The two basic components in pulsed-power technology are capacitors and switches. In order to develop these high-voltage components, a unique laboratory has been constructed using state-of-the-art diagnostic and shielding techniques. The laboratory is comprised of three basic systems: charging systems, (2) diagnostic systems, and (3) grounding and shielding systems

Mace, P. N.

McDuff, G.

Rust, K.

Sarjeant, W. J.

UNT Digital Library

. Is~TITLE: DEVELOPMENT OF HIGH-RELIABILITY, MULTIKILOHERTZREPETITION-RATE, FAST-DISCHARGE COMPONENTSAUTHOR(S): G. McDuff, K. Rust, N. J. Sar.jeant, and P. N. MaceSUBMI’ITED TO: 1980 Fourteenth Pulse-Power Modulator SymposiumOrlando, FloridaJune 3-5, 1980By scceptenu of this article, the publisher reCC@.ZeGthat me U ,S. Government retains n non.exclwlve, royaltyfl’ee Umnm topubl.kh orrepr~)duccthepubl.khtd forrnof this contdbutlon, ortoBIIUW others to do co, for U,S, Governmentpllrposes.)l’%o LaAtemocSclentlflc LsbontorYr.quoti thatth publlsher identify M utlcle M work performedunder tho aueplms of:he Depertmant of Enargy,/ r%q)t[0s altamos r— —.-._ 1,’RCI AIMIN_ _ -- —-... ._, ._,,. ,,, ,L●clontlfae Smboratory,,, ,,,, ,.,,, ,,”,of tho Unlvoidty of California,, ,:,:,:;‘,: ‘, :,,’,.,.’! ,,,LoS ALAMOS, NEW MIXICO B7B4B,,,,, ,, ,,,,,, ,,,:,,,,,,,. ,,....-—.. . ._’ ,,.,,,,,,,4 ‘\.—— ~ --——.—— ...An ANhmatlva A(llon/EquolOppndwnhy fmployat.\Form No, UJ6 IllSLNo, 2629lt7aDEPARTMENT OF ENERQYCONTRACT W.740&EN13, 3a,, ). ,!, , ,ilih[ IL lIf{lllJ!lli.,( u, \,,,DEVELOPtIiENTOFHIGH-RELIABILITY,MULTIKILOHERTZ REPETITION-RATE,FAST-DISCHARGE COMPONENTSG. HcDuff. K. Rust. U. J. Sar.ieant.and P. PlaceLo; Alamos Scientific ~abor~toryP. O. BOX 1663Los Alamos, NH 87545Introduction—A pressing need has arisen for the development ofvery long-life, energy-transfer system components. Asadditional applications for fast pulse-power techniquesare conceived, especially in laser technology, compo-nent specificatiorlsbecome more and more severe. High-repetition rates, high-peak and rms currents, and ex-tremely high reliability are but a few of the difficultconstraints, The two basic components in pulsed-powertechnology are capacitors and switches. In order todevelop these high-voltage components, a unique labora-tory has been constructed using stat~-of-the-art diag-nostic and shielding techniques.The laboratory is comprised of three basic sys-tems:Charging systemsDiagnostic systemsGrounding and s:licldingsystemsThe block diagram in Fig. 1 sho~s the basic system lay-out, It is important to note that each system may beused separately or in conjunction with the ether systemblocks.In the first year of oper~tion, approximately 24different thyratrons, c~pacitors, sarurable inductors,and cllrrent-viewingresistors have been characterizedin the facility, A thorough invt?stigationof polypro-pylene/silicon oil low-loss capacitors has been madeand is discussed later.The Charging SystemsPerhaps the most important part of pulsed-powertechnolo y is poww conditioning, In the com orientde-velopment? laboratory, fboth resonant and pu se trans-former charging (corrsnandcharging) are used to fullycharacterize th~ bebvior of discharge components.Linear remafit charge voltages of 5 to 60 kV atrepetition rates to 3000 PPI,are available=. kiith Lhcuse of saturating inductors, peak-charge voltage; of 75kV a-e achieved, Pulse-forming-n@twork (PFN) cQptic!-tors up to 4 nF can be charged to 80 kV at 1OOI3-PPSrepetition rates, At reduced ope~’stingparameters, ~a~pacitors of several microfa:-adscan be operated in adfscharge circuit.Pulse-transformer charging extends the operttlngrange of the facility to a maximum charge voltaqe of120 kV at repetition rates of 5000 pps, Capacitor val-ues up to 15 nF can be charged in 2 to 10 IIS, bfa!l-plug efficiencies of 85X are tchie,~ed tifth presentpulse-tronsformw charginq syst,ms, and eff~ciencies ofgreater than 90% are expected in systems under develop-ment.Since the resonant and pulse-transform~r chorgingSystems are Completely separat@, a d!:cndrg~ circuitundmr investigation can be changmi from one to theother in a few minutes,uPOWERSUPPLIES1RESONANTCHARGINGSYSTEMri=lhPuLSE TRANSFORMERCHANGINGSYSTEM1~“,l-J~COMPONFNT DEVELOPMENTea.-.TANK-COMMONPOINTOROUNOhO14GNOSTICSSYSTEM GROUNDINGa SHIELDINGFig. 1. High-repetition rate component-develowentlaboratory operating system.DiagnosticsIn the field of cmnponcnt development, accurateand rellable diagnostic capabilities are essential.The heart of the laboratory dla?nostic center is a com-puter-controlled two-channel transient digitizer of50W4HZ bandwidth. Pulse-current measurement capabil-ities of up to 50 kA at 350-flHzbandwidth are incorpo-F@ted in the expcrirrentalarea. A recently dovelopcd250-kV dc to 1OO-MHZ passive high-voltage probe and a100-kV dc to 250-14Hzprobe complement the current neas-uremcnt capabilities. Uith other in-house diagnostictechniques, such as ion microprobe, x-ray topography,ad chemical analysis, a complete data base for thephys!cs, chemistry, and metallurgy of components it bc-lng establi~hed.A new thyratron current-viewing-rt?slstormountin!ltlange assembly, shown in Ftg, 2, was develope~iin con-junction with T L H Research, Albuquerque, New Fiexico.L~.