Injector Commissioning

Injector Commissioning(Phase I & II)
Masanori Satoh(Accelerator Laboratory, KEK)
for Linac Commissioning GroupThe 21th KEKB Accelerator Review Committee, June 13-15, 2016

Injector Commissioning

Contents
1. Injector overview
2. Requirements for SKEKB injector– Operation scheme– Low emittance preservation– Simultaneous top-up injection

3. Recent results of injector commissioning
4. Summary and plan2

Injector Commissioning• Injector linac

Injector overview– Provide e-/e+ for 4 independent storage rings– 600-m-long, 25 Hz (Max. rep. 50 Hz)– Two bunch operation (96 ns interval)• SuperKEKB– HER: 7 GeV, 1 nC
– LER: 4 GeV, 1 nC
Damping ring: 1.1 GeV• Two light sources:– PF:e-, 2.5 GeV, 0.3 nC

three times daily injection or top-up– PF-AR: e-, 3 GeV, 0.3 nC
three times daily injection
3

Injector Commissioning

Requirements for SKEKB injector• Low emittance e-/e+ beam:– e-: 1 nC, 300 mm⋅mrad (KEKB) => 5 nC, 50 (H)/20 (V) mm⋅mrad (Phase III)
– e+: 1 nC, 1500 mm⋅mrad (KEKB) => 4 nC, 100 (H)/20 (V) mm⋅mrad (Phase III)– (*) 1 nC (w/o low emittance) for Phase I, 2 nC (w/ low emittance) for Phase II– Low emittance photocathode rf gun. DR for e+. Fine component alignment(0.1 mm – 0.3 mm (σ)). Precise beam orbit measurement and control for
low emittance preservation.

• High intensity e+:– Flux concentrator, Large aperture S-band accelerating structure• Event based timing system (bucket selection for DR/MR)• Fast rf monitor, high precision BPM readout, pulsed quads and steering
magnets.
• Simultaneous top-up injection (short beam life time (～ 6 min.))– SKEKB HER/LER (+ damping ring), PF, and PF-AR
4

Injector Commissioning

Operation scheme
10 nC x 2 bunches x 50 Hz (SuperKEKB e+)
5 (1) nC x 2 bunches x 50 Hz (SuperKEKB e-)
5 nC (0.3) x 1 bunch x 5 (25) Hz (PF-AR)
0.3 nC x 1 bunch x 25 Hz (PF)A

B

l e-/e+ beams are delivered to 4-rings
PulsedQuad (Doublet)with different
bunch charge forand pulseenergy.
l Beam accelera7on modes must be switchedby-pulse
switchingby 50 Hz pulse-by-pulse for top-up
injec7on.

emittance
Compatible settingslow
fore-/e+ beams
1.1 GeV
RF gun1.5 GeV e(DC Quads)
DR
C
1
2
3

Decelerate LER: 4 GeV e+

ee+ targetC

HER: 7 GeV e5 nC x2
PF-AR: 6.5 GeV e5 nC x1

4.219 GeV

same energy

15e-:Chicane

e+ target

1.5 GeV

44 nC x2
PF: 2.5 GeV e-

1.1 GeVe+

0.3 nC x1
2

3

4

5

Injector Commissioning••••

Low emittance preservation

Low emittance e- beam transport w/o damping ring
Emittance preservation w/ precise beam orbit control is key issue for e- beam.
Simulation results show the feasibility of emittance preservation w/ bunch
compression and offset injection. Beam study was also conducted.
Beam study was also conducted at Sector A and B (125 m straight section)•••- Simulation Quads and acc. w/
misalignment of 0.3 mm (σ)
50 different error seeds
All seeds can be corrected.

