LINAC Upgrade Status
Takako Miura / Kazuro Furukawa(Accelerator Laboratory, KEK)
on behalf of Injector LINAC group

B2GM 26-Jun-2015 T. Miura

1

Injector LINAC
High-current and low-emittance injection beams are required
for SuperKEKB. The LINAC has been upgraded for SuperKEKB, andbeam commissioning has been performed during the upgrading.
LINAC Beam Parametersfor KEKB
for SuperKEKB
e+e-e+e-Energy

3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeV

Bunch charge

Primary e-10nC
→1 nC

1 nC

Primary e-10nC→ 4 nC

5 nC

Norm.Emittance (gbe)2100(mm×mrad)100(mm×mrad)

100/20 (Hor./Ver.)(mm×mrad)50/20 (Hor./Ver.)(mm×mrad)Energy spread

0.125%

0.125%

0.1%

0.1%

Num. of Bunch / Pulse

2222

Repetition rate

50 Hz50 Hz

Simultaneous top-up
injection

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

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

B2GM 26-Jun-2015 T. Miura2

Schedule
SuperKEKB commissioning is divided into three stages. (phase1, phase2, phase3)

Calendar2015

2016

Power restriction
in summer

Current plan on going

2017

Power restriction
in summer

2018

Power restriction
in summer

Power restriction
in summer

Phase 1

Phase 2w/o QCS QCS, Belle II install
w/o Belle II

VXD install
w/ QCS
w/ Belle II (no VXD)

w/ full Belle II

L= 1´1034cm-2s-1(KEKB design)

L= 8´1035cm-2s-1

Vacuum Scrubbing
Basic machine tuning
Current=1A

Phase 3
Add more RF

Full Current

Injection Beam
1 nC/bunch
w/o DRno Top-up inj.

w/ DR

low emittance
4~5 nC/bunchw/ DR

Top-up injection

Top-up injection

low emittance
2 nC/bunch
DR commissioning

B2GM 26-Jun-2015 T. Miura3

Major Upgrades of Injector LINACPhoto-cathode RF gun system< e- beam>
Low emittance (ge £ 20 mm×mrad)
high bunch charge ( ³ 5nC)

Positron Damping Ring (DR)Low emittance e+ beam
Alignment error tolerance
1.1 GeV e+
Damping Ringcirc. 136 m

RF gunThermionic gun(10nC primary e-)

1.5 GeV

3.5 GeV
10nC x 2 (prim. e-)
5nC x 2 (inj. e-)e+target

Positron Capture Section- Flux concentrator (FC)- Large aperture S-band accel.
Structures (LAS)
4 times higher e+ yields(local)=0.1mm
s(global)=0.3mm

Low emittance preservation

BCSECSPFECS

chicanePulsed Quads & Pulsed Steering Magnets

PF-AR

HER LER

Event Timing System and Pulsed Modules• Synchronization for 5-rings including DR• 200 parameters are switched at 50Hz each mode
• Optics at the downstream of DR is switched byusing pulsed magnets
B2GM 26-Jun-2015 T. Miura4

Layout of Electron Guns
Ø Thermionic electron gun are located upstairs to produce ~10 nC primaryelectrons for positron production.
Ø Photocathode RF gun for low emittance e- production is located on theThermionic gun
straight line.

(primary e- 10nC)

Merger line

5Photocathode RF gun

Thermionic gun:commissioning was started
from June 2015.
B2GM 26-Jun-2015 T. Miura

5

Quasi Traveling Wave Side Couple RF GUN
Quasi traveling wave (QTW) side couple RF gun
Installed in sept. 2013.
90 deg Hybrid
RFIr5Ce
Cathode0 deg.

beam

Strong focusing force using
accelerating field

90 deg.

QE=110-4 @266nm
Long lifetime

Laser PortQTW type is adopted tomake drift space short.
Drift space = no focus field

Incident angle: 60deg tothe cathode surface.

