cold box. The need for a spare carbon bed at SNS due to the variability of carbon media lifetime calculation to adsorption efficiency will be discussed. The fabrication, installation and commissioning of this spare carbon vessel will be presented. The novel plan for connecting the spare carbon vessel piping to the existing infrastructure will be presented.

Energy-dispersive neutron imaging and diffraction of magnetically driven twins in a Ni2MnGa single crystal magnetic shape memory alloy

NASA Astrophysics Data System (ADS)

Kabra, Saurabh; Kelleher, Joe; Kockelmann, Winfried; Gutmann, Matthias; Tremsin, Anton

2016-09-01

Single crystals of a partially twinned magnetic shape memory alloy, Ni2MnGa, were imaged using neutron diffraction and energy-resolved imaging techniques at the ISIS spallation neutron source. Single crystal neutron diffraction showed that the crystal produces two twin variants with a specific crystallographic relationship. Transmission images were captured using a time of flight MCP/Timepix neutron counting detector. The twinned and untwinned regions were clearly distinguishable in images corresponding to narrow-energy transmission images. Further, the spatially-resolved transmission spectra were used to elucidate the orientations of the crystallites in the different volumes of the crystal.

SNS STRIPPER FOIL FAILURE MODES AND THEIR CURES

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

Galambos, John D; Luck, Chris; Plum, Michael A

2010-01-01

The diamond stripper foils in use at the Spallation Neutron Source worked successfully with no failures until May 3, 2009, when we started experiencing a rash of foil system failures after increasing the beam power to ~840 kW. The main contributors to the failures are thought to be 1) convoy electrons, stripped from the incoming H beam, that strike the foil bracket and may also reflect back from the electron catcher, and 2) vacuum breakdown from the charge developed on the foil by secondary electron emission. In this paper we will detail these and other failure mechanisms, and describe themore » improvements we have made to mitigate them.« less

Modeling and Characterization of the Magnetocaloric Effect in Ni2MnGa Materials

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

Nicholson, Don M; Odbadrakh, Khorgolkhuu; Shassere, Benjamin

2014-01-01

Magnetic shape memory alloys have great promise as magneto-caloric effect refrigerant materials due to their combined magnetic and structural transitions. Computational and experimental research is reported on the Ni2MnGa material system. The magnetic states of this system are explored using the Wang-Landau statistical approach in conjunction with the Locally Self-consistent Multiple-Scattering method. The effects of alloying agents on the transition temperatures of the Ni2MnGa alloy are investigated using differential scanning calorimetry and superconducting quantum interference device. Experiments are performed at the Spallation Neutron Source at Oak Ridge National Laboratory to observe the structural and magnetic phase transformations.

Long Wavelength Electromagnetic Light Bullets Generated by a 10.6 micron CO2 Ultrashort Pulsed Source

DTIC Science & Technology

2016-11-29

AFRL-AFOSR-VA-TR-2016-0365 Long Wavelength Electromagnetic Light Bullets Generated by a 10.6 micron CO2 Ultrashort Pulsed Source Jerome Moloney...SUBTITLE "Long Wavelength Electromagnetic Light Bullets Generated by a 10.6 micron CO2 Ultrashort Pulsed Source 5a. CONTRACT NUMBER FA9550-15-1-0272 5b...afosr.reports.sgizmo.com/s3/> Subject: Final Report to Dr. Arje Nachman Contract/Grant Title: Long Wavelength Electromagnetic Light Bullets Generated by a 10.6

Directly driven source of multi-gigahertz, sub-picosecond optical pulses

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

Messerly, Michael J.; Dawson, Jay W.; Barty, Christopher P.J.

