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Vacuum Electronics Research at The University of Michigan. Profs. Ron Gilgenbach, Y.Y. Lau and Mary Brake Nuclear Engineering & Radiological Sciences Dept. University of Michigan Ann Arbor, MI 48109-2104 funded by the AFOSR. OUTLINE. motivation research topics recent results

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Vacuum electronics research at the university of michigan l.jpg

Vacuum Electronics Research at The University of Michigan

Profs. Ron Gilgenbach, Y.Y. Lau and Mary Brake

Nuclear Engineering & Radiological Sciences Dept.

University of Michigan

Ann Arbor, MI 48109-2104

funded by the AFOSR


Outline l.jpg
OUTLINE

  • motivation

  • research topics

  • recent results

  • future planned research


U michigan research topics l.jpg
U. Michigan Research Topics

  • initial studies have begun on a small scale (expanded program begins Jan. 1, 2000)

  • crossed field devices: noise and mode stability experiments

  • theoretical research on intermodulation and noise in microwave tubes

  • microwave plasma cleaning/ processing of tubes


Motivation crossed field amplifier applications in dod systems 96 97 l.jpg
Motivation: Crossed Field Amplifier Applications in DoD Systems (96-97)

  • System CFA Tube

  • AEGIS SFD-261/262 and L-4707/4708

  • PATRIOT L-4927A

  • TPS-32 L-4829

  • TPS-63 VXL-1169, L-4806

  • APS-116 SFD-251, L-4764

  • APS-137 L-4764A

  • MK-92 SFD-233G, L-4810

  • SPS-48C SFD-267, L-4717, VXS-1247/1247F, L-4716/4718

  • SPS-48E L-4719

  • HAWK-PAR L-4939/4940

  • ARSR-1&2 L-4953

  • AEGIS (Israel) L-4891

  • HADR (Ger., Nor.) L-4756

  • FLORIDA (Swit.) L-4822

  • E2-C L-4934

  • TPN-19/GPN-22 L-4764

  • AR-320 (UK) L-4756A

  • APS-145 VXL-1910 (in development)


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magnetron experiments

  • beginning with oven magnetrons (most efficient sources known); e.g. Toshiba 2M229, 700-900 W @ 4kV, 0.3A

  • investigate noise and out-of-band mode generation (source of EM pollution)

  • investigate mode hopping in startup- regime

  • explore the existence of “quiet-states” (W.C. Brown, 1988 Raytheon Tech. Rep.)


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magnetron experiments (continued)

  • utilize time-frequency-analysis to examine the spectrum of magnetrons

  • investigate the connection of noise to “excess” cathode emission current

  • modeling of magnetron by Phillips Lab Scientists (Luginsland and Spencer)


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Microwave-tube related theory efforts at U of Michigan

  • 1) Intermodulation in klystrons and in TWTs (Work in progress)

  • 2) Low frequency emission noise from thermionic cathodes (scaling law synthesized for flicker noise power relative to shot noise power)

  • 3) Low frequency ion noise in linear beam tubes (many observed features, such as sensitivity to B-field, to cathode voltages, etc., explained by simple theory.) Methods to reduce this low frequency phase noise proposed.


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theoretical research (continued)

  • 4. Time-frequency analysis: Novel technique studied for reduction of interference in time-frequency analysis of tubes that display mode competition.

  • 5. Crossed-field-device output characterization: Time frequency analysis being applied to various crossed-field device output, from microwave oven magnetron to CFA's. Noise in crossed-field geometry continues to be investigated.

  • 6. Cathode processes: Processes that affect cathode life and cathode noise (e.g., changes in emission due to evaporation and ion backbombardment) being analyzed.


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MICROWAVE PLASMA DISCHARGE CLEANING

  • can clean from the inside of tube

  • can match microwave frequency to tube type

  • no electrode impurities added to system

  • remote cleaning & cleans non-symmetric parts

  • - high density processing plasma (> 10E12- 10e14 /cc) Vs. RF plasmas (~10E9 - 10E10 or ICP =10E12)

  • in principle, no limitation to plasma column length, depends upon the power capability

  • inexpensive sources of 1 kW power at 2.45 GHz


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SURFACE WAVE EXCITED PLASMAS

  • Electromagnetic surface waves can sustain long plasma columns

  • wave is excited at one end of a long tube containing a gas (~1 Torr to 750 Torr)

  • EM wave travels along a plasma column it sustains (from the power that is carried by the wave) and these media constitute the wave's sole propagating structure


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INITIAL MICROWAVE PLASMA CLEANING STUDIES

  • Microwave resonant cavity

  • Fixed cavity inside diameter of 17.8 cm

  • Sliding short adjusts the length of the cavity to obtain specific electromagnetic modes (14.5 cm to ~9.5 cm

  • Tuning stub , which applies the microwave power to the cavity, is placed very close to the glass tube containing the gas/ plasma


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LOW FREQUENCY ION NOISE IN TWT*

Professor Y.Y. Lau

Nuclear Engineering & Radiological Sciences Dept.

University of Michigan

Ann Arbor, MI 48109-2104

*In collaboration with Dave Chernin and Wally Manheimer during sabbatical

in 1999


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A Comparison of Flicker Noise and Shot Noise on a Hot Cathode*

Professor Y.Y. Lau

Nuclear Engineering & Radiological Sciences Dept.

University of Michigan

Ann Arbor, MI 48109-2104

*In collaboration with K. Jenson and B. Levush during sabbatical in 1999


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CONCLUSIONS Cathode

  • The University of Michigan will contribute to the MURI-1999 Program in:

  • crossed-field device science

  • intermodulation and noise

  • tube processing techniques

  • time-frequency signal analysis


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