Injector Commissioning

Injector Commissioning

Masanori Satoh(Accelerator Laboratory, KEK)
for the Linac Commissioning GroupThe 19th KEKB Accelerator Review Committee, March 3-5, 2014

Injector Commissioning

Contents
1. Injector Upgrade
1. Overview
2. Energy spread
3. Low emittance preservation
4. Simultaneous top-up for 4-rings

2. Injector Commissioning
1. Schedule
2. Recent progress of electron commissioning
3. Issues

3. Summary2Injector Commissioning

Contents
1. Injector Upgrade
1. Overview
2. Energy spread
3. Low emittance preservation
4. Simultaneous top-up for 4-rings

2. Injector Commissioning
1. Schedule
2. Recent progress of electron commissioning
3. Issues

3. Summary3

Injector Commissioning

Injector Upgrade Items•••••

Low emittance photo-cathode rf gun (M. Yoshida)
New positron source (T. Kamitani)
Damping ring (N. Iida, KEKB review 2013)
Timing system (H. Kaji)LLRF development (T. Miura)

4Injector Commissioning

e- Linac 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)5050

Max. # of bunch in an rf pulse22Emittance (mm⋅mrad)50/20 (Hor./Ver.)100

Charge (nC)

51Energy spread (%)

0.08

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 Commissioning

e+ Linac Beam Parameters
SuperKEKBKEKBEnergy (GeV)4

3.5

LER stored current (A)

3.6

1.6

LER beam lifetime (min.)6133

Maximum beam repetition (Hz)5050

Max. # of bunch in an rf pulse

22

Emittance (mm⋅mrad)

100/20 (Hor./Ver.)

2100

Charge (nC)41

Energy spread (%)

0.07

0.125

Bunch length σz (mm)

0.7

2.6

Damping ring〇-

Simultaneous top-up injection

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

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

Contents
1. Injector Upgrade
1. Overview
2. Energy spread
3. Low emittance preservation
4. Simultaneous top-up for 4-rings

2. Injector Commissioning
1. Schedule
2. Recent progress of electron commissioning
3. Issues

3. Summary7

Injector Commissioning

Uniform shape of longitudinal beam distribution• Energy spread should be less than 0.08%• Mitigate longitudinal wakefield and reduce energy spread• Gaussian distribution in momentum space

Uniform!

Gaussian!tInjector Commissioning

Energy spread simulation• For 10 ps bunch length,• 〜 0.3% for Gaussian distribution• < 0.08% for uniform distribution• Uniform distribution is necessary.
(Temporal manipulation of rf gun laser)

Gaussianw/ S-band
Uniform
w/ S-band

0.08%

Uniformw/ X-band

M. YoshidaInjector Commissioning

Contents
1. Injector Upgrade
1. Overview
2. Energy spread
3. Low emittance preservation
4. Simultaneous top-up for 4-rings

2. Injector Commissioning
1. Schedule
2. Recent progress of electron commissioning
3. Issues

3. Summary
10Injector Commissioning

Low emittance electron• Low emittance electron beam should be delivered
to MR w/o damping ring.
• Emittance preservation is key issue for e- beam.
• Low emittance rf gun (M. Yoshida, T. Natsui, X. Zhou)• Emittance growth simulation (H. Sugimoto)• 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

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

Emittance growth due to component misalignment

Norm. Projected Emittance (mm⋅mrad)• Simulation results from 100 different seeds• Misalignment of Quadrupole magnets and Accelerating structure:• σ < 0.1 mm: ε 20 mm·mrad is almost satisfied.
• σ > 0.1 mm: emittance preservation is very difficult.
<Emittance growth>・quadratic curve as a functionof misalignment
・strongly depend on error seeds
20 mm·mrad

Misalignment σ (mm)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

Bunchcompression

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

Offset injection for emittance preservation• Offset injection: intentional change of misalignment seed.
• Control the steering magnet at the beginning of Sector CJarc

Bunchcompression
Offset injection

Injector Commissioning

Offset injection (simulation)• Kick angle is relatively small.
• Need a high-precision and stable orbit control.

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

Injector Commissioning

Low emittance electron issue• Component alignment is important• σ < 0.1 mm: enough for emittance (alignment is very difficult)• σ > 0.1 mm: beam manipulation is necessary.
• Simulation w/ misalignment σ 〜 0.3 mm• Emittance can be preserved by• J-ARC:• Sector C:

Bunch compression
Offset injection– Simulation w/ measured misalignment• Alignment requirement:• σ < 0.3 mm for global (whole Linac)• σ < 0.1 mm for local (one Sector ̴ 100 m)