2015-10-20

A robust, compact optical pulse train source is described, with the capability of generating sub-picosecond micro-pulse sequences, which can be periodic as well as non-periodic, and at repetition rates tunable over decades of baseline frequencies, from MHz to multi-GHz regimes. The micro-pulses can be precisely controlled and formatted to be in the range of many ps in duration to as short as several fs in duration. The system output can be comprised of a continuous wave train of optical micro-pulses or can be programmed to provide gated bursts of macro-pulses, with each macro-pulse consisting of a specific number of micro-pulsesmore » or a single pulse picked from the higher frequency train at a repetition rate lower than the baseline frequency. These pulses could then be amplified in energy anywhere from the nJ to MJ range.« less

High duty cycle inverse Compton scattering X-ray source

DOE PAGES

Ovodenko, A.; Agustsson, R.; Babzien, M.; ...

2016-12-22

Inverse Compton Scattering (ICS) is an emerging compact X-ray source technology, where the small source size and high spectral brightness are of interest for multitude of applications. However, to satisfy the practical flux requirements, a high-repetition-rate ICS system needs to be developed. To this end, this article reports the experimental demonstration of a high peak brightness ICS source operating in a burst mode at 40 MHz. A pulse train interaction has been achieved by recirculating a picosecond CO 2 laser pulse inside an active optical cavity synchronized to the electron beam. The pulse train ICS performance has been characterized atmore » 5- and 15- pulses per train and compared to a single pulse operation under the same operating conditions. Lastly, with the observed near-linear X-ray photon yield gain due to recirculation, as well as noticeably higher operational reliability, the burst-mode ICS offers a great potential for practical scalability towards high duty cycles.« less

Femtosecond laser-electron x-ray source

DOEpatents

Hartemann, Frederic V.; Baldis, Hector A.; Barty, Chris P.; Gibson, David J.; Rupp, Bernhard

2004-04-20

A femtosecond laser-electron X-ray source. A high-brightness relativistic electron injector produces an electron beam pulse train. A system accelerates the electron beam pulse train. The femtosecond laser-electron X-ray source includes a high intra-cavity power, mode-locked laser and an x-ray optics system.

Compact 200 kHz HHG source driven by a few-cycle OPCPA

NASA Astrophysics Data System (ADS)

Harth, Anne; Guo, Chen; Cheng, Yu-Chen; Losquin, Arthur; Miranda, Miguel; Mikaelsson, Sara; Heyl, Christoph M.; Prochnow, Oliver; Ahrens, Jan; Morgner, Uwe; L'Huillier, Anne; Arnold, Cord L.

2018-01-01

We present efficient high-order harmonic generation (HHG) based on a high-repetition rate, few-cycle, near infrared (NIR), carrier-envelope phase stable, optical parametric chirped pulse amplifier (OPCPA), emitting 6 fs pulses with 9 μJ pulse energy. In krypton, we reach conversion efficiencies from the NIR to the extreme ultraviolet (XUV) radiation pulse energy on the order of ˜10-6 with less than 3 μJ driving pulse energy. This is achieved by optimizing the OPCPA for a spatially and temporally clean pulse and by a specially designed high-pressure gas target. In the future, the high efficiency of the HHG source will be beneficial for high-repetition rate two-colour (NIR-XUV) pump-probe experiments, where the available pulse energy from the laser has to be distributed economically between pump and probe pulses.

Fracture Mechanics Analyses of Subsurface Defects in Reinforced Carbon-Carbon Joggles Subjected to Thermo-Mechanical Loads

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.; Raju, Ivatury S.; Song, Kyongchan

2011-01-01

Coating spallation events have been observed along the slip-side joggle region of the Space Shuttle Orbiter wing-leading-edge panels. One potential contributor to the spallation event is a pressure build up within subsurface voids or defects due to volatiles or water vapor entrapped during fabrication, refurbishment, or normal operational use. The influence of entrapped pressure on the thermo-mechanical fracture-mechanics response of reinforced carbon-carbon with subsurface defects is studied. Plane-strain simulations with embedded subsurface defects are performed to characterize the fracture mechanics response for a given defect length when subjected to combined elevated-temperature and subsurface-defect pressure loadings to simulate the unvented defect condition. Various subsurface defect locations of a fixed-length substrate defect are examined for elevated temperature conditions. Fracture mechanics results suggest that entrapped pressure combined with local elevated temperatures have the potential to cause subsurface defect growth and possibly contribute to further material separation or even spallation. For this anomaly to occur, several unusual circumstances would be required making such an outcome unlikely but plausible.

