SuperKEKB Electron Positron Injector LINAC Upgrade
towards Higher Charge and Lower EmittanceK. Furukawa, H. Ego, Y. Enomoto, N. Iida, T. Kamitani, M. Kawamura, S. Matsumoto, T. Matsumoto, T. Miura,
M. Satoh, A. Shirakawa, T. Suwada, M. Yoshida,High Energy Accelerator Research Organization (KEK), SOKENDAI, Tsukuba, Ibaraki, 305-0801, JapanKEK electron positron injector linac has established simultaneous top-up
injections in 2019 for 5 rings of SuperKEKB DR, LER, HER, PF ring and PF-AR
as a base of the both elementary particle physics and photon science
experiments even under a quite short beam lifetime. It improved the injection
stabilities while the SuperKEKB broke the world record of the collision
luminosity of the previous project KEKB. As the collision performance improves,

the beam-beam effect makes the dynamic aperture shrink, and the beam
lifetime reduces further. Thus, it became inevitable for the injector to beupgraded in order to resolve the contradictory improvements of higher charge
and lower emittance of injection beams regarding beam wakefield till 2025.
The upgrade plan is described including pulsed magnets, an energy
compression system, accelerating structures, girders, and positron generator.

KEK e– / e+ injector LINAC is being upgraded further in seven categories
for higher beam charge and lower beam emittance in order to achieve the final goal of SuperKEKB
Present Injector LINAC

BAPF
2.5 GeV
0.2nC x 1

1.1 GeV
e+ damping ring

New RF gun 5 nC
Thermionic gun 10 nC

J-arc
Slow Positron
1.5 GeV
EnergyBunchPrimary electron
New PositronCompression Compression
Capture Section
2.9 GeV, 10nC x 2
Bunch
Compression

1C2LER
Energy4.0 GeVCompression 4nC x 2345PF-AR
6.5 GeV
0.2nC x 1

Seven Upgrade Categories

Pulsed magnets/kickers

RF gunPositron capture section

Transverse and Longitudinal Emittance Mitigation

High precision movers

Accelerating structure

PCB capacitor renewal

New energy compressor

Required Beam Performance◆ As the beam orbit deviation by 0.1mm maycause wakefield effect in the structures, pulsed
magnets and movable girders are prepared.

by pulsed magnets/kickers

HER
7.0 GeV
4nC x 220 um

Stage

KEKB (final)

Phase-I (achieved)

Phase-III (interim)

Phase-III (final)

Beame+e–e+e–e+e–e+e–e+e–

EnergyStoredcurrent
Life time(min.)

3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

1.6 A

1.1 A

1.0 A

1.0 A

––

1.8 A

1.3 A

3.6 A

2.6 A

150

200

100

100––––

66

primary e- 10

Bunch charge
(nC)
Norm.
Emittance

primary e- 8→11→ 0.4

1400

310

1000

primary e- 10

10.5

1200/40130(gbe) (mrad)

Seasonal alignment deviation.

Phase-II (achieved)

224150/30

100/40100/1540/20(Hor./Ver.)(Hor./Ver.)(Hor./Ver.)(Hor./Ver.)→4150(Hor./Ver.)

Energyspread

0.13%

0.13%

0.50%

0.50%

0.16%

0.10%

0.16%

0.10%

0.16%

0.07%

Bunch / Pulse

2222222222

Repetition
rate

50 Hz

25 Hz

25 Hz

Simultaneous
top-upinjection(PPM)

3 rings(LER, HER, PF)

No top-up

Partially

50 Hz

50 Hz

4+1 rings (LER, HER, DR, 4+1 rings (LER, HER, DR,PF, PF-AR)
PF, PF-AR)

by movable girders

Klystron
40 MW 4 usAged Device Renewals

Girders for magnets andstructures up to 1000 kg canbe moved by a micron.

SLED
140 MW 0.5 us

230 S-band structures (many 40-year old)
19 have discharge issues
6 had cooling water leakages

Possible beam shape distortion

by energy compression system

160 MV (21 MV/m)
in four 2-m structures
Damping
Ring

Low emittance
RF-gune–Injector Linac

ECS Chicane

e+700 mHigh efficiency
e+ generator

2x beamcurrent

PF
2.5 GeV

e–e+ BTPF-AR
6.5 GeVe – BTECS Accelerating Structure
26m

E100

Beam from Injector and Storage Current
SuperKEKB:
7 GeV e2000 mA
4 GeV e+2800 mAPF:
2.5 GeV e450 mA
PF-AR:
6.5 GeV e60 mA010
H200000 E1E00
200 010000HHE
10000

Existent energy compression (ECS) for e+

10E
00 10H00 E

ECS designed for e–

10 nC
primary e-

Ir-Ce alloy cathodeLasershaping
by DOE

Belle II
30x
Luminosity

Electron/positron machine complex at KEK
bridge coils

targetbeamhole

RF cavity

LER
4 GeV

000 E

solenoid
LAS Accel.
structure

Targetdiameter
4.0 mmrear view

Targetoffsete+

3.5 mm

4 nC injection e-Flux
Concentratorpulsed quad

700 Capacitors in power modulators with low-level PCB(30-40-year old) have to be replaced for legal compliance

3 km

H

DC quad spoiler

pulsed corr.

SuperKEKB

10E00
1Electron and positron source improvements
top view

HER
7 GeV

Holediameter
2.0 mm

2.0 mmFC offset

7.0 mm
FC aperture

Summary◆ KEK injector LINAC will be upgraded progressively in order to support a higher

collision rate in SuperKEKB collider rings.
◆ The upgrade is designed in seven categories for transverse and longitudinalemittance optimization, electron and positron source enhancement, and aged
device renewals.