7 cell, 13.5 MeV@design
Emittance: 5.5 mm-mrad @5 nC (by simulation)
This RF gun can generate e- up to 10 nC

Beam

QTW is made by two standing
waves with 90deg phase difference.

coupling cavities
B2GM 26-Jun-2015 T. Miura

T.Natsui, M.Yoshida
6Yb:YAG/Nd:YAG Laser System for RF-Gun
Yb:YAG (1025-1070 nm) broad band →Pulse shape manipulation is possible.
YbOscilattor

Stretcher

100 fs

30 ps

Yb PCF
Amplifier

0.2 nJ @ 1025-1070 nm

51.9 MHz

30 ps

EO Pulsepicker

Synchronization system

25Hz
Double bunch

2856 MHz triggerFrom Accelerator~ µJ

PCF Yb-doped
fiber amplifier

PCF: Photonic-crystal fiber

Nd:YAG solidstate
amplifier

Yb:YAG thindisk multi-pass
amplifier

Yb:YAG thindisk multi-pass
amplifier~0.8 mJ @ 258 nm

X. Zhou, M. Yoshida, T. Natsui

RF GUN

Yb-dopedfiberamplifier@1035 nmPCF Yb-doped
fiber amplifier

SHG@1064 nmTransmission
Grating
Stretcher

Yb-doped fiber
pre amplifier

Yb-doped fiber
oscillator

Yb:YAG thin-disk
Amplifier2 bunch, 25 Hz achieved(limited by thermal effect)
Final goal is 50 Hz.

~5 mJ

SHG

SHG

SHG: Second harmonic generator
BBO

B2GM 26-Jun-2015 T. Miura7Beam Commissioning of RF Gun
Operation Condition• Laser: 2bunch, 25 Hz• RF gun acc. voltage: limited to 6.5 MV bybreakdown (13.5 MV@design)

Target : 5nC
gex=50 mm×mrad, gey=20 mm×mrad @ LINAC end
gex , gey = 10 mm×mrad @ Gun

Bunch charge just after RF GUN (A1_C5)

Emittance measurement by Quad-scan(m)

1 weekRF GUN

4nC/bunch

Sort for 3h




(Y,M,D)

Screen monitor (t=30µm)

Bunch charge: 3nC@ScreenBeam size was measured shot by shot.
=> Position jitter is not included
gey=26.2 mm×mrad±10%gex=49.2 mm×mrad±10%  

Archived 1/10s

Bunch charge stability depends on the laserstability.

Yb:YAG Thin-disk cooling by soldering Cu plate
was Improved.
R. Zhang, TUPWA071
Laser power increased and stability was also improving.

Ø Measured emittances were higher than target values.
Ø Higher horizontal emittance is due to laser incident
angle.

Need high acc. voltage of RF gun for small emittance

B2GM 26-Jun-2015 T. Miura

8Beam Commissioning of Thermionic e- Gun
Linac A1(QFE) e-/e+ Orbit to LTR dump

B2GM 26-Jun-2015 T. Miura

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Positron Capture Section
T. Kamitani, L. Zang

0.5T DC solenoids : 15 m

FC : Flux concentrator
Large energy acceptance

DC solenoid

LAS : Large aperture S-bandaccel. Structures
Aperture f20mm ® f 30mm

Large transverse acceptanceSolenoid field at e+ production target= 3.5T(FC)+1T(Bridge coil) = 4.5 TFC viewed from downstream

LASLAS + DC solenoid (15m)

3.5T@12kA, 6µs (half sine)

FC/Target

ef2.0 mmHole on-axis

Targetoff-axis

B2GM 26-Jun-2015 T. Miura

May 2014 installed
10Positron beam commissioning @June 2014
Design6/2014

Flux Concentrator

12 kA

6.4 kA

Bridge Coil

600 A

600 A

DC Solenoids

650 A

370 A

14, 12MV/m

10, 12MV/m

Acc Field

orbit-X [mm]T. Kamitani

BAC

e1

Q(e+) = 0.18 nC
at capture section end

orbit-Y [mm]Charge [nC]2targetPositronYe+ > 40 % isnecessary at DRentrance.

