Electron/Positron Injector
Phase-2 Status and Phase-3 Plan
Kazuro Furukawa
for Injector Linac, KEK

Injector Linac Status

K.Furukawa, BPAC, Feb.20191

Overview
Beam Quality Management
Accelerating Structure
Summary

Injector Linac Status

K.Furukawa, BPAC, Feb.20192

Injector Linac Mission

Mission of Electron/positron Injector in SuperKEKB
v For 40-times higher luminosity in SuperKEKB collider
v Low emittance & low energy spread injection beams with 4 times higher beam current³ New high-current photo-cathode RF gun³ New positron capture section³ Positron damping ring injection/extraction³ Optimized beam optics and correction³ Precise beam orbit control with long-baseline alignment³ Simultaneous top-up injection to DR/HER/LER/PF/PFARv Balanced injection for the both photon science andelementary particle physics experiments
Low emittance
RF-gunDamping
Ringe–

Injector Linac

e+

700 m

High efficiency
e+ generator

2x beamcurrent

PF
2.5 GeV

e–

e+ BT

PF-AR
6.5 GeVe – BT

Beam from Injector and Storage Current
SuperKEKB:
7 GeV e2600 mA
4 GeV e+3600 mAPF:
2.5 GeV e450 mA
PF-AR:
6.5 GeV e60 mA

HER
7 GeV

SuperKEKB
3 km

LER
4 GeV

Belle II
40x
Luminosity

Injector Linac Status

The single injector would behave as
multiple injectors to multiple storagerings by the concept of virtual
accelerator
K.Furukawa, BPAC, Feb.20193

Injector Linac Operation in Phase II - III
A

B

10 nC x 2 bunches x 50 Hz (LER)
4 nC x 2 bunches x 50 Hz (HER)
0.3 nC x 1 bunch x 25 Hz (PF-AR)
0.3 nC x 1 bunch x 25 Hz (PF)beam bunches from e- gun
1.1 GeV

1.5 GeV e-

C

1

DR

2

3

DC magnets

e-positron target

C

Injector Linac Status

45

pulsed magnets

1

LER: 4 GeV e+variable energy pulse-to-pulse

deceleration

1.1 GeVe+2

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

4.219 GeV

the same energy

1.5 GeVl beam injection with pulse-to-pulse variablecharge and energy
l device parameter change at 50 Hz (20 ms)
l Pulsed magnet commissioning at 3-5 sectors(2017 autumn), and many more installation(2018-2019)3

4

PF: 2.5 GeV e-

5
K.Furukawa, BPAC, Feb.20194

Linac Beam Property Requirements

Required injector beam parametersStage

KEKB (final)

Beam
EnergyStoredcurrent
Life time(min.)

e+

e–

e+

e–

e+

3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeV

1.6 A

1.1 A

1.0 A

150

200

100

primary e- 10

Bunchcharge (nC)
Norm.
Emittance→1Phase-I

Phase-II

Phase-III (2019)

Phase-III (final)

e–

e+

e–

e+

e–

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

1.0 A

–

–

1.8 A

1.3 A

3.6 A

2.6 A

100

–

–

–

–

6

6

primary e- 8

1primary e- 10

1

→ 0.4

Simultaneous top-up
injection
(PPM)

1

→2

→2

200/40
1400

310

1000

130

(gbe) (mrad)
EnergyspreadBunch /
Pulse
Repetition
rate

0.5

150

100

4

→4
100 / 1540 / 20(Hor./Ver.)(Hor./Ver.)40(Hor./Ver.)
0.13%

0.13%

0.50%

0.50%

0.16%

0.10%

0.16%

0.10%

0.16%

0.07%

2

2

2

2

2

2

2

2

2

2

50 Hz
3 rings

25 Hz

25 Hz

50 Hz

50 Hz

No top-up

Partially

4+1 rings

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

Injector Linac Status

K.Furukawa, BPAC, Feb.20195

Beam Commissioning Activities
Low emittance electronfrom RF gun

High efficiency
positron capture

Injection beam for SuperKEKB
KEKB(− 2010)

Emittance optimization

SuperKEKB
Phase III

Beam

e+

e–

e+

e–

Bunch
charge (nC)

1.0

1.0

4.0

4.0

Normalized
Emittance (μm)

1400

310

Energy spread

0.125%

Injector Linac Status

0.125%

Beam control
with ~70 pulsed magnets

100/1540/20(Hor./Ver.)(Hor./Ver.)

