Transcript Advanced Magnetron Injection Guns for Coaxial Gyrotrons

A 350 MHz, 200 kW CW,
Multiple Beam IOT
Lawrence Ives, Michael Read, David Marsden,
R. H. Jackson, Thuc Bui
Calabazas Creek Research, Saratoga, CA. USA
Takuji Kimura, Edward Eisen
Communications & Power Industries, LLC.
This research is supported by U.S. Department of
Energy Grant DE-FG-3-07ER84876, the Naval Surface Weapons Center, and
Communications & Power Industries, LLC.
Goals of the Research
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Frequency
Bandwidth
Output Power
Gain
Operating Voltage
Efficiency
Total Current
Number of beams
Average Current per beam
352 MHz
4 MHz
200 kW CW
23 dB
30 kV
70%
9.5 A
7
1.4 A
Design Approach and Challenges
Approach
• Utilize existing production electron gun
• Arrange guns in circular pattern driving a
fundamental mode output cavity
• Choose number of beams based on gun operation
(30 kV operation) – Seven beams selected
Challenges
• Input cavity free of parasitic modes
Electron Guns
Solid Model
Input Waveguide
Input Cavity
Output Cavity
Collector
Output Window
Electron Gun
• Uses existing
production IOT
electron gun
• Reduced cost and risk
Electron Gun
• Model for peak current = 5.6 A = 4 x average (normal ratio for IOT)
• Grid voltage = 0 V
• 2D Model Using TRAK
Grid Detail
• Grid Voltage = 0
• I = 5.6 A (max)
• Grid reduces current
below that without a grid,
keeping the grid
interception to ~ 0
Magnetics
• Brillouin focusing with uniform solenoid
– Field set near value appropriate for max current
• 3D Modeling required
– Used OmniTRAK
Input Cavity
Primary challenge for MBIOT design
• Must drive multiple beams in parallel
• Avoid exciting parasitic modes
• Provide required coupling to input waveguide
RF Input
Tuners
Dielectric
break
Cathode
heater leads
Input Waveguide Transition
Input cavity is not in vacuum, so no vacuum window is required for RF input
Input Circuit
HFSS Model
Cavity
Input Waveguide
Electron Guns
CASCADE optimized
Step transducer
-30 dB
HFSS
simulation
345.5
HFSS Analysis of Input Cavity
Bandwidth Analysis
-10 db
-20 db
-30 db
348.2 MHz
Output Cavity
Beam Tunnels
Output Coupler
Output Cavity Field Plots
Output Cavity Fabrication
Output Window
Water cooling
Ceramic
Collector
Tailpipe
Collector
Output coupler
Output Window
Collector Simulations
Collector Thermal Analysis
Collector and Window Assembly
Solenoid and Driver
1.5 kW CW at 350 MHz
Summary
• 350 MHz 200 kW CW multiple beam IOT design complete
• Assembly is 95% completed
• Seeking additional funding to complete and test the tube
MBIOT Status
MBIOT is ~ 95 % complete. Remaining tasks include:
• Rebuild output window
• Cold test output cavity and machine as required
• Braze end plates to output cavity cylinder (only remaining braze)
• Weld electron guns to support plate and connect heater leads
• Weld input cavity to high voltage ceramic and gun support plate
• Weld collector, output window, and input cavity/gun assembly
Estimate cost to complete - $50,000