PERFOMANCE OF THE OF THE LHC HIGH POWER RF SYSTEM Gianfranco Ravidà*, Olivier Brunner, D. Valuch, CERN, Geneva, Switzerland

R10 55 meters INTRODUCTION MODULATOR

In case of an arc occurring inside a , 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 which then becomes conducting and acts as a short circuit O L 2 R

K

T N o t S 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 Waveguide Waveguide 400 MHz RF 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 , has been designed for a direct thyratron replacement and AC/DC PC LHC BEAM has recently been implemented. Superconducting Cavities Charge SEPARATOR CROWBAR 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 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) 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 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 (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 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]