Progress toward steady-state high-efficiency vircators
Conference
·
· Proceedings of SPIE - The International Society for Optical Engineering
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
The resonance at which high-efficiency operation of virtual cathode oscillators is obtained occurs when the beam frequency equals the reflex frequency to within 2%. This tolerance limit in the frequency ratio implies that cathode closure in the anode-cathode gap is not acceptable. We have developed and tested a 6-cm2 cathode that will operate longer than 1 μs at 300 A/cm2 without significant closure. As yet, the full-scale (>80-cm2) cathode has not worked quite as well. In many tests, the cathode will operate in the emission-limited temperature/field (T/F) mode for approximately 300 ns, and then transition into explosive emission with a relatively slow (~0.5 cm/μs) closure rate. The current density was 45 to 90 A/cm2. We have not run high-power rf-emission tests under conditions where the diode stays open and in resonance for the duration of the rf pulse at a current density of 250 A/cm2, which is required for 3-GHz operation; that test remains the focus of our continuing research. We have obtained long (600-ns) duration rf pulses at low power. We have also extended the data base on micro wave generation at lower power and have shown that high-efficiency resonances will occur when a multiple of the reflex frequency equals the beam frequency. This allows greater flexibility in the design and scaling of the microwave device.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 6186396
- Report Number(s):
- UCRL-JC--105613; CONF-910123--11; ON: DE91008064
- Conference Information:
- Journal Name: Proceedings of SPIE - The International Society for Optical Engineering Journal Volume: 1407
- Country of Publication:
- United States
- Language:
- English
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