Transcript theoretical research

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
University of Michigan
OUTLINE
motivation
 research topics
 recent results
 future planned research
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University of Michigan
U. Michigan Research Topics
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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
University of Michigan
Motivation: Crossed Field Amplifier
Applications in DoD Systems (96-97)
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University of Michigan
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)
magnetron experiments
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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.)
University of Michigan
magnetron experiments
(continued)
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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)
University of Michigan
Microwave-tube related theory
efforts at U of Michigan
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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 Bfield, to cathode voltages, etc., explained by
simple theory.) Methods to reduce this low
frequency phase noise proposed.
University of Michigan
theoretical research (continued)
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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 crossedfield 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.
University of Michigan
MICROWAVE PLASMA
DISCHARGE CLEANING
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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
University of Michigan
SURFACE WAVE EXCITED PLASMAS
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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
University of Michigan
INITIAL MICROWAVE PLASMA CLEANING STUDIES
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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
University of Michigan
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
University of Michigan
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
University of Michigan
CONCLUSIONS
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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University of Michigan