Marx Generators fo

Thomas Holt, Jon Mayes, Clay N

Abstract — Recent technological advancementdirected energy have led to increased demand foof driving high-power RF and high-power mradiators. APELC’s line of Marx generatoqualified for use in various directed enerExtensive testing performed on a 33-J Marx genbeen used as a source to drive various RFsummarized. Testing included characterizinbehavior of the Marx generator during operatiorepetition frequencies as well as monitorincharacteristics and reproducibility. Pulse charaother Marx generators varying from 10 mJ toenergy will also be provided. In addition, measudata from various radiators sourced by generators will be presented.

Keywords- Marx generator, HPM, directed wideband

I. INTRODUCTION Applied Physical Electronics, L. C.

developed an assortment of wave-erectigenerators since the company’s founding inAPELC family of Marx generators varies in swide by 2-in long PCB to an 18-in diametecylindrical vessel, and covers an energy rang1.8 kJ. A selection of Marx generators offeredbe summarized and data collected from highhigh power microwave (HPM) applications wThe presentation of information that focategorized according to the Marx generatdivided into a Marx generator performance secan applications section. This paper constituteand update to the previous document with a sim

II. A SAMPLE OF APELCS MARX GE

The specifications for APELC’s line of Masummarized in Table 1. They vary in size from2-in long PCB to an 18-in diameter and 72-ivessel and cover an energy range from 2 mJ to

Each Marx generator listed in Table 1 ismodel number that has the following formZZZZWF. XX represents the number of Marx YY enumerates the number of capacitors pdefines the magnitude of a single stage caidentifies the scale for the capacitance unnanofarad, and PF for picofarad). The MG1example, is a fifteen-stage Marx generator wcapacitors per stage.

for High-Power RF and MApplications

Nunnally, Matt Lara, Mark Mayes, Chris Hatfield, andApplied Physical Electronics, L. C.

Austin, TX 78734 thomas.holt@ieee.org

ts in the field of or sources capable

microwave (HPM) ors are uniquely rgy applications.

nerator, which has F loads, will be ng the thermal

on at various pulse ng output pulse

acteristics for nine o 1.8 kJ in output ured RF and HPM

APELC’s Marx

energy, low-jitter,

(APELC) has on style Marx n 1998 [1]. The size from an 8-in er and 72-in tall ge from 2 mJ to d by APELC will h power RF and

will be presented. ollows will be tor and will be ction followed by es a continuation milar title [2].

ENERATORS arx generators are m an 8-in wide by in tall cylindrical 1.8 kJ.

s identified by a m; MGXX-YYC-

generator stages, per stage, ZZZZ apacitor, and W nit (i.e. NF for 5-3C-940PF, for

with three 940-pF

A. Circuit Board Marx GeneratorsAPELC has developed circuit-b

using solid-state TRAPATT diodswitch circuit board Marx generatorco-planar waveguide generators. capability to be powered by convrepetition rates over 100 Hz and canpower to a matched load for eachoutput voltage waveform from a ggenerator (MG10-1C-1NF).

B. MG15-3C-940PF The MG15-3C-940PF (or MG15

generator and is used extensively inits 50-Ohm impedance. The MG15 cpulse repetition frequency (PRF) at extensive use of the MG15 in a vgenerated voluminous amounts of psummarized in the sections that follo

1) Burst-Mode Performance The burgeoning directed energy (DEfor compact, robust, and enegenerators. APELC adapted its MG1in 2006 to meet the aforementionedThe MG15 is a dry-air insulated system that is capable of limited bcharge voltage at a maximum PRFeighteen sequentially-fired output woperating at 200-Hz PRF and a maxkV are provided in Figure 2 (a). VPRF and charge voltage level is prowaveforms in Figure 2 (b). The MLambda-TDK 802-L HVPS (a conslimits the MG15 to a maximum a(including 1 ms of clear time betw

Figure 1 – Output voltage waveform Marx generator driving a 50-Ohm load.

Microwave

d Jeremy Byman

board-level Marx generators de switches, gas-discharge rs, and conformally-mapped The generators have the ventional battery packs at n deliver up to 1 MW peak

h pulse. Figure 1 shows an gas-discharge switch Marx

5) is APELC’s staple Marx n many applications due to can be operated at a 200-Hz 40-kV charge voltage. The

variety of applications has performance data, which are ow.