0.16%

0.07%

K.Furukawa, BPAC, Feb.20196Injector FY2019 PlanuRealize stable and sufficient beams for the
first year of Phase 3 commissioning
uPerform 3-year program to recoverdegradation of accelerating structures
uPostpone remaining upgrades until later
years, limit backup devices, in order tosupport longer operation hours even underlimited resources in FY2019

Injector Linac Status

K.Furukawa, BPAC, Feb.20197

Overview
Beam Quality Management
Accelerating Structure
Summary

Injector Linac Status

K.Furukawa, BPAC, Feb.20198Injector Operation in Autumn 2018uTop-up injections to light sources, PF/PF-AR
vWith pulsed magnets at beamline merger of guns

uNo positron damping ring operationvOpportunity to study beam behavior at target holeu25 Hz mostly, followed by 3-day 50-Hz hardware checks
vFirst intense 50-Hz operation since 2011 earthquake in 2019uEmittance brow-up studies and knowledge acquisitionvBeam studies are planned, partially with simultaneous injection

uEmittance preservationvBeam orbit, optics controls and mover application

uGradual beam current and gradient improvements
vFor later injection improvement
Injector Linac Status

K.Furukawa, BPAC, Feb.20199Injection Beam at KEKB and SuperKEKB
u Comparison between achievement at KEKB andrequirement at SuperKEKB Phase III
vMuch smaller emittance even with 3-fold higher beam charge
vStill a big challenge that is being resolved

5 

 

400



400



0.08

4

300

300

3
2

0.06

200

200

1
0

100

100

0.04

0

0

Charge (nC)

Injector Linac Status

Norm. Hor.
Emit. (μm)

  0.02
Norm. Ver.
Emit. (μm)

0
σδ(%)

K.Furukawa, BPAC, Feb.201910

Beam Quality
uBeam emittanceuBeam energy spreaduStabilities of beam position, energy, etc
uBeam position jitter (painted jitter emittance)uBeam energy jitter (painted energy spread)uDegradation of above beam qualities can be thesource of injection backgrounduHardware components and their monitor systems
were much improved
Injector Linac Status

K.Furukawa, BPAC, Feb.201911

Beam Phase Space Jitter Reduction

Seimiya et al.

Before dispersion correction

After dispersion correction
J-ARC e+ target

J-ARC e+ target

1nC

The top plotshows thestandard
deviation ofbeam position.
The middle plotshows emittance
growth induced
by beam jitter.

Linac end:

Linac end:

28 μm
7 μm

1.8 μm
0.9 μmBeam phase space jitter is reduced by dispersion correction.
••

Small emittance growth still occurred from after the target after the correction.
We should understand the source of the beam jitter to prepare for the high charged beam
(4 nC) and for accidental jitter source which occur at upstream the target.

Injector Linac Status

K.Furukawa, BPAC, Feb.201912Residual Dispersion Function in Linac
Y. Seimiya et al.

DesignMeasured

Before• Large residual dispersion was generated
from the J–ARC.
• With dispersion correction by tuning themagnetic field of quadrupole magnets,
residual dispersion became smallenough.
Measured

After

Dispersion correction

Injector Linac Status

K.Furukawa, BPAC, Feb.201913

Energy Stabilizer (Energy FB)
Iida et al.

Jarc

BT
FB ON
FB ON

0.03%
TargetBeam energy( monitored)
Energy knob

The injection energies have beenstabilized within 0.03% by the energy
feedback.

Injector Linac Status

K.Furukawa, BPAC, Feb.2019

Energy jitter
Iida et al.

After suppressing the energy jitter,
the signal from Diamond detector was reduced.

Diamond became small

0.1%

0.05%
CLAWS

Energy Jitter

Energy FB
did not
work well.

Beam background is sensitive to the energy jitter.
Injector Linac Status

K.Furukawa, BPAC, Feb.2019Feb. 4,
2019,

Emittance Growth at Target Hole (?)
Y. Seimiya et al.

e+
e-

e-

φ2 mm

• In order to reveal beam jitter problem, simulation analysis of the wakefield in thetarget hole was performed.
• Color variation shows difference of beam position from the center of target hole.
Longitudinal wake

Wake potential in the target
hole.

