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To determine the safety of using argon as a deuteron beam stopping material, the

Physically realized electron gas systems usually reside in either the quantum non-degenerate or fully degenerate limit, where the average de Broglie wavelength of the thermal electrons becomes comparable with the interparticle distance between electrons. A few systems, such as young brown dwarfs and the cold dense fuels created in imploded cryogenic capsules at the National Ignition Facility, lie between these two limits and are partially degenerate. The National Ignition Facility has the unique capability of varying the electron quantum degeneracy by adjusting the laser drive used to implode the capsules. This allows experimental studies of the effects of the degeneracy level on plasma transport properties. By measuring rare nuclear reactions in these cold dense fuels, we show that the electron stopping power, which is the rate of energy loss per unit distance travelled by a charged particle, changes with increasing electron density. We observe a quantum-induced shift in the peak of the stopping power using diagnostics that measure above and below this peak. The observed changes in the stopping power are shown to be unique to the transition region between non-degenerate and degenerate plasmas. Our results support the screening models applied to partially degenerate astrophysical systems such as young brown dwarfs. Transitions between non-degenerate and degenerate plasma are observed in laser-driven implosions of cryogenic capsules at the National Ignition Facility. The observed partially degenerate regime is relevant to the physics of young brown dwarfs.

The international monitoring system exists to verify compliance with the terms of the comprehensive test ban treaty. About 10% of the member stations will be capable of detecting radioxenon, which can be produced in nuclear detonations or through civilian processes. We have studied the activation of radioxenon by the prompt, intense spectrum of 14-MeV neutrons produced at the National Ignition Facility. While 14-MeV neutrons are not currently a significant contributor to the production of radioxenon, we find that radioxenon produced through activation of environmental xenon by 14-MeV neutrons would be distinguishable from activation by nuclear tests.

We determined fission yields of xenon (133mXe, 135Xe, 135mXe, 137Xe, 138Xe, and 139Xe) resulting from 14 MeV neutron induced fission of depleted uranium at the National Ignition Facility. Measurements begin approximately 20 s after shot time, and yields have been determined for nuclides with half-lives as short as tens of seconds. We determined the relative independent yields of 133mXe, 135Xe, and 135mXe to significantly higher precision than previously reported. The relative fission yields of all nuclides are statistically indistinguishable from values reported by England and Rider (ENDF-349. LA-UR-94-3106, 1994), with exception of the cumulative yield of 139Xe. Considerable differences exist between our measured yields and the JEFF-3.1 database values.

RATIONALE Noble gases dissolved in groundwater can reveal paleotemperatures, recharge conditions, and precise travel times. The collection and analysis of noble gas samples are cumbersome, involving noble gas purification, cryogenic separation and static mass spectrometry. A quicker and more efficient sample analysis method is required for introduced tracer studies and laboratory experiments. METHODS A Noble Gas Membrane Inlet Mass Spectrometry (NG-MIMS) system was developed to measure noble gases at natural abundances in gas and water samples. The NG-MIMS system consists of a membrane inlet, a dry-ice water trap, a carbon-dioxide trap, two getters, a gate valve, a turbomolecular pump and a quadrupole mass spectrometer equipped with an electron multiplier. Noble gases isotopes (4)He, (22)Ne, (38)Ar, (84)Kr and (132)Xe are measured every 10 s. RESULTS The NG-MIMS system can reproduce measurements made on a traditional noble gas mass spectrometer system with precisions of 2%, 8%, 1%, 1% and 3% for He, Ne, Ar, Kr and Xe, respectively. Noble gas concentrations measured in an artificial recharge pond were used to monitor an introduced xenon tracer and to reconstruct temperature variations to within 2 °C. Additional experiments demonstrated the capability to measure noble gases in gas and in water samples, in real time. CONCLUSIONS The NG-MIMS system is capable of providing analyses sufficiently accurate and precise for introduced noble gas tracers at managed aquifer recharge facilities, groundwater fingerprinting based on excess air and noble gas recharge temperature, and field and laboratory studies investigating ebullition and diffusive exchange.

