ULTRA-LOW-JITTER REPETITIVE SOLID STATE PICOSECOND SWITCIDNG*

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1 ULTRA-LOW-JTTER REPETTVE SOLD STATE PCOSECOND SWTCDNG* C. A. Fros, T. H. Marin, and R. J. Focia Pulse Power Physics, nc Red Oaks Loop NE Albuquerque, NM J. S. H. Schoenberg Air Force Research Laboraory/Direced Energy Direcorae 3550 Aberdeen Ave SE Kirland AFB, NM Absrac Ulra-low-jier repeiive solid sae picosecond swiching is being developed for applicaion o elecromagneic impulse sources. Ulra-low-jier and fas riseime are required o synchronize muliple modules of radiaing array sources. Laser conrolled phooconducing swiches provide low jier bu have limied lifeime and are oo expensive for many commercial applicaions. We are sudying an alernaive mehod using inexpensive delayed avalanche breakdown semiconducor closing swiches in an arificial ransmission line configuraion o generae powerful elecromagneic shockwaves. As an example of he new echnology, we presen experimenal resuls for a miniaure (volume < 25 cm 3 ) 3 kv pulser which provides RMS jier of 16 ps wih 100 ps riseime a 2 khz repeiion rae. The miniaure pulser employs 18 delayed breakdown silicon avalanche swiches in a differenial shockline opology. SPCEbased circui modeling resuls are compared o experimenal measuremens. The circui modeling includes effecs of sray capaciy and a Mone-Carlo jier analysis. The picosecond pulsers can be used for impulse sources, Pockels cell drivers, rigger generaors, and pulse power applicaions. The modeling echniques are applicable o Marx generaors and circuis conaining large numbers of swiches wih capaciive cross coupling.. DELAYED BREAKDOWN SWTCHNG The delayed breakdown effec was discovered by. V. Grekhov and A. F. Kardo-Sysoev of he offe nsiue in S. Peersburg, Russia.[l,2] When cerain silicon diode srucures are rapidly overvoled beyond saic breakdown, here is a delay of several nanoseconds before a fas breakdown. Figure 1 shows a ypical delayed breakdown device (DBD) srucure. Picosecond breakdown occurs as an ionizaion wave sweeps across he inrisic maerial faser han he carrier drif velociy. Doping: p' em ' n - 10" em ' n' em ' Anode Cahode n 5o~ l o~m Fig. 1. Delayed breakdown device srucure ' ' \ f \ \ Time (ns) Fig. 2. Measured volage wavefonns show driving pulse (dashed) & sharpened oupu pulse (solid line) e niversy of New Mexico Sc ool of Elecrical Engineering recenly evaluaed DBD swiching echnology by esing Russian DBD devices.[3,4] Commercial silicon devices have also demonsraed This work was suppored in par by he Unied Saes Air Force, AF Maeriel command, AF Research Laboraory/Small Business Office, 3550 Aberdeen Avenue SE, Kirland AFB, NM J99/$10.00@19991EEE. 291

2 Repor Documenaion Page Form Approved OMB No Public reporing burden for he collecion of informaion is esimaed o average 1 hour per response, including he ime for reviewing insrucions, searching exising daa sources, gahering and mainaining he daa needed, and compleing and reviewing he collecion of informaion. Send commens regarding his burden esimae or any oher aspec of his collecion of informaion, including suggesions for reducing his burden, o Washingon Headquarers Services, Direcorae for nformaion Operaions and Repors, 1215 Jefferson Davis Highway, Suie 1204, Arlingon VA Respondens should be aware ha nowihsanding any oher provision of law, no person shall be subjec o a penaly for failing o comply wih a collecion of informaion if i does no display a currenly valid OMB conrol number. 1. REPORT DATE JUN REPORT TYPE N/A 3. DATES COVERED - 4. TTLE AND SUBTTLE Ulra-Low-Jier Repeiive Solid Sae Picosecond Swiching 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNT NUMBER 7. PERFORMNG ORGANZATON NAME(S) AND ADDRESS(ES) Pulse Power Physics, nc Red Oaks Loop NE Albuquerque, NM PERFORMNG ORGANZATON REPORT NUMBER 9. SPONSORNG/MONTORNG AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONTOR S ACRONYM(S) 12. DSTRBUTON/AVALABLTY STATEMENT Approved for public release, disribuion unlimied 11. SPONSOR/MONTOR S REPORT NUMBER(S) 13. SUPPLEMENTARY NOTES See also ADM EEE Pulsed Power Conference, Diges of Technical Papers , and Absracs of he 2013 EEE nernaional Conference on Plasma Science. Held in San Francisco, CA on June U.S. Governmen or Federal Purpose Righs License. 14. ABSTRACT Ulra-low-jier repeiive solid sae picosecond swiching is being developed for applicaion o elecromagneic impulse sources. Ulra-low-jier and fas riseime are required o synchronize muliple modules of radiaing array sources. Laser conrolled phooconducing swiches provide low jier bu have limied lifeime and are oo expensive for many commercial applicaions. We are sudying an alernaive mehod using inexpensive delayed avalanche breakdown semiconducor closing swiches in an arificial ransmission line configuraion o generae powerful elecromagneic shockwaves. As an example of he new echnology, we presen experimenal resuls for a miniaure (volume c 25 cm3) 3 kv pulser which provides RMS jier of 16 ps wih 100 ps riseime a 2 khz repeiion rae. The miniaure pulser employs 18 delayed breakdown silicon avalanche swiches in a differenial shockline opology. SPCEbased circui modeling resuls are compared o experimenal measuremens. The circui modeling includes effecs of sray capaciy and a Mone-Carlo jier analysis. The picosecond pulsers can be used for impulse sources, Pockels cell drivers, rigger generaors, and pulse power applicaions. The modeling echniques are applicable o Marx generaors and circuis conaining large numbers of swiches wih capaciive cross coupling. 15. SUBJECT TERMS 16. SECURTY CLASSFCATON OF: 17. LMTATON OF ABSTRACT SAR a. REPORT unclassified b. ABSTRACT unclassified c. THS PAGE unclassified 18. NUMBER OF PAGES 4 19a. NAME OF RESPONSBLE PERSON

