KEKB Injection Developments(as a base of SuperKEKB)
Kazuro Furukawa
for Injector Linac, KEK<kazuro.furukawa@kek.jp>

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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KEKB Injector overview
Dual bunches in a pulse
Continuous injection
Simultaneous top-up injection
Upgrade towards SuperKEKB

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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KEKB Configuration ( – 2010)
uElectron Positron Accelerator Complex at KEK
BelleKEKBHER
8 GeV/cPF-AR
6.5 GeV/ce- BT

Linac delivered:for PF: 2.5 GeV e–for PF-AR: 3 GeV e–
for KEKB: 8 GeV e–
3.5 GeV e+e+, e- Linace+ BTLER
3.5 GeV/c
PF
Shared single injector between 4 storage rings
Shared beam transport line between HER & PF-ARInjector Linac Experience at KEKB

2.5 GeV/c

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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KEKB DesignuMaximum reuse of TRISTAN inheritanceuHowever, still many improvements applied, ex.
vMany bunch collisions with dual ring collider³Energy asymmetry for the boost of center of mass of Bs

vFull energy injection³Energy upgrade with SLED RF pulse compressor
w from 2.5 GeV (400 m) → 8 GeV (600 m)

vInjection aperture of 30 ps³Slight RF frequency modification to have an integer relation
w Linac 2856 MHz
w Ring (508.5 MHz →) 508.9 MHz: 10.386 MHz x 275: 10.386 MHz x 49

vAnd so on
Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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PEP-II/SLAC and KEKBuWe exchanged ideas between PEP-II and KEKB
vViewed each other from control rooms³Friendly competition
Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Performance improvements at KEKB
uCompetition with SLAC PEP-IIvOne of worries was the injector capability
vInjection beam quality
vBeam stability
vBeam current, especially positron
vInjection time to fill the both storage rings
vAnd, integrated luminosity

uMany improvements required, however
vTwo serious damages in accelerator structure in 2001
³after the performance was pushed too hard
³We found our way with optimized performance
Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Operational Optimizations
uFor example, run-length optimization

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Energy Stabilization Loops
u BPMs - Energy knob
v Energy knob without
energy spreadv Simple
P.I.
Loop

6 feedback loops along the linac depending on the modes

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Feedback loop monitor
u Robust operation isessential
v Remote monitoring insummary panelv Several conditions,limits in loop variables
v Beam-mode
dependent operationv Status and variable
logging, and theirviewers

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

9Operation statistics and improvements
Injector operation hours and failure rates

8,000

Operation hours (hour)
Failure rate (%)

Hours

7,000

Beam loss rate (%)

876,000

65,00054,00043,00032,00021,000100Rates (%)

uStatistics

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017

Fiscal year

u Failure: device failures that prevent optimum performanceu Beam loss: time when beam injection was really impossible
Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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KEKB Injector overview
Dual bunches in a pulse
Continuous injection
Simultaneous top-up injection
Upgrade towards SuperKEKB

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Two bunches in a pulsevAs the stored beam current in MR increases, much
more injection beam current was required
vEspecially for the positron injection rateuTwo bunches in a pulse acceleration in orderto to double the positron beam current planned
vMinimum bunch separation of 96 ns (10.386 MHz)vParallel dual grid pulsers for a single cathodevBeam instrumentation with 96 ns separationvTiming manipulation and bucket selection
vEnergy equalization

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Energy Equalization
uBeam loading compensation
vFor bunch separation of 96 ns³Or we sometimes utilize
energy difference
in order to equalize
the beam orbits

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Dual-bunch Energy Equalization, and Feedback
u Energy equalization is important for stable operation
Measurement at bunching section
after energy equalization
with RF pulse timing

Stabilization at bending section
with SLED timing

First Bunch

SLEDSecond Bunch

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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KEKB Injector overview
Dual bunches in a pulse
Continuous injection
Simultaneous top-up injection
Upgrade towards SuperKEKB

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Continuous Injection
vDetector data acquisition stopped during the injection
and the detector high voltage (HV) preparationvEspecially for the positron injection rateuContinuous Injection with detector HV applied
was another major step forward
vFor higher integrated luminosity
vby detector improvements, esp. CDC, TOF, DAQ
vwith certain benefit from collision with crossing angle³without bending magnet at IP, for lower backgroundvThen, approximately 26% gain achieved

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Continuous injectionua
2004, after continuous injection was applied
Data acquisition continued during injection(8-hour history of beam current, luminosity, etc.)

