LINAC Upgrade Status Takako Miura Kazuro Furukawa Accelerator

LINAC Upgrade Status Takako Miura / Kazuro Furukawa (Accelerator Laboratory, KEK) on behalf of Injector LINAC group B 2 GM 26 -Jun-2015 T. Miura 1

Injector LINAC High-current and low-emittance injection beams are required for Super. KEKB. The LINAC has been upgraded for Super. KEKB, and beam commissioning has been performed during the upgrading. LINAC Beam Parameters for KEKB for Super. KEKB Energy e+ e- 3. 5 Ge. V 8. 0 Ge. V 4. 0 Ge. V 7. 0 Ge. V Primary e-10 n. C Bunch charge → 1 n. C Primary e-10 n. C 1 n. C → 4 n. C 5 n. C Norm. Emittance ( ) 2100 (mm mrad) 100/20 (Hor. /Ver. ) (mm mrad) 50/20 (Hor. /Ver. ) (mm mrad) Energy spread 0. 125% 0. 1% Num. of Bunch / Pulse 2 2 Repetition rate Simultaneous top-up injection 50 Hz 3 rings (KEKB e-/e+, PF) B 2 GM 26 -Jun-2015 50 Hz T. Miura 4 rings (Super. KEKB e-/e+, PF-AR) 2

Schedule Super. KEKB commissioning is divided into three stages. (phase 1, phase 2, phase 3) Calendar 2015 2016 Power restriction in summer Current plan on going 2017 Power restriction in summer Phase 1 Power restriction in summer Phase 3 Phase 2 w/o QCS, Belle II install w/o Belle II Vacuum Scrubbing Basic machine tuning Current=1 A 2018 VXD install w/ QCS w/ Belle II (no VXD) L= 1 1034 cm-2 s-1 (KEKB design) w/o DR no Top-up inj. L= 8 1035 cm-2 s-1 Full Current Injection Beam low emittance 2 n. C/bunch 1 n. C/bunch Add more RF w/ full Belle II w/ DR DR commissioning Top-up injection B 2 GM 26 -Jun-2015 T. Miura low emittance 4~5 n. C/bunch w/ DR Top-up injection 3

Major Upgrades of Injector LINAC Photo-cathode RF gun system < e- beam> Low emittance ( 20 mm mrad) high bunch charge ( 5 n. C) Positron Damping Ring (DR) Low emittance e+ beam Alignment error tolerance 1. 1 Ge. V e+ Damping Ring circ. 136 m RF gun Thermionic gun (10 n. C primary e-) 1. 5 Ge. V 3. 5 Ge. V 10 n. C x 2 (prim. e-) 5 n. C x 2 (inj. e-) e+ target Positron Capture Section - Flux concentrator (FC) - Large aperture S-band accel. Structures (LAS) 4 times higher e+ yield (local)=0. 1 mm (global)=0. 3 mm Low emittance preservation BCS ECS PF ECS chicane Pulsed Quads & Pulsed Steering Magnets PF-AR HER LER Event Timing System and Pulsed Modules • Synchronization for 5 -rings including DR • 200 parameters are switched at 50 Hz each mode • Optics at the downstream of DR is switched by using pulsed magnets B 2 GM 26 -Jun-2015 T. Miura 4

Layout of Electron Guns Ø Thermionic electron gun are located upstairs to produce ~10 n. C primary electrons for positron production. Ø Photocathode RF gun for low emittance e- production is located on the Thermionic gun straight line. (primary e- 10 n. C) Merger line 5 Photocathode RF gun Thermionic gun: commissioning was started from June 2015. B 2 GM 26 -Jun-2015 T. Miura 5

