Injector
Masanori Satoh (Acc. Lab. Div. V, KEK)
on behalf of Injector Linac Group and Linac Commissioning Group

Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

1

Contents• Injector outline• e- beam status and issue• e+ beam status and issue• Recent progress• Upgrade work during LS1• Summary

Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 20222

Outline

Injector Linac Layout

・Two electron sources:
RF gun: HER injection
Thermionic DC gun: LER, PF, PF-AR
・Sector 3-5:
All magnets are pulsed magnets.
1.1 GeV e+
Damping Ring
Continuous orbit feedback
・DC magnet settings are same for different
beam mode

60 klystron units
240 accelerating structures (S-band 2-m-long)

8 Sectors (A-C,1-5)
Energy Knob

Thermionic gun
PhotocathodeRF gunJ-ARC
1.5 GeV

B

A

BCS

ECS

C

1

2

3

e+
e+ capture section
target

4

5

PF
ECS

PF-AR

LER

chicaneEnergy KnobHER
HER 7GeV
PF-AR 6.5 or 5 GeV

Acceleration
4.2 GeV

ee+ target

LER 4 GeV e+Stand-byDeceleration

1.1 GeVe+

PF 2.5 GeV

Acceleration

1.5 GeVC
Masanori Satoh (KEK)

1

2

3

4

5
3

Beam energy variation
forAccelerator
each beammode alongthebeam line after J-ARC
KEKB
Review Committee,
Dec. 13-14,2022

3Simultaneous top up injection to 4 rings + DR (May 2018-)
Outline- stored current and linac beam orbit Stored current (1 day)

Linac/BT beam orbit
HER

LER

x
(mm)
y
(mm)

I (nC)PF-AR

Masanori Satoh (KEK)

since May 2018

KEKB Accelerator Review Committee, Dec. 13-14, 2022

PF

4

Parameters
Stage

KEKB
(achievement)

SuperKEKB
Phase-I(achievement)

OutlinePhase-II(achievement)

Phase-III
Summer’19(achievement)

Phase-III
Summer’20(achievement)

Phase-III
Summer’21(achievement)

Phase-III
Summer’22(achievement)

Phase-III(final)

Beam

e+

e–

e+

e–

e+

e–

e+

e–

e+

e–

e+

e–

e+

e-

e+

e–

Energy (GeV)

3.5

8.0

4.0

7.0

4.0

7.0

4.0

7.0

4.0

7.0

4.0

7.0

4.0

7.0

4.0

7.0

Stored current
(A)

1.6

1.1

1.0

1.0

1.0

1.0

0.83

0.94

0.712

0.607

0.790

0.687

1.460

1.145

3.6

2.6

Life time (min.)

150

200

100

100

50

100

20
(typ.)

70(typ.)

12

21

9

22

6.7

26

6

6

primary e10
Bunch charge(nC)

primary e10

primary e- 8
1

1.6

3.6

1.35

3.5

1.6

3

2.5

1

1

→ 0.4

1400

31
0

1000

13
0

200/5
(Hor./Ver.)

200/40

120/6

54/67

100/2

41/45

100/6

Energy spread

0.13%

0.13%

n/a

n/a

n/a

n/a

n/a

n/a

n/a

n/a

Bunch/Pulse

2

2

2

2

2

2

1

1

1

1

Norm.
Emittance

primary
e- 10

2

4

2.1
→ 3.5

→4

100/80

120/5
(BT1)

20/20
100/15
(BT1)

n/a

n/a

-

-

0.16%

0.07%

2

1

2

1

2

2

40/20

(gbe) (mmrad)

Repetition rate
(Hz)

50

25

25

Simultaneous
top-upinjection

3 rings(LER, HER,PF)

No top-up

Partially

50(LER+PF+PF-AR< 25 Hz)50(LER+PF+PFAR < 25 Hz)

50 Hz

50 Hz

50 Hz

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

KEKB Accelerator Review Committee, Dec. 13-14, 20225

e- beam status and issue

KEKB Accelerator Review Committee, Dec. 13-14, 2022

6

Low emittance photocathode rf e- gunRF e- gunIr7Ce2 cathodee- beam status

Laser system• Photocathode: Ir7Ce2• Cavity: QTWSC (Quasi Travelling Wave Side Coupler)– Strong focusing electric fieldshort drift space
Secondary RF gun
for test and backup

