Science.gov

Sample records for spallation neutron emission

  1. Pulsed spallation Neutron Sources

    SciTech Connect

    Carpenter, J.M.

    1994-12-31

    This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provides a few examples of applications in fundamental condensed matter physics, materials science and technology.

  2. Pulsed spallation neutron sources

    SciTech Connect

    Carpenter, J.M.

    1996-05-01

    This paper reviews the early history of pulsed spallation neutron source development ar Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provide a few examples of applications in fundamental condensed matter physics, materials science and technology.

  3. Materials for spallation neutron sources

    SciTech Connect

    Sommer, W.F.; Daemen, L.L.

    1996-03-01

    The Workshop on Materials for Spallation Neutron Sources at the Los Alamos Neutron Science Center, February 6 to 10, 1995, gathered scientists from Department of Energy national laboratories, other federal institutions, universities, and industry to discuss areas in which work is needed, successful designs and use of materials, and opportunities for further studies. During the first day of the workshop, speakers presented overviews of current spallation neutron sources. During the next 3 days, seven panels allowed speakers to present information on a variety of topics ranging from experimental and theoretical considerations on radiation damage to materials safety issues. An attempt was made to identify specific problems that require attention within the context of spallation neutron sources. This proceedings is a collection of summaries from the overview sessions and the panel presentations.

  4. Neutron spallation sources in Europe

    NASA Astrophysics Data System (ADS)

    Bryant, P. J.

    1996-11-01

    After a brief general and historical discussion, the main design features of spallation sources are described. At the present time, Europe not only has the world-leading pulsed neutron spallation source, the SNS-ISIS at RAL, UK, but it is on the point of commissioning a world-leading continuous cyclotron-driven source, the SINQ at PSI, Switzerland. Looking to the future, yet more powerful pulsed sources are actively under study and the difficult problem of high-power target design (>250 kW) is leading to a new technology for liquid targets. The accelerator designs, although basically classical, require custom-built solutions that are often at the limit of present day accelerator technology.

  5. Neutron spallation sources in Europe

    NASA Astrophysics Data System (ADS)

    Bryant, P. J.

    1996-11-01

    After a brief general and historical discussion, the main design features of spallation sources are described. At the present time, Europe not only has the world-leading pulsed neutron spallation source, the SNS-ISIS at RAL, UK, but it is on the point of commissioning a world-leading continuous cyclotron-driven source, the SINQ at PSI, Switzerland. Looking to the future, yet more powerful pulsed sources are actively under study and the difficult problem of high-power target design (>250 kW) is leading to a new technology for liquid targets. The accelerator designs, although basically classical, require custom-built solutions that are often at the limit of presentday accelerator technology.

  6. Spallation Neutron Source reaches megawatt power

    ScienceCinema

    Dr. William F. Brinkman

    2010-01-08

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

  7. Dose measurements around spallation neutron sources.

    PubMed

    Fragopoulou, M; Stoulos, S; Manolopoulou, M; Krivopustov, M; Zamani, M

    2008-01-01

    Neutron dose measurements and calculations around spallation sources appear to be of great importance in shielding research. Two spallation sources were irradiated by high-energy proton beams delivered by the Nuclotron accelerator (JINR), Dubna. Neutrons produced by the spallation sources were measured by using solid-state nuclear track detectors. In addition, neutron dose was calculated after polyethylene and concrete, using a phenomenological model based on empirical relations applied in high-energy physics. The study provides an analytical and experimental neutron benchmark analysis using the transmission factor and a comparison between the experimental results and calculations. PMID:18957519

  8. Spallation Neutron Source reaches megawatt power

    SciTech Connect

    Dr. William F. Brinkman

    2009-09-30

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

  9. Plasma emission spectroscopy for operating and developing the Spallation Neutron Source (SNS) H(-) ion sources.

    PubMed

    Han, B X; Welton, R F; Murray, S N; Pennisi, T R; Santana, M; Stockli, M P

    2014-02-01

    A RF-driven, Cs-enhanced H(-) ion source feeds the SNS accelerator with a high current (typically >50 mA), ∼1.0 ms pulsed beam at 60 Hz. To achieve the persistent high current beam for several weeks long service cycles, each newly installed ion source undergoes a rigorous conditioning and cesiation processes. Plasma conditioning outgases the system and sputter-cleans the ion conversion surfaces. A cesiation process immediately following the plasma conditioning releases Cs to provide coverage on the ion conversion surfaces. The effectiveness of the ion source conditioning and cesiation is monitored with plasma emission spectroscopy using a high-sensitivity optical spectrometer. Plasma emission spectroscopy is also used to provide a means for diagnosing and confirming a failure of the insulating coating of the ion source RF antenna which is immersed in the plasma. Emissions of composition elements of the antenna coating material, Na emission being the most significant, drastically elevate to signal a failure when it happens. Plasma spectra of the developmental ion source with an AlN (aluminum nitrite) chamber and an external RF antenna are also briefly discussed. PMID:24593570

  10. Plasma emission spectroscopy for operating and developing the Spallation Neutron Source (SNS) H- ion sources

    SciTech Connect

    Han, Baoxi; Welton, Robert F; Murray Jr, S N; Pennisi, Terry R; Santana, Manuel; Stockli, Martin P

    2014-01-01

    An RF-driven, Cs-enhanced H- ion source feeds the SNS accelerator with a high current (typically >50 mA), ~1.0 ms pulsed beam at 60 Hz. To achieve the persistent high current beam for several weeks long service cycles, each newly installed ion source undergoes a rigorous conditioning and cesiation processes. Plasma conditioning outgases the system and sputter-cleans the ion conversion surfaces. A cesiation process immediately following the plasma conditioning releases Cs to provide coverage on the ion conversion surfaces. The effectiveness of the ion source conditioning and cesiation is monitored with plasma emission spectroscopy using a high-sensitivity optical spectrometer. Plasma emission spectroscopy is also used to provide a mean for diagnosing and confirming a failure of the insulating coating of the ion source RF antenna which is immersed in the plasma. Emissions of composition elements of the antenna coating material, Na emission being the most significant, drastically elevate to signal a failure when it happens. Plasma spectra of the developmental ion source with an AlN chamber and an external RF antenna are also briefly discussed.

  11. Physics and technology of spallation neutron sources

    NASA Astrophysics Data System (ADS)

    Bauer, G. S.

    2001-05-01

    A substantial body of research is necessary in order to be able to make reliable predictions on the performance and safety of Accelerator Driven Systems (ADS), in particular of their spallation targets. So far, practical experience has resulted from the development of research neutron sources only. Next to fission and fusion, spallation is an efficient process for releasing neutrons from nuclei. Unlike the other two reactions, it is an endothermal process and can, therefore, not be used per se in energy generation. In order to sustain a spallation reaction, an energetic beam of particles, most commonly protons, must be supplied onto a heavy target. Spallation can, however, play an important role as a source of neutrons whose flux can be easily controlled via the driving beam. Although sophisticated Monte Carlo codes exist to compute all aspects of a spallation facility, many features can be understood on the basis of simple physics arguments. Technically a spallation facility is very demanding, not only because a reliable and economic accelerator of high power is needed to drive the reaction, but also, and in particular, because high levels of radiation and heat are generated in the target which are difficult to cope with. Radiation effects in a spallation environment are different from those commonly encountered in a reactor and are probably even more temperature dependent than the latter because of the high gas production rate. A commonly favored solution is the use of molten heavy metal targets. While radiation damage is not a problem in this case, except for the container, other issues need to be considered. R&D carried out for the development of spallation neutron sources will thus be beneficial also directly for ADS.

  12. Basic physics with spallation-neutron sources

    SciTech Connect

    Michaudon, A.F.

    1994-05-01

    The neutron has unique intrinsic properties widely used in basic and applied sciences. The neutron plays a well-known role in applied sciences and technology and is a unique probe well suited for the exploration of condensed-matter properties. But the neutron is also used for many other basic-physics studies, including nuclear physics, particle physics, fundamental physics, astrophysics, and cosmology. These last studies are briefly reviewed in this paper. Spallation-neutron sources today have unmatched neutron-beam properties for such studies and have great potential in future technological developments whereby these studies could be carried out under much improved conditions.

  13. A National Spallation Neutron Source for neutron scattering

    SciTech Connect

    Appleton, B.R.

    1996-10-01

    The National Spallation Neutron Source is a collaborative project or perform the conceptual design for a next generation neutron source for the Department of Energy. This paper reviews the need and justification for a new neutron source, the origins and structure of the collaboration formed to address this need, and the community input leading up to the current design approach. A reference design is presented for an accelerator based spallation neutron source that would begin operation at about 1 megawatt of power but designed so that it could be upgraded to significantly higher powers in the future. The technology approach, status, and progress on the conceptual design to date are presented.

  14. INJECTION CHOICE FOR SPALLATION NEUTRON SOURCE RING.

    SciTech Connect

    WEI,J.; BEEBE-WANG,J.; BLASKIEWICZ,M.; BRODOWSKI,J.; FEDOTOV,A.; GARDNER,C.; LEE,Y.Y.; RAPARIA,D.; DANILOV,V.; HOLMES,J.; PRIOR,C.; REES,G.; MACHIDA,S.

    2001-06-18

    Injection is key in the low-loss design of high-intensity proton facilities like the Spallation Neutron Source (SNS). During the design of both the accumulator and the rapid-cycling-synchrotron version of the SNS, extensive comparison has been made to select injection scenarios that satisfy SNS's low-loss design criteria. This paper presents issues and considerations pertaining to the final choice of the SNS injection systems.

  15. COHERENT at the Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Raybern, Justin; Scholberg, Kate

    2015-04-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, Tennessee, provides an intense isotropic flux of neutrinos in the few tens-of-MeV range, with a sharply-pulsed timing structure which is beneficial for background rejection. This talk will describe how the SNS source can be used for a measurement of coherent elastic neutrino-nucleus scattering (CEvNS), the physics reach of such a measurement, and the status of COHERENT, the planned experimental program.

  16. COHERENT at the Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Scholberg, Kate; Coherent Collaboration

    2016-03-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, Tennessee, provides an intense isotropic flux of neutrinos in the few tens-of-MeV range, with a sharply-pulsed timing structure which is beneficial for background rejection. This talk will describe aspects of COHERENT, the experimental program underway to measure CEvNS (Coherent Elastic Neutrino-Nucleus Scattering) using low-energy nuclear recoil detectors.

  17. Linac-driven spallation-neutron source

    SciTech Connect

    Jason, A.J.

    1995-05-01

    Strong interest has arisen in accelerator-driven spallation-neutron sources that surpass existing facilities (such as ISIS at Rutherford or LANSCE at Los Alamos) by more than an order of magnitude in beam power delivered to the spallation target. The approach chosen by Los Alamos (as well as the European Spallation Source) provides the full beam energy by acceleration in a linac as opposed to primary acceleration in a synchrotron or other circular device. Two modes of neutron production are visualized for the source. A short-pulse mode produces 1 MW of beam power (at 60 pps) in pulses, of length less than 1 ms, by compression of the linac macropulse through multi-turn injection in an accumulator ring. A long-pulse mode produces a similar beam power with 1-ms-long pulses directly applied to a target. This latter mode rivals the performance of existing reactor facilities to very low neutron energies. Combination with the short-pulse mode addresses virtually all applications.

  18. Status Report on the Spallation Neutron Source

    SciTech Connect

    Gabriel, T.A.

    1998-10-12

    The purpose of the Spallation Neutron Source Project (SNS) is to generate low-energy neutrons (ambient [{approximately}200 meV] and cold [{approximately}50 meV]) which can be used by up to 18 neutron beam lines to study the structure and functionality of materials. The neutrons are generated by the spallation process initiated by the interactions of 1-GeV protons with a Hg target. These neutrons are reflected by a Pb reflector and are moderated by 2 water (ambient) and 2 super critical hydrogen (cryogenic) moderators. The pulse structure for the 1 MW proton beam is 60 Hertz and < 0.7 {micro}s/pulse. The facility must be upgradable to higher power levels (2- and 4- MW) with minimal operational interruptions. Although not included in the current funding or baseline, a second target station and associated support structure which will be designed to utilize cold neutrons is also considered to be an upgrade that must be incorporated with minimal impact on operations.

  19. Neutron scattering instrumentation for biology at spallation neutron sources

    SciTech Connect

    Pynn, R.

    1994-12-31

    Conventional wisdom holds that since biological entities are large, they must be studied with cold neutrons, a domain in which reactor sources of neutrons are often supposed to be pre-eminent. In fact, the current generation of pulsed spallation neutron sources, such as LANSCE at Los Alamos and ISIS in the United Kingdom, has demonstrated a capability for small angle scattering (SANS) - a typical cold- neutron application - that was not anticipated five years ago. Although no one has yet built a Laue diffractometer at a pulsed spallation source, calculations show that such an instrument would provide an exceptional capability for protein crystallography at one of the existing high-power spoliation sources. Even more exciting is the prospect of installing such spectrometers either at a next-generation, short-pulse spallation source or at a long-pulse spallation source. A recent Los Alamos study has shown that a one-megawatt, short-pulse source, which is an order of magnitude more powerful than LANSCE, could be built with today`s technology. In Europe, a preconceptual design study for a five-megawatt source is under way. Although such short-pulse sources are likely to be the wave of the future, they may not be necessary for some applications - such as Laue diffraction - which can be performed very well at a long-pulse spoliation source. Recently, it has been argued by Mezei that a facility that combines a short-pulse spallation source similar to LANSCE, with a one-megawatt, long-pulse spallation source would provide a cost-effective solution to the global shortage of neutrons for research. The basis for this assertion as well as the performance of some existing neutron spectrometers at short-pulse sources will be examined in this presentation.

  20. Neutron science opportunities at pulsed spallation neutron sources

    SciTech Connect

    Carpenter, J.M.

    1996-12-31

    Using the IPNS Upgrade plan developed at Argonne National Laboratory as a worked example of the design of a pulsed spallation neutron source, this paper explores some of the scientific applications of an advanced facility for materials science studies and the instrumentation for those purposes.

  1. Spallation neutron source beam loss monitor system

    NASA Astrophysics Data System (ADS)

    Gassner, D.; Witkover, R.; Cameron, P.; Power, J.

    2000-11-01

    The Spallation Neutron Source facility to be built at ORNL is designed to accumulate 2×1014 protons at 1.0 GeV and deliver them to the experimental target in one bunch at 60 Hz. To achieve this goal and protect the machine from excessive radiation activation, an uncontrolled loss criteria of 1 part in 104 (1 W/m) has been specified. Measured losses will be conditioned to provide machine tuning data, a beam abort trigger, and logging of loss history. The design of the distributed loss monitor system utilizing argon-filled glass ionization chambers and scintillator-photomultipliers will be presented.

  2. Neutronic moderator design for the Spallation Neutron Source (SNS)

    SciTech Connect

    Charlton, L.A.; Barnes, J.M.; Johnson, J.O.; Gabriel, T.A.

    1998-11-01

    Neutronics analyses are now in progress to support the initial selection of moderator design parameters for the Spallation Neutron Source (SNS). The results of the initial optimization studies involving moderator poison plate location, moderator position, and premoderator performance for the target system are presented in this paper. Also presented is an initial study of the use of a composite moderator to produce a liquid methane like spectrum.

  3. The Fundamental Neutron Physics Beamline at the Spallation Neutron Source

    PubMed Central

    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. PMID:27308112

  4. A multitask neutron beam line for spallation neutron sources

    NASA Astrophysics Data System (ADS)

    Pietropaolo, A.; Festa, G.; Grazzi, F.; Barzagli, E.; Scherillo, A.; Schooneveld, E. M.; Civita, F.

    2011-08-01

    Here we present a new concept for a time-of-flight neutron scattering instrument allowing for simultaneous application of three different techniques: time-of-flight neutron diffraction, neutron resonance capture analysis and Bragg edge transmission analysis. The instrument can provide average resolution neutron radiography too. The potential of the proposed concept was explored by implementing the necessary equipment on INES (Italian Neutron Experimental Station) at the ISIS spallation neutron source (UK). The results obtained show the effectiveness of the proposed instrument to acquire relevant quantitative information in a non-invasive way on a historical metallurgical sample, namely a Japanese hand guard (tsuba). The aforementioned neutron techniques simultaneously exploited the extended neutron energy range available from 10 meV to 1 keV. This allowed a fully satisfactory characterization of the sample in terms of metal components and their combination in different phases, and forging and assembling methods.

  5. Using spallation neutron sources for defense research

    SciTech Connect

    Pynn, R.; Sterbenz, S.M.; Weinacht, D.J.

    1996-12-31

    Advanced characterization techniques and accelerated simulation are the cornerstones of the Energy Department`s science-based program to maintain confidence in the safety, reliability, and performance of the US nuclear deterrent in an era of no nuclear testing. Neutrons and protons provided by an accelerator-based facility have an important role to play in this program, impacting several of the key stockpile stewardship and management issues identified by the Department of Defense. Many of the techniques used for defense research at a spallation source have been used for many years for the basic research community, and to a lesser extent by industrial scientists. By providing access to a broad spectrum of researchers with different backgrounds, a spallation source such as the Los Alamos Neutron Science Center is able to promote synergistic interaction between defense, basic and industrial researchers. This broadens the scientific basis of the stockpile stewardship program in the short term and will provide spin-off to industrial and basic research in the longer term.

  6. Determination of spallation neutron flux through spectral adjustment techniques

    NASA Astrophysics Data System (ADS)

    Mosby, M. A.; Engle, J. W.; Jackman, K. R.; Nortier, F. M.; Birnbaum, E. R.

    2016-08-01

    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. However, the energy distribution and magnitude of the flux is not well understood. 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.

  7. Slow neutron leakage spectra from spallation neutron sources

    SciTech Connect

    Das, S.G.; Carpenter, J.M.; Prael, R.E.

    1980-02-01

    An efficient technique is described for Monte Carlo simulation of neutron beam spectra from target-moderator-reflector assemblies typical of pulsed spallation neutron sources. The technique involves the scoring of the transport-theoretical probability that a neutron will emerge from the moderator surface in the direction of interest, at each collision. An angle-biasing probability is also introduced which further enhances efficiency in simple problems. These modifications were introduced into the VIM low energy neutron transport code, representing the spatial and energy distributions of the source neutrons approximately as those of evaporation neutrons generated through the spallation process by protons of various energies. The intensity of slow neutrons leaking from various reflected moderators was studied for various neutron source arrangements. These include computations relating to early measurements on a mockup-assembly, a brief survey of moderator materials and sizes, and a survey of the effects of varying source and moderator configurations with a practical, liquid metal cooled uranium source Wing and slab, i.e., tangential and radial moderator arrangements, and Be vs CH/sub 2/ reflectors are compared. Results are also presented for several complicated geometries which more closely represent realistic arrangements for a practical source, and for a subcritical fission multiplier such as might be driven by an electron linac. An adaptation of the code was developed to enable time dependent calculations, and investigated the effects of the reflector, decoupling and void liner materials on the pulse shape.

  8. Synchrotron based spallation neutron source concepts

    SciTech Connect

    Cho, Y.

    1998-07-01

    During the past 20 years, rapid-cycling synchrotrons (RCS) have been used very productively to generate short-pulse thermal neutron beams for neutron scattering research by materials science communities in Japan (KENS), the UK (ISIS) and the US (IPNS). The most powerful source in existence, ISIS in the UK, delivers a 160-kW proton beam to a neutron-generating target. Several recently proposed facilities require proton beams in the MW range to produce intense short-pulse neutron beams. In some proposals, a linear accelerator provides the beam power and an accumulator ring compresses the pulse length to the required {approx} 1 {micro}s. In others, RCS technology provides the bulk of the beam power and compresses the pulse length. Some synchrotron-based proposals achieve the desired beam power by combining two or more synchrotrons of the same energy, and others propose a combination of lower and higher energy synchrotrons. This paper presents the rationale for using RCS technology, and a discussion of the advantages and disadvantages of synchrotron-based spallation sources.

  9. BNL feasibility studies of spallation neutron sources

    SciTech Connect

    Lee, Y.Y.; Ruggiero, A.G.; Van Steenbergen, A.; Weng, W.T.

    1995-12-01

    This paper is the summary of conceptual design studies of a 5 MW Pulsed Spallation Neutron Source (PSNS) conducted by an interdepartmental study group at Brookhaven National Laboratory. The study was made of two periods. First, a scenario based on the use of a 600 MeV Linac followed by two fast-cycling 3.6 GeV Synchrotrons was investigated. Then, in a subsequent period, the attention of the study was directed toward an Accumulator scenario with two options: (1) a 1.25 GeV normal conducting Linac followed by two Accumulator Rings, and (2) a 2.4 GeV superconducting Linac followed by a single Accumulator Ring. The study did not make any reference to a specific site.

  10. SPALLATION NEUTRON SOURCE BEAM CURRENT MONITOR ELECTRONICS.

    SciTech Connect

    KESSELMAN,M.; DAWSON,W.C.

    2002-05-06

    This paper will discuss the present electronics design for the beam current monitor system to be used throughout the Spallation Neutron Source (SNS) under construction at Oak Ridge National Laboratory. The beam is composed of a micro-pulse structure due to the 402.5MHz RF, and is chopped into mini-pulses of 645ns duration with a 300ns gap, providing a macro-pulse of 1060 mini-pulses repeating at a 60Hz rate. Ring beam current will vary from about 15ma peak during studies, to about 50Amps peak (design to 100 amps). A digital approach to droop compensation has been implemented and initial test results presented.

  11. PREFACE: Neutrino physics at spallation neutron sources

    NASA Astrophysics Data System (ADS)

    Avignone, F. T.; Chatterjee, L.; Efremenko, Y. V.; Strayer, M.

    2003-11-01

    Unique because of their super-light masses and tiny interaction cross sections, neutrinos combine fundamental physics on the scale of the miniscule with macroscopic physics on the scale of the cosmos. Starting from the ignition of the primal p-p chain of stellar and solar fusion reactions that signal star-birth, these elementary leptons (neutrinos) are also critical players in the life-cycles and explosive deaths of massive stars and the production and disbursement of heavy elements. Stepping beyond their importance in solar, stellar and supernova astrophysics, neutrino interactions and properties influence the evolution, dynamics and symmetries of the cosmos as a whole. Further, they serve as valuable probes of its material content at various levels of structure from atoms and nuclei to valence and sea quarks. In the light of the multitude of physics phenomena that neutrinos influence, it is imperative to enhance our understanding of neutrino interactions and properties to the maximum. This is accentuated by the recent evidence of finite neutrino mass and flavour mixing between generations that reverberates on the plethora of physics that neutrinos influence. Laboratory experiments using intense neutrino fluxes would allow precision measurements and determination of important neutrino reaction rates. These can then complement atmospheric, solar and reactor experiments that have enriched so valuably our understanding of the neutrino and its repertoire of physics applications. In particular, intermediate energy neutrino experiments can provide critical information on stellar and solar astrophysical processes, along with advancing our knowledge of nuclear structure, sub-nuclear physics and fundamental symmetries. So where should we look for such intense neutrino sources? Spallation neutron facilities by their design are sources of intense neutrino pulses that are produced as a by-product of neutron spallation. These neutrino sources could serve as unique laboratories

  12. The European scene regarding spallation neutron sources

    SciTech Connect

    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 and 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.

  13. Neutronic Design Studies for the National Spallation Neutron Source (NSNS)

    SciTech Connect

    Charlton, LA

    2001-08-01

    Neutronics analyses are now in progress to support initial selection of target system design features, materials, geometry, and component sizes for the proposed Spallation Neutron Source (SNS). Calculations have been performed to determine the neutron, proton, heavy ion, and gamma-ray flux spectra as a function of time, energy, and space for the major components of the target station (target, moderators, reflectors, etc.). These analyses were also performed to establish an initial set of performance characteristics for the neutron source. The methodology, reference performance characteristics, and results of initial optimization studies involving moderator poison plate location, target material performance, reflector performance, moderator position and premoderator performance for the target system are presented in this paper.

  14. European Spallation Source and Neutron Science

    NASA Astrophysics Data System (ADS)

    Yeck, James

    2014-03-01

    International collaborations in large-scale scientific projects can link Sciences and Society. Following this goal, 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. Scandinavia is providing 50 percent of the construction cost whilst the other member states are providing financial support mainly via in-kind contribution from institutes, laboratories or industries of the given countries. Scientists and engineers from 35 different countries are members of the workforce in Lund who participate in its design and construction. The ESS will enable new opportunities for researchers in fields of life sciences, energy, environmental technology, cultural heritage and fundamental physics by producing very high flux neutrons to study condensed matter physics, chemistry, biology, nuclear physics and materials science. The ESS will be up to 30 times brighter than today's leading facilities and neutron sources. A tungsten target and a 5 MW long pulse proton accelerator, composed mainly of superconducting Radio-Frequency components, are used to achieve these goals.

  15. 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.

  16. Plasma emission spectroscopy for operating and developing the Spallation Neutron Source (SNS) H{sup −} ion sources

    SciTech Connect

    Han, B. X. Welton, R. F.; Murray, S. N.; Pennisi, T. R.; Santana, M.; Stockli, M. P.

