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Development of X-band High-Gradient structures at Tsinghua University

This workshop presentation provides an overview of the development of X-band high-gradient structures at Tsinghua University, including the design, production, and testing processes. It covers the T24_THU_#1 structure, choke-mode structure, X-band metallic power extractor, and the C3 structure for Thomson scattering source. The presentation also discusses the future work and upgrades in X-band technology.

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Development of X-band High-Gradient structures at Tsinghua University

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  1. CLIC Workshop 2016 CERN, Geneva Development of X-band High-Gradient structures at Tsinghua University Jiaru Shi Tsinghua University (on behalf of high-gradient team) 2016/01/19

  2. outline • Overview of X-band at Tsinghua • Production in Tsinghua • Development of Structures • T24_THU_#1 structure • Choke-mode structure • X-band metallic power extractor • C3 structure for TBA at Argonne • Tsinghua Thomson Source

  3. X Band S Band Overview of X-band at Tsinghua • Industrial X-band linacs 9.3GHz • Since 1990s 2.5MeV Accelerating tube X-band 2.5MeV Linac 6 MeV Accelerating tube

  4. X-band HG • CLIC-study collaboration • Start from 2009 • “Choke-mode damped structure”, design, producing, testing, … • T24 • Single-cell choke • TD24-choke • Tsinghua Thomson scattering source • Status • Upgrade • New x-band power source

  5. Tsinghua Production – Key facility to HG high-precision machine tools and CNC Machine Clean room for RF Measurement Hydrogen furnace

  6. T24_THU_#1 fab/test flow Design for CLIC (CERN) Fabrication of parts (VDL) High power test (Nextef-KEK) Cleaning Etching (Tsinghua Univ.) Bench test (Tsinghua Univ.) Vac bake (Tsinghua Univ.) Tuning(TsinghuaUniv.) Bonding Brazing (Tsinghua Univ.)

  7. The assembly of T24_THU_#1Bonding • Reduced pressure at 0.1MPa.

  8. The assembly of T24_THU_#1 (5)Tuning and baking • Bench test showed an excellent result after Tuning • Baking is done at 500 degree C, 5 days • Compare to 650 degree C, 10 days @KEK/SLAC/CERN

  9. Full history of T24_THU_#1 • Operation started from 2014.10.22 and ended on 2015.7.2 • Totally 6.08e8 Pulses (≈3378 RF-on hours)and 5908 Acc BDs • Conditioning at 51ns, 91ns, 132ns, 173ns, 213ns, 252ns, also try longer pulse width operation at 331ns, 372ns, 412ns

  10. BDR vs RF pulses • Full map of BDR transition • BDR calculated by last 1M pulses • BDR decrease slightly when input power keeps constant, but still many BDR rising peaks

  11. Normalized Gradient Normalized to BDR of 2e-5 bpp/struc and pulse width of 252ns

  12. BD location of T24_THU_#1

  13. Choke-mode structure 2.0mm 1.2mm 1.6mm [1] HaoZha New choke design CDS-C Features include “two-section”, “impedance matching”, “detuning”

  14. Damping result [1] HaoZha

  15. Single-cell SW test structure • Single cell standing wave • 1C-SW-A3.75-T2.6-CHOKE1.6 [Ref: V. Dolgashev] • To test breakdown behavior in the Choke • Also test un-damped to compare

  16. SW choke-mode cavity diffusion bonding

  17. SW choke-mode cavity diffusion bonding test

  18. Geometry of G1.68 choke r5 r5 d2 g23 d3 • d1 is the gap of the choke • Gap is 1.68mm in origin design 3xr1 r7 c3 c2 r_endpipe r4 r8 d23 b_end b tx3 b_in b_coup ebx3 a_in a_end a a r3 d1 c1 d_in d d-t/2 r2

  19. Bench test before bonding • Bench test result is fine

  20. Bench test after bonding • No frequency shift during bonding/brazing

  21. Bench test after tuning • Tune to 11.424GHz@30℃ • Good results in final test

  22. Geometry of G2.1 choke r5 r5 d2 g23 d3 3xr1 r7 c3 c2 r_endpipe r4 r8 d23 b_end b tx3 b_in b_coup ebx3 a_in a_end a a r3 d1 c1 d_in d d-t/2 r2

  23. RF performance of G2.1 choke • G2.1 choke-mode cavity needs more input power 10MW input power for full structure

  24. Manufacture of 1C-SW-A3.75-T2.6-G2.1-CHOKE • Almost keep same configuration as last two cavities’ design • Diffusion bonding in Tsinghua University

  25. Future work • High power test coming soon at Nextef in KEK • NextBuilding TD24-choke Choke-Gap-1.68 No-Choke Choke-Gap-2.10

  26. Metallic X-band Power Extractor At 11.7GHz for RF power extraction at Argonne Wakefield Accelerator Disk-loaded strucure

  27. A X-band (Copper) Power Extractor for ANL disks brazing. (no HOM damping) mode-launcher

  28. C3 structure at 11.7GHz • Design at ANL, 3 regular cells + 2 matching cells • Brazing design

  29. Setup at Argonne Drive off Drive Beam RF Drive on Higher energy Witness Beam Courtesy: Jing, Chunguang

  30. Tsinghua Thomson-Scattering X-ray

  31. TTX linac upgrade proposal 1.5m x30MV/m 1~2 year 50MW 3~5 year 1.5m x 30MV/m + 2 x 0.6m x 75MV/m Replace 3-meter with 1.5-meter x 30MV/m Add X-band to the enerty ~150MeV

  32. X-band structure design, Preliminary Will be refined with the info of RF power source available. Eacc MV/m @ 50MW # of cells

  33. Progress • Ordered • 50MW CPI 11.424GHz Klystron • Scandinova solid state modulator X-box2 50 MW Klystron Vacuum controllers RF Pulse compressor 430 kV modulator LLRF

  34. Summary • T24_THU_#1 successfully assembled and tested • Discussion: 1) baking 2) careful handling/cleaning • Choke-mode damped structures, SW single-cell test • Bonding test with same contact area at each joint • Machining accuracy from RF check: 10um • Gap1.68, Gap2.1 To be high-power tested @ KEK • TD24-choke in the pipeline • X-band application for Thomson scattering Source

  35. Thank you!

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