Injection background(BG)
andBeam abort caused by Injection beam
8.Jul.2019
SuperKEKB Review
N. IidaContents
I. Injection background(0) Overview in Phase 3(1) Injection beam

• Improvement for stabilizing the injection beam from Phase2(2) Injection tuning• Tuning for the background reduction of the MR

II. Beam aborts during the injection• ~10% of the aborts during injection were caused by,• Big jump of the orbit in LINAC• Big jump of the beam energy in LINAC

2

Injection BG tuning

BeautifulHarmony+ StabilityNo drift
No jitter+ Injection beam+ Injection tuningOrbitCharge
EnergyEnergy spread
Bunching
Laser
…

No
BG

Septum angle
Vertical angle
EnergyInjection phasekicker height…

Optics correction
TuneiBumpFB target
IP Knobs
Collimator
Luminosity…
+ Ring condition

New era name:“Reiwa”3

Layout of LINAC, BT, Injection to MR
e- beam directly injects into HER

LINAC

HE

Damping Ring (DR)for positron

Injection
Pointsprimary e- for e+: Therminic Gun
e- : RF Gun

e+ beam injects into LER via DR.

SectorA

Jarc

SectorBR

Sector1

Sector2

Sector3

Sector4

Sector5

LERSectorCe+ target

Beam Transport line (BT)Diamond detectors at VXD in Phase3

MR
Many loss monitors are around the MR.
Belle2HER:
VXD(Diamond) BW135

LER:
VXD(Diamond) FW135

Most sensitive to the BG on Belle2.

LIN
AC

The signals from the Diamonds and the loss monitors are carefully monitored to keep the4BG low.
Some aborts are avoided by stopping injection when the signals are high.

JUNE

Injection status in the last 30days
by*=3mmby*= 2mm

by*=8mmby*=2mm

CIM
Injection
efficiency
HER
Inf.

Injection
chargeDiamonddetector

LERInf.

The BG was mainly from the Injection beam for HER,
and from the storaged beam for LER.

5

MAY

The injections were changed

To Continuous Injection Mode (CIM)by*=3mmCIM

LER:CIM test HER:CIM test

HER
Inf.

LERInf.

6

CIM test (9/MAY/2019)

Injection tuning

Even for the continuous injection for both ring, the signals fromDiamond,and CLAWS sensers were dramatically reduced !
How could we keep it ?

7

The tuning method for theinjection was established.
• Search for parameters with small injection
oscillations using Turn by turn BPM on “one-turninjection” mode.
• The continuous injections were succesfully done.
• The stabilities are important after the good tuning.

8Contents
I. Injection background(0) Overview in Phase 3(1) Injection beam

• Improvement for stabilizing the injection beam from Phase2(2) Injection tuning• Tuning for the background reduction of the MR

II. Beam aborts during the injection• ~10% of the aborts during injection were caused by,• Big jump of the orbit in LINAC• Big jump of the beam energy in LINAC

9I. Injection background(1) Injection beam

TBI: To be introduced

Improvements for stabilizing the injection beam
ToolPlace
Jarc, DR, BTA

Energy(A) Energy feedback

BEnergy spread(B) Sub Hermonic Buncher 1(SHB1) for LER beamOrbit
DEFeedback

Talk




TBI



Thermionic Gun

SHB2CAchievement

RF Phase monitor

LINAC

TBI

RF Induced wave monitor

LINAC



OctoPos BPM monitor

Jarc

TBIBTTBI(C) Temperature control

LINAC

Orbit feedback

LINAC

End of BT

(D) Pulsed magnet PS

Sector 3-5

Energy jitter(D) Energy knob phase

Sector B, 2, 5TBI(D) RF phaseLINAC

LINAC and MR

Emittance(E) e- RF gun

RF Gune+ DR(E) Wire scannerF. Miyahara

Y. Seimiya

Orbit jitter

Injection phase FB of Master oscillator

T. MiuraY. Seimiya

T. Miura(Stability)

TBI

R. Zhang

DR

LINAC, BTY. Seimiya

End of BT

T. Mori

10

I. Injection background(A) Energy Stabilizer (Energy FB)

Phase2BT FB ONJarc

T. Kudo,M. Kikuchi

0.03%
TargetBeam energy( monitored)

FB ON

Energy knob

The injection energies have been stabilized within 0.03%(p-p) by the energy feedback.
Diamondbecame small

Diamond Dose
Beam Energy

Energy FB did
not work well.

