Upgrade of KEK Electron/Positron
Linac for the Both SuperKEKB andLight Sources
Kazuro Furukawa
Injector Linac, KEK<kazuro.furukawa@kek.jp>

Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

1

SuperKEKB Injector Upgrade and past KEKBSuperKEKB Injector Linac Construction
Injector Linac Commissioning
Injector Linac Operation Consideration

Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

2

Linac Upgrade Overview

Mission of electron/positron Injector in SuperKEKB
u 40-times higher Luminosity
v20-times higher collision rate with nano-beam scheme³ à Low-emittance even at first turn³ à Shorter storage lifetime

à Low-emittance beam from Linac

vTwice larger storage beamà Higher beam current from Linac

uLinac challenges
vLow emittance e³ with high-charge RF-gun

vLow emittance e+³ with damping ringvHigher e+ beam current³ with new capture section

vEmittance preservation³ with precise beam control

v4+1 ring simultaneous injection
Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

3Past KEKBKEKB 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 for SuperKEKB, PF, PFAR

Keeps world
luminosity record
2.1 x 1034
K.Furukawa, KEK, WAO2016, Sep.2016.

4

Required injector beam parametersStage

KEKB (2010)

Iteme+

e–e+e–e+e–Energy

3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

Bunch charge

Primarye-10nC

1 nC→ 1 nCPhase-I (2016)

Primary e8nC
→ 0.4 nC

1 nC

SuperKEKB (final)

Primary e-10nC→ 4 nC

5 nC

Norm. Emittance(γβε)(µrad)

2100

200

2400

150

100/20(Hor./Ver.)

50/20(Hor./Ver.)

Energy spread

0.125%

0.125%

0.5%

0.5%

0.1%

0.1%

No. of Bunch / Pulse

222222

Repetition rate

50 Hz

Simultaneous top-up
injection

3 rings(KEKB e–/e+, PF)

Injector Linac for SuperKEKB, PF, PFAR

25 / 50 Hz

50 Hz

No top-up

4+1 rings(SuperKEKB e–/e+, DR,PF, PF-AR)

K.Furukawa, KEK, WAO2016, Sep.2016.

5Alignment and beam control

Emittance Preservation and Alignmentu If Device is off center of the beam
v Focusing magnet (quad) kicks the beam bunchv Accelerating structure (cavity) excites wakefield, to bend the tailu Distorted bunch in banana shapev Emittance dilution or blow-up, even 100 times larger³ Depending on the beam optics and the beam chargeu Alignment and orbit correction is crucial to preserve the emittancev The effect is proportional to the square of beam charge, 1 nC à 5 nC
Sugimoto et al.

BeamFocusing
MagnetAcceleratingStructure
Transverse beam distribution in time direction

Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

6Schedule

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

Linac Schedule Overview

e- commiss.
at A,B,J,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↓Beam
Licensesin steps

Low
Emittance
Beams

4+1 Ring
Injections

DRCommiss.
1 nC
Phase1

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

Injector Linac for SuperKEKB, PF, PFAR

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

2 nC
Phase24 nC
Phase3

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

K.Furukawa, KEK, WAO2016, Sep.2016.

7

SuperKEKB Injector Upgrade and past KEKBSuperKEKB Injector Linac Construction
Injector Linac Commissioning
Injector Linac Operation Consideration

Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

8

Linac Upgrade Overview

Linac Upgrade Progress towards SuperKEKB (1)u High-charge low-emittance RF gun development
v QTWSC cavity and Ir5Ce photo cathodedevelopments
v Laser development is underway

Quasi traveling wave
side couple cavity

Ir5CeCathodeu Positron generator commissioning
Positron generator

v Good agreement with the simulation resultsv Will solve discharge issues

u Precise alignment for emittance preservation
v Recovering after large earthquake in 2011v Reaching specification of 0.1~0.3mm
v Longer term stability will be solvedu Utility upgrade during FY2014
v for electricity (+1.5MW) and cooling water (+1400L/min)
Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

9Linac Upgrade Overview

Linac Upgrade Progress towards SuperKEKB (2)u High-power microwave modulator upgradesu Low-level RF controls/monitor upgrades
v Pulse-to-pulse modulation (PPM) between 4+1 rings
v More spaces for increased number of devices

u Beam instrumentationv Large/small aperture beam position monitors (BPM)v Precise/fast and synchronized BPM readout systemv Wire scanners and beam loss monitors
v Streak camerasv (Deflectors, etc.)

u Pulsed magnet developments
v ~3 bends, ~30 quads, ~40 steerings
v Even with energy recovery

u Event-based control and timing system upgrades
Pulse magnet tests
v Combination of MRF & SINAP modules
v Essential for PPM operationv Precise timing & synchronized controlsv Bucket selection at DR and MR

Injector Linac for SuperKEKB, PF, PFARSINAP event modules

Beam wire scanner

K.Furukawa, KEK, WAO2016, Sep.2016.