    2014-02-15

    A RF-driven, Cs-enhanced H{sup −} ion source feeds the SNS accelerator with a high current (typically >50 mA), ∼1.0 ms pulsed beam at 60 Hz. To achieve the persistent high current beam for several weeks long service cycles, each newly installed ion source undergoes a rigorous conditioning and cesiation processes. Plasma conditioning outgases the system and sputter-cleans the ion conversion surfaces. A cesiation process immediately following the plasma conditioning releases Cs to provide coverage on the ion conversion surfaces. The effectiveness of the ion source conditioning and cesiation is monitored with plasma emission spectroscopy using a high-sensitivity optical spectrometer. Plasma emission spectroscopy is also used to provide a means for diagnosing and confirming a failure of the insulating coating of the ion source RF antenna which is immersed in the plasma. Emissions of composition elements of the antenna coating material, Na emission being the most significant, drastically elevate to signal a failure when it happens. Plasma spectra of the developmental ion source with an AlN (aluminum nitrite) chamber and an external RF antenna are also briefly discussed.

  17. China Spallation Neutron Source: Design, R&D, and outlook

    NASA Astrophysics Data System (ADS)

    Wei, Jie; Chen, Hesheng; Chen, Yanwei; Chen, Yuanbo; Chi, Yunlong; Deng, Changdong; Dong, Haiyi; Dong, Lan; Fang, Shouxian; Feng, Ji; Fu, Shinian; He, Lunhua; He, Wei; Heng, Yuekun; Huang, Kaixi; Jia, Xuejun; Kang, Wen; Kong, Xiangcheng; Li, Jian; Liang, Tianjiao; Lin, Guoping; Liu, Zhenan; Ouyang, Huafu; Qin, Qing; Qu, Huamin; Shi, Caitu; Sun, Hong; Tang, Jingyu; Tao, Juzhou; Wang, Chunhong; Wang, Fangwei; Wang, Dingsheng; Wang, Qingbin; Wang, Sheng; Wei, Tao; Xi, Jiwei; Xu, Taoguang; Xu, Zhongxiong; Yin, Wen; Yin, Xuejun; Zhang, Jing; Zhang, Zong; Zhang, Zonghua; Zhou, Min; Zhu, Tao

    2009-02-01

    The China Spallation Neutron Source (CSNS) is an accelerator based multidiscipline user facility planned to be constructed in Dongguan, Guangdong, China. The CSNS complex consists of an negative hydrogen linear accelerator, a rapid cycling proton synchrotron accelerating the beam to 1.6 GeV energy, a solid tungsten target station, and instruments for spallation neutron applications. The facility operates at 25 Hz repetition rate with an initial design beam power of 120 kW and is upgradeable to 500 kW. The primary challenge is to build a robust and reliable user's facility with upgrade potential at a fraction of "world standard" cost. We report the status, design, R&D, and upgrade outlook including applications using spallation neutron, muon, fast neutron, and proton, as well as related programs including medical therapy and accelerator-driven sub-critical reactor (ADS) programs for nuclear waste transmutation.

  18. Split-target neutronics and the MLNSC spallation target system

    SciTech Connect

    Russell, G.J.; Ferguson, P.D.; Pitcher, E.J.; Court, J.D.

    1996-12-31

    The Manuel Lujan, Jr., Neutron Scattering Center (MLNSC) at the Los Alamos National Laboratory is one of four operating Short-Pulse Spallation Sources worldwide. The MLNSC target system (composed of targets, moderators, and reflectors) was first installed in 1985. The target system employs a split tungsten spallation target with a void space in between (the flux-trap gap); this target system will be upgraded in 1998. The ability to efficiently split a spallation target allowed us to introduce the concept of flux-trap moderators and ultimately the notion of backscattering and upstream moderators. The upgraded MLNSC target system will employ both flux-trap and upstream/backscattering moderators to simultaneously service 16 neutron flight paths with high-intensity neutron beams for materials science research.

  19. 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)

  20. Modeling of water radiolysis at spallation neutron sources

    SciTech Connect

    Daemen, L.L.; Kanner, G.S.; Lillard, R.S.; Butt, D.P.; Brun, T.O.; Sommer, W.F.

    1998-12-01

    In spallation neutron sources neutrons are produced when a beam of high-energy particles (e.g., 1 GeV protons) collides with a (water-cooled) heavy metal target such as tungsten. The resulting spallation reactions produce a complex radiation environment (which differs from typical conditions at fission and fusion reactors) leading to the radiolysis of water molecules. Most water radiolysis products are short-lived but extremely reactive. When formed in the vicinity of the target surface they can react with metal atoms, thereby contributing to target corrosion. The authors will describe the results of calculations and experiments performed at Los Alamos to determine the impact on target corrosion of water radiolysis in the spallation radiation environment. The computational methodology relies on the use of the Los Alamos radiation transport code, LAHET, to determine the radiation environment, and the AEA code, FACSIMILE, to model reaction-diffusion processes.

  1. Neutrino Cross-Section Measurements at the Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Stancu, Ion

    2008-02-01

    In this paper we discuss the proposal to build a neutrino facility at the recently-completed Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL). This facility can host an extensive, long-term program to study neutrino-nucleus cross-sections in the range of interest for nuclear astrophysics and nuclear theory.

  2. Opportunities for Neutrino Physics at the Spallation Neutron Source (SNS)

    SciTech Connect

    Efremenko, Yuri; Hix, William Raphael

    2009-01-01

    In this paper we discuss opportunities for a neutrino program at the Spallation Neutrons Source (SNS) being commissioning at ORNL. Possible investigations can include study of neutrino-nuclear cross sections in the energy rage important for supernova dynamics and neutrino nucleosynthesis, search for neutrino-nucleus coherent scattering, and various tests of the standard model of electro-weak interactions.

  3. Post irradiation examination of the Spallation Neutron Source target vessels

    SciTech Connect

    McClintock, David A; Ferguson, Phillip D; Mansur, Louis K

    2010-01-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is an accelerator-based pulsed neutron source that produces high-energy spallation neutrons by bombarding liquid mercury flowing through a stainless steel target vessel. During operation the proton beam and spallation neutrons produce radiation damage in the AISI 316L austenitic stainless steel target vessel and water-cooled shroud. The beam pulses also cause rapid heating of the liquid mercury, which may produce cavitation erosion damage on the inner surface of the target vessel. The cavitation erosion rate is thought to be highly sensitive to beam power and predicted to be the primary life-limiting factor of target vessel. Though mitigation of cavitation erosion and radiation damage to the target vessel will be a critical for successful high-power operation of the SNS facility, the effects of radiation damage and cavitation erosion to target vessels in liquid metal spallation systems are not well known. Therefore preparations are being undertaken to perform post irradiation examination (PIE) of the liquid mercury target vessel and water-cooled shroud after end-of-life occurs. An overview of the planned PIE for the SNS target vessel is presented here, including proposed techniques for specimen acquisition and subsequent material properties characterization.

  4. The Spallation Neutron Source and the Neutrino Physics Program

    SciTech Connect

    Stancu, Ion

    2008-02-21

    In this paper we describe the recently-completed Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL), along with a proposed long-term neutrino physics program to study neutrino-nucleus cross-sections and neutrino oscillations.

  5. Neutrino Cross-Section Measurements at the Spallation Neutron Source

    SciTech Connect

    Stancu, Ion

    2008-02-21

    In this paper we discuss the proposal to build a neutrino facility at the recently-completed Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL). This facility can host an extensive, long-term program to study neutrino-nucleus cross-sections in the range of interest for nuclear astrophysics and nuclear theory.

  6. Neutron diffractometers for structural biology at spallation neutron sources

    SciTech Connect

    Schoenborn, B.P.; Pitcher, E.

    1994-12-31

    Spallation neutron sources are ideal for diffraction studies of proteins and oriented molecular complexes. With spoliation neutrons and their time dependent wavelength structure, it is easy to electronically select data with an optimal wavelength bandwidth and cover the whole Laue spectrum as time (wavelength) resolved snapshots. This optimized data quality with best peak-to-background ratios and provides adequate spatial and energy resolution to eliminate peak overlaps. The application of this concept will use choppers to select the desired Laue wavelength spectrum and employ focusing optics and large cylindrical {sup 3}He detectors to optimize data collection rates. Such a diffractometer will cover a Laue wavelength range from 1 to 5{Angstrom} with a flight path length of 10m and an energy resolution of 0.25{Angstrom}. Moderator concepts for maximal flux distribution within this energy range will be discussed using calculated flux profiles. Since the energy resolution required for such timed data collection in this super Laue techniques is not very high, the use of a linac only (LAMPF) spoliation target is an exciting possibility with an order of magnitude increase in flux.

  7. Spallation neutron source target station design, development, and commissioning

    NASA Astrophysics Data System (ADS)

    Haines, J. R.; McManamy, T. J.; Gabriel, T. A.; Battle, R. E.; Chipley, K. K.; Crabtree, J. A.; Jacobs, L. L.; Lousteau, D. C.; Rennich, M. J.; Riemer, B. W.

    2014-11-01

    The spallation neutron source target station is designed to safely, reliably, and efficiently convert a 1 GeV beam of protons to a high flux of about 1 meV neutrons that are available at 24 neutron scattering instrument beam lines. Research and development findings, design requirements, design description, initial checkout testing, and results from early operation with beam are discussed for each of the primary target subsystems, including the mercury target, neutron moderators and reflector, surrounding vessels and shielding, utilities, remote handling equipment, and instrumentation and controls. Future plans for the mercury target development program are also briefly discussed.

  8. BEAM LOSS MITIGATION IN THE OAK RIDGE SPALLATION NEUTRON SOURCE

    SciTech Connect

    Plum, Michael A

    2012-01-01

    The Oak Ridge Spallation Neutron Source (SNS) accelerator complex routinely delivers 1 MW of beam power to the spallation target. Due to this high beam power, understanding and minimizing the beam loss is an ongoing focus area of the accelerator physics program. In some areas of the accelerator facility the equipment parameters corresponding to the minimum loss are very different from the design parameters. In this presentation we will summarize the SNS beam loss measurements, the methods used to minimize the beam loss, and compare the design vs. the loss-minimized equipment parameters.

  9. Material issues relating to high power spallation neutron sources

    NASA Astrophysics Data System (ADS)

    Futakawa, M.

    2015-02-01

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

  10. Protein structures by spallation neutron crystallography

    PubMed Central

    Langan, Paul; Fisher, Zoë; Kovalevsky, Andrii; Mustyakimov, Marat; Sutcliffe Valone, Amanda; Unkefer, Cliff; Waltman, Mary Jo; Coates, Leighton; Adams, Paul D.; Afonine, Pavel V.; Bennett, Brad; Dealwis, Chris; Schoenborn, Benno P.

    2008-01-01

    The Protein Crystallography Station at Los Alamos Neutron Science Center is a high-performance beamline that forms the core of a capability for neutron macromolecular structure and function determination. This capability also includes the Macromolecular Neutron Crystallography (MNC) consortium between Los Alamos (LANL) and Lawrence Berkeley National Laboratories for developing computational tools for neutron protein crystallography, a biological deuteration laboratory, the National Stable Isotope Production Facility, and an MNC drug design consortium between LANL and Case Western Reserve University. PMID:18421142

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

    SciTech Connect

    Grusell, E.; Conde, H.; Larsson, B.; Roennqvist, T.; Sornsuntisook, O.; Crawford, J.; Reist, H.; Dahl, B.; Sjoestrand, N.G.; Russel, G. . Dept. of Radiation Sciences; Paul Scherrer Inst. , Villigen; Chalmers Univ. of Tech., Goeteborg . Dept. of Reactor Physics; Los Alamos National Lab., NM )

    1989-01-01

    Spallation is induced in a heavy material by 72 MeV protons. The hereby produced neutrons with essentially an evaporation spectrum with a peak energy of less than 2 MeV 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 show a good agreement and also show that useful thermal neutron fluences are attainable in the depth of the brain, at proton currents of less than 0.5 mA. 3 refs., 5 figs., 4 tabs.

  12. Towards detectors for next generation spallation neutron sources

    NASA Astrophysics Data System (ADS)

    Gebauer, B.

    2004-12-01

    Neutron scattering and diffraction methods are of utmost importance for probing the structure and dynamics of condensed matter at an atomic, molecular and mesoscopic level. However, today's experiments, using either wavelength-selected cw beams from steady-state reactor or spallation sources or, on the other hand, comparatively weak pulsed spallation source beams (with the exception of the pulsed IBR-2 reactor in Dubna), suffer from relatively low source strengths, e.g. compared to synchrotron-radiation investigations. Therefore, neutron scattering methods can greatly benefit from next generation pulsed spallation neutron sources with 1-10 MW average proton beam power, which will allow analyzing wavelengths by time-of-flight (TOF) and thus utilizing in an experiment simultaneously a large fraction of the full wavelength band. However, the improved instantaneous flux will pose great challenges on the detection systems, since for instance for ESS, the strongest of the projected sources, the peak thermal neutron flux will be higher by nearly two orders of magnitude than at the presently strongest sources. Owing to current improvements in neutron optics and spectrometer design, the fluxes impinging on the samples will be further enhanced by another factor 5-10; however, this will be compensated for by the tendency to investigate smaller samples becoming accessible due to smaller foci and higher beam fluxes. Hence, thermal neutron detectors with up to two orders of magnitude higher peak count rate capacity in conjunction with microsecond TOF and for some applications sub-millimeter position resolutions are required, in addition to other characteristics like e.g. high long-term stability and low sensitivity to photon background. In this review article an overview will be given on the current state-of-the-art and on currently investigated novel solutions for thermal neutron detectors for very high rate and resolution time-resolved experiments, comprising silicon

  13. Target Operational Experience at the Spallation Neutron Source

    SciTech Connect

    Riemer, Bernie; Janney, Jim G; Kaminskas, Saulius; McClintock, David A; Rosenblad, Peter M

    2013-01-01

    The Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL) has operated at unprecedented power levels for a short-pulse spallation source. Target operations have been successful but not without difficulties. Three targets out of the eight used to date have ended life unexpectedly causing interruptions to the neutron science users. The first of a kind mercury target design experiences beam-pulse induced cavitation damage that is suspected in one of the target leaks. The two other targets suffered early failures due to defective welds. Diagnosing the causes of target leaks and understanding of the progression of cavitation erosion and radiation damage effects has made use of post-irradiation examination (PIE) capabilities. As a result of PIE, review of quality assurance practices and related investigations, design changes are being implemented and manufacturing oversight improved. This paper describes SNS target operating experience, including the more important observations and lessons learned.

  14. SPALLATION NEUTRON SOURCE OPERATIONAL EXPERIENCE AT 1 MW

    SciTech Connect

    Galambos, John D

    2011-01-01

    The Spallation Neutron Source (SNS) has been operating at the MW level for about one year. Experience in beam loss control and machine activation at this power level is presented. Also experience with machine protection systems is reviewed, which is critical at this power level. One of the most challenging operational aspects of high power operation has been attaining high availability, which is also discussed

  15. Spallation neutron source and other high intensity froton sources

    SciTech Connect

    Weiren Chou

    2003-02-06

    This lecture is an introduction to the design of a spallation neutron source and other high intensity proton sources. It discusses two different approaches: linac-based and synchrotron-based. The requirements and design concepts of each approach are presented. The advantages and disadvantages are compared. A brief review of existing machines and those under construction and proposed is also given. An R&D program is included in an appendix.

  16. Fission of 232Th in a spallation neutron field

    NASA Astrophysics Data System (ADS)

    Yurevich, V. I.; Nikolaev, V. A.; Yakovlev, R. M.

    2016-03-01

    The spatial distributions of thorium fission reaction rate in a spallation neutron field of thick lead target bombarded by protons or deuterons with energy between 1.0 and 3.7 GeV were measured. Approximately a linear dependence of the thorium fission rate on the beam energy is observed. The mean fission cross section of 232Th <σ f > ≈ 123 mb and it does not depend on energy and type of the beam particles.

  17. Core Vessel Insert Handling Robot for the Spallation Neutron Source

    SciTech Connect

    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, 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.

  18. A Drabkin energy filter for experiments at a spallation neutron source.

    SciTech Connect

    Parizzi, A. A.; Felcher, G. P.; Klose, F.

    2000-11-21

    We present a new approach for dynamic monochromatization of neutrons suitable for time-of-flight experiments at spallation neutron sources. The method requires polarized neutrons and is based on the Drabkin energy filter. In its initial application, this magnetic resonator device, consisting of a polarizer/analyzer system and a wavelength-dependent spin flipper, was proposed for extracting a narrow bandwidth from a broad bandwidth polarized neutron beam. At a spallation neutron source, wavelength is determined by time-of-flight (TOF) from the source to the detector. However, at each instant a spread of wavelengths is recorded due to the non-zero emission time of the source/moderator system. Particularly, high-intensity moderators for cold neutrons produce long ''tails'' in the intensity/time distribution for all wavelengths, degrading the resolution of the experiments. The Drabkin energy filter can be used to cut the neutron tails for all wavelengths, by drifting the resonance condition in synchronization with the TOF. Calculations show that the method is viable, and that substantial resolution gains are obtained by application to a TOF neutron reflectometer.

  19. The Spallation Neutron Source Beam Commissioning and Initial Operations

    SciTech Connect

    Henderson, Stuart; Aleksandrov, Alexander V.; Allen, Christopher K.; Assadi, Saeed; Bartoski, Dirk; Blokland, Willem; Casagrande, F.; Campisi, I.; Chu, C.; Cousineau, Sarah M.; Crofford, Mark T.; Danilov, Viatcheslav; Deibele, Craig E.; Dodson, George W.; Feshenko, A.; Galambos, John D.; Han, Baoxi; Hardek, T.; Holmes, Jeffrey A.; Holtkamp, N.; Howell, Matthew P.; Jeon, D.; Kang, Yoon W.; Kasemir, Kay; Kim, Sang-Ho; Kravchuk, L.; Long, Cary D.; McManamy, T.; Pelaia, II, Tom; Piller, Chip; Plum, Michael A.; Pogge, James R.; Purcell, John David; Shea, T.; Shishlo, Andrei P; Sibley, C.; Stockli, Martin P.; Stout, D.; Tanke, E.; Welton, Robert F; Zhang, Y.; Zhukov, Alexander P

    2015-09-01

    The Spallation Neutron Source (SNS) accelerator delivers a one mega-Watt beam to a mercury target to produce neutrons used for neutron scattering materials research. It delivers ~ 1 GeV protons in short (< 1 us) pulses at 60 Hz. At an average power of ~ one mega-Watt, it is the highest-powered pulsed proton accelerator. The accelerator includes the first use of superconducting RF acceleration for a pulsed protons at this energy. The storage ring used to create the short time structure has record peak particle per pulse intensity. Beam commissioning took place in a staged manner during the construction phase of SNS. After the construction, neutron production operations began within a few months, and one mega-Watt operation was achieved within three years. The methods used to commission the beam and the experiences during initial operation are discussed.

  20. Target station shielding issues at the spallation neutron source.

    PubMed

    Ferguson, P D; Gallmeier, F X; Iverson, E B; Popova, I I

    2005-01-01

    Recent spallation neutron source shielding activities in support of the neutron beam shutters and the hot cell walls are presented. Existing neutron beam shutters can be replaced with concrete at low power or with concrete and steel at approximately 500 kW of beam power. Potential voids in the hot cell walls are analysed to determine the impact on dose rates as a function of void size. A change in the type of shielding work is noted as the project moved from the early design stages as a 'green field' site to the current stage as a construction project nearing completion, where issues to be addressed are approaching retrofit-type analyses. PMID:16381707

  1. The Spallation Neutron Source: A powerful tool for materials research

    SciTech Connect

    Mason, Thom; Anderson, Ian S; Ankner, John Francis; Egami, Takeshi; Ekkebus, Allen E; Herwig, Kenneth W; Hodges, Jason P; Horak, Charlie M; Horton, Linda L; Klose, Frank Richard; Mesecar, Andrew D.; Myles, Dean A A; Ohl, M.; Zhao, Jinkui

    2006-01-01

    When completed in 2006, the Spallation Neutron Source (SNS) will use an accelerator to produce the most intense beams of pulsed neutrons in the world. This unique facility is being built by a collaboration of six US Department of Energy laboratories and will serve a diverse community of users drawn from academia, industry, and government labs. The project continues on schedule and within budget, with commissioning and installation of all systems going well. Installation of 14 state-of-the-art instruments is under way, and design work is being completed for several others. These new instruments will enable inelastic and elastic-scattering measurements across a broad range of science such as condensed-matter physics, chemistry, engineering materials, biology, and beyond. Neutron Science at SNS will be complemented by research opportunities at several other facilities under way at Oak Ridge National Laboratory.

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

    SciTech Connect

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

    1996-06-01

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

  3. POWER SUPPLY CONTROL FOR THE SPALLATION NEUTRON SOURCE.

    SciTech Connect

    LAMBIASE, R.F.; OERTER, B.; SMITH, J.

    2000-06-30

    Brookhaven National Laboratory is currently constructing an accumulator ring as part of a six laboratory collaboration to build the Spallation Neutron Source (SNS) that will be located in Oak Ridge, Tennessee. Control of the power supplies will be implemented using a simple integrated system that provides all functions (setpoint, readback, control and status) with a single board at the power converter. Communication between the power supply interface and the VME control card is through a pair of fibers that also provides electrical isolation. This paper describes the power supply control system and it's impact on the SNS.

  4. Beginnings of remote handling at the RAL Spallation Neutron Source

    SciTech Connect

    Liska, D.J.; Hirst, J.

    1985-01-01

    Expenditure of funds and resources for remote maintenance systems traditionally are delayed until late in an accelerator's development. However, simple remote-surveillance equipment can be included early in facility planning to set the stage for future remote-handling needs and to identify appropriate personnel. Some basic equipment developed in the UK at the Spallation Neutron Source (SNS) that serves this function and that has been used to monitor beam loss during commissioning is described. A photograph of this equipment, positioned over the extractor septum magnet, is shown. This method can serve as a pattern approach to the problem of initiating remote-handling activities in other facilities.

  5. SPALLATION NEUTRON SOURCE RING-DESIGN AND CONSTRUCTION SUMMARY.

    SciTech Connect

    WEI,J.

    2005-05-16

    After six years, the delivery of components for the Spallation Neutron Source (SNS) accumulator ring (AR) and the transport lines was completed in Spring 2005. Designed to deliver 1.5 MW beam power (1.5 x 10{sup 14} protons of 1 GeV kinetic energy at a repetition rate of 60 Hz), stringent measures were implemented in the fabrication, test, and assembly to ensure the quality of the accelerator systems. This paper summarizes the design, R&D, and construction of the ring and transport systems.

  6. Emittance characterization of the spallation neutron source H- injector

    NASA Astrophysics Data System (ADS)

    Han, B. X.; Stockli, M. P.; Welton, R. F.; Murray, S. N., Jr.; Pennisi, T. R.; Santana, M.

    2013-02-01

    The H- injector for the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory consists of a RF H- ion source and a compact electrostatic low-energy beam transport (LEBT) section. Up to 5 ion sources and up to 4 LEBT assemblies are alternated for the SNS beam operations. The beam current and emittance of the H- beam exiting the LEBT were characterized on the test-stand for different sources and LEBT assemblies in order to understand and minimize their performance variations.

  7. AN ALTERNATIVE LATTICE FOR THE SPALLATION NEUTRON SOURCE ACCUMULATOR RING.

    SciTech Connect

    GARDNER,C.J.; LEE,Y.Y.; TSOUPAS,N.; WEI,J.

    1999-03-29

    As a key component of the Spallation Neutron Source (SNS) Project, the Accumulator Ring will collect the proton beam from the SNS LINAC at an intensity of 2 x 10{sup 14} per pulse at 60 Hz for a total power of 2 MW, exceeding present performance value of existing facilities. Requirements of minimum beam loss for hands-on maintenance and flexibility for future upgrade are essential for the lattice design. In this paper, we study an alternative lattice emphasizing various injection schemes and flexibility for future upgrade. Working points, sextupole families for chromaticity control, and alternate extraction schemes are also considered.

  8. Workshop: Research and development plans for high power spallation neutron testing at BNL

    SciTech Connect

    1996-08-05

    This report consists of vugraphs from presentations at the meeting. The papers covered the following topics: (1) APS as a proton source; (2) target status for NSNS (National Spallation Neutron Source); (3) spallation neutron source in Japan; (4) liquid LiBi flow loop; and (5) research and development plans for high power tests at the AGS.

  9. Fundamental neutron physics beamline at the spallation neutron source at ORNL

    DOE PAGESBeta

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

    2014-11-04

    In this paper, we describe the Fundamental Neutron Physics Beamline (FnPB) facility located at the Spallation Neutron Source at Oak Ridge National Laboratory. The FnPB was designed for the conduct of experiments that investigate scientific issues in nuclear physics, particle physics, astrophysics and cosmology using a pulsed slow neutron beam. Finally, we present a detailed description of the design philosophy, beamline components, and measured fluxes of the polychromatic and monochromatic beams.

  10. The Macromolecular Neutron Diffractometer MaNDi at the Spallation Neutron Source

    DOE PAGESBeta

    Coates, Leighton; Cuneo, Matthew J.; Frost, Matthew J.; He, Junhong; Weiss, Kevin L.; McFeeters, Hana; Tomanicek, Stephen J.; Vandavasi, Venu Gopal; Langan, Paul; Iverson, Erik B.

