Progress of KEK Electron/Positron
Injector Linac
Mitsuhiro Yoshida
Injector Linac, KEK

Injector Linac Progress

July.2017.

1

Injector Linac Mission

Mission of Electron/positron Injector in SuperKEKB❖ For 40-times higher luminosity in SuperKEKB collider❖ Low emittance & low energy spread injection beam with 4-5 times more beam current New high-current photo-cathode RF gun
 New positron capture section
 Damping ring construction
 Optimized beam optics and correction
 Precise beam orbit control with long-baseline alignment
 Simultaneous top-up injection to DR/HER/LER/PF/PFAR❖ 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 Progress

July.2017.

2

Required injector beam parametersStage

KEKB (final)

Phase-I

Phase-II

SuperKEKB(final)Beame+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.)150200100100––

66

10.5

1

primary e- 10

primary e- 8

primary e- 10

4Bunch charge (nC)→1

1→ 0.4→4

Norm. Emittance(ge) (mrad)

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

2222

22

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 Progress

July.2017.

3

Schedule

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

Low
Emittance
Beams

4+1 Ring
Injections

DRCommiss.
1 nC
Phase1

Without Top-up: Electron

Injector Linac Progress: Positron

2 nC
Phase24 nC
Phase3

Direct PF-AR BT: Low current electron

July.2017.

4

Photo-cathode RF Gun

Progress of Photo-cathode RF Gun

Yoshida et al◆ Succeeded in injection during SuperKEKB Phase-1 commissioning for 11 days
Thermionic gun◆ Employs Yb-doped-fiber and Nd/Yb:YAGlaser, Ir5Ce or Ir2Ce cathode, QTWSC orcutdisk structures◆ 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 Progress

July.2017.

5

Photo-cathode RF gun: Laser◆Yb:Fiber + Nd:YAG multi-pass amplifier
Fiber
Amp

Nd.YAG Φ4mm
×8pass~30 μJ

Nd.YAG Φ2mm
×2passE.O.

Pockels Cell

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 Progress

July.2017.

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

After the wall and3T/32 pre-injector
removal, linac tunnel
is united as one.

July.2017.

7

8

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

returnyoke❖ cooling down of residual-radiation since May 15❖ removal of FC base part from e+ station in June
❖ visual search for damaged part
❖ detailed inspection in August❖ recovery trial◆ Re-installation or replacement to spare FC
in August for 2017 autumn run & Phase-2 run.
(During these period, operation current will
be around half of the spec.)◆ Manufacturing of next FC assembly on-goingfor stand-alone test and investigation of thebreakdown issue for Phase-3 operation.
Injector Linac Progress

July.2017.

9

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

Pulse magnets (Q+ST+ST+Q)◆ AT/A1 pre-injector merger line bends are replaced fromDC to pulse magnets.
◆ Pulse magnets installation completed.
◆ Pulse power supply setting-up on-going.
◆ Test operation of pulse magnet system in September.
◆ Beam commissioning with pulse magnet system start in
October 2017.
Injector Linac Progress

Pulse current driverJuly.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 cPCI-EVR300 (Swiss FEL) was modified
for our card
• Fundamental functions canalready work well.
• Data buffer functionality is
now under implementation.
Injector Linac Progress

10July.2017. 10

Pulsed magnet rack
Edge switch

DC
Power Supplies

Pulsedmagnetdriver
PXI chassis(PXIe-1082)
ControlPC

Remote controller
DAC (PXI-6733)
ADC (PXIe-6356)
PXI-EVR-230◆ 13 racks are newly installed◆ Small form-factor (4U) power supplies aretested more than 2 months at 50Hz
Interlock signal processing(CompactRIO based system)
Injector Linac ProgressJuly.2017. 11

Development of 571.2MHz Master phase shifter• All linac clocks are generated from 571.2 MHz
master oscillator• Clock is adjusted every minutes to compensate thering circumferences, and the phase should beadjusted to meet the lengths of beam transports ofelectron and positron.
• Stabilities of 0.1%rms in amplitude and 0.02 degree
rms in phase

φ2 changed at 50 Hz
3,4,5セクター

2856MHz移相器

Injector Linac Progress

July.2017.

571.2MHz Phase shifter

571.2MHz

Injector Linac Progress

July.2017.

KL_DS, KL_DN , KL_32 Installation

ECSBCS

Voltage required [MV]

41

21.5

# 2m accelerator
structure21

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 Progress

KL_DS/BCS

KL_DN/ECS

KL_32
July.2017.

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

ARCe+ BT (3.5GeV, 0.6nC)

Primary e– (3.5GeV, 10nC)
e+ Target

Kaji et al◆ 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 selected❖ 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>100nse− GunARC
Primary e– (3.5GeV, 10nC)e+ DR (1.1 GeV, 4nC)

>100ns
96ns

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

e+ Target❖ Can be a big challenge in LLRF precision
Injector Linac Progress

July.2017. 15

Linac Upgrade Overview

Many other Linac Upgrade Progress◆ High-power microwave modulator upgrades◆ Low-level RF controls/monitor upgrades❖ Pulse-to-pulse modulation (PPM) between 4+1 rings❖ More spaces for increasing number of devices◆ Beam instrumentation❖ Large/small aperture beam position monitors (BPM)❖ Precise/fast and synchronized BPM readout system❖ Wire scanners and beam loss monitors❖ Streak cameras❖ (Deflectors, etc.)◆ Alignment to preserve beam emittance❖ Measurement precision reaching 0.1 ~ 0.3mm❖ Mover and orbit control development◆ Event-based control and timing upgrade❖ Essential for pulse-to-pulse modulation❖ Precise timing & synchronized controls❖ Bucket selection at DR and MR

Pulse magnet tests

SINAP event modules

Injector Linac Progress

Beam wire scannerJuly.2017. 16

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

LowEmittanceBeams

4+1 Ring
Injections

DRCommiss.

1 nC
Phase1

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

Injector Linac Progressnon 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 gune- commiss.
at A→5 Qe- = 1~5nCJuly.2017. 17

SummarySummary◆ We learned a lot during KEKB operation◆ Phase-2 injection into SuperKEKB is another challenge with higher
beam current and lower transverse and longitudinal emittance◆ Steady progress towards designed injection beam in steps❖ Alignment: almost confident on the measurement precision (0.1-mm local, 0.3-mm
global), may need mover to maintain it for longer term
❖ Positron generator: need discharge analysis❖ Thermionic gun: stably operated for primary electron for positron generation❖ RF gun: following recommendations at review meetings❖ Pulsed devices: global and synchronized operation❖ New modulators for energy and bunch compressors on DR beamlines◆ Will balance between final beam quality and progressive operation◆ Will select optimized route depending on available resources❖ Balance with injection operation for light sources, commissioing and developmentin parallel
Injector Linac Progress

July.2017. 18

Injection Energy Margin Recovery(even while dropping Energy 8 GeV → 7 GeV)
◆ No backup/stand-by before J-Arc in KEKB operation◆ Optimized for SuperKEKB ring injection reliability with larger beam
currents and smaller emittance◆ Temporary removal of units for construction

Kamitani et al❖ Should be recovered before phase-3◆ A unit was removed to make a room for DR BT◆ Positron deceleration capturing◆ Lower acceleration in large aperture structures in the positron capture
section◆ An unit before J-Arc was converted into a stand-by for availability◆ C-band structures were converted into S-band to help emittancepreservation◆ Degraded accelerating structures after 35 years of operation❖ Should be refurbished in the long run◆ Larger beam current with larger beam loading
Injector Linac Progress

July.2017. 19