1. 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

2. 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

3. 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)

4. 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 !

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

6. 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

7. XL5 X Band Klystron spec Parameters Specifications units RF Frequency
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 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

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

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

16. 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

17. 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

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

24. 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?

25. 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

26. 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

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

28. 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

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

30. 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 

31. 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?

32. 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

33. 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

34. 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

35. 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

36. Thank you for your attention