Virtual Accelerator for Beam Injection Efficiency
Construction budget constraints in Phase II commissioning require careful planning for Linac energy margins and backup preparations. With multiple linac sections and potential failure modes to consider, achieving low emittance beam injection is crucial for operational success.
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Injector Linac Energy Margin Injector Linac Energy Margin Answers to injector questions at Answers to injector questions at Moday Moday talk talk Kazuro Kazuro Furukawa Furukawa Injector Linac, KEK Injector Linac, KEK K.Furukawa, KEK, Feb.2017. Injector Linac Energy Margin 1
Linac Mission in FY2016-FY2017 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 more beam current New high New high- -current photo current photo- -cathode RF gun developments cathode RF gun developments 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 more beam current 1 The single injector would behave as multiple injectors to multiple storage rings by the concept of virtual accelerator K.Furukawa, KEK, Feb.2017. Injector Linac Energy Margin 2
In Phase II Commissioning Linac Energy Margin in Phase II Linac Energy Margin in Phase II Construction budget is so tight that no backups are prepared for many Construction budget is so tight that no backups are prepared for many components (common understanding) components (common understanding) As the acceleration units are indispensable, As the acceleration units are indispensable, for Y( backup/stand backup/stand- -by unit (~150 MeV) is prepared for each of three linac sections by unit (~150 MeV) is prepared for each of three linac sections Sections: J Sections: J- -Arc (1.5 GeV), SY2 Arc (1.5 GeV), SY2- -DR (1.1 GeV e DR (1.1 GeV e+ +), SY3 51 units for acceleration and 9 units for beam manipulation 51 units for acceleration and 9 units for beam manipulation However, However, Y( Y(6s) was out of consideration for Phase 6s) was out of consideration for Phase- -II II It may be possible to operate for It may be possible to operate for Y( Y(6s) without backups (J 6s) without backups (J- -Arc 1.7 GeV) Need to reach an understanding with PF / PF Need to reach an understanding with PF / PF- -AR for possible interference Before that, we surely have to establish low emittance beam injection Before that, we surely have to establish low emittance beam injection There are many failure modes of units, typical ones are; There are many failure modes of units, typical ones are; High power klystrons [a few times a year] High power klystrons [a few times a year] Two and a half days to replace a klystron Two and a half days to replace a klystron High power klystron pulse modulators [once or twice a year] High power klystron pulse modulators [once or twice a year] F From a shift to several days depending on the failures rom a shift to several days depending on the failures Fatal damage in accelerator structures [once in a few years] Fatal damage in accelerator structures [once in a few years] Several days to replace a structure Several days to replace a structure Frequency of the appearance has been increasing Frequency of the appearance has been increasing for Y(4s) 4s) in Phase in Phase- -II at II at least a single least a single Linac- -end (7 GeV e end (7 GeV e / 4 GeV e / 4 GeV e+ +) ) ), SY3- -Linac Arc 1.7 GeV) AR for possible interference Kamitani et al K.Furukawa, KEK, Feb.2017. Injector Linac Energy Margin 3
In Phase III Commissioning Linac Energy Margin in Phase III Linac Energy Margin in Phase III U Unit #13 will be added in Phase nit #13 will be added in Phase- -III (+150 MeV) S Securing well ecuring well- -performed accelerator structures in #44, the unit will be performed accelerator structures in #44, the unit will be converted to high converted to high- -gradient by adding another klystron (+70 MeV) gradient by adding another klystron (+70 MeV) On failures, the J On failures, the J- -Arc energy may be changed to help other Arc energy may be changed to help other sections depending sections depending on the failure on the failure mode If really relevant, DR energy may be changed to help e+ (?) If really relevant, DR energy may be changed to help e+ (?) In the long run, degraded accelerating structures should be In the long run, degraded accelerating structures should be refurbished refurbished III (+150 MeV) mode Kamitani et al SuperKEKB PF/AR Injector PF 2.5 GeV 0.2nC x 1 B A 1.1 GeV e+ damping ring New RF gun 5 nC Thermionic gun 10 nC J-arc 1.5 GeV Slow Positron LER 4.0 GeV 4nC x 2 Energy Compression Bunch Compression New Positron Capture Section Primary electron 2.9 GeV, 10nC x 2 Energy Compression Bunch Compression HER 7.0 GeV 5nC x 2 20 um 5 1 C 2 3 4 PF-AR 6.5 GeV 0.2nC x 1 K.Furukawa, KEK, Feb.2017. Injector Linac Energy Margin 4
