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High gradient test results from X-BOX1

High gradient test results from X-BOX1. Ben Woolley XBOX Team CERN, Switzerland February 2014. Overview. System Layout Diagnostics BD detection and response Structure c onditioning progress 100MV/m results for 26 cell accelerating structure Klystron vacuum/arcing issues

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High gradient test results from X-BOX1

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  1. High gradient test results from X-BOX1 Ben Woolley XBOX Team CERN, Switzerland February 2014

  2. Overview System Layout Diagnostics BD detection and response Structure conditioning progress 100MV/m results for 26 cell accelerating structure Klystron vacuum/arcing issues Future developments

  3. Xbox-1 Layout • Clockwise from top-left: • Modulator/klystron (50MW, 1.5us pulse) • Pulse compressor (250ns, ratio 2.8) • DUT + connections • Acc. structure (TD26CC) Gallery Bunker

  4. System Layout and diagnostics Pulse forming network D.U.T HLRF PC tuning piston control Interlock systems Trig. And Clock

  5. Accelerating Structure Diagnostics RF Load RF Load Asymmetric Reflection WR90 Waveguide Ion gauge readout Ion gauge readout Output coupler Input coupler 50 dB directional coupler CLIC Accelerating Structure 3 dB Hybrid Beam-pipe Beam-pipe Incident power Upstream Faraday cup signal Downstream Faraday cup signal Reflected Power Transmitted Power RF Load RF Power From Pulse Compressor

  6. Accelerating Structure Diagnostics Vacuum valve Directional coupler RF hybrid splitter (behind metal support) Ion Gauge Faraday Cup Ion Gauge RF Load Structure input couplers Temperature probe Structure output couplers Ion Pump

  7. Cavity Conditioning Algorithm Automatically controls incident power to structure. Short term: +10kW steps every 6 min and -10kW per BD event. Long Term: Measures BDR (1MPulse moving avg.) and will stop power increase if BDR too high.

  8. BD Detection: Breakdown Wilfrid Farabolini Transmitted pulse drops as the arc is established. Reflected power increases to the same order as the incident pulse. Faraday cup voltages are saturated: 100-1000x increase in charge emitted. We can use the difference in time between the transmitted power falling and the reflected power increasing to find the BD cell location. The phase of the reflected signal is used to pinpoint cell location.

  9. Breakdown: Steps taken We stop the next pulse from occurring and wait 2 seconds to let the vacuum level recover. All the signals are logged to file for later analysis. Over 20-30 seconds we ramp the power from zero back to the power set-point.

  10. 100ns 200ns 250ns 150ns Pulse: 50ns 100 MV/m ~2x10-5BrD/pulse 05.12.2013 ~7x10-5BrD/pulse XBOX1 Full-fledged CLIC accelerating structure TD26R05CC build by CERN is successfully processed in XBOX1 up to 107 MW/m unloaded accelerating gradient at 250 ns pulses . We have started now study of breakdown rate evolution at the fixed (100 MV/m) gradient. CLIC

  11. #668 Total:11168 #1500 ~200 ns ~250ns

  12. BD cell location: TD26CC

  13. BD cell location: TD24R05

  14. Phase measurements Reflected phase are grouped and separated by 2p/3 • About 25% of BDs see a drift in position: • REF pulse is split in 2 parts that shows 2 different phases • The overall phase change is always negative  BD arc is moving towards the input.

  15. New Developments Dark current signal has been split and sampled at 1.25GSPS. Also we’ve added incident RF signal diode. Used to collect data for stress model analysis of the 100 pulses leading up to a BD event. (Collaboration with Uni. Jerusalem) We have successfully demonstrated that we can produce a CLIC pulse shape using the pulse compressor and the phase programmer. Wilfrid Farabolini

  16. Recent 100MV/m run Large BD triggers period of lower BDR but increases dark current. Also after this period there are less cluster events 45% vs. 25%.

  17. The big picture □ - Measured Values ○ - Rescaled by pulse width × - Rescaled to 100MV/m

  18. Results: TD26CC UP-TIME Uptime~75% Uptime <50% Klystron debugging Re-Calibration of signal paths >1week

  19. Klystron Vacuum + Gun Arcs Klystron gun arcs cause high vacuum for 20-50hrs

  20. Klystron Vacuum + Gun Arcs

  21. Klystron Vacuum + Gun Arcs

  22. Xbox-1: Future Developments • We will remove the XL5 from XBOX-1 to look at the gun ion pump. Regardless of the conclusion it will be moved to XBOX-2 for system testing and conditioning at low powers <20MW. • The new CPI XL5 tube (arrival in 2-3 weeks) will be put into the XBOX-1 test stand. • The new tube will be tested up to full power and pulse width using the new load tree (pictured, vacuum leak checked and LLRF tested OK, now prepping for bake-out). • The load tree will be moved to CTF-2 to condition the rest of the WG network. • Connect klystron to dog-leg WG in order to start dog-leg waveguide commissioning in preparation for the beam loading experiment. See Alberto Degiovanni’s talk later today for: • Continue to develop phase measurement analysis. • Utilise other methods for BD cell location: dark current signals and X-rays emitted during BD. • Soon to have installation of dark current energy spectrometer  Should give better indication of the energies involved in accelerating electrons and ions during a BD. As yet unclear if this will run on XBOX-1 or 2. • Quicker/better method of calibration to be devised (less downtime). • Continue conditioning of the TD26CC structure?

  23. Thank You

  24. Extra Slides

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

  26. RF components & RF network integration

  27. Future Developments: XBOX-3 • 4 turn-key 6 MW, 11.9942 GHz, 400Hz power stations (klystron/modulator) have been ordered from industry. • The first unit is scheduled to arrive at CERN in October 2014. The full delivery will be completed before July 2015.

  28. Online automatic adjustment of the compressed pulse (arbitrary) shape.

  29. Summary TD26CC structure is conditioned up to 103MV/m for required CLIC pulse shape and BDR. Gun arcs in the klystron have slowed progress. Work and planning to greatly expand our testing capability is well underway.

  30. Thank you for your attention!

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

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