Overview of Electron/Positron Injector Linac Upgrades at KEK

The recent status of the Electron/Positron Injector Linac at KEK, presented by Kazuro Furukawa, highlights the mission to achieve 40 times higher luminosity in the SuperKEKB collider. The upgrades include low emittance, low energy spread injection beams with higher beam current, new high-current photo cathode RF gun, positron capture section, and optimized beam optics. The injector linac is designed for balanced injection for both photon science and elementary particle physics experiments, with precise beam orbit control and simultaneous top-up injection to multiple storage rings. Key upgrade items include the photo-cathode RF gun, pulsed magnets, and high-precision beam position monitors for achieving low emittance and high beam quality.

• Electron/Positron Injector Linac
• KEK
• SuperKEKB collider
• Upgrades
• Beam Quality

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1. Recent Status Recent Status of of Electron/Positron Injector Linac Electron/Positron Injector Linac Kazuro Furukawa Kazuro Furukawa for Injector for Injector Linac, Linac, KEK KEK Many slides from Y. Enomoto and S. Matsumoto Many slides from Y. Enomoto and S. Matsumoto Injector Linac Status K.Furukawa, B2GM, Feb.2018 1

2. Injector Linac Mission Mission of Electron/positron Injector in SuperKEKB Mission of Electron/positron Injector in SuperKEKB For 40 For 40- -times higher luminosity in SuperKEKB collider times higher luminosity in SuperKEKB collider Low emittance & low Low emittance & low e energy spread injection beam with 4 nergy spread injection beam with 4- -5 times higher beam current New high New high- -current photo current photo- -cathode RF gun cathode RF gun New positron capture section New positron capture section Damping ring construction Damping ring construction Optimized beam optics and correction Optimized beam optics and correction Precise beam orbit control with Precise beam orbit control with l long ong- -baseline alignment baseline alignment Simultaneous top Simultaneous top- -up injection to DR/HER/LER/PF/PFAR up injection to DR/HER/LER/PF/PFAR Balanced injection for the both photon science and Balanced injection for the both photon science and elementary particle physics experiments elementary particle physics experiments 5 times higher beam current The single injector would behave as multiple injectors to multiple storage rings by the concept of virtual accelerator Injector Linac Status K.Furukawa, B2GM, Feb.2018 2

3. Injector Linac Overview Injector Linac Overview Injector linac configuration Injector linac configuration Major upgrade items Major upgrade items Photo Photo- -cathode RF cathode RF- -gun for low Flux concentrator, LAS structure, solenoids, quads for e+ Flux concentrator, LAS structure, solenoids, quads for e+ Pulsed magnets for adequate beam optics for each beam Pulsed magnets for adequate beam optics for each beam High High- -precision beam position monitor precision beam position monitor High High- -precision beamline alignment for low emittance precision beamline alignment for low emittance gun for low- -emittance e emittance e- - Injector Linac Status K.Furukawa, B2GM, Feb.2018 3

4. Linac Beam Property Requirements Required injector beam parameters Required injector beam parameters SuperKEKB (final) Stage KEKB (final) Phase-I Phase-II e+ e e+ e e+ e e+ e Beam Energy 3.5 GeV 8.0 GeV 4.0 GeV 7.0 GeV 4.0 GeV 7.0 GeV 4.0 GeV 7.0 GeV Stored current 1.6 A 1.1 A 1 A 1 A 3.6 A 2.6 A Life time (min.) 150 200 100 100 6 6 primary e- 10 1 primary e- 8 0.4 primary e- 10 4 1 0.5 1 4 Bunch charge (nC) 1 Norm. Emittance ( ) ( rad) 200/40 (Hor./Ver.) 100/15 (Hor./Ver.) 40/20 (Hor./Ver.) 1400 310 1000 130 150 Energy spread 0.125% 0.125% 0.5% 0.5% 0.16% 0.1% 0.16% 0.07% Bunch / Pulse 2 2 2 2 2 2 2 2 Repetition rate 50 Hz 25 Hz 25 Hz 50 Hz Simultaneous top- up injection (PPM) 3 rings 4+1 rings (LER, HER, DR, PF, PF-AR) No top-up Eventually (LER, HER, PF) Injector Linac Status K.Furukawa, B2GM, Feb.2018 4

