Electron/Positron Injector Linac
andSuperKEKB Domestic Review Meeting
Kazuro Furukawa
Injector Linac, KEK

Injector Linac Status / Domestic Review

B2GM, October.2017.

1

Injector Linac Overview
uInjector linac configuration

vMajor upgrade items³Photo-cathode RF-gun for low-emittance e³Flux concentrator, LAS structure, solenoids, quads for e+³Pulsed magnets for adequate beam optics for each beam
³High-precision beam position monitor³High-precision beamline alignment for low emittance
Injector Linac Status / Domestic Review

B2GM, October.2017.

2

Required injector beam parametersStage

KEKB (final)

Phase-I

Phase-II

SuperKEKB(final)

Beam

e+

e–

e+

e–

e+

e–

e+

e–

Energy3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeVStored current

1.6 A

1.1 A

1A

1A

–

–

3.6 A

2.6 A

Life time (min.)

150

200

100

100

–

–

6

6

Bunch charge (nC)primary e- 10→1

1

primary e- 8
→ 0.4

1

0.5

1

primary e- 10→44Norm. Emittance(γβε) (µrad)

1400

310

1000

130

200/40(Hor./Ver.)150

100/15(Hor./Ver.)

40/20(Hor./Ver.)

Energy spread

0.125%

0.125%

0.5%

0.5%

0.16%

0.1%

0.16%

0.07%

Bunch / Pulse

2

2

2

2

2

2

2

2

Repetition rate

50 Hz

25 / 50 Hz

25 / 50 Hz

50 Hz

Simultaneous topup injection (PPM)

3 rings(LER, HER, PF)

No top-up

Eventually

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

Injector Linac Status / Domestic Review

B2GM, October.2017.

3

Domestic Accelerator Review

Injector Linac Status / Domestic Review

B2GM, October.2017.

4

SuperKEKB Domestic Review
uThe third domestic review meetingw On September 8th
w Reviewers of Atsushi Enomoto, Katsunobu Oide (chair), Kotaro Satoh,
Fujio Naito, Tatsuo Nakada, Junji Haba, Kentaro Harada, Yosuke
Honda, Shinichiro Michizono
w <http://accphys.kek.jp/indico/conferenceDisplay.py?confId=122>

vPositron source
vPhoto cathode RF gun
vAccelerating structure
vPulsed magnets

vDR timing system
vQCS
vLuminosity tuningvElectron cloud instability
in Phase 1 operationvBeam background, MDI³Two of them received recommendations
Injector Linac Status / Domestic Review

B2GM, October.2017.

5

Positron Enhancement

6

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

DC QM

spoiler

Kamitani, Enomoto et al.

solenoid
LAS Accel.
structuretargetprimary
e- beam

e+

beam
hole

positronproduction
5 nC injection e-Target
Flux
Concentrator

pulsed ST
pulsed QM

Flux
Concentrator
BridgeCoils

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)
Replacement mechanism even under higher radiation
Resolving recent discharge difficulties at maximum field
Injector Linac Status / Domestic Review

e+ beam

B2GM, October.2017.

6

Positron Source status
u Breakdown problem in Flux Concentrator
during 2017 April operation after
beamline installation(Though we had no problem during teststand operation at full-spec current.)u No e+ beam operation during April-May
run.
u Inspection of damaged FC

Target
Flux
Concentrator

returnyoke

v cooling down of residual-radiation since May 15
v removal of FC base part from e+ station in Junev visual search for damaged partv detailed inspection in August
v recovery trial

u Re-installation of FC in August for
Phase-2v The operation current will be around half of thenominal. Nevertheless, a sufficient beam for
Phase-2 should be available.
Injector Linac Status / Domestic Review

B2GM, October.2017.

7

Positron source
uRecommendationvAvoid a fatal destruction by securing the dischargeinterlock activation within a pulse.
³——> The interlock system was re-examined, and it isbelieved that it did work within a pulse. (However, thepulse-to-pulse recording system was not working at thetime. It should be made robust in the future.)

uConsiderationvFC may provide 20% increase from 6 kA to 12 kA³Balanced man-power distribution should be necessary
Injector Linac Status / Domestic Review

B2GM, October.2017.

