Multi-megampere operation of plasma compression opening switches in planar geometry Page: 3 of 6
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kiiltihegahpere operation op plasma compression
OPENING SWITCHES IN PLANAR GEOMETRY*
J. R. Goforth, D. J. Erickson. A. H. Williams mod A. B. Groan*
Los Alaaoa NatIonaL Laboratory
Loo Alaaoa, Haw Mexico 87545
Abstract
Experiments ara described in which a plasaa compres-
sioa opening switch la used In pLunar geometry to
sharpen the output pulse of an explosive-driven Mag-
netic flux coapranalon generator. Included are data
from teats where peak opening switch currents range
froa 5.7 to 9.3 KA. The switch Is used to transfer
current to a static low-inductance load >'-10 nH) with
an efficiency of SOX or better and a riser lme as low
as 0.45 us. Results related to current transfer ara
Interpreted wltnln a simple analytical Modal.
Introduction
Pulse sharpening with a plasaa compression opening
switch technique was first reported by Pavlovskll et
al. The opening mechanism In their switch was an In-
crease In plasaa resistance caused by the explosive
depression of a cylindrical pLasoa cavity. The power
source In the Pavlovskll exnerlnent was an expLoelve-
drlven Magnetic flux compression generator. We have
adapted the plasma compression technique to planar ge-
ometry for use with plate-type explosive genera-
tors.'1 In work reported previously, 5 snail scale
tests were performed at noderate currents to establish
paraaeters for the technique. These saaller devices
employed high quality, inexpensive plane-wave lens
detonation systeas. Ve report here the resulta of ex-
periments with switches char are Increased In slae for
currenra In rhe 5-10 MA range. Used wlrh plate gener-
ators, these switches now provide a practical source
for curient pulses with rlsetlmes Ot a microsecond or
less. The results presented here are froa cxperlmenrs
that characrerlxe rhe opening switch In circuit* con-
taining static, low Inductance loads. Other pcpers In
this conierence report on rhe use of the switch to
drive a dynamic '-pinch loa-l.
Pulsaxl Tower Sysrem
The Circuit for the sya'em Is shown in Tig. 1. The
components are an explosive general or denoted by a
rise-dependent Inductance Lj. an opening switch
represented by Li and a variable resistance Ri, a
closing switch 5 and a load Lj. Trnr.._.al ->aton line In-
ductances are Lumped Into 1 he lOsplscnt parumai ora.
The generators In out experiments are desc> lbed
by Cal '"■I e al." Typical generirot charact ._-rl at IcS
are Initial Induct an. e of 250-100 ull. peak Source Im-
pedance of 10—>0 mil, and gener,i.ji (flux) ..lupl1 -u>
rime Oi 1=.— 1 jp us. l»ro Ilrly low ImpedaScC '■.•■>■1*1 1 1
few nil ->ii>l a few mill, the plate genets, ors nee.I tiers
ate rapabLe of piuduclnjt I 'll IM', aa high aa 1* SA.
Tiu. plane1 .i|i«i«i11,,. *wl ■.n ]>. ■■■■■wu t,i i i ■* '* ■ 2 su-i 1.
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.Injur, In Klg. 2. 1 lie S'" ‘I"" I -' 1 ■* 1 Is e >1 .1*1*1’J l-i I he
uplirt l*nl Low-l pi a'es ef ihls - .1..1.1 -l-i I I -111 el
p.j-ititeu I. Tl>e loud a*, leml11 I . Isolaie.l liy . Lesli.p
qwllclien. are al'Sclied -|l |*.*sl I l-uin *2 >11 1. A il.le
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■| • I we « el ■ uni llu-iepli lie- s'- "»ei el *i| su*l -ipi-uliiA •■vl|l>li
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■ |.,l F . ■ ■ ii.| ■■■ I lug |*1 id In llu* nWll.li * h -111 rlr. , IT*r
p ijtad. aim lulilaim-l 11 ■>. ihlu f I I u -it a | *im I iiaia l ha I
*Uul k a.||»i»"lt I mil by tile IIH U.|'a|llw.ii" "if I'nvlgv.
Fig. 1. Circuit for opening switch rests.
have bean vapor deposited on the Teflon Insulators.
Current flows radially Inward In the upper channel of
Fig. 3, and outward In rhe Lower channel. Plasma com-
pression Is obtained from the breakout of planar deto-
nation fronts from the explosive disks. The high
quallry fronts are obrained from explosive lenses (nor
shown), which are placed on the PBX 9501 compressIon
charges.
The closing switches were arranged In a varlery of
■sulrlchannel line configurer lone. In all -rases Lhey
used sheers of polyei r.ylene t-j separate switch elec-
trodes. The polyethylene sheets were punctured In a
number of places by th-- action of small explosive
charge*. The sansltlvlcy of these devices to the
voltage across the switch dielectric requires In situ
testing ro determine precise switch closing rime under
expcrlmenial conditions. We have used rhe swltthen ro
hold off and men i lose ar v-r-Lrages from 2«i ro 70 kV.
The lGads for these experlmcnis were single-turn cdll
blocks designed fur <a specific fixed InJuc'ance.
InlrlolLy. we connected -a single 15-r.H load -ar
position 2 of Fig. 2. In utder >o decr-Mae f.c effec-
tive load Ind-icrance In Subsequent experiments. we
used parallel loa-ta a' posl'lone 3. In ■ he L-ai • er
configutaiIon rhe load Inducrmncaw were reduced to
6-8 nH.
The -Jaa.li-d n.*a|uuiicr In operji lng n.. pnLamd |i.jw-r
aymem lifxlnx wlrli V.i.i.ll>ig l lie Iiilllnl fliix lnl,i 11..-
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Goforth, J. H.; Erickson, D. J.; Williams, A. H. & Greene, A. E. Multi-megampere operation of plasma compression opening switches in planar geometry, article, January 1, 1985; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc1093651/m1/3/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.