Injector LINAC Status

Kazuro Furukawa for Injector LINAC<http://www-linac.kek.jp/linac/>
Data from all injector group members,
especially M.Satoh, F.Miyahara, R.Zhang, N.Iida, Y.Enomoto, M.Yoshida

Injector linac status

K.Furukawa, Nov.2021

1Linac Operation Overview
u Operated 5579 hours in FY2020 till March,giving a higher interruption rate in order tomeet the more precise SuperKEKB injection
requirementu Gave a higher pulse repetition rate or dual
bunches for higher SuperKEKB storage
currentsv Lower injection efficiency with dual bunches atsmaller beta-y*, needing more study time(in the future)

FY2020: 5579 hours, 3.01% failure, 1.52% injection stopu Beam emittance from linac is reasonable,
however several times increase in BT
u Reduction of DR emittance is ongoing, with
injection/extraction optical matchingu Beam charge increase for electron andpositron

Emittance measurement tool
Injector linac status

K.Furukawa, Nov.2021

2

Simultaneous Top-up Injection
Low emittance
RF-gunDampingRing

e–Injector Linac

e+

700 m

High efficiency
e+ generator

2x beamcurrentPF
2.5 GeV

e–e+ BTPF-AR
6.5 GeVe – BT

Beam from Injector and Storage Current
SuperKEKB:
7 GeV e2000 mA
4 GeV e+2800 mA
PF:
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

Typical daily operation before summer

Typical 24 hour operationv Red: Storage
HER:
680mA, 12.5 – 25 Hz, 1 bunch, 1.3 nC
current (mA)
LER:
840mA, 12.5 – 25 Hz, 1-2 bunch, 2.6 nC v Blue: Injection
PF ring: 450mA, <1 Hz, 0.25 nC
charge (nC)
PF-AR: 50mA, <1 Hz, 0.3 nCv Green: Injection
rate (mA/s)

Injector linac status

K.Furukawa, Nov.2021

3Simultaneous Top-up Injection
Low emittance
RF-gunDamping
Ringe–Injector Linace+700 m

High efficiency
e+ generator

2x beamcurrent

PF
2.5 GeVe–e+ BT

PF-AR
6.5 GeVe – BT

Beam from Injector and Storage Current
SuperKEKB:
7 GeV e2000 mA
4 GeV e+2800 mA
PF:
2.5 GeV e450 mA
PF-AR:
6.5 GeV e60 mA

HER
7 GeV

SuperKEKB
3 km

LER
4 GeV

Belle II
40xLuminosity

Starting operation after summer

Typical 24 hour operation (before summer)
v Red: Storage
HER:680mA, 12.5 – 25 Hz, 1 bunch, 1.3 nC
current (mA)
LER:840mA, 12.5 – 25 Hz, 1-2 bunch, 2.6 nC v Blue: Injection
PF ring: 450mA, <1 Hz, 0.25 nC
charge (nC)
PF-AR: 50mA, <1 Hz, 0.3 nC
v Green: Injection
HER 1-2 bunch 2 nC rate (mA/s)(after summer) LER 1-2 bunch 3 nC
Injector linac status

K.Furukawa, Nov.2021

4

Injector Linac Improvementsu Short term：Summer 2021
v Optical element and amplifier for 2nd Laser of Rf-gun
v Photo cathode and laser window replacementv Core/Edge network switch upgrade
Laser stabilization with DOE elementv 7 pulsed corrector magnet additionv Solid-state amplifiers replacing mid-power klystronv Damaged waveguide renewal
v Beam position monitor just after positron target
v Improved secondary RF-gun as backup
New beam position monitor
v Improved protection against AC 50Hz fluctuation

Secondary RF-gun

Core network switchesu Mid-term：up to 2026
v Pulsed magnets & kicker
v Precision girder mover
Pulsed magnets
High-precision mover
PCB capacitor renewalEnergy compression
v Energy compression systemv Improved RF-gun
v Improved positron generationv Accelerating structure upgrade
Accelerating structure
Positron generation
RF gunv PCB capacitor renewal
Injector linac status

K.Furukawa, Nov.2021

5

KEKB ARC Review Recommendations
u R2.1: Check RF gun timing and perform careful RF conditioning of the QTW RF
gun to recover the RF pulse width and, possibly, to improve the 2nd bunch
emittance.
u R2.2: Find and eliminate the source of emittance blow up in the beam transport toimprove injection efficiency and minimize radiation damage to the collimators anddetector.
u R2.3: Sufficient beam time should be allocated for linac beam studies to achieve
and maintain optimum injection performance.
u R2.6: The middle- or long- term upgrade plans must be reviewed by the ARC, ITF,
and/or external experts.
u R4.1: Check the injection hardware for both LER and HER, ensuring that theequipment works with the design parameters under the correct circumstances.
In particular, the conformity of the waveform of the kicker power supplies needs
to be checked.
u R4.6: Pursue the design of the straight transport line and examine its
performance.
Injector linac status

