Overview of Injector Linac
Kazuro Furukawa
for Injector Linac

Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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Linac Overview

Mission of electron/positron Injector in SuperKEKBu 40-times higher LuminosityvTwice larger storage beamà Higher beam current at Linacv20-times higher collision rate with nano-beam scheme³ à Low-emittance even at first turn³ à Shorter storage lifetimeà Low-emittance beam from Linac
à Higher Linac beam currentuLinac challengesvLow emittance e³ with high-charge RF-gunvLow emittance e+³ with damping ringvHigher e+ beam current³ with new capture sectionvEmittance preservation³ with precise beam controlv4+1 ring simultaneous injection
Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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Linac Overview

Linac Upgrade for SuperKEKB
High current gun,
10nC for e+	

B
J-arc
1.5 GeVA

Primary e– for e+
3.2 GeV, 10nC x 2
BunchCompression

C1

1.1 GeV
e+ damping ring

Low emittance RF-gun
5 nC for e–IrCe cathode, Fiberlaser, QTWSC cavity
BunchCompression

2New e+Capturewith FC & LAS

SY2EnergyCompression

3PF50 Hz (e+ or e-)
Pulse-to-pulse
modulation	

2.5 GeV
0.1nC x 1

EnergySY3 Compression

45Linac Upgrade towards SuperKEKB

HER

PF-AR

7.0 GeV
5nC x 220 um

6.5 GeV
5nCu Higher Injection Beam Currentv To Meet the larger stored beam current and shorter beam lifetime in MRv 4~8-times larger bunch current for electron and positronu Lower-emittance Injection Beamv To meet nano-beam scheme in the ringv Positron with a damping ring, Electron with a photo-cathode RF gunv Emittance preservation by alignment and beam instrumentationu Quasi-simultaneous injections into 4 storage rings (PPM)v SuperKEKB e–/e+ rings, and light sources of PF and PF-ARv Improvements to beam monitors, low-level RF, controls, timing, etc

LER

4.0 GeV e+
4nC x 2

Ir5Ce

K.Furukawa, MAC review, Feb.2015.

FC3

Linac Upgrade

Linac Upgrade Progress towards SuperKEKB (1)u High-charge low-emittance RF gun developmentvQTWSC cavity and Ir5Cephoto cathode works well

Quasi traveling wave
side couple cavity

Ir5CeCathodeu Positron generation confirmation for the first timevGood agreement withthe simulation results

Positron generator

Signal fromprimary electron

Signal from positronwith opposite polarityu Precise alignment for emittance preservationvRecovering after earthquakevReaching specification of 0.2mm
u Utility upgrade during summer 2014v for electricity (+1.5MW) and cooling water (+1400L/min)
Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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Linac Upgrade

Linac Upgrade Progress towards SuperKEKB (2)u High power modulator upgrades
Quasi travelng waveu Low-level RF controls/monitor
side couple cavityv Pulse-to-pulse modulation (PPM) between 4+1 ringsv More spaces for increased number of devicesu Beam instrumentationv Large aperture beam position monitors (BPM)v Precise/fast and synchronized BPM readout systemv Wire scanners and beam loss monitorsu Event timing systemv Combination of MRF and SINAP modulesv Essential for PPM operationv High timinng precisionv Bucket selection at DR and MRSINAP event modules

Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

5Alignment

Alignment progress in 2014u For the first time after earthquake at downstream sectorsu Several measurements during summeru Measurement reproducibility was confirmed up to ~0.2 mmu While there existed
several conflicting
measurements,
consistent scheme~5mm
has been establishedu Movement of tunnel
by several 10’s ofmicrometer wasobserved (→ mover)~10mmu Further work necessary
in 2015, for alignmentand girder replacement
Linac Upgrade towards SuperKEKB

Higo et al.

K.Furukawa, MAC review, Feb.2015.

6Positron Enhancement

T.Kamitani

Positron Generation

1) 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
Primary e- [nC] Positron [nC]
June 2014
Specification(at SY2)

0.6

0.12

x17

10.0

DR injection(2017?)
3)

Oct.~Dec.2014 : Linac commissioning
Jan.~May.2015 : Construction
Jul.~Sep.2015 : Construction

Linac Upgrade towards SuperKEKB

5.0
4.0x42

Efficiency

Parameters

20%

FC 6.4kA, Solenoids 370A,
LAS capture field 10 MV/m

50%
40%

x2.5

FC 12kA, Solenoids 650A,
LAS capture field 14 MV/m
Energy spread acceptance
0.5%

Jun. : Linac commissioning
Oct.~Jan.2016 : Linac commissioning
K.Furukawa, MAC review, Feb.2015.

RF-gun

Linac Upgrade for SuperKEKB
High current gun,
10nC for e+	

B
J-arc
1.5 GeVA

Primary e– for e+
3.2 GeV, 10nC x 2
BunchCompression

C11.1 GeVe+ damping ring

Low emittance RF-gun
5 nC for e–
IrCe cathode, Fiberlaser, QTWSC cavity
BunchCompression

2New e+Capturewith FC & LAS

EnergyCompression

SY23PF

50 Hz (e+ or e-)
Pulse-to-pulse
modulation	

2.5 GeV
0.1nC x 1

EnergySY3 Compression

54LER

4.0 GeV e+
4nC x 2

HER

PF-AR

7.0 GeV
5nC x 220 um

6.5 GeV
5nCu Low emittance RF-gun developmentv Photo-cathode: stability, long-lifetime, quantum efficiency

Ir5Ce³ LaB6, Ir5Ce and other possibilities, 5nC/bunch achievedv Laser : high-power, stability, bunch profile management³ Nd:YAG media, LD excitation, 1.5mJ / 30ps achieved³ Fiber laser development for profile controlv Cavity : field optimization³ Disk and washer (DAW) cavity³ Quasi traveling-wave (QTWSC) cavityv Operation : higher stability and reliability