••- Experiment Control steering at Sector A
Emittance was changed at Sector B

Injector Commissioning

Simultaneous top-up injection for three rings
PF-AR
injection(twicedaily)in
KEKB
Stored beam
beam
current
stability
ininterrupt
Apr. 2010.
••• Stored
current
stability
2000.
- KEKB:
KEKB: 300
1 mA(~(~
0.05%)-injection.
mA50%) : e-: 12.5 Hz, e+: 25 Hz• -Bigfor(~(~
SuperKEKB- PF:
PF:issue
0.05mAmA
0.01%) : operation.
0.5 Hz240
53%)• Beam lifetime ~ 6 min.
PFKEKB eKEKB e+

Luminosity
7Injector Commissioning

Simultaneous top-up including PF-AR injection
•
•
•
•
•

PF-AR and KEKB share the long part of BT line.
Existing tunnel space is very tight.
New tunnel has been constructed in Mar. 2014.
Pulsed bend will be installed at #3 switch yard of linac.
New BT commissioning will be conducted in Feb. 2017.

H. Takaki (KEKB review 2013)

Injector Commissioning
•

•
•
•

Injector commissioning for Phase I

Thermionic e- gun was reinstalled in end of April 2015.
– e+ primary e- generation (10 nC). (rf gun achieved the maximum bunch chargeof 5.6 nC)– Keep the beam line for rf gun in original position.
– Beam line level of thermionic gun was changed from 1200 mm to 1950 mm.
– Spare magnets have been reused for the thermionic gun beam line.
Thermionic e- gun commissioning has been successful in May 2015.
MR (both of HER and LER) injection by thermionic e- gun started in this February.
June 8th ~:– HER injection: rf e- gun, LER injection: thermionic e- gunInjector Commissioning

Thermionic e- gun (HER injection)• Typical operation:– 1 nC (gun), 1 nC (linac end), 0.5 nC (BT end)
– 12.5 Hz, single bunch

x (mm)y (mm)First bunch~ 8 ps(streak camera measurement)
I (nC)

Linac

BT
10

Injector Commissioning

Thermionic
egun
(LER
injection)• Typical operation:– Primary e-: 10 nC (gun), 7 nC (target)– e+: 0.7 nC (linac end), 0.4 nC (BT end)
– 25 Hz, two bunch

First bunch~ 15 ps(streak camera measurement)

x (mm)y (mm)

Second bunch~ 15 ps

I (nC)(streak camera measurement)

Linac

BT
11

Injector Commissioning

Thermionic e- gun (Injection rate)• LER:– Injection rate: ~ 0.5 mA/s, efficiency: 70% ~ 100%

• HER:– Injection rate: ~ 0.8 mA/s, efficiency: 80% ~ 100%

Injection rate (mA/s)

2.0

LER injection rate (mA/s)
HER injection rate (mA/s)

1.5

Two bunch injection

1.0

0.5

0.0

160523 00:00 160523 12:00 160524 00:00 160524 12:00 160525 00:00
12
Date and time (yyMMdd HH:mm)

Single bunch injection

Injector Commissioning

Thermionic e- gun (emittance)• Emittance was measured by the multiple wire scanner situated at
Sector 5.

• e- beam: εnx ~ 160, εny ~ 300 (mm·mrad)• e+ beam: εnx ~ 1000, εny ~ 1200 (mm·mrad)

e- beame+ beam13

Injector Commissioning•

Commissioning tools

All parameters can be access via EPICS PVs– ~ 150 IOCs•

Parameter logging: Archiver (CA, CSS)
– 42000 PVs– CLI and Web-based data browser•••

EPICS CSS alarm
Tools based on SAD, Python, CSS
Parameter management tool•

Orbit correction and feedback software is almost ready (both of model andmeasured response can be applicable to correction).
Energy feedback EPICS IOC is almost ready for operation.
Energy spread monitor and feedback will be prepared in this autumn.
Synchronized measurement over 91 BPMs is ready. Similar tools for fast rf
monitor is also ready. Combination of them could be a strong analysis tools.

