K.Furukawa, KEK, RF-gun review, Feb.2015. Linac Upgrade towards SuperKEKB Injector Linac Kazuro...

K.Furukawa, KEK, RF-gun review, Feb.2015.Linac Upgrade towards SuperKEKB

Injector Linac

Kazuro Furukawafor Injector Linac

1


Thanks to the reviewers

Dr. Tsumoru Shintake, OIST, chairDr. Matt Poelker, JLAB

Dr. Sasha Gilevich, SLACDr. Yosuke Honda, cERL/KEK

2


40-times higher LuminosityTwice larger storage beam Higher beam

current at Linac20-times higher collision rate with nano-beam scheme

　 Low-emittance even at first turn Low-emittance beam from

Linac Shorter storage lifetime Higher Linac beam current

Linac challengesLow emittance e-with high-charge RF-gun

Low emittance e+with damping ring

Higher e+ beam currentwith new capture section

Emittance preservationwith precise beam control

4+1 ring simultaneous injection

Mission of electron/positron Injector in SuperKEKB

3

Linac Overview


Linac Upgrade for SuperKEKB

Low emittance RF-gun developmentPhoto-cathode: stability, long-lifetime, quantum efficiency

LaB6, Ir5Ce and other possibilities, 5nC/bunch achievedLaser : high-power, stability, bunch profile management

Nd:YAG media, LD excitation, 1.5mJ / 30ps achieved Fiber laser development for profile control

Cavity : field optimization Disk and washer (DAW) cavity Quasi traveling-wave (QTWSC) cavity

Operation : higher stability and reliability PF injection was tested, longer-term tests, backups, are planned

4

BunchCompression

AB

C 1 2 3 4 5HER7.0 GeV 5nC x 220 um

LER4.0 GeV e+4nC x 2

Primary e– for e+3.2 GeV, 10nC x 2

1.1 GeV e+ damping ring

Energy Compression

Bunch Compression

PF2.5 GeV0.1nC x 1New RF-gun

5 nC for e–, 10nC for e+IrCe cathode, Fiber laser, DAW cavity

New e+ Capture with FC

PF-AR6.5 GeV5nC

J-arc1.5 GeV

EnergyCompression

SY2

SY3

Ir5Ce

DAW


Linac Upgrade Progress towards SuperKEKB

High-charge low-emittance RF gun developmentQTWSC cavity and Ir5Ce

photo cathode works well

Positron generation confirmation for the first timeGood agreement with

the simulation results

Precise alignment for emittance preservationRecovering after earthquakeReaching specification of 0.2mm

Utility upgrade during summer 2014 for electricity (+1.5MW) and cooling water (+1400L/min)

5

Signal from primary electron

Signal from positron with opposite polarity

Ir5CeCathode

Quasi traveling wave side couple cavity

Positron generator


Linac Schedule Overview

6

RF-Gun e- beamcommissioningat A,B-sector

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

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

damped e+ commiss.at 1→5 Qe+ = 1~4nCe- commiss.at A→5 Qe- = 1~5nC

: Electron

: Positron

: Low current electron

2 nCPhase2

1 nCPhase1

Location↓

Time →

Phase1: high emittance beam for vacuum scrubPhase2,3: low emittance beam for collision

Schedule


Alignment High-precision alignment was not necessary in PF and

KEKB injections, and it was much damaged by earthquake in 2011.

Instead of flexible-structure girder before earthquake, rigid-structure was adopted with jack-volts and fixed supports.

Reflector pedestals are developed and mounted onto quad magnets and accelerating cavities for laser-tracker measurement.

Iterative measurement and adjustment with 500-m straight laser and position sensors should enable 0.3-mm global alignment.

Laser tracker should enable 0.1-mm measurement within 10-m girder unit.

Displacement gauges, hydrostatic leveling, inclinometer are also employed.

Remote measurement system and girder mover system will be necessary for longer term, and are under development.

7

Alignment


Alignment progress in 2014 For the first time at 3-5 sectors Horizontal axis: sensor number from sector C, 1-4, to

sector 5 (~80 m/sector)

Vertical axis: voltage (~displacement at 0.25~0.5mm/mV)

Some girders were not yet upgraded Moved up to 3 mm not to break vaccuum

8

Alignment

Displacement / mV

Sector C Sector 5


Alignment progress in 2014 For the first time after earthquake at downstream

sectors Several measurements during summer Measurement reproducibility was confirmed up to ~0.2

mm While there existed

several conflicting measurements, consistent scheme has been established

Movement of tunnel by several 10’s of micrometer was observed (→ mover)

Further work necessary in 2015, for alignment and girder replacement 9

Higo et al.