M. Yoshida et al.

KEKB Accelerator Review Committee, Dec. 13-14, 20227

e- beam status

Hybrid laser system for rf e- gun•

Yb doped fiber and Nd:YAG DPSS module Amplifier••••

Output Power in 1st line:ω (1064 nm): 32 mJ
2ω ( 532 nm): 12 mJ
4ω ( 266 nm): 1.3 mJ

1st laser
2nd laser

Laser roomon theground virtualKLY Gallery

cathodediagnosticsLaser line to RFGun
TunnelRF-GunR. Zhang,
X. Zhou et al.

Optics layout
the Review
tunnel
KEKBinCommittee, Dec. 13-14, 2022
8Accelerator

Laser transport line

8

DOE for reshaping of laser spatial distribution
2019.06 without DOE & beam position sensor

H 2σ: 48.04±0.51, V 2σ: 46.08±0.69

Pointing stability
can be improved.

e- beam status

2021.06 with DOE & beam position sensor

H 2σ: 24.30±3.06, V 2σ: 10.08±0.46

DOE (diffractive optical element) were installedat 1st /2nd (in summer ‘20/‘21) line laser: Laser beamhomogenizer for low emittance beam with thehigh intensity bunch charge.

DOE is installed in vacuum
chamber filled with Argon gas.

Masanori Satoh (KEK)world first DOE application in UV laser

KEKB Accelerator Review Committee, Dec. 13-14, 2022

R. Zhang 9

e- beam statuse- bunch charge history (2020a to 2022c)(from rf gun)(BT)

2020a,b2020c

2021a,b2021c

2022a,b

2022c
(LS1)

High bunchcharge study
discharge

KEKB Accelerator Review Committee, Dec. 13-14, 2022

Bunch charge
feedback

10

Issue of rf gun laser window degradatione- beam issue• Long term operation makes rf gun laser windows dirty for both of 1st and 2nd line.
• It decrease the transmittance of laser power through window and bunch charge intensity.
• After replacement of the laser window, the bunch charge intensity is recovered.
• Vacuum ion pump was installed between the laser window and rf gun cavity with theextension vacuum duct for the 1st line laser in this summer maintenance ‘22.

Bunch charge (nC)e- intensity by 1st-line laser

new window
degraded window

1st-line laser incident position [mm]M. Yoshidae- intensity by 2nd-line laser

new window
degraded window

2nd-line laser incident position [mm]KEKB Accelerator Review Committee, Dec. 13-14, 202211

Improvement of laser window degradation with ion pump

e- beam issue• Long term operation for keeping e- bunch charge is very important issue.
• Continuous beam test at e- beam repetition of 22 Hz has been conducted more than 5 days.
• Installed ion pump could help to mitigate the laser window degradation from the experimental
results.
• This test will be continued until the end of this run. Further improvement is also being
considered.
Degradation test of 1st/2nd line laser window

Quantum efficiency

1st laser line (adding ion pump)
2nd laser line

5 daysMasanori Satoh (KEK)

ElapsedtimeReview
HH:MM:SS
KEKB Accelerator
Committee, Dec. 13-14, 2022

M. Yoshida

12Injection efficiency of 2nd bunch

e- beam issue• HER injection efficiency of e- 2nd bunch is lower than that of 1st bunch and varies gradually.
• In some cases, there is not clear correlation between injection efficiency and orbit of 2nd bunch.
• Low injection efficiency could be also caused by the emittance deterioration.
• Fast kicker for 2nd bunch orbit correction could be effective. Two fast kickers will be installed at the linac end andthe beginning of BT in summer ’23.

Vertical beam position at BT• Prototype kicker was installed at the entrance of J-ARC in this summer ’22. Beam test will be conducted soon.

Ver. position of 2nd bunch at the BT end

Injection efficiency
difference

N. IidaVer. position of 1st bunch at the BT end

Difference between 2nd and 1st bunch
Injection efficiency(Lower 2nd bunch efficiency means negative value)
KEKB Accelerator Review Committee, Dec. 13-14, 202213

e- beam summary and issue

e- beam issue• Thermionic DC e- gun has worked fine.

