NASA Scientific and Technical Aerospace Reports

20040047242 Lawrence Livermore National Lab., Livermore, CA
Investigation of Vacuum Insulator Surface Dielectric Strength with Nanosecond Pulses
Nummally, W. C.; Krogh, M.; Williams, C.; Trimble, D.; Sampayan, S.; Jun. 03, 2003; 10 pp.; In English
Report No.(s): DE2004-15005840; UCRL-JC-151647; No Copyright; Avail: Department of Energy Information Bridge
The maximum vacuum insulator surface dielectric strength determines the acceleration electric field gradient possible in
a short pulse accelerator. Previous work has indicated that higher electric field strengths along the insulator-vacuum interface
might be obtained as the pulse duration is decreased. In this work, a 250 kV, single ns wide impulse source was applied to
small diameter, segmented insulators samples in a vacuum to evaluate the multi-layer surface dielectric strength of the sample
construction. Resonances in the low inductance test geometry were used to obtain unipolar, pulsed electric fields in excess of
100 MV/m on the insulator surface. The sample construction, experimental arrangement and experimental results are
presented for the initial data in this work. Modeling of the multi-layer structure is discussed and methods of improving
insulator surface dielectric strength in a vacuum are proposed.
NTIS
Electric Fields; Field Strength; Pulse Duration; Dielectrics
20040047243 Lawrence Livermore National Lab., Livermore, CA
Tables of Neutron-induced Fission Cross Sections for Various Pu, U, and Th Isotopes, Deduced from Measured Fission
Probabilities
Younes, W.; Britt, H. C.; Mar. 31, 2003; 18 pp.; In English
Report No.(s): DE2004-15005842; UCRL-ID-152906; No Copyright; Avail: Department of Energy Information Bridge
Cross sections for neutron-induced fission of (sup 231, 233)Th, (sup 234,235,236,237,239)U, and (sup 240,241, 243)Pu
are presented in tabular form for incident neutron energies of 0.1(le) E(sub n)(MeV)(le) 2.5. The cross sections were obtained
by converting measured fission probabilities from (t,pf) reactions on mass-A targets to (n,f) cross sections on mass-A+ 1
neutron targets, by using modeling to compensate for the differences in the reaction mechanisms.
NTIS
Neutrons; Neutron Cross Sections; Plutonium Isotopes; Thorium Isotopes; Uranium Isotopes
20040047244 Lawrence Livermore National Lab., Livermore, CA
POINT 2003: A Temperature Dependent ENDF/B-VI, Release 8 Cross Section Library
Cullen, D. E.; May 22, 2003; 20 pp.; In English
Report No.(s): DE2004-15005843; UCRL-ID-127776-R2; No Copyright; Avail: Department of Energy Information Bridge
The ENDF/B data library has recently been updated and is now freely available through the National Nuclear Data Center
(NNDC), Brookhaven National Laboratory. This most recent library is identified as ENDF/B-VI, Release 8. Release 8
completely supersedes all preceding releases. Release 8 will be the last release of ENDF/B-VI; the next release of ENDF/B
data will be for the new ENDF/B-VII library. As distributed the ENDF/B-VI, Release 8 data includes cross sections
represented in the form of a combination of resonance parameters and/or tabulated energy dependent cross sections, nominally
at 0 Kelvin temperature.
NTIS
Cross Sections; Temperature Dependence
20040047253 Lawrence Livermore National Lab., Livermore, CA
Superconducting Detector Endstation for High-Resolution Energy-Dispersive SR-XRF
Friedrich, S.; Drury, O.; Niedermayr, T.; Cunningham, M. F.; van den Berg, M. L.; Sep. 15, 2000; 18 pp.; In English
Report No.(s): DE2004-15005851; UCRL-JC-138005; No Copyright; Avail: Department of Energy Information Bridge
We have built a two-stage adiabatic demagnetization refrigerator (ADR) to operate cryogenic high-resolution x-ray
detectors in synchrotron-based fluorescence applications. The detector is held at the end of a 40 cm cold finger that extends
into a UHV sample chamber. The ADR attains a base temperature below 100 mK with about 24 hours hold time below 400
mK, and does not require pumping on the liquid He bath. We will discuss cryostat design and performance.
NTIS
Superconductivity; X Ray Detectors; Magnetic Fields; Magnetic Cooling
20040047254 Lawrence Livermore National Lab., Livermore, CA
Position Resolution Studies with MSU 32-Fold Segmented HPGe Detector
Lehner, C. E.; Vetter, K.; Kunh, A.; Schmid, G. J.; Beckedahl, D. A.; Oct. 25, 2001; 12 pp.; In English
Report No.(s): DE2004-15005670; UCRL-JC-143745; No Copyright; Avail: Department of Energy Information Bridge
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