10Positron Enhancement

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Positron generation for SuperKEKB
bridge coilsside view
10 nC
primary e-DC QM

spoilersolenoidLAS Accel.
structuretarget

primarye- beame+beamhole

positronproduction
5 nC injection e-Target
FluxConcentrator

pulsed ST
pulsed QM

FluxConcentrator
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)
Resolving recent discharge difficulties at maximum field
Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

11RF gun for low-emittance electron

RF-Gun development strategy for SuperKEKB
u Cavity : Strong electric field focusing structure
vDisk And Washer (DAW)=> 3-2, A-1(test)
vQuasi Traveling Wave Side Couple (QTWSC) => A-1
vCut Disk Structure (CDS) => A-1 (test)=> Reduce beam divergence and projected emittance dilution

u Cathode : Long term stable cathodevMiddle QE (QE=10-4〜10-3 @266nm)
vSolid material (no thin film) => Metal composite cathode=> Started with LaB6 (short life time)=> Ir5Ce (Ir2Ce) has very long life time and QE>10-4 @266nm

u Laser : Stable laser with temporal manipulation
vFiber laser oscillator / amplifier = Yb dopedvLD pumped laser medium => Nd / Yb dopedvTemporal manipulation => Yb doped=> Minimum energy spread
Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

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RF gun for low-emittance electron

Photo cathode RF gun development

Cascaded frequency doublers
Quasi traveling wave side couple cavity
Yb fiber and Yb:YAG think disk laser

Ir5CeCathodeIr5Ce photo cathode
Injector Linac for SuperKEKB, PF, PFAR

u 5.6 nC / bunch was confirmed
u Next step: 50-Hz beam generation &Radiation control
K.Furukawa, KEK, WAO2016, Sep.2016.

13

SuperKEKB Injector Upgrade and past KEKBSuperKEKB Injector Linac Construction
Injector Linac Commissioning
Injector Linac Operation Consideration

Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

14

Subjects to Consider
Phronesis

SafetyDR ECS/BCS

TimingmonitorPhase-IISchedule

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

BBA

RTL abortBalance

LLRF monitor

Low emittanceJun.2017
Nov.

DRu Have to consider
too many subjects !

BPM

Alignment

Temporalmanipulation

1 nC e+Phase-I
Feb.2016

GR̲A1 5nC

Bunch
compression

GR̲A1 8 nC

Resources

GR̲A1 10nC
Laser
development

Energy spread

FC / LAS

PF-AR 6.5GeV

Injector Linac for SuperKEKB, PF, PFAR

Pulsed bend

Beamstability

DC FODO

4 nC e+Phase-III
Oct.2018

Availability

Conditioning

PF Top-up

4-ringinjection

Strategic

maintenanceGR̲A1 1nC e-

2nC e+

3-ringinjection

Orbit control

Compatible
OpticsGR̲A1 for PF

Pulsed PSdevelopment

Pulsed quad

GU̲3T dual feed
modulator

Equipment
stability

KL/AC̲44
replacement

BudgetPF-AR 3GeV

K.Furukawa, KEK, WAO2016, Sep.2016.

15

Energy management
uBeam at the end of linac is dependent on …
vmaximum possible energy by accelerating structurevLLRF-beam crest
venergy spread minimization condition by LLRF
vvacuum, discharge, power-supply statisticalconditions³reviewed daily to protect equipmentuEnergy profile along linac affects …
voverall beam optics conditions
vemittance, stability, …
Injector Linac for SuperKEKB, PF, PFARK.Furukawa, KEK, WAO2016, Sep.2016.

16

Emittance management
uBeam emittance is dependent on …
vequipment alignment, 0.3mm for 500m, 0.1mm for 10m³ alignment drift should be monitored

vinitial orbit to cancel beam profile distortion
vbeam energy profile along linac should be kept
vbeam position monitors for orbit-drift feedback loops
vPPM operation between very different energies and charges
vbalance between fast/pulsed magnets and static magnets
vcontinuous database improvement
valgorithm should be polished

Injector Linac for SuperKEKB, PF, PFARK.Furukawa, KEK, WAO2016, Sep.2016.

