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

Injector Linac Status

K.Furukawa, BPAC, Oct.2018

1

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+

600 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, Oct.2018

2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

decelera1on

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 installaBon(2018-2019)3

4

PF: 2.5 GeV e-

5
K.Furukawa, BPAC, Oct.20183

Linac Beam Property Requirements

Required injector beam parametersStage

KEKB (final)

Phase-I

Phase-II

SuperKEKB(final)

Beam

e+

e–

e+

e–

e+

e–

e+

e–

Energy3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeVStored current

1.6 A

1.1 A

1A

1A

–

–

3.6 A

2.6 A

Life time (min.)

150

200

100

100

–

–

6

6

Bunch charge (nC)primary e- 10→1

1

primary e- 8
→ 0.4

1

0.5

1

primary e- 10→44Norm. Emittance(γβε) (µrad)

1400

310

1000

130

200/40(Hor./Ver.)150

100/15(Hor./Ver.)

40/20(Hor./Ver.)

Energy spread

0.125%

0.125%

0.5%

0.5%

0.16%

0.1%

0.16%

0.07%

Bunch / Pulse

2

2

2

2

2

2

2

2

Repetition rate

50 Hz

25 Hz

25 Hz

50 Hz

Simultaneous topup injection (PPM)

3 rings(LER, HER, PF)

No top-up

Eventually

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

Injector Linac Status

K.Furukawa, BPAC, Oct.20184Phase II Operation
Summer Shutdown
Autumn Operation
Phase III
Summary

Injector Linac Status

K.Furukawa, BPAC, Oct.20185

Phase II Operationu Injector operation: Jan.12 – Jul.17
u Proper SuperKEKB injectionu Light source injectionv 3 injections a day, top-up injection for hybrid mode PF experiments
v 5-GeV PF-AR injection testu Stable operation of 64 new pulsed magnets at 50 Hz
u 4-beam simultaneous operation with thermionic gun
u HER injection from RF-gun with slower beam switchingu LER positron injection via damping ringv with adequate timing and bucket selectionu Instrumentation improvements
v Beam position monitors, profile monitors, bunch monitors
v Microwave monitors
Injector Linac Status

K.Furukawa, BPAC, Oct.20186

Pulsed Magnets
DC Quads

Pulsed Quads

Pulsed Correctors

u Pulsed quad x28 and pulsed corrector x 36 were newly
commissioned on new girders (2017 autumn)
u Good power supply stability of 0.01% (24 hours)u PXI bus, PXI-EVR, cRIO, 50 Hz controls with Windows and LabVIEW
u More pulsed magnet commissioning expected (2018-2019)u Girder mover commissioning (1 micron alignment enabled, 2018-)
v Emittance brow-up investigations and mitigations
Injector Linac Status

K.Furukawa, BPAC, Oct.2018

7

New Pulsed Magnets Enabled Simultaneous Injections
HER

LER
Horizontal

VerticalCharge/bunch

Stable Operation
PF

Injector Linac Status

PF-AR

K.Furukawa, BPAC, Oct.20188

RF gun
2nd laser only
X (mm)y (mm)Q (nC)

1.5 nC

1st and 2nd laser together
X (mm)y (mm)Q (nC)

3.6 nCInjector Linac Status

2.4 nCu Three Yb:YAG fiber
oscillators
u Redundant Yb:YAG fiber and
Nd:YAG disk hybrid laser
amplifiersu Dual laser injection on to IrCe
cathodeu Bunch current up to 3.6 nC
v 2.4 nC at the end of linac(Phase II requirement: 1 nC)
K.Furukawa, BPAC, Oct.2018

9HER Injection with RF Gun
RF-gunThermionic gun

・Safety system required 30 seconds toswitch between guns before summer.
Injector Linac Status

K.Furukawa, BPAC, Oct.201810Requirement for SuperKEKB••••

ASer the LINAC, beam go through BT.
In Phase5III ﬁnal, requirement of beam charge is 4 nC for both beam.
Requirement for H/V emiZance of e+ beam is 100/15 μm.
Requirement for H/V emiZance of e- beam is 40/20 μm.

• We have to realize the high quality beam transporta1on
to main ring without emiZance growth as far as possible.
• Otherwise, injec1on rate is worse and luminosity can notreach the target value.

Stage

Phase II
(Mar. − Jul. 2018)

Phase III
(Mar. 2019 −)

Beam

e+

e–

e+

e–

Bunch
charge (nC)

1.5

1

4

4

200/40150

Norm. Emit.
µm(Hor./Ver.)

