1. Commercial high-power X-band experience: klystron/modulators, and waveguide vacuum flanges CLIC Workshop January 2016 G. McMonagle (on behalf of Xbox team)

2. Klystrons Modulators Klystron Drivers Flanges

3. 2008-2010 SLAC Collaboration XL4 to XL5 KLYSTRON

4. XL4 USA frequency 11.4 GHz only high power X band tube in operation No commercial option Long experience at SLAC in building and using these tubes Collaboration between CERN and SLAC to build 12 GHz design (XL5) PSI and Trieste joined collaboration 5 tubes ordered “Best efforts” collaboration, no guarantees 1 st tube installed at CERN in 2010 KLYSTRON

5. ParametersSpecificationsunits RF Frequency11.9942GHz Peak RF power50MW RF pulse length1.5µs Pulse repetition rate50 (100)Hz Klystron voltage410-470kV Micro perveance1.15E-6 KLYSTRON Good collaboration But some problems needed extra payments due to best efforts NO GUARANTEE

6. 2008-2010 SLAC Collaboration XL4 to XL5 KLYSTRON 2010-2014 Call for Tender for commercial solution Limited replies Contract to CPI

7. CPI VKX-8311A Same specification as XL5 Ordered 2 new tubes plus option of buying a 3 rd 1 st tube successfully tested at SLAC Delivered to CERN and installed in XBox1 Tube has been performing fine since installation 2 nd tube also successfully tested at SLAC Delivered to CERN and installed in Xbox 2 During SAT tests problems arose with tube performance KLYSTRON

8. First diode tests (no RF) of CPI#2 tube showed that 0.7 GHz gun oscillations starts at about 240 kV and even generate RF power from the input cavity: Fortunately, going higher in voltage, the instability zone moves towards the rise/fall time, so the plat top can be used now. No margin to reduce Klystron operation voltage Run at nominal even when low power required to avoid oscillations on RF

9. Why were oscillations not visible in SLAC tests ? Consultation between CERN and CPI concluded it must be due to geometry in the high voltage tank, CERN took reservation on warranty of tube performance. CPI manufactured pieces for 3 different solutions to try and resolve the problem 1.Special plates with ferrites to be mounted on walls of modulator tank :- Improvement but did not get rid of all oscillations but could run at a lower voltage with good flat top 2.Plates to change geometry (reduce volume and mimic shape) to match Xbox1 modulator :- No improvement 3.Solution 2 with ferrites :- Slightly better than 2 but 1 was best. Lost 3 weeks of operations with these manipulations, CPI wanted to investigate more but we decided option 1 is sufficient to allow us to run KLYSTRON

10. Are there any oscillations on 1 st tube? Yes but at within a small voltage at around 200kV and on falling edge Above and below these voltages tube is fine. 3 rd tube has been ordered and will be tested in a new Scandinova modulator in CPI factory (not at SLAC) FAT next week First indications from CPI are that there are no oscillations like 2 nd tube but may have similar issue to 1 st, will find out more next week ! KLYSTRON

11. 2008-2010 SLAC Collaboration XL4 to XL5 KLYSTRON 2010-2014 Call for Tender for commercial solution Limited replies Contract to CPI 2013-2015 Xbox 3 Combination of lower peak power klystron with high average power, turnkey contract awarded to Toshiba for 4 klystron modulators

12. KLYSTRON Toshiba E37113 Peak power: 6 MW Beam Voltage: 150 kV Beam current: 90 A Average power: 12.4 kW Efficiency: 47.5% RF pulse width 5µs Rep rate 400Hz

13. All 4 tubes have been successfully installed in the modulators at CERN in October 2015 All have pulsed to nominal parameters in diode mode First tube has also been operating with RF Waiting for delivery of RF waveguide components, LLRF and klystron drivers RF commissioning hopefully starting March 2016 KLYSTRON