• Photocathode rf e- gun• Laser system and DOE element has worked fine without any significant trouble.

• Increase of bunch charge• High bunch charge e- was demonstrated. Achieved 5 nC from e- gun and 4 nC at the linac end.
• However, the beam loss at J-ARC and e+ target location should be minimized. Beam orbit stability should bealso improved.
• Further beam study will be continued during LS1.

• Issue• Gradual decrease of bunch charge due to laser window deterioration. It could be solved by adding theextension vacuum chamber and ion pump.
• Emittance at the linac end and BT1 (before Arc1) is almost satisfied the final goal while bunch charge (2 nC)
is less than final goal (4 nC).
• However, emittance at BT2 is increased due to ISR, CSR, and some other reasons.
• Increase of 2nd bunch injection efficiency and improvement of its stability are important issues.
e- emittance

Measured enx,nxy (2 nC) : 20/20 mm (at BT1)
Goal: enx,nxy (4 nC) : 40/20 (H/V) mｍ

KEKB Accelerator Review Committee, Dec. 13-14, 2022

14

e+ beam status and issue

KEKB Accelerator Review Committee, Dec. 13-14, 2022

15

e+ beam status

Positron source setup at Sector1
Positron target and capture section

DC solenoid
Large aperture S-band acc. Structures (x10)

W target + flux concentrator (FC)KEKB Accelerator Review Committee, Dec. 13-14, 2022

Y. Enomoto et al.

16

e+ beam status

Positron Capture Section: Flux concentrator, bridge coil, solenoid
Large Aperture S-band acc. structure (LAS)
Bridge Coil (BC)Solenoid

Tungsten target

3.5 GeV e- beam

Flux Concentrator (FC)Cu-alloy (NC50: Cu-Si-Ni)
IFC= 12 kA
Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

Y. Enomoto et al.

17

e+ bunch charge history (2020a to 2022c)
2020c

2020a,b2021a,be+ beam status(after e+ target)(before DR) ・Solenoid current (SL_16_)optimization(Linac end) ・beam tuning (primary e- bunch charge ↑)
(BT)
2022c

2021c

2022a,b(LS1)・beam tuning

・Steering, BPM
in Unit 1-5, 1-6
・beam tuning
・New FC
・Solenoid
current↑

・decrease bunch charge(MR request)

18

KEKB Accelerator Review Committee, Dec. 13-14, 202218

e+ beam summary and issue

e+ beam issue• e+ bunch charge is almost achieved (final target: 4 nC)••••

6 nC at BPM “SP_16_5” (1st BPM after e+ target)
4 nC at LTR (Linac To damping Ring)
3.5 nC at linac end and BTe+ production efficiency with the current FC is reached the simulation result (60%).

• Further improvement of positron bunch charge• Increase acc. gradient of first two structures (AC_15_1[2]) at e+ capture section• Increase primary e- bunch charge, beam tuning, FC power supply upgrade, and so on• Issue• Emittance at linac end and BT1 (before Arc1) is almost satisfied the final goal.
• However, emittance at BT2 is increased due to ISR, CSR, and some other reasons.
• Horizontal emittance after DR is larger than design value. Low emittance DR optics will be tested after LS1.

e+ emittance

Measured enx,nxy (3 nC) : 103.5/4.7 mm (at BT1)
Goal: enx,nxy (4 nC) : 100/15 (H/V) mｍ

Y. Enomoto
KEKB Accelerator Review Committee, Dec. 13-14, 2022

19

Recent progress

KEKB Accelerator Review Committee, Dec. 13-14, 2022

20

Recent progress• SR monitor at J-ARC• Emittance control bump
• Autonomous beam tuning• BPM with 8 strip-line electrodes to measure energy spread (appendix)• Postmortem analysis of beam abort event (appendix)

Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

21

SR monitor at J-ARC

Recent progress• SR monitors (SRM) were installed at J-ARC and ECS in the beginning stage of KEKB operation. After then, they
became obsolete. SRM at ECS was removed after reconfiguration of ECS magnet.
• SRM at J-ARC is recently used as a non-destructive profile monitor with the reconstructed optical system.
• Similar system at BT has been also available since this November.

