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Status of the accelerator upgrade

Status of the accelerator upgrade. Dec.10 2008 Mika Masuzawa. Contents. Introduction Luminosity goal Strategy Higher currents Smaller b y * Increase x y What we need Components for higher currents R&D Status IR & Lattice design for smaller b y * & larger x y Summary.

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Status of the accelerator upgrade

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  1. Status of the accelerator upgrade Dec.10 2008 Mika Masuzawa mm 12/10/2008

  2. Contents • Introduction • Luminosity goal • Strategy • Higher currents • Smaller by* • Increase xy • What we need • Components for higher currents • R&D Status • IR & Lattice design for smaller by* & larger xy • Summary mm 12/10/2008

  3. Introduction Luminosity goal mm 12/10/2008

  4. Luminosity goal mm 12/10/2008

  5. Target: 5-8 × 1035 cm-2s-1 =30-50 x World Record (KEKB) mm 12/10/2008

  6. Strategy mm 12/10/2008

  7. Strategy • (1) Increase beam currents • 1.7 A (LER) / 1.4 A (HER) → 9.6 A (LER) / 4.1 A (HER) • (2) Smaller by* • 6.5(LER)/5.9(HER) mm→3.0/3.0 mm • (3) Increase xy • 0.09 (with Crab) → 0.29 mm 12/10/2008

  8. b*y= σz = 3 mm Crab cavity SuperKEKB e+ 9.4 A e- 4.1 A The state-of-art ARES copper cavities will be upgraded with higher energy storage ratio to support higher current. The superconducting cavities will be upgraded to absorb more higher-order mode power up to 50 kW. Tunnel already exists. Most of the components (magnets, klystrons,etc) will be re-used. The beam pipes and all vacuum components will be replaced with higher-current design. Will reach 5-8 × 1035 cm-2s-1.

  9. Strategy Comparison of parameters ( ): with crab mm 12/10/2008

  10. What we need Components for higher currents R&D Status mm 12/10/2008

  11. What we needfor (1) higher beam currents Vacuum components (pipes/bellows…) Modification of the monitors (BPMs,SRMs…) Longitudinal bunch-by-bunch FB system More RF cavities and klystrons Modifications of the RF systems for higher currents New Crab cavities for SuperKEKB mm 12/10/2008

  12. a) Vacuum components Vacuum components⇨talk by K.Shibata tomorrow • Beam current increase causes: • Intense Synchrotron Radiation power • 27.8 kW/m in LER, twice as high as in KEKB • 21.6 kW/m in HER, 4 times as high as in KEKB • High photon density • Photon density ~1x1019 photons/m/s in average • Large gas desorption • Gas load ~ 5x10-8 Pa m3/s/m (for h = 1x10-6 molecules/photon) • Average pressure ~ 5x10-7 Pa for S ~ 0.1 m3/s/m • Electron Cloud Instability (ECI) becomes a big issue in positron ring Heating due to Higher Order Modes (HOM) • For a loss factor of 1 V/pC, loss power ~ 200 kW mm 12/10/2008

  13. a) Vacuum components Beam duct Copper beam duct with ante-chambers • Copper is required to withstand intense SR power Features (compared to simple pipe): • Low SR power density • Low photoelectrons in beam pipe • Low beam impedance • Expensive Pump Beam SR Some sections of KEKB LER have been replaced by ante-chamber type HER LER mm 12/10/2008 Y.Suetsugu

  14. a) Vacuum components Trial model of a copper beam duct with ante-chambers for arc section The duct is bent with a radius of 16 m mm 12/10/2008 Y.Suetsugu

  15. a) Vacuum components More on suppressing photoelectrons TiN (Titanium nitride) coating on inner surface • Decrease secondary electron yield (SEY): Max. SEY ~0.9 • A test stand for the coating was built in KEK, and applied to a test duct with ante-chambers. ⇨Decrease of electrons at high current region was demonstrated. Electron numbers ~4 m f 90 mm mm 12/10/2008 Y.Suetsugu

  16. a) Vacuum components And more on suppressing photoelectrons Clearing Electrode • A possible measure even inside of magnet • An electrode with a low beam impedance was developed and tested with beam (in the presence of wiggler magnetic field of B = 0.77 T). • Thin structure • Electrons decreased to ~1/100 by applying + 300V. Clearing electrode for test Vr = 1.0 kV B = 0.77 T In wiggler magnet -500 V Velec = 0 V Velec [V] Drift space 1 x 10-5 1 x 10-6 Ie [A] 1 x 10-7 Electron Current [A] 1585 bunches (Bs ~ 6 ns) ~1600 mA 1 x 10-8 +500 V 1 x 10-9 Collectors Applied voltage [V] mm 12/10/2008 Y.Suetsugu

