Simultaneous Top-Up Injection into
four Storage Rings at SuperKEKB
Masanori Satoh (KEK)on behalf of Injector Linac Group

Masanori Satoh (KEK)

IPAC’21, May 2021

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KEK e-/e+ Injector Linac History
1978-1981: Construction of injector linac for Photon Factory (PF)1982: Injector for PF (e-: 2.5 GeV)
1986-1994: Injector for PF, TRISTAN (e-: 2.5 GeV, e+: 2.5 GeV)
1987: PF-AR started
1993: Injector upgrade for KEKB project (e-: 2.5 GeV => 8 GeV, e+: 2.5 GeV => 3.5 GeV)
1998: KEKB commissioning started
2002: Two bunch injection to KEKB
2003 March: Achievement of 100,000 Hours of Operation
2004: Simultaneous top up project started
2005: PF new BT (decoupling from LER BT)
2009 Apr.: Simultaneous top up of 3 storage rings (KEKB HER/LER, PF)2010 June 30: KEKB end of operation
2012: PF-AR direct beam transport (new BT) design started (decoupling from HER BT)
2016: SuperKEKB Phase1 (HER 7 GeV e-, LER 4 GeV e+)
2017: PF-AR full energy (6.5 GeV) injection with new BT
2018: SuperKEKB Phase2
2019: SuperKEKB Phase32019 May: Simultaneous top up of 4 storage rings (SuperKEKB HER/LER, PF, PF-AR) WEPAB037
2020 May: Achievement of 200,000 Hours of Operation
Masanori Satoh (KEK)

IPAC’21, May 2021

WEPAB036

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Electron Accelerator Complex in KEK Tsukuba Campus:one injector, four storage rings (and e+ DR)
e+e-

HER : e7 GeV

Belle II
SuperKEKBLER : e+4 GeV

Circumference : 3 km
STF

PF-AR: 6.5 GeV

Injector LINAC(600 m)Each ring requires much different beam quality

Bunch charge: 0.1 nC – 4 nC (10 nC for e+ production)
Beam energy: 2.5 GeV – 7 GeV
Beam energy spread: 0.07% –Emittance: 15 – 150 mm·mrad (normalized)e+ Damping Ring
PF: 2.5 GeV

Injector Linac provides the beams to 4 (+1) different rings up to 50 Hz⚫ Photon Factory
Light Source⚫ PF-AR⚫ SuperKEKB High Energy Ring (HER)⚫ SuperKEKB Low Energy Ring (LER) + Damping Ring
Masanori Satoh (KEK)

IPAC’21, May 2021

Belle II experiment3

Injector Goal
• High quality beam for SuperKEKB (high bunch charge, low emittance, small energy spread)• Low emittance rf e- gun, DR ring for e+, good alignment, etc.
• Simultaneous top-up for 4 rings (short beam life time of SuperKEKB MR ～ 6 min.)• Event based timing system, pulsed magnet, fast rf phase/timing, fast monitors (up to 50 Hz)
PF/PF-AR

KEKB injection(archived)

SuperKEKB injection(final)injection
LER

HER

LER (w/ DR)

HERBunch charge(nC)

0.1 - 0.31142(achieved)42(achieved)

Normalized
emittance(H/V) (mm)

150

1400

310

100/15

40/20

Energy spread
(%)

n.d.

0.15

0.05

0.16

0.07

Beam energy(GeV)

2.5/6.5 or 5

3.5

84

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Masanori Satoh (KEK)

IPAC’21, May 20214Injector Linac Operation Outline
60 klystron units
240 accelerating structures (S-band 2-m-long)
Bunch charge (nC) in the current nominal operation

