Injector Linac Energy Margin
Answers to injector questions at Moday talkKazuro Furukawa
Injector Linac, KEKInjector Linac Energy Margin

K.Furukawa, KEK, Feb.2017.

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Linac Mission in FY2016-FY2017

Mission of Electron/positron Injector in SuperKEKB
v For 40-times higher luminosity in SuperKEKB collider
v Low emittance & low energy spread injection beam with 4-5 times more beam current³ New high-current photo-cathode RF gun developments³ New positron capture section³ Damping ring construction³ Optimized beam optics and correction³ Precise beam orbit control with long-baseline alignment³ Simultaneous top-up injection to DR/HER/LER/PF/PFARv Balanced injection for the both photon science andelementary particle physics experiments

1The single injector would behave as
multiple injectors to multiple storagerings by the concept of virtualaccelerator
Injector Linac Energy Margin

K.Furukawa, KEK, Feb.2017.

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In Phase II Commissioning

Linac Energy Margin in Phase II
u Construction budget is so tight that no backups are prepared for many
components (common understanding)u As the acceleration units are indispensable, for Y(4s) in Phase-II at least a single
backup/stand-by unit (~150 MeV) is prepared for each of three linac sections
v Sections: J-Arc (1.5 GeV), SY2-DR (1.1 GeV e+), SY3-Linac-end (7 GeV e– / 4 GeV e+)v 51 units for acceleration and 9 units for beam manipulationu However, Y(6s) was out of consideration for Phase-IIv It may be possible to operate for Y(6s) without backups (J-Arc 1.7 GeV)v Need to reach an understanding with PF / PF-AR for possible interferencev Before that, we surely have to establish low emittance beam injection

u There are many failure modes of units, typical ones are;v High power klystrons [a few times a year]³ Two and a half days to replace a klystronv High power klystron pulse modulators [once or twice a year]³ From a shift to several days depending on the failures

v Fatal damage in accelerator structures [once in a few years]³ Several days to replace a structurew Frequency of the appearance has been increasing
Injector Linac Energy Margin

Kamitani et alK.Furukawa, KEK, Feb.2017.

3In Phase III Commissioning

Linac Energy Margin in Phase IIIu Unit #13 will be added in Phase-III (+150 MeV)v Securing well-performed accelerator structures in #44, the unit will be
converted to high-gradient by adding another klystron (+70 MeV)

u On failures, the J-Arc energy may be changed to help othersections depending on the failure modev If really relevant, DR energy may be changed to help e+ (?)

u In the long run, degraded accelerating structures should be
refurbished
Kamitani et al
SuperKEKB PF/AR Injector
BAJ-arc
Slow Positron
1.5 GeV
Primary electron
2.9 GeV, 10nC x 2BunchCompression

CInjector Linac Energy Margin

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New RF gun 5 nC
Thermionic gun 10 nC

1.1 GeV
e+ damping ringLEREnergyBunch
New PositronCompression Compression
Capture Section

23PF
2.5 GeV
0.2nC x 1

Energy4.0 GeV
Compression 4nC x 2

45PF-AR
6.5 GeV
0.2nC x 1

HER
7.0 GeV
5nC x 220 um

K.Furukawa, KEK, Feb.2017.

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Why Smaller Margin
while dropping Energy 8 GeV à 7 GeV
u No backup/stand-by before J-Arc in KEKB operationu Optimized for SuperKEKB ring injection reliability with larger beamcurrents and smaller emittance
Kamitani et alu A unit was removed to make a room for DR BT
u Positron deceleration capturing
u Lower acceleration in large aperture structures in the positron
capture sectionu An unit before J-Arc was converted into a stand-by for availability
u C-band structures were converted into S-band to help emittancepreservationu Degraded accelerating structures after 35 years of operationu Larger beam current with larger beam loading
Injector Linac Energy Margin

K.Furukawa, KEK, Feb.2017.

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One of Key Component: Photo Cathode RF Gun

Development of Photo-cathode RF Gun
u Succeeded in injection during SuperKEKB Phase 1 commissioning for 11 daysu Employs Yb-doped-fiber and Yb:YAG laser,
Ir5Ce cathode, quasi travelling wave
side-coupled cavity
u Need stability improvements
u Beam instrumentation
improvement andcomparison withsimulation codes underway
Beam orbit measurement
Bunch widthu Secondary RF gun is being constructed
as a backup
u Incorporate suggestions by review committee
for availability

Thermionic gun
Primary RF gun

Quasi traveling wave
side couple cavity

New secondary RF gun
Ir5CeCathodeInjector Linac Energy Margin

K.Furukawa, KEK, Feb.2017.

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One of Key Component: Pulsed Magnets

Development and installation of pulsed magnets
v Pulsed magnet power supplies were postponed to 2017 because of resource availability
v 30 quads, 36 steerings, 2 bends, 13 girders will be fabricated and installed in 2017v Quads with aggressive design at 1 mH, 330 A, 340 V, 1 ms with energy recovery up to 75%
v Essential for SuperKEKB low emittance injection and simultaneous injections
v 4+1 ring injections with virtual accelerator concept
v Risks against schedule and possible backup operation procedure are investigated³ Long term tests at a stand³ Satisfies specifications³ Some more control capability³ Synchronous operation in 2017
Injector Linac Energy Margin³ Beam test with two quads³ Girders are tested as well
³ Successful 25 Hz beam switches³ In-house drawings to save rsc.
³ Basic features are completed³ 0.1mm alignment precision³ Event timing synchronization needed ³ Ready for Phase-3 upgrade
K.Furukawa, KEK, Feb.2017.

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Possible Reschedulingu Under limited resources rescheduling of fabrication, purchase, tests, installation,commissioning is plannedu Because of construction concentration in JFY2017, 5-month shutdown ofinjector is plannedv for KEKB it could allocate 9-month shutdown in 1997, synchronizing with light sourceupgrade   
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Injector Linac Energy Margin)$1'*-$%.-1203%2*.- ,.-2)1,*-K.Furukawa, KEK, Feb.2017.

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