Injector Commissioning

Injector Commissioning
Masanori Satoh(Accelerator Laboratory, KEK)
for the Injector Linac Commissioning GroupThe 20th KEKB Accelerator Review Committee, Feb. 23-25, 2015

Injector Commissioning

Contents
1. Injector upgrade overview
2. Energy spread/low emittance preservation
3. Simultaneous top-up for 4-rings
4. Progress of injector commissioning
5. Issues
6. Summary and plan2

Injector Commissioning

Injector upgrade overview• Low emittance photo-cathode rf gun– e-: 1 nC, 100 mm⋅mrad (KEKB) => 5 nC, 20(H)/50(V) mm⋅mrad (SuperKEKB)– e+: 1 nC, 2100 mm⋅mrad (KEKB)=> 4 nC, 20(H)/100(V) mm⋅mrad (SuperKEKB)

•
•
•
•
•

– Component alignment and fine beam control for low emittancepreservation
New positron capture system (Flux concentrator, Large aperture S-bandstructure), and damping ring
New timing system (bucket selection for DR/MR)
Fast RF monitor, high precision BPM readout and other new
subsystems
Simultaneous top-up injection
Main ring commissioning Phase-I: Jan. of 2016
– e-/e+ 1nC w/o low emittance3

Injector Commissioning

Energy profiles and beam properties
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)AB

 e-/e+ beams are delivered to 4-rings
PulsedQuad (Doublet)with different
bunch charge forand pulseenergy.
 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: 2.5 GeV e+

ee+ targetC

HER: 7 GeV e‐
5 nC x2
PF‐AR: 6.5 GeV e‐
5 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

Energy spread requirement• Energy spread should be less than 0.1%.
• Uniform beam distribution is necessary for mitigation longitudinal
wakefield and reduce energy spread.
• Temporal manipulation of laser system
Gaussian

Uniform

0.1%

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

Offset injection for emittance preservation••••

Low emittance e- beam transport w/o damping ring
Emittance preservation is key issue for e- beam.
Offset injection: intentional change of misalignment seed.
Control the steering magnet at the beginning of Sector C

Bunch
compression

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
Emittance simulation w/ 10 misalignment seeds (accelerating structure).
SectorC to Sector5 (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.
" !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

9

5.4
5.6
charge [nC]

Injector Commissioning

BPM readout system• Current system:– Windows-based digital oscilloscope• 10 GSa/s, 8 bit, 1 GHz bandwidth, 4 channels• Twenty four systems process: 90 BPMs
• Position measurement precision: 25〜50 µm (3-BPM)• 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– Meas. precision: 3 µm
~ 100 modules under pre-delivery inspection

80 ns

Injector Commissioning

e-/e+ beam fast switching (SuperKEKB)• Positron production target with a hole (e- beam pass through inside a hole)• A hole is at the center of beam line for low emittance e- beam.
• Same scheme was successful in KEKB operation.

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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
12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 tunnel has been constructed in Mar. of 2014.
Pulsed bend will be installed at #3 switch yard of Linac.
New BT will be available in Jan. of 2017.

H. Takaki (KEKB review 2013)

Injector Commissioning

Injector commissioning• Injector commissioning has been started in Oct. of 2013.
– Oct. and Dec. of 2013 (e+ beam line construction in Nov.)– Apr. ~ Jun. of 2014
– Oct. ~ Dec. of 2014
– Commissioning (Jan.-Mar. of 2015) was canceled. (operationbudget)– Day shift: beam line construction, laser tuning– Evening shift: beam study– Early morning shift: beam study, rf conditioning

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Injector Commissioning
Chargehistory
5.6 nC

0.75 nC

Injector Commissioning

Bunch charge from rf gun in last Dec.
1 week16

Injector Commissioning

Beam orbit example• During commissioning, 3T gun continuously provides e- beam for
PF ring (top-up).
• Full Linac study can be conducted in Wednesday.
• PF dedicated magnet settings are used in Sector3 - Sector5• RF Φ can switched in pulse-by-pulse (LLRF Φ control)

x (mm)y (mm)

I (nC)
A1 rf gun17
3T gun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

18

0.2

0.4 0.6 0.8

1.0 1.2 1.4 1.6

I (nC)

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)
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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
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Injector Commissioning

Beamdiagnostics• Beam position measurement••– BPMs x 90 (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

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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

22

Injector Commissioning

Offset Injection (experiment)••••

Feasibility of offset injection was studied w/ bunch charge of 0.3 nC.
Changing the excitation current of steering magnet at Unit-A4.
Emittance was measured multiple wire scanner at SectorB end.
We will conduct this measurement w/ various bunch charges.