~5mm

~10mm

Alignment


Positron Generation4-times more positron is required at

SuperKEKB than KEKBSafety measure was taken after cable fire

during the test of Flux Concentrator (FC)New components in

100-m capture section were tested in steps

High voltage tests in tunnel in April

Beam tests with electronin May

10

Positron Enhancement


Positron generation for SuperKEKB

New positron capture section after target with Flux concentrator (FC) and large-aperture S-band structure (LAS)Satellite bunch (beam loss) elimination with velocity bunchingPinhole (2mm) for electrons beside target (3.5mm)Beam spoiler for target protection

Flux Concentrator

e+

5 nC injection e-

10 nCprimary e-

bridge coils

target

beamhole

pulsed ST

DC QM

pulsed QM

side view

spoiler

solenoid

LAS Accel. structure

11

positronproductionTarget

Flux Concentrator

BridgeCoils

primary e- beam

e+ beam

11



Positron Generation1) Installation of positron generator for SuperKEKB in

April 2014(Beamline construction since summer 2013)

(positron target, spoiler, Flux Concentrator, bridge coils, LAS structures [x6], DC solenoids [16+13],

e+/e- separator, quads [>90])

2) Commissioning of positron beam, observation of the first positron after reconstruction for SuperKEKB, further improvements expected

3) Oct.~Dec.2014 : Linac commissioningJan.~May.2015 : Construction Jun. : Linac commissioningJul.~Sep.2015 : Construction Oct.~Jan.2016 : Linac commissioning

T.Kamitani

Primary e- [nC]

Positron [nC] Efficiency Parameters

June 2014 0.6 0.12 20% FC 6.4kA, Solenoids 370A, LAS capture field 10 MV/m

Specification(at SY2) 10.0 5.0 50% FC 12kA, Solenoids 650A,

LAS capture field 14 MV/m

DR injection(2017?) 4.0 40% Energy spread acceptance

0.5%

x17 x42 x2.5



RF-Gun development strategy for SuperKEKB

Cavity : Strong electric field focusing structureDisk And Washer (DAW) => 3-2, A-1(test)Quasi Traveling Wave Side Couple => A-1 => Reduce beam divergence and projected emittance

dilution Cathode : Long term stable cathode

Middle QE (QE=10-4～ 10-3 @266nm) Solid material (no thin film) => Metal composite

cathode => Started from LaB6 (short life time)

=> Ir5Ce has very long life time and QE>10-4 @266nmLaser : Stable laser with temporal manipulation

LD pumped laser medium => Nd / Yb dopedTemporal manipulation => Yb doped

=> Minimum energy spread

RF gun for low-emittance electron


time=2.48098e-009

728 729 730 731 732 733

GPT z

11.3

11.4

11.5

11.6

11.7

Ene

rgy

[MeV

]

Emittance 5.5 mm-mrad

Size 0.4 mm

Energy spread 0.6%

Bunch shape

Gun Exit

5 nC 10 nC

Beam tracking simulation resultRF gun for low-emittance electron

M. Yoshida


Energy spread reduction using temporal manipulation

15

0

0.5

1

1.5

2

2.5

3

0 5 10 15 20 25 30

FWHM (ps)

σE/

E (%

)

Gaussian

Square

5nC10nC

15nC

20nC

20nC15nC10nC5nC

5nC electron 15nCPrimary beam for positron production

t

t

Energy spread of 0.1% is required for SuperKEKB synchrotron injection.


M. Yoshida


5.6 nC / bunch was confirmed Next step: 50-Hz beam generation

&Radiation control 16

Quasi traveling wave side couple cavity

Cascaded frequency doublers

Yb fiber and Yb:YAG think disk laser

Ir5Ce photo cathode

Photo cathode RF gun developmentRF gun for low-emittance electron

Part of multi-pass Amplifier


GU_A1 Laser Configuration as of Dec.2014

17



Photo cathode RF gun improvementCrucial for high-current low-emmittance

beamNew Ir5Ce cathode and new cavity QTWSC

were successfulBasic features were confirmed at 2 ~ 5 HzExpect beam parameter and stability

performance at 50 Hz, with multi-pass amplifiers and cooling system

Resolved the issue of oscillator synchronization

Staged laser system improvements with beam measurement system

18



R0 ARC Dispersion: need for investigation

Measurement (dot) compared with expected value (line)

