Bank Upgrade for Sspx at Llnl Page: 3 of 6
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BANK UPGRADE FOR SSPX AT LLNL
M.M. Marchiano, E.G. Cook, R.W. Geer, R.O. Kemptner, H.S. McLean, N.N.
Martovetsky, J.M. Moller, K.L. Morris, B.W. Stallard, J.A. Watson, and R.D. Wood
Sustained Spheromak Physics Experiment, Lawrence Livermore National Lab
Livermore, CA 94551, U.S.A.Abstract
A new 5kV, 1.5MJ modular capacitor
bank has been designed for the Sustained
Spheromak Physics Experiment (SSPX) at
LLNL. The new bank consists of thirty 4mF
capacitors that are independently controlled
by light-triggered thyristors. By closing all
switches simultaneously, the bank will
provide a mega-ampere discharge. The new
bank will also allow additional capabilities
to SSPX, including higher peak gun current,
longer current pulses, and multi-pulse
plasma buildup. Experiment results for a
single stage prototype will be presented.
I. INTRODUCTION
Currently SSPX has two capacitor banks
used for plasma production. The formation
bank is a 12 capacitor 10kV, 0.5MJ bank
that produces a 0.5ms 600kA current spike
to initially create the plasma in SSPX. The
sustainment bank is a 30 capacitor, 5kV,
1.5MJ bank that produces a 3ms 250kA
current pulse that sustains the plasma.
Unfortunately, these two banks provide little
variability in pulse shape.
The modular bank is designed to deliver
a greater variety of pulse shapes to SSPX. It
is much like the sustainment bank except
that each capacitor has its own dedicated
switch so that it is more like thirty mini-
banks than a single large bank. Each switch
in the bank can be individually triggered
allowing each capacitor to begin its energydump into the plasma at any point in time.
All switches can be triggered together to
deliver a single large current spike, or,
switches can be triggered in sequence to
deliver a longer lower current pulse.
Multiple pulses can be created by triggering
sections of the modular bank in intervals.
- -I
0. Present bank
(MA) DA
4 2 4 6 6 10
time (rns)
Figure 1. Typical current pulse delivered by
the formation and sustainment banks
overlaying waveform objectives for the
modular bank.
II. AN INDIVIDUAL MODULE
Each module consists of a 4mF, 5kV,
50kJ capacitor, an optically triggered
thyristor, a current limiting inductor, two
series diodes, one anti-parallel diode, and
low resistance cable to connect each module
to SSPX.* This work was performed under the auspices of the U.S. Department of Energy by the University of California
Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48
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Marchiano, M. M.; Cook, E. G.; Geer, R. W.; Kemptner, R. O.; McLean, H. S.; Martovetsky, N. N. et al. Bank Upgrade for Sspx at Llnl, article, May 31, 2005; Livermore, California. (https://digital.library.unt.edu/ark:/67531/metadc876246/m1/3/: accessed April 26, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.