8

One of Key Component: Photo Cathode RF Gun

Development of Photo-cathode RF Gun
Yoshida et al.

u Succeeded in injection during SuperKEKB Phase 1 commissioning for 11 daysu Employs Yb-doped-fiber and Nd/Yb:YAG
laser, Ir5Ce cathode, QTWSC or cut disk
cavitiesu Stability improving
u Beam instrumentation
improvements andcomparison withsimulation codes underway Bunch width
Beam orbit measurementu Secondary RF gun is being constructed
as a backup
u Incorporate suggestions by review committee
for availability and so on

Thermionic gun
Primary RF gun

New secondary RF gun
Cut disk cavity

Injector Linac Status / Domestic Review

Ir5Ce
CathodeElectron Guns

B2GM, October.2017.

9RF gunuRecommendations
vNew technologies seem to be introduced too often.
Further discussions on available facilities arenecessary.
³==> Weekly meetings are held at the linac open space, inwhich members from other groups participate. Dr. Yosuke
Honda, one of the reviewers, further contributes to the laser
discussion weekly.

vConsidering whole operation would stop on the gun
failure, an existent technology should be employed³==> As was recommended in past review meetings, existenttechnologies were applied for Phase-2. However, we arestill open to Phase-3 options.
Injector Linac Status / Domestic Review

B2GM, October.2017. 10

Injector Linac Issues

Injector Linac Status / Domestic Review

B2GM, October.2017. 11

Longest shutdown for SuperKEKB
uMany major constructions³for 5 months from May to October 2017

vRemoval of a temporary thermionic gun of #3T
vRemoval of all quads from 3, 4, 5 sectors
vInstallation of 30 pulsed quads and 36 correctors
vInstallation of a energy compressor (#DN) at DR LTR
vInstallation of a bunch compressor (#DS) at DR RTL
vFinalize the backup RF gun at #AS
vInstallation of a streak camera & wire scanners
vFinalize 70 LLRF monitors and LLRF phase shifters
vInstallation of the event timing controls for DR
Injector Linac Status / Domestic Review

B2GM, October.2017. 12

Waveguide fabrication issue
uWrong waveguide fabrication
vfound on Sept.19 in LLRF test
³Schematics from KEK and from the maker were correct

vWaveguide flanges need to connect the both vacuum
and RF with a help by 2-mm contactor
vwith slight taper surface design of 0º22"
vLater, 31 waveguides out of ~100 were found to bewrong³62 flanges were wrong³1 waveguide of them is a backup

vOpposite angle was programmed in NC machinesvIt can take 5 months to re-fabricate them all
Injector Linac Status / Domestic Review

B2GM, October.2017. 13

Linac side

Contactor

Injector Linac Status / Domestic Review

FlangeDR sideB2GM, October.2017. 14

ECS at LTR

Injector Linac Status / Domestic Review

B2GM, October.2017.

BCS at RTL

Injector Linac Status / Domestic Review

B2GM, October.2017.

Recovery #1
u Several countermeasures were examinedvFlange modification, flange replacement, contactor modification,etc.
vEspecially, contactor modification possibilities are investigated indetail, but found to be impracticalu At first lower-power operation was tested
vOn October 2nd
vNominal operational power and reflection (VSWR) should be 30
MW and 1.05 respectively
vMinimum power for Phase-2 is 8 MWvA single connection test was performed up to 3 MW with
continuous discharges at 1 Hz and VSWR of 1.7

u In parallel new fabrications were preparedv Initial plan suggests the beam availability at the end of January
Injector Linac Status / Domestic Review

B2GM, October.2017. 17

Test standWaveguides in cave

Reflection out of range
Forward power
Repetition
VacuumInjector Linac Status / Domestic Review

Reflection

History
strip chart
B2GM, October.2017.

Recovery #2
u Rearrangements and new fabrications of waveguides will
be performed
v32 were removed (30 have bad flanges) on Oct.7
v10 (original length) will be fabricatedv4 (new, various lengths) will be fabricatedv20 (old, various lengths) will be reused
vbackups will be fabricated in parallelu It was suggested to make system tests within this year
vZero-power beam delivery may be possible on Dec.20 to the endof LTRvAlmost synchronized with DR construction (?)
vStill barely acceptable with MR Phase-2 operation (?)

