XBOX-2 Status and Crab Cavity Testing Ben Woolley G. Burt, A. - PowerPoint PPT Presentation

XBOX-2 Status and Crab Cavity Testing Ben Woolley G. Burt, A. Dexter, G. Mcmonagle, I. Syratchev, R. Wegner, W. Wuensch, et. al EuCARD2 WP12 Meeting, CEA Saclay, France April 2014

Overview • XBOX-2 Progress: – System Layout & Diagnostics – LLRF tests and results – Installation Progress • Crab Cavity Testing – Design – Tuning Results – Cavity Diagnostics • CLIC Crab Cavity Phase Stability and Synchronisation – Introduction – Phase Stability Experiment 2

System Layout and diagnostics D.U.T HPRF LLRF mixing Temp. Control crate PXI Dark Current Vector Signal Gen. PXI Crate

XBOX-2 LLRF Developments include: • FPGA demodulation; could potentially give us a spare channel (4ch+1ref  5ch + internal ref) • phase feedback control in order to keep the pulse compressor’s output pulse flat during temperature fluctuations. (±1°C tested stable)

XBOX-2 LLRF: Phase Stability • Phase stability performance has Phase (FPGA) been measured. Approximately 0.24 Phase(mix w/ref) degrees of phase jitter between Amp (mix w/ref) adjacent channels (averaged over Ref Amp 300ns). Ref Phase • However approximately 2 degrees with respect to 10MHz reference 2.9GHz LO 2.4GHz LO • Phase noise spectra indicate that 12GHz out the main source of this jitter is the 400MHz IF 2.9GHz local oscillator compounded Meas. Noise by the x4 multipliers. floor • A PLL based LO is under development which will be tested in the coming weeks.

Xbox-2 Layout + Progress • Scandinova Modulator • Klystron (50MW, 1.5us pulse) For Crab cavity test: “old” SLAC XL5 • Pulse compressor (250ns, ratio ~3) • Stainless steel load

Installation Progress • Safety doors and switches for personal protection installed • Electrical protection around the solenoid • LLRF and diagnostics moved to the operating temperature controlled rack. • Cabling between racks ongoing • TWT installation and connection • Access doors and safety chain to the bunker • Set-up of ceiling and additional shielding • Connection of the remaining waveguide network in the bunker • Safety files and RP authorization • Conditioning of the RF network • Installation of supports, spectrometer and diagnostics • Installation of the first structure to be tested

Klystron Vacuum + Gun Arcs 5kV • • We have decided to move the old Gun arcs were possibly caused by a XL5 to the XBOX-2 test stand faulty connection to the gun ion because it was starting to have many pump (pictured above). This was gun arcs. discovered when moving the klystron from XBOX-1. • It can still produce enough power (>20MW) to test the crab cavity without pulse compression.

Klystron Pulsing Pulse 0.8µS; Vkly 343kV 220 Amps µPerveance = 1.1E-6 343kV 1.5µS • Managed to increase voltage reference on IGBT switches to 1150 V • Repitition rate 50 Hz • Heater current 20 amps • Pulse width reference on modulator 0.8uS • “noise” problems on waveform (IGBT switch cable , pulse tx ?) • Some issues with the modulator (Pulse tuning circuit and interlock system) • Klystron gun still breakdowns from time to time

Crab Cavity: Single-feed prototype Single feed prototype for test: • RF design done at Lancaster P. Ambattu • Tuning at CERN. • and G. Burt. High power test at CERN. • Design coordinated by CERN • Manufacturing of disks at VDL, The Netherlands

Tuning of the Crab Cavity centring V guiding the wire for bead- pull measurements nitrogen supply input (chosen and marked) tuning pins (4 per cell) temperature sensor cooling block output (marked) 12.02.2014 Tuning of CLIC Crab Cavity 11

Before tuning bead-pull @ 11.9922 input reflection GHz Bead-pulling at 11992.2 MHz, 0 0.08 -10 sqrt(abs(  S 11 )) 0.06 0.04 -20 -26.3 S / dB 0.02 -30 -34.8 0 1 5 10 -40 phase advance between cells   / cell (DEG) -114 -116 simulated by Graeme Burt -50 -118 S 11 -120 11.9922 -122 -60 1 5 10 11.8 11.9 12 12.1 12.2 12.3 12.4 cell# f / GHz 0 simulated by Graeme Burt combined S11 in complex plane 12 S 11 -10 -0.037 10 -0.038 -20 -0.039 3 -26.3 8 S / dB Imag( S 11 ) -0.04 -30 -0.041 -34.8 6 -0.042 -40 -0.043 4 2 1 -0.044 -50 2 -0.045 11.9922 -0.032 -0.03 -0.028 -0.026 -0.024 -0.022 -0.02 -0.018 -60 11.96 11.98 12 12.02 12.04 Real( S 11 ) f / GHz 12.02.2014 Tuning of CLIC Crab Cavity 12

