Injector Linac Status
Feb. 22nd, 2020
Masanori Satoh (KEK, Acc. Lab.)for Injector Linac GroupThe 36th B2GM, June1 22-26, 2020

Contents• Injector overview• e-/e+ beam status• Beam abort caused by abnormal injection beam
– Abnormal orbit (pulsed magnet issue)– Abnormal energy (rf failure)• Feedback loops• Summary and plan

2020/6/21

2

Injector: Simultaneous top-up to five rings• Photocathode RF gun for HER injection• Thermionic gun for LER (via DR), PF, PF-AR

B SectorA Low emittance RF e- gun
Thermionic DC e- gun1.1 GeV

1.5 GeVC

12 e+DR 3e+ target

e-:Chicane

45Pulsed quads, steering magnets
HER: 7 GeV e-

4.219 GeV
same energy

ee+ target

1.5 GeV
3CDecelerate

1PF-AR: 6.5 GeV eor 5 GeV

LER: 4 GeV e+
1.1 GeVe+2PF: 2.5 GeV e-

345

Pulse to pulse switching:rf e- gun/thermionic e- gun

Thermionic DC e- gun (GU_AT)
w/ 2 subharmonic bunchers and 2 bunchers

・e+ production e-: 10 nC (for LERinjection)・e- study/HER injection: 1 nC・PF injection: 0.3 nC・PF-AR injection: 0.3 nC

RF e- gun
（GR_A1 for HER injection）

Pulsed bend rep. up to 25 Hz (LER + PF + PF-AR)(magnet coil and chamber heating issue)
It will be replaced by new one in summer shutdown 2020.
4

Low emittancerf gunRF e- gun• Yb-doped-fiber and Nd/Yb:YAG laser• IrCe cathode• QTWSC or cut disk cavities
5M. Yoshida, SuperKEKB review, Mar. 14th, 2018

Hybrid laser system for rf gun••

Three Oscillators (two of them are backup)
Yb doped fiber and Neodymium (Nd) doped
laser crystal

1st laser
2nd laser
1st + 2nd laser line:
laser line:
e- beam bunch length～ 10 ps (FWHM)

2020/6/21
R. Zhan, SuperKEKB review, 2019

6 the tunnel
Optics layout ine- source

HER injection beam (rf e- gun) status• HER injection w/ only rf gun since Mar. 11th , 2019.
• Laser system has no significant fault.
• In summer shutdown of 2019, photocathode (Ir7Ce2) was
replaced by new one (Ir2Ce) for aiming at better quantum
efficiency (Qe).
– Discharge, frequent VSWR, gradual decrease of bunch charge• In the last winter shutdown, photocathode was replaced– Ir2Ce => Ir7Ce2

2020/6/21

7

SP_A1_G1 (from rf gun)
QMD10E_M (BT)

5.0

Ir2Ce

4.5

Bunch charge (nC)

4.0
discharge

3.5
3.0
2.5

VSWR

2.0
1.5

discharge
VSWR

VSWR

VSWR

VSWR

1.0
0.5
0.0
10/1

2020/6/21

10/15

10/29

11/12

Date

11/26

12/10

2019

Laser cleaning ～ 30 min.

Before laser cleaning

2020/6/21

M. Yoshida, B2GM, Feb. 6th, 2020

92020/6/21
10/01/072020/0
1/062020/0
1/052020/01/0420

220/01/032020/0
1/022020/01/012020

e- bunch charge (nC)4
LIiBM:SP_A1_G_1:ISNGL:KBE:10S

Ir7Ce23.5

3

2.5Charge feedback ON

1.5

1

0.5

02020

HER injection beam (rf e- gun) status• Laser cleaning for recovering Qe.
• Bunch charge feedback works fine to keep bunch charge
constant.
• In this summer, diffractive optical element (DOE) will be
installed for transverse laser beam shaping (flat top). It could
be help for low emittance beam.
• Laser position feedback will be prepared soon.

2020/6/21

11R. Zhang

e- beam emittance・ ex,y ～15 mm at SectorB, SectorB• Emittance growth at BT2 in both directions.
• Beam based alignment in BT line is now in progress.
• Emittance could be increased at around solenoid section in Sector1.

