1. Update of KEK X-band Research Activity March 3, 2009 Shuji Matsumoto Accelerator Laboratory, KEK 2009/3/31US High Gradient Workshop

2. Contents We are running two X-band high power test stands. Status and JFY2009 Schedule of these stations are given. We are working for the high gradient accelerator structures in close collaboration with SLAC and CERN as well as the fundamental researches on high gradient RF field and RF breakdown. 2009/3/32US High Gradient Workshop

3. Those two X-band high power stations we are operating. KT-1 (50MW) Klystron Test, Small experiments (in Lead shield box) Test area in Shield-A Nextef (100MW) Modulator and twin klystrons 2009/3/33US High Gradient Workshop

4. KEK X-band High Power Stations Reassembled old XTF in 2007. A 100MW high power station for the X-band accelerator structure tests. We use Nextef for the collaboration work with SLAC and CERN on developing high gradient accelerator structures of 100MV/m by 2011. Currently, the high power test of T18_VG2.4_Disk#2 is ongoing. Nextef stands for NEw X-band TEst Facility. KT-1stands for Klystron Test stand #1. For small size fundamental studies on high gradient and RF breakdown tests such as narrow waveguides are done at KT-1 50MW station. 2009/3/34US High Gradient Workshop

5. Nextef Configuration A: Modulator B: Klystrons C: Circular Waveguide D: Accelerator Structure in Shield-A. The control hut is not shown explicitly in the figure. Frequency11.424GHz Max power production 100MW Max power for test* 75MW Pulse width400ns Repetition rate 50pps * 25% power loss in the waveguide. 2009/3/35US High Gradient Workshop

6. Nextef layout and information Present layout of the facility – Two klystrons with power combiner. Future layout – Pulse compression to obtain 150MW. – Swich the combined power into Shield-A or/and Shield-B. Relevance to – warm-LC R&D, close collaboration with CLIC structure developments and Nextef serves to get basic high gradient understanding and to develop components. Note that – The facility can run 24 hr/day closely linked with KEKB Injector operation (KT-1 also). 2009/3/36US High Gradient Workshop

7. T18 trend 80MV/m For 1 month 252ns 2009/3/37US High Gradient Workshop

8. T18_VG2.4_Disk#2 Test at Nextef BD’s and BDR during 27 days in December 2008 at 80MV/m (35MW). BDR ~17 str. BD / 566 hr ~0.030 BD/hr/str ~0.75 x10 -6 BD/Pulse/m Finished at 9:00 on Dec. 25 Started at 10:00 on Nov. 28 566 hrs run / 643 hrs = 88% ON 2009/3/38US High Gradient Workshop 200hr

9. Basic high gradient study at KT-1 Narrow Waveguide Please refer to Kazue Yokoyama’s presentation. 2009/3/39US High Gradient Workshop E=125MV/m SUS003 RF KT-1 50MW Station Damage due to BDs is clearly seen.

10. Nextef / KT-1 Schedule as of March 3. 2008 2009 2009/3/3 10 US High Gradient Workshop 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 T18_VG2.4_Disk #2 TD18_VG2.4_Quad TD18_VG2.4_Disk C-band test ? NWG SUS003 NWG CU005 KLY PPM6B Solenoid Kly retest Nextef Sheid-A Shield-B KT-1 Construction Pulse Compression (Schedule will be fixed)

11. Then, I should explain C- band high power test… C-band R&D project is ongoing in KEK for upgrading the positron injection energy in future Super KEKB project. Four 1m-long C-band Accelerating structures are (series CKM) working in KEKB Injector. Additional two, CKM005 and CKM 006, are to be installed in 2009 and 2010 (one per each year). Their high power tests are necessary before their installation into KEKB Injector. CKM005 test is planned in June 2009. We finally made a decision to make a new concrete shield (Shield-B), next to the existing one (Shield-A), for the C-band tests. This enables us to run our X-band and C-band programs simultaneously. Shield-B can be used by X-band test if C-band test does not occupy it. The C-band RF power is produced by the klystron at KT-2 and transferred into Shield- B. The waveguide is used as the delay line of the X-band pulse compression. 2009/3/311US High Gradient Workshop

12. 2009 Configuration of X-Band High Power Test Area Nextef Modulator and Klystrons Nextef Control Hut Shield-A Shield-B KT-1 KT-2 (Loaded C-Band Klystron) Phi-80 Circular Waveguide 2009/3/312US High Gradient Workshop

13. Shield B Shield A Nextef (X-band) Modulator and Klystrons Almost fully packed! X-band High Power station in KEKB Injector Structure Test Hall Feb. 20, 2009 2009/3/313US High Gradient Workshop

14. Nextef JFY2008 1.100MW power production is established with 250ns RF width, 50pps and 70MW power available for the structure test. We may go somewhat beyond this power level if necessary. The machines work basically fine. 2.Test of T18_VG2.4 #2 is ongoing at (or slightly beyond of) its design spec (Eacc 100MV/m, 250ns, 50pps). Test will continue till the end of March. 3.Every breakdown in the accelerator structure is believed to be detected and recorded. Need some effort for the better measurement and analysis of data. 2009/3/314US High Gradient Workshop

