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Ryan Umstattd Naval Postgraduate School Presented at the MURI 2004 Kick-Off

Western Consortium on the NanoPhysics of Electron Dynamics near Surfaces in High Power Microwave Devices and Systems. Ryan Umstattd Naval Postgraduate School Presented at the MURI 2004 Kick-Off at the Baltimore ICOPS, 28 June 2004. Western Consortium Team Members.

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Ryan Umstattd Naval Postgraduate School Presented at the MURI 2004 Kick-Off

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  1. Western Consortium on the NanoPhysics of Electron Dynamics near Surfaces in High Power Microwave Devices and Systems Ryan Umstattd Naval Postgraduate School Presented at the MURI 2004 Kick-Off at the Baltimore ICOPS, 28 June 2004

  2. Western Consortium Team Members • UC Davis: N.C. Luhmann, Jr., J. P. Heritage, C.W. Domier, K.Liu • Stanford: G. Caryotakis, L. Laurent, G. Scheitrum • Naval Postgraduate School: R. Umstattd • Collaborators: G. S. Park: SNU • P. Li: BVERI • M. Gundersen: USC

  3. Original Timeline

  4. Some program highlights… • Thermionic cathodes -Oxide -Scandate* • Field emitter arrays • Explosive emission cathodes & guns • RF breakdown experiments & simulations *70 A/cm2 demonstrated with 5 μs pulses at a 500 Hz repetition rate at 1000 ˚C—200 A/cm2 appears achievable for HPM applications.

  5. Thermionics • Plasma deposition of cathodes • Performed at Stanford facility in collaboration w/ BVERI colleagues • Vast improvements in system since original use for oxide cathode deposition • Focus: Long life cathodes for conventional microwave tubes and high current density “clean” cathodes for HPM sources • Goal: Cathodes with work functions in the target range of 1.4-1.6 eV

  6. Field Emitters • Si tips • UCD • CNT emitters • UCD/LLNL • Photo-gated arrays • UCD • Active control • NPS/USC

  7. Explosive Emitters • Carbon microfiber in Pierce gun • Long pulse testing  commercial applications • Short pulse testing  compact pulsed power • Hollow cathodes • High Brightness • High Energy

  8. RF Breakdown Experiments • TM020 cavity with removable noses • Examine materials and processing • Copper surface before (left) and after (right) Gas Cluster Ion Beam (GCIB) Processing (collaboration with Epion)

  9. RF Breakdown Simulations • Comparison between measured experimental data (left) and 3D PIC simulations (right) using a 4x4 mm emitting spot, an electron current of 7 kA, and a copper ion current of 30 A*. • Macroscopic versus microscopic models * V. Dolgashev and S. Tantawi

  10. Conclusion • Lots of exciting efforts ahead of us! • Look forward to working with you all… • Upcoming cathode conferences: • International Vacuum Nanoelectronics Conference (IVNC) @ MIT, July 11-16 • International Vacuum Electron Sources Conference (IVESC) in Beijing, Sept 6-10

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