G.McMonagle, 8 th July 2011 CLIC Project Meeting X Band Stand Alone Power Source at CERN Stand Alone Power Source (SAPS) The story so far

G.McMonagle, 8th July 2011

CLIC Project Meeting

X Band Stand Alone Power Source at CERN

•Stand Alone Power Source (SAPS) •The story so far ....................

•Future requirements for SAPS at CERN•CPI order•Modulator requirements•Where to install at CERN

•Conclusions



Stand Alone Power Source

• Beginning of 2008 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 at that time

• 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 contribution from CERN.

• Memorandum of collaboration was finally signed 1 year later. 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, one for CERN



CEA SACLAY (Modulator and RFcomponents)

CERN

SAPS to be installed and run at CERN in the CTF3 facility

SLACKlystron XL5 Based on XL4Best efforts agreement

Special French Contribution

Financed by CLIC Project

PSI Trieste



SAPS Installation and Requirements

Klystron

50 MW1500 ns 50 Hz

test slot

200 MW, 0 ... 100 nsor100 MW, 0 ... 350 ns

phasemodulation

hybrid

Modulator

pulse compression

CTF2

KlystronGallery



F-Cup+Isolator

Stand alone Test Stand in CTFII

Concrete block

girdergirder girdergirder girdergirder

ACC

pump

Pump Tee

load

coupler

Circular WG

Mode converter

WG valve

0.5 m

0.5 m

Courtesy: S. Doebert



XL5 X Band Klystron specParameters 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 kV

Heater voltage 20 max V

Heater current 30 max A

Heater start up surge current ?max A

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

parameters, and 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



CLIC WS 10/2009 KM Schirm BE-RF 8

1

High Voltage Modulator

Specification :

High Voltage : 450 kV

Current : 335 A

Flat pulse length: 1.5 µs

Pulse length at 50%: 2.3 µs

Repetition rate: 50 Hz

HV ripple: � 0.25 %

Pulse to pulse stability: � 0.1 %

(1.8 x 3 x 2 m3)

HVPSPULSE

TRANSFORMERSOLID STATE

SWITCHKLYSTRON

L1L2

L3

1000VDC 1000V 450kV

Development of a new solid state modulator by

SCANDINOVA

Klystron XL5

Magnet

Solid State Switch modules

Magnet and Ion pump power supplies

Water cooling circuit

Oil tank with pulse transfomer

Tuning circuitOil pump and filter

K2-SYSTEM PULSES, 265kV / 262A

K2-SYSTEM PULSE FLATNESS <0.4%

K2-SYSTEM PULSE-PULSE STABILITY <0.04%



External Water Cooling System

Filament DCPS 0-30A

Core Bias DCPS

HVPS#1 - N

Control System Unit

Power Distribution Unit

L1L2L3

GND

Water Cooling Distribution

SW#3

SW#1

SW#2

SW#n

RF-Source

RF-Amplifier

Solenoid PS #1-3

Ion Pump PS 5X

Modulator >45 L/min

Collector >120 L/min

Body>10 L/min

Solenoid >10 L/min

TrigIpulse

Upulse

Remote RS232

12GHz

400VAC50Hz

Safety Interface

3-phase 480VAC

1-phase 120VAC

Local RS232

K2 Solid State ModulatorPulse

Transformer Oil Tank

RF 3GHz

3x185A

CT

CVD

Water Flow Interlocks

Vacuum Interlock

Current Interlock

Waveguide pressure Int., Arc Int, VSWR Int.

L1N

GND230VAC5

0Hz

MODULATOR AND RF SYSTEM, OVERVIEW



Modulator delivered to CERN(only tested in dummy load waiting for klystron)



XL5 performance at SLAC

“This is a 50MW Klystron not 60MW!”Daryl Sphren , SLAC

Voltage, Current and rf waveforms at 57MW 1.25us



Klystron Delivered to CERN



Klystron installation in modulator

Oil was removed fromtank after dummy load testssome very small metal pieceswere noticed at the bottom ofThe tank. This worried our SLAC colleaguse



Pause to resolve some issues

• Modulator oil tank was not airtight and we were not convinced the whole gun was covered with oil.

• Modification to tank to allow the transformer side to be higher than klystron by inserting a shim plate

• Klystron removed for this operation



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 showedceramic feed throughon ion pump was leaking

New ion pump and valve installedtube pumped down vacuum ok



Bakeout

Tube was baked out at 200 degrees for 4 daysActivated cathode during the bake out periodSuccess 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 cathode2. Gun misalignment

Varied filament heater current with constant klystron Voltage.From results looks as though cathode performs as expectedProbably rules out cathode pollution



Ruling out cathode pollutionand with 10% body interception

(nominal <1%)This leaves gun misalignment

investigationTube removed again

















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?

• Good news• Latest communication from SLAC



“I think we have some very good news to share but I'd like to discuss it with the rest of our group before making a formal statement.

Last Friday we stretched the eyelet joint on an old 5045 (same seal and eyelets as the XL) while it was under vacuum... We found that although the joint would spring back closed after small displacements, it would stay open with increased stretching. We stretched it enough to stay open ~1.5mm (0ne side only so tilted just like XL5-2). At that point we simply clamped it back down using 2 bar clamps (one at the high point and one at 180 deg)... not much force was required. We found that the joint stayed closed and matched original dimensions within .001 to .002". As we don't know how the XL5 seal was disturbed, the results may not be duplicated but I think we will request a try once we discuss details and cautions etc. -Andy”

There is still some hope that we can recover quicklyWaiting for instructions from SLAC



Future SAPS at CERN• In autumn last year we decided that we want to

order two more XL5 klystrons • 1 for spare and 1 for second test area

• In contact with our SLAC colleagues• If possible would like an industrialised klystron,

SLAC of same opinion for their XL4• Price enquiry made to industry 3 firms contacted• Thales, CPI, and Toshiba• Thales declined as they could not meet time

schedule (minimum 5 years estimate from them as they have no in house experience at this frequency)

• Toshiba made offer but conditional on receiving XL4 order as well• They did not get the SLAC order and withdrew

from CERN tender• CPI only valid tender• Finance committee approved order for two

klystrons plus option of third with CPI in June this year

• First klystron due at CERN beginning 2013



Planning

• Kick of meeting with CPI on 25th and 26th July• Once parameters are confirmed

• Call for tender for modulator (one or two?)

• Order TWT klystron driver and RF components

• Decide on location for next test stand(s) ?

SM18XExcludedno space



B.2002

Possible in old EPA kicker magnet areaBut may be difficult to get 2 test areas in zoneGood location beside CTF3



B.152

LINAC 4 Test StandDepends on planning For this area



CONCLUSIONS• Difficult times over last couple of years• Still optimistic in getting the SAPS running

soon• Challenging program with very limited

resources to get 2nd (or even 3rd) SAPS running for start of 2013

• Any location suggestions for these test stands welcome

• Some new ideas for further test stands (see Igor’s talk)



Thank you for your attention

Documents

G.McMonagle, 8 th July 2011 CLIC Project Meeting X Band Stand Alone Power Source at CERN Stand Alone Power Source (SAPS) The story so far