    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.

  11. The Macromolecular Neutron Diffractometer MaNDi at the Spallation Neutron Source

    SciTech Connect

    Coates, Leighton; Cuneo, Matthew J.; Frost, Matthew J.; He, Junhong; Weiss, Kevin L.; McFeeters, Hana; Tomanicek, Stephen J.; Vandavasi, Venu Gopal; Langan, Paul; Iverson, Erik B.

    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.

  12. Optimizing Moderator Dimensions for Neutron Scattering at the Spallation Neutron Source

    SciTech Connect

    Zhao, Jinkui; Robertson, Lee; Herwig, Kenneth W; Gallmeier, Franz X; Riemer, Bernie

    2013-01-01

    In this work, we investigate the effect of neutron moderator dimensions on the performance of neutron scattering instruments at the Spallation Neutron Source. In a recent study of the planned second target station at the Spallation Neutron Source (SNS) facility [1,2], we have found that the dimensions of a moderator play a significant role in determining its surface brightness. A smaller moderator may be significantly brighter for a smaller viewing area [4]. One of the immediate implications of this finding is that for modern neutron scattering instrument designs, moderator dimensions and brightness have to be incorporated as an integrated optimization parameter. Here, we establish a strategy of matching neutron scattering instruments with moderators using analytical and Monte Carlo techniques. In order to simplify our treatment, we group the instruments into two broad categories, those with natural collimation and those that use neutron guide systems. We found that the cross-sections of the sample and the neutron guide, respectively, are the deciding factors for choosing the moderator. Beam divergence plays no role as long as it is within the reach of practical constraints. Namely, the required divergence is not too large for the guide or sample to be located close enough to the moderator on an actual spallation source.

  13. Facility for fast neutron irradiation tests of electronics at the ISIS spallation neutron source

    SciTech Connect

    Andreani, C.; Pietropaolo, A.; Salsano, A.; Gorini, G.; Tardocchi, M.; Paccagnella, A.; Gerardin, S.; Frost, C. D.; Ansell, S.; Platt, S. P.

    2008-03-17

    The VESUVIO beam line at the ISIS spallation neutron source was set up for neutron irradiation tests in the neutron energy range above 10 MeV. The neutron flux and energy spectrum were shown, in benchmark activation measurements, to provide a neutron spectrum similar to the ambient one at sea level, but with an enhancement in intensity of a factor of 10{sup 7}. Such conditions are suitable for accelerated testing of electronic components, as was demonstrated here by measurements of soft error rates in recent technology field programable gate arrays.

  14. Electron cloud development in the Proton Storage Ring and in theSpallation Neutron Source

    SciTech Connect

    Pivi, M.T.F.; Furman, M.A.

    2002-10-08

    We have applied our simulation code "POSINST" to evaluatethe contribution to the growth rate of the electron-cloud instability inproton storage rings. Recent simulation results for the main features ofthe 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 key ingredient in our modelis a detailed description of the secondary emitted-electron energyspectrum. A refined model for the secondary emission process includingthe so-called true secondary, rediffused and backscattered electrons hasrecently been included in the electron-cloud code.

  15. Systematic neutron guide misalignment for an accelerator-driven spallation neutron source

    NASA Astrophysics Data System (ADS)

    Zendler, C.; Bentley, P. M.

    2016-08-01

    The European Spallation Source (ESS) is a long pulse spallation neutron source that is currently under construction in Lund, Sweden. A considerable fraction of the 22 planned instruments extend as far as 75-150 m from the source. In such long beam lines, misalignment between neutron guide segments can decrease the neutron transmission significantly. In addition to a random misalignment from installation tolerances, the ground on which ESS is built can be expected to sink with time, and thus shift the neutron guide segments further away from the ideal alignment axis in a systematic way. These systematic errors are correlated to the ground structure, position of buildings and shielding installation. Since the largest deformation is expected close to the target, even short instruments might be noticeably affected. In this study, the effect of this systematic misalignment on short and long ESS beam lines is analyzed, and a possible mitigation by overillumination of subsequent guide sections investigated.

  16. Mercury Cavitation Phenomenon in Pulsed Spallation Neutron Sources

    SciTech Connect

    Futakawa, Masatoshi; Naoe, Takashi; Kawai, Masayoshi

    2008-06-24

    Innovative researches will be performed at Materials and Life Science Experimental Facility in J-PARC, in which a mercury target system will be installed as MW-class pulse spallation neutron sources. Proton beams will be injected into mercury target to induce the spallation reaction. At the moment the intense 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. Localized impacts by micro-jets and/or shock waves which are caused by cavitation bubble collapse impose pitting damage on the vessel wall. The pitting damage which degrades the structural integrity of target vessels is a crucial issue for high power mercury targets. Micro-gas-bubbles injection into mercury may be useful to mitigate the pressure wave and the pitting damage. The visualization of cavitation-bubble and gas-bubble collapse behaviors was carried out by using a high-speed video camera. The differences between them are recognized.

  17. BEAM INSTRUMENTATION FOR THE SPALLATION NEUTRON SOURCE RING.

    SciTech Connect

    WITKOVER,R.L.; CAMERON,P.R.; SHEA,T.J.; CONNOLLY,R.C.; KESSELMAN,M.

    1999-03-29

    The Spallation Neutron Source (SNS) will be constructed by a multi-laboratory collaboration with BNL responsible for the transfer lines and ring. [1] The 1 MW beam power necessitates careful monitoring to minimize un-controlled loss. This high beam power will influence the design of the monitors in the high energy beam transport line (HEBT) from linac to ring, in the ring, and in the ring-to-target transfer line (RTBT). The ring instrumentation must cover a 3-decade range of beam intensity during accumulation. Beam loss monitoring will be especially critical since un-controlled beam loss must be kept below 10{sup -4}. A Beam-In-Gap (BIG) monitor is being designed to assure out-of-bucket beam will not be lost in the ring.

  18. SPALLATION NEUTRON SOURCE HIGH-POWER PROTECTION MODULE TEST STAND

    SciTech Connect

    Lee, Sung-Woo; Ball, Jeffrey Allen; Crofford, Mark T; Davidson Jr, Taylor L; Jones, Stacey L; Hardek, Thomas W

    2010-01-01

    The Spallation Neutron Source (SNS) High-Power Protection Module (HPM) provides interlocks and fast shutdown for the radio frequency (RF) system to protect the accelerating structures and high power RF (HPRF) Distribution System. The HPM has required some functional upgrades since the start of beam operations and an upgrade to the HPM test stand was required to support these added features. The HPM test stand currently verifies functionality, RF channel calibration, and measurement of the speed of shutdown to ensure the specifications are met. The upgraded test stand was implemented in a Field Programmable Gate Array (FPGA) to allow for future growth and flexibility. Work is currently progressing on automation of the test stand to better perform the required module calibration schedule.

  19. THE SPALLATION NEUTRON SOURCE CRYOMODULE TEST STAND RF SYSTEM

    SciTech Connect

    Crofford, Mark T; Ball, Jeffrey Allen; Davidson Jr, Taylor L; Hardek, Thomas W; Heidenreich, Dale A; Kasemir, Kay; Kim, Sang-Ho; Kang, Yoon

    2008-01-01

    The Spallation Neutron Source (SNS) has recently commissioned a cryomodule test facility for the repair and testing of the super-conducting radio-frequency (SRF) cavities. This facility utilizes the original 402.5/805 MHz Radio Frequency (RF) Klystron Test Stand as its power source along with dual Low Level RF (LLRF) control systems. One control system is based on the standard SNS Linac LLRF controls with a second system for open-loop only control. The system is designed to allow simultaneous testing of devices in the test cave and other devices which can be tested outside of the enclosure. Initial tests have shown good results; some improvements are yet to be implemented.

  20. STATUS OF THE SPALLATION NEUTRON SOURCE SUPERCONDUCTING RF FACILITIES

    SciTech Connect

    Stout, Daniel S; Assadi, Saeed; Campisi, Isidoro E; Casagrande, Fabio; Crofford, Mark T; DeVan, Bill; Hardek, Thomas W; Henderson, Stuart D; Howell, Matthew P; Kang, Yoon W; Geng, Xiaosong; Stone Jr, William C; Strong, William Herb; Williams, Derrick C; Wright, Paul Alan

    2007-01-01

    The Spallation Neutron Source (SNS) project was completed with only limited superconducting RF (SRF) facilities installed as part of the project. A concerted effort has been initiated to install the infrastructure and equipment necessary to maintain and repair the superconducting Linac, and to support power upgrade research and development (R&D). Installation of a Class10/100/10,000 cleanroom and outfitting of the test cave with RF, vacuum, controls, personnel protection and cryogenics systems is underway. A horizontal cryostat, which can house a helium vessel/cavity and fundamental power coupler for full power, pulsed testing, is being procured. Equipment for cryomodule assembly and disassembly is being procured. This effort, while derived from the experience of the SRF community, will provide a unique high power test capability as well as long term maintenance capabilities. This paper presents the current status and the future plans for the SNS SRF facilities.

  1. CONSTRUCTION STATUS AND ISSUES OF THE SPALLATION NEUTRON SOURCE RING.

    SciTech Connect

    WEI,J.

    2004-07-05

    The Spallation Neutron Source (SNS) ring is designed to accumulate beam pulses of 1.5 x 10{sup 14} protons of 1 GeV kinetic energy at a repetition rate of 60 Hz [1]. At such beam intensity and power, key design challenges include control of beam loss and radio-activation, construction of high-quality large-aperture magnets and power supplies, design of robust injection and extraction systems, minimization of beam-coupling impedances, and mitigation of electron-cloud effects. This paper discusses the status of the ring systems with emphasis on technical challenges and issues, and presents future perspectives towards a next-generation high-intensity facility.

  2. Electron-cloud mitigation in the spallation neutron source ring

    SciTech Connect

    Wei, J.; Blaskiewicz, M.; Brodowski, J.; Cameron, P.; Davino, D.; Fedotov, A.; He, P.; Hseuh, H.; Lee, Y.Y.; Meng, W.; Raparia, D.; Tuozzolo, J.; Zhang, S.Y.; Danilov, V.; Henderson, S.; Furman, M.; Pivi, M.; Macek, R.

    2003-05-01

    The Spallation Neutron Source (SNS) accumulator ring is designed to accumulate, via H- injection, protons of 2 MW beam power at 1 GeV kinetic energy at a repetition rate of 60 Hz [1]. At such beam intensity, electron cloud is expected to be one of the intensity-limiting mechanisms that complicate ring operations. This paper summarizes mitigation strategy adopted in the design, both in suppressing electron-cloud formation and in enhancing Landau damping, including tapered magnetic field and monitoring system for the collection of stripped electrons at injection, TiN coated beam chamber for suppression of the secondary yield, clearing electrodes dedicated for the injection region and parasitic on BPMs around the ring, solenoid windings in the collimation region, and planning of vacuum systems for beam scrubbing upon operation.

  3. Impedance measurements of the Spallation Neutron Source extraction kicker system

    NASA Astrophysics Data System (ADS)

    Hahn, H.

    2004-10-01

    Transverse coupling impedance measurements of the Spallation Neutron Source (SNS) beam extraction system were performed and the results are here reported. The SNS beam extraction system is composed from 14 subsystems, each of which consists of a vertical kicker magnet plus a pulse forming network (PFN). Impedance bench measurements were performed on one large and one small aperture magnet, stand-alone as well as assembled with the first-article production PFN. The impedance measuring methods to cover the interesting frequency range from below 1 to 100MHz are described in considerable detail. The upper frequency range is properly covered by the conventional twin-wire method but it had to be supplemented at the low-frequency end by a direct input impedance measurement at the magnet busbar. Required modifications of the PFN to maintain the impedance budget are discussed. The total impedance estimate was finally obtained by quadratic scaling with vertical aperture from the two tested kicker subsystems.

  4. COMMISSIONING OF THE SPALLATION NEUTRON SOURCE ACCELERATOR SYSTEMS

    SciTech Connect

    Plum, Michael A

    2007-01-01

    The Spallation Neutron Source accelerator complex consists of a 2.5 MeV H- front-end injector system, a 186 MeV normal-conducting linear accelerator, a 1 GeV superconducting linear accelerator, an accumulator ring, and associated beam transport lines. The linac was commissioned in five discrete runs, starting in 2002 and completed in 2005. The accumulator ring and associated beam transport lines were commissioned in two runs from January to April 2006. With the completed commissioning of the SNS accelerator, the facility has begun initial low-power operations. In the course of beam commissioning, most beam performance parameters and beam intensity goals have been achieved at low duty factor. A number of beam dynamics measurements have been performed, including emittance evolution, transverse coupling in the ring, beam instability thresholds, and beam distributions on the target. The commissioning results, achieved beam performance and initial operating experience of the SNS will be discussed

  5. Electron Cloud Mitigation in the Spallation Neutron Source Ring

    SciTech Connect

    Wei, J.; Blaskiewicz, Michael; Brodowski, J.; Cameron, P.; Davino, Daniele; Fedotov, A.; He, P.; Hseuh, H.; Lee, Y.Y.; Ludewig, H.; Meng, W.; Raparia, D.; Tuozzolo, J.; Zhang, S.Y.; Catalan-Lasheras, N.; Macek, R.J.; Furman, Miguel A.; Aleksandrov, A.; Cousineau, S.; Danilov, V.; Henderson, S.; /Brookhaven /CERN /LANL, Ctr. for Nonlinear Studies /LBL, Berkeley /Oak Ridge /SLAC

    2008-03-17

    The Spallation Neutron Source (SNS) accumulator ring is designed to accumulate, via H{sup -} injection, protons of 2 MW beam power at 1 GeV kinetic energy at a repetition rate of 60 Hz [1]. At such beam intensity, electron-cloud is expected to be one of the intensity-limiting mechanisms that complicate ring operations. This paper summarizes mitigation strategy adopted in the design, both in suppressing electron-cloud formation and in enhancing Landau damping, including tapered magnetic field and monitoring system for the collection of stripped electrons at injection, TiN coated beam chamber for suppression of the secondary yield, clearing electrodes dedicated for the injection region and parasitic on BPMs around the ring, solenoid windings in the collimation region, and planning of vacuum systems for beam scrubbing upon operation.

  6. Spallation neutron source cryomodule heat loads and thermal design

    SciTech Connect

    E. F. Daly; V. Ganni; C. H. Rode; W. J. Schneider; K. M. Wilson; M. A. Wiseman

    2002-05-10

    When complete, the Spallation Neutron Source (SNS) will provide a 1 GeV, 2 MW beam for experiments. One portion of the machine's linac consists of over 80 Superconducting Radio Frequency (SRF) 805 MHz cavities housed in a minimum of 23 cryomodules operating at a saturation temperature of 2.1 K. Minimization of the total heat load is critical to machine performance and for efficient operation of the system. The total heat load of the cryomodules consists of the fixed static load and the dynamic load, which is proportional to the cavity performance. The helium refrigerator supports mainly the cryomodule loads and to a lesser extent the distribution system loads. The estimated heat loads and calculated thermal performance are discussed along with two unique features of this design: the helium heat exchanger housed in the cryomodule return end can and the helium gas cooled fundamental power coupler.

  7. Rationale for a spallation neutron source target system test facility at the 1-MW Long-Pulse Spallation Source

    SciTech Connect

    Sommer, W.F.

    1995-12-01

    The conceptual design study for a 1-MW Long-Pulse Spallation Source at the Los Alamos Neutron Science Center has shown the feasibility of including a spallation neutron test facility at a relatively low cost. This document presents a rationale for developing such a test bed. Currently, neutron scattering facilities operate at a maximum power of 0.2 MW. Proposed new designs call for power levels as high as 10 MW, and future transmutation activities may require as much as 200 MW. A test bed will allow assessment of target neutronics; thermal hydraulics; remote handling; mechanical structure; corrosion in aqueous, non-aqueous, liquid metal, and molten salt systems; thermal shock on systems and system components; and materials for target systems. Reliable data in these areas are crucial to the safe and reliable operation of new high-power facilities. These tests will provide data useful not only to spallation neutron sources proposed or under development, but also to other projects in accelerator-driven transmutation technologies such as the production of tritium.

  8. Spallation Neutron Source Operating Experience and Outlook for Upgrades

    NASA Astrophysics Data System (ADS)

    Henderson, Stuart

    2010-03-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is a MW-class accelerator-driven pulsed neutron source. The SNS began formal operations in October 2006. Since then, the beam power has been increased to 1 MW, the number of operating hours per year has increased to nearly 5000, the availability has increased to 85%, and the number of operating neutron scattering instruments has increased to 13. Plans are in place to increase the beam power and availability to their design values of 1.4 MW and 90% over the next two years, and to continue the build-out of instruments to 16 by 2012. Two upgrade projects are in the planning stages. In the first, the beam power of the SNS is increased to at least 2 MW by raising the beam energy from 1.0 to 1.3 GeV and the beam current by 60%. In the second, a Second Target Station is constructed, and is powered by sharing beam pulses with the first target station. The operating experience will be described, as will the challenges that have been met along the path toward 1 MW beam power. The strategy for upgrades will also be presented.

  9. Materials Compatibility Studies for the Spallation Neutron Source

    SciTech Connect

    DiStefano, J.R.; Manneschmidt, E.T.; Pawel, S.J.

    1998-09-01

    The Spallation Neutron Source (SNS) is a high power facility for producing neutrons that utilizes flowing liquid mercury inside an austenitic stainless steel container as the target for a 1.0 GeV proton beam. The energy deposited in the target is transported by two separate mercury flow streams: one to transport heat in the interior target region and one to cool the stainless steel container. Three-dimensional computational fluid dynamics simulations have been performed to predict temperature, velocity, and pressure distributions in the target. Results have generally shown that the power deposited in the bulk mercury can be effectively transported with reasonable flow rates and the bulk mercury temperature should not exceed 160{deg}C. Assuming good thermal contact, the maximum stainless steel wall temperature should be 130 {deg}C. Type 316 SS has been selected as the container material for the mercury and consequences of exposure of 316 SS to radiation, thermal shock, thermal stress, cavitation and hot, flowing mercury are all being addressed by R&D programs. In addition, corrosion studies include evaluation of Inconel 718 because it has been successfully used in previous water cooled spallation neutron systems as a window material. With type 316 SS selected to contain the mercury target of the SNS, two types of compatibility issues have been examined: LME and temperature gradient mass transfer. Studies have shown that mercury does not easily wet type 316 SS below 275{deg}C. In the LME experiments, attempts were made to promote wetting of the steel by mercury either by adding gallium to the mercury or coating the specimen with a tin-silver solder that the mercury easily wets. The latter proved more reliable in establishing wetting, but there was no evidence of LME in any of the constant extension rate tensile tests either at 23 or 100 {deg}C. Inconel 718 also showed no change in room temperature properties when tested in mercwy or mercury-gallium. However, there

  10. 5 MW pulsed spallation neutron source, Preconceptual design study

    SciTech Connect

    Not Available

    1994-06-01

    This report describes a self-consistent base line design for a 5 MW Pulsed Spallation Neutron Source (PSNS). It is intended to establish feasibility of design and as a basis for further expanded and detailed studies. It may also serve as a basis for establishing project cost (30% accuracy) in order to intercompare competing designs for a PSNS not only on the basis of technical feasibility and technical merit but also on the basis of projected total cost. The accelerator design considered here is based on the objective of a pulsed neutron source obtained by means of a pulsed proton beam with average beam power of 5 MW, in {approx} 1 {mu}sec pulses, operating at a repetition rate of 60 Hz. Two target stations are incorporated in the basic facility: one for operation at 10 Hz for long-wavelength instruments, and one operating at 50 Hz for instruments utilizing thermal neutrons. The design approach for the proton accelerator is to use a low energy linear accelerator (at 0.6 GeV), operating at 60 Hz, in tandem with two fast cycling booster synchrotrons (at 3.6 GeV), operating at 30 Hz. It is assumed here that considerations of cost and overall system reliability may favor the present design approach over the alternative approach pursued elsewhere, whereby use is made of a high energy linear accelerator in conjunction with a dc accumulation ring. With the knowledge that this alternative design is under active development, it was deliberately decided to favor here the low energy linac-fast cycling booster approach. Clearly, the present design, as developed here, must be carried to the full conceptual design stage in order to facilitate a meaningful technology and cost comparison with alternative designs.

  11. The new cold neutron chopper spectrometer at the Spallation Neutron Source: design and performance.

    PubMed

    Ehlers, G; Podlesnyak, A A; Niedziela, J L; Iverson, E B; Sokol, P E

    2011-08-01

    The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments. PMID:21895276

  12. The new cold neutron chopper spectrometer at the Spallation Neutron Source: Design and performance

    SciTech Connect

    Ehlers, G.; Podlesnyak, A. A.; Niedziela, J. L.; Iverson, E. B.; Sokol, P. E.

    2011-08-15

    The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

  13. The new Cold Neutron Chopper Spectrometer at the Spallation Neutron Source -- Design and Performance

    SciTech Connect

    Ehlers, Georg; Podlesnyak, Andrey A.; Niedziela, Jennifer L.; Iverson, Erik B.; Sokol, Paul E.

    2011-01-01

    The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

  14. 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.

  15. rf improvements for Spallation Neutron Source H-ion source

    SciTech Connect

    Kang, Yoon W; Fuja, Raymond E; Goulding, Richard Howell; Hardek, Thomas W; Lee, Sung-Woo; McCarthy, Mike; Piller, Chip; Shin, Ki; Stockli, Martin P; Welton, Robert F

    2010-01-01

    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. 2010 American Institute of Physics.

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

    SciTech Connect

    Peter Kneisel; John Brawley; Richard Bundy; Gianluigi Ciovati; Kurt Macha; Danny Machie; John Mammosser; Ron Sundelin; Larry Turlington; Katherine Wilson; J. Sekutowicz; D. Barni; C. Pagani; R. Parodi; P. Pierini; D. Schrage; M. Doleans; S.H. Kim; D. Mangra; P. Ylae-Oijala

    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 a 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.

  17. Spallation Neutron Source Accident Terms for Environmental Impact Statement Input

    SciTech Connect

    Devore, J.R.; Harrington, R.M.

    1998-08-01

    This report is about accidents with the potential to release radioactive materials into the environment surrounding the Spallation Neutron Source (SNS). As shown in Chap. 2, the inventories of radioactivity at the SNS are dominated by the target facility. Source terms for a wide range of target facility accidents, from anticipated events to worst-case beyond-design-basis events, are provided in Chaps. 3 and 4. The most important criterion applied to these accident source terms is that they should not underestimate potential release. Therefore, conservative methodology was employed for the release estimates. Although the source terms are very conservative, excessive conservatism has been avoided by basing the releases on physical principles. Since it is envisioned that the SNS facility may eventually (after about 10 years) be expanded and modified to support a 4-MW proton beam operational capability, the source terms estimated in this report are applicable to a 4-MW operating proton beam power unless otherwise specified. This is bounding with regard to the 1-MW facility that will be built and operated initially. See further discussion below in Sect. 1.2.

  18. Mechanical Engineering of the Linac for the Spallation Neutron Source

    SciTech Connect

    Bultman, N.K.; Chen, Z.; Collier, M.; Erickson, J.L.; Guthrie, A.; Hunter, W.T.; Ilg, T.; Meyer, R.K.; Snodgrass, N.L.

    1999-03-29

    The linac for the Spallation Neutron Source (SNS) Project will accelerate an average current of 1 mA of H{sup {minus}} ions from 20 MeV to 1GeV for injection into an accumulator ring. The linac will be an intense source of H{sup {minus}} ions and as such requires advanced design techniques to meet project technical goals as well as to minimize costs. The DTL, CCDTL and CCL are 466m long and operate at 805 MHz with a maximum H{sup {minus}} input current of 28 mA and 7% rf duty factor. The Drift Tube Linac is a copper-plated steel structure using permanent magnetic quadrupoles. The Coupled-Cavity portions are brazed copper structures and use electromagnetic quads. RF losses in the copper are 80 MW, with total rf power supplied by 52 klystrons. Additionally, the linac is to be upgraded to the 2- and 4-MW beam power levels with no increase in duty factor. The authors give an overview of the linac mechanical engineering effort and discuss the special challenges and status of the effort.

  19. 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. PMID:20192394

  20. 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.

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

    PubMed

    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 mm(2) to 20 × 20 mm(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. PMID:27370444

  2. The COHERENT Experiment at the Spallation Neutron Source

    SciTech Connect

    Elliott, Steven Ray

    2015-09-30

    The COHERENT collaboration's primary objective is to measure coherent elastic neutrino- nucleus scattering (CEvNS) using the unique, high-quality source of tens-of-MeV neutrinos provided by the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). In spite of its large cross section, the CEvNS process has never been observed, due to tiny energies of the resulting nuclear recoils which are out of reach for standard neutrino detectors. The measurement of CEvNS has now become feasible, thanks to the development of ultra-sensitive technology for rare decay and weakly-interacting massive particle (dark matter) searches. The CEvNS cross section is cleanly predicted in the standard model; hence its measurement provides a standard model test. It is relevant for supernova physics and supernova-neutrino detection, and enables validation of dark-matter detector background and detector-response models. In the long term, precision measurement of CEvNS will address questions of nuclear structure. COHERENT will deploy multiple detector technologies in a phased approach: a 14-kg CsI[Na] scintillating crystal, 15 kg of p-type point-contact germanium detectors, and 100 kg of liquid xenon in a two-phase time projection chamber. Following an extensive background measurement campaign, a location in the SNS basement has proven to be neutron-quiet and suitable for deployment of the COHERENT detector suite. The simultaneous deployment of the three COHERENT detector subsystems will test the N=2 dependence of the cross section and ensure an unambiguous discovery of CEvNS. This document describes concisely the COHERENT physics motivations, sensitivity and plans for measurements at the SNS to be accomplished on a four-year timescale.