•
•
•

14

Injector Commissioning

MR injection from rf e- gun••••

MR injection w/ rf gun was success at the first time (May 31, 2016).
Bunch charge is around 1 nC w/o emittance preservation.
e- beam emittance was measured by the Quads scan (Qscan) and multiple wire
scanner (WS).
Qscan can be conducted by using a profile monitor and a GbE network attachedcamera w/ external trigger input.
Measured location

Horizontal εn (mm·mrad) Vertical εn (mm·mrad)

Unit A1 chicane (Qscan)

28.3

26.4

A1_M (Qscan)

20.3

17.7

Dump @ Sector B(Qscan)

48.5

21.7

Sector C (WS)

100 ± 13834.2 ± 16.5

Sector 5 (WS)106 ± 24.9

76.5 ± 38.9

BT (WS)

211 ± 110.6

133 ± 22.2

15

Injector Commissioning

Beam orbit
w/o bunch compression (rf e- gun)x (mm)

Horizontal steering x (A)y (mm)

Vertical steering x (A)I (nC)LinacBT

Injector Commissioning

Beam orbit
w/ bunch compression (rf e- gun)x (mm)

Horizontal steering x (A)y (mm)

Vertical steering x (A)I (nC)LinacBT

Injector Commissioning

Main ring injection w/ rf e- gun• After bunch compression w/ chicane of unit A1, the injection
efficiency reaches almost 100%.
Injection tuning
HER current (mA)
Injection efficiency (%)
Bunch charge (nC)

w/o bunchcompression

w/ bunch compression

Injector Commissioning

Stable HER injection w/ rf e- gun

24 hours
LER inj. rate
HER inj. rate

100

1.5

Injection efficiency (%)

Injection rate (mA/s)

2.0

1.0

0.5

0.0

HER injection
w/ thermionic e- gun

160606 00:00

160607 00:00

160608 00:00

HER injection
w/ rf e- gun
160609 00:00

80
60
40
20
0

160610 00:00

Da te and time (yyMMdd HH:mm)

LE R inj. eff.
HER inj. eff.

HER injection
w/ thermionic e- gun

160606 00:00

19160607 00:00

160608 00:00

HER injection
w/ rf e- gun
160609 00:00

160610 00:00

Da te and time (yyMMdd HH:mm)

Injector Commissioning

Bunch charge stability (rf e- gun)• RF e- gun has been utilized for HER injection since last Wednesday(June 8th) w/o any significant trouble.
• Bunch charge fluctuation is about 4% ~ 5%. (~ 20% in 2014)• 1% ~ 2% (thermionic e- gun)• Bunch charge stability is almost same for different beam repetition.
0.07

Bunch charge stability (∼ 10 min.)
1 Hz
5 Hz
12.5 Hz
25 Hz

0.06

0.04
0.03
0.02
0.01
0.00

SP_A
1_G
SP_A
1_
SP_A 01_
SP_A 1
1_M
SP_A
2_1
SP_A
2_3
SP_A
2_4
SP_A
3_2
SP_A
3_4
SP_A
4_
SP_A 2
4_4
SP_B
1_SP_B 4
2_4
SP_B
3_SP_B 44_4
SP_B
5_SP_B 4
6_4
SP_B
SP_R 7_4
0_0
SP_R 10_
SP_R 02
0_14
SP_R
0_
SP_R 22
0_32
SP_R
0_
SP_R 42
0_51
SP_R
0_
SP_R 62
0_63
SP_C
1_4

σI (nC)

0.05

20

BPM name

0.4
0.4

0.2
0.2

0.0
0.0

SP_A
1_G
SP_A
1_
SP_A 01_
SP_A 1
1_M
SP_A
2_1
SP_A
2_
SP_A 3
2_4
SP_A
3_2
SP_A
3_4
SP_A
4_
SP_A 2
4_4
SP_B
1_SP_B 4
2_4
SP_B
3_SP_B 44_4
SP_B
5_SP_B 4
6_4
SP_B
SP_R 7_4
0_0
SP_R 10_
SP_R 02
0_14
SP_R
0_
SP_R 220_3
SP_R 20_
SP_R 42
0_51
SP_R
0_
SP_R 62
0_6
SP_C 3
1_4

0.8

0.6

σy (mm)Horizontal position stability (∼ 10 min.)