Precisely-known fission yield distributions are needed to determine a fissioning isotope and the incident neutron energy in nuclear security applications. 14 MeV neutrons from DT fusion at the National Ignition Facility induce fission in depleted uranium contained in the target assembly hohlraum. The fission yields of Kr isotopes (85m, 87, 88, and 89) are measured relative to the cumulative yield of

The high-fluence neutron spectrum produced by the National Ignition Facility (NIF) provides an opportunity to measure the activation of materials by fast-spectrum neutrons. A new large-volume gas-cell diagnostic has been designed and qualified to measure the activation of gaseous substances at the NIF. This in-chamber diagnostic is recoverable, reusable and has been successfully fielded. Data from the qualification of the diagnostic have been used to benchmark an Monte Carlo N-Particle Transport Code simulation describing the downscattered neutron spectrum seen by the gas cell. We present early results from the use of this diagnostic to measure the activation of natXe and discuss future work to study the strength of interactions between plasma and nuclei.

The Radiochemical Analysis of Gaseous Samples (RAGS) diagnostic apparatus operates at the National Ignition Facility (NIF). At the NIF, xenon is injected into the target chamber as a tracer, us ed as an analyte in the NIF targets, and generated as a fission product from 14 MeV neutron fission of depleted uranium contained in the NIF hohlraum. Following a NIF shot, the RAGS apparatus used to collect the gas from the NIF targ et chamber and then to cryogenically fractionate xenon gas. Radio-xenon and other activation products are collected and counted via gamma spectrometry, with the results used to determine critical physics parameters including: capsule areal density, fuel-ablator mix, and nuclear cross sections. We will discuss the following performance upgrades to the system: Modification of the xenon fractionator to allow collection of krypton. Krypton is an important target analyte and is also generated as fission gas in NIF shots. We have modified the cryostat to enable fractionation of xenon, krypton, or both. A translatable detector for quantification of the fission gases. An in situ Germanium detector is used to count the radio isotopes collected on the coldhead. NIF shots that incorporate depleted uranium in the hohlraum generate large amounts of fission gas, the radioactivity of which paralyzes the detector. We have designed a system that will adjust the detector-to-coldhead distance based upon either the count rate or the time after the NIF shot. Keywords: krypton, radiochemistry, cryogenic, nuclear diagnostic

The generation of dynamic high energy density plasmas (HEDP) in the pico- to nano-second time domain at high-energy laser facilities affords unprecedented nuclear science research possibilities. At the National Ignition Facility (NIF), the primary goal of Inertial Confinement Fusion research has led to the synergistic development of a unique high brightness neutron source, sophisticated nuclear diagnostic instrumentation, and versatile experimental platforms. These novel experimental capabilities provide a new path to investigate nuclear processes and structural effects in the time, mass and energy density domains relevant to astrophysical phenomena in a unique terrestrial environment. Some immediate applications include neutron capture cross-section evaluation, fission fragment production, and ion energy loss measurement in electron-degenerate plasmas. More generally, the NIF conditions provide a singular environment to investigate the interplay of atomic and nuclear processes such as plasma screening effects upon thermonuclear reactivity. Achieving enhanced understanding of many of these effects will also significantly advance fusion energy research and challenge existing theoretical models.

For the first time, 41Ar produced by the (n,ϒ) reaction from 40Ar in the beryllium shell of a DT filled Inertial Confinement Fusion capsule has been measured. Ar is co-deposited with beryllium in the sputter deposition of the capsule shell. Combined with a measurement of the neutron yield, the radioactive 41Ar then quantifies the areal density of beryllium during the DT neutron production. The measured 1.15 ± 0.17 × 10+8 atoms of 41Ar are 2.5 times that from the best post-shot calculation, suggesting that the Ar and Be areal densities are correspondingly higher than those calculated. Possible explanations are that (1) the beryllium shell is compressed more than calculated, (2) beryllium has mixed into the cold DT ice, or more likely (3) less beryllium is ablated than calculated. Since only one DT filled beryllium capsule has been fielded at NIF, these results can be confirmed and expanded in the future.

Precisely-known fission yield distributions are needed to determine a fissioning isotope and the incident neutron energy in nuclear security applications. 14 MeV neutrons from DT fusion at the National Ignition Facility induce fission in depleted uranium contained in the target assembly hohlraum. The fission yields of Kr isotopes (85m, 87, 88, and 89) are measured relative to the cumulative yield of 88Kr and compared to previously tabulated values. The results from this experiment and England and Rider are in agreement, except for the 85mKr/88Kr ratio, which may be the result of incorrect nuclear data.