Injector Commissioning

Fast e-/e+ beam switching (KEKB)• Fast control of e- beam orbit
by pulsed steering magnet and e+target with a hole.
• Similar system will be installed forSuperKEKB.
• Beam position and angle should be
fixed at the target location.
view fromUpstream

primary e- for e+e- beam (e- mode)
Hole for e- bypass

Tungsten target:φ 5 mm

4.5 mmHole: φ3 mm

Injector Commissioning

Contents
1. Injector Upgrade
1. Overview
2. Energy spread
3. Low emittance preservation
4. Simultaneous top-up for 4-rings

2. Injector Commissioning
1. Schedule
2. Recent progress of electron commissioning
3. Issues

3. Summary
19

Injector Commissioning

Simultaneous Top-up Operation for three rings• Stored
Beam current
beam current
stability
stability
in Original
sinceOperation
Apr. 2009- KEKB: 1300mAmA(~ 0.05%)(~ 50 %): e-: 12.5 Hz, e+: 25 Hz- PF: 0.05
240 mAmA (~(~ 530.01%)%) :0.5 HzKEKB e-PF

KEKB e+Luminosity
20Injector Commissioning

PF-AR injection: 20 min., twice daily• Interrupt KEKB injection• Problem for SuperKEKB (beam lifetime: 6 min.)Injector Commissioning

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

PF-AR and KEKB share the long part of beam transport line.
Existing tunnel space is very tight.
New beam transport line is required for PF-AR top-up injection.
New tunnel is under construction. (FY2013)
New BT will be available
in Jan. of 2016.

H. Takaki (KEKB review 2013)

Injector Commissioning

Contents
1. Injector Upgrade
1. Overview
2. Energy spread
3. Low emittance preservation
4. Simultaneous top-up for 4-rings

2. Injector Commissioning
1. Schedule
2. Recent progress of electron commissioning
3. Issues

3. Summary
23

Injector Commissioning• Beam charge

Schedule- Our goal -– e-: 5 nC (10 nC for e+ production)– e+: 4 nC

• Emittance preservation at end of Linac– e-: 50/20 mm⋅mrad w/o DR (Hor./Ver.)– e+: 100/20 mm⋅mrad w/ DR (Hor./Ver.)• Stability– Charge– Position– Energy– Energy spread– Emittance– Simultaneous top-up for 4 rings
24

Injector Commissioning

Schedule (cont’d)• Commissioning Stage 1: Oct. 2013 ∼ Mar. 3 2014
– Nov. 2013: e+ beam line construction– Dec. 2013: Daytime: e+ beam line construction (9 ~ 20)
Night shift: e- beam commissioning– Jan., Feb. 2014: Sometimes day shift for e+ beam line construction– Beam injection for PF top-up and PF-AR twice daily– Sector 3 to Sector 5– Full Linac Study: Every Tuesday (Sector A to Sector 5)– We have not enough time for study.
– e+ beam line is not yet completed.
25

Injector Commissioning

Schedule (cont’d)• Result of Commissioning Stage 1– RF conditioning of gun cavity– Laser tuning for e- rf gun– 5.6 nC from gun, 0.58 nC at end of Linac– Development of commissioning tools• Next commissioning Stage 2:– Apr. 11∼ Jul. 1, 2014
• Mid. of May (daytime) ∼ : Commissioning only in Sector A, B(DR construction)– Emittance preservation of e– Install Flux concentrator (End of May) and e+commissioning
26

Injector Commissioning

Schedule (cont’d)• Next commissioning Stage 3:– Oct. – Dec. 2014
– e+ commissioning– Emittance preservation of e- beam
– Goal of this stage:• e- :1 nC w/ low emittance• e+: 1 nC w/o low emittance• Stable beam (charge, orbit,…)• Commissioning Stage 4:– Feb. – June 2015
– Beam Injection to MR (May 2015)27

Injector Commissioning

Schedule (cont’d)• Commissioning Stage 5:– Oct. – Dec. 2015
– During summer shutdown: install pulsed Quadrupoleand Steering magnets– Pulse-by-pulse switching e-/e+ beam
– Increase beam charge, Improve beam stability– Emittance preservation– e+ DR commissioning (Dec. 2015)28

Injector Commissioning

Contents
1. Injector Upgrade
1. Overview
2. Energy spread
3. Low emittance preservation
4. Simultaneous top-up for 4-rings

2. Injector Commissioning
1. Schedule
2. Recent progress of electron commissioning
3. Issues

3. Summary29

Injector Commissioning

Recent progress ofelectron commissioning• Commissioning items:– RF conditioning of gun cavity– Laser tuning for e- rf gun– High intensity beam charge up to 5 nC
– Beam deliver to Linac end– Bunch compression @ A1 unit
– Bunch compression @ J-ARC– Emittance measurement• A1 unit, Sector B, Sector C, Sector 2, Sector 530

Injector Commissioning

Beamdiagnostics• Beam position measurement– BPMs x100 (Strip-line type electrodes)– Data processing• Oscilloscope (σ 25~50 µm) => VME-based one (σ ~10 µm) is under development• Beam profile measurement– Screen monitors x100
– Multiple wire scanners x4• Bunch length measurement– Streak cameras x3

31

Injector Commissioning

RF gun e- beam (5.12 GeV) in Oct. 201332

Injector Commissioning

Typical beam charge• 1 ~ 2 nC (end of Sector B)• 2 ~ 3 nC (RF gun)33

Injector Commissioning
Chargehistory
5.6 nC

0.58 nC

Injector Commissioning

Typical beam charge stability

1 hourI = 1.13 +/- 0.144 (nC)

400
350
300

Counts250
200
150
100

σI: 10% ~ 20%~ 2.5% (KEKB operation)

50
0
0.0

35

0.2

0.4 0.6 0.8

1.0 1.2 1.4 1.6I (nC)

1.8 2.0

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.

