22/06/06 B2GM

Operation status and upgrade
plan of the KEK-LINAC
Takuya Natsui1

Beam status
2022abFinal goal

Beame+e-e+e-Energy

4.0 GeV

7.0 GeV

4.0 GeV

7.0 GeV

Bunch charge
1st , 2nd [nC]

3.5 , 3.0

1.8 , 1.5

4.0, 4.0

4.0, 4.0

Normalized
emmittance[mm-mrad]120, 5(Hor. , Ver. )40-20, 40-20(Hor. , Ver. )100, 15(Hor. , Ver. )40, 20(Hor. , Ver. )Simultaneous
top-upinjection

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

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

2

Electron beam charge history of 2022ab
Four months history

RF Gun generation

Linac end

Stable beam charge due to charge feedback using laser power adjustment
3Charge stabilization of KBE beam

2021c

2022abRF Gun generation

Linac end

The bunch charge stability was significantly improved compared to theprevious period.

4Electron beam orbit in Linac and BT52 bunch operation of KBE

Sometimes we try to 2 bunch operation.
But injection rate is not so good. We use 1 bunch operation in usual.
Beam orbit seems good. But emittance value is not so good, maybe.

6Electron emittance measurement.
Sometimes we achive a very good condition. The next task is to maintain this condition.

Hor. 20.1, Var. 17.8
Bmag is Good
(Target value : 40, 20)

7

Positron beam charge history of 2022ab
GunPrimary at target

Positron generation

Charge reduction
for MR request

End of LinacMaximum beam charge is 3.5 nC

8

Two bunches
operation historyof KBP

We succeeded to the twobunches operation for KBP.
2nd bunch charge is almost sameas 1st bunch charge.
We can maintain a stable twobunches injection.

9

Long term charge history of KBP beam
12charge (nC)

10
864
20
15_T

16_5

28_4
position

DC_4

design2020ab-run

2020ab-study

2020c2021a2021b

2021c

2022ab(暫定)

58_4

10

Injector line
We have two lines in injector sector for positron and electron beam.

Pulse Bend Magnet

11

Improvement of 24 deg slope line for KBP beam
Leal time dispersion measurement panel

Magnetadjustment

Big dispersion had been remained.
We had to remove this dispersion in straight line.
12Adjust magnets (PB_J1, J5, Q mag J2, J3, J4)
We found a better magnet condition

13

Pulse bend magnet current (AT_J1, J5) improvement
Noise reduction atcontrol signal andmonitor

Monitor improved
Start feedback
Stable pulse magnet operation was realized in 2022ab

14

Improvement of beam fluctuation of KBP
2021c2022b

Small beam charge fluctuation
at target.
15

Injection summary

N.Iida16

Measured emittances of the injection beam

N.IidaStill remain a emittance brow up in BT. We have to study the brow up problem.

17

Linac Upgrade 2022-2026• Pulse magnet• Girder Mover• PCB capacitor replace• electron ECS• RF gun• Positron target and capture• Acceleration structure

UpgradebudgetNormalbudget18

Pulse magnet upgrade
Fast kicker
Injector DC gun
A sector

FCTargetC sector

New large pulse
Q magnet andfast kicker

RF gunDumping
Ring

RF gunR sector(J-arc)B sector

Pulse magnet(already used)LAS

1 sector

2 sector

3 sector

4 sector

5 sector

We already use a pulse magnet in 35 sector.
But we need additional pulse
magnet at J-arc for matching withboth beam of KBP and KBE
19We don’t have pulse magnet at B,Csector due to a big beam aperture.
A sector

FCTargetC sector

RF gunDumping
Ring

RF gunR sector(J-arc)B sector

DC gunLAS

1 sector

2 sector

3 sector

4 sector

5 sector

Beam loss at J-arc, because of common optics

20

8 large pulse magnets will be installed at entrance and exit of J-arc

✔

✔
✔

✔

✔

Fast pulse kicker✔

Pulse Q magnet✔
✔

このパッケージは元の位置から 450 mm 上流へ✔
21

New pulse Q magnet has large aperture for positron primary22

New pulse magnet driver is also developing.
3-5 sector typeNew driver

Max Voltage [V]230400Max Current [A]

330600Magnet inductance [mH]

11.5Control method

ID-VGE analog controlPWM

23

Fast kicker for 2nd bunch

Fast kicker affects to only 2nd bunch.
Pulse raising time must be under 96 ns.

24

Energy Compression System (ECS) for KBE
Install accelerating structure in BTe

We make R56 in Arc0 of BTe25

We will add a klystron in end of linac for electron ECS.
Now we are ready to install a new klystron and modulator.

Combiner Hybrid

Existing KL_61 waveguide
BTe-ECS waveguide26

PFN capacitor replace for PCB countermeasures
PCB : Poly Chlorinated Biphenyl• 40 capacitors in one klystron
modulator

PFN– 2 series, 20 ladder PFN• We have to replace about 600
capacitors• This upgrade does notcontribute to performance
improvement.

• Voltage：47kV• Capacitance：0.0155μF

27

New acceleration structure
The old acceleration tube must be replaced.
New structures have higher accelerating gradientand lower surface electric field.
We will replace to a new accelerating structure toreach a collision at the higher energy resonance of(6S).

New accelerating structure is high quality

New pulse compression system
also developed.

28

New positron rotation target and FC
Rotation target is very nice system for not
only positron beam but also electron beam.
That why, both beam orbit will be on theaxis and big aperture for electron beam.

29

7 items of injector upgrades by 2026

Pulse magnet

RF gunGirder Mover

Positron

PCB

ECS

Acceleratingstructure30SummaryElectron beam• Beam charge is very stable.
• Emittance is almost satisfied a required value.
Next challenges• 2 bunches operation.
• How to maintain good emittance.
• Increase beam charge, over 2.0 nC.
• Avoid emittance brow up at BT.
Positron beam
• Beam charge is almost reach the target value.
• 2 bunch operation is succeeded.
• Emittance is almost satisfied a required value.
Next challenges• Increase beam charge to 4.0 nC• Stable operation.
• Avoid emittance brow up at BT.

Linac upgrade is on going.
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