R. Zhang et al.
J-ARC layout

SR extraction
port
Masanori
Satoh (KEK)

Control GUI

SR 13-14,
monitor(J-ARC)KEKB Accelerator Review Committee, Dec.
2022

SR monitor (BT)22

SR monitor at J-ARC (cont’d)Recent progress• Centroid position of the beam profile images are synchronously measured by SR monitor and screen monitor(SCM) with the different beam energy. Each of them and BPM show a good agreement.
• Measured profile images are slightly different between SCM and SRM.
• SRM could be a strong help for beam feedback as a nondestructive monitor.
Beam profile Imageby changing klystron phase

SCM

SRM

Projection plot

SCM

SRM

Centroid position (SRM, SCM)
vs beam energy

J-ARC layout

Masanori Satoh (KEK)

Right/Left definition is opposite
KEKB Accelerator Review Committee,
Dec.
13-14,
2022
btwn
SCM
and
SRM

F. Miyahara, Y. Seimiya 23

Low
emittance
ewith
bump
orbit
• Measured emittance and beam size at Sector5 and BT by changing vertical orbit (Sector3-5)

Recent progress• Finding the beam orbit minimizing emittance (mitigate emittance growth due to transverse wake field effect)• Correlation btwn the emittance and beam size is confirmed with the measured data at Sector5 and BT.

KEKB Accelerator Review Committee, Dec. 13-14, 2022

Ver. norm. emittance
Bmag x ver. norm. emittanceVer. norm. emittance
Bmag x ver. norm. emittanceVer. bump height

Y. Seimiya

Ver. beam size sy (mm)Masanori Satoh (KEK)at BT

at Sector5

Ver. beam size sy (mm)Different ver. bump height @ Sector3-5• It could find and keep the orbit minimizing emittance with SRM at BT even during beam injection.

Ver. bump height24

Automatic beam tuning

Recent progress• Automatic beam tuning approach with machine learning is recent trend in accelerator operation.
• Bayesian Optimization approach is now under test by using the beam of injector Linac.
• Implementation using GPyOpt Python library (T. Natsui) / In-house developed implementation (G. Mitsuka)

Preliminary test result with GPyOpt• Setup:T. Natsui• Explanatory variable: excitation current of 4 pulsed steering magnets at J-ARC exit
• Objective function: bunch charge calculated from 4 BPMs at around the e+ target• Bunch charge before LTR was increased from 3.5 nC to 3.7 nC after optimization.
• Best parameter was found within ～ 5 min. (depending on beam rep. , # of number of averaging points, and so on)• Optimization result seems to be same level by the operator.

• In the future, try to apply it to more complicated tuning like 2nd bunch beam tuning, dispersion correction,
injection tuning (after LS1).
Steering
current(normalized)

4 pulsed steeringx(mm)

I (nC)

e+ target

Before optimization

After
optimization
KEKB Accelerator
ReviewCommittee, Dec. 13-14, 2022

Objective valuey(mm)# of trial

Upgrade work during LS1

KEKB Accelerator Review Committee, Dec. 13-14, 2022

26

Upgrade during LS1

Upgrade work during LS1• Pulsed Quads• at J-ARC matching section• at Sector1, 2 (e-/e+ compatible optics region)• New accelerating structure

Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

27

Pulsed Quads at J-ARC for optics matchingUpgrade during LS1

e- beam• At the entrance and exit of 180 deg. J-ARC region,a good optics matching is very important to mitigate beamloss and emittance growth.
• Simultaneous matching for both of HER/LER injection
beam requires the pulsed quads.

matching
section• From the simulation result, 4 pulsed quads at both ofentrance and exit of J-ARC are sufficient.

matching
sectionY. Okayasu

e- beam

Bmag yCurrent optics at J-ARC

New optics at J-ARC
with pulsed quads

Bmag xMatching simulation

KEKB Accelerator Review Committee, Dec. 13-14, 2022

e- beamY. Seimiya 28

Pulsed Quads at J-ARC for e- low beta optics

Upgrade during LS1• Current optics at Sector1, 2• Large emittance e+ beam is accelerated from 0.1 GeV to 1.1 GeV for DR injection.
• Quad settings is optimized for e+ beam.
• For e- beam (3 ～ 4 GeV), focusing force is weak in comparison with optimum parameter. It could cause theemittance growth.