15. List of works at High Power Stations in JFY2009 Nextef Shield-A Continue the tests of X-band High Gradient Accelerator structures: T18_VG2.4_Disk #2 test ongoing till end of March. A quad structure, T18_VG2.4_Quad #5, will be installed in April. TD18_VG2.4_Disk will be the next. New Shield: Shield-B will start to work. Condition C-band Structure (CKM-005) in June. Phi 80 Circular waveguide will be ready. It is used for C-band power transmission from KT-2 to Shield-B. It is planned to be switched to the delay line of the X-band pulse compression after C-band test. First test of PC will be in autumn. 2009/3/315US High Gradient Workshop

16. List of works (cont) KT-1 Continue the Narrow Wave Guide High Gradient experiment. Condition a PPM klystron, PPM6B (One of our four PPM klystrons). Start to (re)test of our old solenoid klystron (XB72K). (The operation of a solenoid-focused klystron (named XB72K) at KT-1 is planned to see its performance with longer (1 us) RF pulse length as a study of future version of our pulse compression system.) 2009/3/316US High Gradient Workshop

17. X-band Pulse Compressor Plan One-Channel Delay Line Traveling Wave Type utilizing 22m C-band Low Loss Line ・ X-band PPM Klystron : Expected to be stable at 30 MW. If this is true, → ×2(Klystrons)= 60MW ×3(Compression) = 180MW → we expect the peak power of 150MW (taking into account of the compression efficiency). 2009/3/317US High Gradient Workshop M. Yoshida, S. Kazakov, H. Matsushita

18. ・ Easy Phase Flip compared with Cavity Type ・ Only One Phase Shifter. ・ Utilizing C-band Low Loss Line (φ80). ・ No need to adjust phase difference of different mode. KlystronAccelerator SLED-II Traveling Wave Pulse Compressor One-Channel Delay Line Traveling Wave Pulse Compressor KlystronAccelerator TE 11R TE 11L Delay Line Type: Principle Iris 2 lines Single line 3-dB 2009/3/318US High Gradient Workshop

19. Strategy for Nextef Klystron Accelerator TE 11R TE 11L 750ns → 150ns Gain = 3.6 @ 3dB 22m - One Channel Klystron Accelerator 1500ns → 300ns Gain = 3.3 @ 3dB. Meets solenoid klystron Spec? TE 11R TE 11L TE 12L TE 12R TE 11 Mode Converter TE 11 -TE 12 Reflector Upgrade using higher mode 25 MW×2 Klyston ×gain=3 → 150MW 2009 version 2009/3/319US High Gradient Workshop Future version

20. Φ80 Circular Waveguide for Delay Line ← MO Flange - Fine alignment pin for gasket. - Keep straightness because flanges are tightly closed. 2.5m × 9 = 22.5 m Assembled using EBW - Keep solidness. 2009/3/320US High Gradient Workshop

21. □TE 10 →○TE 11 Mode Converter (by S. Kazakov ) 2009/3/321US High Gradient Workshop

22. Horn (matches to Phi 80 circular WG) Linear Cos (divided by each100mm) TE11 Other modes 2009/3/322US High Gradient Workshop

23. Fabrication of structures for high gradient study Target – Extend SLAC/KEK X-band legacy to recent CLIC approach. Framework – Electrical design by CERN – Mechanical design and fabrication by KEK and SLAC – Assembly and tuning at SLAC and/or KEK – High power tests at SLAC and KEK (until CERN station is established) Four T18_VG2.4_Disk in collaboration with CERN and SLAC – Assembly and testing are being done by SLAC and KEK – These structures serve as a cross referencing. Quadrant-type CLIC structure T18_VG2.4_Quad – Final fabrication process at KEK. Expected to be installed in Nextef in April. 2009/3/323US High Gradient Workshop

24. T18 #1~#4 disks and couplers produced by KEK 2009/3/324US High Gradient Workshop

25. T18_VG2.4_Disk #1 & #2 Assembly at SLAC Parts for Input/Output Couplers Cooling Blocks under brazing Accelerator Body under Diffusion Bonding 2009/3/325US High Gradient Workshop

26. T18_VG2.4_Disk #1 & #2 #1 tested at NLCTA, SLAC #2 being tested at Nextef, KEK 2009/3/326US High Gradient Workshop

27. TD18 disks for damped cavity Cells are being made based on SLAC/KEK HDDS technology. Surface treatment and assembly is to be made at SLAC, following our standard technology to date. 2009/3/327US High Gradient Workshop

28. Yasuo Higashi, KEK Single-cell test samples production by KEK, tested at SLAC 2009/3/328US High Gradient Workshop

29. Pulse heating samples Some of the samples were prepared and provided by MEC, KEK. Lisa Laurent, (SLAC) 2009/3/329US High Gradient Workshop

30. Activities in JFY 2009 1.High power test of a CLIC type quad accelerator structure (T18_VG2.4_QUAD #5, collaboration of SLAC, CERN and KEK) will start from April. We use Shield-A. The structure, TD18_VG2.4_Disk. 2.Fabrication of accelerator structures under the CKS collaboration will continue. 3.X-band RF pulse compression in this autumn. Use the phi-80 circular waveguide. Goal peak power 150MW. 2009/3/330US High Gradient Workshop