0.1%

0.05%
CLAWS11I. Injection background(B)Phase fluctuation of SHB1

The fluctuation of SHB depends onthe charge from the thermionic gun.

greenSHB1 Phasered:
SHB2 Amplitude

T. Miura

After worked, SHB1 becomes stable. SHB2 is still moving.
The long electric cable for 114MHz
oscillation replaced to an optical fiber.

SHB2
PFSHB1PF2deg.

2deg.

The diunal diference due tothe phase change almost
disappeared.

SHB1
primary e-2deg.

2deg.

SHB2
primary e-Tuning

May/13/2019
9:00

2.5daysSHB1

2.5days

SHB212I. Injection background(C) Energy spread

In Phase2, it was very hot especially in July.
Temperatureof atmosphere
Temperature
in HV station ofthe thermal gun
Room temperatureof the thermal gun

Arc section in Beam Transport line (BT)Phase2

Before tuning

After tuning

7/13 20:00
Energy spread

Just 40 min.
after tuning
7/13 20:43

Dt=12deg.
Energy spread is very sensitive to the RF phase.
One source of the RF drifts is from the temperature change.
Some countermeasures have been done but not all yet.
→ RF phase/voltage monitors are ready. (T. Miura)
In Phase 3, It was also hot in a few days

33℃

Temperature
Electron current
HER Injection efficiency

The energy spread is monitored only by thedestructive screen monitors.
→ Nondestructive monitors(OctoPos BPM)
have been developed.
(F. Miyahara)

Electron charge
Positron current
LER Injection efficiency
Positron charge
Belle II Diamond

13

I. Injection background
Progress of LINAC in autumn, 2018

(D) Beam Jitter Sources

Causes of several beam fluctuations were revealed by BPMs and the new RF monitors.

Binarization from the Pulsed Magnets(at the straight section) will be repaired.

Y. Seimiya, F. Miyahara, T. Miura

EnergyOrbit

x [mm]

Large variation of Energy gain
near zero cross of RF phaseΔp/p=0.042%

near zero crossΔp/p=0.027%

Beam energy (arb. unit)x’ [mrad]Binarization from the RF Phase(at the dispersive section)

Degree@KL_B3

Degree@KL_C8

near peak

It is planned that the energy knobs are usedcloser to the top of the RF wave.

RF phase monitor
14

I. Injection background

Progress of LINAC in autumn, 2018

(D) Beam jitter (cause and remedy)
Orbit stabilization① Binarization from the Pulsed Magnets• The power supplies will be repaired in this summer.
Beam energy stabilization② Binarization from the RF Phase• Connector or Cable Problems③ Large variation of RF phase near the zero cross• Use the energy knob closer to the top of the RF wave
18:00

Before tightening the cable

20:00

After

T. Miura, T. Matsumoto

Std=0.28
1.5

Before

Std=0.15
0.8

After
The cables areexchanged to softones.
15

I. Injection background(E) Emittance
before tuning

QCS Quench &e- beam Tuning

M. Yoshida

aftertuning

VDX BW135
became“Super clean”.
Energy spread

gex=147µm
gey=262µm

Energy spread

gex=99µm
gey=68µm

16Contents
I. Injection background(0) Overview in Phase 3(1) Injection beam

• Improvement for stabilizing the injection beam from Phase2(2) Injection tuning• Tuning for the background reduction of the MR

II. Beam aborts during the injection• ~10% of the aborts during injection were caused by,• Big jump of the orbit in LINAC• Big jump of the beam energy in LINAC

Since the efforts have been made to stabilize, fine tuning is always necessary.
Talk about the experience will be presented.

17

I. Injection background(2) Injection tuning• Injection phase

HER

Before injection after no beam or
optics changed, the injection tuning
was done by using TBT BPM toreduce the amplitude of the tunes
with one-turn injection mode
(Injection kicker2 was Off).
New method !

Y. Ohnishi

nsFor the synchrotron tune, the best
injection phase with low backgroundwas 12deg.(in 571.2MHz) lower than
the TBT adjusted phase.

nx

Amplitude of ns

finj=226deg.

finj=237deg.

The amplitude was much lower.

finjnx, ny were also tuned
as well as ns.