Four DC quads will be replaced by pulsed one.

KEKB Accelerator Review Committee, Dec. 13-14, 2022

29

Pulsed Quads at J-ARC for e- low beta optics (cont’d)Upgrade during LS1• After only these four pulsed quads are optimized for the e- beam, the betatronfunction can be decreased.
• Simulation result shows that it can help to decrease the emittance less than half.
Δγε𝑥 ~ 100 um, 𝛽𝑥 = 45.2 m••Δγε𝑥 ~ 40 um, 𝛽𝑥 = 16.3 m

End of LAS cavity
Start of S-band
cavityBunch tail is kicked back byquad, and temporally
emittance is reduced.

e+ target

Sector2 end

achieved smaller
betatron function

e+ target

Sector2 end

Before optimization
optimization
KEKB Accelerator Review Committee, Dec.After
13-14, 2022

Y. Seimiya 30

New accelerating structure

Upgrade during LS1• Mitigation of accelerating structure failures• Originally designed for 8 MeV/m (PF injector), but used at 20 MeV/m (KEKB upgrade)• Degradation that lead to high field emission rate and discharges• Water leaks, field emission , discharge in waveguide, and so on (29 of 60 units have some problems)• Not only future Y(6S) but even Y(4S) could be suffered

Damaged iris

• 5-year upgrade plan to fabricate and install new accelerator structures (FY2018 –FY2022)• 4 units (16 acc. structures) will be replaced by new one. (Unit44 was replaced in this summer)• New acc. structure: acc. gain ↑7%, surface field ↓20% (reduce breakdown)• New pulse compressor (SCPC) was also developed and installed in Unit44.

Colling water leakage

New pulse compressor

New S-band 2-m-long TW acc. structure KEKB Accelerator Review
Committee,
Dec.
13-14, 2022
Spherical-Cavity
Pulse
Compressor(SCPC)

H. Ego31

Summary•

Simultaneous top up injection operation of 4 storage rings (SuperKEKB HER/LER, PF, PF-AR) + DR has beensuccessfully conducted.

•

e- beam• Laser system has worked fine without any significant trouble.
• DOE was installed also at 2nd laser line in the last summer maintenance, and it has worked fine.
• In the run 2022a/b, bunch charge of 2 nC can be kept with bunch charge feedback.
• 5 nC from gun was demonstrated. Further beam study will be continued during LS1.

•e+ beam• The new FC is working fine.
• Reached bunch charge of 3.5 nC at BT end (final design 4 nC).

•

Upgrade work during LS1• Pulsed Quads (x8) at J-ARC for the simultaneous dedicated matching of HER/LER injection beam
• Pulsed Quads (x4) at Sector1, 2 for low beta optics of HER injection beam
• New accelerating structure• Replacement of air conditioners at SectorA, B (in the accelerator tunnel)• Fast kicker for 2nd bunch orbit correction•

Issues• Emittance growth at end of BT for both of e- and e+ beam (BT report, Injection report)• Low e- injection efficiency of 2nd bunch• Increase the e- bunch charge while keeping small emittance
Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

32

Appendix

Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

33

Outline• Injector linac provides e+ beam to LER via DR and e- beam to HER and twolight sources (PF, PF-AR) up to 50 Hz.
• Maximum repetition is limited up to 25 Hz during LS1 to reduce electricity consumption(run 2022c).

• Simultaneous top up injection to 4 rings has been successfully conducted since
May 2018.
• Electron sources• Photocathode rf gun for HER injection• Thermionic DC gun for LER (primary e- for e+ production) and two lightsources injection• two subharmonic bunchers (114 MHz/571 MHz) for obtaining single bunch beam

• Two bunch injection is available (96 ns interval) for both of HER and LER
injection.

Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

34

Pulse to pulse beam switching:rf e- gun/thermionic e- gun
In injector section(double decker beam line)

Thermionic DC e- gun (GU_AT)

Outlinew/ 2 subharmonic bunchers (114 MHz, 571 MHz) and 2
bunchers.

