Progress and Status of X Band Stand Alone Power Source (SAPS) at CERN History 2007 to now What is present situation Future requirements for SAPS at CERN

Optimistic Planning Presented CLIC 07 workshop CERN decided that to complement the testing being done at KEK and SLAC a high power X band power source is necessary for testing structures on site at 12GHz Market survey showed that there was no source available from industry Initial contact with SLAC klystron department for a collaboration to develop a 12Ghz klystron based on the existing 11.4 GHz tube was positive Wheels in motion for a collaboration between CERN and SLAC with financial contributions from CERN. Optimistic Planning Presented

At the time there was some opinion that this was too pessimistic 2009 2010 In reality due to administrative problems the final contract agreement was delayed one year 2007 2008 2009 11 12 1 2 3 4 5 6 7 8 9 10 Klystron feasibility and costing enquiry   Finance Committee Approval (for klystron collaboration and project approval) Order Klystron Klystron Manufacture and Delivery Modulator Price Enquiry Modulator Manufacture and Delivery Preparation of Modulator area Procurement and preparation of auxiliaries Preparation of test area Procurement and manufacture of test area equipment Low level RF START TEST STAND COMISSIONING (single klystron)

During this time PSI and Sincretrone Trieste joined in the collaboration. The MoU was signed under a “best efforts” agreement In total 5 klystrons were ordered Only one for CERN !

SAPS Installation and Requirements Klystron 50 MW 1500 ns 50 Hz test slot 200 MW, 0 ... 100 ns or 100 MW, 0 ... 350 ns phase modulation hybrid Modulator pulse compression CTF2 Gallery

ACC Concrete block Stand alone Test Stand in CTFII Circular WG F-Cup+Isolator Stand alone Test Stand in CTFII Concrete block girder ACC pump Pump Tee load coupler Circular WG Mode converter WG valve 0.5 m Courtesy: S. Doebert

XL5 X Band Klystron spec Parameters Specifications units RF Frequency 11.9942 GHz Peak RF power 50 MW RF gain dB Efficiency % RF pulse length 1.5 µs Pulse repetition rate 50 (100) Hz Duty cycle Klystron voltage 410-470 kV Klystron current A Inverse klystron voltage 100 max Heater voltage 20 max V Heater current 30 max Heater start up surge current ?max Preheating period 60 min

Modulator Exceptional financial contribution to CERN from France modulator and some RF components came via CEA Saclay collaboration Modulator specification based on SLAC klystron parameters, and the limited space available in the klystron gallery Call for tender launched Four offers 2 were of similar priced 1 line type modulator and 1 solid state Contract was awarded to Scandinova, mainly based on footprint of modulator, delivery schedule and our interest in using new technology

Modulator delivered to CERN (only tested in dummy load waiting for klystron) In hindsight choosing a new technology for a project with a tight time schedule was probably not the correct one

XL5 performance at SLAC (Feb 2010) Despite admin delays SLAC had klystron ready ahead of schedule Voltage, Current and rf waveforms at 57MW 1.25us Best efforts agreement meant CERN had to pay for repair Klystron eventually delivered to CERN end of October 2010 Unfortunately during preparation for shipment the klystron was damaged

Klystron Delivered to CERN Although there was some cosmetic damage the tube vacuum was ok and there didn't seem to be anything visually wrong with the tube

Klystron installation in modulator with help from our SLAC collaborators Many teething problems with modulator calibration, interlocking etc. But we got first pulse on klystron before end of the year, stopped to do some modifications to modulator

First signs of trouble When klystron was reinstalled we turned Ion Pump supplies on and they indicated that the klystron was up to air ... Disaster as klystron is sealed unit with pinch off Contacted SLAC and we decided a leak test may be possible, SLAC sent engineer to participate While waiting for SLAC engineer, we removed the tube and contacted our vacuum group to see what was the best way to proceed

Leak test showed ceramic feed through on ion pump was leaking New ion pump and valve installed tube pumped down vacuum ok

Tube was baked out at 200 degrees for 4 days Activated cathode during the bake out period Success tube ready for reinstallation