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Injector Commissioning

Bunch compression at Unit-A1
ChicaneLaser length

w/ bunch
w/obunchcompression
compression
10
30 ps
ps

30 ps

24

A1
A1RF
RFΦΦ-30°:
0°: 3010psps

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

25

6

Injector Commissioninge+ beam measurement• First e+ beam was measured by current system at Jun. 9th 2014.
• Primary e- beam charge: 0.5 nC• e+ charge: 0.02 nC @ SP_28_4
e- beamtargetx (mm)y (mm)

I (nC)

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e+ beamInjector Commissioning

R16, R36 elements at J-ARC• R16, R36 values were measured at J-ARC and SectorC.
• w/ and w/o fudge factors (B’ = Afudge x B’model )• Find suitable fudge factors– Typical fudge factors used for KEKB operation are 1% ~ 5%.

Design value

w/ fudge factors

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Injector Commissioning

Beam loss at first acc. structurex (mm)•y (mm)•
I (nC)

1 (nC)

4 (nC)

Beam transmission rate is reduced at 2nd
BPM (downstream 1st accelerating
structure) when bunch charge from gun
increases.
To improve it, 1st accelerating structure
will be removed soon.

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Injector Commissioning•••

Timing system

Event generator (EVG)/Event receiver (EVR) based on VME64x. (MicroResearch Finland)
EVG (EVG-230) x1, EVR (EVR-230RF) x24
Arbitrary injection pattern can be set via HLA.

Main timing station
EVG
SH_A1
KL_B5/B6

SB_B

Injection

SB_A

e− GunJ-ARCCont-ABC
SB_C

KL_51/52
SB_1

SB_2

SB_3

SB_4

SB_5

e– BT (PF: 2.5GeV, 0.2nC)
e– BT (PF-AR: 6.5GeV, 5nC)
e+ BT (SuperKEKB: 4GeV, 4nC)

e+ Target

EVRs

e– BT (SuperKEKB: 7GeV, 5nC)
Cont-1

Cont-2

Cont-3Cont-4Cont-5

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Injector Commissioning

New timing system configuration
Main timing station

EVG

Main Rings

EVG#1

EVR

Damping Ring

Event signal (optical fiber)

EVR

•
•
•

EVG#2 EVG#3

•
•

PF-AR
PF

Bucket selection: MR, DR# of EVG: 1 => 3
CPU: MVME5500 =>MVME6100
RTOS: VxWorks5.5 => 6.8
Firmware updated

SH_A1
KL_B5/B6

SB_B

Injection

SB_A

e− GunJ-ARCCont-ABC
SB_C

KL_51/52
SB_1

SB_2

SB_3

SB_4

SB_5

e– BT (PF: 2.5GeV, 0.2nC)
e– BT (PF-AR: 6.5GeV, 5nC)
e+ BT (SuperKEKB: 4GeV, 4nC)

e+ Target

EVRs

e– BT (SuperKEKB: 7GeV, 5nC)
Cont-1

Cont-2

Cont-3Cont-4Cont-5Injector Commissioning

Beam injection study(new timing system configuration)• PF/PF-AR injection study were conducted w/ new EVG configurationand software.
• Beam orbit and injection rate is quite similar between current and new
system configuration.
• Wire scanner/BPM works well.
• Long-term stability will be tested after this Apr.
Beam orbit for PF injection (new system)

Beam orbit for PF injection (current system)

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Injector Commissioning

Unit A1 (reconfiguration)••

Thermionic e- gun will be temporarily back in end of this Apr. (for radiation control
license and e+ primary e- generation of 10 nC)– Keep the beam line for rf gun in current position.
– Beam line level of beam line will be changed from 1200 mm to 1950 mm.
– Spare magnets will be used for new beam line.
Thermionic e- gun commissioning will be started in early May.