Production of radioactive isotopes through cosmic muon spallation in KamLAND

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

Abe, S.; Furuno, K.; Gando, Y.

2010-02-15

Radioactive isotopes produced through cosmic muon spallation are a background for rare-event detection in nu detectors, double-beta-decay experiments, and dark-matter searches. Understanding the nature of cosmogenic backgrounds is particularly important for future experiments aiming to determine the pep and CNO solar neutrino fluxes, for which the background is dominated by the spallation production of {sup 11}C. Data from the Kamioka liquid-scintillator antineutrino detector (KamLAND) provides valuable information for better understanding these backgrounds, especially in liquid scintillators, and for checking estimates from current simulations based upon MUSIC, FLUKA, and GEANT4. Using the time correlation between detected muons and neutron captures, themore » neutron production yield in the KamLAND liquid scintillator is measured to be Y{sub n}=(2.8+-0.3)x10{sup -4} mu{sup -1} g{sup -1} cm{sup 2}. For other isotopes, the production yield is determined from the observed time correlation related to known isotope lifetimes. We find some yields are inconsistent with extrapolations based on an accelerator muon beam experiment.« less

Study of the Production of Radioactive Isotopes through Cosmic Muon Spallation in KamLAND

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

KamLAND Collaboration; Abe, S.; Enomoto, S.

2009-06-30

Radioactive isotopes produced through cosmic muon spallation are a background for rare event detection in {nu} detectors, double-beta-decay experiments, and dark-matter searches. Understanding the nature of cosmogenic backgrounds is particularly important for future experiments aiming to determine the pep and CNO solar neutrino fluxes, for which the background is dominated by the spallation production of {sup 11}C. Data from the Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) provides valuable information for better understanding these backgrounds, especially in liquid scintillator, and for checking estimates from current simulations based upon MUSIC, FLUKA, and Geant4. Using the time correlation between detected muons and neutronmore » captures, the neutron production yield in the KamLAND liquid scintillator is measured to be (2.8 {+-} 0.3) x 10{sup -4} n/({mu} {center_dot} (g/cm{sup 2})). For other isotopes, the production yield is determined from the observed time correlation related to known isotope lifetimes. We find some yields are inconsistent with extrapolations based on an accelerator muon beam experiment.« less

Study of 232Th(n, γ) and 232Th(n,f) reaction rates in a graphite moderated spallation neutron field produced by 1.6 GeV deuterons on lead target

NASA Astrophysics Data System (ADS)

Asquith, N. L.; Hashemi-Nezhad, S. R.; Westmeier, W.; Zhuk, I.; Tyutyunnikov, S.; Adam, J.

2015-02-01

The Gamma-3 assembly of the Joint Institute for Nuclear Research (JINR), Dubna, Russia is designed to emulate the neutron spectrum of a thermal Accelerator Driven System (ADS). It consists of a lead spallation target surrounded by reactor grade graphite. The target was irradiated with 1.6 GeV deuterons from the Nuclotron accelerator and the neutron capture and fission rate of 232Th in several locations within the assembly were experimentally measured. 232Th is a proposed fuel for envisaged Accelerator Driven Systems and these two reactions are fundamental to the performance and feasibility of 232Th in an ADS. The irradiation of the Gamma-3 assembly was also simulated using MCNPX 2.7 with the INCL4 intra-nuclear cascade and ABLA fission/evaporation models. Good agreement between the experimentally measured and calculated reaction rates was found. This serves as a good validation for the computational models and cross section data used to simulate neutron production and transport of spallation neutrons within a thermal ADS.