36

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 hutStreakcameraChicane

RF gun37

Injector Commissioning

Single shot bunch length measurement at A1 unit
(streak camera)
w/o bunch compression

w/ bunch compression
10 ps

30 ps

A1 RF Φ -30°: 10 〜 15 ps

A1 RF Φ 0°: 30 ps
38

Injector Commissioning

Energy spread measurement @ J-ARC• Measure beam energy spread by screen monitor (middle ofJ-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)

39

Injector Commissioning

Emittance measurement example (A1 unit)• Quadrupole scan
• Screen monitor @ middle of chicane

ChicaneVertical
εny: 7.3 mm·mrad

Horizontal
εnx: 21.3 mm·mrad

40

Injector Commissioning

Emittancemeasurement
example(SectorB)• Multiple wire scanner in Sector B• Typical result:

εn,x: 95.01 ± 19.97 mm⋅mrad– εn,y: 19.67 ± 33.79 mm⋅mrad–• Charge stability is not so small. Software is under development for
subtracting shot-by-shot beam fluctuation.�

41

Injector Commissioning

Bunch compression @ J-ARC• Isochronous, R56 = -0.3 m• w/ different RF Φ in Sector A, B
R56 = -0.3 m

Isochronous42

Injector Commissioning

Preliminary result of bunch compression @ J-ARC• Clear bunch compression is not yet measured.
• Continue bunch compression study• Apr. 2014 ~: Measure emittance by wire scanner @ Sector 2
w/ and w/o J-ARC bunch compression.
w/o compression
w/ compression

Bunch length (ps)

20
1816
14

Streak camera @ C1 unit

1210-6-4-20RF ΔΦ (deg.)

24643Injector Commissioning

Summary of electron commissioning
ItemRequirement

Current status

Beam charge (nC)

5 (10 for e+ primary)

5.6 (first BPM)
0.58 (Linac end)

Beam energy (GeV)

7

5.12

50/20 (Hor./Ver.)

20/7 (Hor./Ver.) (@A1 unit)

Beam charge stability

2.5% (KEKB)

10% ~ 20%

Bunch compression @ A1 unit

30 ps => 10 ps

10 ps ~ 15 ps

Bunch compression @ J-ARC

10 ps => 5 psn/a

Temporal manipulation of laser

Uniform shapen/aEmittance preservation

20 mm⋅mrad at Linac end

n/aMax. beam repetition

50

5# of bunches

21Operation

Simultaneous top-up

n/a44

Injector Commissioning

Contents
1. Injector Upgrade
1. Overview
2. Energy spread
3. Low emittance preservation
4. Simultaneous top-up for 4-rings

2. Injector Commissioning
1. Schedule
2. Recent progress of electron commissioning
3. Issues

3. Summary45

Injector Commissioning

Issues• New e+ source– Flux concentrator• Dec. 2013 => End of May 2014

– Large aperture S-band structure (LAS)– RF conditioning of LAS is not completed.

– e+ commissioning is delayed.

• e- commissioning:– Started in Oct. 2013.
– Not enough time for injector commissioning– Beam stability (charge, position) is not yet enough.
46

Injector Commissioning

Contents
1. Injector Upgrade
1. Overview
2. Energy spread
3. Low emittance preservation
4. Simultaneous top-up for 4-rings

2. Injector Commissioning
1. Schedule
2. Recent progress of electron commissioning
3. Issues

3. Summary47

Summary

Injector Commissioning• Commissioning stage 1: (Oct. 2013 ∼ Mar. 2014)– New RF gun commissioning (laser tuning and cavity conditioning)– High intensity charge– Prepare beam diagnostics and commissioning tools– New Photo-cathode RF gun has successfully manufactured andinstalled. (Summer 2014)• 5.6 nC from New RF Gun• 0.58 nC at end of Linac• Stage 2: (Apr. 11∼ Jul. 1, 2014)– Emittance preservation of e- at the end of Sector B, Sector 5• Bunch compression at J-ARC, offset injection, wake field bump,…..

– Positron beam commissioning (May 2014 ∼)– Beam stability• Charge, Position, Energy, Energy spread, Emittance48

Injector Commissioning

Thank you foryour attention!