5. New Schedule Linac Schedule Overview Linac Schedule Overview as of Feb.2018 e e- - commiss. commiss. at A,B at A,B,R, ,R,C,1 C,1 at 1,2 sector at 1,2 sector (FC, DCS, Qe (FC, DCS, Qe- - 50%) e e- - commiss. commiss. at 1,2,3,4,5 sector at 1,2,3,4,5 sector as of Feb.2018 e+ e+ commiss. commiss. RF RF- -Gun Gun e e- - beam commissioning commissioning at A,B at A,B- -sector sector beam Phase1: high emittance beam for vacuum scrub Phase2,3: low emittance beam for collision 50%) Time Time Location Location Beam Beam Licenses Licenses in steps in steps Low Low Low Low 4+1 Ring 4+1 Ring Injections Injections Emittance Emittance Beams Beams Emittance Emittance Injections Injections DR DR Commiss. Commiss. 1 nC 1 nC Phase1 Phase1 1 1 - - 2 2 nC Phase2 Phase2 nC 2 2 - - 4 4 nC Phase3 Phase3 nC Without Top Without Top- -up up Direct PF Direct PF- -AR BT AR BT damped e+ damped e+ commiss. at 1 at 1 5 5 Qe+ = 1~4nC Qe+ = 1~4nC e e- - commiss. commiss. at A at A 5 5 Qe Qe- - = 1 commiss. Improved Improved RF gun RF gun non damped e+ non damped e+ commiss. at 1,2, at 1,2, 3,4,5 3,4,5 sectors sectors e e- - commiss. commiss. at A commiss. : Electron : Electron : Positron : Positron : Low current electron : Low current electron at A 5 sectors 5 sectors = 1~4nC ~4nC Injector Linac Status K.Furukawa, B2GM, Feb.2018 5

6. Newly Installed Pulsed Magnets Newly Installed Pulsed Magnets Common optics was enough KEKB KEKB Independent beam optics with 26 Quads and 26 Correctors in Sectors 3 5 10 Correctors in Sectors 1 and 2 2 Quads for Positron Target SuperKEKB SuperKEKB HER (7 GeV) PF-AR (6.5 GeV) Beam energy LER (4 GeV) PF (2.5 GeV) A A B B C C 1 1 Sector 2 2 3 3 4 4 5 5 Injector Linac Status K.Furukawa, B2GM, Feb.2018 6

7. Pulsed Magnet Installation Pulsed Magnet Installation 1 1 Installation during long Installation during long shutdown at summer 2017 shutdown at summer 2017 Not possible before Phase 1 Not possible before Phase 1 without DR because of the without DR because of the aperture aperture Replacement for 64 magnets Replacement for 64 magnets In 99 days between May and In 99 days between May and October October All components including All components including magnets, girders, cabling, magnets, girders, cabling, cooling water, controls, etc. cooling water, controls, etc. In parallel with other In parallel with other replacements and installations replacements and installations K.Furukawa, B2GM, Feb.2018 2017/3/31 by N.Toge Injector Linac Status 7

8. Pulsed Magnet Installation Pulsed Magnet Installation 2 2 13 New girders 13 New girders each for 2 quads and 2 correctors each for 2 quads and 2 correctors ready for 10 ready for 10 m m alignment to realize low emittance preservation alignment to realize low emittance preservation in Phase 3 in Phase 3 Injector Linac Status K.Furukawa, B2GM, Feb.2018 8

9. Pulsed Magnet Installation Pulsed Magnet Installation 3 3 Standard cabinet configuration for pulsed magnets 4 quads and 4 correctors for a half sector Pulsed power supplies & Interlock system for 2 quads and 2 correctors Pulsed power supplies & Interlock system for 2 quads and 2 correctors Controls Girder and magnet replacements before July Power supply installation and cabling before September Comprehensive system tests in September for a month Injector Linac Status K.Furukawa, B2GM, Feb.2018 9

10. Performance of Quad Performance of Quad P Power Supply ower Supply High performance with energy High performance with energy recovery recovery Total energy recovery rate of Total energy recovery rate of 68.5 68.5 (measured) (measured) No need for additional wall No need for additional wall power (only 39kW for all new power (only 39kW for all new magnets) magnets) High precision and high stability High precision and high stability by analog feedback with IGBT by analog feedback with IGBT Stability of 0.01 Stability of 0.01 Flexible synchronous controls Flexible synchronous controls with global event control system with global event control system Independent pulse Independent pulse- -by modulation at 50 Hz modulation at 50 Hz Drives a 1 mH coil Drives a 1 mH coil at 330 A, 340 V, 1.5 ms at 330 A, 340 V, 1.5 ms risetime risetime for 24 hours for 24 hours by- -pulse pulse Injector Linac Status K.Furukawa, B2GM, Feb.2018 10

11. Power Consumption Measurement Power Consumption Measurement Quad (50 Hz, 300 A) x 1 3000 2628.6 2500 Actual power consumption (measured) 2250 2000 Energy stored in coil inductance Power (W) 1500 Heat loss at Magnet Heat loss on cables 1000 827 Total Energy 500 302.6 76 0 Pjoule-mag Pjoule-cable PL . Ptotal Pmeasured Energy recovery ratio = 1 - Pmeasured/ Ptotal= 68.5 % Injector Linac Status K.Furukawa, B2GM, Feb.2018 11

12. Stability of Quad Power Supply Stability of Quad Power Supply 25 mA / div 0.014578 A / 165.946 A = 0.0107% / 24 hours (for PF_52_4 magnet) Injector Linac Status K.Furukawa, B2GM, Feb.2018 12

