Status of our X-band klystrons

Status of our X-band klystrons SLAC XL5 (a short history) CPI VKX-8311A Toshiba E37113

XL5First ‘optimistic’ planning presented at CLIC workshop October 2007 JPD considered it to be too pessimistic !!!

XL5 performance at SLAC (Feb 2010) Despite admin delays (1 year to agree to WFO text) 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 October 2010 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 near air pressure ... 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 (I/V3/2) 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 • Varying heater filament current while pulsing eliminated the idea of cathode pollution (poor electron emission). One other option left, was the cathode misaligned in the gun?

Conclusive that there is a misalignmentalthough we don't really know how it happenedwhat 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

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

First RF from klystron on 6th September 2011 Snippet from logbook No vacuum activity in klystron only loads

For almost 2 years, ~13000 operational hours no problems Gun arcs started occurring in November last year Decided to remove klystron to see if ion pump reading was klystron or modulator problem With klystron removed the modulator circuit for ion pump supply was ok

Klystron moved to assembly area Ion pump at high voltage cathode potential on gun 5kV

5kV

Shell Diala B oil reacted with rubber insulation causing it to “dissolve” 5kV We are now reasonably confident that the tube may still be ok to operate

CPI VKX-8311A • Call for tender for industrialized XL5 equivalent September 2010 • Contract signed with CPI 25th June 2011 for two tubes with option of a spare • Under DOE rules SLAC collaborated with CPI for the industrial design • Delivery of first tube expected March 2013 • After bake out of tube there was a vacuum problem due to some contamination in the gun area – tube refurbishment • Tube shipped to SLAC for testing July 2013, took 5 months to condition to nominal 50 MW (not just klystron problem but RF network conditioning and no 24/7 running at SLAC) • Tube final factory acceptance tests January 2014

CPI VKX-8311A

CPI VKX-8311A • 2nd tube has been assembled and baked out • After consultation with SLAC the bake out temperature was increased by 90 degrees compared to first tube • Unfortunately there are 2 leaks on the output gaskets on the waveguide components • New gaskets being manufactured • New bake out in 2 to 3 weeks • Testing at SLAC probably beginning of April • Acceptance tests estimated for June/July 2014 (if testing goes well) • Option for 3rd tube, not ordered yet

Toshiba E37113 • 6 MW, 400 Hz, 5µs • Turnkey solution for 4 klystron modulators • Tender March 2013 • Contract August 2013 • Delivery of fist pre series klystron modulator planned for October 2014 • Klystron design and manufacture ahead of schedule • Modulator on schedule • 3 series production units no later than July 2015

Toshiba E37113 Compact Scandinova Modulator Klystron outline

Toshiba E37113in XBOX 3

Summary • XL5 removed from XBOX 1, will be installed in XBOX 2 next week • Commission modulator with this tube • Test if tube is ok • Condition crab cavity • CPI tube S.No. 1 • Arrives next week • Install in XBOX 1 (happy with modulator, easier to commission new tube) • Test into load tree to full power (50 MW, 1.5µs) • Put load tree in CTF2 and condition RF network with compressed pulse • Connect to cavity in dogleg and condition • CPI tube S.No. 2 • Upon arrival install in XBOX2 to do acceptance tests on tube • Keep XL5 as hot spare if still considered operational until CPI tube number 3 arrives, otherwise send back to SLAC for repair

Status of our X-band klystrons