・e+ production e-: 10 nC (for LER injection)・e- study/HER injection: 1 nC
・PF injection: 0.1 - 0.3 nC
・PF-AR injection: 0.1 - 0.3 nC

RF e- gun
（GR_A1 for HER injection）

Pulsed bend
Schematic side view

KEKB Accelerator Review Committee, Dec. 13-14, 2022

35

Layout of LINAC, BT to MR
e- beam directly injects into HER:
The injeciton BG is directly affected by
the condition of RF-gun, LINAC, and BT.

e+ beam injects into LER via DR:
The injection BG is not affected verymuch by the condition upstream the DR.

Injection Points
LINAC
1.1GeV Damping Ring (DR)for positron

Beam Transport line (BT)Arc4primary e- for e+: Therminic Gun

Jarce- : RF Gun
SectorB SectorA
SectorC

Sector1

LTR

BCS
Sector2

ECS

BT1

Sector3

Sector4

BT2

ECS
for e+

Arc2-3

Sector5e+ target

Green: Emittance measured with wire scanners(WSs)
Arc0
BCS: Bunch Compression System
ECS: Energy Compression System KEKB Accelerator Review Committee, Dec. 13-14, 2022

BT1

Arc1

N. Iida36

e- beam

KEKB Accelerator Review Committee, Dec. 13-14, 202237

e- beam source for LER/light source• Thermionic DC e- gun• Thermionic DC e- gun provides e- beam with bunch charge of around 10 nC for positron
production (LER injection) and of around 0.3 nC for light sources.
• Two subharmonic bunchers (114 MHz, 571 MHz), pre-buncher, and buncher can generate thesingle bunched e- beam with the bunch length of about 5 ps (0.3 nC)/10 ps (10 nC) in FWHM.
• It has worked through run 2021b to 2022c without any significant troubles.

Grid pulse width～ 2 nsThermionic DC e- gun and bunching section
Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

Y. Ogawa, OHO200238

e- beam source for HER• Photocathode rf e- gun• HER injection has been conducted by using only rf gun since 2019.
• Electron beam from rf gun is directly delivered to HER ring without DR. The system comprises ofquasi travelling wave (QTW) type cavity, Ir7Ce2 photocathode, and laser system. Two laser system
is in operation (1st laser line and 2nd laser line). 1st laser line is utilized for daily operation, and 2ndline is backup and also cathode laser cleaning system for recovering the quantum efficiency ofphotocathode. Both laser lines can be simultaneously operated for obtaining higher bunch charged
e- beam.
• Diffractive optical element (DOE) has been installed in 1st laser line after run 2020b for reshaping
the transverse laser profile (flat-top distribution). After run 2020c, it can help obtaining the low
emittance beam w/ high bunch charge by mitigating space charge effect and decreasing beam jitter.

Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

39

Countermeasure of window degradation at 1st laser line

e- beam issue• Install extension vacuum duct between the laser window and the rf gun cavity at 1st laser linein this summer shutdown 2022.
• Ion pump was added between the laser window and rf gun cavity.
• Its effectiveness is now under test.

ebeam

quartzwindow

newquartzwindowextension
duct

added
pump

laser photon into RF-gun
vacuum chamber
X. Zhou
KEKB Accelerator Review Committee, Dec. 13-14, 2022

40

Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

T. Natsui, eeFACT202241

入射効率低下

水平軌道差と入射効率

The different between 1st and#2 bunches have no dependent
on the injection efficiencies.
It is considered that theemittance of 2nd bunch had
been increased.