Why Smaller Margin Why Smaller Margin while dropping Energy 8 while dropping Energy 8 GeV GeV 7 7 GeV GeV No backup/stand No backup/stand- -by before J Optimized for SuperKEKB ring injection reliability with larger beam Optimized for SuperKEKB ring injection reliability with larger beam currents and smaller emittance currents and smaller emittance by before J- -Arc in KEKB operation Arc in KEKB operation Kamitani et al A unit was removed to make a room for DR BT A unit was removed to make a room for DR BT Positron deceleration capturing Positron deceleration capturing Lower acceleration in large aperture structures in the positron Lower acceleration in large aperture structures in the positron capture section capture section An unit before J An unit before J- -Arc was converted into a stand Arc was converted into a stand- -by for availability C C- -band structures were converted into S band structures were converted into S- -band to help emittance preservation preservation Degraded accelerating structures after 35 years of operation Degraded accelerating structures after 35 years of operation Larger beam current with larger beam loading Larger beam current with larger beam loading by for availability band to help emittance K.Furukawa, KEK, Feb.2017. Injector Linac Energy Margin 5
One of Key Component: Photo Cathode RF Gun Development of Photo Development of Photo- -cathode RF Gun cathode RF Gun Succeeded in injection Succeeded in injection during SuperKEKB Phase 1 during SuperKEKB Phase 1 commissioning for 11 days Employs Employs Yb Yb- -doped doped- -fiber and Yb:YAG laser fiber and Yb:YAG laser, , Ir5Ce cathode Ir5Ce cathode, , quasi travelling wave quasi travelling wave side side- -coupled cavity coupled cavity Need stability improvements Need stability improvements Beam instrumentation Beam instrumentation improvement and improvement and comparison with comparison with simulation codes underway simulation codes underway Bunch width commissioning for 11 days Beam orbit measurement Secondary RF gun is being constructed Secondary RF gun is being constructed as a backup as a backup Incorporate suggestions by review committee Incorporate suggestions by review committee for availability for availability Thermionic gun Primary RF gun Quasi traveling wave side couple cavity New secondary RF gun Ir5Ce Cathode K.Furukawa, KEK, Feb.2017. Injector Linac Energy Margin 6
One of Key Component: Pulsed Magnets Development and installation of pulsed magnets Development and installation of pulsed magnets Pulsed magnet power supplies were postponed to 2017 because of resource availability Pulsed magnet power supplies were postponed to 2017 because of resource availability 30 quads, 36 steerings, 2 bends 30 quads, 36 steerings, 2 bends, 13 girders will be fabricated and installed in 2017 , 13 girders will be fabricated and installed in 2017 Quads with aggressive design at Quads with aggressive design at 1 mH, 330 A, 340 V, 1 ms 1 mH, 330 A, 340 V, 1 ms with energy recovery Essential for SuperKEKB low Essential for SuperKEKB low e emittance injection and simultaneous injections mittance injection and simultaneous injections 4+1 4+1 r ring injections with virtual accelerator concept ing injections with virtual accelerator concept Risks against schedule and possible backup operation procedure are investigated Risks against schedule and possible backup operation procedure are investigated with energy recovery up to 75% up to 75% Long term tests Long term tests at a stand Satisfies specifications Satisfies specifications Some more control capability Some more control capability Synchronous operation in Synchronous operation in 2017 2017 at a stand Beam test Beam test with two quads with two quads Successful Successful 25 Hz beam switches 25 Hz beam switches Basic features are completed Basic features are completed Event timing synchronization needed Event timing synchronization needed Girders are tested as well Girders are tested as well In In- -house house drawings drawings to save rsc. 0.1mm alignment 0.1mm alignment precision Ready for Phase Ready for Phase- -3 upgrade to save rsc. precision 3 upgrade K.Furukawa, KEK, Feb.2017. Injector Linac Energy Margin 7
Possible Rescheduling Possible Rescheduling Under limited resources rescheduling of fabrication, purchase, tests, installation, Under limited resources rescheduling of fabrication, purchase, tests, installation, commissioning is planned commissioning is planned Because of construction concentration in JFY2017, 5 Because of construction concentration in JFY2017, 5- -month shutdown of injector is planned injector is planned for KEKB it could allocate 9 for KEKB it could allocate 9- -month shutdown in 1997, synchronizing with light source month shutdown in 1997, synchronizing with light source upgrade upgrade month shutdown of K.Furukawa, KEK, Feb.2017. Injector Linac Energy Margin 8
