Slide 1

Status of the accelerator upgrade Dec.10 2008 Mika Masuzawa mm 12/10/2008 Slide 2 Contents 1.Introduction Luminosity goal 2.Strategy Higher currents Smaller y * Increase y 3.What we need Components for higher currents R&D Status IR & Lattice design for smaller y * & larger y 4.Summary mm 12/10/2008 Slide 3 1.Introduction Luminosity goal mm 12/10/2008 Slide 4 Luminosity goal mm 12/10/2008 Slide 5 Target: 5-8 10 35 cm -2 s -1 =30-50 x World Record (KEKB) mm 12/10/2008 Slide 6 2.Strategy mm 12/10/2008 Slide 7 Strategy (1) Increase beam currents 1.7 A (LER) / 1.4 A (HER) 9.6 A (LER) / 4.1 A (HER) (2) Smaller y * 6.5(LER)/5.9(HER) mm3.0/3.0 mm (3) Increase y 0.09 (with Crab) 0.29 mm 12/10/2008 Slide 8 Crab cavity The superconducting cavities will be upgraded to absorb more higher- order mode power up to 50 kW. The beam pipes and all vacuum components will be replaced with higher-current design. The state-of-art ARES copper cavities will be upgraded with higher energy storage ratio to support higher current. SuperKEKB e- 4.1 A e+ 9.4 A * y = z = 3 mm Will reach 5-8 10 35 cm -2 s -1. Tunnel already exists. Most of the components (magnets, klystrons,etc) will be re-used. Slide 9 Comparison of parameters KEKB Design (A) KEKB (achieved) KEKB upgrade (B) Gain Factor (B/A) y * (mm) 10 5.9/6.5 (5.9/5.9) 33.3 yy 0.0520.056 (0.093)0.296 RyRy 0.8850.879(1.15)1.11 y /R y 0.0590.063(0.081)0.2674.5 I beam (H/L) (A)1.1/2.6 1.45/1.8 (0.95/1.62) 4.1/9.43.6 RLRL 0.845 0.715(0.827)0.861.02 Luminosity (10 34 cm -2 s -1 ) 11.71 (1.46)55 z (mm) 4~ 75(LER)/3(HER) mm 12/10/2008 ( ): with crab Strategy Slide 10 3.What we need Components for higher currents R&D Status mm 12/10/2008 Slide 11 What we need for (1) higher beam currents mm 12/10/2008 a. Vacuum components (pipes/bellows) b. Modification of the monitors (BPMs,SRMs) c. Longitudinal bunch-by-bunch FB system d. More RF cavities and klystrons e. Modifications of the RF systems for higher currents f. New Crab cavities for SuperKEKB Slide 12 Vacuum components talk by K.Shibata tomorrow mm 12/10/2008 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 ~1x10 19 photons/m/s in average Large gas desorption Gas load ~ 5x10 -8 Pa m 3 /s/m (for h = 1x10 -6 molecules/photon) Average pressure ~ 5x10 -7 Pa for S ~ 0.1 m 3 /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 a) Vacuum components Slide 13 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 mm 12/10/2008 Beam SR Pump LER HER Y.Suetsugu a) Vacuum components Some sections of KEKB LER have been replaced by ante-chamber type Slide 14 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 a) Vacuum components Slide 15 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. mm 12/10/2008 ~4 m 90 mm Electron numbers Y.Suetsugu a) Vacuum components Slide 16 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. mm 12/10/2008 Clearing electrode for test Electron Current [A] Applied voltage [V] V r = 1.0 kV B = 0.77 T V elec [V] I e [A] 1585 bunches (B s ~ 6 ns) ~1600 mA V elec = 0 V -500 V +500 V 1 x 10 -5 1 x 10 -6 1 x 10 -7 1 x 10 -8 1 x 10 -9 Collectors Y.Suetsugu a) Vacuum components Drift space In wiggler magnet Slide 17 And more on suppressing photoelectrons Grooved Surface: being tested with the beam now. Another possible measure in magnets Decrease effective SEY structurally TiN~50 nm SS + TiN coating M. Pivi mm 12/10/2008 Y.Suetsugu et.al a) Vacuum components Slide 18 Grooved surface currently tested mm 12/10/2008 a) Vacuum components Slide 19 For lower impedance: RF shielding Comb-type RF shield 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. Without cooling fan Comb-type RF-shield Temperature of bellows a) Vacuum components mm 12/10/2008 Y.Suetsugu Slide 20 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 Y.Suetsugu et.al a) Vacuum components mm 12/10/2008 Slide 21 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 ( 90 mm) 200 kW power loss Loss factor decreases to ~1/10 ( 90 mm). Manageable by conventional HOM absorber Loss factor Bunch length [mm] Loss factor [V/pC] Ver.4 Ver.6 a) Vacuum components mm 12/10/2008 Y.Suetsugu Slide 22 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. Head of Ver.6 (trial model) Temperature of bellows near masks Beam Head Support Y.Suetsugu et.al a) Vacuum components mm 12/10/2008 Slide 23 Movable mask (beam test) Principle was proved experimentally. Improvement for high-current is currently underway Temperatures of bellowsTemperatures of SiC cooling water Old type New type Old type New type Y.Suetsugu et.al a) Vacuum components mm 12/10/2008 Slide 24 And more for lower impedance:Connection flange MO-type flange, which can makes very smooth inner surface low impedance SUS flange Copper alloy flange (under test) Flange and gasket (copper) Y.Suetsugu et.al a) Vacuum components mm 12/10/2008 Slide 25 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? ( 50) Larger aperture OR Smaller aperture Low impedance Cure for CSR (ex, resistive wall) (Low cost?) Effective pumping ( 90) ? Y.Suetsugu et.al a) Vacuum components mm 12/10/2008 Slide 26 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. M. Tejima et al. b) Modification of the monitors mm 12/10/2008 Slide 27 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 J.Flanagan et.al b) Modification of the monitors mm 12/10/2008 Slide 28 Bunch-by-bunch Feed back system mm 12/10/2008 Transverse feedback similar to present design Target damping time 0.2ms -Detection frequency 2.02.5 GHz. -Transverse kicker needs work to handle higher currents -Improved cooling, supports for kicker plates. Longitudinal feedback to handle ARES HOM & 0/ mode instability Target damping time 1ms -Use DA NE-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 DA NE. c) Bunch-by-bunch FB system Slide 29 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. d & e ) RF system for higher currents mm 12/10/2008 Akai et.al Slide 30 The ARES Cavity 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. Storage Resonant Acceleration Accelerator Resonantly-coupled Energy Storage T. Kageyama, et al d & e ) RF system for higher currents mm 12/10/2008 Slide 31 High power RF R&D Y. Takeuchi, T. Kageyama, et al d & e ) RF system for higher currents mm 12/10/2008 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. Slide 32 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 mm. HOM damper upgrade may be needed. S. Mitsunobu, et al d & e ) RF system for higher currents mm 12/10/2008 Slide 33 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 HOMs may be needed, particularly for horizontal polarization of transverse modes (large x at crab). A new crab cavity has been designed, which can be used at 10 A. f) Crab cavity for higher currents Slide 34 3.What we need IR & lattice design for smaller y * & larger y mm 12/10/2008 Slide 35 IR (Interaction Region) mm 12/10/2008 IssuesCausesPossible cures Physical aperture Lower * Injection beam quality (Damping ring) Dynamic aperture Lower * Injection beam quality (Damping ring) Move the IR magnets closer to IP needs stronger magnets Local correction at the IR straight section in HER Detector backgroundHigher beam currentOptimization of mask, IP beam duct shape etc. talk by M.Iwasaki Heating of componentsHigher beam current & shorter bunch length Optimization of the IP beam duct, cooling systems etc. For smaller * Higher luminosity smaller * causes issues such as Slide 36 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 For smaller * Slide 37 mm 12/10/2008 IR-overview present design (based on the LoI) QCSL (QCSL center from IP = 0.969 m) KEKB=1.6 m QCSR (QCSR center from IP = 1.163 m) KEKB=1.92 m ESR ESL IP The cryostats were designed with keeping the KEKB boundary conditions with Belle detector. N.Ohuchi For smaller * Slide 38 mm 12/10/2008 Cross section of QCSR 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) N.Ohuchi IR magnets (QCS) : Design For smaller * Slide 39 IR magnets (QCS R&D) : Field measurement results mm 12/10/2008 Field gradient at 1186.7A G=40.05 T/m was obtained (Design G=40.124T/m) Multipoles Data