  3. Beamline Performance Simulations for the Fundamental Neutron Physics Beamline at the Spallation Neutron Source

    PubMed Central

    Huffman, P. R.; Greene, G. L.; Allen, R. R.; Cianciolo, V.; Huerto, R. R.; Koehler, P.; Desai, D.; Mahurin, R.; Yue, A.; Palmquist, G. R.; Snow, W. M.

    2005-01-01

    Monte Carlo simulations are being performed to design and characterize the neutron optics components for the two fundamental neutron physics beamlines at the Spallation Neutron Source. Optimization of the cold beamline includes characterization of the guides and benders, the neutron transmission through the 0.89 nm monochromator, and the expected performance of the four time-of-flight choppers. The locations and opening angles of the choppers have been studied using a simple spreadsheet-based analysis that was developed for other SNS chopper instruments. The spreadsheet parameters are then optimized using Monte Carlo techniques to obtain the results presented in this paper. Optimization of the 0.89 nm beamline includes characterizing the double crystal monochromator and the downstream guides. The simulations continue to be refined as components are ordered and their exact size and performance specifications are determined.

  4. Neutronics performance and decay heat calculation of a solid target for a spallation neutron source

    NASA Astrophysics Data System (ADS)

    Nio, D.; Ooi, M.; Takenaka, N.; Furusaka, M.; Kawai, M.; Mishima, K.; Kiyanagi, Y.

    2005-08-01

    A solid target is expected to give higher neutron intensity than a liquid target of mercury at a spallation neutron source with a power of around 1 MW. We have studied the neutronic performance of a target-moderator-reflector assembly with a tungsten solid target. It is found that the neutron intensities from moderators were higher in the solid target system than in the mercury liquid target. However, the tungsten target required cladding to prevent tungsten from the corrosion of cooling water. A tungsten target with tantalum cladding has been already developed although tantalum has high decay heat. Therefore, we estimated the decay heat of the target and found that the decay heat of 0.5 mm thick tantalum was still high. We need a thinner tantalum or new cladding materials. It was revealed that adoption of a thinner tantalum or new cladding material such as chrome nitride reduced the decay heat effectively.

  5. 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.

  6. Fundamental neutron physics at a 1 MW long pulse spallation neutron source

    SciTech Connect

    Greene, G.L.

    1995-12-31

    Modern neutron sources and modern neutron science share a common origin in mid twentieth century scientific investigations concerned with the study of the fundamental interactions between elementary particles. Since the time of that common origin, neutron science and the study of elementary particles have evolved into quite disparate disciplines. The neutron became recognized as a powerful tool for the study of condensed matter with modern neutron sources being primarily used (and primarily justified) as tools for condensed matter research. The study of elementary particles has, of course, led to the development of rather different tools and is now dominated by activities carried out at extremely high energies. Notwithstanding this trend, the study of fundamental interactions using neutrons has continued and remains a vigorous activity at many contemporary neutron sources. This research, like neutron scattering research, has benefited enormously by the development of modern high flux neutron facilities. Future sources, particularly high power spallation sources, offer exciting possibilities for the continuation of this program of research.

  7. Computational Benchmark Calculations Relevant to the Neutronic Design of the Spallation Neutron Source (SNS)

    SciTech Connect

    Gallmeier, F.X.; Glasgow, D.C.; Jerde, E.A.; Johnson, J.O.; Yugo, J.J.

    1999-11-14

    The Spallation Neutron Source (SNS) will provide an intense source of low-energy neutrons for experimental use. The low-energy neutrons are produced by the interaction of a high-energy (1.0 GeV) proton beam on a mercury (Hg) target and slowed down in liquid hydrogen or light water moderators. Computer codes and computational techniques are being benchmarked against relevant experimental data to validate and verify the tools being used to predict the performance of the SNS. The LAHET Code System (LCS), which includes LAHET, HTAPE ad HMCNP (a modified version of MCNP version 3b), have been applied to the analysis of experiments that were conducted in the Alternating Gradient Synchrotron (AGS) facility at Brookhaven National Laboratory (BNL). In the AGS experiments, foils of various materials were placed around a mercury-filled stainless steel cylinder, which was bombarded with protons at 1.6 GeV. Neutrons created in the mercury target, activated the foils. Activities of the relevant isotopes were accurately measured and compared with calculated predictions. Measurements at BNL were provided in part by collaborating scientists from JAERI as part of the AGS Spallation Target Experiment (ASTE) collaboration. To date, calculations have shown good agreement with measurements.

  8. High-Power Linac for the Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Rej, D. J.

    2002-04-01

    The Spallation Neutron Source (SNS) will be the world’s most intense source of neutrons for fundamental science and industrial applications. Design and construction of this facility, located at Oak Ridge, is a joint venture between six DOE laboratories. Construction began in 1999 and is currently ahead of the scheduled 2006 completion date. Injecting a high-power, pulsed proton beam into a mercury target produces neutrons. In this talk, we review the physics requirements, design, and status of the construction of the 1-GeV, 1.4-MW average power RF linac for SNS. The accelerator consists of a drift tube linac (DTL), a coupled-cavity linac (CCL), and a superconducting rf (SRF) linac. The phase and quadrupole settings are set to avoid structure and parametric resonances, with coherent resonances posing minimal risk for emittance growth. The DTL is 37 m long and accelerates the ions to 87 MeV. The CCL is 55 m long and accelerates the ions to 186 MeV. The rf structure design and stability for both the DTL and CCL have been validated with scale models. The SRF linac has a modular design to accelerate ions to 1000 MeV, with a straightforward upgrade to 1.3 GeV at a later date. 3D particle-in-cell simulations of beam dynamics are performed to validate performance. The accelerator utilizes 93 MW of pulsed power operating continuously at 60-Hz with an 8factor. Approximately one hundred 402.5 or 805-MHz klystrons, with outputs between 0.55 and 5 MW, are used. The klystrons are powered by a novel converter-modulator that takes advantage of recent advances in IGBT switch plate assemblies and low-loss material cores for boost transformer. Beam diagnostics include position, phase, profile, and current monitors. They are designed to enable accurate beam steering and matching, and to minimize beam loss that would lead to activation and prevent hands-on maintenance.

  9. A calorimetric measurement of the heat deposition in the vicinity of a spallation neutron target

    SciTech Connect

    Fischer, W.E.; Moritz, L.; Spitzer, H.; Thorson, I.M.

    1986-07-01

    An experiment to measure the heat deposition in various materials in the vicinity of a spallation neuron target is described. This experiment has been performed at the Thermal Neutron Facility, TRIUMF. In the analysis of the data, the contributions to the heat deposition from (n,..gamma..) capture processes, fast neutron, and prompt gamma-ray scattering are separated.

  10. Tensile property changes of metals irradiated to low doses with fission, fusion and spallation neutrons

    SciTech Connect

    Heinisch, H.L.; Hamilton, M.L.; Sommer, W.F.; Ferguson, P.D.

    1991-11-01

    Radiation effects due to low doses of spallation neutrons are compared directly to those produced by fission and fusion neutrons. Yield stress changes of pure Cu, alumina-dispersion-strengthened Cu and AISI 316 stainless steel irradiated at 36--55{degrees}C in the Los Alamos Spallation Radiation Effects Facility (LASREF) are compared with earlier results of irradiations at 90{degrees}C using 14 MeV D-T fusion neutrons at the Rotating Target Neutron Source and fission reactor neutrons in the Omega West Reactor. At doses up to 0.04 displacements per atom (dpa), the yield stress changes due to the three quite different neutron spectra correlate well on the basis of dpa in the stainless steel and the Cu alloy. However, in pure Cu, the measured yield stress changes due to spallation neutrons were anomalously small and should be verified by additional irradiations. With the exception of pure Cu, the low dose, low temperature experiments reveal no fundamental differences in radiation hardening by fission, fusion or spallation neutrons when compared on the basis of dpa.

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

    SciTech Connect

    Welton, Robert F; Pennisi, Terry R; Roseberry, Ron T; Stockli, Martin P

    2012-01-01

    The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent {approx}38 mA peak current in the linac and an availability of {approx}90%. H{sup -} beam pulses ({approx}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, {approx}60 kW) of a copper antenna that has been encased with a thickness of {approx}0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of {approx}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 {approx}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 {approx}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.

  12. H- radio frequency source development at the Spallation Neutron Sourcea)

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

    Gianluigi Ciovati

    2001-09-01

    The Spallation Neutron Source project includes a superconducting linac section in the energy range from 186 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 Jefferson Lab, which calls for fabricating and testing 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 on each beam pipe and a port for a high power coaxial input coupler. Three of the four {beta} = 0.61 cavities will be used for a cryomodule test in early 2002. At this time four medium beta cavities and one high beta cavity have been completed at JLab. The first tests on the {beta} = 0.61 and {beta} = 0.81 exceeded the design values for gradient and Q value: E{sub acc} = 10.1 MV/m and Q = 5 x 10{sup 9} at 2.1K for the {beta} = 0.61 and E{sub acc} = 12.3 MV/m and Q = 5 x 10{sup 9} at 2.1 K for the {beta} = 0.81. One of the medium beta cavities has been equipped with an integrated helium vessel and measurements of the static Lorentz force detuning have been done and compared to the ''bare'' cavities. In addition two single cell cavities have been fabricated, equipped with welded-on HOM couplers. They are being used to evaluate the HOM couplers with respect to multipacting, fundamental mode rejection and HOM damping as far as possible in a single cell. This paper describes the cavity design with respect to electromagnetic and mechanical features, the fabrication efforts and the results obtained with the different cavities existing at the time of this workshop.

  14. Optimizing moderator dimensions for neutron scattering at the spallation neutron source

    SciTech Connect

    Zhao, J. K.; Robertson, J. L.; Herwig, Kenneth W.; Gallmeier, Franz X.; Riemer, Bernard W.

    2013-12-15

    In this work, we investigate the effect of neutron moderator dimensions on the performance of neutron scattering instruments at the Spallation Neutron Source (SNS). In a recent study of the planned second target station at the SNS facility, we have found that the dimensions of a moderator play a significant role in determining its surface brightness. A smaller moderator may be significantly brighter over a smaller viewing area. One of the immediate implications of this finding is that for modern neutron scattering instrument designs, moderator dimensions and brightness have to be incorporated as an integrated optimization parameter. Here, we establish a strategy of matching neutron scattering instruments with moderators using analytical and Monte Carlo techniques. In order to simplify our treatment, we group the instruments into two broad categories: those with natural collimation and those that use neutron guide systems. For instruments using natural collimation, the optimal moderator selection depends on the size of the moderator, the sample, and the moderator brightness. The desired beam divergence only plays a role in determining the distance between sample and moderator. For instruments using neutron optical systems, the smallest moderator available that is larger than the entrance dimension of the closest optical element will perform the best (assuming, as is the case here that smaller moderators are brighter)

  15. Optimizing moderator dimensions for neutron scattering at the spallation neutron source.

    PubMed

    Zhao, J K; Robertson, J L; Herwig, Kenneth W; Gallmeier, Franz X; Riemer, Bernard W

    2013-12-01

    In this work, we investigate the effect of neutron moderator dimensions on the performance of neutron scattering instruments at the Spallation Neutron Source (SNS). In a recent study of the planned second target station at the SNS facility, we have found that the dimensions of a moderator play a significant role in determining its surface brightness. A smaller moderator may be significantly brighter over a smaller viewing area. One of the immediate implications of this finding is that for modern neutron scattering instrument designs, moderator dimensions and brightness have to be incorporated as an integrated optimization parameter. Here, we establish a strategy of matching neutron scattering instruments with moderators using analytical and Monte Carlo techniques. In order to simplify our treatment, we group the instruments into two broad categories: those with natural collimation and those that use neutron guide systems. For instruments using natural collimation, the optimal moderator selection depends on the size of the moderator, the sample, and the moderator brightness. The desired beam divergence only plays a role in determining the distance between sample and moderator. For instruments using neutron optical systems, the smallest moderator available that is larger than the entrance dimension of the closest optical element will perform the best (assuming, as is the case here that smaller moderators are brighter). PMID:24387465

  16. A neutron resonance capture analysis experimental station at the ISIS spallation source.

    PubMed

    Pietropaolo, Antonino; Gorini, Giuseppe; Festa, Giulia; Reali, Enzo; Grazzi, Francesco; Schooneveld, Erik M

    2010-09-01

    Neutron resonance capture analysis (NRCA) is a nuclear technique that is used to determine the elemental composition of materials and artifacts (e.g., bronze objects) of archaeological interest. NRCA experiments are mostly performed at the GELINA facility in Belgium, a pulsed neutron source operating with an electron linear accelerator. Very intense fluxes of epithermal neutrons are also provided by spallation neutron sources, such as the ISIS spallation neutron source in the United Kingdom. In the present study, the suitability of the Italian Neutron Experimental Station (INES) beam line for NRCA measurements is assessed using a compact (n, γ) resonance detector made of a Yttrium-Aluminum-Perovskite (YAP) scintillation crystal coupled with a silicon photomultiplier (SiPM) readout. The measurements provided a qualitative recognition of the composition of the standard sample, a lower limit for the sensitivity for NRCA for almost-in-traces elements, and an estimation of the relative isotopic concentration in the sample. PMID:20828445

  17. Behavior of structural and target materials irradiated in spallation neutron environments

    SciTech Connect

    Stubbins, J.F.; Wechsler, M.; Borden, M.; Sommer, W.F.

    1995-05-01

    This paper describes considerations for selection of structural and target materials for accelerator-driven neutron sources. Due to the operating constraints of proposed accelerator-driven neutron sources, the criteria for selection are different than those commonly applied to fission and fusion systems. Established irradiation performance of various alloy systems is taken into account in the selection criteria. Nevertheless, only limited materials performance data are available which specifically related to neutron energy spectra anticipated for spallation sources.

  18. A time-of-flight backscattering spectrometer at the Spallation Neutron Source, BASIS

    SciTech Connect

    Mamontov, E.; Herwig, K. W.

    2011-08-15

    We describe the design and current performance of the backscattering silicon spectrometer (BASIS), a time-of-flight backscattering spectrometer built at the spallation neutron source (SNS) of the Oak Ridge National Laboratory (ORNL). BASIS is the first silicon-based backscattering spectrometer installed at a spallation neutron source. In addition to high intensity, it offers a high-energy resolution of about 3.5 {mu}eV and a large and variable energy transfer range. These ensure an excellent overlap with the dynamic ranges accessible at other inelastic spectrometers at the SNS.

  19. Target station design for a 1 MW pulsed spallation neutron source

    SciTech Connect

    Russell, G.J.; Baker, G.D.; Brewton, R.J.

    1993-12-31

    Target stations are vital components of the 1 MW, next generation spallation neutron source proposed for LANSCE. By and large, target stations design determines the overall performance of the facility. Many traditional concepts will probably have to be rethought, and many new concepts will have to be put forward to meet the 1 MW challenge. This article gives a brief overview of the proposed neutron spallation source from the target station viewpoint, as well as the general philosophy adopted for the design of the LANSCE-II target stations. Some of the saliant concepts and features envisioned for LANSCE-II are briefly described.

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

    SciTech Connect

    G. Ciovati; P. Kneisel; K. Davis; K. Macha; J. Mammosser

    2002-06-01

    The Spallation Neutron Source project includes a superconducting linac section in the energy range from 186 MeV to 1000 MeV operating at a frequency of 805 MHz at 2.1 K. 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 a high power coaxial input coupler. Three of the four Beta=0.61 cavities will be used for a cryomodule test in early 2002. At this time, four medium beta cavities and one high beta cavity have been completed and tested at JLab. In addition, the three medium beta cavities for the prototype cryomodule have been equipped with the integrated Ti-Helium vessel, successfully retested and will be assembled into a cavity string. Results from the cryo-module test should be available by the time of the conference. The tests on the Beta=0.61 cavity and the Beta=0.81 cavity exceeded the design values for gradient and Q - value: E{sub acc} =10.1 MV/m and Q = 5 x 10{sup 9} at 2.1K for Beta=0.61 and E{sub acc} = 12.3 MV/m and Q=5 x 10{sup 9} at 2.1K for Beta = 0.81. The medium beta cavities reached gradients between E{sub acc} = 15 MV/m and 21 MV/m. This paper will describe the test results obtained with the various cavities, some aspects of the HOM damping at cryogenic temperatures, results from microphonics and Lorentz force detuning tests and the cavity string assembly at the time of this workshop.

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

    SciTech Connect

    G. Ciovati, P. Kneisel , J. Brawley, R. Bundy, I. Campisi, K. Davis; K. Macha; D. Machie; J. Mammosser; S. Morgan; R. Sundelin; L. Turlington; K. Wilson; M. Doleans; S.H. Kim; D. Barni; C. Pagani; P. Pierini; K. Matsumoto; R. Mitchell; D. Schrage; R. Parodi; J. Sekutowicz; P. Ylae-Oijala

    2001-09-01

    The Spallation Neutron Source project includes a superconducting linac section in the energy range from 192 MeV to 1000 MeV, operating at a frequency of 805 MHz at 2.1 K. 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 on each beam pipe and a port for a high power coaxial input coupler. Three of the four beta= 0.61 cavities will be used for a cryomodule test in early 2002. At this time four medium beta cavities and one high beta cavity have been completed at JLab. The first tests on the beta=0.61 cavity and the beta= 0.81 exceeded the design values for gradient and Q - value: E{sub acc} = 1 0.3 MV/m and Q = 5 x 10{sup 9} at 2.1K for beta= 0.61 and E{sub acc} = 12.3 MV/m and Q = 5 x 10{sup 9} at 2.1K for beta= 0.81. One of the medium beta cavities has been equipped with an integrated helium vessel and measurements of the static and dynamic Lorentz force detuning will be done and compared to the ''bare'' cavities. In addition two single cell cavities have been fabricated, equipped with welded-on HOM couplers. They are being used to evaluate the HOM couplers with respect to multipacting, fundamental mode rejection and HOM damping as far as possible in a single cell. 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 this workshop.

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

    SciTech Connect

    McClintock, David A; Riemer, Bernie; Ferguson, Phillip D; Carroll, Adam J; Dayton, Michael J

    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 316L 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.

  3. Comparison of fission neutron and pulsed spallation neutron sources for radiation effects experiments on Cu/sub 3/Au

    SciTech Connect

    Kirk, M.A.

    1983-10-01

    Through our recent experimental work on the neutron irradiation effects in Cu/sub 3/Au, we will compare fission and pulsed spallation neutron sources. Neutron characteristics of irradiation facilities at the Intense Pulsed Neutron Source (IPNS) and the CP-5 reactor (now closed down), are briefly described. Defect cascade size distributions from irradiations of Cu/sub 3/Au at both neutron sources illustrated by transmission electron micrographs of disordered zones. Radiation-enhanced diffusion experiments in Cu/sub 3/Au are discussed along with the effect of pulsed neutron irradiations.

  4. Calculations of helium production in materials irradiated at spallation neutron sources

    SciTech Connect

    Corzine, R.K.; Dudziak, D.J.; Wechsler, M.S.; Barnett, M.H.; Mansur, L.K.

    1998-09-01

    Experience with materials irradiated in fission reactor neutron environments has shown that radiation-produced helium can exacerbate the degradation of properties caused by radiation-produced defects and defect clusters. Whereas fission-reactor neutron energies extend up to {approximately}10 MeV, the neutrons and protons at spallation neutron sources reach up to 1,000 to 2,000 MeV, and He production is much greater. For example, calculations have shown for the innermost shell of the containment vessel of the spallation neutron source, under collaborative design by several national laboratories led by the Oak Ridge National Laboratory, that full-power displacement and He production rates are {approximately}20 displacements per atom (dpa)/yr and 1,000 atomic parts per million (appm) He/yr, which corresponds to 50 appm He/dpa. By contrast, materials in fission reactor cores usually experience <1 appm He/dpa. In this paper, the authors summarize methods and results for the calculation of He production cross sections appropriate to the neutron and proton energies to which target and containment materials are exposed at spallation neutron sources. The principal calculational tool is LAHET or, more broadly, the LAHET code system (LCS).

  5. A facility for neutrino-nucleus cross-section measurements at the spallation neutron source

    NASA Astrophysics Data System (ADS)

    Efremenko, Yu.

    2005-01-01

    In this paper we discuss the possibility of building a neutrino facility at the Spallation Neutron Source presently under construction at ORNL. At such a facility an extensive long-term program can be established to study neutrino nucleus cross-sections in the range of interest for nuclear astrophysics and nuclear theory.

  6. Post-irradiation examination of the Spallation Neutron Source target module

    NASA Astrophysics Data System (ADS)

    McClintock, D. A.; Ferguson, P. D.; Mansur, L. K.

    2010-03-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is an accelerator-based pulsed neutron source that produces high-energy spallation neutrons by bombarding liquid mercury flowing through a stainless steel target vessel. During operation the proton beam and spallation neutrons produce radiation damage in the AISI 316L austenitic stainless steel target vessel and water-cooled shroud. The beam pulses also cause rapid heating of the liquid mercury, which may produce cavitation erosion damage on the inner surface of the target vessel. The cavitation erosion rate is thought to be highly sensitive to beam power and predicted to be the primary life-limiting factor of the target module. Though cavitation erosion and radiation damage to the target vessel are expected to dictate its lifetime, the effects of radiation damage and cavitation erosion to target vessels in liquid metal spallation systems are not well known. Therefore preparations are being undertaken to perform post-irradiation examination (PIE) of the liquid mercury target vessel and water-cooled shroud after end-of-life occurs. An overview of the planned PIE for the SNS target vessel is presented here, including proposed techniques for specimen acquisition and subsequent material properties characterization.

  7. BEAM-LOSS DRIVEN DESIGN OPTIMIZATION FOR THE SPALLATION NEUTRON SOURCE (SNS) RING.

    SciTech Connect

    WEI,J.; BEEBE-WANG,J.; BLASKIEWICZ,M.; CAMERON,P.; DANBY,G.; GARDNER,C.J.; JACKSON,J.; LEE,Y.Y.; LUDEWIG,H.; MALITSKY,N.; RAPARIA,D.; TSOUPAS,N.; WENG,W.T.; ZHANG,S.Y.

    1999-03-29

    This paper summarizes three-stage design optimization for the Spallation Neutron Source (SNS) ring: linear machine design (lattice, aperture, injection, magnet field errors and misalignment), beam core manipulation (painting, space charge, instabilities, RF requirements), and beam halo consideration (collimation, envelope variation, e-p issues etc.).

  8. The spin-echo spectrometer at the Spallation Neutron Source (SNS)

    NASA Astrophysics Data System (ADS)

    Ohl, M.; Monkenbusch, M.; Arend, N.; Kozielewski, T.; Vehres, G.; Tiemann, C.; Butzek, M.; Soltner, H.; Giesen, U.; Achten, R.; Stelzer, H.; Lindenau, B.; Budwig, A.; Kleines, H.; Drochner, M.; Kaemmerling, P.; Wagener, M.; Möller, R.; Iverson, E. B.; Sharp, M.; Richter, D.

    2012-12-01

    A novel neutron spin-echo spectrometer with superconducting main coils enabling enclosure by a double walled μ-metal magnetic shielding chamber has been built and set into operation at the spallation neutron source in Oak Ridge. The layout of the spectrometer is described. Performance with emphasis on the superconducting main solenoids and the time-of-flight operation is described. Data on resolution, stability and first experiments are shown.

  9. Comparison of Different INC Physical Models of MCNPX to Compute Spallation Neutronics of LBE Target

    NASA Astrophysics Data System (ADS)

    Feghhi, Seyed Amir Hossein; Gholamzadeh, Zohreh; Tenreiro, Claudio; Alipoor, Zahra

    2015-04-01

    Spallation particles can utilize in different fields such as neutron scattering studies, external source for burning spent fuel as well as running subcritical reactors. Different computational particle transport codes are widely used to model spallation process into the heavy targets. Among these codes, MCNPX 2.6.0 comprises various intra nuclear cascade models for spallation calculations. Impact of different intra nuclear cascade models on calculation of neutronic parameters of LBE target has been evaluated in this work. Escaped neutron yield, energy deposition and residual nuclei production in the spallation target has been calculated using the physical models. A comparison between the computational and experimental has been carried out to validate the computational data. The simulation data showed there is a good conformity between the obtained data from Bertini/Drenser and Isabel/Drenser. The data achieved by Bertini/Abla and Isabel/Abla models are close to each other for the studied parameters as well. Among the studied models, CEM showed more discrepancies with experimental and other computational data. According to the obtained data, INCL4/Drenser, INCL4/Abla and Isabel/Drenser models can meet more agreements with experimental data.