垂直軌道差と入射効率
入射効率#1

入射効率#2垂直軌道差(#2-#1)

水平軌道差(#2-#1)

BT終端での水平軌道 #2

BT終端での垂直軌道 #2
BT終端での垂直軌道 #2

BT終端での水平軌道 #1

入射効率 #2-#1

BT終端での垂直軌道 #1
BT終端での垂直軌道 #1
入射効率 #2-#1

特にHERでは、この期間は２バンチ目の入射効率は垂直軌道変化に依存している。
（１バンチ目のみ、軌道FBが働いているため、２バンチ目だけがDriftしている）
この時、水平軌道はほとんど変化がない。
KEKB Accelerator２バンチ目の垂直軌道補正のために、Fast
Review Committee, Dec. 13-14, 2022
kickerを設置する。

High bunch charge e- beam test
5 nC beam from rf e- gun, 4 nC at the linac end

KEKB Accelerator Review Committee, Dec. 13-14, 2022

e+ beam

KEKB Accelerator Review Committee, Dec. 13-14, 2022

44

e+ beam• e+ production system• e+ generation and capture system is situated in the middle of Sector1. The system comprises oftungsten target inside flux concentrator (FC), bridge coil, DC solenoid, 10 large aperture S-band
accelerating structures. The tungsten target has a small hole with diameter of 2 mm. e- beam for
HER/light source injection traverses inside the hole.
• For e+ beam generation mode, primary electron beam with bunch charge of around10 nC, energy ofaround 3 GeV is impinging on the tungsten target with diameter of 4 mm.

• FC• FC made by oxygen free cupper was damaged by large discharge in Phase2. After this discharge, it isdifficult to apply the high voltage because of shortening of slit gap distance.

• To improve FC head performance, Cu-alloy (NC50: Cu-Si-Ni) was adopted as FC head material. In
addition, FC design was also optimized. A new FC (current version) was manufactured, tested andfinally installed into beam line in summer shutdown FY2020. Since run2020c, the new FC has beensuccessfully in operation without any significant problem.
• Sometimes FC operation was interrupted for a short time since the thyratron for FC has some noiseproblem. Some countermeasures were already applied (modification of cabling inside thyratron,
adjustment of reservoir voltage).
Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 202245

After large discharge…
After large discharge

Slit gap got narrow.
Not possible toapply high voltage
unless the gap will
be expanded.
Y. Enomoto
SuperKEKB review, 2019KEKB Accelerator Review Committee, Dec. 13-14, 2022

46

KEKB Accelerator Review Committee, Dec. 13-14, 2022

47

Comparison FC baseMaterial

Shape

RemarkFor e-For e+

Base 5

OFC
+
SS400

Old design

12 kA in beam line
large slit gap△○

Base 7NC50+
permendur

Old design

4.5 months test

○

○+ *

Base 8NC50+permendur

New design(optimized)
in operation

Cooling water leakage wasfound.
(already fixed and tested during
4 days)◎○+ *All FC bases achieve 12 kA in test stand. (*) return yoke (permendur) makes higher magnetic field.
Base 8

Y. Enomoto

・Optimized yoke shape・Reinforced insulation (FC head support)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

Base 7 and older

48

e+ beam status

Steering magnet and BPM in solenoid section• There is no BPM and steering magnet between e+ target and 16_5 unit.
• DC steering (x4) and BPM (x4) will be installed in this summer shutdown.
• It could be help to cure e+ beam loss and e- beam emittance growth.

SY, BPMSX, BPMSX, BPM49
KEKBNoAccelerator
Dec.magnet
13-14, 2022
BPMReview
andCommittee,
steering

Target: e+ W target
FC_15: flux concentrator
SC: screen monitor
AC: accelerating structure
SP: BPM
SL: solenoid
BM: bend
PX: horizontal pulsed steering
PY: vertical pulsed steering

49

Recent progress

KEKB Accelerator Review Committee, Dec. 13-14, 2022

50

BPM (with 8 stripline electrodes) at J-ARC

Recent progress• Special BPM (S8) at J-ARC can obtain the quadrupole moment (Jq) of beam. It help to measure the energy spread.
• Results measured with S8 (nondestructive) and SCM (destructive) are comparable.

y position (S8) (arb. units)

Jq (S8)x beam size (SCM) (pixel)

x position (S8) (arb. units)

SCM
SC_R0_31

Klystron phase SectorB (deg.)

Masanori Satoh (KEK)

J-ARC layout

Changing klystron phasey position (SCM) (mm)

BPM (w/ 8 electrodes)
S8_R0_31

x position (SCM) (mm)• Both of S8 and SRM can work complementary as nondestructive monitor for beam tuning and feedback.

