Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September 2011 CEA SACLAY CLIC R&D Activities F. Peauger, A. Hamdi, M. Desmons, W. Farabolini, P. Girardot CEA Saclay France M. Aicheler, A. Cherif, N. Chritin, J. Kovermann, S. Lebet, G. Mcmonagle, G. Riddone, K. Schirm, A. Solodko CERN, Geneva, Switzerland

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September The 12 GHz Test Stand at CERN Collaboration : CERN, CEA Saclay, SLAC CEA Saclay contribution : Modulator and RF components, in the framework of French exceptional contribution to CERN Objective : high power tests of accelerating structures without beam at 100 MV/m and higher, breakdown rate measurements → the test stand will produce 120 MW peak power with 300 ns pulse length at 50 Hz Modulator Klystron RF Pulse compressor Mode converter Circular waveguide 1st floor of Building 2010 (CTF3 Klystron gallery) Ex-CTF2 area - Building 2010 RF Valve & Mode converter

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Test Stand configuration in Sept Modulator Klystron Bidirectional coupler Vacuum pumping port 3 dB splitter 2 RF loads Low level RF system with TWT

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Modulator Solid state modulator from SCANDINOVA Main specifications: 450 kV – 335 A – 50 Hz – 1.5 µs pulse length (flat top)  Solid state switches IGBT switches, 6 IGBTs per units, 10 units low voltage operation 1kV (60% of their maximum voltage) which increases the reliability  Pulse transformer 5 separate cores and 180 windings on the primary side RL tuning circuits for voltage drop compensation  Charging voltage PS, 4 Ion Pumps PS, 3 Magnet current PS, Control system (local and remote), oil tank, water cooling system, lead shielding for klystron gun, support and lifting device for klystron  Compatible with the 50 MW 12 GHz klystron (XL5) from SLAC Switch Unit including 6 IGBT’s Pulse transformer 1:400

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Modulator issues  Pulse shape uncertainty of klystron cathode current o The signals given by the three current transformers (CT) implemented in the tank are different  30 mm spacer added on oil tank o To increase oil level on the klystron gun  Interlock problem on klystron solenoid current power supplies o 2 PS connected in master/slave condition for one solenoid current: when the slave PS turns off, the high voltage does not stop as expected o in certain conditions in the control system (TERM mode), the interlock does not work properly  Klystron body power diagnostic added o Precise flow meter and PT100 temperature probes installed on klystron body cooling circuit to monitore the klystron beam interception CT1 CT2  Cathode high voltage calibration o Capacitive voltage divider installed in the tank not calibrated, extra cost asked by SN for a calibrated one…

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Specification Achieved High Voltage Vk:450 kV 400 kV Current Ik:335 A300 A Flat pulse length: 1.5 µs min0.5 µs Pulse length at 50%:2.3 µs max3.4 µs Repetition rate:50 Hz10 Hz HV ripple:± 0.25 %± 0.25 % Pulse to pulse stability:± 0.1 % (16 th Sept 11) Modulator test results  Pulse shape measurements: …. Vk Ik 2 cursors at ± 0.25 % 1.5 µs 3.4 µs  Pulse shapes out of specifications improvements of rise time and flatness on the 1.5 µs top required actions investigated by SN: -add high voltage capacitance inside the tank-> test on PSI modulator at factory -Eventually compensate the voltage drop with the RL tuning circuit → Probably needs to remove the klystron from the tank in Oct. 2011

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Test stand conditionning  Operating conditions pulse repetition rate : 1.2 Hz to 50 Hz RF pulse length: 80 to130 ns Modulator charging voltage: 1000 V corresponding to Vk = 368 k, Ik = 245 A (perveance = 1.1 µA/V 1.5 )  Conditionning strategy increase slowly the RF input power check the vacuum level in the klystron and the waveguide network  Klystron performance after repair Same small signal gain as at SLAC Pin [W]Pout [MW]Gain [dB]Fr [Hz]RFPW [ns]E [J]Pload [W] RF pulse shape (in and out) Outgassing in the RF network Gain curve example done in ~1 hour [J. Kovermann – G. Mcmonagle]

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September RF components See « High power rf components » talk, this workshop

