Present Status and Future Upgrade of KEKB Injector

Present Status and Future Upgrade of KEKB Injector Linac Kazuro Furukawa, for e–/e+ Linac Group Present Status Upgrade in the Near Future R&D towards Super. KEKB K. Furukawa, Feb. 24. 2005. 1

Present Status and Future Upgrade of KEKB Injector Linac Electron/Positron Injector Linac u. Machine Features v 600 m Linac with 59 S-band rf Stations, most of them Equipped with SLED to provide 20 Me. V/m v. Dual Sub-Harmonic Bunchers to achieve 10 ps for 10 n. C, and Energy Compression System for Positron u. Beam Characteristics v 8 Ge. V 1. 2 n. C Electron and 3. 5 Ge. V 0. 6 n. C x 2 Positron for KEKB v 2. 5 Ge. V 0. 2 n. C for PF, 3. 0 Ge. V 0. 2 n. C for PF-AR Present Status K. Furukawa, Feb. 24. 2005. 2

Present Status and Future Upgrade of KEKB Injector Linac in KEKB Commissioning u. Challenging Projects since 1998 v. Commissioning (1998~) v. Overcoming rf Breakdowns at the Bunching section and Positron Capturing section (1999~2000) v. Positron Injection with Dual Bunches in a Pulse (2001~2002) v. Reduction of Failure Rate with Careful Management of the Equipment and Beam Parameters, especially at rf Trip Rate (2002) v. C-band R&D for the Future Super. KEKB (2003~) v. Continuous Injection of both Positron and Electron Beams (2004) u. Recent Operation v. About 7000 hours/year v. Machine-trouble time (when some part of the machine is broken): 2~3% v. Beam-loss time (when beam could not be delivered): ~0. 5% v. Routine management of rf Power, rf Phasing, Optics Matching, Energy Spread Optimization Present Status K. Furukawa, Feb. 24. 2005. 3

Present Status and Future Upgrade of KEKB Injector Linac Increase of the Injection Efficiency Feb. 2005 Continuous Injections May. 2000 Apr. 2003 Dual Bunch e+ Present Status K. Furukawa, Feb. 24. 2005. 4

Present Status and Future Upgrade of KEKB Injector Linac Continuous Injection Mode u. Reliability of the Operation v. Frequent Switch was not Considered in the Design ³Vacuum Bellows, Mechanical Phase Shifters, etc. v. Improvement in each Hardware Component, as well as Operation Software v. No Reliability Degradation is Observed Present Status K. Furukawa, Feb. 24. 2005. 5

Present Status and Future Upgrade of KEKB Injector Linac Positron Generation with Crystalline Tungsten (Collaboration between KEK, Tokyo Metro. Univ. , Hiroshima Univ. , Tomsk Polytech. , LAL-Orsay) u. High Intensity Positron is Always a Challenge in Electron-Positron Colliders v. Positron Production Enhancement by Channeling Radiation in Single Crystal Target was Proposed by R. Chehab et. al (1989) v. The Effect was Confirmed Experimentally in Japan (INS/Tokyo, KEK) and at CERN Crystalline Positron Target K. Furukawa, Feb. 24. 2005. 6

Present Status and Future Upgrade of KEKB Injector Linac Experiment at KEK u. Positron Production Enhancement Measurement v. Target Thickness Dependence (2. 2, 5. 3, 9 mm for Tungsten Crystal, 2 ~ 28 mm for Amorphous) v. Out-going Positron Energy Dependence (5 ~ 20 Me. V) v. Incident Electron Energy Dependence (3 ~ 8 Ge. V) v. Single Target or Hybrid Target v. Target other than Tungsten, Crystals used for Calorimeters, Silicon, Diamond Crystalline Positron Target K. Furukawa, Feb. 24. 2005. 7

Present Status and Future Upgrade of KEKB Injector Linac Experimental Setup 60 o Single Target Hybrid Target Crystalline Positron Target K. Furukawa, Feb. 24. 2005. 8

Present Status and Future Upgrade of KEKB Injector Linac Typical Experimental Measurements 9 mm. Wc 2. 2 mm. Wc 9 mm. Wc on-axis off-axis e+ base yield Crystal W Amorphous W Crystalline Positron Target K. Furukawa, Feb. 24. 2005. 9

Present Status and Future Upgrade of KEKB Injector Linac Results and Considerations u. With Tungsten Single Crystal, the Absolute Positron Yields were Enhanced by ~26% at Ee+=20 Me. V, and by ~15% (average) in the range of Ee+= 5~20 Me. V compared with the Maximum Yield in the Amorphous Tungsten. u. Diamond Hybrid Target has been Suggested to Produce 3 Times more Photons (V. N. Baier et al. ), but We need >15 mm Thick Diamond while We could test only 5 mm. And the Radiation Damage is Unknown. u. Another Experiment is Planned just before Summer Shutdown to Refine the Results, and The Optimized Crystalline Tungsten is Planned to Replace the Present Positron Target. The Design of the Target is Under way. Crystalline Positron Target K. Furukawa, Feb. 24. 2005. 10

Present Status and Future Upgrade of KEKB Injector Linac Upgrade Towards Simultaneous Injection (Collaboration Working Group between PF, KEKB, Linac and Others) u. Requirements v. One Linac is used for 4 Storage Rings (Time Sharing) v. Switching between KEKB and other Modes takes ~3 minutes because ECS Magnets have to be standardized. v. Machine Studies in PF and/or PF-AR Interrupt the KEKB Continuous Injection. v. PF Needs Top-up (Continuous) Injection in the Future for Advanced Measurement. u. Possible Solution v. Simultaneous Injection Scheme is Strongly Suggested. v. Beam Switches pulse-by-pulse could be Employed. v. Needs Pulse Bend. Magnet to Kick PF Beam Simultaneous Injection K. Furukawa, Feb. 24. 2005. 11

