PERFOMANCE OF THE CROWBAR OF THE LHC HIGH POWER RF SYSTEM Gianfranco Ravidà*, Olivier Brunner, D. Valuch, CERN, Geneva, Switzerland R10 55 meters Cathode INTRODUCTION MODULATOR Anode In case of an arc occurring inside a klystron, which is operated at -58 kV and 9 A, the high voltage energy 4 400 meters N O R 3 T S N MA2622A Y is removed from the tube by triggering a thyratron which then becomes conducting and acts as a short circuit O L 2 R K T N o S t O Y R L T K 1 S of the HV power supply to the ground. o Y t N L O K R o t T S Y Circulator L R10 5 mH K 300 kW o t SWITCH Waveguide Waveguide 400 MHz RF Thyratrons are reliable from the point of view of protecting the klystron, but suffering from auto-firing! -100 kV/40 A 4 µF A solid state solution, based on a stack of thyristors, has been designed for a direct thyratron replacement and AC/DC PC LHC BEAM has recently been implemented. Superconducting Cavities Charge SEPARATOR CROWBAR CAPACITOR KLYSTRON 4-5 K THYRATRON CROWBAR PERFORMANCE The current CROWBAR made by a 5 gap double PARAMETERS fast discharge of the 4 μF capacitor & the long slow discharge of the 5 mH coils of the power ended thyratron (CX1194/B) is requiring a very fine coaxial cables (≈ 6000 A, 200 μs) converter (≈ 60 A, 340 ms) From separator To 4mF capacitor adjustment. – 58 KV Ø 1 5 V From 5000 6.6 V stabilizer 550 ns Turn ON Delay, 1200 ns rise time EEV coil - 70 V 7 MA2622A transformer 100 KV 220 / 70 V 0.5A isolating 220 / 5 V 3 A transformer 220 / 6.6 V 40 A 220 / 220 V 30 K HV side 4000 2000 H R 25 Optical fiber G1 K G 1 Electronic box G 2 (mandoline) Optical fiber ext. trigger W 250 pF M 3000 20 0 2 470 W 1500 W 250 pF M 0 2 15 470 W 2000 W Ispark M 0 2 470 W 1000 10 Current (A) Current Current Current (A) W CX 1194 / B M Icapacitor 0 2 1000 470 W W 5 M G.1 0 Ithyratron 2 Anode Current (A) Current G 2 500 70 V G 1 Rectifier card Ø 1 6.6 V From 0 External 5 V 0 transformer H R Ø 7 0 50 100 150 200 transformer 0 50 100 150 200 250 220 / 70 V 0.5A 220 / 5 V 3 A 220 / 6.6 V 40 A LV side A MES.V -5 0 -1000 0 500 1000 1500 2000 2500 Time (us) Time (ms) - reliable from the point of view of protecting the -500 klystron, Time (ns) ARC ENERGY DISSIPATION - suffering from auto-firing! 1500 250000 200000 1000 150000 Integral (a.u)Integral SOLID STATE THYRISTOR (A) Current 500 100000 Thyratron CX1194/B CT (-26kV) CT: Trigger. Current Transformer : D1 MA2622A 100:1 (-26kV) APP 56SA-18E (Trigger Board) CATHODE Current D2 0 50000 350 ns Turn ON Delay, 2500 ns rise time (-58kV) 0 1 2 3 4 5 6 7 8 9 10 APP 56SA-18E (MA2622A & Short Stack) PARAMETERS D1 : BY527 D2 : 1.5KE440CA T1 0 -500 0 10 20 30 40 50 T2 Time (us) E VOLTAGE (kV) TRIGGER CABLE 8 1 - T3 A 6 ) 5 V S CONCLUSIONS k : Connection at -26kV 2 New CROWBAR made by a solid state e T9 t 7 ( a t A fully validated upgraded thyristors stack has been installed in LHC in February 2012. It device (APP S56A-18-E), made up of S T15 d i Ti : S38-G :APP module (x18) l equips one of the four HV bunker. Until now the device has proven to be very reliable and 18 single thyristors stages no need o S T16 for any extra control electronics give full satisfaction. Other thyristors based crowbars are in production to equip the three T17 other bunkers. ANODE T18 Fast part of CROWBAR Current. Current A long reliability run as well as complementary measurement of the energy lost into the arc (GND) Transformer : Pearson 150. will be made in the near future. *[email protected] .