Progress in Development of Multi-Frequency High-Power Gyrotron 29aP69 池⽥亮介,⼩⽥靖久,⼩林貴之,梶原健,⾼橋幸司,森⼭伸⼀,坂本慶司 0 20 40 60 80 100 -3 -2 -1 0 1 2 3 100 120 140 160 180 200 TE 31,11 gyrotron TE 31,8 gyrotron Power reflection rate [%] rad [deg.] Oscillation frequency [GHz] 19,7 22,8 25,9 28,10 31,11 34,12 37,13 4 /2 5/2 6 /2 3/2 18,5 35,9 31,8 27,7 36,9 22,6 Design parameters of JA ITER gyrotron ITER gyrotron at QST ITER gyrotron of TE 31,8 mode had already achieved 1.0 MW CW operation with total efficiency of 55%. Higher order mode of TE 31,11 has been selected to enhance the output power and to realize multi-frequency oscillations. Mode TE 31,8 TE 31,11 Cavity radius R c = 17.90 mm 20.87 mm Triode MIG R e = 46.5 mm Same Beam radius R b = 9.13 mm Same Diamond window D w = 82 mm t w = 1.853 mm Same Remark 1MW/55%/800s 0.8MW/57%/1hr Up to 1.4 MW Multi-frequency Design for multi-frequency oscillation by ITER type gyrotron Oscillation frequency 104GHz 137GHz 170 GHz 203 GHz Cavity Field 4.08 T 5.32 T 6.63 T 7.98 T Gun Field 0.172 T 0.21 T 0.28 T 0.31 T Beam radius 9.25 mm 9.19 mm 9.13 mm 9.10 mm Anode-cathode voltage 28 kV 36k V 42 kV 50 kV Pitch factor 1.32 1.35 1.35 1.35 Oscillation power 1.12 MW 1.26 MW 1.3 MW 1.3 MW Oscillation efficiency 39% 44% 45% 45% Oscillation frequency (Cavity mode number) Transmission efficiency between radiator to window 104GHz (TE19,7) 95.5% 137GHz (TE25,9) 96.9% 170 GHz (TE31,11) 98.5% 203 GHz (TE37,13) 97.6% (Radiator design was optimized for170 GHz beam.) 0 10 20 30 40 50 60 70 80 0 10 20 30 40 Water temp. increase at DCB absorber [deg.C] Time [s] 170GHz (1MW) 137GHz (1MW) 104GHz (0.9MW) Water flow : 8 L/min DCB absorber 43 kW 29 kW 16 kW 0 10 20 30 40 0 10 20 30 40 Water temp. increase at relief window load [deg.C] Time [s] 170GHz (1MW) 137GHz (1MW) 104GHz (0.9MW) Water flow : 7 L/min Relief window load 8 kW 14 kW 21 kW Boiling! Oscillation efficiencies at the cavity for sub-frequencies were close to one at main designed 170GHz oscillation. Low frequency oscillations are limited due to water temperature at RF absorber. Modification of the radiator design is underway to realize longer pulse 1MW operation (> 30s) at 104 GHz and to apply the low field experiments (1.8 T) in ITER. Calculated transmission efficiency from radiator to window is 96.6 %. Cavity heat load reaches 2kW/cm 2 at 1 MW cavity power . If the internal loss is ~10 % (203GHz), output power is up to 0.9 MW. Power balance in gyrotron for quad-frequency oscillations 104 GHz 137 GHz 170 GHz 203 GHz DCB [%] 6.1 3.9 2.3 2.6 Relief window [%] 2.3 1.4 0.8 0.9 viewing ports [%] 0.6 0.3 0.1 0.1 Diffraction loss [%] 8.9 5.6 3.3 3.7 Mirrors [%] 0.9 0.7 0.7 0.6 Radiator [%] 2.0 1.8 1.8 1.7 Cavity [%] 2.8 3.0 3.4 3.8 Ohmic loss [%] 5.7 5.4 5.8 6.1 Total internal loss [%] 14.6 11.1 9.1 9.7 Output eff. [%] 24.0 26.5 28.0 25.0 Cavity eff. [%] 27.5 29.4 30.5 27.4 x3 x2 JA ITER gyrotron is capable of multi-frequency oscillations with uniform directional beam. 1.2MW power and ~ 50% efficiency have been demonstrated. Steady-state operation at 1MW was achieved (All coolant temperature was saturated). 1MW-level oscillations of 104 GHz for 5s and 137 GHz for 6s were obtained. 203GHz oscillation has been demonstrated. Long pulse operation : 0.4 MW for 5s (The world’s first) Achieved maximum power : 0.9 MW/0.3ms Experimental results of long pulse operations for 170 GHz and multi--frequency oscillations If higher order mode TE 49,17 mode in same mode-group is selected for 236 GHz oscillation, the oscillation power increases up to 1.35 MW (Output power ~ 1.2 MW). Multi-frequency oscillation (178GHz/207GHz/265GHz) is expected. Compact loads for viewing ports Dummy load for relief window DC-break coolant (Fluorinert) DC-break Absorber (Water) Mirrors Radiator Cavity 0 2 10 -4 4 10 -4 6 10 -4 8 10 -4 1 10 -3 8 8.5 9 9.5 10 10.5 Coupling coefficient [a.u.] Beam radius [mm] TE19,7 TE37,13 TE31,11 TE25,9 1 1 main sub rad r , main , sub cos cos mn mn m m N I. 1.0 MW steady state operation has been achieved for ITER, and over-1MW of 1.2MW with ~ 50 % have been demonstrated. II. Quad-frequency oscillations (0.9MW/5s/104GHz, 1MW/6s/137GHz, 1MW/300s/170GHz, 0.4MW/5s/203GHz) have been demonstrated. III. 236 GHz (TE 43,15 ) for DEMO can be expected up to 0.9 MW output power even if the ITER gyrotron. Over-1 MW will be expected by exciting TE 49,17 mode. Summary 30 40 50 60 0.6 0.8 1 1.2 Achieved efficiency [%] Output power [MW] (Pulse length > 2sec) Maximum power : 1.23MW/47% TE 43,15 mode 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 20 40 60 80 100 15 20 25 30 35 40 45 Oscillation power [MW] Oscillation efficiency [%] Beam current [A] f osci ~ 236.07 GHz V beam = 72 kV, = 1.2, B c ~ 9.29 T 2 kW/cm 2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 0 20 40 60 80 100 25 30 35 40 45 50 55 Oscillation power [MW] Oscillation efficiency [%] Beam current [A] f osci ~ 235.98 GHz V beam = 72 kV, = 1.2, B c ~ 9.28 T 2 kW/cm 2 TE 49,17 mode Possibility of 236 GHz oscillation for demo-reactor generation 170GHz (Present design) 170GHz (Modified) 104GHz (Present design) 104GHz (Modified) 95 96 97 98 99 100 170GHz(Modified) 104GHz(Modified) 170GHz(Present design) 104GHz(Present design) Transmission efficiency [%] Radiator M1 M2 M3 M4 Window 97.4% 95.5% 98.5% 98.1% Target efficiencies is > 98 % at both frequencies. Improvement of 2 % is achieved at 104 GHz. The efficiency at 170 GHz is comparable. Beam profile at radiator (Beam voltage: 72kV and beam current : 40 A) Cavity radius: 23.80 mm Beam radius: 10.31 mm Window thickness : 2.14mm Case 1 : ITER type gyrotron Case 2 : Modified gyrotron