Laser plasma x-ray source for ultrafast time-resolved x-ray absorption spectroscopy

DOE PAGES

Miaja-Avila, L.; O'Neil, G. C.; Uhlig, J.; ...

2015-03-02

We describe a laser-driven x-ray plasma source designed for ultrafast x-ray absorption spectroscopy. The source is comprised of a 1 kHz, 20 W, femtosecond pulsed infrared laser and a water target. We present the x-ray spectra as a function of laser energy and pulse duration. Additionally, we investigate the plasma temperature and photon flux as we vary the laser energy. We obtain a 75 μm FWHM x-ray spot size, containing ~10 6 photons/s, by focusing the produced x-rays with a polycapillary optic. Since the acquisition of x-ray absorption spectra requires the averaging of measurements from >10 7 laser pulses, wemore » also present data on the source stability, including single pulse measurements of the x-ray yield and the x-ray spectral shape. In single pulse measurements, the x-ray flux has a measured standard deviation of 8%, where the laser pointing is the main cause of variability. Further, we show that the variability in x-ray spectral shape from single pulses is low, thus justifying the combining of x-rays obtained from different laser pulses into a single spectrum. Finally, we show a static x-ray absorption spectrum of a ferrioxalate solution as detected by a microcalorimeter array. Altogether, our results demonstrate that this water-jet based plasma source is a suitable candidate for laboratory-based time-resolved x-ray absorption spectroscopy experiments.« less

Satellite Observations of Rapidly Varying Cosmic X-ray Sources. Ph.D. Thesis - Catholic Univ.

NASA Technical Reports Server (NTRS)

Maurer, G. S.

1979-01-01

The X-ray source data obtained with the high energy celestial X-ray detector on the Orbiting Solar Observatory -8 are presented. The results from the 1977 Crab observation show nonstatistical fluctuations in the pulsed emission and in the structure of the integrated pulse profile which cannot be attributed to any known systematic effect. The Hercules observations presented here provide information on three different aspects of the pulsed X-ray emission: the variation of pulsed flux as a function of the time from the beginning of the ON-state, the variation of pulsed flux as a function of binary phase, and the energy spectrum of the pulse emission.

Soviet-French working group interpretation of the scientific information during the search for celestial sources of gamma pulses, abstract of reports, 24-30 March 1977

NASA Technical Reports Server (NTRS)

Estulin, I. V.

1977-01-01

The progress made and techniques used by the Soviet-French group in the study of gamma and X ray pulses are described in abstracts of 16 reports. Experiments included calibration and operation of various recording instruments designed for measurements involving these pulses, specifically the location of sources of such pulses in outer space. Space vehicles are utilized in conjunction with ground equipment to accomplish these tests.

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

Inductively generated streaming plasma ion source

DOEpatents

Glidden, Steven C.; Sanders, Howard D.; Greenly, John B.

2006-07-25

A novel pulsed, neutralized ion beam source is provided. The source uses pulsed inductive breakdown of neutral gas, and magnetic acceleration and control of the resulting plasma, to form a beam. The beam supplies ions for applications requiring excellent control of ion species, low remittance, high current density, and spatial uniformity.

Numerical investigation of a scalable setup for efficient terahertz generation using a segmented tilted-pulse-front excitation.

PubMed

Pálfalvi, László; Tóth, György; Tokodi, Levente; Márton, Zsuzsanna; Fülöp, József András; Almási, Gábor; Hebling, János

2017-11-27

A hybrid-type terahertz pulse source is proposed for high energy terahertz pulse generation. It is the combination of the conventional tilted-pulse-front setup and a transmission stair-step echelon-faced nonlinear crystal with a period falling in the hundred-micrometer range. The most important advantage of the setup is the possibility of using plane parallel nonlinear optical crystal for producing good-quality, symmetric terahertz beam. Another advantage of the proposed setup is the significant reduction of imaging errors, which is important in the case of wide pump beams that are used in high energy experiments. A one dimensional model was developed for determining the terahertz generation efficiency, and it was used for quantitative comparison between the proposed new hybrid setup and previously introduced terahertz sources. With lithium niobate nonlinear material, calculations predict an approximately ten-fold increase in the efficiency of the presently described hybrid terahertz pulse source with respect to that of the earlier proposed setup, which utilizes a reflective stair-step echelon and a prism shaped nonlinear optical crystal. By using pump pulses of 50 mJ pulse energy, 500 fs pulse length and 8 mm beam spot radius, approximately 1% conversion efficiency and 0.5 mJ terahertz pulse energy can be reached with the newly proposed setup.