June 2014

Q(e+) = 0.12 nC

Primary eintensity at target
Q(e-) = 0.60 nC
Primary Electrone+

Commissioning withdesign parameters
will be started
from Oct. 2015.
So far, thecommissioning
data agrees thedesign welle+ yield (Ye+) = e+ charge (Qe+) / primary e- charge (Qe-)
Ye+@Jun.2014 = 30 % at capture section end, 20% at the end of Sector2 with limited ele/mag fields
B2GM 26-Jun-2015 T. Miura11Radiation shield for higher beam current#15 region

Iron shield

Gradual increase of beam current / shield andcorresponding radiation license applications are planned
B2GM 26-Jun-2015 T. Miura12

Summary• Steady progress towards first MR injection in JFY2015• Finished earthquake disaster recovery in JFY2014• Will make gradual improvements up to Phase-III• Alignment: almost confident on the required precision (0.1mm local, 0.3-mm global), need to maintain for longer term
• RF gun: following recommendations at review meetings
with commercial devices and Nd-based lasers• Thermionic gun: under commissioning• Positron generator: waiting for license tests

Thank you for your attention.

• Will balance between final beam quality andoperation in phases• Will select optimized route depending on availableresources
B2GM 26-Jun-2015 T. Miura

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Mt. Tsukuba

Thank you
SuperKEKB
dual rings
PF-ARPF

14

InjectorLinacBack-up slides

B2GM 26-Jun-2015 T. Miura

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Why need longitudinal pulse-shape manipulation?
Energy spread of 0.1% is required for SuperKEKB synchrotron injection.
15nC
t

5nC 10nC

20nC

  

Energy Spread

Gaussiant

Square



5nC
10nC
15nC
20nC

5nC electronRequirement

Pulse lengthM. Yoshida
16

J-ARCAlignment Requirement
120m
BACRings
12500m345s < 0.1 mm: bge 20 mm·mrad is almostsatisfied.
s > 0.1 mm: emittance preservation isrequired by some methods.

Requirement
Local s < 0.1mm
Global s < 0.3mm
H. Sugimoto17

Hard ware alignment on a girders in sector 3 - 5
Horizontal
VerticalHorizontal
s=34µm

Vertical
s=47µm
T. Higo2015/2/24
May/5/2015

KEK Review HigoIPAC2015 Takako Miura

1818

Floor Movement in a Half Yearstraight laser of 500m + Position Detector (PD)T. Suwada

At expansion joint in tunnel,
large movement is observed.

4-segmented silicon
PD (dia.=10mm)

T. Higo19Expected e+ Yield improvement
Ne+/Ne- @ capture section end

At the entrance of LER, 4nC e+ is necessary for 10nC primary e- .
measurement
2014 June
simulation

T. Kamitani, F. Miyahara

Designed yield atcapture section end
By raising
DC Solenoid fieldFC field andacceleration field,

2014-June
FC 6.4 kA
BC 600 A
DCS 370 A
Acc 10,12 MV/m

FC 6.4 kA
BC 600 A
DCS 650 A
Acc 10,12 MV/m

FC 12 kA
BC 600 A
DCS 650 AAcc 10,12 MV/m

FC 12 kA
BC 600 A
DCS 650 A
Acc 14,12 MV/m

2.7 times
Improvement
expected.

Start from Oct. 201520

LINAC Beam Acceleration Scheme
1.1 GeV
Damping Ringcirc. 136 m

Low emittanceRF gun1.5 GeV

e-/e+ beam with different
bunch charge and energy areaccelerated by 50 Hz repetition
rate.