234deg.

222deg.

This suggests that the electron beam
18 would
have long tail in longitudinal phase space?

I. Injection background(2) Injection tuning (Cont’d)Even once the injection parameters are fixed, sometimes they should be re-tuned
during the operations.
• Septum angle(Horizontal injection angle) (, Kicker tuning)• Vertical injection angle• Injection phase
The tuning was repeated cyclically.
Injection
efficiency↑• H. Tune

Injection efficiency ↑BG ↓Septum angle

For especially,
Septum angle
Low(3.42mrad): High currentHigh(3.44mrad): Low current↓ BG

nxnx tuning is effective
HER injection became beautiful!
19

Contents
I.

Injection background(0) Overview in Phase 3(1) Injection beam

• Improvement for stabilizing the injection beam from Phase2(2) Injection tuning• Tuning for the background reduction of the MR

II. Beam aborts during the injection• ~10% of the aborts during injection were caused by,• Big jump of the orbit in LINAC• Big jump of the beam energy in LINAC• There is no abort causing the QCS quench due to injection beam in Phase 3.
Abort caused by LINAC abnormal beam:
May/31 LER abort 0/9
Jun./01 LER abort 2/4
Jun./06 LER abort 0/3
The other causes are still unknown.

20II. Beam aborts during the injection

Operation log for SuperKEKB on one day

Energy jump

The new addional
21
information from LINAC

II. Beam aborts during the injection

Y. Seimiya, F. Miyahara

Due toFast beam position monitor(BPM) in LINAC
the injection beam just before abort can be monitored.

b. 1/Jun. 21:19

a. 1/Jun. 19:56• LER D6V2 LM abort
No energy diviation
Dispersive point

Orbit diviation

Straight line

One station for the power supplies(PS)was set to 0 [A] due to a trigger missingof the PS.

• LER D6V2 LM abort

Beam energy was 50 MeV lower.
Dispersive point

Straight line

The klystron 51 was down at the time.
The estimation was -46.5 MeV which isconsistent with the beam position.22

II. Beam aborts during the injection

Simulations
In the both cases, the beams had been injected into the LER.

a. 1/Jun. 19:56

b. 1/Jun. 21:19

BT lineBT lineY. Seimiya

a. The collimators(CHP, CVP) in the BT could cut the beams with the abnormal orbits.
b. The lower energy beam can not be cut in the BT due to the Energy Compression System(ECS) at
the end of the LINAC.
We have to install one more collimator, which is under planning.
•23

In HER, the collimator for protecting the lower energy beam will be also prepared in this summer.

II. Beam aborts during the injectionLower energy beam after the ECS
in front of the BT

The longitudinal phase space
LINAC end

R56=0.9

Exit of the chicane

Exit of ECS acc. structure

DE=

DE=-50MeV

Since the ECS restores the beam energy, the beam can inject while being shifted in the time24
direction, which could cause a LER abort.

SummaryI. Injection background(0) Tuning method with TBT BPM on one-pass mode is established.
(1) Injection beam
• Improvement for stabilising the injection beam will be continued.

(2) Injection tuning• HER• Some parameters such as the septum angle, the vertical steerings should
be tuned to keep the low BG.
• The tunes or collision tunings sometimes affects to the BG.

• LER injection is very stable. Thanks to the DR.

II. Beam aborts during the injection can be monitored• ~10% of the aborts during injection were caused by theabnormal orbit or energy in LINAC.
• The abnormal beam will be cut by the new collimators.
• The other causes are still unknown.

25

Backup26

I. Injection background(E) Emittance and Energy spreadof the injection e- beam
Emittances measured by the wire scanners at the BT

3rd/Jun . (before tuning)
Energy spreadsxsygex=147µm
gey=262µm

11th /Jun. (after tuning)
Energy spread
gex=99µm
gey=68µm

The energy spreadbecame smaller.

Especially the vertical emittance became smaller.
27

I. Injection background(2) Injection tuning (Cont’d)• iBumpFB Target

V. Offset

Tune FB
was stopped

28

II. Beam aborts during the injection

Pulsed quads, Pulsed steering at
the abort
One station for the power supplies was set to 0 [A] due to a trigger missing.

Y. Seimiya

Trigger failure of the power suppliesof the pulsed magnets.

29