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ASTA Capabilities and Projects

ASTA Capabilities and Projects. Accelerator Structure Test Area High power X-band accelerator structure test facility Deliver high power pulsed RF to high gradient accelerator structures Based on lessons learned at the NLCTA Stephen Weathersby.

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ASTA Capabilities and Projects

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  1. ASTACapabilities and Projects Accelerator Structure Test Area High power X-band accelerator structure test facility Deliver high power pulsed RF to high gradient accelerator structures Based on lessons learned at the NLCTA Stephen Weathersby

  2. High gradient X-band testing of accelerator structures regularly exceeding 100 MV/m gradient • Up to ~300 MW peak power delivered to the structure by combining the power of two XL4 klystrons into a delay line pulse compression system. • Consists of two modulators, two klystrons, delay lines for pulse compression, a radiation enclosure, PPS system, interlocked vacuum and cooling water systems, llrf system, diagnostics and data acquisition… • Past RF gun testing incorporated a UV cathode laser system and small beam line with a beam spectrometer. • S-Band capability Capabilities

  3. High power RF capabilities With two 50MW XL4 klystrons ASTA can produce: 100MW @ 1.5 μs --> 550MW @ 63 ns at X-band and feed two experimental outputs in the enclosure. Variable Delay line length through variable mode converter Gate Valves Variable iris From Two 50 MW Klystrons Two experimental stations inside the enclosure, one with compressed pulse and the other without the benefit of the pulse compressor. Courtesy of Valery Dolgashev

  4. components to support the experimental facilities Gate valve Tee for variable iris Bends for low loss transmission and reliable RF systems Dual moded delay lines with variable delay for a flexible pulse width Courtesy of Sami Tantawi

  5. llrf configuration Power meters Dark current signals DUT FE/RE Klystron RE Vacuum AFG I&Q MIXER TWT K no SLED SRS 60 Hz SRS DG645 4 port combiner SLED AFG I&Q MIXER TWT K

  6. Pulse compression and pulse shaping Pulse compressor forward power Each bin of has independent I&Q modulation via two channel AFGs Forward power RF signals are I&Q demodulated and can be used in pulse shape feedback Delay line tuning is handled by feedback

  7. Breakdown rates vs gradient Breakdown rate vs. pulse length for C10-VG07 forward power reflected power faraday cup 1 faraday cup 2 260 ns 130 ns Faraday cup signals register breakdowns and inhibit further pulses Gradient is calculated. Several weeks for typical structure characterization GS/s acquisition rates Breakdown traces are saved Automated processing

  8. CERN CLIC PETS3 Testing 266 ns 133 ns Peak power Avg power Energy BD Drive beam Courtesy of Alessandro Cappelletti Main beam PETS Accelerating structures RF power

  9. Recirculation Implementation Revised: April 7, 2010 Jake Haimson

  10. Some ongoing and planned HG studies

  11. Test of a Vacuum Brazed CuZr and CuCr Structures Normal copper High Gradient Structures--AAC 2010 Page 11

  12. Clamped Structure Diffusion bonding and brazing of copper zirconium are being researched at SLAC. Clamping Structure for testing copper alloys accelerator structure • The clamped structure will provide a method for testing materials without the need to develop all the necessary technologies for bonding and brazing them. • Once a material is identified, we can spend the effort in processing it. • Furthermore, it will provide us the opportunity to test hard materials without annealing which typically accompany the brazing process

  13. Test of Hard Copper Hard Copper showed an observable improvements of annealed brazed structures Clamped Structure with Hard Copper cells High Gradient Structures--AAC 2010 Page 13

  14. Cryogenic RF material testing at SLAC • Test bed for novel SRF materials • Finding materials with higher quenching RF magnetic field • Leading to higher gradient in SRF accelerator structures • Samples in different forms, thin film or bulk, multilayer, etc • Unique X-band system with compact size and short pulses, resulting lower pulsed heating • Quick testing cycles with small samples • Surface resistance characterization

  15. Cavity design High-Q cavity under TE013 like mode • High-Q hemispheric cavity under a TE013 like mode • Zero E-field on sample • Maximize H-field on the sample, peak on bottom is 2.5 times of peak on dome • Maximize loss on the sample, 36% of cavity total • No radial current on bottom • Copper cavity body • Stable, no transition or quenching • Higher surface impedance • Coupling sensitive to iris radius • Nb cavity body being designed • Lower loss for more accurate surface impedance characterization • Qext is much higher with smaller iris H E Sample R=0.95” Fres, design=~11.399GHz Fres, 290K=~11.424GHz Fres, 4K=~11.46GHz Q0,4K=~224,000 Q0,290K=~50,000 (measured from bulk Cu samples) Q0,4K=~350,000 (Estimated for zero resistivity samples, using measured Cu sample results) Tc~3.6µs(using Q value for copper at 4K) Qe~310,000

  16. Selected test results: MgB2 on Sapphire

  17. Experimental Evaluation of Magnetic Field role in Breakdown Rate Experiments with short standing wave structures and specifically with structures where magnetic field is increased due input slots or field-confining rods (PBG) showed that magnetic field plays an important role in determining the gradient limit. Before we studied effect of rf magnetic fields on rf breakdown high-magnetic-field and low-magnetic-field waveguide tests (V.A. Dolgashev, S.G. Tantawi, RF Breakdown in X-band Waveguides, EPAC02) Here we suggest a test that separately controls electric and magnetic fields using the TE01 and the TM02 modes

  18. A standing wave accelerator cell with iris dimensions similar to standing wave accelerator structure Feed with TM01 mode converter Electric Field along the surface TM02 Mode with resonance frequency 11.443GHz S. Tantawi

  19. A standing wave accelerator cell with iris dimensions similar to standing wave accelerator structure Magnetic Field along the surface TE01 Mode with resonance frequency 11.4244GHz S. Tantawi Feed with TE01 mode converter

  20. Rf Breakdown at Cryogenic Temperatures at ASTA We plant to test hypotheses that connect statistical properties of rf breakdowns to dislocation dynamics in metals: this dynamics dramatically changes at cryogenic temperatures Cryostat “Cold head” of refrigerator Single-Cell-SW structure TM01 input waveguide S. Tantawi et al.

  21. In-Situ Observation of Metal Surface (KEK, SLAC) • Crystal migration due to pulse heating • Interferometer • High resolution microscopy • Pulse temperature measurement by High-Speed Radiation Thermometer • Particles observation by Laser scattering SW structure New pulse heating cavity

  22. Future plans for ASTA • EPICS for remote monitoring and control • Spectrometer to measure gradient • Phase measurements and breakdown localization • 24 hour unattended operation • Move cryostat to ASTA Thanks for your attention

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