Energy spread

0.16%

0.1%

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

0.16%

0.07%

Schema1c layout of LINAC and beam transport line (BT)Electron gun
SectorA

Jarc

SectorB

DR (damping ring)

SectorC

ARC (Bending sec1on)

Sector1

Sector2

Sector3

Sector4

Sector5

Beam Transportlines (BT)

Positron genera1on target
BT (Beam Transport line)

Injector Linac Status

K.Furukawa, BPAC, Oct.201811Injection Beam at KEKB and SuperKEKB
u Comparison between achievement at KEKB andrequirement at SuperKEKB Phase III
v Much smaller emittance even with 3-fold higher beam charge
v Still a big challenge that is being resolved

5 3 times
43
2
10Charge (nC)

Injector Linac Status

400

1/7

400

300
200

300
200

100

100

0

0
Norm. Hor.
Emit. (μm)

1/15

1.3 times

0.08
0.06
0.04
0.02

Norm. Ver.
Emit. (μm)

0
σδ(%)

K.Furukawa, BPAC, Oct.201812

Residual Dispersion Function in Linac
DesignMeasured

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

ASer

Dispersion correc1on

Injector Linac Status

K.Furukawa, BPAC, Oct.201813

Residual Dispersion Function in DR RTL•••

There are two
ARCs in the DR
extrac1on line.

This table shows values of residual dispersion before and aSer
correc1on.

Residual dispersion became smaller in both ARCs.
1/2 [m]<ηx2>1/2dispersion[m]<ηy2>s1ll
Fudge Factor of Quad.
Ine+1st ARC, residual
is notsmall enough.

Correc1on

BeforeAfter

BeforeAfter[%]

2nd ARC

0.079

0.019

0.00940.0077C 4.5

1st ARC

1.05

0.09

0.02

0.01

C 8.2

Example: 1st ARC

Need more study
BeforeASer dispersion correc1on

Y. Seimiya et al.

Op1cs of theextrac1on line

The third graphshows residual
dispersion. Blue ishorizontal and red isver1cal.

Extrac1on Kicker
Extrac1on
SeptumInjector Linac Status

DC Bends

Instead of changing the energy of DR, I changed the strength of Bend, Quad all at
once. For the kicker and septum, Response measurement was done.

K.Furukawa, BPAC, Oct.201814

Phase II Operation
Summer Shutdown
Autumn Operation
Phase III
Summary

Injector Linac Status

K.Furukawa, BPAC, Oct.201815

Summer Maintenance and Improvements
u105 items were performed
uFrom July 17th to October 22thuThere were several near misses (no injuries)
vTaking measures against themuMorning meetings every day

Injector Linac Status

K.Furukawa, BPAC, Oct.201816

RF System Upgrade
Replacement of SHB1 Solid-State
10kW Amp.

RF Monitor Upgrade (Pulse-Shortening Detector)

20 years old,often unstable,
degraded power

Solid-State Sub-Booster System

Replaced single 60-kW klystronwith distributed 600W Solid-State Amplifiers

KL_13 Reinstallation

Injector Linac Status

K.Furukawa, BPAC, Oct.201817

Accelerating Units and Target Holeu Restoration of Unit 1-3
u Replacement of markedly deteriorate accelerating structures in Units 1-1 and5-1 with spares capable of rated power operationu Installation and adjustment of the power supplies for pulse magnets newly
installedu Removal of the used FC base-unit and installation of the dummy plunger withholes for beam jitter measurementu Upgrade of control system for bending and solenoidal magnets

Restored Unit 1-3
Injector Linac Status

Dummy plunger with holes (replacing target)
K.Furukawa, BPAC, Oct.201818

Magnets and Beamline

u Pulse magnets installed in beam-merger line of two preinjectors. (bends x2, quads x4, correctors x4)

u Corrector magnets added. (PY_12_2 [pulsed], BX_DS_C2 [DC])u DC corrector magnets removed in Sector-3, 4, 5.
(pulsed correctors installed in summer 2017 summer)

u Interlock system configuration improved.
(e+ focusing DC solenoids, beam dump line quads)

u Alignment of all beam-line girders and quads measured.
Those with large deviation adjusted.
u Remote control system installed in e+/e- beam separator.
Injector Linac Status

K.Furukawa, BPAC, Oct.201819

Development of New Beam Monitors

A new beam profile monitor with OTR
target and high-precision optical focus
system was installed at SY2 straightline. The resolution is expected to be 8
micron in FWHM.
Injector Linac Status

A new beam timing monitor with striplineelectrodes was installed at #A44. The
resolution is expected to be 2 ps in RMS.
Beam induced RF monitors are improved
to held each other.