  17. a) Vacuum components And more on suppressing photoelectrons • Grooved Surface: being tested with the beam now. • Another possible measure in magnets • Decrease effective SEY structurally M. Pivi TiN~50 nm SS + TiN coating mm 12/10/2008 Y.Suetsugu et.al

  18. a) Vacuum components Grooved surface currently tested mm 12/10/2008

  19. a) Vacuum components For lower impedance: RF shielding Comb-type RF-shield • Comb-type RFshield • Features (compared to finger type): • Low beam impedance • High thermal strength • Applicable to complex aperture • Little flexibility (offset) • Effect of RF shielding was demonstrated in KEKB. • Finger-type as an option • If more flexibility is required. Temperature of bellows Without cooling fan mm 12/10/2008 Y.Suetsugu

  20. a) Vacuum components More for lower impedance: Bellows and gate valves Comb-type RF shield is adaptable to a complicated aperture of beam duct with antechambers. Bellows Gate valve mm 12/10/2008 Y.Suetsugu et.al

  21. a) Vacuum components And more for lower impedance: Movable mask Big impedance sources in the ring • Planning to use “stealth” type (Ver.6) • Low beam impedance • Present Ver.4 ~ 1V/pC (f 90 mm) 200 kW power loss • Loss factor decreases to ~1/10 (f 90 mm). • Manageable by conventional HOM absorber Loss factor Ver.4 Loss factor [V/pC] Ver.6 Bunch length [mm] mm 12/10/2008 Y.Suetsugu

  22. a) Vacuum components And more for lower impedance: movable mask • Trial models were installed and tested with beam. • Principle was proved experimentally. • Temperature rise of bellows decreased to 1/2 ~ 1/3. • But, could not withstand a high intensity beam yet. • Start with Ver.4 ? • While beam current is low. Temperature of bellows near masks Head of Ver.6 (trial model) Beam Head Support mm 12/10/2008 Y.Suetsugu et.al

  23. a) Vacuum components Movable mask (beam test) • Principle was proved experimentally. • Improvement for high-current is currently underway Temperatures of bellows Temperatures of SiC cooling water Old type Old type New type New type mm 12/10/2008 Y.Suetsugu et.al

  24. a) Vacuum components And more for lower impedance:Connection flange MO-type flange, which can makes very smooth inner surface  low impedance SUS flange Flange and gasket (copper) Copper alloy flange (under test) mm 12/10/2008 Y.Suetsugu et.al

  25. a) Vacuum components Remaining Vacuum Issues • Optimization of beam duct shape • CSR (Coherent Synchrotron Radiation) problem have a great effect on the luminosity. • Deformation of beam duct by heating • Displacement gauge for every BPM? Larger aperture OR Smaller aperture Low impedance Cure for CSR (ex, resistive wall) (Low cost?) Effective pumping ? (f 50) (f 90) mm 12/10/2008 Y.Suetsugu et.al

  26. b) Modification of the monitors Modification of the monitors :Beam Position Monitors • Use same front-end electronics. • New button electrodes • New connector design for improved reliability. • 12 mm →6 mm diameter • Signal power same as at present, at higher beam currents, to match dynamic range of existing front-end electronics. mm 12/10/2008 M. Tejima et al.

  27. b) Modification of the monitors Modification of the monitors:Beam Size Monitors • Chamber redesign for high current. • Source bending radius for synchrotron radiation monitors increases 3x to reduce mirror heating at high currents. • Reduces beam image distortion at high currents. Also increases visible light flux. • Development of x-ray monitor also being pursued based on x-ray astronomy technique of Coded Aperture Imaging for high-bandwidth/high-speed readout with low beam current dependence. • Optics testing and detector development being carried out in collaboration with Cornell (CesrTA ILC damping ring study machine group) and U. Hawaii (Belle detector group). • Collaboration with other machines and between physics and accelerator groups. 1-D URA Mask for Coded Aperture Imaging mm 12/10/2008 J.Flanagan et.al

  28. c) Bunch-by-bunch FB system Bunch-by-bunch Feed back system • Transverse feedback similar to present design • →Target damping time 0.2ms • Detection frequency 2.0→2.5 GHz. • Transverse kicker needs work to handle higher currents • Improved cooling, supports for kicker plates. • Longitudinal feedback to handle ARES HOM & 0/p mode instability • →Target damping time 1ms • Use DAfNE-type (low-Q cavity) kicker. • Digital FIR and memory board to be replaced by new Gboard. • Low noise, high speed (1.5 GHz), with custom filtering functions possible. • Extensive beam diagnostics. A prototype of the new bunch-by-bunch feedback system (G-board / Gproto) has been developed as a result of collaboration between SLAC, KEK and INFN, and successfully tested at KEKB, KEK ATF, KEK PF, SLAC and DAFNE. mm 12/10/2008