E) field has created demand ergy-dense pulsed power 15 for burst-mode operation d demands of the DE field. and cooled pulsed power

burst-mode operation at full F of 200 Hz. An overlay of waveforms from an MG15 ximum charge voltage of 40 Verification of the claimed vided by the charge voltage

MG15 was charged with a stant current supply), which achievable PRF of 210 Hz ween Marx events). Higher

from a 10-stage circuit board

978-1-4244-7129-4/10/$26.00 ©2010 IEEE 385 381

Model Number Maximum

Charge Voltage

MaximuEnergy p

Pulse [kV] [J]

MG10-1C-1NF 1 0.005 MG15-3C-940PF 40 33 MG40-3C-2700PF 40 266 MG20-1C-100NF 20 400 *Predicted values assume an optimized Lambda-TD** Rise time calculated using 20% - 80% standard. AAdditional models available but not discussed in MG16-3C-2700PF, MG30-3C-100NF, MG20-22C-

(a)

(b)

Figure 2 – (a) Superposition of 18 output wavduring burst-mode operation at 200-Hz PRF at voltage. (b) Corresponding Marx generator (blgenerator (gray) charge voltage waveforms.

PRFs are achievable by using a higher powernot yet been tested.

2) Lifetime Study Accurate prediction of the lifetime of a M

dependent upon a confluence of operational highly probable that an MG15 operated in swith minutes of downtime between shots cexperimenter with minimal maintenance. It is that an MG15 operated at maximum charge would fail thermally within 20 secondsoperation.

APELC developed a LabView-controLifetime testbed to monitor the electrical isignals as well as the internal thermal condMG15 components during operation at varioulevels and PRFs. Thermal conditions of intewere monitored by an Omega FOB104 temcapable of measuring temperature from four ioptic thermometers with a switching rate of channels. Data recorded from electrical withheld due to their similarity to the resuFigure 2.

Table 1 – Summary of Marx generators um per

Peak Erected Voltage

Estimated Marx

Impedance

Rise Time Length

HousDiam(Wid

[kV] [Ω] [ns] [in] [in10 < 50 0.8** 8 (2600 52 0.5 – 5 31 – 36 5

1,600 70 1 – 7 72 8400 20 ~100 41 10

DK 303-L power supply with no size or weight constraints. All other rise times quoted using 10% - 90% standard. this manuscript: MG17-1C-500PF, MG17-1C-940PF, MG10-1

-2000PF, MG20x8-3C-2200PF-PFN.

veforms measured maximum charge

lack) and Trigger

r HVPS but have

Marx generator is parameters. It is

single-shot mode could outlive an equally probable voltage and PRF of continuous

olled, automated input and output dition of various us charge voltage ernal components mperature sensor independent fiber 250 ms between diagnostics are

ults presented in

Experimentation showed that occurred at the spark gap electrodeswas present in the direction of the Mgradient corresponds directly witenergies that bridge each subsequMG15 erection (due to wave erectiacquired at 30-kV charge voltage dHz PRF is provided in Figure 3. It to failure, that a temperature of apfourteenth stage temperature diagnthermal failure of the MG15. This upper service temperature of the indirect proximity to the electrodecollected over the course of the lifeof acceptable burst lengths providenoted that the acceptable burst leachievable burst length, rather the mtested and, consequently, recommenoperation of the MG15. Thermal remonitored and typically showed thapproximately 3 scfm, a 1 minutwould cool the MG15 to a accommodate any subsequent burst

The shot log kept during the lifetotal of 239,120 shots were fired levels on the same spark gap eletransfer, QT, of 16.2 Coulombs. electrode lifetime measured in numcharge voltages, VC, can be computtotals 143,324 shots at full voltage. the lifetime study remains in service

Figure 3 – Temperature monitoring foside spark gap electrode for the eighthstages. Data were accumulated durisummarized in Table 2.

sing meter/

dth)

Maximum PRF verified/(predicted*)

n] [Hz] 2) 50/(1000) 5 200/(300) 8 4/(80) 0 10/(50)

1C-940PF, MG10-1C-2700PF,

the highest thermal stress s and that a thermal gradient MG15 erection. The thermal th the increasing electron uent spark gap during the ion). Example thermal data

during a 15-sec burst at 200 was found, through testing

pproximately 210° F on the nostic marked the onset of

closely corresponds to the nsulating material found in e pairs. The thermal data etime testing yielded the list ed in Table 2. It should be ength is not the maximum maximum burst length safely nded by APELC for reliable elaxation profiles were also hat under constant flow of e purge following a burst

temperature that would as defined in Table 2.

etime study indicated that a at different charge voltage

ectrodes for a total charge The minimum expected

mber of shots, NE, at various ted using Equation (1), and The Marx that was used for

e to this day.