C.B. Yeamans, W. Cassata, J.A. Church, D.N. Fittinghoff, M. Gatu Johnson, N. Gharibyan, R. Hatarik, D.B. Sayre, H.W. Sio, R.M. Bionta, D.L. Bleuel, J.A. Caggiano, C.J. Cerjan, G.W. Copper, M.J. Eckart, E.R. Edwards, S.A. Faye, C.J. Forrest, J.A. Frenje, V.Yu. Glebov, P.F. Grant, G.P. Grim, E.P. Hartouni, H.W. Herrmann, J.D. Kilkenny, J.P. Knauer, A.J. Mackinnon, F.E. Merrill, K.J. Moody, M.J. Moran, R.D. Petrasso, T.W. Phillips, H.G. Rinderknecht, D. H. G. Schneider, S.M. Sepke, D.A. Shaughnessy, W. Stoeffl, C.A. Velsko, P. Volegov 1 Lawrence Livermore National Laboratory, Livermore, California, USA 2 General Atomics, San Diego, California, USA 3 Los Alamos National Laboratory, Los Alamos, New Mexico, USA 4 Massachusetts Institute of Technology, Cambridge, Massachusetts, USA 5 University of California, Berkeley, Berkeley, California, USA 6 University of New Mexico, Albuquerque, New Mexico, USA 7 University of Rochester, Laboratory for Laser Energetics, Rochester, New York, USA yeamans1@llnl.gov

The Radiochemical Analysis of Gaseous Samples (RAGS) diagnostic apparatus was recently installed at the National Ignition Facility (NIF). Following a NIF shot, RAGS is used to pump the gas load from the NIF chamber for purification and isolation of the noble gases. After collection, the activated gaseous species are counted via gamma spectroscopy for measurement of the capsule areal density and fuel-ablator mix. Collection efficiency was determined by injecting a known amount of (135)Xe into the NIF chamber, which was then collected with RAGS. Commissioning was performed with an exploding pusher capsule filled with isotopically enriched (124)Xe and (126)Xe added to the DT gas fill. Activated xenon species were recovered post-shot and counted via gamma spectroscopy. Results from the collection and commissioning tests are presented. The performance of RAGS allows us to establish a noble gas collection method for measurement of noble gas species produced via neutron and charged particle reactions in a NIF capsule.

We are developing 3H AMS to measure 3H activity of mg-sized biological samples. LLNL has already successfully applied 14C AMS to a variety of problems in the area of biomedical research. Development of 3H AMS would greatly complement these studies. The ability to perform 3H AMS measurements at sensitivities equivalent to those obtained for 14C will allow us to perform experiments using compounds that are not readily available in C-tagged form. A 3H capability would also allow us to perform unique double-labeling experiments in which we learn the fate, distribution, and metabolism of separate fractions of biological compounds.

Radiochemical diagnostic methods are currently under development for the National Ignition Facility (NIF). Samples in the gas-phase offer a direct method of collection by pumping out the large target chamber following a NIF shot and transporting the gas down-stream for further analysis. Ignition capsules will have a small amount (roughly 1015 atoms) of dopant added to the inner-most layers of the ablator shell. These elements will undergo nuclear activation from neutrons, deuterons, or alpha particles produced via the fusion process. For example, doping 124Xe and 127I in the shell will create activated xenon isotopes that can be correlated to the amount of fuel ρR and long-range mix in the capsule. We are building the Radiochemical Analysis of Gaseous Samples (RAGS) apparatus for collecting and analyzing activated gases produced via the ignition process. Following a shot, gases will be pumped out of the chamber and transported to a two-part system. The first part consists of a pre-filter that will remove particulates and other reactive gases. The second part is a cryogenic xenon collection station where xenon will be isolated, and will then either be removed for mass spectrometric analysis, or counted via gamma spectroscopy. Preliminary results from RAGS commissioning will be presented and future improvements to the apparatus will also be discussed.

Radiochemical diagnostic techniques such as solid- and gas-phase capsule debris analysis may prove to be successful methods for establishing the success or failure of ignition experiments at the National Ignition Facility (NIF). Samples in the gas phase offer the most direct method of collection by simply pumping out the large target chamber following a NIF shot. The target capsules will be prepared with dopants which will produce radioactive noble gas isotopes upon activation with neutrons. We have designed the Radchem Apparatus for Gas Sampling (RAGS) in order to collect post-shot gaseous samples for NIF capsule diagnostics. The design of RAGS incorporates multiple stages intended to purify, transfer, and count the radioactive decays from gaseous products synthesized in NIF experiments.

Three low-pressure rocket motor burn tests were executed in May--June 1997 time frame at the X-tunnel complex located on the Department of Energy's Nevada Test Site.