3 Sandard Form 298 (Rev. 8-98) Prescribed by ANS Sd Z39-18

4 delayed breakdown and can perform as picosecond swiches.[5] We have exended his echnique o low jier command riggered shockline pulsers using muliple devices. Figure 2 shows experimenally measured waveforms for a cm 2 area silicon device. The daa were acquired wih a Tekronix sampling digiizer. The slow rising (dashed line) waveform is he pulse charging waveform, while he fas rising waveform is he oupu volage from he diode shaper. The wo waveforms are ime correlaed. The DBD swich was effecive a blocking he prepulse and slow rise and swiching rapidly near peak volage giving a riseime of 355 ps o a kv peak volage wih a pulse widh (FWHM) of 1.45 ns. The pulse charging waveform had a riseime of 2150 ps. To Comparison o Experimen 0,~ 400 q q /. \ "" ' \ / 'o.aoo \ r?; ~ 4 //.f - -,_ Transien ime (e) Fig. 3. Simulaion of delayed breakdown in silicon f reduce he circui inducance, we consruced a igh coaxial es fixure. This configuraion gave faser swiching wih riseime of 135 ps o 2.2 kv. The Silvaco 2-D device physics code was used o model he srucure of figure 1. Figure 3 shows ha he simulaion gives good agreemen wih he measuremen of figure 2. This is one example of many simulaions which were performed o undersand he delayed breakdown process. Silicon carbide (SiC) devices were also sudied. Figure 4 shows exremely good swiching resuls for a SiC device wih a srucure similar o figure 1.. SHOCKLNE PULSERS We use muliple delayed breakdown avalanche swiches in a apered arificial ransmission line srucure o achieve high volage ulra-fas pulses. The delayed breakdown swiches are used in series wih he inducors of an LC-ladder-line as shown by figure 5. The firs swich is riggered, and all of he oher swiches are overvoled. The riggered swich can be a bipolar avalanche ransisor, MOSFET, or a laser conrolled phooconducing swich. Fig. 5. Closing swiches in series wih he inducors of an LC-ladder-line generae EM-shockwaves A higher oupu level can be delivered o a balanced load by operaing wo opposiely charged sacks of delayed breakdown devices as a balanced pulser. This configuraion provides a pair of simulaneous opposie polariy oupu pulses. The wo swich sacks are synchronized by cross connecing each sage wih a capacior. The high volage differenial oupu allows efficien coupling o a balanced ulra-wideband impulse radiaing anenna wihou need of a balun nework. ~ BOOO S900 f 3800 > 1---l---+k"~F-~--ll"---'lrf---l, ~00~~-"~'""-""'~" _ /!'""..., \ ll \ _ \ \ \... ~~~~~~~ -~... -:- \ \.... _... ~~d f--... ~..._... ~~-...-~ 0 O 1111/e(ns) Fig. 4. Simulaion of SiC device shows A V= 6.2 kv, A = 50 ps, and dv/d = 1.24x V /s. Fig. 6. A balanced version of he LC-ladder-line pulser using delayed breakdown swiches gives differenial oupu Figure 6 il usraes e balanced shockline which evolves from he unbalanced circui by mirror image reflecion abou he ground plane. This circui has he advanage of auomaically synchronizing each sage hrough he cross coupling capacior.. PULSER SMULATONS We modeled he differenial9-sage pulser using SPCE simulaion. The volage conrolled laching swich model was repeaed 18 imes, and saisical variaions in swich 292