19

R36

R16

Commissioning

Preliminary


Towards the injectionWe didn’t completed the preparation

of routine injection beam for Phase-1We prepare for routine operation while

continueing the development ex. Thermionic gun

Also considering the schedule for radiation control licensesMar.-Jun.2015, Jun.-Oct.2015

Need balance between development, operation, schedule, and budget

20

Electron gun rearrangement


Staged Radiation Control License towards SuperKEKB

Two licenses were approved in June 2014[1] Beam diagnostic station at #A2 just after

gunfor 1250nC/s at 50Hz 2bunches

[2] Beam dump at #28 just before damping ringfor 10nC/s with positrons

Radiation measurements especially at positron generatorIndispensable to estimate radiation at >100 times

higher beamBoth approvedSoon apply for the next license at ~Jun.201521



RF-gunCavities

KL-A1-B

KL-A1-A Phase shifters


Up to Dec.2014.


Installation of Thermionic GunUnder constructionJan.2015 – May.2015.

23

Thermionic gun

RF gun


Injector Division Group StructureMicrowave (RF): klystron, pulse-modulator, llrf,

(at linac, cERL, STF)Accelerator: structure/cavity, vacuum, magnet,

alignment, cooling water, (devices in tunnel), etc

Controls: computer controls, beam monitors, timing, alignment, etc

Injector: RF-gun, beam monitor, pulsed devices, etcM.Yoshida, X.Zhou, T.Natsui, R.Zhang, (D.Satoh), …

Operation: operation management, safety, etcRoutine/basic operation: out-sourced

Commissioning: traversal group between groups

24

KEKB


Linac Schedule Overview

25

RF-Gun e- beamcommissioningat A,B-sector

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

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

damped e+ commiss.at 1→5 Qe+ = 1~4nCe- commiss.at A→5 Qe- = 1~5nC

: Electron

: Positron

: Low current electron

2 nCPhase2

1 nCPhase1

Location↓

Time →

Phase1: high emittance beam for vacuum scrubPhase2,3: low emittance beam for collision

Schedule


Injector linac schedule and RF-gun

Feb(?).2015 – Jun(?).2015: Phase-1 commissioning Non-low-emittance, 1nC electron/positron beams, without damping ring

(DR) With combination of RF-gun and thermionic gun ex. Electron with 1nC RF-gun, Positron with 6nC (?) thermionic gun

(depends on downstream configuration after DR delay affecting PF/PF-AR injections)

Dec(?).2016 – May(?).2017, Damping ring commissioning 1nC – 2nC positron beam, to/from DR

Jun(?).2017 – Feb(?).2018, Phase-2 commissioning Low-emittance (20mm.mrad, 0.1%), 2nC electron/positron beams, with DR

Low-emittance electron beam with RF-gun, 2nC Primary beam for positron with RF-gun or thermionic gun, 5nC

Oct(?).2018 – …, Phase-3 commissioning Low-emittance (20mm.mrad, 0.1%), 4nC electron/positron beams, with DR

Low-emittance electron beam with RF-gun, 4nC Primary beam for positron with RF-gun or thermionic gun, 10nC

26

Alignment


SummarySteady progress towards first MR injection

Finishing earthquake disaster recovery in FY2014

Will make staged improvements before 2018

Will balance between final beam quality and staged operation

Will select optimized route depending on available resourcesIncorporate thermionic gun as well as RF gun

27


SuperKEKB dual rings

Mt. Tsukuba

InjectorLinac

PF-AR

PF

28

Thank you

K.Furukawa, KEK, RF-gun review, Feb.2015.Linac Upgrade towards SuperKEKB 29



ARC

e– (2.5GeV, 0.2nC)

e− Gun

ARC

e+ Target e+ (4GeV, 4nC)

e− Gun

PF Injection

SuperKEKB-LER Injection e– (3.5GeV, 10nC)

ARC

e– (7GeV, 5nC)

e− Gun

SuperKEKB-HER Injection

ARC

e– (6.5GeV, 5nC)

e− Gun

PF-AR Injection

Damping ring

Event-based Control System

Every20 ms

F.B

F.B

F.B

F.B

F.B

F.B

F.B

F.B

Four PPM virtual acceleratorsfor SuperKEKB project

maybe with additional PPM VAsfor stealth beammeasurements

based on Dual-tier controls withEPICS and event-system

Pulse-to-pulse modulation

33


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K.Furukawa, KEK, RF-gun review, Feb.2015. Linac Upgrade towards SuperKEKB Injector Linac Kazuro...

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