Transverse wake

X = Beam position
from the center oftarget hole.

Enlarged coefficient of beam position jitter:~ 0.1@1nC << Measured enlarged coefficient

Injector Linac Status

K.Furukawa, BPAC, Feb.201916

Target Hole Study
Y. Enomoto et al.

• To reveal beam jitter source directly, we temporally replace the target
to dummy target with several hole, which have different diameter.
• In this autumn, we will study the target hole effect on beam jitter.

Injector Linac Status

K.Furukawa, BPAC, Feb.201917

Jitter Emittance after Target
The result is;• The growth of the jitter emittance has
been nothing to do with the small hole.
• Strong correlation between orbit jitterand beta function.
• The beta function after the target islarge to squeeze the beam sizes to passthrough the hole, which causes the large
Although the jitter
orbit jitter.
emittances are still
increased as shown
Position jitters x, y [µm] in the jitter
emittance plots, it is
known that this√bx, √byjitter becomes
smaller when Jarc's
dispersion leakage
is reduced.
They are smallenough at the endof LINAC.

Injector Linac Status

With Target hole(φ2mm)

No Target hole

K.Furukawa, BPAC, Feb.2019

Overview
Beam Quality Management
Accelerating Structure
Summary

Injector Linac Status

K.Furukawa, BPAC, Feb.201920

Injector Linac Beam Acceleration
AB

10 nC x 2 bunches x 50 Hz (LER)
4 nC x 2 bunches x 50 Hz (HER)
0.3 nC x 1 bunch x 25 Hz (PF-AR)
0.3 nC x 1 bunch x 25 Hz (PF)l 60 acceleration units are employedeach with 4 acceleration structures.
l Beams are accelerated/decelerated
as well as energy/bunch-compressedwith them.

beam bunches from e- gun
1.1 GeV

1.5 GeV e-

C

1

DR

2

3

DC magnets

e-positron target

C

Injector Linac Status5

pulsed magnets

1

LER: 4 GeV e+variable energy pulse-to-pulse

deceleration

1.1 GeVe+2

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

4.219 GeV

the same energy

1.5 GeV43

4

PF: 2.5 GeV e-

5
K.Furukawa, BPAC, Feb.201921

Acceleration Unit Configuration
Designed performance of the accelerating unit
SLED output
140 MW(mean) 0.5 us

Klystron output
40 MW 4 us

Waveguides~10% power loss

Va = 160 MV (21 MV/m)by four structures

Injector Linac Status

K.Furukawa, BPAC, Feb.201922

Accelerating Structures
Three types of S-band quasi-constant-gradientaccelerating structures of 2 m in length are employed
as main accelerators
Type

Number in use• PF-type accelerating structures

142(19 + 6 units have issues)• KEKB-type accelerating structures74• Large-aperture accelerating structures (LAS) * 10
* special structure for the positron capture unit
Injector Linac Status

K.Furukawa, BPAC, Feb.201923

Accelerating Structures
PF-type structure

KEKB-type structure

Not interchangeable

Complicated fabrication
Used at 8 MeV/m since 35 years ago
Later raised to 21 MeV/m
Injector Linac Status

Revised structure
Designed for 21 MeV/m
K.Furukawa, BPAC, Feb.201924

Degradation of Acceleration Units
Field emission, reflection (19)Lower acceleration

Cooling water leakage (6)Has to fix

not recoverable

water leak
Need interim fix with sealantSome of water leakage are fatal
Approx. 3 leakages per year, in recent years
May increase as they are built at a timeImproving the identification of a damage in four structuresNo more healthy PF-type backup structures
Have to utilize degraded structures in an emergency
Injector Linac Status

K.Furukawa, BPAC, Feb.201927

New Structure Production
As a solution, structures are newly designedwith lower emission and higher gradient4 structures per year
12 structures for 3 years
Scheduling from FY2018-9 even under limited budget
stopping other improvements
Fabrication schedule
FY20xxContract