  10. Benchmarking shielding simulations for an accelerator-driven spallation neutron source

    NASA Astrophysics Data System (ADS)

    Cherkashyna, Nataliia; DiJulio, Douglas D.; Panzner, Tobias; Rantsiou, Emmanouela; Filges, Uwe; Ehlers, Georg; Bentley, Phillip M.

    2015-08-01

    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 monolith 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.

  11. Pre-conceptual design and preliminary neutronic analysis of the proposed National Spallation Neutron Source (NSNS)

    SciTech Connect

    Johnson, J.O.; Barnes, J.M.; Charlton, L.A.

    1997-03-01

    The Department of Energy (DOE) has initiated a pre-conceptual design study for the National Spallation Neutron Source (NSNS) and given preliminary approval for the proposed facility to be built at Oak Ridge National Laboratory (ORNL). The pre-conceptual design of the NSNS initially consists of an accelerator system capable of delivering a 1 to 2 GeV proton beam with 1 MW of beam power in an approximate 0.5 {micro}s pulse at a 60 Hz frequency onto a single target station. The NSNS will be upgradable to a significantly higher power level with two target stations (a 60 Hz station and a 10 Hz station). There are many possible layouts and designs for the NSNS target stations. This paper gives a brief overview of the proposed NSNS with respect to the target station, as well as the general philosophy adopted for the neutronic design of the NSNS target stations. A reference design is presented, and some preliminary neutronic results for the NSNS are briefly discussed.

  12. Precompound emission of energetic light fragments in spallation reactions

    NASA Astrophysics Data System (ADS)

    Kerby, Leslie Marie

    Emission of light fragments (LF) from nuclear reactions is an open question. Different reaction mechanisms contribute to their production; the relative roles of each, and how they change with incident energy, mass number of the target, and the type and emission energy of the fragments is not completely understood. None of the available models are able to accurately predict emission of LF from arbitrary reactions. However, the ability to describe production of LF (especially at energies ~ 30 MeV) from many reactions is important for different applications, such as cosmic-ray-induced Single Event Upsets (SEUs), radiation protection, and cancer therapy with proton and heavy-ion beams, to name just a few. The Cascade-Exciton Model (CEM) version 03.03 and the Los Alamos version of the Quark-Gluon String Model (LAQGSM) version 03.03 event generators in Monte Carlo N-Particle Transport Code version 6 (MCNP6) describe quite well the spectra of fragments with sizes up to 4He across a broad range of target masses and incident energies (up to ~ 5 GeV for CEM and up to ~1 TeV/A for LAQGSM). However, they do not predict the high-energy tails of LF spectra heavier than 4He well. Most LF with energies above several tens of MeV are emitted during the precompound stage of a reaction. The current versions of the CEM and LAQGSM event generators do not account for precompound emission of LF larger than 4He. The aim of our work is to extend the precompound model in them to include such processes, leading to an increase of predictive power of LF-production in MCNP6. This entails upgrading the Modified Exciton Model currently used at the preequilibrium stage in CEM and LAQGSM. It also includes expansion and examination of the coalescence and Fermi break-up models used in the precompound stages of spallation reactions within CEM and LAQGSM. Extending our models to include emission of fragments heavier than 4He at the precompound stage has indeed provided results that have much better

  13. Dissertation: Precompound Emission of Energetic Light Fragments in Spallation Reactions

    SciTech Connect

    Kerby, Leslie Marie

    2015-08-04

    Emission of light fragments (LF) from nuclear reactions is an open question. Different reaction mechanisms contribute to their production; the relative roles of each, and how they change with incident energy, mass number of the target, and the type and emission energy of the fragments is not completely understood. None of the available models are able to accurately predict emission of LF from arbitrary reactions. However, the ability to describe production of LF (especially at energies ≳ 30 MeV) from many reactions is important for different applications, such as cosmic-ray-induced Single Event Upsets (SEUs), radiation protection, and cancer therapy with proton and heavy-ion beams, to name just a few. The Cascade-Exciton Model (CEM) version 03.03 and the Los Alamos version of the Quark-Gluon String Model (LAQGSM) version 03.03 event generators in Monte Carlo N-Particle Transport Code version 6 (MCNP6) describe quite well the spectra of fragments with sizes up to ⁴He across a broad range of target masses and incident energies (up to ~ 5 GeV for CEM and up to ~ 1 TeV/A for LAQGSM). However, they do not predict the high energy tails of LF spectra heavier than ⁴He well. Most LF with energies above several tens of MeV are emitted during the precompound stage of a reaction. The current versions of the CEM and LAQGSM event generators do not account for precompound emission of LF larger than ⁴He. The aim of our work is to extend the precompound model in them to include such processes, leading to an increase of predictive power of LF-production in MCNP6. This entails upgrading the Modified Exciton Model currently used at the preequilibrium stage in CEM and LAQGSM. It also includes expansion and examination of the coalescence and Fermi break-up models used in the precompound stages of spallation reactions within CEM and LAQGSM. Extending our models to include emission of fragments heavier than ⁴He at the precompound stage has indeed provided results that have much

  14. A Long-Pulse Spallation Source at Los Alamos: Facility description and preliminary neutronic performance for cold neutrons

    SciTech Connect

    Russell, G.J.; Weinacht, D.J.; Pitcher, E.J.; Ferguson, P.D.

    1998-03-01

    The Los Alamos National Laboratory has discussed installing a new 1-MW spallation neutron target station in an existing building at the end of its 800-MeV proton linear accelerator. Because the accelerator provides pulses of protons each about 1 msec in duration, the new source would be a Long Pulse Spallation Source (LPSS). The facility would employ vertical extraction of moderators and reflectors, and horizontal extraction of the spallation target. An LPSS uses coupled moderators rather than decoupled ones. There are potential gains of about a factor of 6 to 7 in the time-averaged neutron brightness for cold-neutron production from a coupled liquid H{sub 2} moderator compared to a decoupled one. However, these gains come at the expense of putting ``tails`` on the neutron pulses. The particulars of the neutron pulses from a moderator (e.g., energy-dependent rise times, peak intensities, pulse widths, and decay constant(s) of the tails) are crucial parameters for designing instruments and estimating their performance at an LPSS. Tungsten is the reference target material. Inconel 718 is the reference target canister and proton beam window material, with Al-6061 being the choice for the liquid H{sub 2} moderator canister and vacuum container. A 1-MW LPSS would have world-class neutronic performance. The authors describe the proposed Los Alamos LPSS facility, and show that, for cold neutrons, the calculated time-averaged neutronic performance of a liquid H{sub 2} moderator at the 1-MW LPSS is equivalent to about 1/4th the calculated neutronic performance of the best liquid D{sub 2} moderator at the Institute Laue-Langevin reactor. They show that the time-averaged moderator neutronic brightness increases as the size of the moderator gets smaller.

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

    NASA Astrophysics Data System (ADS)

    McClintock, D. A.; Riemer, B. W.; Ferguson, P. D.; Carroll, A. J.; Dayton, M. J.

    2012-12-01

    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 fully prototypic 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 316L target material and the extent of cavitation-induced erosion to the mercury 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.

  16. Stripper foil failure modes and cures at the Oak Ridge Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Plum, M. A.; Cousineau, S. M.; Galambos, J.; Kim, S. H.; Ladd, P.; Luck, C. F.; Peters, C. C.; Polsky, Y.; Shaw, R. W.; Macek, R. J.; Raparia, D.

    2011-03-01

    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 H0 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 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.

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

    SciTech Connect

    Plum, M.A.; Raparia, D.; Cousineau, S.M.; Galambos, J.; Kim, S.H.; Ladd, P.; Luck, C.F.; Peters, C.C.; Polsky, Y.; Shaw, R.W.; Macek, R.J.

    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 around 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.

  18. Stripper foil failure modes and cures at the Spallation Neutron Source

    SciTech Connect

    Cousineau, Sarah M; Galambos, John D; Kim, Sang-Ho; Ladd, Peter; Luck, Chris; Peters, Charles C; Polsky, Yarom; Shaw, Robert W; Raparia, Deepak; Macek, Robert James; Plum, Michael A

    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 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.

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

    SciTech Connect

    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 beam 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

  20. Prototype Spallation Neutron Source Rotating Target Assembly Final Test Report

    SciTech Connect

    McManamy, Thomas J; Graves, Van; Garmendia, Amaia Zarraoa; Sorda, Fernando; Etxeita, Borja; Rennich, Mark J

    2011-01-01

    A full-scale prototype of an extended vertical shaft, rotating target assembly based on a conceptual target design for a 1 to 3-MW spallation facility was built and tested. Key elements of the drive/coupling assembly implemented in the prototype include high integrity dynamic face seals, commercially available bearings, realistic manufacturing tolerances, effective monitoring and controls, and fail-safe shutdown features. A representative target disk suspended on a 3.5 meter prototypical shaft was coupled with the drive to complete the mechanical tests. Successful operation for 5400 hours confirmed the overall mechanical feasibility of the extended vertical shaft rotating target concept. The prototype system showed no indications of performance deterioration and the equipment did not require maintenance or relubrication.

  1. THERMAL HYDRAULIC ANALYSIS OF A LIQUID-METAL-COOLED NEUTRON SPALLATION TARGET

    SciTech Connect

    W. GREGORY; R. MARTIN; T. VALACHOVIC

    2000-07-01

    We have carried out numerical simulations of the thermal hydraulic behavior of a neutron spallation target where liquid metal lead-bismuth serves as both coolant and as a neutron spallation source. The target is one of three designs provided by the Institute of Physics and Power Engineering (IPPE) in Russia. This type of target is proposed for Accelerator-driven Transmutation of Waste (ATW) to eliminate plutonium from hazardous fission products. The thermal hydraulic behavior was simulated by use of a commercial CFD computer code called CFX. Maximum temperatures in the diaphragm window and in the liquid lead were determined. In addition the total pressure drop through the target was predicted. The results of the CFX analysis were close to those results predicted by IPPE in their preliminary analysis.

  2. Neutron guide optimisation for a time-of-flight neutron imaging instrument at the European Spallation Source.

    PubMed

    Hilger, A; Kardjilov, N; Manke, I; Zendler, C; Lieutenant, K; Habicht, K; Banhart, J; Strobl, M

    2015-01-12

    A neutron transport system for the planned imaging instrument ODIN at the future European Spallation Source (ESS) based on neutron optical components was designed and optimized. Different ways of prompt pulse suppression were studied. The spectral performance of the optimal neutron guide configuration is presented. In addition, the influence of the gaps in the guide system needed for the required chopper configuration was investigated. Given that the requirements for an imaging instrument located on a long guide system and hosting a complex chopper system are extremely demanding in terms of spectral and divergence needs, this study can be beneficial for a wide range of instruments in various ways. PMID:25835677

  3. Coherent Scattering Investigations at the Spallation Neutron Source: a Snowmass White Paper

    SciTech Connect

    Akimov, D.; Bernstein, A.; BarbeauP.,; Barton, P. J.; Bolozdynya, A.; Cabrera-Palmer, B.; Cavanna, F.; Cianciolo, Vince; Collar, J.; Cooper, R. J.; Dean, D. J.; Efremenko, Yuri; Etenko, A.; Fields, N.; Foxe, M.; Figueroa-Feliciano, E.; Fomin, N.; Gallmeier, F.; Garishvili, I.; Gerling, M.; Green, M.; Greene, Geoffrey; Hatzikoutelis, A.; Henning, Reyco; Hix, R.; Hogan, D.; Hornback, D.; Jovanovic, I.; Hossbach, T.; Iverson, Erik B; Klein, S. R.; Khromov, A.; Link, J.; Louis, W.; Lu, W.; Mauger, C.; Marleau, P.; Markoff, D.; Martin, R. D.; Mueller, Paul Edward; Newby, J.; Orrell, John L.; O'Shaughnessy, C.; Penttila, Seppo; Patton, K.; Poon, A. W.; Radford, David C; Reyna, D.; Ray, H.; Scholberg, K.; Sosnovtsev, V.; Tayloe, R.; Vetter, K.; Virtue, C.; Wilkerson, J.; Yoo, J.; Yu, Chang-Hong

    2013-01-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, Tennessee, provides an intense flux of neutrinos in the few tens-of-MeV range, with a sharply-pulsed timing structure that is beneficial for background rejection. In this white paper, we describe how the SNS source can be used for a measurement of coherent elastic neutrino-nucleus scattering (CENNS), and the physics reach of different phases of such an experimental program (CSI: Coherent Scattering Investigations at the SNS).

  4. RESULTS OF BACKGROUND SUBTRACTION TECHNIQUES ON THE SPALLATION NEUTRON SOURCE BEAM LOSS MONITORS

    SciTech Connect

    Pogge, James R; Zhukov, Alexander P

    2010-01-01

    Recent improvements to the Spallation Neutron Source (SNS) beam loss monitor (BLM) designs have been made with the goal of significantly reducing background noise. This paper outlines this effort and analyzes the results. The significance of this noise reduction is the ability to use the BLM sensors [1], [2], [3] distributed throughout the SNS accelerator as a method to monitor activation of components as well as monitor beam losses.

  5. Monitoring method for neutron flux for a spallation target in an accelerator driven sub-critical system

    NASA Astrophysics Data System (ADS)

    Zhao, Qiang, He, Zhi-Yong; Yang, Lei; Zhang, Xue-Ying; Cui, Wen-Juan; Chen, Zhi-Qiang; Xu, Hu-Shan

    2016-07-01

    In this paper, we study a monitoring method for neutron flux for the spallation target used in an accelerator driven sub-critical (ADS) system, where a spallation target located vertically at the centre of a sub-critical core is bombarded vertically by high-energy protons from an accelerator. First, by considering the characteristics in the spatial variation of neutron flux from the spallation target, we propose a multi-point measurement technique, i.e. the spallation neutron flux should be measured at multiple vertical locations. To explain why the flux should be measured at multiple locations, we have studied neutron production from a tungsten target bombarded by a 250 MeV-proton beam with Geant4-based Monte Carlo simulations. The simulation results indicate that the neutron flux at the central location is up to three orders of magnitude higher than the flux at lower locations. Secondly, we have developed an effective technique in order to measure the spallation neutron flux with a fission chamber (FC), by establishing the relation between the fission rate measured by FC and the spallation neutron flux. Since this relation is linear for a FC, a constant calibration factor is used to derive the neutron flux from the measured fission rate. This calibration factor can be extracted from the energy spectra of spallation neutrons. Finally, we have evaluated the proposed calibration method for a FC in the environment of an ADS system. The results indicate that the proposed method functions very well. Supported by Strategic Priority Research Program of Chinese Academy of Sciences (XDA03010000 and XDA03030000) and the National Natural Science Foundation of China(91426301).

  6. 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.

  7. Assessment of the neutron cross section database for mercury for the ORNL spallation source

    SciTech Connect

    Leal, L.C.; Spencer, R.R.; Ingersoll, D.T.; Gabriel, T.A.

    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 survey 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.

  8. Defect clusters formed from large collision cascades in fcc metals irradiated with spallation neutrons

    NASA Astrophysics Data System (ADS)

    Satoh, Y.; Matsuda, Y.; Yoshiie, T.; Kawai, M.; Matsumura, H.; Iwase, H.; Abe, H.; Kim, S. W.; Matsunaga, T.

    2013-11-01

    Fcc pure metals were irradiated with spallation neutrons (energies up to 500 MeV) at room temperature to a neutron fluence of 1 × 1018 n m-2 at KENS, High Energy Accelerator Research Organization (KEK). Defect clusters induced by large collision cascades were examined using transmission electron microscopy (TEM). In Au, large groups of defects included more than 10 clusters, and the damage zone extended over 50 nm, which was larger than that induced by fusion neutron irradiation (<20 nm). Although small stacking fault tetrahedra (SFT) are formed in subcascades by fission and fusion neutron irradiation, dislocation loops were also observed in the present experiments. Large dislocation loops (>10 nm) were identified as vacancy type by the conventional inside-outside contrast method. Because of the low neutron fluence, spatial overlapping of collision cascades was ignored. Large vacancy loops are formed through cooperative reactions among subcascades in a single collision cascade with large recoil energy.

  9. High-energy in-beam neutron measurements of metal-based shielding for accelerator-driven spallation neutron sources

    NASA Astrophysics Data System (ADS)

    DiJulio, D. D.; Cooper-Jensen, C. P.; Björgvinsdóttir, H.; Kokai, Z.; Bentley, P. M.

    2016-05-01

    Metal-based shielding plays an important role in the attenuation of harmful and unwanted radiation at an accelerator-driven spallation neutron source. At the European Spallation Source, currently under construction in Lund, Sweden, metal-based materials are planned to be used extensively as neutron guide substrates in addition to other shielding structures around neutron guides. The usage of metal-based materials in the vicinity of neutron guides however requires careful consideration in order to minimize potential background effects in a neutron instrument at the facility. Therefore, we have carried out a combined study involving high-energy neutron measurements and Monte Carlo simulations of metal-based shielding, both to validate the simulation methodology and also to investigate the benefits and drawbacks of different metal-based solutions. The measurements were carried out at The Svedberg Laboratory in Uppsala, Sweden, using a 174.1 MeV neutron beam and various thicknesses of aluminum-, iron-, and copper-based shielding blocks. The results were compared to geant4 simulations and revealed excellent agreement. Our combined study highlights the particular situations where one type of metal-based solution may be preferred over another.

  10. Energy Dissipation in the Target Station of the Spallation Neutron Source

    SciTech Connect

    Charlton, L.A.; Difilippo, F.C.

    1999-09-27

    The heat distributions within the components of the target station of the Spallation Neutron Source were calculated using the Monte Carlo codes HETC, LAHET and MCNP to track the cascade of events after the introduction of 1 GeV protons in the mercury target. The boundaries of the model are the proton window and the external reflectors and includes such components as the stainless steel container, the water coolant, the thermal and cold neutron sources and the beam tubes. The calculations show that detailed heat distributions are sensitive to the proton beam profile and the curvature of the surface penetrated by the proton beam.

  11. The performance of neutron spectrometers AR a long-pulse spallation source

    SciTech Connect

    Pynn, R.; Daemen, L.L.

    1995-12-01

    At a recent workshop at Lawrence Berkeley National Laboratory members of the international neutron scattering community discussed the performance to be anticipated from neutron scattering instruments installed at a 1 MW long-pulse spallation source (LPSS). Although the report of this workshop is long, its principal conclusions can be easily summarised and almost as easily understood. This article presents such a synthesis for a 60 Hz LPSS with 1 msec proton pulses. We discuss some of the limitations of the workshop conclusions and suggest a simple analysis of the performance differences that might be expected between short- and long-pulse sources both of which exploit coupled moderators.

  12. Plans for a Collaboratively Developed Distributed Control System for the Spallation Neutron Source

    SciTech Connect

    DeVan, W.R.; Gurd, D.P.; Hammonds, J.; Lewis, S.A.; Smith, J.D.

    1999-03-29

    The Spallation Neutron Source (SNS) is an accelerator-based pulsed neutron source to be built in Oak Ridge, Tennessee. The facility has five major sections - a ''front end'' consisting of a 65 keV H{sup -} ion source followed by a 2.5 MeV RFQ; a 1 GeV linac; a storage ring; a 1MW spallation neutron target (upgradeable to 2 MW); the conventional facilities to support these machines and a suite of neutron scattering instruments to exploit them. These components will be designed and implemented by five collaborating institutions: Lawrence Berkeley National Laboratory (Front End), Los Alamos National Laboratory (Linac); Brookhaven National Laboratory (Storage Ring); Argonne National Laboratory (Instruments); and Oak Ridge National Laboratory (Neutron Source and Conventional Facilities). It is proposed to implement a fully integrated control system for all aspects of this complex. The system will be developed collaboratively, with some degree of local autonomy for distributed systems, but centralized accountability. Technical integration will be based upon the widely-used EPICS control system toolkit, and a complete set of hardware and software standards. The scope of the integrated control system includes site-wide timing and synchronization, networking and machine protection. This paper discusses the technical and organizational issues of planning a large control system to be developed collaboratively at five different institutions, the approaches being taken to address those issues, as well as some of the particular technical challenges for the SNS control system.

  13. Neutronic performance of the MEGAPIE spallation target under high power proton beam

    NASA Astrophysics Data System (ADS)

    Michel-Sendis, F.; Chabod, S.; Letourneau, A.; Panebianco, S.; Zanini, L.

    2010-07-01

    The MEGAPIE project, aiming at the construction and operation of a megawatt liquid lead-bismuth spallation target, constitutes the first step in demonstrating the feasibility of liquid heavy metal target technologies as spallation neutron sources. In particular, MEGAPIE is meant to assess the coupling of a high power proton beam with a window-concept heavy liquid metal target. The experiment has been set at the Paul Scherrer Institute (PSI) in Switzerland and, after a 4-month long irradiation, has provided unique data for a better understanding of the behavior of such a target under realistic irradiation conditions. A complex neutron detector has been developed to provide an on-line measurement of the neutron fluency inside the target and close to the proton beam. The detector is based on micrometric fission chambers and activation foils. These two complementary detection techniques have provided a characterization of the neutron flux inside the target for different positions along its axis. Measurements and simulation results presented in this paper aim to provide important recommendations for future accelerator driven systems (ADS) and neutron source developments.

  14. A high power accelerator driver system for spallation neutron sources

    SciTech Connect

    Jason, A.; Blind, B.; Channell, P.

    1996-07-01

    This is the final report of a two-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). For several years, the Los Alamos Meson Physics Facility (LAMPF) and the Proton Storage Ring (PSR) have provided a successful driver for the nearly 100-kW Los Alamos Neutron Scattering Center (LANSCE) source. The authors have studied an upgrade to this system. The goal of this effort was to establish a credible design for the accelerator driver of a next-generation source providing 1-MW of beam power. They have explored a limited subset of the possible approaches to a driver and have considered only the low 1-MW beam power. The next-generation source must utilize the optimum technology and may require larger neutron intensities than they now envision.

  15. Target designs for the Brookhaven National Laboratory 5-MW pulsed spallation neutron source

    SciTech Connect

    Ludewig, H.; Todosow, M.; Powell, J.R.

    1996-03-01

    A feasibility study of a compact high power density target for a spallation neutron source was under-taken. The target arrangement consists primarily of heavy metal, with appropriate cooling passages. A high intensity proton beam of intermediate energy is directed at the target, where it interacts with the heavy metal nuclei. The subsequent spallation reactions produce several neutrons per proton resulting in an intense neutron source. The proton beam is assumed to havean energy of 5 MW, and to be cyclic with a repetition rate of 10Hz and 50Hz. The study was divided into two broad sections. First, an analysis of preliminary target designs was undertaken to ensure the overall feasibility of the concepts involved in the design and eventual construction of such a high power density target. Second, two proposed target designs, based on the first set of analyses, are investigated in more detail. Special care is taken to ensure that the neutron fluxes in the moderator are at the desired level no material compatibility problems exist,and the target is able to operate in a reliable and safe manner. Several target materials, coolant types, and target arrangements are investigated in the first section. The second section concentrates on a single target material and geometric arrangement. However, several structural material choices continue to be investigated with the aim of minimizing the effects of structural heating, and associated thermally induced stresses. In the final section the conclusions of this preliminary study are summarized.

  16. Three-dimensional computational fluid dynamics for the Spallation Neutron Source liquid mercury target

    SciTech Connect

    Wendel, M.W.; Siman-Tov, M.

    1998-11-01

    The Spallation Neutron Source (SNS) is a high-power accelerator-based pulsed spallation source being designed by a multilaboratory team led by Oak Ridge National Laboratory (ORNL) to achieve high fluxes of neutrons for scientific experiments. Computational fluid dynamics (CFD) is being used to analyze the SNS design. The liquid-mercury target is subjected to the neutronic (internal) heat generation that results from the proton collisions with the mercury nuclei. The liquid mercury simultaneously serves as the neutronic target medium, transports away the heat generated within itself, and cools the metallic target structure. Recirculation and stagnation zones within the target are of particular concern because of the likelihood that they will result in local hot spots. These zones exist because the most feasible target designs include a complete U-turn flow redirection. Although the primary concern is that the target is adequately cooled, the pressure drop from inlet to outlet must also be considered because pressure drop directly affects structural loading and required pumping power. Based on the current design, a three-dimensional CFD model has been developed that includes the stainless steel target structure, the liquid-mercury target flow, and the liquid-mercury cooling jacket that wraps around the nose of the target.

  17. European Spallation Source

    NASA Astrophysics Data System (ADS)

    Eshraqi, Mohammad; McGinnis, David; Lindroos, Mats

    The following sections are included: * Neutron usage and historical background * Spallation * History of spallation sources * The ESS facility * The ESS linac * Beam physics * The front-end and the normal conducting linac * Superconducting linac * RF sources * Summary * References

  18. 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.

  19. Barites - Anomalous xenon from spallation and neutron-induced reactions

    NASA Technical Reports Server (NTRS)

    Srinivasan, B.