1.4

1.2
1 Hz
5 Hz
12.5 Hz25 Hz

1.0

BPM name
BPM name

21
SP_A
1_G
SP_A
1_
SP_A 01_
SP_A 1
1_M
SP_A
2_1
SP_A
2_3
SP_A
2_4
SP_A
3_
SP_A 2
3_4
SP_A
4_
SP_A 2
4_4
SP_B
1_SP_B 4
2_4
SP_B
3_SP_B 44_4
SP_B
5_SP_B 4
6_4
SP_B
SP_R 7_4
0_0
SP_R 10_
SP_R 02
0_1
SP_R 40_
SP_R 22
0_32
SP_R
0_
SP_R 420_5
SP_R 10_
SP_R 62
0_63
SP_C
1_4

σx (mm)Injector Commissioning• Position fluctuation is almost same for different beam repetition.
• Beam position fluctuation in horizontal direction is larger than one invertical direction.
• σx,y: 0.1 mm ~ 0.2 mm (thermionic e- gun)Position stability (rf e- gun)Vertical position stability (∼ 10 min.)

1.4

1.2

1 Hz
5 Hz
12.5 Hz
25 Hz

1.0

0.8

0.6

Injector Commissioning

Summary and plan
• Reinstallation of thermionic e- gun was completed in May of 2015.
• MR Phase I commissioning successfully started w/ thermionic e- gunfor HER and LER injection.
• MR injection w/ rf e- gun was success at the first time (May 31, 2016).
• Rf gun has continuously been utilized for daily operation since last
Wednesday. Bunch charge stability has been much improved.
• Towards Phase II (Oct. 2017):– Low emittance beam (2 nC, 20 mm·mrad)• rf e- gun (2 nC, 10 mm·mrad)• Pre-alignment and countermeasure for ground motion• Low emittance preservation study in this autumn– BPM readout will be replaced by the high precision one (VME module)in this autumn. (12/91 have been already replaced.)• Development of commissioning tools especially for low emittancepreservation
22

Injector Commissioning

Summary and plan (cont’d)• Towards Phase II (Oct. 2017):– Positron generation• Flux concentrator: New one (work hardening process) will be installed in thisNov. for 12 kA operation.
– Simultaneous top-up (HER, LER (+ damping ring), PF, PF-AR)• Commissioning of New PF-AR BT (Feb. 2017)• Pulsed Quads will be tested by real beam soon. Control and monitor system isunder preparation. All pulsed Quads (30) and steering magnets (36) will be
installed in the next summer.
• Safety system upgrade for simultaneous top-up operation

23

Injector Commissioning

Backup24

Injector Commissioning

Sector Cto5: -10 deg rf phase
R56 =-0.20

Emittance growth due to component misalignment

Norm. projected rms emittance (mm⋅mrad)• Simulation results from 100 different seeds.
• Misalignment of Quadrupole magnets and Accelerating structure:• σ < 0.1 mm: βγε 20 mm·mrad is almost satisfied.
• σ > 0.1 mm: emittance preservation is required by some methods.
<Emittance growth>・quadratic curve as a function of
misalignment
・final emittance depends on error
seed
Simulation

20 mm·mrad
Misalignment σ (mm)SAD code, Elegant
Initial bunch charge: 5 nC
Initial emittance: 6 mm⋅mrad
Initial bunch length: 10 ps (FWHM)
Initial energy spread : 0.4%
Initial beam energy: 20 MeV
Uniform longitudinal beam distribution

Injector Commissioning

Energy spread requirement••

For the synchrotron phase space injection, small energy spread (0.1%) is required.
A rectangular beam distribution in the longitudinal direction is required for the
beam with bunch charge of 5 nC (Phase III).
• Laser shaping technique (temporal manipulation)

Gaussian shape

0.1
Rectangular shape
26

S. Kazama et al., IPAC’15, MOPWA053

Injector Commissioning

Offset injection (experiment)• Feasibility of offset injection was studied w/ bunch charge of 0.3 nC(thermionic gun).
• Changing the excitation current of steering magnet at Unit A4.
• Emittance was measured multiple wire scanner at Sector B end.
• We will conduct this measurement w/ rf gun.