BCS

3.5 GeV
10nC x 2 (prim. e-)
5nC x 2 (inj. e-)

ECS
3TRF gune+ target &LAS capture section

chicanePFECSPF-ARHER LER
5 nC x2

HER: 7GeV ePF-AR: 6.5GeV e-

4.219 GeV5nCx1e-

LER: 4GeV e+
4 nCx2e+ target
1.5 GeVe+

PF: 2.5 GeV e-

1.1 GeVe-/e+ compatible optics

0.1nCx1Optics is changed for each pulse by using
pulsed quads (Doublet) & steering magnets

B2GM 26-Jun-2015 T. Miura

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Injector LINAC
The upgrade construction toward SuperKEKB has been started from 2010.
High-current and low-emittance injection beams are required for SuperKEKB.
Upgrade of injector LINAC for SuperKEKB is in progress.
Belle IIe+

HER : e7 GeV, 2.6 A

e-LER : e+
4 GeV, 3.6 ASuperKEKB

Circumference : ~3 km
STF

Injector LINAC~600 mPF-ARPFLINAC Provides:
LER:
4 GeV e+ 4nC ´ 2HER:
7 GeV e- 5nC ´ 2PF:
2.5 GeV e- 0.3nC ´1
PF-AR: 6.5 GeV e- 5nC ´ 1e+ Damping Ring
newly constructed

LINAC is the injector for four storage rings (LER, HER, PF, and PF-AR).
The pulse by pulse beam mode switching in 50 Hz which is repetition rate of the LINAC isnecessary for top-up injections into these four rings.
B2GM 26-Jun-2015 T. Miura22Beam Lifetime
Y. Funakoshi
KEKB (design)

KEKB (operation)

SuperKEKB Design

LER

HERLERHERLERHER

Radiative
Bhabha

21.3h

9.0h

6.6h

4.5h

28min.

20min.

Beam-gas

45ha)

45ha)

24.5min.b)

46min. b)

Touschek

10h-10min.

10min.

Total

5.9h

7.4h

~2.2h

~3.3h

6min. c)6min. c)Beamcurrent

2.6A

1.1A

1.6A

1.1A

3.6A

2.6A

Loss Rate

0.12mA/s

0.04mA/s

0.23mA/s

0.11mA/s

10mA/s

7.2mA/sa) Bremsstrahlungb) Coulomb scattering, sensitive to collimator settingc) w/o beam-beam effectRevolution freq~100kHz

For compensation of the particle loss

Low emittance and high current injection beams are necessary.

4nC@25Hz 2.9nC@25Hz
injection rate are required.

LINAC is a key component of SuperKEKB.
May/5/2015

IPAC2015 Takako Miura

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LINAC Beam Parametersfor KEKB

for SuperKEKB

e+e-e+e-Energy

3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeV

Bunch charge

Primary e-10nC
→1 nC

1 nC

Primary e-10nC→ 4 nC

5 nC

Num. of Bunch / Pulse

2222

Norm.Emittance (gbe)2100(mm×mrad)100(mm×mrad)

100/20 (Hor./Ver.)(mm×mrad)50/20 (Hor./Ver.)(mm×mrad)Energy spread

0.125%

0.125%

0.1%

0.1%

Repetition rate

50 Hz

0.3nC ´15nC ´ 1
5nC ´ 24nC ´ 2

May/5/2015

50 Hz

Beam modes are switched in pulse to pulse
for 5-rings including Damping Ring (DR).

IPAC2015 Takako Miura

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High charge and low emittance are required for SuperKEKB
for KEKB

for SuperKEKB

e+e-e+e-

Energy (GeV)

3.5

8.0

4.0

7.0

Bunch charge (nC)1145Norm.Emittance (gbe)(mm×mrad)

2100

100

100 (H) / 20 (V)

50 (H) / 20 (V)Energy spread (%)

0.125

0.125

0.1

0.1

B2GM 26-Jun-2015 T. Miura25