DAW³ PF injection was tested, longer-term tests, backups, are planned
Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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Thermionic Gun

Preparation of Thermionic Gunu Under refurbishmentvRaise by 75cm not to conflict with straight RF-gun³ Instead of angled RF-gunv~ May.2015.

u May serve primary electron for positron generation
Thermionic gun

RF gunLinac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

9RF-gun Review

RF-gun Review Meetingu Thanks to reviewersvDr. Tsumoru Shintake, OIST, chairvDr. Matt Poelker, JLABvDr. Sasha Gilevich, SLACvDr. Yosuke Honda, cERL/KEKu Feb.19,20.2015.
u Phylosophy of simplicity and robustnessu Cavity and photo-cathod seems to be OKu Concentration on the laser
without temporal manipulationvPhase-1 and (partial) Phase-2 should be OK

Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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2014 Reviewer’s Comments (final-1)u Summaryv Overall, the ARC Review Committee congratulates the accelerator team onvery solid progress on construction of SuperKEKB and its injector and firmly
expects that beam commissioning of the rings will start in 2015.
v With key components of the injector now installed and operational, significant
effort should be devoted to achieving the necessary beam stability to support
commissioning of new and critical downstream components.

u Overview of InjectorvBut significant challenges related to achieving Super KEKB luminosity remain: operation at

higher bunch charge for both electron and positron beams, demanding emittance requirements,tight requirements on monitoring the beam position, and a demanding schedule that requires
commissioning of many new components including the positron source and positron damping ring.
The earthquake and Super KEKB construction has alerted KEK staff to tunnel motion, 0.1mm/day,comparable to the quadrupole and RF cavity alignment specification.

v To achieve Super KEKB luminosity requirement, the staff will pursue a phased
approach, beginning with “modest” bunch charge and emittance and working
their way to final goals over ~3 years.
³ Optimizing beam with many simulation works to achieve goal within available resources³ Staged beam commissioning with low à high charge and normal à low emittance
Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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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↓1 nC
Phase1: Electron: Positron: Low current electron

Linac Upgrade towards SuperKEKB

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

2 nC
Phase2

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

K.Furukawa, MAC review, Feb.2015.

12ScheduleInjector linac schedule and RF-gunu Feb.2016 – Jun.2016: Phase-1 commissioningv Non-low-emittance, 1nC electron/positron beams, without damping ring (DR)³ With combination of RF-gun and thermionic gun³ ex. Electron with 1nC RF-gun, Positron with ~6nC thermionic gunw (depends on downstream configuration after DR delay affecting PF/PF-AR injections)u Dec.2016 – May.2017, Damping ring commissioningv 1nC – 2nC positron beam, to/from DRu Jun/Oct.2017 – Feb.2018, Phase-2 commissioningv Low-emittance (20mm.mrad, 0.1%), 2nC electron/positron beams, with DR³ Low-emittance electron beam with RF-gun, 2nC³ Primary beam for positron with RF-gun or thermionic gun, 5nCu Oct.2018 – …, Phase-3 commissioningv Low-emittance (20mm.mrad, 0.1%), High charge electron/positron beams, with DR³ Low-emittance electron beam with RF-gun, 4nC³ Primary beam for positron with RF-gun or thermionic gun, 10nC
Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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2014 Reviewer’s Comments (final-2)u Commissioningv Drive laser stability issues are a key concern (timing stability, amplitude
stability and pointing stability).
³ à Combination with thermionic gunu RF gun and Emittance Preservationv However, the QTW laser system is very complex, and with complexity comesrisk. (…)
³ à Concentrate on laser system without pulse shapingw Recommendation at rf-gun reviewu Positron Sourcev A fire at the solenoid flux concentrator has introduced a ~ 4 month delay incommissioning.
³ à First positrons were observed³ à Careful safety investigations again³ à High-current radiation shieldu Timing Systemv There is still significant software development to complete and much hardware
to integrate.
³ à Successful tests with light source beams
Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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Fire in FY2013

Fire during flux concentrator developmentu One of small problems – Cables burned by 20cmv This was reported last year

Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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Near-misses at Linacu May.12.2014. Despiker at KL_A2
high power modulator
overheatedvAging à Devices in the same lot werereplacedu May.12.2014. Coil of a bending
magnet BM_28_4 overheatedvCommunication erroru Dec.9.2014. High power cable
overheated at the terminal of flux
concentrator power supplyvCorona discharge à Thicker cable

Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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Presentations for Injector Linacu Alignment 20'v Speaker: Toshiyasu Higou RF gun review 20'v Speaker: Matt Poelker (JLab)u Electron gun and transport 40'v Speaker: Mitsuhiro Yoshidau Positron source upgrade 40'v Speaker: Takuya Kamitaniu Injector commissioning 40'v Speaker: Masanori Satoh

Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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SummaryuSteady progress towards first MR injectionuFinishing earthquake disaster recovery in FY2014
uWill make staged improvements before 2018uWill balance between final beam quality andstaged operationuWill select optimized route depending on availableresources

Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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Mt. Tsukuba

Thank you
SuperKEKB
dual rings
PF-ARPF

Linac Upgrade towards SuperKEKB

Injector
Linac

K.Furukawa, MAC review, Feb.2015.

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Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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Linac Upgrade towards SuperKEKB

K.Furukawa, MAC review, Feb.2015.

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