27

Injector Commissioning
Emittance simulation w/ 10 misalignment seeds (accelerating structure).
Sector C to Sector 5 (Linac end)
Assuming 5 nC, initial emittance of 10 mm⋅mrad (SectorC)
When bunch charge increases by 10%, emittance increases by 6.5%.
Try simulations w/ measured component misalignment, dynamic beam line
movement, energy jitter.
γ ∈x @ 5-sector End

•
•
•
•
•

Emittance w/ bunch charge fluctuation

×10−6
15
14

12.4 => 13.2 mm⋅mrad

13
12
11
4.4

5 nC => 5.5 nC
4.6

4.8

5

5.2

28

5.4
5.6
charge [nC]

Injector Commissioning

Emittance measurement•••

Emittance as function of bunch charge (drop the results w/ large error )Small bunch charge (< 1 nC) shows good emittance at injector section.
– < 10 mm⋅mrad (Vertical), < 15 mm⋅mrad (Horizontal)
Results at SectorB show larger emittance than our goal.

20

29

Injector Commissioning

Optics design•

Quadrupole triplets will be installed in merger line.

•

Beam size is not so large in comparison with bore radius of vacuum chamber .

Merger line√⁠​𝛽↓𝑥(√⁠√⁠​𝛽𝑚↓𝑦)(√⁠𝑚 )
​𝜂↓𝑥
𝑚
​𝜂(↓𝑦
(mm)
Hor. beam
size (mm)𝑚)Ver. beam size (mm)Beam energy (MeV)30

Injector Commissioning

Beamdiagnostics• Beam position measurement••– BPMs x 91 (strip-line type electrodes)
Beam profile/Emittance measurement– Fluorescent screen monitors x100
– Single wire scanner x1– Multiple wire scanner x5
Bunch length measurement– Streak camera x3

31

Injector Commissioning

New BPM readout system• Current system:– Windows-based digital oscilloscope• 10 GSa/s, 8 bit, 1 GHz bandwidth, 4 channels• Twenty four systems process the signals from 92 BPMs
• Position measurement precision: 25～50 µm (3-BPM method)• New system:– VME module w/ band-pass sampling scheme• 250 MSa/s, 16 bit ADC,
• BPF (fc: 180 MHz, BW: 60 MHz, 22 MHz)• Signal can be well damped within 80 ns(first and second bunch interval: 96 ns)– Measurement precision: 3 µm
104 modules have been manufactured.
12 modules have been successfully utilized for daily operation.

80 ns

Injector Commissioning

Profile monitor• Screen material is made of 99.5% Al2O3 and 0.5% CrO3 (AF995R,
Demarquest Co.). (t: 1 mm)• Linux/PLC (x31) control profile monitor (insert/remove, video signal
select, limit switch, LED illumination, pneumatic air pressure).
• EPICS IOC is running on Linux/PLC. HLA is implemented by Python.
Beam profile
Controller and HLA

Monitor and CCD camera

33

Injector Commissioning

Profilemonitor(cont’d)• 7/97 were replaced by 30-µm-thick one for precise beam
size/emittance measurement (Quadrupole scan).
• CCD cameras have been replaced by new one.
– Allied Vision: GC650 w/ GbE– Ext. trigger input– EPICS IOC, CSS for HLA

34

Injector Commissioning
Bunch charge
history (rf gun)
5.6 nC

0.75 nC

Injector Commissioning

Bunch compression at Unit-A1
ChicaneLaser length

w/ bunch
w/obunchcompression
compression
10
30 ps
ps

30 ps

36

A1
A1RF
RFΦΦ-30°:
0°: 3010psps

Injector Commissioning

Bunch charge from rf gun in last Dec.
1 week37

Injector Commissioning

Typical beam charge stability

1 hourI = 1.13 +/- 0.144 (nC)