    1976-01-01

    Sedimentary barites from South Africa and Western Australia (about 3 billion years old) contain spallogenic Xe isotopes produced by reactions of Ba with nuclear-active particles in cosmic rays. 'Surface residence time' of these samples was calculated from the observed concentrations of spallogenic Xe-126. Comparison of spallogenic ratios of Xe-131/Xe-126 in the two samples provides evidence for the reaction Ba-130(n, gamma) yields Xe-131, which is characterized by a large number of resonances for neutron absorption in the epithermal region. This observation lends additional support to the conclusions already reached regarding the origin of anomalous Xe-131 in lunar samples.

  20. STUDY OF A 10-MW CONTINUOUS SPALLATION NEUTRON SOURCE.

    SciTech Connect

    RUGGIERO,A.G.LUDEWIG,H.SHAPIRO,S.

    2003-05-12

    This paper reports on the feasibility study of a proton Super-Conducting Linac as the driver for an Accelerator-based Continuous Neutron Source (ACNS) [1] to be located at Brookhaven National Laboratory (BNL). The Linac is to be operated in the Continuous Wave (CW) mode to produce an average 10 MW of beam power. The Linac beam energy is taken to be 1.25 GeV. The required average proton beam intensity in exit is then 8 mA.

  1. Neutron Emission Spectra from Inelastic Scattering on 58,60Ni with a White Neutron Source at FIGARO

    SciTech Connect

    Rochman, D.; Haight, R.C.; O'Donnell, J. M.; Devlin, M.; Ethvignot, T.; Granier, T.; Grimes, S.M.; Talou, P.

    2005-05-24

    Neutron emission spectra from inelastic neutron scattering on natural nickel at the FIGARO facility have been measured by a double time-of-flight technique. The incident neutrons are produced from the spallation source of the Weapons Neutron Research facility, and their energies are determined by time of flight. The emitted neutrons and gamma rays are detected by 16 liquid scintillators and one high-resolution germanium or one barium-fluoride detector, respectively. The results for incident neutron energies from 2 to 10 MeV are compared with predictions of nuclear model calculations performed with the code EMPIRE-II. Finally, the level density parameters 'a' and ''{delta}'' are extracted.

  2. Energy-Deposition and Damage Calculations in Core-Vessel Inserts at the Spallation Neutron Source

    SciTech Connect

    Murphy, B.D.

    2002-06-25

    Heat-deposition and damage calculations are described for core-vessel inserts in the target area of the Spallation Neutron Source. Two separate designs for these inserts (or neutron beam tubes) were studied; a single-unit insert and a multi-unit insert. The single unit contains a neutron guide; the multi unit does not. Both units are constructed of stainless steel. For the single unit, separate studies were carried out with the guide composed of stainless steel, glass, and aluminum. Results are also reported for an aluminum window on the front of the insert, a layer of nickel on the guide, a cadmium shield surrounding the guide, and a stainless steel plug in the beam-tube opening. The locations of both inserts were the most forward positions to be occupied by each design respectively thus ensuring that the calculations are conservative.

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

    SciTech Connect

    Zolnierczuk, Piotr A; Vacaliuc, Bogdan; Sundaram, Madhan; Parizzi, Andre A; Halbert, Candice E; Hoffmann, Michael C; Greene, Gayle C; Browning, Jim; Ankner, John Francis

    2013-01-01

    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, implemented 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.

  4. Spallation neutron source saddle antenna H{sup -} ion source project

    SciTech Connect

    Dudnikov, Vadim; Johnson, Rolland P.; Dudnikova, Galina; Stockli, Martin; Welton, Robert

    2010-02-15

    In this project we are developing an H{sup -} source which will synthesize the most important developments in the field of negative ion sources to provide high current, high brightness, good lifetime, high reliability, and high power efficiency. We describe two planned modifications to the present spallation neutron source external antenna source in order to increase the plasma density near the output aperture: (1) replacing the present 2 MHz plasma-forming solenoid antenna with a 13 MHz saddle-type antenna and (2) replacing the permanent multicusp magnetic system with a weaker electromagnet.

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

    SciTech Connect

    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.

  6. Stabilized operation of the improvement of the Spallation Neutron Source (SNS) radio-frequency quadrupole (RFQ)

    SciTech Connect

    Kim, Sang-Ho; Aleksandrov, Alexander V; Crofford, Mark T; Galambos, John D; Gibson, Paul E; Hardek, Thomas W; Henderson, Stuart D; Kang, Yoon W; Kasemir, Kay; Peters, Charles C; Thompson, David H; Stockli, Martin P; Williams, Derrick C

    2010-01-01

    The Spallation Neutron Source (SNS) radio-frequency quadrupole (RFQ) had resonance control instabilities at duty factors higher than approximately four percent. Systematic investigations have been carried out to understand the cause of the instability and to ensure the operational stability of the RFQ. The most critical source of the instability is revealed to be an interaction between hydrogen released by beam bombardments and the RFQ RF field resulting in a discharge, which consumes additional RF power and could cause the RFQ to operate in an unstable region. This paper reports improvement of the SNS RFQ operational stability based on the findings during the SNS operation.

  7. Comparison of synchrotron and accumulator scenarios for a 5-MW Pulsed Spallation Neutron Source

    SciTech Connect

    Blumberg, L.; Luccio, A.; Ruggiero, A.G.; Steenberg, A. van

    1996-07-01

    This paper reports conceptual design studies of a site-independent 5 MW Pulsed Spallation Neutron Source (PSNS) conducted by an interdepartmental study group at Brookhaven National Laboratory. First, a scenario based on the use of a 600 MeV Linac followed by two fast cycling 3.6 GeV Synchrotrons was investigated. Then we studied an Accumulator with two options: (1) a 1.25 GeV normal conducting Linac followed by two Accumulator Rings, and (2) a 2.4 GeV superconducting Linac followed by a single Accumulator Ring.

  8. COLLECTIVE EFFECTS AND THEIR CONTROL AT THE SPALLATION NEUTRON SOURCE RING.

    SciTech Connect

    WEI,J.; BLASKIEWICZ,M.; BRODOWSKI,J.; CAMERON,P.; DAVINO,D.; FEDOTOV,A.; HAHAN,H.; HSEUH,H.; LEE,Y.Y.; RAPARIA,D.; ZHANG,S.Y.; ET AL

    2002-06-03

    One of the primary tasks in the design of the Spallation Neutron Source (SNS) ring is to control collective effects including space charge, transverse and longitudinal instabilities, and electron cloud. Transverse painting is used to alleviate space charge force; longitudinal painting along with chromatic sextupoles are used to enhance Landau damping; injection kicker vacuum pipes are carefully shielded, and extraction kicker impedances are measured in detail and optimized; beam halo, beam loss and electron production are minimized; finally, damping systems at various frequencies are planned. This paper summarizes these design implementations.

  9. Emittance studies of the Spallation Neutron Source external-antenna H{sup -} ion source

    SciTech Connect

    Han, B. X.; Stockli, M. P.; Welton, R. F.; Pennisi, T. R.; Murray, S. N.; Santana, M.; Long, C. D.

    2010-02-15

    A new Allison-type emittance scanner has been built to characterize the ion sources and low energy beam transport systems at Spallation Neutron Source. In this work, the emittance characteristics of the H{sup -} beam produced with the external-antenna rf-driven ion source and transported through the two-lens electrostatic low energy beam transport are studied. The beam emittance dependence on beam intensity, extraction parameters, and the evolution of the emittance and twiss parameters over beam pulse duration are presented.

  10. Testing Procedures and Results of the Prototype Fundamental Power Coupler for the Spallation Neutron Source

    SciTech Connect

    Stirbet, M; Campisi, I E; Daly, E F; Davis, G K; Drury, M; Kneisel, P; Myneni, G; Powers, T; Schneider, W J; Wilson, K M; Kang, Y; Cummings, K A; Hardek, T

    2001-06-01

    High-power RF testing with peak power in excess of 500 kW has been performed on prototype Fundamental Power Couplers (FPC) for the Spallation Neutron Source superconducting (SNS) cavities. The testing followed the development of procedures for cleaning, assembling and preparing the FPC for installation in the test stand. The qualification of the couplers has occurred for the time being only in a limited set of conditions (travelling wave, 20 pps) as the available RF system and control instrumentation are under improvement.

  11. TESTING PROCEDURES AND RESULTS OF THE PROTOTYPE FUNDAMENTAL POWER COUPLER FOR THE SPALLATION NEUTRON SOURCE

    SciTech Connect

    M. STIRBET; I.E. CAMPISI; ET AL

    2001-06-01

    High-power RF testing with peak power in excess of 500 kW has been performed on prototype Fundamental Power Couplers (FPC) for the Spallation Neutron Source superconducting (SNS) cavities. The testing followed the development of procedures for cleaning, assembling and preparing the FPC for installation in the test stand. The qualification of the couplers has occurred for the time being only in a limited set of conditions (travelling wave, 20 pps) as the available RF system and control instrumentation are under improvement.

  12. Low-energy beam transport studies supporting the Spallation Neutron Source 1-MW beam operationa

    SciTech Connect

    Han, Baoxi; Kalvas, T.; Tarvainen, O.; Welton, Robert F; Murray Jr, S N; Pennisi, Terry R; Santana, Manuel; Stockli, Martin P

    2012-01-01

    The H- injector consisting of a cesium enhanced RF-driven ion source and a 2-lens electrostatic low-energy beam transport (LEBT) system supports the Spallation Neutron Source 1-MW beam operation with ~38 mA beam current in the linac at 60 Hz with a pulse length of up to ~1.0 ms. In this work, two important issues associated with the low-energy beam transport are discussed: 1) inconsistent dependence of the post-RFQ beam current on the ion source tilt angle, and 2) high power beam losses on the LEBT electrodes under some off-nominal conditions compromising their reliability.

  13. ASSESSMENT OF THERMAL SHOCK ATTENUATION IN THE PARTICLE BED OF THE SPALLATION NEUTRON SOURCE COLLIMATOR.

    SciTech Connect

    SIMOS,N.; LUDEWIG,H.; WALKER,J.; CATALAN-LASHERAS,N.; WEI,J.; TODOSOW,M.

    2000-06-30

    A thermal shock analysis in a particle bed that surrounds the Spallation Neutron Source (SNS) beam tube in the various collimation locations is performed using a detailed thermal/stress wave propagation formulation. The goal of this effort is to assess the response of the particle bed when subjected to the full proton beam under off-normal operating conditions and its ability to attenuate the induced stress shock. Conclusions are drawn on the basis of comparison between the responses of (a) the individual particle bed elements, (b) an arrangement of elements comprising the particle bed and (c) an equivalent porous-less material with the density of the particle bed.

  14. Ring energy and current considerations for spallation neutron source

    SciTech Connect

    Blumberg, L.N.

    1994-04-01

    The most desirable energy E{sub o} of protons from the synchrotron and thus beam current {bar I} to produced a given beam power P{sub B} involves a balanced consideration of neutron production capability, accelerator beam stability, user requirements, and cost considerations. The present solution consists of two 3.6-GeV rings with a 600-MeV Linac injector, a compromise between conflicting factors of cost and technical concern. The authors believe that the design is a conservative one. They could increase the beam energy and/or the repetition rate and thereby decrease the requirement for the number of protons N{sub o} in the ring which in the present design is an extrapolation of about a factor of 7 from existing ring intensities. However, the specified ring acceptance appears quite adequate to contain the required 1.45 10{sup 14} protons/ring and the resulting loss in the target window and target are reasonable. The beam power and current are indeed modest in terms of window and target integrity compared to the 200 MW, 200mA 1-GeV design for the APT. The two-ring approach also offers several practical advantages -- the project is stageable in the sense that only one ring may be required initially to achieve P{sub B} = 2.5 MW power on the target with subsequent expansion to 5 MW with addition of the second ring. Two rings also provide additional reliability in the sense that the user program need not be interrupted by failure of one ring.

  15. 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. PMID:22852718

  16. A comparison of four direct geometry time-of-flight spectrometers at the Spallation Neutron Source.

    PubMed

    Stone, M B; Niedziela, J L; Abernathy, D L; DeBeer-Schmitt, L; Ehlers, G; Garlea, O; Granroth, G E; Graves-Brook, M; Kolesnikov, A I; Podlesnyak, A; Winn, B

    2014-04-01

    The Spallation Neutron Source at Oak Ridge National Laboratory now hosts four direct geometry time-of-flight chopper spectrometers. These instruments cover a range of wave-vector and energy transfer space with varying degrees of neutron flux and resolution. The regions of reciprocal and energy space available to measure at these instruments are not exclusive and overlap significantly. We present a direct comparison of the capabilities of this instrumentation, conducted by data mining the instrument usage histories, and specific scanning regimes. In addition, one of the common science missions for these instruments is the study of magnetic excitations in condensed matter systems. We have measured the powder averaged spin wave spectra in one particular sample using each of these instruments, and use these data in our comparisons. PMID:24784665

  17. 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.

  18. THE COMMISSIONING PLAN FOR THE SPALLATION NEUTRON SOURCE RING AND TRANSPORT LINES.

    SciTech Connect

    RAPARIA,D.BLASKIEWICZ,M.LEE,Y.Y.WEI,J.ET AL.

    2004-03-10

    The Spallation Neutron Source (SNS) accelerator systems will provide a 1 GeV, 1.44 MW proton beam to a liquid mercury target for neutron production. In order to satisfy the accelerator systems' portion of the Critical Decision 4 (CD-4) commissioning goal (which marks the completion of the construction phase of the project), a beam pulse with intensity greater than 1 x 10{sup 13} protons must be accumulated in the ring, extracted in a single turn and delivered to the target. A commissioning plan has been formulated for bringing into operation and establishing nominal operating conditions for the various ring and transport line subsystems as well as for establishing beam conditions and parameters which meet the commissioning goal.

  19. Integrating advanced materials simulation techniques into an automated data analysis workflow at the Spallation Neutron Source

    SciTech Connect

    Borreguero Calvo, Jose M; Campbell, Stuart I; Delaire, Olivier A; Doucet, Mathieu; Goswami, Monojoy; Hagen, Mark E; Lynch, Vickie E; Proffen, Thomas E; Ren, Shelly; Savici, Andrei T; Sumpter, Bobby G

    2014-01-01

    This presentation will review developments on the integration of advanced modeling and simulation techniques into the analysis step of experimental data obtained at the Spallation Neutron Source. A workflow framework for the purpose of refining molecular mechanics force-fields against quasi-elastic neutron scattering data is presented. The workflow combines software components to submit model simulations to remote high performance computers, a message broker interface for communications between the optimizer engine and the simulation production step, and tools to convolve the simulated data with the experimental resolution. A test application shows the correction to a popular fixed-charge water model in order to account polarization effects due to the presence of solvated ions. Future enhancements to the refinement workflow are discussed. This work is funded through the DOE Center for Accelerating Materials Modeling.

  20. A comparison of four direct geometry time-of-flight spectrometers at the Spallation Neutron Source

    SciTech Connect

    Stone, Matthew B; Niedziela, Jennifer L; Abernathy, Douglas L; Debeer-Schmitt, Lisa M; Garlea, Vasile O; Granroth, Garrett E; Graves-Brook, Melissa K; Ehlers, Georg; Kolesnikov, Alexander I; Podlesnyak, Andrey A; Winn, Barry L

    2014-04-01

    The Spallation Neutron Source at Oak Ridge National Laboratory now hosts four direct geometry time-of-flight chopper spectrometers. These instruments cover a range of wave vector and energy transfer space with varying degrees of neutron flux and resolution. The regions of reciprocal and energy space available to measure at these instruments is not exclusive and overlaps significantly. We present a direct comparison of the capabilities of this instrumentation, conducted by data mining the instrument usage histories, and specific scanning regimes. In addition, one of the common science missions for these instruments is the study of magnetic excitations in condensed matter systems. We have measured the powder averaged spin wave spectra in one particular sample using each of these instruments, and use these data in our comparisons.

  1. A comparison of four direct geometry time-of-flight spectrometers at the Spallation Neutron Source

    SciTech Connect

    Stone, M. B.; Abernathy, D. L.; Ehlers, G.; Garlea, O.; Podlesnyak, A.; Winn, B.; Niedziela, J. L.; DeBeer-Schmitt, L.; Graves-Brook, M.; Granroth, G. E.; Kolesnikov, A. I.

    2014-04-15

    The Spallation Neutron Source at Oak Ridge National Laboratory now hosts four direct geometry time-of-flight chopper spectrometers. These instruments cover a range of wave-vector and energy transfer space with varying degrees of neutron flux and resolution. The regions of reciprocal and energy space available to measure at these instruments are not exclusive and overlap significantly. We present a direct comparison of the capabilities of this instrumentation, conducted by data mining the instrument usage histories, and specific scanning regimes. In addition, one of the common science missions for these instruments is the study of magnetic excitations in condensed matter systems. We have measured the powder averaged spin wave spectra in one particular sample using each of these instruments, and use these data in our comparisons.

  2. A long-wavelength target station for the spallation neutron source

    NASA Astrophysics Data System (ADS)

    Carpenter, J. M.; Mason, T. E.

    2005-06-01

    The Spallation Neutron Source (SNS), a major new user facility for studies of the structure and dynamics of materials, funded by the US Department of Energy (DOE), is under construction at Oak Ridge National Laboratory (ORNL). Details about the project are available in a recent paper and on the SNS Web site [MRS Bull. 28 (12) (2003) 923]. A Long-Wavelength Target Station (LWTS) [Technical Concepts for a Long-Wavelength Target Station for the Spallation Neutron Source, Argonne National Laboratory Report ANL-02/16, Oak Ridge National Laboratory Report ORNL/SNS-TM-2001/163, November 2002. See also www.pns.anl.gov/related/] will complement the High-Power Target Station (HPTS) facility of the SNS and will build upon the significant investment in the remainder of the installation by providing important new scientific opportunities. For areas of science using the optimized long-wavelength beam lines, the LWTS will at least double the overall scientific capability of the SNS and provide for up to an order of magnitude performance gain over the initial HPTS. The fully equipped SNS has the prospect to offer capabilities for neutron-scattering studies of the structure and dynamics of materials with sensitivity, resolution, dynamic range, and speed that are unparalleled in the world. Preliminary assessments of the performance of the several instruments treated in detail in the body of the paper bear out this expectation. The LWTS concept has been developed in close consultation with the scientific community through a series of workshops and conferences jointly sponsored by DOE's Office of Basic Energy Science and the National Science Foundation. We describe the principal features of the LWTS concept, and provide a preliminary summary of some neutron scattering instruments suited to exploit the unique features of the LWTS. It remains to develop concepts and designs for a full suite of instruments that exploit the capabilities of LWTS, a process that has begun in collaboration

  3. Spallation Neutrons and Pressure SNAP DE-FG02-03ER46085 CLOSE-OUT MAY 2009

    SciTech Connect

    Parise, John B

    2009-05-22

    The purpose of the grant was to build a community of scientist and to draw upon their expertise to design and build the world's first dedicated high pressure beamline at a spallation source - the so called Spallation Neutron And Pressure (SNAP) beamline at the Spallation Neutron Source (SNS) at OAk Ridge NAtional LAboratory. . Key to this endeavor was an annual meeting attended by the instrument design team and the executive committee. The discussions at those meeting set an ambitious agenda for beamline design and construction and highlighted key science areas of interest for the community. This report documents in 4 appendices the deliberations at the annual SNAP meetings and the evolution of the beamline optics from concept to construction. The appendices also contain key science opportunities for extreme conditions research.

  4. Advantages and limitations of nuclear physics experiments at an ISIS-class spallation neutron source

    NASA Astrophysics Data System (ADS)

    Mocko, M.; Muhrer, G.; Tovesson, F.

    2008-05-01

    Nuclear physics experiments have a long history of being conducted on spallation neutron sources. Like other experiments, these measurements take advantage of the identification of the incident neutron energy by the time-of-flight (ToF) technique. However, in some ways these experiments are often in direct conflict with other experiments. Especially in large (ISIS or SNS class) facilities, the design of the source often reflects a compromise between different experimental needs and requirements. It has been a long standing question for nuclear physics experiments how limiting these compromises are and how they can be dealt with. We have therefore calculated the incident neutron energy spectrum, along with the gamma background spectrum, for flight path (FP) 5 at the Los Alamos Neutron Science Center (LANSCE) Manuel Lujan Jr. Neutron Scattering Center (Lujan Center) including a detailed evaluation of the signal shape. We will discuss the advantages and limitations of the nuclear physics experiments at FP-5 in the light of our results.

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

    SciTech Connect

    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 MW 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.

  6. Neutron-induced reaction studies at FIGARO using a spallation source

    NASA Astrophysics Data System (ADS)

    Rochman, D.; Haight, R. C.; O'Donnell, J. M.; Devlin, M.; Ethvignot, T.; Granier, T.

    2004-05-01

    A description is given of the new flexible facility Fast Neutron-Induced Gamma-Ray Observer (FIGARO) at the Los Alamos Neutron Science Center. FIGARO is designed to study fast-neutron-induced reactions that result in the emission of γ rays and neutrons, using the white neutron beam of the Weapons Neutron Research Facility. The emitted neutrons and γ rays are detected by several liquid scintillators and one high-resolution germanium or one barium-fluoride detector, respectively. As an example, the inelastic neutron scattering on Si from 4 to 20 MeV is presented and the results are compared with predictions of the nuclear model calculations performed with the codes GNASH and EMPIRE II.

  7. 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.

  8. Neutron emission prior to fission

    SciTech Connect

    Gavron, A.; Gayer, A.; Boissevain, J.; Britt, H.C.; Nix, J.R.; Sierk, A.J.; Grange, P.; Hassani, S.; Weidenmueller, H.A.; Beene, J.R.

    1986-01-01

    Neutron emission in the /sup 158/Er composite system is studied in order to investigate particle emission with energy spectrum and angular distribution in excess of statistical model predictions. Data are analyzed using a modified statistical model which incorporates effects due to nuclear dissipation, and also calculates neutron emission during the descent from the saddle to the scission point. Calculations consider the Kramers effect and the Transient effect. It is concluded that a detailed interpretation of enhanced neutron emission preceding fission in compound nucleus reactions is possible, and that an upper limit may be set on the reduced nuclear dissipation coefficient. 5 refs., 2 figs. (LEW)

  9. Proceedings of the workshop on ion source issues relevant to a pulsed spallation neutron source: Part 2 workshop presentations

    SciTech Connect

    Schroeder, L.; Leung, Ka-Ngo; Alonso, J.

    1994-10-01

    As part of the Lawrence Berkeley Laboratory Pulsed Spallation Source study, this Workshop was convened to address ion-source technology`s present status with respect to the next-generation Pulsed Spallation Source in the 1-5 MW range for the neutron scattering community. Considerations of Low Energy Beam Transport (LEBT) parameters and designs were included in the discussions throughout the Workshop. Ion-source requirements and actually-achieved performances were assessed, resulting in a determination of research and development requirements to bridge the gap. Part 1 of these Proceedings summarizes the Workshop; Part 2 contains viewgraphs of Workshop presentations.

  10. Particle optics of quadrupole doublet magnets in Spallation Neutron Source accumulator ring

    NASA Astrophysics Data System (ADS)

    Wang, J. G.

    2006-12-01

    The Spallation Neutron Source ring employs doublet quadrupoles and dipole correctors in its straight sections. The electromagnetic quadrupoles have a large aperture, small aspect ratio, and relatively short iron-to-iron distance. The corrector is even closer to one of the quads. There have been concerns on the magnetic fringe field and interference in the doublet magnets and their assemblies. We have performed 3D computing simulations to study magnetic field distributions in the doublet magnets. Further, we have analyzed the particle optics based on the z-dependent focusing functions of the quads. The effect of the magnetic fringe field and interference, including the third-order aberrations, on the particle motion are investigated. The lens parameters and the first-order hard edge models are derived and compared with the parameters used in the ring lattice calculations.

  11. Evidence of a halo formation mechanism in the Spallation Neutron Source linac

    NASA Astrophysics Data System (ADS)

    Jeon, Dong-O.

    2013-04-01

    A new halo formation mechanism and its mitigation scheme [D. Jeon, J. Stovall, A. Aleksandrov, J. Wei, J. Staples, R. Keller, L. Young, H. Takeda, and S. Nath, Phys. Rev. ST Accel. Beams 5, 094201 (2002)PRABFM1098-440210.1103/PhysRevSTAB.5.094201] are verified experimentally through a series of emittance measurements performed during the drift tube linac tank 1 commissioning of the Spallation Neutron Source. This is a rare experiment evidence of a halo formation mechanism. As the simulation predicts, the emittance measurements clearly show a visible halo reduction as well as a significant rms emittance reduction when the proposed round beam optics is employed. The emittance measurement results are consistent with multiparticle simulations and also consistent with wire scanner results. These measurements serve as a valuable code benchmarking for a beam under an intense space charge effect.

  12. Computer simulations for rf design of a Spallation Neutron Source external antenna H ion source

    SciTech Connect

    Lee, Sung-Woo; Goulding, Richard Howell; Kang, Yoon W; Shin, Ki; Welton, Robert F

    2010-01-01

    Electromagnetic modeling of the multicusp external antenna H ion source for the Spallation Neutron Source SNS has been performed in order to optimize high-power performance. During development of the SNS external antenna ion source, antenna failures due to high voltage and multicusp magnet holder rf heating concerns under stressful operating conditions led to rf characteristics analysis. In rf simulations, the plasma was modeled as an equivalent lossy metal by defining conductivity as . Insulation designs along with material selections such as ferrite and Teflon could be included in the computer simulations to compare antenna gap potentials, surface power dissipations, and input impedance at the operating frequencies, 2 and 13.56 MHz. Further modeling and design improvements are outlined in the conclusion.