13. New Pulsed New Pulsed M Magnets enabled Simultaneous agnets enabled Simultaneous PF/PF /PF- -AR AR Injections And 2 Test Beam Accelerations Injections And 2 Test Beam Accelerations PF Injector Linac Status K.Furukawa, B2GM, Feb.2018 13

14. For Phase 3 For Phase 3 Pulsed bending magnet addition for Pulsed bending magnet addition for switching between RF electron gun / switching between RF electron gun / thermal electron gun thermal electron gun Pulsed corrector additions for offset Pulsed corrector additions for offset injection (orbit control) to enable lower injection (orbit control) to enable lower emittance emittance 40 magnet replacements if budget allows 40 magnet replacements if budget allows Injector Linac Status K.Furukawa, B2GM, Feb.2018 14

15. Planning Pulsed Planning Pulsed B Bend for Merger end for Merger L Line ine 24-degree Merger Bend x2 Thermionic Gun PF-AR LER (primary e for e+ PF HER Photo RF Gun Injector Linac Status K.Furukawa, B2GM, Feb.2018 15

16. DR LTR / RTL Waveguides DR LTR / RTL Waveguides Accelerating structures for energy / bunch compressors on DR LTR / RTL beam lines 45-m waveguides from linac gallery Fabrication errors of ~150 m were found (while schematics from KEK and from maker were correct) DR RTL Linac Injector Linac Status K.Furukawa, B2GM, Feb.2018 16

17. DR LTR / RTL DR LTR / RTL Waveguides Waveguides Components with Red circles had to be replaced Energy Compressor on LTR Energy Compressor on LTR Bunch Compressor on RTL Bunch Compressor on RTL Injector Linac Status K.Furukawa, B2GM, Feb.2018 17

18. Structure of Waveguide Flange Structure of Waveguide Flange Metal Seal (Vacuum) RF Contactor (Electric) Emphasized figures Correct Wrong only 150 m difference Injector Linac Status K.Furukawa, B2GM, Feb.2018 18

19. Fabrication Error and Recovery Fabrication Error and Recovery September 2017 September 2017 A large reflection was observed from the middle of A large reflection was observed from the middle of waveguides in the low waveguides in the low- -power test power test Fabrication errors in 58 waveguide flanges were identified Fabrication errors in 58 waveguide flanges were identified October 2017 October 2017 High power test was performed at a test stand High power test was performed at a test stand Discharge at the gap prevents the power only up to 10% Discharge at the gap prevents the power only up to 10% of the nominal power of the nominal power All 29 wrong waveguides were replaced; some were replaced with the ones with different length, others were newly fabricated Injector Linac Status K.Furukawa, B2GM, Feb.2018 19

20. Fabrication Recovery Fabrication Recovery Early October 2017 Early October 2017 Removal of all erroneous waveguides from the tunnel Removal of all erroneous waveguides from the tunnel Till November 2017 Till November 2017 Fabrication, preparation and test of replacement waveguides Fabrication, preparation and test of replacement waveguides Late November Late November early December 2017 early December 2017 Re Re- -installation in between linac operation installation in between linac operation December 17 and 24, 2017 December 17 and 24, 2017 High High- -power verification of whole system in between DR power verification of whole system in between DR construction construction January 2018 January 2018 Intermittent RF conditioning in between DR construction Intermittent RF conditioning in between DR construction Reached nominal power for Phase 2 and 3 operation Reached nominal power for Phase 2 and 3 operation Confirmed the designed energy compression of one third on LTR Confirmed the designed energy compression of one third on LTR Injector Linac Status K.Furukawa, B2GM, Feb.2018 20

21. LTR/ECS LTR/ECS RTL/BCS Waveguide Conditioning RTL/BCS Waveguide Conditioning Injector Linac Status K.Furukawa, B2GM, Feb.2018 21

22. Summary Summary New Pulsed Magnets New Pulsed Magnets Successful fabrication and installation of home Successful fabrication and installation of home- -grown low pulsed magnet system during 2017 summer shutdown pulsed magnet system during 2017 summer shutdown 1 1- -month test was performed as scheduled month test was performed as scheduled Experienced no large troubles so far and enabled stable Experienced no large troubles so far and enabled stable simultaneous accelerations with different energy beams simultaneous accelerations with different energy beams grown low- -cost cost Erroneous Waveguides Erroneous Waveguides Replacements of 29 waveguides were performed successfully even Replacements of 29 waveguides were performed successfully even during light source operation and SuperKEKB commissioning during light source operation and SuperKEKB commissioning /construction /construction Achieved the designed energy compression without any harmful Achieved the designed energy compression without any harmful impact against DR commissioning impact against DR commissioning Injector is ready for Phase Injector is ready for Phase- -2 commissioning 2 commissioning Injector Linac Status K.Furukawa, B2GM, Feb.2018 22

23. Thank you Thank you Injector Linac Status K.Furukawa, B2GM, Feb.2018 23