Light source employing laser-produced plasma

DOEpatents

Tao, Yezheng; Tillack, Mark S

2013-09-17

A system and a method of generating radiation and/or particle emissions are disclosed. In at least some embodiments, the system includes at least one laser source that generates a first pulse and a second pulse in temporal succession, and a target, where the target (or at least a portion the target) becomes a plasma upon being exposed to the first pulse. The plasma expand after the exposure to the first pulse, the expanded plasma is then exposed to the second pulse, and at least one of a radiation emission and a particle emission occurs after the exposure to the second pulse. In at least some embodiments, the target is a solid piece of material, and/or a time period between the first and second pulses is less than 1 microsecond (e.g., 840 ns).

Fiber laser driven dual photonic crystal fiber femtosecond mid-infrared source tunable in the range of 4.2 to 9 μm

NASA Astrophysics Data System (ADS)

Yao, Yuhong; Knox, Wayne H.

2014-02-01

We report a fiber based approach to broadly tunable femtosecond mid-IR source based on difference frequency mixing of the outputs from dual photonic crystal fibers (PCF) pumped by a femtosecond fiber laser, which is a custom-built Yb-doped fiber chirped pulse amplifier (CPA) delivering 1.35 W, 300 fs, 40 MHz pulses centered at 1035 nm. The CPA output is split into two arms to pump two different types of PCFs for generation of the spectrally separated pulses. The shorter wavelength pulses are generated in one PCF with its single zero dispersion wavelength (ZDW) at 1040 nm. Low normal dispersion around the pumping wavelength enables spectral broadening dominated by self-phase modulation (SPM), which extends from 970 to 1092 nm with up to 340 mW of average power. The longer wavelength pulses are generated in a second PCF which has two closely spaced ZDWs around the laser wavelength. Facilitated by its special dispersion profile, the laser wavelength is converted to the normal dispersion region of the fiber, leading to the generation of the narrow-band intense Stokes pulses with 1 to 1.25 nJ of pulse energy at a conversion efficiency of ~30% from the laser pulses. By difference mixing the outputs from both PCFs in a type-II AgGaS2 crystal, mid-IR pulses tunable from 4.2 to 9 μm are readily generated with its average power ranging from 135 - 640 μW, corresponding to 3 - 16 pJ of pulse energy which is comparable to the reported fiber based mid-IR sources enabled by the solitons self-frequency shift (for example, 3 - 10 μm with 10 pJ of maximum pulse energy in [10]). The reported approach provides a power-scalable route to the generation of broadly tunable femtosecond mid-IR pulses, which we believe to be a promising solution for developing compact, economic and high performance mid-IR sources.

1030-nm diode-laser-based light source delivering pulses with nanojoule energies and picosecond duration adjustable by mode locking or pulse gating operation

NASA Astrophysics Data System (ADS)

Klehr, A.; Liero, A.; Wenzel, H.; Bugge, F.; Brox, O.; Fricke, J.; Ressel, P.; Knigge, A.; Heinrich, W.; Tränkle, G.

