Klystron Modulator Systems for CLIC 500 NLCJLC Revisited

Klystron Modulator Systems for CLIC 500 NLC/JLC Revisited Progress in technology for increased efficiency? cost estimate

NLC Initial Baseline Design • 75 MW Klystron (approx 2000 per LINAC) – Solenoid focussing (25 k. W per klystron) – 55% efficiency – 0. 0002 duty cycle (120 Hz, 1. 6µs) • Average RF output power of klystron 14. 4 k. W – 1 k. W heater power per klystron • Line type modulator – Pulse transformer 20% wasted power with rise and fall time – Thyratron switch, 600 W per thyratron • Overall Power Requirement per Klystron/Modulator – 58 k. W • 116 MW/LINAC • This technology is known and works

Simplified RF System Layout Klystron RF output TWT Klystron Driver 2 KW Klystron (~55% efficient) LLRF Pulse Compressor Modulator ~80% efficient Beam Compressed pulse ~ x 2 to 3 in amplitude

NLC Baseline Design circa 2002 • 75 MW Klystron (approx 2000 per LINAC) – ppm periodic permanent magnet focussing (no solenoids) – 55% efficiency – 0. 0002 duty cycle (120 Hz, 1. 6µs) • Average RF output power of klystron 14. 4 k. W – • 1 k. W heater power per klystron Solid State Modulator (1 per two klystrons) – Pulse transformer 20% wasted power with rise and fall time • Overall Power Requirement per Klystron/Modulator(0. 5) – 31. 5 k. W • • • 63 MW/LINAC Klystron development was not finished, some problems with pulse width and high rep rate, peak power achieved Modulators – Many iterations were done on different types of solid state switches, but still with pulse transformer. Only recently can we confidently say that this technology is properly developed

Realistic Goals for CLIC 500 • PPM Klystron development will definitely need to continued(R&D Costs) – Pulse width – Duty cycle • New Marx Type modulators being developed at the moment that look promising – no pulse transformer hence faster rise and fall times greater efficiency >88%

Klystron Costing • Price enquiry out for industrialised X band klystron at the moment • Expected price ~ 500 k. CHF • Large orders for CLIC 500 – Lots of dependencies – Manufacturer needs tests stands to condition tubes to full power, unless CLIC 500 pays for a large majority of these and eventually installs most of them in the LINAC then unit price wont come down significantly. Remember we need ~ 4500 klystrons that take probably 2 weeks per klystron to be conditioned – 1 modulator can test ~20 klystrons per year

Modulator Costing Approximate price for a modulator today is ~480 k. CHF This can be significantly reduced for large quantities as long as there is a modular design I would estimate at least a 50% reduction

Additional costs • Not to be forgotten – Pulse compressors, very difficult to manufacture and very expensive • Don't forget temperature stabilisation – TWT klystron drivers, very unreliable • ~ 50 k. CHF each, • a sold state solution should be found (does not exist at the moment)