Transcript The HSX Hybrid Quasioptical Waveguide System

The HSX Hybrid Quasioptical Waveguide System
J. W. Radder, K. M. Likin, F. S. B. Anderson, D. T. Anderson, J. N. Talmadge
HSX Plasma Laboratory, Univ. of Wisconsin, Madison, USA; 1Affiliation of Collaborators
Overview
•
•
•
5
Ellipsoidal Mirrors
6
4
2
8
3
3/8” I.D. Teflon® tubing
HSX
7
Spherical expanding mirror
(R=20.0”)
9
TE02-TEM00
Mode Converter
3
Quasioptical Switch
Coupling Coefficients
• Inherent higher-order mode filtering
• Waveguide cut = LB, bounce length
• TE02-to astigmatic beam
 E u f udu
 f u f udu
Dual-mode Waveguide Entrance
Gyrotron Tuning
Corrugated Waveguide Entrance
*
ca 
Waveguide Cut
*
5
0.5
9
a  1.25"

 587m 1
Side View
 
 B  sin1 0,2  22o
 k 
m
rc 
0
Microwave Source:
•28 GHz Varian (CPI) Gyrotron
•TE02 main output mode
•200 kW (peak), 200 ms (max)
1
LB  2
2
 rc2 cot B   6.15"
2F  rc   sin  
1 cos
2F

1 cos
Old Transmission Line:
Target marker
Target markers
ca=0.94
w0/2a=0.505
ca=0.97
w0/4F=0.470
Hybrid Qausioptical Line #2
• 2nd 200 kW, 28 GHz CPI gyrotron
• Steerable launching mirror
• 0.5 T X-mode 2nd harmonic heating
• 1 T O-mode fundamental heating
• Installation in 2007
Infrared
• Single-iteration CMM alignment
camera
•Thermal camera + Macor® ceramic target
• Temperature profile ~ microwave power profile
• Analysis includes thermal conduction in target
Polarization Twist Reflector

4
Gaussian Beam Propagation
r 2

 2 0.5
jr 2
E(r,z)   2  exp 2  jkz 
 j0 
w 
R
w

 1
M lens  
1/ f
0

1
1
M L  
0
L

1

B 1
 
D 0
dout   1
 
1
  1/ f
0 1
 
1 0
• Rotate beam polarization
• O-mode: E || B0
• X-mode: E ^B0
• Low cross-polarization, icross
O-mode (28.8º) X-mode (-61.2º)
1 = 67.3°
1 = -79.7°
d = 0.1408”
d = 0.1473”
icross< -30 dB icross< -25 dB
”
”
”
din 

1 
”
”
Smooth-Walled (Dual-Mode) Waveguide
• Traverse long distances
• Eliminate quasioptical mirror
size/quantity trade-off
• Low loss (<< 1%)
• Superposition TE11, TM11
• Efficient coupling to
Gaussian beam modes
• Multiple of TE11, TM11
guided wavelength
• 2.5” ID: DL = 0.065 m
• 4.0” ID: DL = 1.676 m
Modulated ECRH
• ECRH power deposition profiles
• Electron thermal diffusivity, e
• Heatwave & heat pulse propagation
Summary
HSX
To Gyrotron
Optimal Tuning
Future Work
• Gaussian power profile
• w0 ~ 2.0 cm
• Beam offset < 5mm
• Gaussian power profile
• w0 ~ 3.25 cm
• Beam offset < 5mm
Thermal target
d
2
• Thermal image at mirror surface
• Image indicates gyrotron output
• Reduced TE02 power for
suboptimal tuning
• Optimal tuning required for
optimized waveguide operation
Suboptimal Tuning
End View
Parabolic Reflector

TEM00
a

d
 0,2
A
M  
C
• Quasioptical design
• Water load calorimeter
• Integrated directional coupler • Calorimeter/dummy load operation
• Low loss (<1% per mirror)
• Full-power/test-pulse gyrotron operation
• CNC machined aluminum
• Input aperture matches corrugated waveguide input
Thermal Beam Imaging
• Vlasov converter: stepwise cut + parabolic reflector
Oversized Waveguide
• Line removed Feb, 2006
7
• Focus beam & correct astigmatism
• Simplify waveguide bends
• Utilize quasioptical design techniques
Vlasov Converter
2
8
• Gyrotron test mode 24-96 kW
• DT calibrated with cartridge heater
2.5” I.D.
1
k
• TE02-to-TE01-to-TE11-to-HE11
• 50 kW (nominal), 50ms (nominal)
• Power limited by waveguide arcing
24.75”
2
ECRH Transmission Line Upgrade
– ECRH power previously limited by waveguide arcing
– Oversized, mode-converting waveguide removed
– Hybrid quasioptical line installed
– Waveguide ECRH operation since July, 2006
Hybrid Quasioptical Design
– Vlasov mode converter: TE02-to-TEM00
– Quasioptical units: beam direction and focus
– Dual-mode (TE11+TM11) waveguide connects quasoptical
units
Beam Analysis
– Launched power measured with a quasioptical water load
calorimeter
– Microwave beam patterns measured with a thermal
camera and ceramic target
TE02
Quasioptical Calorimeter
6
•
•
•
ETE11  ETM 11
1 
cab=0.99
w/a = 0.64
B =0.83

•
•
Over-sized, mode converting waveguide was replaced with a
hybrid quasioptical waveguide.
Quasioptical design was utilized for mode conversion,
astigma correction and beam bends.
A dual-mode (TE11+TM11) waveguide eliminates mirror
size/quantity trade-off in a quasioptical system.
Measured microwave beam profiles exhibit excellent
agreement with predicted profiles.
Waveguide tested for X- and O-mode 100kW ECRH
• Effective plasma heating, improved plasma stored energy
48th Annual Meeting of the Division of Plasma Physics, October 30 – November 3, 2006, Philadelphia, Pennsylvania