2017-02-01

A new compact 1030 nm picosecond light source which can be switched between pulse gating and mode locking operation is presented. It consists of a multi-section distributed Bragg reflector (DBR) laser, an ultrafast multisection optical gate and a flared power amplifier (PA), mounted together with high frequency electronics and optical elements on a 5×4 cm micro bench. The master oscillator (MO) is a 10 mm long ridge wave-guide (RW) laser consisting of 200 μm long saturable absorber, 1500 μm long gain, 8000 μm long cavity, 200 μm long DBR and 100 μm long monitor sections. The 2 mm long optical gate consisting of several RW sections is monolithically integrated with the 4 mm long gain-guided tapered amplifier on a single chip. The light source can be switched between pulse gating and passive mode locking operation. For pulse gating all sections of the MO (except of the DBR and monitor sections) are forward biased and driven by a constant current. By injecting electrical pulses into one section of the optical gate the CW beam emitted by the MO is converted into a train of optical pulses with adjustable widths between 250 ps and 1000 ps. Peak powers of 20 W and spectral linewidths in the MHz range are achieved. Shorter pulses with widths between 4 ps and 15 ps and peak powers up to 50 W but larger spectral widths of about 300 pm are generated by mode locking where the saturable absorber section of the MO is reversed biased. The repetition rate of 4.2 GHz of the pulse train emitted by the MO can be reduced to values between 1 kHz and 100 MHz by utilizing the optical gate as pulse picker. The pulse-to-pulse distance can be controlled by an external trigger source.

Comparison between experimental data and Monte-Carlo simulations of neutron production in spallation reactions of 0.7-1.5 GeV protons on a thick, lead target

NASA Astrophysics Data System (ADS)

Krása, A.; Majerle, M.; Krízek, F.; Wagner, V.; Kugler, A.; Svoboda, O.; Henzl, V.; Henzlová, D.; Adam, J.; Caloun, P.; Kalinnikov, V. G.; Krivopustov, M. I.; Stegailov, V. I.; Tsoupko-Sitnikov, V. M.

2006-05-01

Relativistic protons with energies 0.7-1.5 GeV interacting with a thick, cylindrical, lead target, surrounded by a uranium blanket and a polyethylene moderator, produced spallation neutrons. The spatial and energetic distributions of the produced neutron field were measured by the Activation Analysis Method using Al, Au, Bi, and Co radio-chemical sensors. The experimental yields of isotopes induced in the sensors were compared with Monte-Carlo calculations performed with the MCNPX 2.4.0 code.

Pulsed-DC DBD Plasma Actuators

NASA Astrophysics Data System (ADS)

Duong, Alan; Corke, Thomas; Thomas, Flint

2017-11-01

A power system for dielectric barrier discharge (DBD) plasma actuators that utilizes a pulsed-DC waveform is presented. The plasma actuator arrangement is identical to most typical AC-DBD designs with staggered electrodes that are separated by a dielectric insulator. A key difference is that the pulsed-DC actuator utilizes a DC voltage source to drive the actuator instead of an AC voltage input. The DC source is supplied to both electrodes. The exposed electrode remains constant in time while the encapsulated electrode is periodically grounded for short instances then is allowed to rise to the source DC level. Further investigation of the pulsed-DC plasma actuator was conducted. Time-resolved velocity measurements were done to characterize the induced velocity field generated by the pulsed-DC plasma actuator. A model of the pulsed-DC plasma actuator is developed in LTspice for further study. The work presented are intended in developing a model to be used in CFD flow control simulations. NASA SBIR NNX14CC12C.

Pulsed voltage electrospray ion source and method for preventing analyte electrolysis

DOEpatents

Kertesz, Vilmos [Knoxville, TN; Van Berkel, Gary [Clinton, TN

2011-12-27

An electrospray ion source and method of operation includes the application of pulsed voltage to prevent electrolysis of analytes with a low electrochemical potential. The electrospray ion source can include an emitter, a counter electrode, and a power supply. The emitter can include a liquid conduit, a primary working electrode having a liquid contacting surface, and a spray tip, where the liquid conduit and the working electrode are in liquid communication. The counter electrode can be proximate to, but separated from, the spray tip. The power system can supply voltage to the working electrode in the form of a pulse wave, where the pulse wave oscillates between at least an energized voltage and a relaxation voltage. The relaxation duration of the relaxation voltage can range from 1 millisecond to 35 milliseconds. The pulse duration of the energized voltage can be less than 1 millisecond and the frequency of the pulse wave can range from 30 to 800 Hz.