K.Furukawa, Nov.2021

6Positron Generation Improvements
u Improvement
at summer 2020v Cu-Ni alloy forflux concentratorv Routine 12 kA operationv Correctors inside of15-m solenoid sectionv Accelerating structure & loadv Stable 3 nC positron delivery

Injector linac statusbridge coils

top view
10 nC
primary e-

DC quadspoilersolenoid
LAS Accel.
structuretargete+beamhole

4 nC injection eFlux
Concentrator

pulsed corr.
pulsed quad

K.Furukawa, Nov.2021

7Positron Reaching Designed Chargeu Positron beam tuning
after hardware improvements
u Solenoid field and accelerating field
are not optimal yet
u Needs further tuning for the futurev Often operated at lower beam current
depending on the stored beam

Present emittance requirement: γεx 100 µm, γεy 30 µm

Injector linac status

K.Furukawa, Nov.2021

8

Future Improvementu Further optimization is considered
vPositron LER storage current is higher and the lifetime is shortervWe may need more positron charge
Under present configuration:³ Such as 6 nC / bunchvCloser target placement
vBeam instrumentations
vCorrectors
vetc.

Magnetic field is lower
and asymmetric
Positron would be spirallytransferred

Target material : W
Target size : Φ4 x 14
Inserted in the pure Cu block
Connected by HIP process
looking from downstream side
Injector linac status

K.Furukawa, Nov.2021

9

Electron Beam from RF gun
u Tight configuration for cavity and optical elementsv Dual laser
introduction with
1st and 2nd laser
for photocathode³ Flat laser beamwith DOE

v As well as laser
application forlaser cleaning³ Focused laser beam

Injector linac status

K.Furukawa, Nov.2021

10

Electron Beam from RF gunu Beam emittancevPresent requirement γεx 100 µm, γεy 40 µm
vStability improvements³ DOE for 2nd laser³ Stabilization loops³ 7 pulsed correctors

At 1.5 GeV

vEmittance blow-up
in later part of BT³ Needs further studies

Injector linac status

1st half of BT

K.Furukawa, Nov.2021

11

Injector Linac Upgrade Items 2022 - 2026
Thermionic gun with 10 nC

BJ-arc

ARF gun with 4 nC

PF ring
2.5 GeV
0.2 nC

1.1 GeV positron
damping ring

1.5 GeV
Bunch compression

3.2 GeV, 10nC x 2C1 Positron
generation 2LER positron
4.0 GeV
Energy compression 4 nC x 2

Energy compression

345PF-AR
6.5 GeV
0.2 nCHER electron
7.0 GeV
4 nC x 2

Pulsed magnets/kickers High precision movers PCB capacitor renewal New energy compressor

RF gunInjector linac status

Positron capture section

Accelerating structure
K.Furukawa, Nov.2021

12

Pulsed Magnet, Kicker and Mover
Injector linac injects beams into SuperKEKB HER, LER as well as light sources PF, PFAR with adequate beam properties at 50 Hz maximum in simultaneous top-up injection
scheme. Pulsed magnets, kicker magnets and girder movers will be installed in order tosuppress emittance blow-up caused by wakefield in accelerator structure with 4 nC perbunch. Kicker magnets may correct beam orbits separated by only 96 ns. Girders may
adjust girders at less than 10 microns.
Ceramics chamber integrated
kicker development

Pulsed magnets and power
supplies
High-precision girder movers

Injector linac status

K.Furukawa, Nov.2021

13Higher Energy Injection and Collisionu Mitigation of accelerator structure issuesv Originally designed for 8 MeV/m, but has been used at 20 MeV/mv Degradation that lead to high field emission rate and discharges
v Water leaks
v Not only Y(6S) but even Y(4S) could be sufferedu 4-year plan to fabricate and install new accelerator structures

Injector linac status

K.Furukawa, Nov.2021

14

New Accelerating Structuresand ECS for Electron Beam

7% of 230 accelerating structures will be
replaced for mitigation of 40-years ofdegradation by discharges and water leaks.

Energy compression system (ECS) for
electron beam will be installed at thebeginning of the beam transport line.

電子銃空洞と光陰極回折光学素子による形状補正

Additional replacement will benecessary in nearfuture.