K.Furukawa, BPAC, Oct.201820

Planning Pulsed Magnets for Merger Line
24-degree Merger
Bend x2
Thermionic Gun
PF-AR
LER (primary e– for e+）PF
HER
Photo RF Gun

Injector Linac Status

K.Furukawa, BPAC, Oct.201821

Pulsed Magnets for Merger Line

Injector Linac Status

K.Furukawa, BPAC, Oct.201822

Phase II Operation
Summer Shutdown
Autumn Operation
Phase III
Summary

Injector Linac Status

K.Furukawa, BPAC, Oct.201823

Injector Operation in Autumn 2018u Top-up injections to light sources, PF/PF-AR
vWith pulsed magnets at beamline merger of gunsu No positron damping ring operationvOpportunity to study beam behavior at target holeu 25 Hz mostly, followed by 3-day 50-Hz hardware checks
vFirst intense 50-Hz operation since 2011 earthquake in 2019u Emittance brow-up studies and knowledge acquisitionvBeam studies are planned, partially with simultaneous injection

u Emittance preservationv Beam orbit, optics controls and mover application

u Gradual beam current and gradient improvementsv For later injection improvement
Injector Linac Status

K.Furukawa, BPAC, Oct.201824

Beam Phase Space Jitter
ASer dispersion correcBon

Before dispersion correcBon

J-ARC e+ target

J-ARC e+ target

1nC

First ﬁgureshows thestandard
devia1on ofbeam posi1on.
Second ﬁgureshows emiZance
growth induced
by beam jiZer.

Linac end:

Linac end:

28 μm
7 μm

1.8 μm
0.9 μmBeam phase space jiVer is reduced by dispersion correcBon.
••

Small emiZance growth s1ll occurred from aSer the target aSer the correc1on.
We should understand the source of the beam jiZer to prepare for the high charged beam
(4 nC) and for accidental jiZer source which occur at upstream the target.

Injector Linac Status

K.Furukawa, BPAC, Oct.201825

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

e-

e+
e-

φ2
mm

• In order to reveal beam jiZer problem, simula1on analysis of the wakeﬁeld in
the target hole was performed.
• Color varia1on shows diﬀerence of beam posi1on from the center of target
Transverse wakehole.
Longitudinal wake

Wake poten1al in the target
hole.

Enlarged coeﬃcient of beam posi1on
jiZer:~ 0.1@1nC << Measured enlarged
coeﬃcient
Injector Linac Status

X = Beam posi1on
from the center oftarget hole.

K.Furukawa, BPAC, Oct.201826

Target Hole Study
Y. Enomoto et al.

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

Injector Linac Status

K.Furukawa, BPAC, Oct.201827

Simulation for Minimizing Emittance Growth
Induced by Wakefield in Acceleration Structure
Par1cle tracking simula1on was performed toevaluate this emiZance growth.
Simula1on condi1ons:• Measured misalignments of acc. structureand quadrupole magnet were used.
• Iris diameter of acc. structure is about 20
mm.

•
•
•
•

εinj = 10 µm
σz = 1.3 mm
σδ = 0.4%
Q = 5 nC

ASer orbit displacement is minimized

Blue and red dot
show horizontal
and ver1cal
emiZance,
respec1vely.

Phase;III requirement:
Horizontal : - ( <50 μm)
Ver1cal: - ( <20 μm)
ASer emiZance is minimized at the endof LINAC

LINAC end:
γβεX:240 μm
γβεY:120 μm

LINAC end:
γβεX: 22 μm
γβεY: 11 μm

Blue and red line
shows horizontal
and ver1cal
requirement ofPhase III.

s (m)End of LINACs (m)By the orbit correc1on for minimizing emiZance growth, requirement of Phase III can be
sa1sﬁed.
Injector Linac Status

K.Furukawa, BPAC, Oct.201828

Phase II Operation
Summer Shutdown
Autumn Operation
Phase III
Summary

Injector Linac Status

K.Furukawa, BPAC, Oct.201829

Schedule

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

Linac Schedule Overview as of Jun.2018
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
Licensesin steps

Low
Emittance
Beams

Low
Emittance
Injections

4+1 Ring
Injections

DR
Commiss.
1 nC
Phase1

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

1 - 2 nC
Phase2

1 - 4 nC
Phase3

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, Oct.201830

For Phase 3
uSimultaneous injections with some more
pulsed magnets, in order to adjust beam optics
and orbits
uSome more beam instrumentation
improvements
uPositron target / flux concentrator restoration
u50 Hz operation
uFurther instability huntuLow emittance beam developmentsuReliability, reproducibility, automation, etc.
Injector Linac Status

K.Furukawa, BPAC, Oct.201831

Summaryu The injector performed Phase-2 commissioning without
much troubles
u The 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, Oct.201832

Thank you

Injector Linac Status

K.Furukawa, BPAC, Oct.201833