Rejuvenation of 7-GeV SuperKEKB Injector Linac
Y. Enomoto, K. Furukawa, M. Akemoto, D. Arakawa, Y. Arakida, H. Ego, A. Enomoto, T. Higo, H. Honma, N. Iida, M. Ikeda,H. Kaji, K. Kakihara, T. Kamitani, H. Katagiri, M. Kawamura, M. Kurashina, S. Matsumoto, T. Matsumoto, H. Matsushita,S. Michizono, K. Mikawa, T. Miura, F. Miyahara, H. Nakajima, K. Nakao, T. Natsui, M. Nishida, Y. Ogawa, Y. Ohnishi,
S. Ohsawa, F. Qiu, I. Satake, M. Satoh, Y. Seimiya, A. Shirakawa, H. Sugimura, T. Suwada, T. Takenaka, M. Tanaka,
N. Toge, Y. Yano, K. Yokoyama, M. Yoshida, R. Zhang, X. Zhou
High Energy Accelerator Research Organization (KEK), SOKENDAI, Tsukuba, Ibaraki, 305-0801, Japan
KEK injector linac has delivered electrons and positrons for particle
physics and photon science experiments for more than 30 years. It is being
upgraded for the SuperKEKB project, which aims at a 40-fold increase inluminosity over the previous project KEKB, in order to increase ourunderstanding of flavor physics beyond the standard model of elementary
particle physics.
SuperKEKB energy-asymmetric electron and positron
collider with its extremely high luminosity requires a high current, lowemittance and low energy spread injection beam from the injector. The

electron beams will be generated by a new type of RF gun, that provides amuch higher beam current to correspond to a large stored beam current anda short lifetime in the ring. The positron source is another major challengethat enhances the positron bunch intensity from 1 to 4 nC by increasing thepositron capture efficiency, and the positron beam emittance is reduced from2000 µm to 10 µm in the vertical plane by introducing a damping ring,followed by the bunch compressor and energy compressor. The summary of
the rejuvenation is reported.

e– / e+ Injector rejuvenation with high-intensity and low-emittance beams
towards 40-times higher luminosity, operating for Phase-II commissioning
SuperKEKB Electron/Positron Complex
Damping
Ring

Low emittance
RF-gune–Injector Linac

2x beamcurrent

PF
2.5 GeV

RF-Gun e- beamcommissioning
at A,B-sector

e+ commiss.
at 1,2 sector (FC, DCS, Qe- 50%)e- commiss.
at 1,2,3,4,5 sector

e- commiss.
at A,B,R,C,1

Phase1: high emittance beam for vacuum scrub
Phase2,3: low emittance beam for collision

Time →Location↓e+600 m

High efficiency
e+ generator

Balanced Schedule for Improvements / Stability
Typical Accelerator Units

e–BeamLicensesin steps

e+ BT

PF-AR
6.5 GeVe – BT

Beam from Injector and Storage Current
SuperKEKB:
7 GeV e2600 mA
4 GeV e+3600 mA
PF:
2.5 GeV e450 mA
PF-AR:
6.5 GeV e60 mA

HER
7 GeV

1 nC
Phase13 km

Pulse-to-pulse modulation operation

4+1 Ring
Injections

1 - 2 nC
Phase2

2 - 4 nC
Phase3

Belle II
Without Top-up

40xLuminosity

Positron generator and its shield

Direct PF-AR BT
damped e+ commiss. Improved
at 1→5 Qe+ = 1~4nC RF gun
e- commiss.
at A→5 Qe- = 1~4nC

non damped e+ commiss.
at 1,2, 3,4,5 sectors
e- commiss. at A→5 sectors: Electron: Positron: Low current electron

Injector Linac

SuperKEKB particle physics

Low
Emittance
Injections

DRCommiss.

SuperKEKBLER
4 GeV

Low
Emittance
Beams

PF / PF-AR photon science◆ Long-term and fixed users◆ Short-term in many groups◆ Performance intensive◆ Stability intensive(Integrated performance)(Hates failures)◆ Minimum preventive maintenance◆ Deliberate scheduled maintenance◆ Invests on improvements◆ Invests on maintenance◆ May share common goal with users◆ Distance from users◆ Everyday is new◆ Fixed procedures

On-the-job training for operators

Difficult to train operators

High-current Low-emittance RF Gun

Rejuvenated Injector Linac

High-performance Pulsed Magnets

Thermionic gun
Primary RF gun

IrCe cathodeQTWSC cavity

QTWSC cavity
Secondary RF gun

Synchronized Global Controls
Event-basedControl System

Newly developed 64 pulsed magnets

SummaryEvery
20 msHigh-current Positron Generator

F.B
e− GunARCe– (2.5GeV, 0.2nC)

e− GunBridge Coils

Damping ring

SuperKEKB-LER Injection

F.B

e– (3.5GeV, 10nC)

F.B

e+ Targete+ (4GeV, 4nC)

since 2010, and is close to its

Pulsed positron generator

F.B
ARC

◆Injector linac has been rejuvenatedF.B

PF Injection

10 nC
Primary e-Solenoid

DCFocusing
Magnets Spoiler

LAS Accel.
Structure

Targete+e− Gun
ARCSuperKEKB-HER Injection

F.B

e– (7GeV, 5nC)
e− GunARC

PF-AR Injection

beamholeF.B

F.B
e– (6.5GeV, 0.2nC)

Virtual accelerators for simultaneous top-up injections
Each VA with associated beam feedback loops

PulsedCorrector
Magnets

4 nC Injection e-electrons and positrons in SuperKEKB
phase 1 & 2 commissioning.
◆It maintained light source injections

Flux
Concentrator

PulsedFocusing
Magnetscompletion.
◆It successfully injected required

during rejuvenation.
◆It is expected to improve for Phase 3
Side viewcommissioning.