1. 48th Annual Meeting of the Division of Plasma Physics, October 30 – November 3, 2006, Philadelphia, Pennsylvania Waveguide Cut c ab =0.99 w/a = 0.64 Gyrotron test mode 24-96 kW  T calibrated with cartridge heater ECRH power deposition profiles Electron thermal diffusivity,  e Heatwave & heat pulse propagation Summary 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; 1 Affiliation of Collaborators Thermal Beam Imaging Hybrid Qausioptical Line #2 Single-iteration CMM alignment Thermal camera + Macor ® ceramic target Temperature profile ~ microwave power profile Analysis includes thermal conduction in target 28 GHz Varian (CPI) Gyrotron TE 02 main output mode 200 kW (peak), 200 ms (max) Microwave Source: Oversized Waveguide 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: TE 02 -to-TEM 00 –Quasioptical units: beam direction and focus –Dual-mode (TE 11 +TM 11 ) 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 Overview Modulated ECRH Gaussian Beam Propagation Smooth-Walled (Dual-Mode) Waveguide Traverse long distances Eliminate quasioptical mirror size/quantity trade-off Low loss (<< 1%) Superposition TE 11, TM 11 Efficient coupling to Gaussian beam modes B =0.83 Quasioptical Calorimeter Thermal image at mirror surface Image indicates gyrotron output Reduced TE 02 power for suboptimal tuning Optimal tuning required for optimized waveguide operation Gyrotron Tuning Suboptimal Tuning Optimal Tuning Focus beam & correct astigmatism Simplify waveguide bends Utilize quasioptical design techniques Ellipsoidal Mirrors Vlasov Converter Vlasov converter: stepwise cut + parabolic reflector Inherent higher-order mode filtering Waveguide cut = L B, bounce length TE 02 -to astigmatic beam c a =0.94 w 0 /2a=0.505 Coupling Coefficients Gaussian power profile w 0 ~ 2.0 cm Beam offset < 5mm Gaussian power profile w 0 ~ 3.25 cm Beam offset < 5mm Dual-mode Waveguide EntranceCorrugated Waveguide Entrance Polarization Twist Reflector Rotate beam polarization O-mode: E || B 0 X-mode: E  B 0 Low cross-polarization, i cross X-mode (-61.2º)  1 = 67.3° d = 0.1408” i cross < -25 dB O-mode (28.8º)  1 = -79.7° d = 0.1473” i cross < -30 dB Old Transmission Line: TE 02 -to-TE 01 -to-TE 11 -to-HE 11 50 kW (nominal), 50ms (nominal) Power limited by waveguide arcing Line removed Feb, 2006 HSX To Gyrotron 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 (TE 11 +TM 11 ) 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 Quasioptical design Water load calorimeter Calorimeter/dummy load operation Full-power/test-pulse gyrotron operation Input aperture matches corrugated waveguide input Future Work c a =0.97 w 0 /4F=0.470 End View Side View 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 d Integrated directional coupler Low loss (<1% per mirror) CNC machined aluminum Multiple of TE 11, TM 11 guided wavelength 2.5” ID:  L = 0.065 m 4.0” ID:  L = 1.676 m Parabolic Reflector 4 1 3 2 5 9 7 8 95 7 4 3 2 1 2 TE 02 -TEM 00 Mode Converter HSX Quasioptical Switch 6 6 TE 02 TEM 00 Infrared camera Thermal target Target markers Target marker Spherical expanding mirror (R=20.0”) 3/8” I.D. Teflon ® tubing 8 2.5” I.D. 24.75” ” ” ” ” ”