5 breakdown volage were also sudied. The breakdown volage was se a 450 V for each of he 18 swiches. An increase of 150 V above he saic volage was required o TME (,.) Fig. 9. Simulaion resul for oupu volage waveform ino a 1 00 ohm balanced load break down he swich. Figure 7 shows he volage waveform across each of he 18 swiches. Swich #1 is fired a ime zero, swich #2 breaks down a approximaely 63 ps, and each successive swich breaks down wih a shorer ime inerval as he elecromagneic shockwave builds. The wo sides of he sack, self synchronized o wihin 1 ps. V. PULSER MEASUREMENTS We performed experimenal measuremens on a balanced pulser which validaed SPCE based circui modeling. The dual polariy 9-sage pulser provided a balanced oupu volage of3.18 kv wih a 0.1 ns riseime. The posiive and negaive oupus were well synchronized, and command riggering jier of below 16 ps was achieved. The experimenal resuls show good agreemen wih he simulaion predicions. The balanced oupu pulser circui was fabricaed on a prined circui board wih 9 swiches on each side of he board for a oal of S-swiches. The wo 9-sage swich sacks were synchronized by capacior cross coupling a each sage as shown by figure 6. The firs sage swich on one side only was a base riggered bipolar ransisor operaed in avalanche mode. All oher swiches were silicon devices operaed in delayed breakdown mode. Each 50 ohm oupu fed a separae 50 ohm high volage aenuaor. The Tekronix sequenial sampling digiizer was exernally riggered. TME (M) Fig. 8. Simulaed curren waveform for sage 1 of he 9-sage LC-ladder-line pulser Figure 8 shows he curren waveform passing hrough he firs swich. The curren rises o a consan level. A fla curren waveform in he fus swich indicaes proper uning he sage capaciors. Figure 9 shows he simulaion predics a 94 ps riseime 3.5 kv oupu pulse ino a 100 ohm resisive load. 01~----~--~----~----~----~ Nanoseconds Fig. 10. Differenial oupu volage waveform 293

6 The posiive and negaive oupu volage waveforms were numerically combined o give he differenial volage. Figure 10 shows he resuling oupu volage waveform. The riseime is 104 ps o a peak volage of 3.18 kv. The fas rising edge was hen digiized wihou averaging. A leas squares linear fi o he daa gave an RMS command rigger jier value ofbelow 16 ps. Table 1 gives he values for he key pulser oupu parameers. The firs row of able 1 shows he SPCE simulaion where all 18 swiches are se o break down a a fixed volage level of 450 V. The second row shows he resuls of a Mone Carlo simulaion where he 18 swiches are each se o break down a a volage of 450 V ± 1%. The lised variaions (±xx) on he able represen he calculaed one sandard deviaion levels for he se of 101 runs. impulse wih a peak elecric field of 1 kv/m a 3 meer range.[6] Figure 11 shows he measured elecric field waveform on-axis and 3 meers from he source. Figure 12 shows he source being calibraed oudoors on a nonconducing plaform. Table 1. BALANCED 9-STAGE PULSER Peak Peak RMS Case Volage Rise ime dv/d Jier kv ps kv/ns ps SPCE Mone Carlo 3.52± ± ± Measuremen < 16 V. RADATNG MPULSE SOURCE The 3 kv shockline pulser was combined wih a 9-inch diameer dielecric lens anenna o form a compac radiaing impulse source. The compac source which operaes from a 12-vol lanern baery provides a 100 ps l! ) Time (nanosewnds) Z Jm Fig. 11. Measured elecric field waveform wih he probe on axis and 3 meers from source Fig 12. Phoograph of he experimenal seup used o characerize he compac impulse source REFERENCES [1].V. Grekhov and A.F. Kardo-Sysoev, "Subnanosecond Curren Drops in Delayed Breakdown of Silicon p-n Juncions", Sov. Tech. Phys. Le. 5 (8), 395, [2].V. Grekhov, "Mega and Gigawas-ranges, Repeiive Mode Semiconducor Closing and Opening Swiches", proc. 11h EEE nernaional Pulsed Power Conference, July [3] R.J. Focia, E. Schamiloglu, C.B. Fleddermann, W.C. Nunnally, and J. Gaude, "Silicon Diodes in Avalanche Pulse Sharpening Applicaions," EEE Trans. on Plasma Science, 25, 138 (1997). [4] R.J. Focia, E. Schamiloglu, and C.B. Fleddermann, "Simple echniques for he generaion of high peak power pulses wih nanosecond and subnanosecond rise imes," Rev. Sci. nsrum, 67 (7), , July (5] D.M. Benzel and M.D. Pocha, Rev. Sci. nsrum. 56, 1456 (1985). [6] J.S.H. Schoenberg, C.A. Fros, T.H. Marin, and R.J. Focia, "Low Cos, High Repeiion Frequency mpulse Radiaing Sources and Arrays Using Delayed-Breakdown Device Elecromagneic Shocklines", o be published in proc. High Power Microwave Conf., May