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/cm 2 demonstrated with 5 μs pulses at a 500 Hz repetition rate at 1000 ˚C—200 A/cm 2 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 TM 020 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. 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 RF Breakdown Simulations * 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