Pulsed Electron Source with Grid Plasma Cathode and Longitudinal Magnetic Field for Modification of Material and Product Surfaces

NASA Astrophysics Data System (ADS)

Devyatkov, V. N.; Koval, N. N.

2018-01-01

The description and the main characteristics of the pulsed electron source "SOLO" developed on the basis of the plasma cathode with grid stabilization of the emission plasma boundary are presented. The emission plasma is generated by a low-pressure arc discharge, and that allows to form the dense low-energy electron beam with a wide range of independently adjustable parameters of beam current pulses (pulse duration of 20-250 μs, pulse repetition rate of 1-10 s-1, amplitude of beam current pulses of 20-300 A, and energy of beam electrons of 5-25 keV). The special features of generation of emission plasma by constricted low-pressure arc discharge in the grid plasma cathode partially dipped into a non-uniform magnetic field and of formation and transportation of the electron beam in a longitudinal magnetic field are considered. The application area of the electron source and technologies realized with its help are specified.

Performance summary on a high power dense plasma focus x-ray lithography point source producing 70 nm line features in AlGaAs microcircuits

NASA Astrophysics Data System (ADS)

Petr, Rodney; Bykanov, Alexander; Freshman, Jay; Reilly, Dennis; Mangano, Joseph; Roche, Maureen; Dickenson, Jason; Burte, Mitchell; Heaton, John

2004-08-01

A high average power dense plasma focus (DPF), x-ray point source has been used to produce ˜70 nm line features in AlGaAs-based monolithic millimeter-wave integrated circuits (MMICs). The DPF source has produced up to 12 J per pulse of x-ray energy into 4π steradians at ˜1 keV effective wavelength in ˜2 Torr neon at pulse repetition rates up to 60 Hz, with an effective x-ray yield efficiency of ˜0.8%. Plasma temperature and electron concentration are estimated from the x-ray spectrum to be ˜170 eV and ˜5.1019 cm-3, respectively. The x-ray point source utilizes solid-state pulse power technology to extend the operating lifetime of electrodes and insulators in the DPF discharge. By eliminating current reversals in the DPF head, an anode electrode has demonstrated a lifetime of more than 5 million shots. The x-ray point source has also been operated continuously for 8 h run times at 27 Hz average pulse recurrent frequency. Measurements of shock waves produced by the plasma discharge indicate that overpressure pulses must be attenuated before a collimator can be integrated with the DPF point source.

Fast coincidence counting with active inspection systems

NASA Astrophysics Data System (ADS)

Mullens, J. A.; Neal, J. S.; Hausladen, P. A.; Pozzi, S. A.; Mihalczo, J. T.

2005-12-01

This paper describes 2nd and 3rd order time coincidence distributions measurements with a GHz processor that synchronously samples 5 or 10 channels of data from radiation detectors near fissile material. On-line, time coincidence distributions are measured between detectors or between detectors and an external stimulating source. Detector-to-detector correlations are useful for passive measurements also. The processor also measures the number of times n pulses occur in a selectable time window and compares this multiplet distribution to a Poisson distribution as a method of determining the occurrence of fission. The detectors respond to radiation emitted in the fission process induced internally by inherent sources or by external sources such as LINACS, DT generators either pulsed or steady state with alpha detectors, etc. Data can be acquired from prompt emission during the source pulse, prompt emissions immediately after the source pulse, or delayed emissions between source pulses. These types of time coincidence measurements (occurring on the time scale of the fission chain multiplication processes for nuclear weapons grade U and Pu) are useful for determining the presence of these fissile materials and quantifying the amount, and are useful for counter terrorism and nuclear material control and accountability. This paper presents the results for a variety of measurements.