{nduct.ante design ( ..40 n}l)and wide rang@ Of re-sistance values make it suitable for almost any cir-cuit. T’hlsnew diagnostic tool has been found to bcindispensable in thyratron circuits.iL..- – .—. .. —— --—-— - —--Fig. 2, Thyratron current-viewingflanqe assembly..C.spacltorsresistor/mountingAlong with the dev~lupment of various high-voita e7components, the present area of prime interest Is mu -tlkilohertz, long-life, low-inductance capacitors, Amajor program to fully rharacterlze capacitors designedfor pulse duty Is in progress. The motivation fOrpulse-capacitor development is threefold.● To obtain a data base to understaf,dthe physicsand chemical processes affecting capacftor life.● 10 develo low-loss, extremely long-life ctspaci-!tors >10 2 shots.● To interact with industry in designtng capaci-tors in the-range of 1 to 20 nF capable of10 kA/nF peak current In a 50- to 100-ns dis-charge.There are two configurations that meet the lcw-10ss requirements, silfcon oil/polypropylerreand dry,reconstltu?~d,mica-type capacitors.The equivalent series resistance (ESR) Is of primeimportance in determining the loss of the capacitorduring the discharge pulse. The ESR measurement wasapprc ‘,hedfrom several directions. The ro,lventionalmethod of deriving ESR from a ringing dlsch~rgc wasused along with phase shift, Fourier analysis, andtemperature variation measurements. A direct methodusfrrgcircuit theory applied to no~lirreart~me-varyins~cond-order cirruits was also used, Results from al!methods indicated an ESR of less than 100 mn, A 0,5%accuracy of resolution Is the ltmit of the present lab-oratory diagnostics, To make high-accuracy ESIImefis-urements al 50-kV, l-kA pulse levels at whfch tl)@ca-pacitors operate, a 0.02X resolution of accuracy wouldbe n@ed@d, In the WI propylene/silicon oil caphci-/tors, dependence of Ii etlme on repetition rate natbeen determined ai seen In Fig. 3, The repetition-ratedepcndcncc is due to a time-voltage stress relattonseen only in high dl/dt cfrcults,A new in situ method has been devised to detect aninwrinentfailure in polypropylene/silicon oil capaci-tors using partial-discharge detection techniques. Allcapacitors of this type tested have failed in the samepredictable manner due to the same failu-,smechanism.The method of capacitor-failure prediction ha; thus farproved to be 100% reliable.Th~ atronsHigh-average powzr switching is a major area inthe field of pulsed power. To meet the requirements oflong life, high-repetition rate, and low loss, th~ thy-ratron at prezent is the only viable choice. In a~di-tion to the above qualities, thyratrons require lesssupport equipment than high repetition-rate spark gapsand are far rrmreeconomical to use. Areas of thyr.atroninvestigation include efficiency, power and energyflow, and switching characteristics.One of the major problems to date in fast-dis-charge, kilohertz repetition-rate spark gap switchingis the large losses experienced (20 to 30Z) in theswitch. In lon -life, high-reliability circuitry such?losses are tots ly unacceptable. The thyratron lfis:esduring corrrnr.’tationn this fast-discharge circuit hav~been measured for the first time in this new facility.For stored energies of 1 to 1.2 J, this loss iu 2.2% atan 80-ns pulse tiidthand a peak curfent of 700 A. Thelosses wwe observed to decrease rapidly with increas-ing energy, as expected, so that low-loss switchin isfeasible with thyratrons, givinq long economical fifeat high switching efficiencies,New, comp.dct,short-pulse thyratrons are currentlyundr=rdevelopment for 50 to 100 kV multikilohertz per-?ation at current raies of rise in excess of 101 A/sat 10 to 100 kA peak c~rrent operation,System UpgradeThe present component-development laboratory hasan average power capability of 50 kki. A second facil-ity, capable of 300-kU continucu~ average power, isunder construction, The new facility is Simtlar inconcept Lo the existing laboratory with many advancesin diagnostic capabilities.. Two pr~jects planned forthe high-power laboratnfy a development of hic+h-energy density capacitors and PFNs for repetitivepulsed-power l~ser application.,1750I. ..0 ●nn !000 ProL-Pwn mm P-9?50 .1.—— — . - - —.- .-.. -.--—— ——..5 6LOG USt{(l T59Fig, 3. Lifattme vs pulse repetition rate for siliconoil/polypropylene.. . ,The high-repetition rate component-develop+,lent Is encouraged within the Los Alamos Scientific Labora-laburatory has received much internal support as well tory and are vital to the advancement of pulse-poweras support from industry. Interaction and technology technology.transfer between other national facilities and industry

Development of high-reliability, multikilohertz repetition-rate, fast-discharge components

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Development of high-reliability, multikilohertz repetition-rate, fast-discharge components

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