Present Status and Future Upgrade of KEKB Injector Linac Fast Beam Switches u. Fast Change of the Magnetic Field is Difficult v. Common Magnetic Field (Quad and Steering Magnets) should be Used. v. Energy Adjustment can be Achieved with Low-level rf Controls. ³With Additional Circuits and Controls. v. The Beam is Accelerated up to ~5. 3 Ge. V then further Accelerated to 8 Ge. V for KEKB, or Decelerated to 2. 5 Ge. V for PF. "2. 5 Ge. V" e- optics Preliminary Test by Y. Onishi Simultaneous Injection • Energy = 2. 7 Ge. V (SC 61 H) • gex = m -5 • gey = 6 x 10 m 3. 6 x 10 -4 8 Ge. V e- optics • Energy = 8 Ge. V (SC 61 H) • gex = 2. 5 x 10 -4 m • gey = 4 x 10 -5 m K. Furukawa, Feb. 24. 2005. 12

Present Status and Future Upgrade of KEKB Injector Linac Upgrade Overview u. Upgrade would be Carried in 3 Phases v. Phase-I: Construction of New PF-BT Line Summer 2005 v. Phase-II: Simultaneous Injection between KEKB e– and PF e– v. Phase-III: Simultaneous Injection including KEKB e+ (, PF-AR) u. It was decided to be Carried out as Soon as Possible. Simultaneous Injection K. Furukawa, Feb. 24. 2005. 13

Present Status and Future Upgrade of KEKB Injector Linac PF Beam Transport Optics Design u. The New PF-BT Optics Design is Fixed u. Spare Parts are Collected based on the Design, if Exists u. Other Components are being Designed or being Fabricated u. Phase-I Components (except Pulse Bend) will be Installed at this Summer Energy Spread Monitor Simultaneous Injection K. Furukawa, Feb. 24. 2005. 14

Present Status and Future Upgrade of KEKB Injector Linac C-band R&D towards Super. KEKB u. Higher Luminosity in Super. KEKB v(1) Squeezing Beta at Interaction Region v(2) Increase of Beam Currents v(3) Crab Cavities v(4) Exchange of Energies of Electron/Positron to Cure e-Cloud Issues vetc. u. For Linac (4) is the Major Challenge as well as (2) v. Higher Gradient Acceleration with C-band Structure is Considered to Achieve 8 Ge. V Positron u~24 rf Stations will be Converted v. From: Single S-band rf Station + 2 m x 4 Acc Structure = ~160 Me. V v. To: Dual C-band rf Station + 1 m x 16 Acc Structure = ~320 Me. V ==> 8 Ge. V Positron can be Provided u. Dumping Ring to Meet the IR Design will also be Employed C-band R&D K. Furukawa, Feb. 24. 2005. 15

Present Status and Future Upgrade of KEKB Injector Linac Advances in C-band R&D u. Apr. 2002 -Aug. 2003. v. Design and Installation of ³First rf Station ³First Acc. Structure w. Basically Scale down of S-band One v. First Accelerated Beam (Oct. 2003) ³~38 MV/m at 43 MW u. Sep. 2003 -Aug. 2004. v. Design and Installation of ³First LIPS type rf Compressor (SLED) w. TE 038 mode v. Further Improve for Real Operation v. Accelerated Beam with rf Pulse-Compressor ³~42 MV/m at ~56 MW (12 MW from Kly. ) C-band R&D K. Furukawa, Feb. 24. 2005. 16

Present Status and Future Upgrade of KEKB Injector Linac C-band Components u. Klystron & Pulse Modulator v. Compact (1/3 size), Cooling and IGBT breakdown Issues Solved urf Window v. Mix (TE 11+TM 11) mode Traveling Wave, 300 MW Transmission urf Pulse Compressor v. TE 038 mode (instead of TE 015), Q 0=132, 000, 200 MW Achieved in Test u. Accelerating Structure v. Based on half-scale of S-band Structure v 2/3 p Traveling-wave, Quasi-constant-gradient, Electroplating v. Because of such Simple Design, a few Trips / hour Observed ³Expected to be Solved in the Next Summer urf Low-level and booster Klystron v. May need Modification in Real Operation C-band R&D K. Furukawa, Feb. 24. 2005. 17

Present Status and Future Upgrade of KEKB Injector Linac Improvements in Coming Summer u. Four Accelerating Structures are under Fabrication v. Designed in KEK, and Fabricated in KEK or MHI u. Several Features are Applied especially at Coupler v. Standard or Non-standard (Full-length) Coupler Cell v. Thick and Smooth Shape Coupler Iris v. Coupler Axis offset for Field Correction v. Electro-polishing at Coupler v. Constant Impedance C-band R&D K. Furukawa, Feb. 24. 2005. 18

Present Status and Future Upgrade of KEKB Injector Linac Summary u. Operational Improvements and Future Projects are Carried with Balancing between them u. Continuous Injection Surely Improved KEKB Luminosity u. Simultaneous Injection Project will Help both KEKB and PF Advanced Operation, and also Other Rings in Future u. Oriented Crystalline Positron Target may Enhance Positron Production u. C-band R&D for Future Super. KEKB Advances Steadily but relatively Rapidly, and the Results seem to be Promising K. Furukawa, Feb. 24. 2005. 19