2003, before continuous injection was applied
Data acquisition stopped during injection(8-hour history of beam current, luminosity, etc.)

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Beam mode switching improvements
uContinuous injection was applied in 2004
Beam mode switching
80000
70000
60000

Count

50000
40000
30000
20000
10000
0
1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Year

uSwitched 360 times / day in 2008
uSimultaneous top-up injection was applied in 2009
Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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KEKB Injector overview
Dual bunches in a pulse
Continuous injection
Simultaneous top-up injection
Upgrade towards SuperKEKB

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Simultaneous Top-up InjectionsvEven faster beam mode switches

uPulse-to-pulse modulation (PPM) at 50 Hz³PPM was applied at PS/CERN (1977?) at 1.2 s

v~150 parameters were switched every 20 ms for 3beams

uMany Hardware improvements as well ascontrolsvPF top-up injection for higher quality experiments
vSensitive luminosity tuning with Crab cavities³Many more parameters in SuperKEKB for 4 beams
Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Dual-layer Controls

Fast Global Synchronous ControlsuEvent-based controls (MRF)
u114.24MHz event rate, 50Hz fiducials
uTiming precision < 10ps

Dual layer control concept
Dual Layer Controls

Event Generator

CentralOPI

EPICS
Channel Access

IOCIOCIOC

IOC

EVG

EVR

EVR

EVR

MRF
Event Link

SH_A1
KL_B5/B6

SB_B

Injection

SB_Ae­ Gun
ARC

e– BT (PF: 2.5GeV, 0.1nC)

Cont-ABC
KL_51/52
SB_C

SB_1

SB_2

SB_3

SB_4

SB_5

e+ BT (KEKB: 3.5GeV, 2nC)

e+ Target
Cont-1

Cont-2

Cont-3Cont-4Cont-5Event Receivers
Injector Linac Experience at KEKB

e– BT (KEKB: 8GeV, 2nC,PFAR: 3.0GeV, 0.1nC)

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Dual-layer Controls

One Machine, Multiple Virtual Accelerators (VAs)u Control/Monitor are carried dependent on a VA
v Mostly independent between VAs

u Independent parameter set for each VA, one of the VAs is controlled at atime
v VAs for Injections (HER (e-), LER (e+), PF, PF-AR) and Linac-only in SuperKEKB projecte− Gune– BT (PF: 2.5GeV, 0.1nC)

PF Injection

ARC

e+ Target

Event-based
Control Systeme− GunARC

KEKB-LER Injection

Primary e– (4GeV, 10nC)

e+ BT (KEKB: 3.5GeV, 0.6nC)

e+ Targete− GunARC

KEKB-HER Injection
e+ Targete– BT (KEKB: 8GeV, 1.2nC)

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Dual-layer Controls

Multiple Closed Loop Controls Overlappedu Closed loops were installed on each VA independently

e− Gune– BT (PF: 2.5GeV, 0.1nC)

PF Injection

ARCe+ Target
e− GunEvent-based
Control System

ARC

KEKB-LER Injection

Primary e– (4GeV, 10nC)

e+ BT (KEKB: 3.5GeV, 0.6nC)

e+ Targete− GunARC

KEKB-HER Injection
e+ Targete– BT (KEKB: 8GeV, 1.2nC)

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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KEKB Operation Improvement (base of SuperKEKB)
red: beam current (e-, e+)purple: vacuum (e-, e+)yellow: luminosity
green: integrated luminosity

Belle/KEK

May.2000
Apr.2003
Dual Bunch e+Feb.2005
ContinuousInjections
Dec.2008
Crab Cavities andSimultaneous Injection
Injector Linac Experience at KEKB

Keeps world
luminosity record
K.Furukawa, KEK, eeFACT2018, Sep.2018.