This is the first demonstration of the use of accelerator mass spectrometry (AMS) as a tool for the measurement of 3H with attomole (10(-18) mol) sensitivity in a biological study. AMS is an analytical technique for quantifying rare isotopes with high sensitivity and precision and has been most commonly used to measure 14C in both the geosciences and more recently in biomedical research. AMS measurement of serially diluted samples containing a 3H-labeled tracer showed a strong correlation with liquid scintillation counting. The mean coefficient of variation of 3H AMS based upon the analysis of separately prepared aliquots of these samples was 12%. The sensitivity for 3H detection in tissue, protein, and DNA was approximately 2-4 amol/mg of sample. This high sensitivity is comparable to detection limits for 14C-labeled carcinogens using 14C AMS and demonstrates the feasibility of 3H AMS for biomedical studies. One application of this technique is in low-dose, dual-isotope studies in conjunction with 14C AMS. We measured the levels of 3H-labeled 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 14C-labeled 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) in rat liver tissue and bound to liver DNA and protein 4.5 h following acute administration of individual or coadministered doses in the range of 4-5100 pmol/kg of body weight. Levels of PhIP and MeIQx in whole tissue and bound to liver protein were dose-dependent. MeIQx-protein and -DNA adduct levels were higher than PhIP adduct levels, which is consistent with their respective carcinogenicity in this organ. Coadministration of PhIP and MeIQx did not demonstrate any measurable synergistic effects compared to administration of these compounds individually. These studies demonstrate the application of AMS for the low-level detection of 3H in small biological samples and for its use in conjunction with 14C AMS for dual-labeling studies.

Collection of representative samples of debris following inertial confinement fusion implosions in order to diagnose implosion conditions and efficacy is a challenging endeavor because of the unique conditions within the target chamber such as unconverted laser light, intense pulse of x-rays, physical chunks of debris, and other ablative effects. We present collection of gas samples following an implosion for the first time. High collection fractions for noble gases were achieved. We also present collection of solid debris samples on flat plate collectors. Geometrical collection efficiencies for Au hohlraum material were achieved and collection of capsule debris (Be and Cu) was also observed. Asymmetric debris distributions were observed for Au and Be samples. Collection of Be capsule debris was higher for solid collectors viewing the capsule through the laser entrance hole in the hohlraum than for solid collectors viewing the capsule around the waist of the hohlraum. Collection of Au hohlraum material showed the opposite pattern: more Au debris was collected around the waist than through the laser entrance hole. The solid debris collectors were not optimized for minimal Cu backgrounds, which limited the conclusions about the symmetry of the Cu debris. The quality of the data limited conclusions on chemical fractionation effects within the burning, expanding, and then cooling plasma.

Point design ignition capsules designed for the National Ignition Facility (NIF) currently use an xray-driven Be(Cu) ablator to compress the DT fuel. Ignition specifications require that the mass of unablated Be(Cu), called residual mass, be known to within 1% of the initial ablator mass. The specifications also require that the implosion bang time, a surrogate measurement for implosion velocity, be known to 50 ps RMS. Experiments designed to measure and to tune experimentally the amount of residual mass are being developed as part of the National Ignition Campaign (NIC). Tuning adjustments of the residual mass and peak velocity can be achieved using capsule and laser parameters. We currently plan to measure the residual mass using streaked radiographic imaging of surrogate tuning capsules. This technique, together with bang time measurements, should allow us to tune ignition capsules to meet NIC specs.

Samples of bulk meteorites show only mass-dependent fractionation of silicon isotopes. No isotopic anomalies were found. The variation of the ratios 29 Si/ 28 Si and 30 Si/ 28 Si over the meteorite classes is small; 1%. per mass unit difference. The average Si isotopic composition for each class of meteorites is identical, within analytical uncertainties. This is quite unlike O, whose anomalous isotopic abundances in bulk samples differentiate among the classes of meteorites. The overlapping abundance ranges of Si isotopes among many classes of meteorites suggest closed-system behavior for this element prior to meteorite accretion and allow calculation of an average solar system Si isotope composition.

Two forsterite-, fassaite-, spinel-rich inclusions in Allende which share common mineralogy and texture with three previously described inclusions are described. These inclusions were at least partially molten at temperatures over 1400 C, and their crystallization sequence was spinel, olivine, fassaite, and Mg-rich melilite. At least some of them experienced partial volatilization of MgO and SiO2 from their outer margins. At least one of the inclusions is highly enriched in MgO relative to CaO and Al2O3 compared to Allende coarse-grained inclusions, although it is just as strongly enriched in refractory trace elements as the latter, relative to C1 chondrites. Two of the objects are FUN inclusions on the basis of their oxygen, magnesium, and silicon isotopic compositions.