  29. d & e ) RF system for higher currents RF systems Need RF systems which can store high beam currents and handle shorter bunches. ARES (normal-conducting cavity) for LER ARES + SCC (Single-cell Superconducting cavity) for HER Adopt the same RF frequency as KEKB and use the existing RF system as much as possible, with improvements as necessary to meet the requirements for SuperKEKB. →Construction cost is greatly reduced. →Technical uncertainties are relatively small. mm 12/10/2008 Akai et.al

  30. d & e ) RF system for higher currents The ARES Cavity Accelerator Resonantly-coupled Energy Storage • Passive stabilization with huge stored energy. • Eliminate unnecessary modes by coupling of 3 cavities. • Higher order mode dampers and absorbers. • No need for longitudinal bunch-by-bunch feedback. • No transverse instability arises from the cavities. Acceleration Resonant Storage mm 12/10/2008 T. Kageyama, et al

  31. d & e ) RF system for higher currents High power RF R&D • Higher HOM power Upgrade of HOM damper • Higher input RF power • 400 kW/cavity -> 800 kW/cavity • R&D of input coupler using new test-stand. mm 12/10/2008 Y. Takeuchi, T. Kageyama, et al

  32. d & e ) RF system for higher currents Superconducting Cavity SuperKEKB challenges: The expected power load to the HOM absorber is 50 kW/cavity at 4.1 A, (even) with a larger beam pipe of 220 mmφ. HOM damper upgrade may be needed. mm 12/10/2008 S. Mitsunobu, et al

  33. f) Crab cavity for higher currents Crab cavity with 10 A beam • The original cavity is designed for 1-2 A beam • Simple structure, suitable for SC → High kick voltage is obtained by one cavity. • Sufficient damping of parasitic modes. • Not necessarily optimized for a 10 A beam. • Possible problems at 10 A • Large HOM power (200 kW) • Loss factor is not very small, because the radius of coaxial beam pipe can not be widely opened. • Additional loss factor comes from the absorber on wide beam pipe. • Much heavier damping of HOM’s may be needed, particularly for horizontal polarization of transverse modes (large bx at crab). • A new crab cavity has been designed, which can be used at 10 A. mm 12/10/2008

  34. What we need IR & lattice design for smaller by* & larger xy mm 12/10/2008

  35. For smaller b* IR (Interaction Region) Higher luminosity⇨smaller b* causes issues such as mm 12/10/2008

  36. For smaller b* IR layout • Crossing angle: 22⇨30 mrad • Move final focus quadrupoles closer to IP for lower beta functions at IP. • Preserve current machine-detector boundary. • QCS and solenoid compensation magnets overlap in SuperKEKB. mm 12/10/2008

  37. For smaller b* IR-overview present design (based on the LoI) QCSR (QCSR center from IP = 1.163 m) KEKB=1.92 m QCSL (QCSL center from IP = 0.969 m) KEKB=1.6 m ESR IP The cryostats were designed with keeping the KEKB boundary conditions with Belle detector. ESL mm 12/10/2008 N.Ohuchi

  38. For smaller b* IR magnets (QCS) : Design • 6 layer coils (3-double pane cake coils) • Inner coil radius : 90.0 mm • Outer coil radius : 116.8 mm • Cable size : 1.1 mm  4.1 mm • 1.1 mm  7.0 mm (KEKB) • Number of turns : 271 in one pole • 1st layer = 38, 2nd layer = 39 • 3rd layer = 46, 4th layer = 47 • 5th layer = 50, 6th layer = 51 • Field gradient : 40.124 T/m • Magnet current : 1186.7 A • Magnetic length : 0.299m (R), 0.358m (L) • Inductance : 69.98 mH (R), 83.79 mH (L) • Stored energy : 49.3 kJ (R), 59.0 kJ (L) • Operation temperature : 4.5 K • Operation point w.r.t. SC limit : 75% (R), 74% (L) Cross section of QCSR mm 12/10/2008 N.Ohuchi

  39. For smaller b* IR magnets (QCS R&D) : Field measurement results • Field gradient at 1186.7A • G=40.05 T/m was obtained (Design G=40.124T/m) • Multipoles • Data at r=48mm • a3= -0.86 units, b3= 0.91 units • a4= -1.27 units, b4= 0.40 units • a5= 0.11 units, b5= -0.80 units • a6= -0.55 units, b6= -0.00 units （I units = 10-4 × b2） • Design at Rref= 50 mm • b6=0.12, b10=-0.04, b14=0.12 mm 12/10/2008 N.Ohuchi

