N15A-T023 TITLE: Advanced Solid State Switch (Diode) Materials for High Rep Rate Pulse Power Systems and High Power Radio Frequency (HPRF) Applications

TECHNOLOGY AREAS: Materials/Processes, Electronics, Weapons

ACQUISITION PROGRAM: ONR 352: High Power Radio Frequency Research and Electromagnetic Railgun INP

OBJECTIVE: Develop, design, and fabricate new solid state switch (diode) materials and demonstrate them in standard form factor mountings. These switches are envisioned for use in HPRF applications on tri-service platforms. The proposers should concentrate on fast rise time, fast recombination time switching materials and switches which can be used in high repetition rate (100�s of kilohertz (kHz) to 1000�s of kHz) applications. Also, the demonstration designs should be able to support 150 Amperes (A) at a potential 1500 volts (V) at a repetition rate of 500 kHz, with improved thermal transfer over present commercial products. Use of R134a refrigerant or other cooling methods are permitted.

DESCRIPTION: Switches are a critical component for the pulsed power systems utilized to produce the high voltages/currents to drive the next generation HPRF production technology or to directly synthesize the HPRF from charged transmission lines. HPRF systems use a wide range of opening and closing switch technologies from traditional spark gap, gas insulated switches to solid state photoconductive switches. The shortfall of many of these switches and switch/media is that they do not support high repetition rate applications, being physics-limited to repetition rate-limited to kHz or 10�s of kHz pulse repetition frequency rates (PRF) when used to power a variety of RF emitters such as a non-linear transmission line or to directly synthesize HPRF when embedded in a transmission line.

The three physics phenomena that drive the switch/media shortfall in repetition rate are the electron/hole recombination time (recovery rate), the resistive losses in the switch, and the thermal transport capabilities/rates of the switch to the surrounding environment for continuous wave (CW) operation. For a demonstration application of the material developed, what is envisioned is a switch that would have a recovery time of less than 0.5 microseconds that could support a variety of HPRF systems and applications and should have picoseconds or less of jitter, when kept at a constant temperature.

A driving factor in the transition of the switches and material is a focus on the ability to manufacture both the material and switches in sufficient quantity for operational use. As the new HPRF systems will push the envelope of increased energy, PRF, and power on-target, the more robust the driving switch technology must become while remaining in a standardized commercial form. The Department of Defense is interested in further developing switch technology capabilities through the study of innovative and novel materials that will not only advance the current state-of-the-art, but also be safer and cheaper to utilize within HPRF systems. The switching mediums of interest include, but are not limited to, solid state materials that are both conventionally or optically triggered (i.e., photoconductive switches utilizing Silicon (Si), Gallium Arsenide (GaAs), Silicon Carbide (4H-SiC), Gallium Nitride (GaN), etc.). The challenge for switch technology development is improved performance in the PRF with jitters of 1 picosecond (ps) or less, for pulse lengths of < 10 nanoseconds (ns), and switch charge times between 10 ns to 100 ns. In addition, repetition rates in the 500 kHz to 1000 kHz regime are required. Threshold standoff voltage should be in excess of 1,500 V with an on current of 150A. It is anticipated that the materials and switches developed under this topic will be, or become, export controlled and ITAR restricted beyond Phase II development. The offeror should anticipate the use of a DD254 in the contract as well as security classification guidance at that point.

PHASE I: In this phase the feasibility of developing semiconductor materials to meet the threshold requirements will be determined along with the development of test material samples required to support further development. One of the candidate designs will be chosen and a more detailed design will be developed. Electromagnetic and circuit modeling and simulation of the switch design should be conducted, and results leading to the final design(s) should be documented and provided in the final report along with a data package on all proposed critical components in the baseline system design. Phase I demonstrations are highly encouraged within available scope under time and funding constraints.

Phase I Design Parameters:
� 1.5 kV switch voltage
� 900 ns or recovery time
� 150 A On Current
� 5 ns pulse lengths
� 10 picoseconds jitter
� 100 ns charge times
� 5 ns rise times
� 1 hour (hr) run time
� 100,000 Hz pulse repetition frequency

The awardees are expected to start the facilities clearance process, if one does not exist, during the Phase I award.

PHASE II: Based upon the Phase I results, design and construct new switching media and test using a brassboard switch and the chosen novel switching medium. The use of actual hardware and empirical data collection is expected for the performance analysis of the switch and switching medium and should be provided in the final report along with a data package on all critical components in the brassboard system. At the completion of Phase II, the prototype switch should be capable of demonstrating the following performance characteristics:

Phase II Design Parameters:
� 1.5 kV switch voltage or greater
� 500 ns or less recovery time
� 150 A On Current
� 10 ns pulse lengths
� 1 picoseconds jitter
� 100 ns charge times
� 1 ns rise times
� 500 kHz pulse repetition frequency
� 1 hr run time
� 500,000 Hz pulse repetition frequency
� packaged in a standard industrial form factor

The Phase II switch prototype must demonstrate a clear path towards addressing the scalability and manufacturability challenges along with packaging the system into a relatively useful volume. At this point, the prototype should be able to demonstrate switch capabilities with minimal secondary system support, even if for a short test cycle. Furthermore, a plan should be developed clearly stating the methodology for future secondary system reduction and scalability for a fully developed switch. All data collected in the analysis of the switch and switching medium of the prototype system will be included in the final report along with a data package on all critical system components. A DD-254 will be included with any Phase II award.

PHASE III: Phase III will consist of an operational demonstration of a fully capable, compact switch meeting the specified switch requirements (detailed below). The final switch will represent a complete solution and should be ruggedized for, at a minimum, testing in a dry, outdoor environment and integrated into an government system of the funding agencies choosing or new system if the government so desires.