8 Sectors (A-C,1-5)
Energy Knob

1.1 GeV e+
Damping Ring

Thermionic gun

HER

2LER

2PhotocathodeRF gunJ-ARC
1.5 GeVB

A

10 e- for e+ production
PF/PF-AR

BCS
ECS

C

123e+
e+ capture section
target450.1 - 0.3PF

ECS

PF-AR

LER

chicaneEnergy KnobHER
HER 7GeV
PF-AR 6.5 or 5 GeV

Acceleration
4.2 GeVee+ target

LER 4 GeV e+Stand-byDeceleration

1.1 GeVe+PF 2.5 GeVAcceleration

1.5 GeVC12345beam line after the J-ARC.
Masanori Satoh (KEK) Beam energy for each beam mode along
IPAC’21, theMay 2021

5Event Based Timing System
EVG clockCentral timing station

Main Rings

EVG#1

EVG EVR

Damping Ring

Event signal (optical fiber)
PFAR

EVR

PF

PFAR
PF

EVG#2 EVG#3
EVR
EVR

EVR

EVR

e− GunJ-ARC

EVR

e– BT (PF: 2.5 GeV, 0.1nC)

EVR
EVR

Masanori Satoh (KEK) EVRs

Micro-Research Finland Oy: event generator (EVG),event receiver (EVR)• Based on VME system (VxWorks6.8 (RTOS),MVME6100 (CPU))• PXIe EVR for pulsed magnet control• EVG x 3, EVR x 28 (VME), x17 (PXIe)• Low level rf phase, pulsed magnet, etc arecontrolled by using the EventCode distributed from
EVG. (each EventCode is tagged to each ring
injection beam.)

EVR
EVR

EVR

EVR

EVR

EVR

e+Target
EVR

EVR

e– BT (PF-AR: 6.5 GeV, 0.1 nC)
e+ BT (SuperKEKB: 4 GeV, 1-4 nC)
e– BT (SuperKEKB: 7 GeV, 1-4 nC)

EVR

May 2021
EVR IPAC’21,
EVR

6Beam Injection Pattern Generation• Beam repetition rate is determined by demand from each ring.
• Priority can be defined.

Beam repetition rate management foreach beam injection mode.
Masanori Satoh (KEK)

IPAC’21, May 2021

Beam mode
KBE: SuperKEKB e- (HER)
KBP: SuperKEKB e+ (LER)
QFE: PF
ARE: PF-AR

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Pulse to pulse beam switching:rf e- gun/thermionic e- gun
In injector section

Thermionic DC e- gun (GU_AT)
w/ 2 subharmonic bunchers (114 MHz, 571 MHz)and 2 bunchers.

・e+ production e-: 10 nC (for LER injection)・e- study/HER injection: 1 nC
・PF injection: 0.1 - 0.3 nC
・PF-AR injection: 0.1 - 0.3 nC

RF e- gun
（GR_A1 for HER injection）

Pulsed bend

IPAC’21, May 2021

RF e- gun

Low emittance photocathode rf e- gun

Ir7Ce2 cathodeLaser system• Photocathode: Ir7Ce2• Cavity: QTWSC (Quasi Travelling Wave Side Coupler)– Strong focusing electric fieldshort drift space
Secondary RF gun
for test and backup

M. Yoshida et al.

IPAC’21, May 2021

emittancee(2 nC)～20 mm (BT)•Hybrid laser system for rf e- gunYb doped fiber and Nd:YAG DPSS module Amplifier

nx,nxyGoal: enx,nxy (4 nC)～40/20 (H/V) mｍ)••••

1st laser
2nd laser

Output Power in 1st line:ω (1064 nm): 32 mJ
2ω ( 532 nm): 11 mJ
4ω ( 266 nm): 1.2 mJ

DOE (diffractive optical element) in 1st laser line:
Laser beam homogenizer for low emittancebeam w/ high intensity bunch charge.

world first DOE application in UV laser

R. Zhan et al.

Optics layout 10in the tunnel
IPAC’21, May 2021

Positron source setup at Sector1Positron target and capture section

DC solenoid
Large aperture S-band acc. Structures (x10)

W target + flux concentrator (FC)IPAC’21, May 2021

Y. Enomoto et al.

11Positron Capture Section: Flux concentrator, bridge coil, solenoid
Large Aperture S-band acc. structure (LAS)
Bridge Coil (BC)Solenoid

Tungsten target

3.5 GeV e- beam

Flux Concentrator (FC)Cu-alloy (NC50: Cu-Si-Ni)
Poster presentation:[WEPAB144]
IFC= 12 kA
Masanori Satoh (KEK)