14. 2010 Xbox 1 MODULATORS

15. Xbox 1 modulator CEA Saclay collaboration financed modulator Area chosen for modulator installation had limited footprint Therefore size of modulator was critical and CEA also decided to go for solid state technology Contract awarded to Scandinova ScandiNova solid-state modulator (Ser. #1) for powering the XL5 klystron -Designed for 400kV, 300A, 3.25us HV pulse width FWHM, 1.5us RF pulse width at 50Hz repetition rate -Max. 450kV, 350A, 3.5us, 50Hz -Specified 0.25% HV ripple and 0.1% HV repeatability -Compact design (3x2m 2 ) including HV oil tank and klystron -Primary voltage 1400V max. -Integrated control and interlock system -Integrated vacuum and solenoid power supplies for klystron

16. MODULATORS Factory test done into dummy load (no klystron available) Normally modulator delivered to client in fully assembled unit (as in factory) but due to space restrictions had to be disassembled the remounted at CERN SAT tests with dummy load no klystron available Did not achieve nominal parameters until 2015 with CPI klystron installed (arcing in SLAC klystron gun)

17. MODULATORS Issues with 1 st modulator Calibration measurements. In factory no problem into resistive load (so we thought) In SAT, modulator was commissioned with dummy load again as klystron was not delivered yet. When klystron arrived was difficult to correlate measurements from SLAC to measurements at CERN, indications were that the perveance of tube was not correct. Eventually found that SLAC measurements were erroneous by 10% (confirmed by Trieste during their acceptance of tube #3)

18. External Water Cooling System Filament DCPS 0- 30A Core Bias DCPS HVPS #1 - N Control System Unit P o w e r D i s tr i b u ti o n U n it L1L1 L2L2 L3L3 GN D Water Cooling Distribution S W #3 S W #1 S W #2 S W #n RF- Source RF- Amplifie r Solenoid PS #1-3 Ion Pump PS 5X Modulator >45 L/min Collector >120 L/min Body >10 L/min Solenoid >10 L/min Tri g I puls e U pul se Remote RS232 12GH z 400VAC 50Hz Safety Interface 3- phase 480VA C 1-phase 120VAC Local RS232 K2 Solid State Modulator Pulse Transform er Oil Tank RF 3GHz 3x18 5A CTCT CVD Water Flow Interlocks Vacuum Interlock Current Interlock Waveguide pressure Int., Arc Int, VSWR Int. L1L1 N GN D 230VAC 50Hz MODULATOR AND RF SYSTEM, OVERVIEW MODULATORS Current measurements on low side of pulse transformer secondary Not ideal due to stray capacitance giving overshoot on measurement Difficult especially when starting up in short pulse to say where real peak is situated Need a CT on high side For future modulators Initially only SN built HT measurement Later commercial calibrated solution installed

19. MODULATORS GUI interface was not very user friendly No real time and date stamp on interlock occurrences Some switch failure and reliability problems May have been due to many tube arcs in the XL5 tube Flat top on voltage difficult to achieve many iterations on changing tuning elements on each switch Flat top only really perfect at nominal voltage Had some issues with switch units when at nominal voltage Beware if you have to increase charging voltage to keep performance Some switch units may not be triggering and overloading the others (no indication of non triggering switches) When in operation the modulator performance is very good

20. 2010 Xbox 1 MODULATORS 2012 Xbox 2

21. MODULATORS Xbox 2 modulator competitive tender from CERN Scandinova awarded contract Measurement requests implemented into new unit (Calibrated CVD, CT on high side), but not real time and date stamp for intelocks New design of switch unit (unfortunately not backward compatible with 1 st unit) Different spares needed. 3 charging power supplies integrated (2 in first) Unfortunately we decided to commission this modulator with the XL5 as there was pressure to put CPI tube #1 in Xbox1. Resulted in getting modulator to work correctly but not at full pulse width due to tube limitations. Waited for CPI #2 to arrive before full commissioning and tuning of pulse shape Apart from a few teething problems and of course tube oscillations system running very well

22. MODULATORS Xbox in building 150 More space, overhead crane available Manipulation and operation a lot easier than Xbox1