The desired potential Phase III design parameters will include previously stated parameters but may require additional advancement to support 2 kV switch voltage or greater with a 8 hour system run time.

All data collected in the analysis of the switch and switching medium of the final system will be included in the final report along with a user�s manual and a data package on all critical system components. The final component report shall be developed with performance specifications satisfying the targeted acquisition program requirements coordinated with technical point of contact. A preliminary design package and plan outlining the use of the switch in commercial switching applications should also be submitted with the final report.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: HPRF sources, and consequently switches, are used in a wide variety of commercial applications including the electric power industry, semiconductor processing, x-ray machines, pulsed power, and medical applications. These applications should be identified as a part of the Phase I and II proposal and a transition plan developed to use the material and devices in the commercial industry.

REFERENCES:
1. Morton, D.; Banister, J.; Levine, J.; Naff, T.; Smith, I.; Sze, H.; Warren, T.; Giri, D. V.; Mora, C.; Pavlinko, J.; Schleher, J.; Baum, C.E., "A 2MV, <300ps risetime, 100Hz pulser for generation of microwaves," Power Modulator and High Voltage Conference (IPMHVC), 2010 IEEE International, pp. 361,364, 23-27 May 2010.

2. Lehr, J.M.; Abdalla, M.D.; Burger, J.W.; Elizondo, J.M.; Fockler, J.; Gruner, F.; Skipper, M.C.; Smith, I.D.; Prather, W.D., "Design and development of a 1 MV, compact, self break switch for high repetition rate operation," Pulsed Power Conference, 1999. Digest of Technical Papers. 12th IEEE International, vol. 2, pp. 1199, 1202 vol. 2, 27-30 June 1999.

3. Corley, J. P.; Hodge, K. C.; Drennan, S. A.; Guthrie, D. W.; Navarro, J. M.; Johnson, D.L.; Lehr, J.M.; Rosenthal, S. E.; Elizondo, J.M., "Development/tests of 6-MV triggered gas switches at SNL," Pulsed Power Conference, 2003. Digest of Technical Papers. PPC-2003. 14th IEEE International, vol. 2, pp. 875, 878 Vol. 2, 15-18 June 2003.

4. Gilman, Charles; Lam, S. K.; Naff, J.T.; Klatt, M.; Nielsen, K., "Design and performance of the FEMP-2000: a fast risetime, 2 MV EMP pulser," Pulsed Power Conference, 1999. Digest of Technical Papers. 12th IEEE International, vol. 2, pp. 1437,1440, vol. 2, 27-30 June 1999.

5. John Maenchen, Jane Lehr, Larry K. Warne, et. al, "Fundamental Science Investigations to Develop a 6-MV Laser Triggered Gas Switch for ZR: First Annual Report" Sandia National Laboratories, March 2007, http://www.sandia.gov/pulsedpower/prog_cap/pub_papers/070217.pdf

6. Rohwein, G.J., "A Three Megavolt Transformer for PFL Pulse Charging," IEEE Transactions on Nuclear Science, vol. 26, no. 3, pp. 4211, 4213, June 1979.

7. Bailey, V.; Carboni, V.; Eichenberger, C.; Naff, T.; Smith, I.; Warren, T.; Whitney, B.; Giri, D.; Belt, D.; Brown, D.; Mazuc, A.; Seale, T., "A 6-MV Pulser to Drive Horizontally Polarized EMP Simulators," IEEE Transactions on Plasma Science, vol. 38, no. 10, pp.2554, 2558, Oct. 2010.

8. Belt, D.; Mazuc, A.; Sebacher, K.; Bailey, V.; Carboni, V.; Eichenberger, C.; Naff, T.; Smith, I.; Warren, T.; Whitney, B., "Operational performance of the Horizontal Fast Rise EMP pulser at the Patuxent River EMP test facility," Pulsed Power Conference (PPC), 2011 IEEE, pp. 551, 554, 19-23 June 2011.

9. Carboni, V.; Lackner, H.; Giri, D.; Lehr, J., "The breakdown fields and rise times of select gases under the conditions of fast charging (20 ns and less) and high pressures (20-100 atmospheres)," Pulsed Power Plasma Science, 2001. PPPS-2001. Digest of Technical Papers, vol. 1, pp. 482, 486 vol. 1, 17-22 June 2001.

10. James, C.; Hettler, C.; Dickens, J., "Design and Evaluation of a Compact Silicon Carbide Photoconductive Semiconductor Switch," IEEE Transactions on Electron Devices, Vol. 58, Issue 2, 2011.

11. Pocha, M.D.; Druce, R.L., "35-kV GaAs subnanosecond photoconductive switches," Electron Devices, IEEE Transactions on Electron Devices, Vol. 37 , Issue: 12 , Part: 2, 1990.

12. Karabegovic, A.; OConnell, Robert M.; Nunnally, W.C. "Photoconductive switch design for microwave applications," IEEE Transactions on Dielectrics and Electrical Insulation, Volume: 16, Issue: 4, 2009.

13. Zutavern, F.J.; Glover, S.F.; Mar, A.; Cich, M.J.; Loubriel, G.M.; Swalby, M.E.; Collins, R.T.; Greives, K.H.; Keator, N.D., "High current, multi-filament photoconductive semiconductor switching," IEEE Pulsed Power Conference (PPC), 2011.

KEYWORDS: High power radio frequency; high power microwave; dielectrics; closing switches; opening switches; spark gap; semiconductor solid state switches; photoconductive switches

** TOPIC AUTHOR (TPOC) **

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