400
350
300

Counts

250
200
150
100

σI: 10% ~ 20%~ 2.5% (KEKB operation)

50
0
0.0

38

0.2

0.4 0.6

0.8

1.0

I (nC)

1.2 1.4

1.6

1.8

2.0

Injector Commissioning

Bunch charge and laser power

Bunch charge (nC)

• Bunch charge (1st BPM) as a function of laser power.
• Clear correlation between themLaser power (Arb. Units)
39

Injector Commissioning

Bunch charge fluctuation• Bunch charge fluctuation as a function of bunch charge (2D histogram)• Oct. of 2013 – Dec. of 2014

Requirement
for Phase-I
40

Injector Commissioning

e- beam parameters
SuperKEKBKEKBEnergy (GeV)

7.0

8.0

HER stored current (A)

2.6

1.1

HER beam lifetime (min.)

6200

Maximum beam repetition (Hz)50

50

Max. # of bunch in an rf pulse

2

2

Emittance (mm⋅mrad)50/20 (Hor./Ver.)310

Charge (nC)

51Energy spread (%)

0.1

0.05

Bunch length σz (mm)

1.3

1.3

Damping ring--

Simultaneous top-up injection

4 rings (SuperKEKB
e-/e+, PF, PF-AR)

3 rings (KEKB e-/e+, PF)Injector Commissioninge+ beam parameters
SuperKEKBKEKBEnergy (GeV)4

3.5

LER stored current (A)

3.6

1.6

LER beam lifetime (min.)

6

133

Maximum beam repetition (Hz)50

50

Max. # of bunch in an rf pulse

2

2

Emittance (mm⋅mrad)

100/20 (Hor./Ver.)

1400

Charge (nC)

41Energy spread (%)

0.07

0.125

Bunch length σz (mm)

0.7

2.6

Damping ring〇-

Simultaneous top-up injection

4 rings (SuperKEKB
e-/e+, PF, PF-AR)

3 rings (KEKB e-/e+, PF)Injector Commissioning

Shot-by-shot beam profile stability

43

Injector Commissioning

Beam position stability @ SP_A1_C5• Measured beam position at first BPM (SP_A1_C5)– σx ~ 0.57 mm– σy ~ 0.11 mm• Fluctuation of horizontal beam position is larger than vertical one.

30 min.

44

Injector Commissioning

Energy spread measurement @ J-ARC• Measure beam energy spread by screen monitor (middle of
J-ARC) w/ and w/o bunch compression at A1 chicane.
• Bunch compression at A1 unit is effective for energy
spread compensation.
A1 chicane Off(w/ bunch compression)

A1 chicane On(w/o bunch compression)

45

Injector Commissioning

Bunch compression @ J-ARC• Isochronous (w/o bunch compression), R56 = -0.3 m (w/ bunch
compression) w/ different RF Φ in SectorA/B• Clear bunch compression has not yet been measured.
• Emittance measurement by multiple wire scanner at Sector2 w/ andw/o J-ARC bunch compression.
w/o compression
w/ compression

Bunch length (ps)

20
18
16
14
12
10
-6

Streak camera at SectorC
-4

-2

0
RF ΔΦ (deg.)

2

4

46

6

Injector Commissioning

Bunch compression at J-ARC• Mitigate transverse wakefield and emittance growth• Initial bunch length 10 ps => 5 ps (bunch compression at J-ARC)– First stage compression at A1 unit (30 ps => 10 ps)• Control R56 and energy spread at J-ARC

Jarc

Bunch
compression

Injector Commissioning

Emittance (misalignment σ = 0.3 mm)• Bunch compression is effective.
• However, still not enough for 20 mm⋅mrad.
R56 = 0 (w/o compression)

R56 = -0.30 (w/ compression)

20 mm⋅mrad

Injector Commissioning

Bunch compression at A1 unit
• To mitigate space charge effect, bunch length is compressed from30 ps to 10 ps.
First Accelerating structure

Laser hut

StreakcameraChicaneRF gun49