Merger line

Thermionic e- gunRF e- gun beam line
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1200 mm1950 mm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)

33

Injector Commissioning• Injector commissioning

Issues– Oct. and Dec. of 2013/ Apr. ~ Jun. of 2014/ Oct. ~ Dec. of 2014
– Not enough time for commissioning– e+ commissioning:• Installation of flux concentrator delayed from Dec. of 2013 to May of 2014.
• Twice accidents in Dec. of 2013 and Dec. 2014 (cable burned)• First e+ beam was measured in Jun. of 2014.
• Progress of LAS rf conditioning is slow.
• Not enough primary e- bunch charge at target (≤ 1 nC)– e- commissioning:• Discharge of rf gun cavity. Not enough power for rf gun cavity (12 MW/20 MW)• Shot-by-shot beam stability of charge and position/angle from gun is not yet
enough. Difficulty to keep the high bunch charge in long term period.
• Beam loss at Unit-A1 (chicane) and J-ARC
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Injector Commissioning

Summary and Plan
• Beam commissioning w/ A1 rf gun started in Oct. of 2013.
– Not enough time for commissioning– 5.6 nC (from rf gun), 0.75 nC (Linac end)
– Stability is still issue. (Shot-by-shot and long term)• Unit-A1 reconfiguration will be completed before end of Apr.
Thermionic e- gun commissioning in May.
• Beam commissioning w/ thermionic e- gun (May, June)– Measure Quadrupole center to BPM center offset– Reduce beam loss at Unit-A1/J-ARC– Development of commissioning tools and tests (beam based alignment/
emittance preservation)– Pulsed Quads (x2) and steering (x2) will be tested in Sector2.

• Prepare stable e-/e+ beams (1 nC w/o low emittance) before MR
commissioning Phase-I.
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Injector Commissioning

backup36

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.)100

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.)

2100

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

Design drawing of A1 beam line

39

Injector Commissioning

Shot-by-shot beam profile stability

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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.

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Injector Commissioning

Emittance measurement example (Unit-A1)• Quadrupole scan
• Screen monitor at chicane

ChicaneHorizontal
βγεnx: 15.43 mm·mrad

Vertical
βγεny: 9.42 mm·mrad

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Injector Commissioning

Emittancemeasurement
example(SectorB)• Multiple wire scanner at the end of Sector B• Typical result (1 nC):

εn,x: 66.006 ± 10.755 mm⋅mrad– εn,y: 77.309 ± 14.522 mm⋅mrad–• Charge stability is not so small. Software is under development for
subtracting shot-by-shot beam fluctuation.�

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Injector Commissioning

Emittance measurement• Emittance of rf gun and SectorB were measured by Quad scan andmultiple wire scanner, respectively.
• Results measured in Nov. and Dec. of 2014.
• Vertical emittance is smaller than horizontal one.

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Injector Commissioning

Two bunch operation example

1st bunch charge

2nd bunch charge
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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

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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

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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)48

Injector Commissioning

Summary of e- commissioning
Item

Requirement

Current status

Beam charge (nC)

5 (10 for e+ primary)

5.6 (first BPM)
0.58 (Linac end)

Beam energy (GeV)7

7

Normalized emittance(mm⋅mrad)50/20 (Hor./Ver.)(at the end of Linac)

20/7 (Hor./Ver.)(from RF gun)Bunch charge stability

2.5% (KEKB), 1% (PF/PF-AR)

10% ~ 20%

Bunch compression (Unit-A1)

30 ps => 10 ps

30 ps => 10 ps

Bunch compression (J-ARC)

10 ps => 5 psn/a

Temporal manipulation of laser

Uniform shapen/aEmittance preservation

20 mm⋅mrad (Linac end)n/aMax. beam repetition

50

25# of bunches

22Operation

Simultaneous top-up

n/a49