IPAC’21, May 2021

Y. Enomoto et al.

12emittancee(2.3 nC)～99.7/3.2 mm (BT)nx,nxyPositron yield• 5 nC at BPM<SP_16_5> (1st BPM after e+ target)• ～ 3 nC LTR (Linac To damping Ring) and downstream• For obtaining 4 nC at BT:

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Goal: enx,nxy (4 nC)～100/15 (H/V) mｍ)• Some more steering/Q magnets will be installed after target in 2021 (this summer).
• Increase gradient: 7.3 MV/m to 14.0 MV/m (design) for two structures (AC_15_1[2]situated at downstream e+ target)• Increase FC field and DC solenoid field. (power supply should be improved)

Design value (0.58)
Present

Y. Enomoto et al.

IPAC’21, May 2021

Pulsed magnet system• Pulsed quad (x 32) (w/ ceramic duct), steering (x 65) and bend (x 2) are used (mainly in sector 3 to sector 5)
since 2017
• PXIe based control system (Windows, LabVIEW, EPICS, MRF event receiver) (x 16) have worked fine.
• Power supply stability: 0.01% (24 hours)  requirement : 0.1%
• Stored energy in an inductance of the magnet are recovered to capacitors.
• Total energy recovery efficiency 68.5％ (measured).

Y. EnomotoPhoto of a prototype pulsed Q driver
designed by T. Natsui

Current statistics in 24 hours

Masanori Satoh (KEK)

Movable girder for pulsed magnet(remote controllable, 10 mm step)

IPAC’21, May 2021

Photo of control unit and power supply14

All magnets in Sector3-5 were replaced by pulsed one in 2017

Old DC magnets
Q triplet

We renewed power supply, cooling water,cabling, support, control system, software, etc
in 99 working days.

Masanori Satoh (KEK)

IPAC’21, May 2021

New pulsed magnets
QF
Horizontal steering
Vertical steering
QD15Beam orbit snapshot during simultaneous top up injection
LER

HER
Hor.
orbit
Ver.
orbit
Bunchcharge
rf gunThermionic gun and damping ring
PF-ARPF

Thermionic gun
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Thermionic gun
IPAC’21, May 2021

Stored current stability during simultaneous top up injection

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6.25 Hz6.25 Hz4.16 Hz4.16 Hz

IPAC’21, May 2021

Long way to simultaneous top-up injection into 4 rings (1)New PF-BT
in 2005

May.2000

Apr.2003, Dual Bunch injection

Feb.2005, Continuous Injections

However, still PF, PF-AR
injection 2-3 times daily

red: beam current (e-, e+)purple: vacuum (e-, e+)yellow: luminosity
green: integrated luminosity

2004: Simultaneous top up injection project started
2005: New PF BT (decoupling from LER BT)
2017: New PF-AR BT (decoupling from HER BT)
IPAC’21, May 2021

PF

Long way to simultaneous top-up injection into 4 rings (2)New PF-AR BTin 2017
PF

2009, simultaneous top-up
for 3 rings (KEKB HER/LER, PF)

2019, simultaneous top-up
for 4IPAC’21,rings! (SuperKEKB HER/LER, PF, PF-AR)
May 2021

Summary
Simultaneous top up injection operation of 4 storage rings (SuperKEKB HER/LER, PF,PF-AR) has successfully established.

• Pulse to pulse beam control based on the event based timing system, low level rfphase control, pulsed magnet (Quad, Steering, Bend)• 50 Hz monitoring (BPM, rf, pulsed magnet PS, FC) and analysis tools• Many People’s Continuous Contributions and Efforts over 15 years
Future improvements:• Improvement of reproducibility beam quality (emittance, energy spread)• Achievement of the final parameter required for SuperKEKB (high bunch charge,low emittance)• Deteriorated subsystem will be replaced (damaged acc. Structures, old magnet
power supply and controller, and so on)
Masanori Satoh (KEK)

IPAC’21, May 2021

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Thank you for your attention!

Masanori Satoh (KEK)

IPAC’21, May 2021

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