Reinstallation of klystron in modulator Several issues with believing current and voltage calibration of the modulator But tube was pulsing !!! If we believe the figures from the voltage and current waveforms the perveance on the tube is lower than what was seen at SLAC Temperature probes were installed at input and output of collector water cooling and also a precision flow meter in order to do a calorimetric check. Unfortunately the calorimetric measurement confirmed the low perveance and allowed us to believe that the voltage and current measurements were correct

Some measurements Two possible causes for this 1. Cathode pollution, not getting uniform electron beam from cathode 2. Gun misalignment Varied filament heater current with constant klystron Voltage. From results looks as though cathode performs as expected Probably rules out cathode pollution

Ruling out cathode pollution and with 10% body interception (nominal <1%) This leaves gun misalignment investigation Tube removed again

Conclusive that there is a misalignment although we don't really know how it happened what do we do ? First option We send the tube back to SLAC for repair As its a best effort collaboration will cost us 200k$ and at least 6 months delay Second option Long shot, try and realign gun at CERN Risky but if it doesn't work the tube will have to be sent back anyway Extra 4 week delay but worth the risk?

After consultation with SLAC we prepared a clamping system to squeeze the gun on the “low side” The process seemed to have worked and the misalignment was removed and tube vacuum still ok Tube reinstalled in modulator

NOW SOME GOOD NEWS While repairing klystron some additional measurement systems were implemented in the modulator to help with our calibration doubts Started pulsing klystron at short pulse width on 30th August All seems fine running at around 370kV 50Hz By 2nd September we got to near nominal pulse width at 50 Hz and at approximately 370kV

Many measurements were performed to see if the klystron behaves as it did in SLAC Electrically it works

NEXT STEP RF To remove any doubts about the exact voltage we are running at we need to put RF on the tube and compare to gain curves from SLAC Initial testing is into short waveguide system with two RF loads

First RF from klystron on 6th September Snippet from logbook No vacuum activity in klystron only loads

Latest news Running at 50Hz , ~350 kV, RF at 132ns, Gain of tube about 52dB Pin [W] Prf[MW] Gain [dB] ReRa [Hz] RFPW [ns] E [J] ave Pload [W] 52.2 7.94 51.8 50 132 1.05 52.40 Vacuum in loads Vacuum in rest of waveguide network No vacuum activity in klystron 

Next Steps Continue RF conditioning Verify gain curves to complete voltage calibration Loads are limiting factor (hopefully) Will probably take some time before we reach nominal power Once loads are conditioned install final assembly for cavity testing May be a good idea to recover conditioned loads from SLAC?

Future SAPS at CERN (1) We have ordered two more industrialised XL5 klystrons fron CPI 1 for spare and 1 for second test area CPI working with SLAC to finalise design Klystron Schedule Final design review October 2011 Delivery 1st Klystron no later than December 2012 Deliver of 2nd klystron July 2013 Option to purchase a 3rd tube

Low Power klystron test stand Future SAPS at CERN (2) Call for tender for modulator, with option for a second will go out once final klystron design is accepted in October Spare tube, can it be a working spare in another test stand ? Any offers or ideas from our collaborators? Low Power klystron test stand Igor Syratchev has proposal for high rep rate multiple low powered klystrons to be used as test stand (see talk in AWG4 Thursday 18H00) There has been some initial contact with potential klystron suppliers Global market survey from CERN for klystrons and or turn key solution will be done this year

With budget approval and if an appropriate site could be found we would like to have a specific CLIC test area, even for drive beam klystron testing

Acknowledgements PSI Sinctritone Trieste Colleagues at CERN CEA Saclay Karl Schirm Stephane Curt Ghislain Rossat Igor Syratchev Jan Kovermaan Steffen Doebert Germana Riddone Luca Timeo And many more..... CEA Saclay Franck Peauger Abdallah Hamdi Wilfrid Farabolini SLAC Daryl Sprehn John Paul Eichner Eric Jongwaard Andy Haase PSI Sinctritone Trieste

Thank you for your attention