Quasi Traveling Wave Side Couple RF GUN Strong focusing force using accelerating field Quasi traveling wave (QTW) side couple RF gun Installed in sept. 2013. 90 deg Hybrid Ir 5 Ce Cathode 0 deg. be am RF 90 deg. QE=1× 10 -4 @266 nm Long lifetime Laser Port QTW type is adopted to make drift space short. Drift space = no focus field Incident angle: 60 deg to the cathode surface. 7 cell, 13. 5 Me. V@design Emittance: 5. 5 mm-mrad @5 n. C (by simulation) This RF gun can generate e- up to 10 n. C Beam QTW is made by two standing waves with 90 deg phase difference. coupling cavities B 2 GM 26 -Jun-2015 T. Miura T. Natsui, M. Yoshida 6

Yb: YAG/Nd: YAG Laser System for RF-Gun Yb: YAG (1025 -1070 nm) broad band →Pulse shape manipulation is possible. Stretcher Yb Oscilattor 100 fs Yb PCF Amplifier Yb: YAG thin-disk Amplifier SHG 30 ps 0. 2 n. J @ 1025 -1070 nm Yb-doped fiber pre amplifier Yb-doped fiber oscillator 51. 9 MHz 30 ps EO Pulse picker Synchronizatio n system PCF: Photonic-crystal fiber 2856 MHz trigger From Accelerator ~ μJ Yb: YAG thindisk multi-pass amplifier PCF Yb-doped fiber amplifier ~0. 8 m. J @ 258 nm X. Zhou, M. Yoshida, T. Natsui RF GUN Yb-doped fiber amplifier @1035 nm PCF Yb-doped fiber amplifier 25 Hz Double bunch @1064 nm Transmission Grating Stretcher Nd: YAG solidstate amplifier Yb: YAG thindisk multi-pass amplifier 2 bunch, 25 Hz achieved (limited by thermal effect) Final goal is 50 Hz. ~5 m. J SHG SHG: Second harmonic generator BBO B 2 GM 26 -Jun-2015 T. Miura 7

Beam Commissioning of RF Gun Operation Condition • Laser: 2 bunch, 25 Hz • RF gun acc. voltage: limited to 6. 5 MV by breakdown (13. 5 MV@design) Bunch charge just after RF GUN (A 1_C 5) Target : 5 n. C x=50 mm mrad, y=20 mm mrad @ LINAC end x , y = 10 mm mrad @ Gun Emittance measurement by Quad-scan (m) 1 week RF GUN 4 n. C/bunch Sort for 3 h (Y, M, D) Screen monitor (t=30 m) Bunch charge: 3 n. C@Screen Beam size was measured shot by shot. => Position jitter is not included x=49. 2 mm mrad 10% y=26. 2 mm mrad 10% Archived 1/10 s Bunch charge stability depends on the laser stability. Yb: YAG Thin-disk cooling by soldering Cu plate was Improved. R. Zhang, TUPWA 071 Laser power increased and stability was also improving. Ø Measured emittances were higher than target values. Ø Higher horizontal emittance is due to laser incident angle. Need high acc. voltage of RF gun for small emittance B 2 GM 26 -Jun-2015 T. Miura 8

Beam Commissioning of Thermionic e- Gun Linac A 1(QFE) e-/e+ Orbit to LTR dump B 2 GM 26 -Jun-2015 T. Miura 9

Positron Capture Section T. Kamitani, L. Zang 0. 5 T DC solenoids : 15 m FC : Flux concentrator Large energy acceptance DC solenoid LAS : Large aperture S-band accel. Structures Aperture 20 mm 30 mm Large transverse acceptance Solenoid field at e+ production target = 3. 5 T(FC)+1 T(Bridge coil) = 4. 5 T FC viewed from downstream LAS + DC solenoid (15 m) 3. 5 T@12 k. A, 6 s (half sine) FC/Target e 2. 0 mm Hole on-axis Target off-axis B 2 GM 26 -Jun-2015 T. Miura May 2014 installed 10