Injector Linac Status / Domestic Review

B2GM, October.2017. 19

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Injector Linac Status / Domestic Review

B2GM, October.2017. 20

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 beam with 4-5 times more beam current³ New high-current photo-cathode RF gun³ New positron capture section³ Damping ring construction³ 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

The single injector would behave as
multiple injectors to multiple storagerings by the concept of virtual
accelerator
Injector Linac Status / Domestic Review

B2GM, October.2017. 21

One of Key Component: Pulsed Magnets

Development and installation of pulsed magnets
v Pulsed magnet power supplies are scheduled in FY2017 for resource optimizationv 30 quads, 36 steerings, 2 bends, 13 girders are fabricated and installed in 2017v Quads with advanced design at 1 mH, 330 A, 340 V, 1 ms with energy recovery up to 75%
v Essential for SuperKEKB low emittance injection and simultaneous injections
v 4+1 ring injections with virtual accelerator concept
v Risks against schedule and possible backup operation procedure are also investigated³ Long term tests at a stand³ Satisfies specifications³ Some more control capability³ Synchronous operation in 2017

³ Beam test with two quads³ Girders are tested as well
³ Successful 25 Hz beam switches³ In-house drawings to save rsc.
³ Basic features are completed³ 0.1mm alignment precision³ Event timing synchronization needed ³ Ready for Phase-3 upgradev On going as expected, with long-term test in September for a month
Injector Linac Status / Domestic Review

B2GM, October.2017. 22

Thanks

Injector Linac Status / Domestic Review

B2GM, October.2017. 23

Injector Linac Status / Domestic Review

B2GM, October.2017. 24

Schedule

Linac Schedule Overview as of Jun.2017
u Long (5-month) shutdown for the first time in SuperKEKB projectv Installation of many important components
during this shutdownv 9-month shutdown in 1997 during KEKBv DR construction, resource availability, etc
Time →
Location↓
Beam
Licensesin steps

Low
Emittance
Beams

4+1 Ring
Injections

DR
Commiss.
1 nC
Phase1

Without Top-up: Electron: Positron

Injector Linac Status / Domestic Review

2 nC
Phase24 nC
Phase3

Direct PF-AR BT: Low current electron

B2GM, October.2017. 25

Photo-cathode RF Gun

Progress of Photo-cathode RF Gun

Yoshida et alu Succeeded in injection during SuperKEKB Phase-1 commissioning for 11 days
Thermionic gunu Employs Yb-doped-fiber and Nd/Yb:YAG
laser, Ir5Ce or Ir2Ce cathode, QTWSC or
cutdisk structuresu Secondary RF gun was constructed foravailability with Ir2Ce and cutdisk
Primary RF gun
QTW RF gun

New secondary RF gun
0 deg injection

IrCe
CathodeCDS RF gun

Cutdisk cavity

Beam orbit measurement
Injector Linac Status / Domestic Review

B2GM, October.2017. 26

Photo-cathode RF gun: Laser

uYb:Fiber + Nd:YAG multi-pass amplifier
Fiber
Amp

Nd.YAG Φ2mm
×2passE.O.

Pockels Cell

Nd.YAG Φ4mm
×8pass~30 μJ

Nd.YAG Φ4mm
×4pass ~700 μJ

SHG
Nd.YAGΦ4mm

1.57 +/-0.032 nC

2 mJ

FHG

1.0 mJ

200 μJ
Beam charge stability- Stable laser system for Phase-II.
- 2 nC, 2 bunch stable operation will be expected.
(2-bunch operation was already demonstrated.)- Two oscilllator (one will be commercial oscillator).
- Two amplifier lines.
- Spatial filter for one amplifier line.
Injector Linac Status / Domestic Review

B2GM, October.2017. 27

Removal of temporary pre-injector (3T/
32RFgun)u KEK e+/e- linac has been divided into two
regions by a wall at 3T.
u 3T/32 pre-injector has been used for PF, AR
injection during upgrade construction andinitial beam commissioning in linac
upstream region.
u 3T/32 pre-injector is removed in May 2017
for DR commissioning.
u a regular accelerator module (3-2) isinstalled in this region for injection beamenergy margin.
u AT/A1 pre-injector is used for all thestorage rings (HER, LER, PF, AR) after
autumn 2017. They share the same fate incase of linac troubles.
u PF, AR beam operation from October.
u DR commissioning from December 2017.
Injector Linac Status / Domestic Review

wall
3T pre-injector
32 pre-injector

After the wall and
3T/32 pre-injector
removal, linac tunnel
is united as one.

B2GM, October.2017.

28

29

Pulse magnet systemu For pulse-by-pulse beam-mode switching andindependent optics/orbit tuning,pulse magnet system is introduced.
u All the quads in Sector-3, 4, 5 are replaced by pulse-Qs
and pulse-steerings are introduced.