150

BC

３5

BT1 BT2

HorizontalBC

３5

BT1 BT2

VerticalLinac

Steering magnet and BPM in solenoid section• There is no BPM and steering magnet between e+ target and 16_5unit.
• DC steering (x4) and BPM (x4) will be installed in this summer
shutdown.
• It could be help to cure e+ beam loss and e- beam emittance growth.
Target: e+ W target
FC_15: flux concentrator
SC: screen monitor
AC: accelerating structure
SP: BPM
SL: solenoid
BM: bend
PX: horizontal pulsed steering
PY: vertical pulsed steering

SY, BPMSX, BPM

2020/6/21

SX, BPM

13

No BPM and steering magnet

e+ source setup
Positron target and capture section

DC solenoid
Large aperture S-band acc. Structures (x10)

W target + flux concentrator (FC)
14Y. Enomoto, SuperKEKB review, 2019

e+ bunch charge trend
LIiBM:SP_16_5_1:ISNGL:KBP:10S
LIiBM:SP_28_4_1:ISNGL:KBP:10S
LIiBM:SP_58_4_1:ISNGL:KBP:10S

3(from e+ target)(before LTR)
(linac end)

e+ bunch charge (nC)

2.5

FC off

2
1.5
1
0.5/0
1/0
720
20/0
1/0
1/062020152020/05/0
1/042020/0
1/032020/01/0220
20

2020/6/21

20

20/01/0102020

LERinjection
beamstatus• Bunch charge– Stable and enough bunch charge in this stage– Primary e-: 11 nC (from gun), 9 nC (on W target), e+ : 1.2 nC (linac end), 0.8 nC (BT)• Flux concentrator (FC)– Previous FC was damaged by large discharge during PhaseII. It was removed in
Sept. 2018.
– Current FC was installed in Jan. 2019.
– 2 ～ 3 kA operation current (design 12 kA) for stable operation. no significant
fault.
Requirements for material of the FC head are• Good brazing characteristic• High yield strength even after brazing• High electric and thermal conductivity– New FC made of Cu-alloy (NC50: Cu-Si-Ni) has been tested w/o fault (～ 12 kA).
– New FC will be installed in summer shutdown of 2020 for aiming at design
operation current.
2020/6/21

16

After large discharge…
After large discharge

Slit gap got narrow.
Not possible to apply
high voltage unless thegap will be expanded.
Y. Enomoto, SuperKEKB review, 201917

FC assembly, base summary
Phase 1

Phase 2Phase 32019
autumn2020
spring2020
autumn2021
winter～deliveryremovalPresent status（2020/6）

Assembly 1

Before2015

2017/3TunnelAssembly 2

2016/3

Beam line

Assembly 3

2017/11

Test bench

FC base 1

before 2015

Trial productFC base 2

before 2015

Trial productFC base 3

before 2015

FC base 4

2017/3

Assembly 1

2018/9Tunnel2020/9Beam line

remarkFC base 5

2016/7

FC base 6

2017/11

Reserved

FC base 7*

2019/10Finished longterm test

FC base 8**

2020/5

Under test

Final version
modifiedFC base 9**2021/3

Under design

Final version
spare••*Base 7, 8, 9 (head : Cu → NC50, return yoke : SS400 → permendur)
18**Base 8, 9 Shape optimization (insulation, leakage magneticfield)

red： operation
blue： spare
black： test bench

Hardening(Toyama)

Y. EnomotoTest result of new FC: 2020/1 – 2020/6

Replace FC base 7 => 8During long term test, no trouble (discharge and vacuum pressure problem)
FC base 7 test: ～ May 2020
FC base 8 test: June 2020 ～19Y. Enomoto

e+ beam emittance• e+ beam emittance in linac and BT1 are smaller than current goal.
• Emittance growth at BT2 in both directions.
• Beam based alignment in BT line is now in progress.

150DR

３5BT1Horizontal

BT2DR

３5BT1BT2

VerticalLinac

2020/6/2120Feedback loops (1)• Beam energy feedback (J-ARC, LTR, ECS, BT)– J-ARC (e-, e+)– DR (e+)– Linac end– BT (e-, e+)• Energy stability at BT line < 0.025%
Energy FB
ee+Beam energy deviation (%)

0.100

0.075

0.050

0.025

0.000
00:00

2105:00

10:00

15:00

HH:mm

20:00

Feedback loops (2)• Beam orbit feedback– J-ARC (e-, e+)– e+ target upstream (e-, e+)– Sector2 (e-)– Sector3-5 (e-)– Linac end, BT end (e-, e+)Sector3-5 FB ONx, y position (Sector3-5)
2020/6/21

22

Feedback loops (3)• RF phase feedback has been newly implemented.
• Quick recover from tunnel work (after maintenance ortrouble recovery)

Klystron ON
RF phase of acc. Structure(Sector1)

After linac maintenance
FB ON

FB ON
Cooling water temperatureof acc. structure(Sector1)

23

Abnormal injection beam
could cause MR abort– Abnormal beam orbit• Pulsed magnet misfire (Sector3-Sector5)– Abnormal beam energy• Klystron down
• RF phase trip
• RF pulse shortening (klystron discharge)

2020/6/21

24

Pulsed magnet misfire events
Pulsed magnet
misfire, here

'ACC-PM-PC-8', '2020/03/25 11:09:33’,
50138, 'KBP', 'KBE', 'NIM',
PF/PX/PY/PD_36[8]_4

Beam orbit log viewer

Beam abort caused by pulsed magnet misfire• 49 events in 2020a, 2020b.