After tuning bead-pull @ 11.9922 input reflection GHz Bead-pulling at 11992.2 MHz, 0 0.08 sqrt(abs(  S 11 )) 0.06 -10 0.04 -20 0.02 S / dB -30 0 -34.8 1 5 10 -37.9 phase advance between cells -40   / cell (DEG) -118 simulated by Graeme Burt -50 -119 S 11 -120 11.9922 -60 1 5 10 11.8 12 12.2 12.4 12.6 12.8 cell# f / GHz 0 simulated by Graeme Burt combined S11 in complex plane 12 -10 S 11 -0.01 10 -20 -0.012 3 S / dB 8 Imag( S 11 ) -30 -0.014 -34.8 6 -37.9 -40 -0.016 4 1 2 -50 -0.018 2 11.9922 -60 -4 -2 0 2 4 6 8 11.96 11.98 12 12.02 12.04 Real( S 11 ) -3 x 10 f / GHz 12.02.2014 Tuning of CLIC Crab Cavity 13

Crab Cavity Diagnostics Incident Reflected Uppsala Dark Power 60 dB directional Power RF Load Current coupler Spectrometer Transmitted RF In From Pulse WR90 Power Compressor Waveguide Ion gauge Ion gauge Input Output readout readout Screen coupler coupler Dipole Crab Cavity Beam-pipe Beam-pipe Magnet Upstream Downstream Faraday cup Faraday cup Collimator signal signal • Single feed structure requires a Readout different feed to the accelerating structures. • We can take advantage of extra diagnostics with the Uppsala dark current spectrometer.

CLIC Crab Cavity Synchronisation  720 f 1 Cavity to Cavity Phase   x 1 degrees  4 synchronisation requirement c S c rms  x (nm)  c  rms  t (fs) Target max. luminosity f Pulse Length ( m s) loss fraction S (GHz) (rads) (deg) 0.98 12.0 45 0.020 0.0188 4.4 0.156 So need RF path lengths identical to better than c  t = 1.3 microns over 35 m

RF path length measurement 48 MW 11.994GHz Klystron 200 ns 50 Hz Cavity Cavity rep. Cavity Coupler Cavity Coupler 0dB or -40dB 0dB or -40dB RF Phase Measurement reflection reflection System & control Power Power 12 Power Meter Meter MW Meter -30 dB -30 dB -30 dB coupler coupler coupler Magic Tee Lossy Lossy Phase Phase Waveguide Waveguide shifter shifter (-3dB) (-3dB) Power Main pulse Meter reflection Measurement 600 W 4 kW 11.8GHz pulse return Klystron 5 μ s 500W pulse 5 kHz rep.

Waveguide phase stability test 11.992 GHz 11.94 GHz -10 dBm -10 dBm Aims: +23 dBm +23 dBm Diode Diode 1. Establish limit of resolution of Switch Switch p = plane phase measurements for different s = groove Power Power pulse lengths detector seal detector 2. Investigate different mixers Power Power detector detector gas gas 3. Investigate ability to calibrate valve  valve S s s s p p s p p C phase measurements C Magic Tee 4. Implement a piezoelectric H bend p p s s H bend Moveable Moveable Short Short controller on the moveable short s s p p p p p p C C s s to stabilize waveguide s s Variable Variable 10 dB 10 dB 5. Study temperature and vibration p Attenuator p Attenuator s 20 dB 20 dB s p p perturbations on waveguide gas s s C C valve gas p s s p s p p s 6. Investigate whether stabilization valve s p s p s s 2 m waveguide p 2 m waveguide p at one frequency can equalize s p p s sections sections waveguide lengths for other s s p p p s p s p frequency p s s H bend H bend H bend H bend

Phase Stability Test: Control 1. PXI based system has been purchased with 4ch high resolution 16-bit ADC. 2. Also included is a 2ch 16-bit DAC to control piezoelectric actuators which will vary the path length using the movable shorts in order to stabilize the RF path length. 3. Currently performing market survey for piezoelectric actuators.

Future Developments • Continue with the commissioning of XBOX-2. • Test the Crab Cavity up to nominal gradient. • Push the gradient to investigate effect of dipole field on BDR. • Continue preparation for the waveguide stability experiment • Develop and refine phase measurement electronics • Write and test feedback algorithms for phase stabilisation 19

Thank You

Extra Slides

Future LLRF Generation and Acquisition for X-band test stands 12GHz vector 2.4GHz vector modulated modulated signal to DUT 12 signal IF RF Vector GHz Modulator 2.4 GHz LO BPF Oscillator RF out 9.6 X4 LO in LO out Amp GHz freq. 12GHz CW BPF reference LO 3dB hybrid signal 12 2.4GHz CW IF RF GHz reference signal Oscillators BPF IF should be phase LO locked RF Input 1 IF LO 1.6 GSPS RF Input 2 400 IF 11.6 X4 IF Amp Amps MHz GHz 12-bit ADCs freq. LPFs BPF 2.9 GHz LO RF Input 3 Digital IQ IF Oscillator demodulation 12GHz CW LO reference RF_Referance signal

Future Developments: XBOX-2 LLRF Functional plan completed Board Fully Tested PXI hardware purchased and Software partially CPI-XL5 completed tube fully conditioned at SLAC