or the buswork near the high- (gray) and fourteenth (black) ing burst-mode operation as

386 382

Table 2 – Summary of Acceptable Burst Lengtoperating conditions

Charge Voltage PRF Acceptable B

Length[kV] [Hz] [sec] 20 100 150 20 200 50 30 100 40 30 200 15 35 100 10

3) TTL to Marx Output Jitter Applications requiring low jitter betwe

trigger command and a subsequent high voltcan be accommodated by APELCs line of Maroverlay of 19 TTL and Marx output waprovided in Figure 4. The waveform pairs arbitrary units as the relative timing between tthe only parameter of interest. Analysis showevent follows an average of 45.36 ns after the with a jitter of 1.84 ns. Additional jitter mepresented in [3].

4) Peaking Circuit Many applications, such as direct rad

generator output, require the use of a peaking output pulse rise times that can be efficieantennas that are not prohibitively large. APEmodular peaking circuit that replaces a traditiosection and is capable of achieving sub-nanoswhen driving a cable load of matched summarized in Table 3. This demonstratimprovement over the standard rise time of 4.690) and 3.41 ± 0.26 ns (20-80) and aimprovement over the results presented in [4]. 1000 psi) breathable dry air confined to thesection is used as the insulating dielectric. capable of integrating crowbar switches intosections to control output pulse fall time.

C. MG20-1C-100NF The MG20-1C-100NF (MG20) is a 20

generator suitable for driving HPM loads suOutput voltage waveforms acquired with operated in burst mode are provided in Figure

Figure 4 – Jitter measurement data for an MG15 ofull charge voltage. The black traces are a TTprovided by a delay generator used to initiate the Mgray traces are the MG15 output waveforms.

ths for different

Burst h

(1)

een a TTL-level tage output pulse rx generators. An

aveform pairs is are provided in

the 50% points is ws that the Marx trigger command

easurements were

diation of Marx circuit to achieve ntly radiated by

ELC developed a onal MG15 output second rise times

impedance, as es a significant 69 ± 0.15 ns (10-an even greater High pressure (>

e modular output APELC also is

o modular output

-Ω, 400-J Marx uch as a vircator.

a 20-Ohm load 5.

operating at 75% of TL reference pulse Marx event and the

Table 3 – Various rise times correspondvoltage leve

Charge Voltage Rise Time (10-[kV] [ns] 20 0.48 30 2.48 35 0.67

III. APPLICA

Throughout the past decade, APtechnology in a variety of differsections summarize recent applicatyears, of APELCs line of Marx gene

A. MG15-3C-940PF The MG15 has seen the most

customers for a variety of applisourcing a variety of impulse radcharging various resonating loads. selection of APELCs applicationsMG15-like Marx generator.

1) APELCs Suite of Wideband DAPELCs suite of proprietary

presently covers the frequency ranMHz which are driven by the Mamplitudes exceeding 200 kV/m whof 1 m have been recorded. Figmeasurement made by an unddemonstrates the burst mode cawideband dipole system.

2) Additional Applications of thA modified MG15 was used t

transparent TEM horn feeding a pelectric field of greater than 200 kVachieved. Additional details are prov

APELC developed an EMP tesdevice under test as large as 40” x 2height). The test-bed can be drivenmodules which meet the RS-105 aas defined by MIL-STD 461 C/E/Fbasis technology used to drive theinformation on APELCs EMP Test-

B. 12-ft Radiating Dish sourced byAn impulse radiating antenna s

dish was developed using the MGthe source. The MG40 was mopeaking circuit [4], then adapted to fed a 12-ft diameter, fiberglass ptransition consisted of a coaxial-to-pconverted the 70-Ohm coaxial MarxOhm parallel plate TEM-horn feesection had a two-way transit time to feed the pseudo-transparent TEMconstructed with telescoping armsrested on sliding rails to allow for rphase center given the operatinggenerator.

ding to different MG15 charge els -90) Rise Time (20-80)

[ns] 0.22 0.85 0.59

ATIONS PELC has applied its Marx rent areas. The following tions, within the past three erators in the DE field.

use by APELC and other ications including directly diating antennas and pulse The following are a small

s involving the use of an

Dipole Radiators wideband dipole radiators

nge from 100 MHz to 400 MG15. Peak electric field hen normalized to a distance gure 6 is an electric field isclosed third party and

apability of the 400-MHz

he MG15 to directly source a semi-parabolic reflector. A peak V/m normalized to 1 m was vided in [5].

t-bed that accommodates a 24” x 16” (length x width x n by two separate front-end nd RS-05 testing standards