  40. For smaller b* IR magnets (QC1&QC2) : R&D on coil winding Coil winding on a cone shaped bobbin R&D work required for a winding tool mm 12/10/2008 N.Ohuchi

  41. For smaller b* IR magnets (QCS) : 1.9K version for new optics QCS @ 1.9 K (design) IP 4 layer structure Integrated field gradient ＝17.445T field gradient ＝98.9 T/m⇦ needed for new IR Length ＝336mm Cable（the same type as QCS R&D 4.05mm×1.16mm） Current ＝2610A Max field inside the magnet ＝8.8T　（corresponds to 10T iron bore magnet） mm 12/10/2008 N.Ohuchi

  42. For smaller b* IR magnets (QCS) : 1.9K version for new optics to do list IR design has to be fixed. Design of Super-QC2 Design of compensation solenoids Optimization of QCS, QC2 and compensation solenoid under the combined operation Design of cryostats for 1.9K operation! mm 12/10/2008 N.Ohuchi

  43. For smaller b* Dynamic aperture Lattice Design Local chromaticity correction for widening dynamic aperture KEKB Design Report KEKB: local correction only in LER KEKB upgrade: local correction also in downstream of HER ⇨ New magnets need to be designed and made/measured/installed. Effects of local correction - widen dynamic aperture - weaken synchro-betatron resonance mm 12/10/2008

  44. Smaller b* Larger sz Hourglass effect Lattice DesignTravelling focus We would like to have sz ~ by* Bunch length limitation due to CSR LER bunch sz=5mm (not 3mm) when by*=3mm⇨sz > by* Hourglass effect is not negligible. ⇨A possible cure is to use the travel focusing Beam size changes along Z mm 12/10/2008

  45. Smaller b* Recovering from the hourglass effect Travelling focus Evaluation by Koiso-san Needs a pair of sextupole magnets at both sides of the crab cavity AND Two crab cavitieseach ring… More evaluation of the effect on the luminosity will be studied. (how much do we gain by this scheme?? Awfully expensive!) mm 12/10/2008

  46. For higher xy Lattice Designfor higher xy • Improving the performance with crab crossing is a must • Beam-beam parameter, beam lifetime ⇨Injecter upgrade • ⇨presentation by Funakoshi-san on KEKB status • Other efforts for higher xy are • Lower bx*, smaller ex, ey, smaller coupling ,,,, • ⇨Better magnet alignment • ⇨More auxiliary coils for optics diagnostics and correction mm 12/10/2008

  47. Injecter upgrade Simultaneous (pulse-by-pulse) injection of KEKB LER/HER/PF Injecter upgrade Crystal tungsten target f5 mm 4.5 mm Hole: f3 mm Simultaneous injection of e- and e+ is desirable in view of thermal stability of　components and an ability of the operation with shorter beam lifetime. Phase I : Construction of a new beam transport which bypasses the energy compression system (ECS). Phase II : Fast beam switch between KEKB e- and PF e- by a pulsed bend. Phase III : Fast beam switch between KEKB e-, PF e- and KEKB e+ by an e+ target with a hole and pulsed steerings. Phase I and II have been completed. Beam study for Phase III is underway. Phase III will be started in this autumn. PF e- Gun (A1 Gun; for KEKB and PF) #3 Switchyard e- Gun (CT Gun; for PF-AR） KEKB/ AR pulsed Bend ECS Positron Target mm 12/10/2008 (M. Satoh, KEKB review committee 2007)

  48. Injecter upgrade Injecter upgrade Simultaneous injection of KEKB LER/HER/PF On Dec.8, 2008 First pulse-by-pulse injection to PF & KEKB HER! PF / 5Hz HER / 12.5Hz mm 12/10/2008 N.Iida

  49. Better magnet alignment For higher xy KEKB tunnel continues to sink and magnets follow the tunnel Tunnel level Magnet level 2004 data Measurement data were used as alignment errors and simulation was done by Ohnishi. No need for leveling the tunnel but local ups and downs better be corrected. We also found that the magnets are rotated, horizontal position moved and so on… mm 12/10/2008

  50. Summary Accelerator components R&D work of the accelerator components (vacuum, monitors and etc) is ongoing. Some have been tested with the beam. IR optics IR optics is being re-designed with bx=20 cm ⇨Koiso-san’s talk on the new IR optics parallel session tomorrow. IR magnets QCS R&D version has been made and its magnetic field has been measured. IR magnets (QCS,QC1 and QC2) will all be superconducting. Evaluation of QCS at 1.9K shows a possibility of higher field gradient which is needed for the new IR optics with smaller bx. ⇨New cryostat for 1.9K needs to be designed. mm 12/10/2008

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