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Accelerating structure with wakefield monitors (WFM) To achieve the luminosity in CLIC, we need to align the beam in the accelerating structures to an accuracy of about 5 µm  Beam based alignment technique use higher order mode in the accelerating structure to detect and correct a beam offset  Feasibility demonstration in CTF3 build and equip two TD24 structures with wakefield monitors test on Two-beam test stand ParametersCLIC commissioning CLIC operation CTF3 Charge / bunch (nC) Number of bunches Bunch length (µm) Train length (ns) Bunch Spacing (ns) Accuracy (µm)55 Resolution (µm)5< 5 Range (mm)± 2± 0.1± 2 Beam Aperture (mm) ~5.5 Collaboration : CERN, CEA Saclay CEA Saclay contribution : design of WFM, procurement of accelerating structures and WFM equipement in the framework of French exceptional contribution to CERN

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Accelerating module layout in TBTS Flange with Wakefield monitor feedthroughs Accelerating structure n°1 Accelerating structure support Vacuum tank Vacuum valve Accelerating structure n°2 Probe e- beam RF input and output waveguides Vacuum tank support RF cables for WFM signals

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Accelerating module layout in TBTS Probe e- beam

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September TD24-WFM accelerating structure design Probe e- beam vacuum and dielectric volumes  TD24 structure (CERN design) o 24 cells + 2 matching cells + high power couplers separeted from the cells o No rf absorbers in the damped waveguides o Diamond machining and diffusion bonding of the disks o Tuning studs in every cell  WFM = 90 deg waveguide bend + pick-ups + rf absorber o Implemented on the middle cell o Screwed on the structure with special feature to ensure good electrical contact  Cooling circuit o Brazed on the structure Probe e- beam TM-like modes pick-up TE-like modes pick-up RF absorber WFM waveguide

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Wakefield monitor signals simulations  Time domain simulations with GdfidL o Excitation of hybrid HEM modes in the structure by an offset beam o Record port signals in the of the middle cell damped waveguides on the two first modes  First Port mode ( TM like modes) 18 GHz XX Simulation for a beam offset of  x = 1 mm XX YY X+X+ Y+Y+ X-X- Y-Y- YY  Second Port mode ( TE like modes) X+X+ Y+Y+ X-X- Y-Y- Y+Y+ X+X+ Y+Y+ X+X+ 24 GHz 180° hybrid coupler

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Max. amplitude of the port signal (voltage) Offset  x (mm) Linearity and power range Peak power: - TM modes: 10 µW to 1 kW - TE modes: ~ ten times lower Peak power: - TM modes: 10 µW to 1 kW - TE modes: ~ ten times lower

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Structure fabrication status  Challenge: qualify new suppliers for diamond machining ( MECACHROME) and diffusion bonding (THALES)  Couplers  6 pairs of couplers have been machined very close the specifications  Flatness : 2-4 µm  Roughness: 6 to 25 nm  Shape tolerance:3 to 5 µm  Burrs problem after last turning operation  Shape tolerance errors of 10 µm at the waveguide / beam hole junction (acceptable)  Storage in alcool before solvant cleaning and etching  Small surface pollution on extremity cells  Delivered at CERN for etching the 20th of Sept. Storage in alcohol Burrs Cleaning with co-solvants

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Structure fabrication status: disks  Disks  Prototype Disk (disk 9) machined and controlled at factory and CERN (Leitz tridim)  Very good agreement meaning that the dimensional control at factory can be trusted Control at Factory Control at CERN

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Structure fabrication status: disks  Disks  Prototype Disk (disk 9) surface roughness controlled at CERN and meet the specification of 25 nm Rugosité face A Rugosité face opposée a A Rugosité Iris

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Diffusion bonding  Diffusion bonding test on 3 prototype disks  Under Hydrogen 1 bar  1040°C during 2 hours  Good tightness and cell-to-cell contact

Franck PEAUGER – CEA SACLAY LCWS11 - Grenada 29 th September Conclusion Must carefully follow-up the necessary improvements of the modulator and complete the acceptance tests Follow-up the manufacturing of the accelerating structures for wakefield experiments in 2012 in CLEX Prepare future contribution of CEA Saclay to CLIC  Eucard 2 proposal  Option for a second modulator  CPI Klystron from the CERN order Good opportunities to build a test stand at Saclay