  13. EXPERIENCE WITH COLLABORATIVE DEVELOPMENT FOR THE SPALLATION NEUTRON SOURCE FROM A PARTNER LAB PERSPECTIVE.

    SciTech Connect

    HOFF, L.T.

    2005-10-10

    Collaborative development and operation of large physics experiments is fairly common. Less common is the collaborative development or operation of accelerators. A current example of the latter is the Spallation Neutron Source (SNS). The SNS project was conceived as a collaborative effort between six DOE facilities. In the SNS case, the control system was also developed collaboratively. The SNS project has now moved beyond the collaborative development phase and into the phase where Oak Ridge National Lab (ORNL) is integrating contributions from collaborating ''partner labs'' and is beginning accelerator operations. In this paper, the author reflects on the benefits and drawbacks of the collaborative development of an accelerator control system as implemented for the SNS project from the perspective of a partner lab.

  14. Dynamics of uncaught foil-stripped electrons in the Oak Ridge Spallation Neutron Source accumulator ring

    NASA Astrophysics Data System (ADS)

    Cousineau, S.; Holmes, J. A.; Plum, M. A.; Lu, W.

    2011-06-01

    The Spallation Neutron Source accelerator utilizes H- charge exchange injection to merge a 1 GeV, 1 MW beam from a linac into an accumulator ring. The design calls for the 545 keV foil-stripped electrons to be absorbed by an electron catcher located below the foil. However, multiple observations of hardware damage caused by stripped electrons indicate that at least a fraction of the electrons are reflected back into the vacuum chamber. This paper presents the results of a 3D computational model employed to simulate the dynamics of foil-stripped electrons, including a surface interaction model for the catcher. Simulation results are compared with experimental observations, and the implications for high power beam operations are discussed.

  15. Development of a fast traveling-wave beam chopper for the National Spallation Neutron Source

    SciTech Connect

    Kurennoy, S.S.; Jason, A.J.; Krawczyk, F.L.; Power, J.

    1997-10-01

    High current and severe restrictions on beam losses, below 1 nA/m, in the designed linac for the National Spallation Neutron Source (NSNS) require clean and fast--with the rise time from 2% to 98% less than 2.5 ns to accommodate a 402.5-MHz beam structure--beam chopping in its front end, at the beam energy 2.5 MeV. The R and D program includes both modification of the existing LANSCE coax-plate chopper to reduce parasitic coupling between adjacent plates, and development of new traveling-wave deflecting structures, in particular, based on a meander line. Using analytical methods and three-dimensional time-domain computer simulations the authors study transient effects in such structures to choose an optimal chopper design.

  16. Development of the activation analysis calculational methodology for the Spallation Neutron Source (SNS)

    SciTech Connect

    Odano, N.; Johnson, J.O.; Charton, L.A.; Barnes, J.M.

    1998-03-01

    For the design of the proposed Spallation Neutron Source (SNS), activation analyses are required to determine the radioactive waste streams, on-line material processing requirements remote handling/maintenance requirements, potential site contamination and background radiation levels. For the conceptual design of the SNS, the activation analyses were carried out using the high-energy transport code HETC96 coupled with MCNP to generate the required nuclide production rates for the ORIHET95 isotope generation code. ORIHET95 utilizes a matrix-exponential method to study the buildup and decay of activities for any system for which the nuclide production rates are known. In this paper, details of the developed methodology adopted for the activation analyses in the conceptual design of the SNS are presented along with some typical results of the analyses.

  17. Low-energy beam transport studies supporting the spallation neutron source 1-MW beam operation

    SciTech Connect

    Han, B. X.; Welton, R. F.; Murray, S. N. Jr.; Pennisi, T. R.; Santana, M.; Stockli, M. P.; Kalvas, T.; Tarvainen, O.

    2012-02-15

    The H{sup -} injector consisting of a cesium enhanced RF-driven ion source and a 2-lens electrostatic low-energy beam transport (LEBT) system supports the spallation neutron source 1 MW beam operation with {approx}38 mA beam current in the linac at 60 Hz with a pulse length of up to {approx}1.0 ms. In this work, two important issues associated with the low-energy beam transport are discussed: (1) inconsistent dependence of the post-radio frequency quadrupole accelerator beam current on the ion source tilt angle and (2) high power beam losses on the LEBT electrodes under some off-nominal conditions compromising their reliability.

  18. Low-energy beam transport studies supporting the spallation neutron source 1-MW beam operation

    SciTech Connect

    Kalvas, T.; Welton, Robert F; Pennisi, Terry R

    2012-01-01

    The H{sup -} injector consisting of a cesium enhanced RF-driven ion source and a 2-lens electrostatic low-energy beam transport (LEBT) system supports the spallation neutron source 1 MW beam operation with {approx}38 mA beam current in the linac at 60 Hz with a pulse length of up to {approx}1.0 ms. In this work, two important issues associated with the low-energy beam transport are discussed: (1) inconsistent dependence of the post-radio frequency quadrupole accelerator beam current on the ion source tilt angle and (2) high power beam losses on the LEBT electrodes under some off-nominal conditions compromising their reliability.

  19. Spallation Neutron Source Availability Top-Down Apportionment Using Characteristic Factors and Expert Opinion

    SciTech Connect

    Haire, M.J.; Schryver, J.C.

    1999-10-01

    Apportionment is the assignment of top-level requirements to lower tier elements of the overall facility. A method for apportioning overall facility availability requirements among systems and subsystems is presented. Characteristics that influence equipment reliability and maintainability are discussed. Experts, using engineering judgment, scored each characteristic for each system whose availability design goal is to be established. The Analytic Hierarchy Process (AHP) method is used to produce a set of weighted rankings for each characteristic for each alternative system. A mathematical model is derived which incorporates these weighting factors. The method imposes higher availability requirements on those systems in which an incremental increase in availability is easier to achieve, and lower availability requirements where greater availability is more difficult and costly. An example is given of applying this top-down apportionment methodology to the Spallation Neutron Source (SNS) facility.

  20. ACCELERATOR SYSTEMS MODIFICATIONS FOR A SECOND TARGET STATION AT THE OAK RIDGE SPALLATION NEUTRON SOURCE

    SciTech Connect

    Galambos, John D; Kim, Sang-Ho; Plum, Michael A

    2014-01-01

    A second target station is planned for the Oak Ridge Spallation Neutron Source. The ion source will be upgraded to increase the peak current from 38 to 49 mA, additional superconducting RF cavities will be added to the linac to increase the H beam energy from 938 to 1300 MeV, and the accumulator ring will receive modifications to the injection and extraction systems to accommodate the higher beam energy. After pulse compression in the storage ring one sixth of the beam pulses (10 out of 60 Hz) will be diverted to the second target by kicker and septum magnets added to the existing Ring to Target Beam Transport (RTBT) line. No further modifications will be made to the RTBT so that when the kicker and septum magnets are turned off the original beam transport lattice will be unaffected. In this paper we will discuss these and other planned modifications and upgrades to the accelerator facility.

  1. Design of an Aluminum Proton Beam Window for the Spallation Neutron Source

    SciTech Connect

    Janney, Jim G; McClintock, David A

    2012-01-01

    An aluminum proton beam window design is being considered at the Spallation Neutron Source primarily to increase the lifetime of the window, with secondary advantages of higher beam transport efficiency and lower activation. The window separates the core vessel, the location of the mercury target, from the vacuum of the accelerator, while withstanding the pass through of a proton beam of up to 2 MW with 1.0 GeV proton energy. The current aluminum alloy being investigated for the window material is 6061-T651 due to its combination of high strength, high thermal conductivity, and good resistance to aqueous corrosion, as well as demonstrated dependability in previous high-radiation environments. The window design will feature a thin plate with closely spaced cross drilled cooling holes. An analytical approach was used to optimize the dimensions of the window before finite element analysis was used to simulate temperature profiles and stress fields resulting from thermal and static pressure loading. The resulting maximum temperature of 60 C and Von Mises stress of 71 MPa are very low compared to allowables for Al 6061-T651. A significant challenge in designing an aluminum proton beam window for SNS is integrating the window with the current 316L SS shield blocks. Explosion bonding was chosen as a joining technique because of the large bonding area required. A test program has commenced to prove explosion bonding can produce a robust vacuum joint. Pending successful explosion bond testing, the aluminum proton beam window design will be proven acceptable for service in the Spallation Neutron Source.

  2. Department of Energy review of the National Spallation Neutron Source Project

    SciTech Connect

    1997-06-01

    A Department of Energy (DOE) review of the Conceptual Design Report (CDR) for the National Spallation Neutron Source (NSNS) was conducted. The NSNS will be a new high-power spallation neutron source; initially, it will operate at 1 megawatt (MW), but is designed to be upgradeable to significantly higher power, at lower cost, when accelerator and target technologies are developed for higher power. The 53-member Review Committee examined the projected cost, schedule, technical scope, and management structure described in the CDR. For each of the major components of the NSNS, the Committee determined that the project team had produced credible designs that can be expected to work well. What remains to be done is to integrate the design of these components. With the exception of the liquid mercury target, the NSNS Project will rely heavily on proven technologies and, thus, will face a relatively low risk to successful project completion. The Total Project Cost (TPC) presented to the Committee in the CDR was $1.266 billion in as-spent dollars. In general, the Committee felt that the laboratory consortium had presented a credible estimate for each of the major components but that value engineering might produce some savings. The construction schedule presented to the Committee covered six years beginning in FY 1999. The Committee questioned whether all parts of the project could be completed according to this schedule. In particular, the linac and the conventional facilities appeared to have overly optimistic schedules. The NSNS project team was encouraged to reexamine these activities and to consider a more conservative seven-year schedule. Another concern of the Committee was the management structure. In summary, the Committee felt that this Conceptual Design Report was a very credible proposal, and that there is a high probability for successful completion of this major project within the proposed budget, although the six-year proposed schedule may be optimistic.

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

    DOE PAGESBeta

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; et al

    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 Zr64Ni36 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

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

    SciTech Connect

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; Wang, Xun-Li; Goldman, A. I.; Egami, T.; Kelton, K. F.

    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 elastic 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 Zr64Ni36 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).

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

    NASA Astrophysics Data System (ADS)

    Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; Johnson, M. L.; Rustan, G. E.; Quirinale, D. G.; Kreyssig, A.; Lokshin, K. A.; Neuefeind, J. C.; An, Ke; Wang, Xun-Li; Goldman, A. I.; Egami, T.; Kelton, K. F.

    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. 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 elastic 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 Zr64Ni36 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).

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

    PubMed

    Mauro, N A; Vogt, A J; Derendorf, K S; Johnson, M L; Rustan, G E; Quirinale, D G; Kreyssig, A; Lokshin, K A; Neuefeind, J C; An, Ke; Wang, Xun-Li; Goldman, A I; Egami, T; Kelton, K F

    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. 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 elastic 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 Zr64Ni36 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). PMID:26827330

  7. The Neutron Science TeraGrid Gateway, a TeraGrid Science Gateway to Support the Spallation Neutron Source

    SciTech Connect

    Cobb, John W; Geist, Al; Kohl, James Arthur; Miller, Stephen D; Peterson, Peter F; Pike, Gregory; Reuter, Michael A; Swain, William; Vazhkudai, Sudharshan S; Vijayakumar, Nithya N

    2006-01-01

    The National Science Foundation's (NSF's) Extensible Terascale Facility (ETF), or TeraGrid [1] is entering its operational phase. An ETF science gateway effort is the Neutron Science TeraGrid Gateway (NSTG.) The Oak Ridge National Laboratory (ORNL) resource provider effort (ORNL-RP) during construction and now in operations is bridging a large scale experimental community and the TeraGrid as a large-scale national cyberinfrastructure. Of particular emphasis is collaboration with the Spallation Neutron Source (SNS) at ORNL. The U.S. Department of Energy's (DOE's) SNS [2] at ORNL will be commissioned in spring of 2006 as the world's brightest source of neutrons. Neutron science users can run experiments, generate datasets, perform data reduction, analysis, visualize results; collaborate with remotes users; and archive long term data in repositories with curation services. The ORNL-RP and the SNS data analysis group have spent 18 months developing and exploring user requirements, including the creation of prototypical services such as facility portal, data, and application execution services. We describe results from these efforts and discuss implications for science gateway creation. Finally, we show incorporation into implementation planning for the NSTG and SNS architectures. The plan is for a primarily portal-based user interaction supported by a service oriented architecture for functional implementation.

  8. The continued development of the Spallation Neutron Source external antenna H{sup -} ion source

    SciTech Connect

    Welton, R. F.; Carmichael, 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.; Desai, N. J.

    2010-02-15

    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{sup -} 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 {approx}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 {approx}35 mA (beam current required by the ramp up plan) with availability of {approx}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.

  9. Laser wire beam profile monitor in the spallation neutron source (SNS) superconducting linac

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Aleksandrov, A.; Assadi, S.; Blokland, W.; Deibele, C.; Grice, W.; Long, C.; Pelaia, T.; Webster, A.

    2010-01-01

    The spallation neutron source (SNS) at Oak Ridge National Laboratory is an accelerator-based, neutron-scattering facility. SNS uses a large-scale, high-energy superconducting linac (SCL) to provide high beam power utilizing hydrogen ion (H -) beams. For the diagnostics of high-brightness H - beams in the SCL, nonintrusive methods are preferred. This paper describes design, implementation, theoretical analysis, and experimental demonstration of a nonintrusive profile monitor system based on photodetachment, also known as laser wire, installed in the SNS SCL. The SNS laser wire system is the world's largest of its kind with a capability of measuring horizontal and vertical profiles of an operational H - beam at each of the 23 cryomodule stations along the SCL beam line by employing a single light source. Presently 9 laser wire stations have been commissioned that measure profiles of the H - beam at energy levels from 200 MeV to 1 GeV. The laser wire diagnostics has no moving parts inside the beam pipe, causes no contamination on the superconducting cavity, and can be run parasitically on an operational neutron production H - beam.

  10. Accelerating Data Acquisition, Reduction, and Analysis at the Spallation Neutron Source

    SciTech Connect

    Campbell, Stuart I; Kohl, James Arthur; Granroth, Garrett E; Miller, Ross G; Doucet, Mathieu; Stansberry, Dale V; Proffen, Thomas E; Taylor, Russell J; Dillow, David

    2014-01-01

    ORNL operates the world's brightest neutron source, the Spallation Neutron Source (SNS). Funded by the US DOE Office of Basic Energy Science, this national user facility hosts hundreds of scientists from around the world, providing a platform to enable break-through research in materials science, sustainable energy, and basic science. While the SNS provides scientists with advanced experimental instruments, the deluge of data generated from these instruments represents both a big data challenge and a big data opportunity. For example, instruments at the SNS can now generate multiple millions of neutron events per second providing unprecedented experiment fidelity but leaving the user with a dataset that cannot be processed and analyzed in a timely fashion using legacy techniques. To address this big data challenge, ORNL has developed a near real-time streaming data reduction and analysis infrastructure. The Accelerating Data Acquisition, Reduction, and Analysis (ADARA) system provides a live streaming data infrastructure based on a high-performance publish subscribe system, in situ data reduction, visualization, and analysis tools, and integration with a high-performance computing and data storage infrastructure. ADARA allows users of the SNS instruments to analyze their experiment as it is run and make changes to the experiment in real-time and visualize the results of these changes. In this paper we describe ADARA, provide a high-level architectural overview of the system, and present a set of use-cases and real-world demonstrations of the technology.

  11. Design progress of cryogenic hydrogen system for China Spallation Neutron Source

    SciTech Connect

    Wang, G. P.; Zhang, Y.; Xiao, J.; He, C. C.; Ding, M. Y.; Wang, Y. Q.; Li, N.; He, K.

    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 load 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.

  12. Design progress of cryogenic hydrogen system for China Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Wang, G. P.; Zhang, Y.; Xiao, J.; He, C. C.; Ding, M. Y.; Wang, Y. Q.; Li, N.; He, K.

    2014-01-01

    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 load 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.

  13. Awareness, Preference, Utilization, and Messaging Research for the Spallation Neutron Source and High Flux Isotope Reactor

    SciTech Connect

    Bryant, Rebecca; Kszos, Lynn A

    2011-03-01

    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 pulsed neutron beams. Management of these two resources is the responsibility of the Neutron Sciences Directorate (NScD). NScD commissioned this survey research to develop baseline information regarding awareness of and perceptions about neutron science. Specific areas of investigative interest include the following: (1) awareness levels among those in the scientific community about the two neutron sources that ORNL offers; (2) the level of understanding members of various scientific communities have regarding benefits that neutron scattering techniques offer; and (3) any perceptions that negatively impact utilization of the facilities. NScD leadership identified users of two light sources in North America - the Advanced Photon Source (APS) at Argonne National Laboratory and the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory - as key publics. Given the type of research in which these scientists engage, they would quite likely benefit from including the neutron techniques available at SNS and HFIR among their scientific investigation tools. The objective of the survey of users of APS, NSLS, SNS, and HFIR was to explore awareness of and perceptions regarding SNS and HFIR among those in selected scientific communities. Perceptions of SNS and FHIR will provide a foundation for strategic communication plan development and for developing key educational messages. The survey was conducted in two phases. The first phase included qualitative methods of (1) key stakeholder meetings; (2) online interviews with user administrators of APS and NSLS; and (3) one-on-one interviews

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

    PubMed

    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. PMID:27502571

  15. 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.

  16. 196Pt(n,xn yp γ) reactions using spallation neutrons from En=1 to 250 MeV

    NASA Astrophysics Data System (ADS)

    Tavukcu, E.; Bernstein, L. A.; Hauschild, K.; Becker, J. A.; Garrett, P. E.; McGrath, C. A.; McNabb, D. P.; Younes, W.; Chadwick, M. B.; Nelson, R. O.; Johns, G. D.; Mitchell, G. E.

    2001-11-01

    Neutron-induced reactions on 196Pt were studied over the neutron energy range from 1 to 250 MeV. A ``white'' neutron beam was provided by the spallation neutron source of the Weapons Neutron Research facility at the Los Alamos Neutron Science Center. The prompt reaction γ rays were measured with the large-scale Compton-suppressed Ge spectrometer GEANIE. The incident neutron energy was determined by the time-of-flight technique. Excitation functions for γ-ray transitions in 184,186,188,190-196Pt and 189,191,193Ir isotopes are compared with enhanced Hauser-Feshbach reaction modeling, as implemented in the reaction code GNASH. Overall, the model predictions agree well with the measured γ-ray yields. Discrepancies appear, however, due to inadequate discrete-level information in the calculations describing the preequilibrium process.

  17. The performance of neutron scattering spectrometers at a long-pulse spallation source

    SciTech Connect

    Pynn, R.

    1997-06-01

    In this document the author considers the performance of a long pulse spallation source for those neutron scattering experiments that are usually performed with a monochromatic beam at a continuous wave (CW) source such as a nuclear reactor. The first conclusion drawn is that comparison of the performance of neutron scattering spectrometers at CW and pulsed sources is simpler for long-pulsed sources than it is for the short-pulse variety. Even though detailed instrument design and assessment will require Monte Carlo simulations (which have already been performed at Los Alamos for SANS and reflectometry), simple arguments are sufficient to assess the approximate performance of spectrometers at an LPSS and to support the contention that a 1 MW long-pulse source can provide attractive performance, especially for instrumentation designed for soft-condensed-matter science. Because coupled moderators can be exploited at such a source, its time average cold flux is equivalent to that of a research reactor with a power of about 15 MW, so only a factor of 4 gain from source pulsing is necessary to obtain performance that is comparable with the ILL. In favorable cases, the gain from pulsing can be even more than this, approaching the limit set by the peak flux, giving about 4 times the performance of the ILL. Because of its low duty factor, an LPSS provides the greatest performance gains for relatively low resolution experiments with cold neutrons. It should thus be considered complementary to short pulse sources which are most effective for high resolution experiments using thermal or epithermal neutrons.

  18. 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.

  19. 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.

  20. Thermal-hydraulic analysis of the liquid mercury target for the national spallation neutron source

    SciTech Connect

    Siman-Tov, M.; Wendel, M.W.; Haines, J.R.; Rogers, M.

    1997-04-01

    The National Spallation Neutron Source (NSNS) is a high-energy, accelerator-based spallation neutron source being designed by a multi-laboratory team led by Oak Ridge National Laboratory (ORNL) to achieve very high fluxes of neutrons for scientific experiments. The NSNS is proposed to have a 1 MW beam of high-energy ({approximately}1 GeV) protons upgradable to 5 MW and operating at 60 Hz with a pulse duration of 0.5 {mu}s. Peak steady-state power density in the target is about 640 MW/m{sup 3} for 1 MW, whereas the pulse instantaneous peak power density is as high as 22,000 GW/m{sup 3}. The local peak temperature rise for a single pulse over it`s time-averaged value is only 6{degrees}C, but the rate of this temperature rise during the pulse is extremely fast ({approximately}12 million {degrees}C/s). In addition to the resulting thermal shock and materials compatibility concerns, key feasibility issues for the target are related to its thermal-hydraulic performance. These include proper flow distribution, flow reversals and stagnation zones, possible {open_quotes}hot spots{close_quotes}, cooling of the beam {open_quotes}window{close_quotes}, and the challenge of mitigating the effects of thermal shock through possible injection of helium bubbles. An analytic approach was used on the PC spreadsheet EXCEL to evaluate target design options and to determine the global T/H parameters in the current concept. The general computational fluid dynamics (CFD) code CFX was used to simulate the detailed time-averaged two-dimensional thermal and flow distributions in the liquid mercury. In this paper, an overview of the project and the results of this preliminary work are presented. Heat transfer characteristics of liquid mercury under wetting and non-wetting conditions are discussed, and future directions of the program in T/H analysis and R&D are outlined.

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

    SciTech Connect

    Haines, J.R.; DiStefano, J.; Farrell, K.; Gabriel, T.A.

    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 the 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.

  2. A 1- to 5-MW, RCS-based, short-pulse spallation neutron source

    SciTech Connect

    Cho, Y. Chae, Y.C.; Crosbie, E.

    1997-06-01

    Two accelerator configurations, the linac/compressor ring scheme and the linac/RCS scheme, are commonly used to provide the proton beam power for a short-pulse spallation neutron source. In one configuration, a full-power linac provides the beam power and a compressor ring shortens the pulse length from 1-ms down to 1 {micro}s. In the other, rapid cycling synchrotrons (RCSs) provide the beam power and also shorten the pulse length. A feasibility study of a staged approach to a 5-MW proton source utilizing RCS technology, allowing intermediate operation at 1 MW, was performed at ANL and is presented in this paper. This study is complementary to a study in progress at ORNL based on a linac and an accumulator ring. The 1-MW facility consists of a 400-MeV injector linac that delivers 0.5-mA time-averaged current, a synchrotron that accelerates the beam to 2 GeV at a 30-Hz rate, and two neutron-generating target stations. In the second phase, the 2-GeV beam is accelerated to 10 GeV by a larger RCS, increasing the facility beam power to 5 MW.

  3. Preequilibrium Emission of Light Fragments in Spallation Reactions

    NASA Astrophysics Data System (ADS)

    Kerby, L. M.; Mashnik, S. G.; Sierk, A. J.

    2014-04-01

    The ability to describe production of light fragments (LF) is important for many applications, such as cosmic-ray-induced single event upsets (SEUs), radiation protection, and cancer therapy with proton and heavy-ion beams. The cascade-exciton model (CEM) and the Los Alamos version of the quark-gluon string model (LAQGSM) event generators in the LANL transport code MCNP6, describe quite well the spectra of fragments with sizes up to 4He across a broad range of target masses and incident energies (up to ∼ 5 GeV for CEM and up to ∼ 1 TeV/A for LAQGSM). However, they do not predict the high-energy tails of LF spectra heavier than 4He well. Most LF with energies above several tens of MeV are emitted during the precompound stage of a reaction. The current versions of our event generators do not account for precompound emission of LF larger than 4He. The aim of our work is to generalize the precompound model to include such processes, leading to increased predictive power of LF production. Extending the model in this way provides preliminary results that have much better agreement with experimental data.

  4. Fundamental Problems of Neutron Physics at the Spallation Neutron Source at the ORNL

    SciTech Connect

    Vladimir Gudkov

    2008-07-16

    We propose to provide theoretical support for the experimental program in fundamental neutron physics at the SNS. This includes the study of neutron properties, neutron beta-decay, parity violation effects and time reversal violation effects. The main purpose of the proposed research is to work on theoretical problems related to experiments which have a high priority at the SNS. Therefore, we will make a complete analysis of beta-decay process including calculations of radiative corrections and recoil corrections for angular correlations for polarized neutron decay, with an accuracy better that is supposed to be achieved in the planning experiments. Based on the results of the calculations, we will provide analysis of sensitivity of angular correlations to be able to search for the possible extensions of the Standard model. Also we will help to plan other experiments to address significant problems of modern physics and will work on their theoretical support.