F. A modified MG15 is the e EMP test-bed. Additional bed can be found in [6].

y the MG40-3C-2700PF similar to the 6-ft radiating

G40-3C-2700PF (MG40) as dified to accommodate a a custom RF transition that arabolic reflector. The RF parallel plate transition that x generator output to a 110-ed. The parallel plate feed of 10 ns prior to flaring off

M horn. The TEM horn was s and the Marx generator real time positioning of the

g conditions of the Marx

387 383

Figure 5 – Superposition of 10 output waveformburst-mode operation at 10-Hz PRF at maximum ch

Figure 6 – A small sample of waveforms captur400-MHz dipole radiator by a third party. The waconstructed by stacking independent trigger eve500-ns windows of data over the course of a burstat a repetition rate of 150 Hz. The diagnostic wasEFS and was at a distance of 4 meters from the dipo

A measured impulse recorded using an AHSAS-570 double ridged horn as a receiving antFigure 7 (a) and the corresponding spectral deFigure 7 (b). The center frequency of the mainis near 400 MHz, however, the low frequencycomparatively lower amplitude (~ 70 kV/m) rithe spectral density. System size prohibimapping of the antenna pattern; however, an Hwas performed. As expected, the main lobe isight of the system (in the direction normal reflector) and has a 3-dB beamwidth of adegrees. The far field of the antenna is estbetween 11.1 m and 38.4 m from the aperdepending on the far-field criterion appliedfrequency chosen.

C. Microwave System sourced by the MG20-1A first-generation planar vircator was driv

and marked APELCs first foray into the realmdevelopment. The observed center frequencpresented in Figure 8 swept from near 1.5 GHsecond-generation cathode is under developmesteps are being taken to improve performance.

IV. CONCLUSIONS APELC is working diligently to meet

compactness, robustness, and repetition raplaced on systems required by the DE field. applications listed herein and others too numdemonstrate APELCs growing breadth of expbe applied to realize deployable DE systems.

ms measured during

harge voltage.

red from APELCs

aveform above was ents comprised of t of 200 shots fired s a Nanofast 709-1 ole radiator.

H-Systems model tenna is shown in

ensity is shown in n radiated impulse y (200 MHz) and inging dominates ited a complete H-plane mapping is along the bore to the parabolic

approximately 18 timated to begin rture of the dish d and the center

1C-100NF ven by the MG20 m of HPM source y from the data

Hz to 2.8 GHz. A ent and additional

the demands of ate performance The sources and

merous to include perience that can

(a)

(b)

Figure 7 – (a) A measured radiated impDish normalized to a distance of 1 mspectral density. The accuracy of the dependent and is expected to be withinthe radiated signal.

Figure 8 – Microwave output frommicrowave load sourced by the MG20-1

REFERENC

[1] J. R. Mayes, W. J. Cary, W. C. NunMarx Generator as an Ultra WidebandInternational Pulsed Power Conferen1668.

[2] J. R. Mayes, W. J. Carey, “The DirMicrowaves with Compact Marx GeneInternational Conference on High-Melhorn, and M. A. Sweeney (eds.), N

[3] J. R. Mayes, W. J. Carey, W. C. NunNanosecond Jitter Operation of Marx474.

[4] T. A. Holt, M. B. Lara, C. NunnallyGenerators Modified for Fast RiseInternational Pulsed Power Conferen1197-1200.

[5] T. A. Holt, M. G. Mayes, M. B. Lara,Driven Impulse Radiating Antenna,” ib

[6] J. R. Mayes, M. B. Lara, W. C. Nunna“An Ultra-Portable Marx Generator461E/F RS-105 Testing,” ibid. [4], pp.

pulse from the 12-ft Radiating m and (b) the corresponding amplitude in (a) is frequency

n 20% of the true amplitude of

m APELCs first generation 1C-100NF.

ES nnally, and L. L. Altgilbers, “The d Source,” Proceedings of the 13th nce, Las Vegas, 2001, pp. 1665-

rect Generation of High Power erators,” in Beams 2002: The 14th Power Particle Beams, T. A.

New York: AIP, 2002, pp. 299-302. nnally, and L. L. Altgilbers, “Sub-x Generators,” ibid. [1], pp. 471-

y, J. R. Mayes, “Compact Marx time,” Proceedings of the 17th ce, Washington, D.C., 2009, pp.

J. R. Mayes, “A Marx Generator bid. [4], pp. 489-494. ally, M. G. Mayes, and J. Dowden, -Based Solution for MIL STD 1433-1438.

388 384