at r=48mm a 3 = -0.86 units, b 3 = 0.91 units a 4 = -1.27 units, b 4 = 0.40 units a 5 = 0.11 units, b 5 = -0.80 units a 6 = -0.55 units, b 6 = -0.00 units I units = 10 -4 b 2 Design at R ref = 50 mm b 6 =0.12, b 10 =-0.04, b 14 =0.12 N.Ohuchi For smaller * Slide 40 IR magnets (QC1&QC2) : R&D on coil winding mm 12/10/2008 Coil winding on a cone shaped bobbin R&D work required for a winding tool N.Ohuchi For smaller * Slide 41 mm 12/10/2008 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 4.05mm1.16mm Current 2610A Max field inside the magnet 8.8T corresponds to 10T iron bore magnet N.Ohuchi QCS @ 1.9 K (design) IR magnets (QCS) : 1.9K version for new optics For smaller * Slide 42 mm 12/10/2008 IR magnets (QCS) : 1.9K version for new optics to do list 1.IR design has to be fixed. 2.Design of Super-QC2 3.Design of compensation solenoids 4.Optimization of QCS, QC2 and compensation solenoid under the combined operation 5.Design of cryostats for 1.9K operation! N.Ohuchi For smaller * Slide 43 Local chromaticity correction for widening dynamic aperture KEKB Design Report Effects of local correction - widen dynamic aperture - weaken synchro-betatron resonance 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. Lattice Design mm 12/10/2008 For smaller * Dynamic aperture Slide 44 Lattice Design Travelling focus mm 12/10/2008 We would like to have z ~ y * Bunch length limitation due to CSR LER bunch z =5mm (not 3mm) when y * =3mm z > y * Hourglass effect is not negligible. A possible cure is to use the travel focusing Beam size changes along Z Smaller * Larger z Hourglass effect Slide 45 Travelling focus mm 12/10/2008 Evaluation by Koiso-san Needs a pair of sextupole magnets at both sides of the crab cavity AND Two crab cavities each ring More evaluation of the effect on the luminosity will be studied. (how much do we gain by this scheme?? Awfully expensive!) Smaller * Recovering from the hourglass effect Slide 46 Lattice Design for higher y KEKBKEKB upgrade y (max) with crab from b-b simulation 0.150.296 x * [m] 0.90.2 x (LER/HER) [nm] 18/2412/13 y / x [%] 10.5 x (LER/HER) 0.506/0.5100.505/0.505 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 y are Lower x *, smaller x, y, smaller coupling,,,, Better magnet alignment More auxiliary coils for optics diagnostics and correction mm 12/10/2008 For higher y Slide 47 Injecter upgrade Simultaneous (pulse-by-pulse) injection of KEKB LER/HER/PF 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. e- Gun (A1 Gun; for KEKB and PF) e- Gun (CT Gun; for PF- AR #3 Switchyard KEKB/ AR PF pulsed Bend ECS Crystal tungsten target 5 mm Hole: 3 mm 4.5 mm Phase I and II have been completed. Beam study for Phase III is underway. Phase III will be started in this autumn. 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. (M. Satoh, KEKB review committee 2007) Positron Target mm 12/10/2008 Injecter upgrade Slide 48 HER / 12.5HzPF / 5Hz N.Iida On Dec.8, 2008 First pulse-by-pulse injection to PF & KEKB HER! mm 12/10/2008 Injecter upgrade Simultaneous injection of KEKB LER/HER/PF Injecter upgrade Slide 49 mm 12/10/2008 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 Tunnel level Magnet level KEKB tunnel continues to sink and magnets follow the tunnel Better magnet alignment For higher y Slide 50 Summary mm 12/10/2008 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 x=20 cm Koiso-sans 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 x. New cryostat for 1.9K needs to be designed. Slide 51 Summary mm 12/10/2008 Lattice design Bunch length of HER 3 mm/LER 5 mm (due to CSR) is the current choice. Hourglass effect will degrade the luminosity. Travelling focus? Effect of travelling focus needs to be examined. Better alignment Magnet rotation/level measurement data have been taken and machine performance is simulated. Realignment (smoothing locally) will be needed though a leveling of the entire tunnel may not be necessary. We are making steady progress toward 5-8 10 35 cm -2 s -1. Slide 52 mm 12/10/2008 Contribution is welcome.