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KEKB Injector overview
Dual bunches in a pulse
Continuous injection
Simultaneous top-up injection
Upgrade towards SuperKEKB

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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SuperKEKB at 2002
uSome consideration on upgrade forSuperKEKB was presented already in 2002
uMuch different from present form, but thisshows a project needs a long lead timevLater,vEnergy exchange
was rejected
vNano-beam scheme
was employed

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Injector Linac Mission

Mission of Electron/positron Injector in SuperKEKB
v For 40-times higher luminosity in SuperKEKB collider
v Low emittance & low energy spread injection beams with 4 times higher beam current³ New high-current photo-cathode RF gun³ New positron capture section³ Positron damping ring injection/extraction³ 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
Low emittance
RF-gunDampingRinge–Injector Linace+600 m

High efficiency
e+ generator

2x beamcurrent

PF
2.5 GeVe–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

SuperKEKB
3 km

LER
4 GeV

Belle II
40xLuminosity

Injector Linac Experience at KEKB

The single injector would behave as
multiple injectors to multiple storagerings by the concept of virtual
accelerator
K.Furukawa, KEK, eeFACT2018, Sep.2018.

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SuperKEKB Schedule
SuperKEKB/Belle II schedule
Calendar year

201020112012

2013

201420152016

20172018

2019

Japan FY

JFY2010

JFY2011

JFY2012

JFY2013

JFY2014

JFY2015

JFY2016

JFY2017

JFY2018

JFY2019KEKB operation

・・・
・・・

SuperKEKB LER & HER upgrade construction
Start-up

Phase 1w/o QCS
w/o Belle II

Belle II upgrade construction

IR renovation(install QCS, etc.)
Belle II roll-in

Phase 2
w/ QCS
w/ Belle II (no VXD)VXD installation

Positron damping ring (DR) construction

w/ full Belle II

Phase 3DR commissioning

Injector Linac upgrade construction & operation

Injector Linac Experience at KEKB

operationfor years

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Schedule

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

Linac Schedule Overview 2018

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

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

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

Time →Location↓BeamLicenses
in steps

LowEmittance
Beams

LowEmittanceInjections

4+1 Ring
Injections

DRCommiss.
1 nC
Phase1

Without Top-up: Electron: Positron: Low current electron

Injector Linac Experience at KEKB

non damped e+ commiss.
at 1,2, 3,4,5 sectors
e- commiss. at A→5 sectors

1 - 2 nC
Phase2

1 - 4 nC
Phase3

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

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Linac Beam Property Requirements

Required injector beam parametersStage

KEKB (final)

Phase-I

Phase-II

SuperKEKB(final)

Beame+e–e+e–e+e–e+e–

Energy3.5 GeV

8.0GeV

4.0 GeV

7.0GeV

4.0 GeV

7.0GeV

4.0 GeV

7.0 GeVStored current

1.6 A

1.1 A

1A1A

1.8 A

1.3 A

3.6 A

2.6 A

Life time (min.)

150

200

100

100––

66

Bunch charge(nC)

primary e- 10

1

0.5

1

primary e- 8→11→ 0.4

Norm. Emittance(γβε) (µrad)

1400

310

1000

130

200/40(Hor./Ver.)

Energy spread

0.125%

0.125%

0.5%

0.5%

Bunch / Pulse

2222

Repetition rate

50 Hz

Simultaneous
3 rings
top-up injection(LER, HER, PF)(PPM)
Injector
Linac Experience at KEKB

primary e- 10→44150100/15(Hor./Ver.)

40/20(Hor./Ver.)

0.16%

0.1%

0.16%

0.07%

222225 Hz

25 Hz

50 Hz

No top-up

Eventually

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

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Subjects to Consider at Injector
Phronesisu (As of 2014)

SafetyDR ECS/BCS

Timingmonitor

Phase-IISchedule

u Phronesis needed(Greek: Practical wisdom,
Ability to understand theUniversal Truth)

BBA

RTL abort

Phase-I
Feb.2016GR̲A1 5nC

Bunch
compression

Strategicmaintenance

1 nC e+manipulation
3-ringinjection

Orbit control

GR̲A1 1nC e-

2nC e+
TemporalBalance

LLRF monitor

Low emittanceJun.2017
Nov.

DRu Have to consider
too many subjects !