Pulse magnets (Q+ST+ST+Q)

u AT/A1 pre-injector merger line bends are replaced fromDC to pulse magnets.
u Pulse magnets installation completed.
u Pulse power supply setting-up on-going.
u Test operation of pulse magnet system in September.
u Beam commissioning with pulse magnet system start in
October 2017.
Injector Linac Status / Domestic Review

Pulse current driver
B2GM, October.2017.

Event timing controls
for pulsed quad & steering magnet controls
Satoh, Enomoto et al.

MRF PXI-EVR-230 was added
Control software is based on:
Windows 8.1 Professional
EPICS base R3.14.12.6 for EVR control
LabView for DAC/ADC control• Device driver for cPCIEVR-300 (Swiss FEL) was
modified for our card
• Fundamental functions canalready work well.
• Data buffer functionality is
now under implementation.
Injector Linac Status / Domestic Review

30

B2GM, October.2017. 30

Pulsed magnet rack
Edge switch

DC
Power Supplies

PulsedmagnetdriverPXI chassis(PXIe-1082)
ControlPC

Remote controller
DAC (PXI-6733)
ADC (PXIe-6356)
PXI-EVR-230

u 13 racks are newly installedu Small form-factor (4U) power supplies aretested more than 2 months at 50Hz
Interlock signal processing(CompactRIO based system)
Injector Linac Status / Domestic Review

B2GM, October.2017. 31

Development of 571.2MHz Master phase shifter• All linac clocks are generated from 571.2
MHz master oscillator• Clock is adjusted every minutes tocompensate the ring circumferences, andthe phase should be adjusted to meet thelengths of beam transports of electron andpositron.
• Stabilities of 0.1%rms in amplitude and0.02 degree rms in phase

φ2 changed at 50 Hz
3,4,5セクター
2856MHz移相器

Injector Linac Status / Domestic Review

B2GM, October.2017.

571.2MHz Phase shifter

571.2MHz

Injector Linac Status / Domestic Review

B2GM, October.2017.

KL_DS, KL_DN , KL_32 Installation

ECS

BCS

Voltage required [MV]

41

21.5

# 2m accelerator
structure2

1

Accelerator field [MV/
m]

10.2

10.75

Operation power [MW]

29.0

19.0

Pulse width [µs]

0.8

0.8

Rep. rate [Hz]5050

Injector Linac Status / Domestic Review

KL_DS/BCS

KL_DN/ECSKL̲32
B2GM, October.2017.

Bucket selection in Phase-2 with DRu Without DR, simply wait up to 5120 x 96 ns ~ 490 μs
v 96 ns : highest common frequency between linac – ringe− GunKEKB

ARCe+ BT (3.5GeV, 0.6nC)

Primary e– (3.5GeV, 10nC)
e+ Target

Kaji et alu With DR, in order to select arbitrary bucket in MR, have to wait up
to ~4.5 ms, even if a bucket in DR was carefully selectedv Power supply can wait only 2 ms, one of only 2798 buckets in 5120 buckets can beselected, may have to change LLRF condition at latter half of linac every pulse
96ns +e DR (1.1 GeV, 4nC)
>100nse− GunARC
Primary e– (3.5GeV, 10nC)>100ns
96ns

SuperKEKB
e+ BT (KEKB: 4GeV, 4nC)

e+ Targetv Can be a big challenge in LLRF precision
Injector Linac Status / Domestic Review

B2GM, October.2017. 35

New Schedule

Linac Schedule Overview as of Jun.2017

RF-Gun e- beamcommissioning
at 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

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

DR
Commiss.
1 nC
Phase1

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

Injector Linac Status / Domestic Review

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

B2GM, October.2017. 36

Summary

Summaryu We learned a lot during KEKB operationu Phase-2 injection into SuperKEKB is another challenge with higher
beam current and lower transverse and longitudinal emittanceu Steady progress towards designed injection beam in steps
v Alignment: almost confident on the measurement precision (0.1-mm local, 0.3-mm
global), may need mover to maintain it for longer termv Positron generator: need discharge analysis
v Thermionic gun: stably operated for primary electron for positron generationv RF gun: following recommendations at review meetings
v Pulsed devices: global and synchronized operationv New modulators for energy and bunch compressors on DR beamlines

u Will balance between final beam quality and progressive operationu Will select optimized route depending on available resourcesv Balance with injection operation for light sources, commissioning and developmentin parallel
Injector Linac Status / Domestic Review

B2GM, October.2017. 37