KEKB Accelerator Review Committee, Dec. 13-14, 2022

Klystron phase SectorB (deg.)

F. Miyahara

51

Postmortem analysis
of beam abort event

Masanori Satoh (KEK)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

52

Postmortem analysis of beam abort event

Recent progress

Abort event

Beam abort coincidence w/ injection:
Linac/BT orbit, RF monitor, pulsed magnet
PS are abnormal or normal?
It can be easily checked via web pageautomatically created.
KEKB Accelerator Review Committee, Dec. 13-14, 2022

53

RF pulse shortening event can be checked(injector operation e-log)

KEKB Accelerator Review Committee, Dec. 13-14, 2022

Recent progress

54

Other subsystems

KEKB Accelerator Review Committee, Dec. 13-14, 2022

55

Subsystem

RF phase feedback

RF phase feedback can quicky
recover the beam operation mode
from maintenance mode.

Variation of rf phase and cooling water temperature(accelerating structure)

T. Miura

KEKB Accelerator Review Committee, Dec. 13-14, 2022

RF phase feedback:already deployed to many locations

56

Subsystem

Pulsed magnet

Pulsed magnet
BPM

Mounted on movable girder(remote controllable, 10 mm step)High stability of PS output

Schematic diagram ofcontrol system

DesignMeasured

Quad

0.1%

< ~0.006%

Steering

0.01%< ~0.003%

Future plan••
Y. Enomoto

Fast steering magnet is under development (kick only the 1st bunch or
only the 2nd bunch for reducing the orbit difference between 1st and 2nd
bunch).
This work is in progress as collaboration between PF and injector linac.

KEKB Accelerator Review Committee, Dec. 13-14, 2022

57

Pulsed steering magnet PS upgrade～ run 2021b

New (FY’21 summer)

Voltage

±50 V

±100V

Current

±10 A

±20 A

Voltage drop in PS

20 V*

1 V**

Output voltage

±20 V

±90 V

Inductance

3 mH

12 mH (7.5 mH for PX_A4_4)

Amp

PA12

PA04

# of production

35 (70 ch)

19 (38 ch) + 2ch

Installation location

SectorA
PX/PY_AT_22, PX/PY_A1_M
PX/PY_A2_1,
Sector1, 2
PX/PY_16_5, PX/PY_17_2
PX/PY_18_2, PX/PY_21_2
PX/PY_22_4,
SectorD, 1-5
PX/PY_DC_2 ～ PX/PY_58_4 (26 ch)

SectorA
PX/PY_A4_4
PX/PY_C7_4,
SectorJ-ARC
PX/PY_R0_01, PX/PY_R0_02,
PX/PY_R0_61, PX/PY_R0_63
Sector1, 2
PY_12_2, PX_13_2, PX/PY_13_5,
PX/PY_13_52,
PX/PY_17_4, PX/PY_18_4,
PX/PY_21_4, PX/PY_24_4
PX_23_4, PY_24_1, PX_26_1,
PY_26_4, PX_27_2, PY_28_2
Total: 32 ch

Black：in operation
Red：new
Blue：replacement

Total: 42 ch

Y. Enomoto

KEKB Accelerator Review Committee, Dec. 13-14, 2022

Subsystem(5A x4)58

Subsystem

Data archiving
・Archiver appliance
Linac archiver: ~ 110,000 data
In addition CSS archiver,2019/11～ Archiver Appliance in operation• Data retrieving speed performance x800
• Easy management• Load balance with clustering technology
・Synchronized measurement (BPM, RF, pulsed magnet)

Data retrieving speed performance between
CSS archiver and archiver applianceAll data are stored（ASCII → gzip）• Postmortem analysis of event
related to MR abort
Abnormalorbit• Abnormal beam orbit• Abnormal rf phase/amplitude• Abnormal pulsed magnet
current
Beam orbit display• Binarization of data
(HER/LER Abort event)with HDF5 format in progress
F. Miyahara
KEKB Accelerator Review Committee, Dec. 13-14, 2022

I. Satake
Issue
Archiving data:・mutual easy access and usage oflinac/ring data

Synchronization of linac and ring data:
・Development of easy analysis tool・Automation of data processing
59