Download Gyroklystron Research at CCR

Gyroklystron Research at CCR
Lawrence Ives, Michael Read, Jeff Neilson, Philipp
Borchard and Max Mizuhara
Calabazas Creek Research, Inc.
20937 Comer Drive, Saratoga, CA 95070-3753
W. Lawson
IREAP, University of Maryland
College Park, Maryland
[email protected]
Acknowledgement
• Work supported by the US Department of Energy contracts
DE-FG02-04ER83917, DE-FG02-06ER84454, and DEFG03-99ER82754
Gyroklystron Designs
• 91.392 GHz, 10 MW - Available for testing
• 30 GHz, 30 MW gyroklystron – Phase I design completed
spring 2005. Phase II program not funded
• 30 GHz, 50 MW gyroklystron – Phase I design completed
spring 2007. No Phase II proposal submitted
Gyroklystron design goals
Pulse power
25/50 MW
Gain
~ 50 dB
Pulse width
~ 1 microsecond
Frequency
30 GHz
Voltage
≤ 500 kV
50 MW Design Parameters
Designs at fundamental and second harmonic
Parameter
Fundamental
Second
harmonic
Peak Efficiency (%)
Large signal gain (dB)
48.189
53.8
37.11
46.1
Output Power (MW)
Input Power (kW)
Drive frequency (kHz)
72.28
0.3
30.051
37.11
0.92
15.008
Beam guiding radius (cm)
1.0
0.5
Beam Voltage (kV)
Beam Current (A)
Average velocity ratio
500
300
1.5
500
200
1.5
6
5
30.000
12.56
.78
1.22
15.000
16.58
NA
0.97
Axial velocity spread (%)
Drive cavity f (GHz)
Tube length (cm)
Drift tube ID (cm)
Drift tube OD (cm)
Electron Gun for Fundamental Mode
296 A @ 500 kV
Inverted MIG
R (cm)
Cathode
anode
mod anode
(-10 kV - + 10 kV)
inner conductor
Z (cm)
Electron Gun for Second Harmonic
R (cm)
Z (cm)
140 A @ 500 kV
Space Charge Limited
Input coupler
cavity
input guide
Second Harmonic Cavity
1.8
1.7
Radius (cm) / Field (T)
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0
2
4
6
8
10
12
Axial distance (cm)
14
16
18
20
Output Guide for Second Harmonic
TE01 Input, 99.9% TE01 Output
Challenges and Goals for Coaxial
Gyroklystron
• Investigate alternative gun designs with improved
performance
• Utilize coaxial inserted supported at both ends for
precisions alignment
• Investigate circuit designs with high efficiency
• Develop output coupler consistent with coax conductor
Fundamental Mode Cavity
1.8
Radius (cm) / Field (T)
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0
3
6
9
12
Axial distance (cm)
15
18
RF Structure
cavities
cavities
inner conductor
25 MW RF Structure Summary
•
•
•
•
•
•
•
•
Number of cavities:
Cavity mode
Magnetic field
Q (all but output cavity)
Q (output cavity)
Stability
Efficiency
Gain
5
TE01
~1.43 Tesla (fundamental)
200
240
zero-drive stable for all modes
54% at 33 MW
60 dB for η=54%
Bandwidth
0.25%
1. 5
Output
window
m
Collector
Output coupler
Input coupler
Inverted MIG
Input and Output couplers
• Wrap-around coupler used for the input
• Output coupling through the inner conductor is simpler and
gives desired TE01 output mode
Input Coupler
cavity
input guide
Output coupler
outer
conductor
inner
conductor
output cavity
connecting pins
Output cavity RF Electric Field
Inner
conductor
Inner conductor of
coax output
waveguide
Maximum RF
electric field is
23 MV/m
Output coupler RF electric field
Output window
• TE01 mode
• Traveling wave design used to minimize fields at ceramic
Fundamental Mode Collector
•
•
Peak power is
limiting factor
Final design has
peak temperature
of 240 °C
Collector for Second Harmonic
1 10
Temperature Rise (K)
3
100
10
1
0.1
3
1 10
1 10
4
1 10
Heat Flux (W/cm2)
5
1 10
6
Thermal Issues
• Average power of 8 kW average power does not pose a
significant problem with cooling center conductor from
gun and collector end
• Pulse heating in output cavity and collector motivated
careful design, but all peak temperatures and temperature
rises are within engineering limits
Superconducting Magnet
Magnet is
procured and
available
W-Band
Gyroklystron
Lawrence Ives, M. Read, J. Neilson,
M. Mizuhara,
T. Robinson and D. Marsden
Calabazas Creek Research, Inc.
W. Lawson and B. Hogan
Institute for Plasma Research,
University of Maryland
Funded by SBIR grant DOE DEFG03-99ER82754
Specifications
Parameter
Goal
Frequency
91.386 GHz
Design Output Power
10 MW
Efficiency
37%
Gain
56 dB
Pulse length
~ 1 microsec
Duty cycle
~ 0.001
Operating mode
TE01 or TE02
Output mode
TE01/02 Composite
Operating Voltage
500 kV
Operating Current
50 A
Gyroklystron Circuit
Fundamental
TE01
TE01/02
Mode
Converter
6
Radial location (mm)
5
4
3
2
2nd Harmonic TE02
1
0
0
20
40
60
Axial location (mm)
80
100
120
MAGYKLY2000 Calculation Using Measured
Cavity F and Q
•
•
•
•
•
Output frequency (GHz)
Drive power (W)
Electronic efficiency (%)
Output power (MW)
Gain (dB)
91.386
23
36
10
56
Availability
• The gyroklystron is
fully assembled, baked,
and ready for operation
• Superconducting
magnet with power
supplies are in
inventory
• Two RF driver TWTs
are in stock
Summary
• 91 GHz gyroklystron is completed and available for testing
• 30 GHz designs generated at 25 and 50 MW – tubes can be
build if funding provided