EEHHEHEEHEE
H

Injector linac status

EK.Furukawa, Nov.2021

15

Capacitors with PCB contamination
Capacitors (up to 1200) in power modulatorswith low-level PCB produced before 1991 will bereplaced following the law.
Summary:
Capacitors in high-power
Injector linac continues to improve withklystron modulators
hardware upgrade in above 7 category
regions from 2022 to 2026.

Injector linac status

K.Furukawa, Nov.2021

16

Summaryu Injector LINAC continues reasonable injections insimultaneous top-up injection mode.
u Emittance blow-up at the 2nd half of beam transport line isstill a mystery, but partially relaxed recently with finerparameter tuning to make injection and storage beams
match.
u The injector upgrade implementation is discussed in 7
categories for the final beam parameters with higher
bunch charges and lower transverse and longitudinalemittances.
Injector linac status

K.Furukawa, Nov.2021

17

Thanks

Injector linac status

K.Furukawa, Nov.2021

18

Linac Beam Property Requirements

Linac Beam Parameters for KEKB/SuperKEKB
Stage

KEKB (final)

Beame+e–e+e–e+e–e+e–e+e–

EnergyStoredcurrent
Life time(min.)

3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

1.6 A

1.1 A

1.0 A

1.0 A

––

1.8 A

1.3 A

3.6 A

2.6 A

150

200

100

100

––––

66

primary e- 10

Bunch charge
(nC)
Norm.
Emittance

Phase-II (achieved)

310

Phase-III (final)

primary e- 10

10.5

122→ 0.44→4200/40
1400

Phase-III (interim)

primary e- 8

1→1

Phase-I (achieved)

1000

130(γβε) (mrad)

150/30100/40100/1540/20(Hor./Ver.)(Hor./Ver.)(Hor./Ver.)(Hor./Ver.)150(Hor./Ver.)

Energyspread

0.13%

0.13%

0.50%

0.50%

0.16%

0.10%

0.16%

0.10%

0.16%

0.07%

Bunch / Pulse

2222222222

Repetition
rate

50 Hz

25 Hz

25 Hz

Simultaneous
top-upinjection(PPM)

3 rings(LER, HER, PF)

No top-up

Partially

50 Hz

50 Hz

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

u Gradual improvements keeping light source injections
Injector linac status

K.Furukawa, Nov.2021

19

Alignment

Emittance Preservation
u Offset injection may solve the issueu Orbit have to be maintained preciselyu Mis-alignment should be <0.1mm locally, <0.3mm globally
Mis-alignment leads to Emittance blow-up

Orbit manipulation compensates it

100 samples
Sugimoto et al.
Injector linac status

K.Furukawa, Nov.2021

20

Alignment

Floor vertical movement
in a half year from summer to winter

C3

Injector linac status11182838

Higo et al.

48K.Furukawa, Nov.2021

21

Injector Linac and AC Power Frequency
u Injector linac selects a proper timing depending on the storage ring and injects
beams at a precision less than 10 ps
u It should synchronize with AC power 50 Hz within 2 ms considering the stability of
40 year-old devices
u It is required for the bucket selection mechanism through the damping ring that
the AC line frequency should stay within 49.9 Hz to 50.1 Hz
Figure by Di Wang
PLL

1/51
114.2 MHz

10 MHzLinac-MO
571.2 MHz

Event Clock
AC LineInput

EVG

AC-GEN

EVR

114.2 MHz
2856 MHz10.385 MHz

44 Hz Trigger

EventTimingSystem

10 MHzTriple Sync.
Module for PFAC Trigger

Triple Sync. AC Trigger
Module for AR

MR-MO
508.89 MHz
EVG

TDC

EVG

DR-MR-BS Cycle
44 kHz

1/46

Freq Multi/Div 2
OpticalFanoutUpDown2856 MHz114.2 MHz

571.2 MHz

OpticalFanout

MR-BS Cycle
2 kHz

Linac

Injector linac status

2856 MHzAcc.

MR Rev
99.39 kHz

Down

RF GunUp

ThermionicGun

SHB1

1/49

1/5120DR-MO508.89 MHz

E/O
SHB2

1/51

AR RevPF Rev

TDC Start

TDC Stop

Freq
Multi/Div 1u Additional software andhardware were introduced.

Main MO
510 MHz510 MHz10.385 MHz

u Such an event occurred afew time a month. However,Linac
it increased up to several
Gallery
times a day since April.
It prevented the injection,and triggered RF discharges.

O/E

Upstream
EVRs

Acc.

Downstream
EVRs

For Gun, Klystrons, BPMs,Pulsed Magnets, etc

DR

For Klystrons, BPMs, Pulsed
Magnets, Kicker, etc

Kicker,
Septum

Acc.

LER

IP

Acc.

MR

HER

K.Furukawa, Nov.2021

222856 MHzAcc.