Positron beam commissioning @June 2014 Design 6/2014 Flux Concentrator 12 k. A 6. 4 k. A Bridge Coil 600 A DC Solenoids 650 A 370 A 14, 12 MV/m 10, 12 MV/m Acc Field orbit-X [mm] T. Kamitani B A C e 1 Q(e+) = 0. 18 n. C at capture section end orbit-Y [mm] Charge [n. C] 2 target Positron Ye+ > 40 % is necessary at DR entrance. June 2014 Q(e+) = 0. 12 n. C Primary eintensity at target Q(e-) = 0. 60 n. C Primary Electron e+ Commissioning with design parameters will be started from Oct. 2015. So far, the commissioning data agrees the design well e+ yield (Ye+) = e+ charge (Qe+) / primary e- charge (Qe-) Ye+@Jun. 2014 = 30 % at capture section end, 20% at the end of Sector 2 with limited ele/mag fields B 2 GM 26 -Jun-2015 T. Miura 11

Radiation shield for higher beam current #15 region Iron shield Gradual increase of beam current / shield and corresponding radiation license applications are planned B 2 GM 26 -Jun-2015 T. Miura 12

Summary • Steady progress towards first MR injection in JFY 2015 • Finished earthquake disaster recovery in JFY 2014 • Will make gradual improvements up to Phase-III • Alignment: almost confident on the required precision (0. 1 mm local, 0. 3 -mm global), need to maintain for longer term • RF gun: following recommendations at review meetings with commercial devices and Nd-based lasers • Thermionic gun: under commissioning • Positron generator: waiting for license tests Thank you for your attention. • Will balance between final beam quality and operation in phases • Will select optimized route depending on available resources B 2 GM 26 -Jun-2015 T. Miura 13

Mt. Tsukuba Thank you Super. KEKB dual rings PF-AR PF 14 Injector Linac

Back-up slides B 2 GM 26 -Jun-2015 T. Miura 15

Why need longitudinal pulse-shape manipulation? Energy spread of 0. 1% is required for Super. KEKB synchrotron injection. 15 n. C t 5 n. C 10 n. C 20 n. C Energy Spread Gaussian t Square Requirement 5 n. C electron Pulse length 5 n. C 10 n. C 15 n. C 20 n. C M. Yoshida 16

J-ARC Alignment Requirement 120 m B A C Rings 1 2 500 m 3 4 5 < 0. 1 mm: 20 mm·mrad is almost satisfied. > 0. 1 mm: emittance preservation is required by some methods. Requirement Local s < 0. 1 mm Global s < 0. 3 mm H. Sugimoto 17

Hard ware alignment on a girders in sector 3 - 5 Horizontal Vertical Horizontal =34 m Vertical =47 m T. Higo 2015/2/24 May/5/2015 KEK Review Higo IPAC 2015 Takako Miura 18 18

Floor Movement in a Half Year straight laser of 500 m + Position Detector (PD) T. Suwada At expansion joint in tunnel, large movement is observed. 4 -segmented silicon PD (dia. =10 mm) T. Higo 19

Expected e+ Yield improvement Ne+/Ne- @ capture section end At the entrance of LER, 4 n. C e+ is necessary for 10 n. C primary e-. measurement 2014 June simulation T. Kamitani, F. Miyahara Designed yield at capture section end By raising DC Solenoid field FC field and acceleration field, 2014 -June FC 6. 4 k. A BC 600 A DCS 370 A Acc 10, 12 MV/m FC 6. 4 k. A BC 600 A DCS 650 A Acc 10, 12 MV/m FC 12 k. A BC 600 A DCS 650 A Acc 14, 12 MV/m 2. 7 times Improvement expected. Start from Oct. 2015 20