  5. Initial tests of the Spallation Neutron Source H{sup -} ion source with an external antenna

    SciTech Connect

    Welton, R.F.; Stockli, M.P.; Murray, S.N.; Kang, Y.; Peters, J.

    2006-03-15

    The ion source for the Spallation Neutron Source (SNS) is a radio-frequency (rf) multicusp source designed to deliver H{sup -} beam pulses of 40 mA to the SNS accelerator with a normalized root-mean-square emittance of less than 0.2{pi} mm mrad, with a pulse length of 1 ms and a repetition rate of 60 Hz. In order to achieve this performance the source must operate with both high-pulse rf power, {approx}50 kW, and high average rf power, {approx}3.5 kW, over a continuous operational period of 3 weeks. During operation at these power levels the plasma-immersed, porcelain-coated rf antenna is susceptible to damage, limiting source lifetime. We are therefore developing an ion source where the plasma is separated from the Cu antenna by an Al{sub 2}O{sub 3} discharge chamber. This article describes the ion source, presents initial beam extraction measurements, and details our ongoing effort to develop this concept into a suitable ion source for the SNS.

  6. Characterization of an explosively bonded aluminum proton beam window for the Spallation Neutron Source

    SciTech Connect

    McClintock, David A; Janney, Jim G; Parish, Chad M

    2014-01-01

    An effort is underway at the Spallation Neutron Source (SNS) to change the design of the 1st Generation high-nickel alloy proton beam window (PBW) to one that utilizes aluminum for the window material. One of the key challenges to implementation of an aluminum PBW at the SNS was selection of an appropriate joining method to bond an aluminum window to the stainless steel bulk shielding of the PBW assembly. An explosively formed bond was selected as the most promising joining method for the aluminum PBW design. A testing campaign was conducted to evaluate the strength and efficacy of explosively formed bonds that were produced using two different interlayer materials: niobium and titanium. The characterization methods reported here include tensile testing, thermal-shock leak testing, optical microscopy, and advanced scanning electron microscopy. All tensile specimens examined failed in the aluminum interlayer and measured tensile strengths were all slightly greater than the native properties of the aluminum interlayer, while elongation values were all slightly lower. A leak developed in the test vessel with a niobium interlayer joint after repeated thermal-shock cycles, and was attributed to an extensive crack network that formed in a layer of niobium-rich intermetallics located on the bond interfaces of the niobium interlayer; the test vessel with a titanium interlayer did not develop a leak under the conditions tested. Due to the experience gained from these characterizations, the explosively formed bond with a titanium interlayer was selected for the aluminum PBW design at the SNS.

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

    SciTech Connect

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

    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 procedure 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.

  8. A Large Neutrino Detector Facility at the Spallation Neutron Source at Oak Ridge National Laboratory

    SciTech Connect

    Efremenko, Y.V.

    1999-02-14

    The ORLaND (Oak Ridge Large Neutrino Detector) collaboration proposes to construct a large neutrino detector in an underground experimental hall adjacent to the first target station of the Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory. The main mission of a large (2000 ton) Scintillation-Cherenkov detector is to measure {bar {nu}}{sub {mu}} {r_arrow} {bar {nu}}{sub e} neutrino oscillation parameters more accurately than they can be determined in other experiments, or significantly extending the covered parameter space below (sin'20 {le} 10{sup {minus}4}). In addition to the neutrino oscillation measurements, ORLaND would be capable of making precise measurements of sin{sup 2} {theta}{sub W}, search for the magnetic moment of the muon neutrino, and investigate the anomaly in the KARMEN time spectrum, which has been attributed to a new neutral particle. With the same facility an extensive program of measurements of neutrino nucleus cross sections is also planned to support nuclear astrophysics.

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

    SciTech Connect

    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 avoiding 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.

  10. Potential containment materials for liquid-lead and lead-bismuth eutectic spallation neutron source

    SciTech Connect

    Park, J.J.; Butt, D.P.; Beard, C.A.

    1997-11-01

    Lead (Pb) and lead-bismuth eutectic (44Pb-56Bi) have been the two primary candidate liquid-metal target materials for the production of spallation neutrons. Selection of a container material for the liquid-metal target will greatly affect the lifetime and safety of the target subsystem. For the lead target, niobium-1 (wt%) zirconium (Nb-1Zr) is a candidate containment material for liquid lead, but its poor oxidation resistance has been a major concern. The oxidation rate of Nb-1Zr was studied based on the calculations of thickness loss due to oxidation. According to these calculations, it appeared that uncoated Nb-1Zr may be used for a one-year operation at 900 C at P{sub O{sub 2}} = 1 {times} 10{sup {minus}6} torr, but the same material may not be used in argon with 5-ppm oxygen. Coating technologies to reduce the oxidation of Nb-1Zr are reviewed, as are other candidate refractory metals such as molybdenum, tantalum, and tungsten. For the Pb-Bi target, three candidate containment materials are suggested based on a literature survey of the materials compatibility and proton irradiation tests: Croloy 2-1/4, modified 9Cr-1Mo, and 12Cr-1Mo (HT-9) steel. These materials seem to be used only if the lead-bismuth is thoroughly deoxidized and treated with zirconium and magnesium.

  11. RISE/FALL TIME ENHANCEMENT OF THE SPALLATION NEUTRON SOURCE LINAC LEBT CHOPPER SYSTEM

    SciTech Connect

    Peplov, Vladimir V; Saethre, Robert B

    2013-01-01

    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 these 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.

  12. Separation of beam and electrons in the spallation neutron source H{sup -} ion source

    SciTech Connect

    Whealton, J.H.; Raridon, R.J.; Leung, K.N.

    1997-12-01

    The Spallation Neutron Source (SNS) requires an ion source producing an H{sup {minus}} beam with a peak current of 35mA at a 6.2 percent duty factor. For the design of this ion source, extracted electrons must be transported and dumped without adversely affecting the H{sup {minus}} beam optics. Two issues are considered: (1) electron containment transport and controlled removal; and (2) first-order H{sup {minus}} beam steering. For electron containment, various magnetic, geometric and electrode biasing configurations are analyzed. A kinetic description for the negative ions and electrons is employed with self-consistent fields obtained from a steady-state solution to Poisson`s equation. Guiding center electron trajectories are used when the gyroradius is sufficiently small. The magnetic fields used to control the transport of the electrons and the asymmetric sheath produced by the gyrating electrons steer the ion beam. Scenarios for correcting this steering by split acceleration and focusing electrodes will be considered in some detail.

  13. rf improvements for Spallation Neutron Source H{sup -} ion source

    SciTech Connect

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

    2010-02-15

    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 {approx}38 mA H{sup -} 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.

  14. Control system for the Spallation Neutron Source H{sup -} source test facility Allison scanner

    SciTech Connect

    Long, C. D.; Stockli, M. P.; Gorlov, T. V.; Han, B.; Murray, S. N.; Pennisi, T. R.

    2010-02-15

    Spallation Neutron Source is currently in progress of a multiyear plan to ramp ion beam power to the initial design power of 1.4 MW. Key to reaching this goal is understanding and improving the operation of the H{sup -} ion source. An Allison scanner was installed on the ion source in the test facility to support this improvement. This paper will discuss the hardware and the software control system of the installed Allison scanner. The hardware for the system consists of several parts. The heart of the system is the scanner head, complete with associated bias plates, slits, and signal detector. There are two analog controlled high voltage power supplies to bias the plates in the head, and a motor with associated controller to position the head in the beam. A multifunction data acquisition card reads the signals from the signal detector, as well as supplies the analog voltage control for the power supplies. To synchronize data acquisition with the source, the same timing signal that is used to trigger the source itself is used to trigger data acquisition. Finally, there is an industrial personal computer to control the rest of the hardware. Control software was developed using National Instruments LABVIEW, and consists of two parts: a data acquisition program to control the hardware and a stand alone application for offline user data analysis.

  15. Lorentz force detuning analysis of the Spallation Neutron Source (SNS) accelerating cavities.

    SciTech Connect

    Mitchell, R.R.; Matsumoto, K. Y.; Ciovati, G.; Davis, K.; Macha, K.; Sundelin, R. M.

    2001-01-01

    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 Lorentz force detuning. In addition, the pulsed RF induces cyclic Lorentz pressures that mechanically excite the cavities, producing 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.

  16. High-power linac for a US spallation-neutron source

    SciTech Connect

    Wangler, T.P.; Billen, J.; Jason, A. Krawczyk, F.; Nath, S.; Shafer, R.; Staples, J.; Takeda, H.; Tallerico, P.

    1996-09-01

    We present status of high-power linac design studies for a proposed National Spallation Neutron Source (NSNS), based on a linac/accumulator-ring accelerator system. Overall project is a collaboration involving 5 national laboratories. ORNL will be responsible for the target, facilities, and conceptual design; BNL will be responsible for the ring; LBNL will be responsible for the injector, including the RFQ and a low-energy chopper in front of the RFQ; LANL will be responsible for the main linac; and ANL will be responsible for the instrumentation. The facility will be built at Oak Ridge. In the first phase, the dual-frequency linac with 402.5 and 805 MHz frequencies must deliver to the accumulator ring an H{sup -} beam near 1 GeV, with about 1 ms pulse length, a repetition rate 60 Hz, and average beam power {ge} 1 MW. The linac can be upgraded by a factor of 4 in beam power by increasing the dc injector current, and by funneling the beams from two 402.5 MHz low-energy linacs into the 805-MHz high-energy linac. Requirements for low beam loss in both linac and ring have important implications for linac design, including the requirement to provide efficient beam chopping to provide low-loss extraction for the ring. Linac design options and initial parameters are presented together with initial beam-dynamics simulation results.

  17. Droop Compensation for the High Voltage Converter Modulators at the Spallation Neutron Source.

    SciTech Connect

    Patel, Gunjan P; Anderson, David E; Solley, Dennis J; Wezensky, Mark W

    2012-01-01

    The Spallation Neutron Source (SNS) has been in operation since 2006 and routinely operates at 1 MW of beam power. At 1 MW, the High Voltage Converter Modulators (HVCMs) are delivering 8-11 MW pulsed power to the Klystrons for up to 1185 us at 60 Hz. The pulsed output of the modulator has a substantial voltage droop operating in open-loop mode. Achieving 1.4 MW operations require an increase in the output pulse width of the HVCM, resulting in loss of LLRF control margin due to modulator voltage reduction at the end of the pulse. Initially, the HVCM was designed with a pulse width modulation scheme for droop compensation but early operations at full duty revealed this technique unreliable. Increasing the output voltage of the modulator would likely compromise system reliability. This paper proposes the use of alternate modulation schemes to address the voltage droop. The effect of frequency modulation and phase modulation on voltage droop is studied. Experimental results will also be presented.

  18. Novel Large Area High Resolution Neutron Detector for the Spallation Neutron Source

    SciTech Connect

    Lacy, Jeffrey L

    2009-05-22

    Neutron scattering is a powerful technique that is critically important for materials science and structural biology applications. The knowledge gained from past developments has resulted in far-reaching advances in engineering, pharmaceutical and biotechnology industries, to name a few. New facilities for neutron generation at much higher flux, such as the SNS at Oak Ridge, TN, will greatly enhance the capabilities of neutron scattering, with benefits that extend to many fields and include, for example, development of improved drug therapies and materials that are stronger, longer-lasting, and more impact-resistant. In order to fully realize this enhanced potential, however, higher neutron rates must be met with improved detection capabilities, particularly higher count rate capability in large size detectors, while maintaining practicality. We have developed a neutron detector with the technical and economic advantages to accomplish this goal. This new detector has a large sensitive area, offers 3D spatial resolution, high sensitivity and high count rate capability, and it is economical and practical to produce. The proposed detector technology is based on B-10 thin film conversion of neutrons in long straw-like gas detectors. A stack of many such detectors, each 1 meter in length, and 4 mm in diameter, has a stopping power that exceeds that of He-3 gas, contained at practical pressures within an area detector. With simple electronic readout methods, straw detector arrays can provide spatial resolution of 4 mm FWHM or better, and since an array detector of such form consists of several thousand individual elements per square meter, count rates in a 1 m^2 detector can reach 2?10^7 cps. Moreover, each individual event can be timetagged with a time resolution of less than 0.1 ?sec, allowing accurate identification of neutron energy by time of flight. Considering basic elemental cost, this novel neutron imaging detector can be commercially produced economically

  19. High-pressure beamline (PLANET) at the spallation neutron source, J-PARC (Invited)

    NASA Astrophysics Data System (ADS)

    Kagi, H.; Hattori, T.; Arima, H.; Utsumi, W. S.; Komatsu, K.; Nagai, T.; Yagi, T.

    2009-12-01

    Material and Life Science experimental Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC) will be one of the most powerful spallation neutron facilities in the world. The pulsed neutron source with a liquid Hg target is designed to be running at 25 Hz with a power of 1 MW. We have started the construction of the powder diffractometer dedicated to high-pressure experiments (PLANET) on BL-11. PLANET aims to study structures of hydrogen-bearing materials including dense hydrous minerals of the Earth’s deep interior, magmas and light element liquids. The instrument will realize diffraction and radiography experiments for powder and liquid/glass samples at high pressures up to 20 GPa and 2000 K using a large sized multi-anvil hydraulic press that can apply forces of ˜1500 ton. The instrument views a decoupled liquid H2 moderator with a cross section of 100 × 100 mm2. The primary and secondary fight paths are 25 m and 1.5 m, respectively. The 11.5-m-long supermirror guide with elliptical shape starts at a distance of 11.5 m from the moderator. Design of elliptical geometry is optimized by means of incorporating several different grade mirrors and linear approximation with planar guide in order to save cost for production without degradation of the intensity performance. The guide has a rectangular cross-section and consists of four walls coated with supermirror material. Sample is placed at 2 m from the guide exit. The 90° detectors will be installed at 1.5 m from the sample position. For the powder diffraction measurements using a multi-anvil press, an incident neutron beam passes through the vertical anvil gaps and irradiates the sample in the pressure medium. Diffracted neutrons go through the other anvil gaps at 90° direction. Half inch 3He linear position sensitive detectors with 600 mm length will be arranged horizontally and form these detector banks, which cover the scattering angle of 79° ≤ 2θ ≤ 101° and -35° ≤ Φ ≤ +35°. The

  20. Spallation process with simultaneous multi-particle emission in nuclear evaporation

    SciTech Connect

    Santos, B. M.

    2013-05-06

    High energy probes have been used currently to explore nuclear reaction mechanism and nuclear structure. The spallation process governs the reaction process around 1 GeV energy regime. A new aspect introduced here to describe the nuclear reaction is the in-medium nucleonnucleon collision framework. The nucleon-nucleon scattering is kinematically treated by using an effective mass to represent the nuclear binding. In respect to the evaporation phase of the reaction, we introduce the simultaneous particles emission decay. This process becomes important due to the rise of new channels at high excitation energy regime of the compound nucleus. As results, the particles yields in the rapid and evaporation phases are obtained and compared to experimental data. The effect and relevance of these simultaneous emission processes in the evaporation chain is also discussed.

  1. Performance of the Los Alamos National Laboratory spallation-driven solid-deuterium ultra-cold neutron source

    SciTech Connect

    Saunders, A.; Makela, M.; Bagdasarova, Y.; Boissevain, J.; Bowles, T. J.; Currie, S. A.; Hill, R. E.; Hogan, G.; Morris, C. L.; Mortensen, R. N.; Ramsey, J.; Seestrom, S. J.; Sondheim, W. E.; Teasdale, W.; Wang, Z.; Back, H. O.; Broussard, L. J.; Hoagland, J.; Holley, A. T.; Pattie, R. W. Jr.; and others

    2013-01-15

    In this paper, we describe the performance of the Los Alamos spallation-driven solid-deuterium ultra-cold neutron (UCN) source. Measurements of the cold neutron flux, the very low energy neutron production rate, and the UCN rates and density at the exit from the biological shield are presented and compared to Monte Carlo predictions. The cold neutron rates compare well with predictions from the Monte Carlo code MCNPX and the UCN rates agree with our custom UCN Monte Carlo code. The source is shown to perform as modeled. The maximum delivered UCN density at the exit from the biological shield is 52(9) UCN/cc with a solid deuterium volume of {approx}1500 cm{sup 3}.

  2. Test of Time-Reversal Invariance Violation in Neutron Scattering At Spallation Neutron Sources

    NASA Astrophysics Data System (ADS)

    Gudkov, Vladimir

    2015-10-01

    Time Reversal Invariant Violating effects in neutron transmission through a nuclear target are discussed. A class of free from false asymmetries experiments is presented, and a comparison of a sensitivity of these transmission experiments and electric dipole moment measurements to different mechanisms of CP-violation is discussed. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics program under Award Number DE-FG02-09ER41621.

  3. Recent advances in high pressure neutron scattering at the Spallation Neutron Source at Oak Ridge National Laboratory

    NASA Astrophysics Data System (ADS)

    Tulk, C.; dos Santos, A.; Klug, D.; Guthrie, M.; Machida, S.; Molaison, J.

    2012-12-01

    There have been significant improvements in the operation of the high pressure diffractometer, SNAP, at the Spallation Neutron Source over the past two years. This talk will highlight the current capacities which include low temperature systems, high temperature systems, and the introduction of new pressure cell technology that is based on supported diamond anvils and, with advances in software, is particularly suited for powder diffraction. Specific examples of our recent research will focus on high pressure transitions in hydrogen bonded systems such as methane and CO2 hydrate. The high pressure hexagonal phase of methane hydrate is studied to determine the nature of the hydrate cage loading, this provides detailed experimental data that will lead to better intermolecular potentials for methane - methane interactions, particularly when methane molecules are in close contact and strongly repelling. The high pressure structural systematics of carbon dioxide hydrate is reported. While the structural transformation sequence of most hydrates progress from sI (or sII) to the hexagonal form then to a flied ice structure, CO2 hydrate is an example of a system that skips the hexagonal phase and transforms directly into the filled ice structure. Finally examples of using SNAP to study disorder in amorphous systems will be given. Particularly amorphous vapor co-deposits of water, known as amorphous solid water, and clathrate forming molecules such as CO2, and the structural response of these systems to increased pressure at low temperature.

  4. Neutron Emission Spectra from Inelastic Scattering on 58,60Ni with a White Neutron Source at FIGARO.

    SciTech Connect

    Rochman, D.; O'Donnell, J. M.; Devlin, M. J.; Ethvignot, T.; Granier, T.; Grimes, S. M.

    2005-01-01

    Neutron emission spectra from inelastic neutron scattering on natural nickel at the FIGARO facility have been measured by a double time-of-flight technique. The incident neutrons are produced from the spallation source of the Weapons Neutron Research facility, and their energies are determined by time of flight. The emitted neutrons and gamma rays are detected by 16 liquid scintillators and one high-resolution germanium or one barium-fluoride detector, respectively. The results for incident neutron energies from 2 to 10 MeV are compared with predictions of nuclear model calculations performed with the code EMPIRE-II. Finally, the level density parameters 'a' and '{Delta}E' are extracted.

  5. Design of a horizontal neutron reflectometer for the European Spallation Source

    NASA Astrophysics Data System (ADS)

    Nekrassov, D.; Trapp, M.; Lieutenant, K.; Moulin, J.-F.; Strobl, M.; Steitz, R.

    2014-08-01

    A design study of a horizontal neutron reflectometer adapted to the general baseline of the long pulse European Spallation Source (ESS) is presented. The instrument layout comprises advanced solutions for the neutron guide, high-resolution pulse shaping and beam bending onto a sample surface being thoroughly adjusted to the properties of the ESS. The length of this instrument is roughly 55 m, enabling δλ/λ resolutions from 0.5% to 10%. The incident beam is focused in horizontal plane to boost measurements of sample sizes of 1×1 cm2 and smaller with potential beam deflection in both downward and upward directions. The primary range of neutron wavelengths utilized by the instrument is 2-7.1 Å. If the wavelength range needs to be extended, then this is possible by utilizing only every second (third, fourth) pulse by suppressing all other pulses by the chopper system and thus increase the longest usable wavelength to 12.2 (17.3, 22.4) Å. Angles of incidence can be set between 0° and 9° with a total accessible q-range from 4×10-3 Å-1 up to 1 Å-1, while the δθ/θ resolution can be freely set. The instrument operates in both θ/θ (free liquid surfaces) and θ/2θ (solid-liquid, air-solid interfaces) geometries. The experimental setup will in particular enable direct studies on ultrathin films (d ≈10 Å) and buried monolayers to multilayered structures of up to 3000 Å total thickness. The horizontal reflectometer will further foster investigations of hierarchical systems from nanometer to micrometer length scale (the latter by off-specular scattering), as well as their kinetics and dynamical properties, in particular under load (shear, pressure, external fields). Polarization and polarization analysis as well as the GISANS option are designed as potential modules to be implemented in the generic instrument layout. The instrument is highly flexible and offers a variety of different measurement modes. With respect to its mechanical components the instrument

  6. H{sup -} radio frequency source development at the Spallation Neutron Source

    SciTech Connect

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

    2012-02-15

    The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent {approx}38 mA peak current in the linac and an availability of {approx}90%. H{sup -} beam pulses ({approx}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, {approx}60 kW) of a copper antenna that has been encased with a thickness of {approx}0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of {approx}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 {approx}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 {approx}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.

  7. Helium Bubble Injection Solution To The Cavitation Damage At The Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Francis, M. W.; Ruggles, A. E.

    2009-03-01

    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 wave 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.

  8. Helium Bubble Injection Solution To The Cavitation Damage At The Spallation Neutron Source

    SciTech Connect

    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 wave 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.

  9. Outgassing properties of the spallation neutron source ring vacuum chambers coated with titanium nitride

    NASA Astrophysics Data System (ADS)

    He, P.; Hseuh, H. C.; Mapes, M.; Todd, R.; Weiss, D.; Wilson, D.

    2004-05-01

    The stainless steel vacuum chambers of the 248 m accumulator ring of the Spallation Neutron Source are to be coated with ~100 nm of titanium nitride (TiN). This is to minimize the secondary electron yield from the chamber wall, and thus avoid the so-called e-p instability caused by electron multipacting as observed in a few high-intensity proton storage rings. Reports in the literature suggest that a TiN coating, by acting as a hydrogen permeation barrier, may also reduce the ultimate outgassing rate. The outgassing rate of TiN coated chambers deposited at various sputtering pressures was measured and compared to uncoated chambers, both with and without 250 °C in situ bake. Some coated chambers were subjected to glow discharge treatment (GDT). It was found that the surface roughness, analyzed with a scanning electron microscope, depends on the deposition pressure and is also influenced by GDT. The outgassing rate varies as a function of the surface roughness of the TiN layer, with rougher coatings more hydroscopic in nature. The in situ postbake outgassing rate was reduced ~30% for a chamber coated with TiN at low pressure and subsequently subjected to GDT, thus giving evidence that the TiN layer acts as a permeation barrier to hydrogen diffusion. It was also found that a 450 °C vacuum degas reduced the hydrogen outgassing rate one order of magnitude, although the amount of reduction does not agree with the value predicted by standard diffusion equations. .

  10. Design, status and first operations of the spallation neutron source polyphase resonant converter modulator system

    SciTech Connect

    Reass, W. A.; Apgar, S. E.; Baca, D. M.; Doss, James D.; Gonzales, J.; Gribble, R. F.; Hardek, T. W.; Lynch, M. T.; Rees, D. E.; Tallerico, P. J.; Trujillo, P. B.; Anderson, D. E.; Heidenreich, D. A.; Hicks, J. D.; Leontiev, V. N.

    2003-01-01

    The Spallation Neutron Source (SNS) is a new 1.4 MW average power beam, 1 GeV accelerator being built at Oak Ridge National Laboratory. The accelerator requires 15 converter-modulator stations each providing between 9 and 11 MW pulses with up to a 1 .I MW average power. The converter-modulator can be described as a resonant 20 kHz polyphase boost inverter. Each converter modulator derives its buss voltage from a standard substation cast-core transformer. Each substation is followed by an SCR pre-regulator to accommodate voltage changes from no load to full load, in addition to providing a soft-start function. Energy storage is provided by self-clearing metallized hazy polypropylene traction capacitors. These capacitors do not fail short, but clear any internal anomaly. Three 'H-Bridge' IGBT transistor networks are used to generate the polyphase 20 kHz transformer primary drive waveforms. The 20 kHz drive waveforms are time-gated to generate the desired klystron pulse width. Pulse width modulation of the individual 20 lcHz pulses is utilized to provide regulated output waveforms with DSP based adaptive feedforward and feedback techniques. The boost transformer design utilizes nanocrystalline alloy that provides low core loss at design flux levels and switching frequencies. Capacitors are used on the transformer secondary networks to resonate the leakage inductance. The transformers are wound for a specific leakage inductance, not turns ratio. This design technique generates multiple secondary volts per turn as compared to the primary. With the appropriate tuning conditions, switching losses are minimized. The resonant topology has the added benefit of being deQed in a klystron fault condition, with little energy deposited in the arc. This obviates the need of crowbars or other related networks. A review of these design parameters, operational performance, production status, and OWL installation and performance to date will be presented.