FY20xx + 1
DesignMaterials

M
C
ST
B
T
F

加工

検査と測定
表面処理

#1, 2 Structures
M
Coupler
Structure

C

ST

M

B
C

C
ST

C

B

組立
性能調整
最終組立

Injector Linac Status

T

F

C

#3, 4 Structures
M

C
M

ST

B
C

C
ST

C

B

T

F

C

K.Furukawa, BPAC, Feb.201928

Overview
Beam Quality Management
Accelerating Structure
Summary

Injector Linac Status

K.Furukawa, BPAC, Feb.201929

Schedule

RF-Gun e- beamcommissioning
at A,B-sector

Linac Schedule Overview

e- commiss.
at A,B,R,C,1

e+ commiss.
at 1,2 sector (FC, DCS, Qe- 50%)e- commiss.
at 1,2,3,4,5 sector

Phase1: high emittance beam for vacuum scrub
Phase2,3: low emittance beam for collision

Time →
Location
↓
Beam

Low

Low

Licenses

Emittance

Emittancein steps

Beams

Injections

4+1 Ring
Injections

DR
Commiss.
1 nC

1 - 2 nC

1 - 4 nC

Phase1

Phase2Phase3

Without Top-up: Electron: Positron: Low current electron

Injector Linac Status

non damped e+ commiss.
at 1,2, 3,4,5 sectors
e- commiss. at A→5 sectors

Direct PF-AR BT
damped e+ commiss. Improved
at 1→5 Qe+ = 1~4nC RF gun
e- commiss.
at A→5 Qe- = 1~4nC

K.Furukawa, BPAC, Feb.201930

For Phase 3
uPositron target / flux concentrator restoration
u50 Hz operation
uSimultaneous injections for 4 storage rings
with beam stabilization feedback loops
uFurther instability huntuLow emittance beam developmentsuReliability, reproducibility, automation, etc.

Injector Linac Status

K.Furukawa, BPAC, Feb.201931

SummaryuThe injector performed beam improvements after Phase2 towards Phase-3 commissioning
uThe facility is believed to be ready for the first year in
Phase-3, while it may face challenges to achieve the final
beam qualities

Injector Linac Status

K.Furukawa, BPAC, Feb.201932

Thank you

Injector Linac Status

K.Furukawa, BPAC, Feb.201933

Injector Linac Status

K.Furukawa, BPAC, Feb.201934

Lifetime and injection rate
Example : Phase 3-3ex Parameter
Assumed from the lifetime of Phase 2

LER
Life time [sec.]600

Nb=1578,
Itot=2.0A

Loss Rate [mA/sec] 3.0
dI= 3.0mA/s
dt Loss<latexit sha1_base64="s+BtsLlUX3SCiw4ZMf5JKmUJh0o=">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</latexit><latexit sha1_base64="aqFiKmJlWKTNc7yBjRkXrjOOqRA=">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</latexit>⌧ = 600sec<latexit sha1_base64="sA9vHSgUp0aq6Lk28Fp4S3e4t+Y=">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</latexit>dI= Ne frev Ne = QBTend · frep · nbunch · e↵inj
dt Inj<latexit sha1_base64="LQsscpx38xBV2ILxVEn8IqGMpkw=">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</latexit><latexit sha1_base64="Hxf9dA6+LThPfQq5wkZmT9WHje0=">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</latexit>

for I = 2000mA= 3.5mA/s<latexit sha1_base64="8amlSQfTGlLgUwd9ey6MqivkmzQ=">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</latexit>

frev=100kHz
QBTend=1.0nC
frep=25Hz
nbunch=2
effinj=70%

Even if such a low charge injection, the total beam current can be kept
with 25Hz injection.
Injector Linac Status

K.Furukawa, BPAC, Feb.2019

Nondestructive Energy Spread Monitor：
F. Miyahara
eight electrode BPM in Jarc①
sx monitored
with
OctoPos BPM

②

⑦

⑥

sx monitored withscreen monitor③④
The beam spread can bemeasured from the second
moment.
Injector Linac Status⑤

Although the profile with two peaks ② can not berecognized from ⑥ only with the second moment,
it is important to keep the energy spread to ③ or④.
K.Furukawa, BPAC, Feb.2019

Beam energy stabilization

Other voltage fluctuation of klystron power
supply C1: RF Phase
C1: RF voltage
5%

7deg

RF voltage / phase variation
Sometimes the AC line voltage for klystron power supply drops.
Klystron output power is stabilized by
Induced Voltage Regulator (IVR) at the sudden change of AC line voltage.
In Phase 2, IVR stabilization had been done once an hour.

It is planed to establish the IVR feedback in Phase 3.

Injector Linac Status

K.Furukawa, BPAC, Feb.2019