LINAC Beam Acceleration Scheme 1. 1 Ge. V Damping Ring circ. 136 m Low emittance RF gun 1. 5 Ge. V 3. 5 Ge. V 10 n. C x 2 (prim. e-) 5 n. C x 2 (inj. e-) e-/e+ beam with different bunch charge and energy are accelerated by 50 Hz repetition rate. BCS ECS 3 T RF gun e+ target & LAS capture section chicane PF ECS PF-AR HER LER 5 n. C x 2 HER: 7 Ge. V e. PF-AR: 6. 5 Ge. V e- 4. 219 Ge. V 5 n. Cx 1 e- LER: 4 Ge. V e+ 4 n. Cx 2 e+ target 1. 5 Ge. V e+ PF: 2. 5 Ge. V e- 1. 1 Ge. V e-/e+ compatible optics 0. 1 n. Cx 1 Optics is changed for each pulse by using pulsed quads (Doublet) & steering magnets B 2 GM 26 -Jun-2015 T. Miura 21

Injector LINAC The upgrade construction toward Super. KEKB has been started from 2010. High-current and low-emittance injection beams are required for Super. KEKB. Upgrade of injector LINAC for Super. KEKB is in progress. Belle II e+ HER : e 7 Ge. V, 2. 6 A e- LER : e+ 4 Ge. V, 3. 6 A Super. KEKB Circumference : 3 km STF Injector LINAC 600 m PF-AR PF LINAC Provides: LER: 4 Ge. V e+ HER: 7 Ge. V e. PF: 2. 5 Ge. V e. PF-AR: 6. 5 Ge. V e- 4 n. C 2 5 n. C 2 0. 3 n. C 1 5 n. C 1 e+ Damping Ring newly constructed LINAC is the injector four storage rings (LER, HER, PF, and PF-AR). The pulse by pulse beam mode switching in 50 Hz which is repetition rate of the LINAC is necessary for top-up injections into these four rings. B 2 GM 26 -Jun-2015 T. Miura 22

Beam Lifetime Y. Funakoshi KEKB (design) KEKB (operation) Super. KEKB Design LER HER Radiative Bhabha 21. 3 h 9. 0 h 6. 6 h 4. 5 h 28 min. 20 min. Beam-gas 45 ha) 24. 5 min. b) 46 min. b) Touschek 10 h - 10 min. Total 5. 9 h 7. 4 h ~2. 2 h ~3. 3 h 6 min. c) Beam current 2. 6 A 1. 1 A 1. 6 A 1. 1 A 3. 6 A 2. 6 A 0. 12 m. A/s 0. 04 m. A/s 0. 23 m. A/s 0. 11 m. A/s 10 m. A/s 7. 2 m. A/s Loss Rate a) Bremsstrahlung b) Coulomb scattering, sensitive to collimator setting c) w/o beam-beam effect Revolution freq~100 k. Hz For compensation of the particle loss Low emittance and high current injection beams are necessary. 4 n. C@25 Hz 2. 9 n. C@25 Hz injection rate are required. LINAC is a key component of Super. KEKB. May/5/2015 IPAC 2015 Takako Miura 23

LINAC Beam Parameters for KEKB Energy for Super. KEKB e+ e- 3. 5 Ge. V 8. 0 Ge. V 4. 0 Ge. V 7. 0 Ge. V Primary e-10 n. C Bunch charge → 1 n. C Primary e-10 n. C 1 n. C → 4 n. C 5 n. C Num. of Bunch / Pulse 2 2 Norm. Emittance ( ) 2100 (mm mrad) 100/20 (Hor. /Ver. ) (mm mrad) 50/20 (Hor. /Ver. ) (mm mrad) Energy spread 0. 125% 0. 1% Repetition rate 50 Hz 0. 3 n. C 1 5 n. C 2 4 n. C 2 May/5/2015 50 Hz Beam modes are switched in pulse to pulse for 5 -rings including Damping Ring (DR). IPAC 2015 Takako Miura 24

High charge and low emittance are required for Super. KEKB e+ e- 3. 5 8. 0 4. 0 7. 0 Bunch charge (n. C) 1 1 4 5 Norm. Emittance ( ) (mm mrad) 2100 100 (H) / 20 (V) 50 (H) / 20 (V) Energy spread (%) 0. 125 0. 1 Energy (Ge. V) B 2 GM 26 -Jun-2015 T. Miura 25