17

Linac Optics Measurement / Managementu Wire scanner is used to manage twiss parameters along linac
u ~6 sets of wire scanners will be installedu Wire scanner measurements performed everyday
u If necessary (if "Bmag" is large), re-matching is performed by operatoru For pulse-to-pulse measurement, X-band deflector will be installed later
Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

18

Typical SuperKEKB Phase-1 Daily Operation
More than300mA stored thisweek in the bothe-/e+ rings(~1A in June)
In daytime
increases beam
current, andperforms optics
studies
In night time
continue vacuum
scrubbingNo collision yetCollision expected
at end of JFY2017
Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

19

SuperKEKB Injector Upgrade and past KEKBSuperKEKB Injector Linac Construction
Injector Linac Commissioning
Injector Linac Operation Consideration

Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

20

Schedule

Radiation control licensesu Step-by-step upgrade of beam limitsv (Reduced during upgrade construction after KEKB injection)u Final goal in linac is 1250/625 nA before/after targetu License applications
vFall.2013. 10 nA at #28 dump, 1250 nA at #A2 dump
vSpring 2014. New utility rooms, 50 nA at #61 straight dump
vJun.2015. 200 nA at #15 targetvEarly 2016. 800 nA at #15 target, 625 nA at #61
vSometime 2017.(?) 1250 nA at #15 targetu Shield, shield, shield, shield …
v Gun, 180deg-arc, Target, Electron stopper, Collimator, etc.
Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

2120000

818000716000Operation Time / year [hrs]14000

Total Operation Time [hrs]6

Machine Failure [%]12000

510000

48000

36000

24000
2000

KEKB

TRISTAN

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0

PF

FY

Machine Failure [%]Total Operation Time / 10 [hrs]Operation Time / year [hrs]Injector Linac Operation History

10Earthquake

Routine maintenance was important to improve the reliability(Failure rate includes rf trips)
Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

22

SuperKEKB and PF/PF-AR Injectionsu Particle physics experimentu Photon science experiments
vLong-term fixed user group
vShort-term and many groups
vPerformance oriented
vStability oriented
v For yearly integrated luminosity vFor maximum performance
performance
during assigned beam timevMinimum prevention
vRoutine scheduled
maintenancemaintenance
vCan develop common undervBit of distance between
standing between experimentexperiment and accelerator
and accelerator groups
groupsvEnthusiasm for improvements
vPeaceful operationvEveryday is a training
vLearn through document³ Light-source injection was performed even during SuperKEKB upgrade

Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

23

Injection for Both Experiments
uProper operation schedule to meetexperimental characteristics of those storage
rings
uSearch for common ground with respect for
those experimentsuShould find and confirm solutions in gradualchangesuImprove the machine using virtual accelerator
concept, if applicable

Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

24

Pulse-to-pulse modulation

Event-basedControl Systemu Four PPM virtual accelerators Every
20 ms
for SuperKEKB project
F.B
e− GunBased onDual-tier controls withEPICS and event-system

ARC

F.B

PF Injectione– (2.5GeV, 0.2nC)

F.B
e− GunDamping ring

Independent parameter sets ARC SuperKEKB-LER Injection
for each VA (20ms)
e (3.5GeV, 10nC)>200 parameterse TargetF.B
for equipment controls
e Gunmany more
ARC
SuperKEKB-HER Injection
for beam instrumentation

F.B–+e+ (4GeV, 4nC)

−maybe with additional PPM VAof stealth beam
for measurement

F.B

e– (7GeV, 5nC)
e− GunARC

F.B

PF-AR Injection

F.B
e– (6.5GeV, 5nC)

Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

25

Recent works

Field works on busy days
Positron generator
at #15 region

Iron shield

Positron generator complex

Guns
at #A1 region

Thermionic gun
for high-current beam

RF gunfor low-emittance beam

Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

26

SummarySummary
u We learned a lot during KEKB construction and operationu It contributed to achieve the world highent luminosityu Injection into SuperKEKB is another challenge with higher beam
charge and lower emittanceu Steady progress towards designed injection beam in steps
v Alignment: almost confident on the required precision (0.1-mm local, 0.3-mm
global), need to maintain for longer termv Positron generator: another license test, need discharge analysis
v RF gun: following recommendations at review meetings

u Will balance between final beam quality and progressive operationu Will balance between particle physics and photon scienceu With some Phronesis we may enjoy beam commissioningInjector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

27

Mt. Tsukuba

Thank you
SuperKEKB
dual rings
PF-AR
PF

600m Injector
Linac

Conference papers at <http://www-linac.kek.jp/linac/>
Injector Linac for SuperKEKB, PF, PFAR

K.Furukawa, KEK, WAO2016, Sep.2016.

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