23. 2010 Xbox 1 MODULATORS 2012 Xbox 2 Xbox 3 2014

24. MODULATORS Lessons learnt from previous two projects Price enquiry to klystron manufacturers for turnkey solution Klystron contract awarded to Toshiba who subcontracted modulators to Scandinova Tube and modulators arrived at CERN after full SAT test with klystron Very quick and successful integration at CERN

25. MODULATORS Modified K1 ScandiNova modulator The illustration of new 2 cabinet concept that will be adopted for 6 MW Toshiba klystrons.  Doubled width oil tank. To facilitate installation of the Toshiba klystron which has rather wide (  0.7 m) solenoid.  Additional cabinet (comes for free). It can be used for Klystron RF driver amplifier, Solenoid PS, Ion Pump PS etc.  New Control System that will simplify integration of external parts and offer a lot of new features.  Flexible design (klystrons positioning) to minimize the length of RF waveguide circuit: Modulator parameters (max.) for 6 MW Toshiba klystron Peak RF power: 8.0 MW Pulsed voltage: 175 kV Pulse current: 115 A Average power: 50 kW Pulse length (flat): 5  sec Rep. rate: 400 HZ 1.6 m 1.3m

26. MODULATORS Xbox 3 in building 150 Please sign up for visits later in the workshop

27. MODULATORS New improved performance in modulators due to new control system and GUI FPGA programming of switch triggers and charging power supplies allows easier tuning of flat top by delaying triggers Also allows flat top to be tuned at lower voltages of operation not just at nominal New GUI an excellent improvement Real time and date stamp for interlocks and events Interlock levels and settings a lot more user friendly

28. MODULATORS Final words on modulator performance, measurements made on new S band K2 at SN Same performance on Xbox modulators K2-SYSTEM PULSE FLATNESS <0.4% DC-LEVEL STABILITY K2-SYSTEM USING PRECISION MULTIMETER <0.002% K2-SYSTEM PULSE-PULSE STABILITY <0.04% USING OSCILLOSCOPE

29. Klystron Drivers For Xbox 1 and 2 Using TWT 3kW pulsed driver to provide power to Xbox 1 and 2 ~ 700w needed but allows tube to placed considerable distance away from klystron Non member state Expensive Protected technology, end user statements needed Designed for high duty factor (high pulse rep) Using at 50 Hz peak power drops off after few thousand hours operation Recycling at high prf necessary to recondition tube Recently seeing glitches in pulses causing problems in pulse compression Finite lifetime of tubes, whole unit needs to be sent back for change (long and expensive)

30. Klystron Drivers Xbox 3 Development of solid state driver with a member state company Prototype built achieved 310W output power (initial goal >400W) Tested on Xbox3 A RMS phase and amplitude stability is very good with 0.17 degrees and 0.14% respectively Peak power limited due insertion loss by coaxial combination and isolator inside unit. 4 new units ordered with waveguide combination and output >1.1dB extra gain expected to achieve >400W output (delivery February 2016) If successful two units can be combine to power klystrons in Xbox 1 and 2 Still cheaper than USA TWT

31. FLANGES Xbox 1 and Xbox 2 Using SLAC type male/female type flange Expensive to manufacture flanges and gaskets Attention to detail on integration of “directional” components needed when choosing flanges. Experience in Xbox 1 shows copper plating on flanges is necessary to reduce RF losses and RF heating

32. FLANGES New sexless flange manufactured for Xbox3 (design agreed between laboratories that use x band technology) Initial problem with copper plating, now resolved with new technique at CERN (for more info see Serge Lebet) When mounting it was found difficult to align flanges and keep the flange gasket in place. New mounting jig developed prototype ready this week FLANGE GASKET Initial testing of flange at SLAC

33. Summary New technology, fast learning curve for CERN – And manufacturers Good collaboration between laboratories and commercial suppliers allowing fast development in the field Other competitors coming on market especially in solid state modulators e.g. Ampegon (SwissFEL) and Jema (University of Valencia) 2010 2016 Xbox operations at CERN XFEL’S? Medical apps? University test stands? Xbox3 technology in industry? Thank you for your attention