BPM

Alignment

GR̲A1 8 nC

GR̲A1 10nC

Availability

Conditioning

Laserdevelopment

Energy spread
Resources

FC / LAS

Beamstability

DC FODO

4 nC e+PF Top-up

Compatible
Optics4-ringinjection

PF-AR 6.5GeV

Injector Linac Experience at KEKB

GR̲A1 for PF

Phase-III

Oct.2018

Pulsed bend

Pulsed PS
development

Pulsed quad

GU̲3T dual feed
modulator

Equipment
stability

KL/AC̲44
replacement

BudgetPF-AR 3GeV

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Positron Enhancement

32

Positron generation for SuperKEKB

Y.Enomoto et al.

side view
10 nC
primary e-bridge coils

DC QM spoilersolenoid
LAS Accel.
structuretargetprimarye- beame+beamhole

positronproduction
5 nC injection e-Target
Flux
Concentrator

pulsed ST
pulsed QM

Flux
Concentrator
BridgeCoilse+ beam

New positron capture section after target with
Flux concentrator (FC) and large-aperture S-band structure (LAS)
Satellite bunch (beam loss) elimination with velocity bunching
Pinhole (2mm) for passing electrons beside target (3.5mm)
Recently, facing discharge difficulties at maximum field
Injector Linac Experience at KEKB

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One of Key Component: Photo Cathode RF Gun

Development of Photo-cathode RF Gun
M.Yoshida et al.

u Succeeded in injection during SuperKEKB Phase 1 and 2 commissioningu Employs Yb-doped-fiber and Nd/Yb:YAGlaser, Ir5Ce cathode, QTWSC or cut diskcavities
u Stability improving
u Beam instrumentation
improvements andcomparison withsimulation codes underway Bunch width
Beam orbit measurementu Secondary RF gun was constructed
as a backup
u Incorporate suggestions by review committee
for availability and so on

Thermionic gun
Primary RF gun

Quasi traveling wave
side couple cavity

Secondary RF gun
Cut disk cavity

Injector Linac Experience at KEKB

Ir5Ce
CathodeElectron Guns

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Pulsed Magnet Development

Development and installation of pulsed magnets
v Pulsed magnets and power supplies will be installed in 2017 for resource optimizationv 30 quads, 36 steerings, 2 bends, 13 girders are being fabricated and installedv Quads with advanced design at 1 mH, 330 A, 340 V, 1 ms with energy recovery up to 75%
v Small form factor of 19 inch width and 3U height eachEnomoto, Natsui et alv Steering power supplies were also developed in-housev Essential for SuperKEKB low emittance injection and for simultaneous injection
v 4+1 ring simultaneous injections with virtual accelerator concept³ Long term tests at a stand³ Satisfies specifications³ Control synchronization
Injector Linac Experience at KEKB

³ Beam test with two quads³ Successful fast beam switches³ Switching features are comfirmed³ Girders are tested as well
³ In-house drawings to save rsc.
³ 0.1mm alignment precision³ Ready for Phase-3 upgrade

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Pulse-to-pulse modulationu Four PPM virtual accelerators
for SuperKEKB project
Based onDual-tier controls withEPICS and event-system

Event-basedControl System

Every
20 ms

F.B
e− GunARC

Independent parameter setsfor each VA (20ms)>200 parameters
for equipment controls
many morefor beam controls
maybe with additional PPM VAof stealth beam
for measurement

F.B

PF Injectione– (2.5GeV, 0.2nC)

F.B
e− GunARC

Damping ring

SuperKEKB-LER Injection

F.B

e– (3.5GeV, 10nC)

F.B

e+ Targete+ (4GeV, 4nC)

e− GunARC

SuperKEKB-HER Injection

F.B

e– (7GeV, 5nC)
e− GunARC

F.B

PF-AR Injection

F.B
e– (6.5GeV, 5nC)

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Summary

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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SummarySummary
u We learned a lot during KEKB injection operationu It contributed to achieve the world highest luminosity
u Injection into SuperKEKB is another challenge with higher beam
charge and lower transverse/longitudinal emittanceu Steady progress towards designed injection beam in steps
u Then, we may need to improve the injection furtherv ex. stealth beam measurement / optimizer, etc

u With some Phronesis we may enjoy beam commissioning

Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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Mt. Tsukuba

Thank you
SuperKEKB
dual ringsPF-ARPF

600m Injector
Linac

Conference papers at <http://www-linac.kek.jp/linac/>
Injector Linac Experience at KEKB

K.Furukawa, KEK, eeFACT2018, Sep.2018.

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