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April 1999 Highlights 0 Fig, -
0 time-of-flight and
the xbrernsstrahlung tie-
e Pnals on Shot 396.
Pulsed Power Inertial
Confinement Fusion Program r_ sohsignal
2440 260 20 ---oo optics ln
trroe of flight (ns)
In April we received a DOE Defense Programs award for ,
significant contributions to the Nuclear Weapons Pro-
gram in developing and applying z-pinch x-ray sources to gas ine -
stockpile stewardship. DOE also recognized pulsed nempeare -- -
power for outstanding performance at a world-class level Fig. 2. Z hard-
as part of the FY98 performance appraisal review. There ware that sue-
were 1 3 Z shots: 3 for LANL weapon physics, 2 to pre- cessfully civoell -
pare to measure the D, equation of state (EOS), 4 to cooled D- to
22 I{ anode plate-
assess energetics of single-sided drive with the z-pinch- 2p
driven hohlraum, and 4 to study the variation in x-ray power with the mass of a copper converter foil
inside a nested wire array for the dynamic hohlraum.
We hosted an April 27-28 workshop on the potential of z pinches for inertial fusion energy. The topics
discussed were reactor chamber design, simplifying the targets using magnetic thermal insulation or dou-
ble shells rather than cryogenic DT. the use of disposable electrodes, and methods to achieve "standoff"
by separating the high-yield implosions from accelerator hardware. On May 6-7 we will host a workshop
to review progress in integrated target designs for the three z-pinch high-yield hohlraum configurations.
On three dynamic hohlraum shots in March, beam-generated neutrons were produced with deuterated
polystyrene to test the neutron diagnostics. The CD was in the form of 50 pm wires in the inner array of a
nested array (Shot 396) or as an annular converter (Shots 397 and 398). We measured (1.9-5.5) x 10 I
beam-generated deuterium neutrons with three detectors (neutron-time-of-flight, indium, and lead probe).
The timing of the neutron production was determined from a bremsstrahlung signal coincident with the x-
ray diode signals (Fig. 1). The data suggest that high-energy (5-6 MeV) deuterium ions are traveling
along the z axis. The neutron-time-of-flight technique, in conjunction with the use of deuterated materi-
als, affords a new, sensitive measure for the production of energetic ions in the vicinity of the pinch.
We are modeling the magnetohydrodynamic (MHD) behavior of conductors at ultra-high current density
in conjunction with Z experiments. Unlike previous accelerators that were in the I Tesla regime, Z's disc
magnetically-insulated transmission lines are in a 100-1200 Tesla regime. Hence, its conductors cannot
be modeled as static, infinite-conductivity boundaries. Using the MACH2 code, we are studying the con-
ductor hydrodynamics and characterizing the joule heating, magnetic diffusion, material deformation,
and material properties for a range of current densities, rise times, and conductors. Our goals are to pre-
dict power flow losses accurately, model the response of particle velocity probe (VISAR) samples in var-
ious configurations, and incorporate appropriate EOS and conductivity models in the MHD simulations.
Our results will be qualitative until the conductivity model in the code is improved, since it overestimates
magnetic field penetration into metals at low temperatures.
Using a cryocell (Fig. 2), cooling of deuterium to a liquid state has been achieved on Z. The purpose of
this research is to obtain data on the deuterium EOS. We are fielding 12 VISARs, three spectrographs,
and a fiber-optics shock breakout array. Preliminary data indicate that the metallic state of liquid deute-
rium is observed at a pressure of 500 kbars with the VISAR system on these experiments.
Contact: Jeff Quintn. Inertial Confinement Fusion Program. Dept. 1602, 505-845-7245, fax: 505-845-7464, email: jpquint@sandia.gov.
Highlights are prepared by Mary Ann Sweeney, Dept. 1602, 505-845-7307, fax: 505-845-7890, email: masween( sandia.gov.
Archived copies of the HighlghrA beginning July 1993 are avai lthc at h1p://N w w.saidiugov/pulspowr/hedict/highlgh.
Sandia National Laboratories Inertial Confinement Fusion Program