HER
LER

# of aborts caused bypulsed magnet misfire

54
32
10
2/28

3/13

3/27
Date

4/6-6/12

6/19

Pulsed magnet misfire events

400
350300250
200
150
100MMdd

27

6/13

6/6

5/30

5/23

5/16

5/9

5/2

4/25

4/18

4/11

4/4

3/28

3/21

3/14

50
0

2020/6/21

ee+

3/7

# of pulsed magnet misfire• ～ 100 misfire/day in Feb./Mar. (16 controllers)• Main control software and event receiver driver were replacedby improved one (Apr. 9th～). # of misfire events decreased toalmost zero.
• Misfire appears again (Jun. 10th 22:30～16th 3:23 ).
network trouble?

(*) including all misfire events(even no beam)Beam abort caused by injection beam w/ abnormal energyJun., 2019 21:19 LER D6V2 LM abort
Beam energy was 50 MeV lower than nominal condition
Dispersive point

Straight line

Horizontal position (mm)Vertical position (mm)Bunch charge (nC)The klystron 51 was down at the time.
The estimation was -46.5 MeV which isconsistent with the beam position.
28

Abnormal energy beam
- Collimator at ECS of linac end • Klystron down or rf phase trip could cause energy change.
• In the case of e+ beam, ECS (in linac end) can correct it to a certain
extent. Beam can go through BT and into MR.
• To prevent such beam, collimator will be installed in this summer
maintenance.

2020/6/21

29

Y. Okayasu

• RF gun

Summary and plan

– no significant fault– Laser cleaning can cure degradation of Qe.
– Bunch charge feedback works fine.
– Laser position feedback will be implemented.
– Diffractive optical element (DOE) will be installed fortransverse laser beam shaping (flat top).

• Flux concentrator

30– no significant fault– New flux concentrator will be installed for higher e+ bunchcharge for higher e+ bunch charge.
– Steering magnet and BPM will be installed inside solenoid
section.

Summary and plan (cont’d)• Beam abort caused by bad quality beam (orbit, energy)– Pulsed magnet misfire (orbit)• Control software have been improved.

– Install collimator at ECS (linac end) in this summer shutdown.

• Feedback loops– Orbit feedback Sector2, Sector3-5 work fine.
– RF phase feedback in many stations work well.

• Vertical pulsed bends and chambers will be replaced new one
for 50 Hz operation of thermionic e- gun (LER, PF, PF-AR).
• Beam base alignment at BT line is now in progress.

31

Backup

2020/6/21

32

Linac Beam Parameters for KEKB/SuperKEKB
Stage

KEKB (final)

Beame+e–e+e–e+

Energy3.5 GeV

8.0 GeV

4.0 GeV

7.0 GeVStored current

1.6 A

1.1 A

1.0 A

Life time(min.)

150

200

100

primary e- 10

Bunch charge
(nC)

Norm.
Emittance

Phase-I

Phase-II

Phase-III (interim)

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––––

66

primary e- 8

primary e- 10

1→1

1

0.5

1

310

1000

130(gbe) (mmrad)

42→

200/401400

2→ 0.4

4

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

Energy spread

0.13%

0.13%

0.50%

0.50%

0.16%

0.10%

0.16%

0.10%

0.16%

0.07%

Bunch / Pulse

222222

2222

Repetition rate

50 Hz

25 Hz

25 Hz

Simultaneous
top-upinjection(PPM)

3 rings(LER, HER, PF)

No top-up

Partially

2020/6/21

33

50 Hz

50 Hz

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

Beam emittance example(~1 nC) w/ multiple wire scanners
e- emittance growth
Be+: ex/ey ～100/2 mm

A

1.1 GeV

1.5 GeV eC

e+: ex/ey ～100/6 mm

12DR

345

BT
#1 straighte+: ex,y ～ 2500 mm (before DR)e-: ex,y ～20 mm

e-: ex,y ～15 mm
34

e-: ex,y ～ 50～80 mm
e-: ex,y ～ 50～80 mm

Pulse to pulse
e-/e+ beam switching• Pulsed steering magnet control e- beam orbit．
• Low emittance e- beam goes through a hole at center ofbeam line.
W target (F4 mm)

35

hole (F2 mm)
for low emittance e- beam

Qe of photocathode (Ir7Ce2, Ir2Ce)

M. Yoshida

2020/6/2136

Simultaneous beam operation (w/ thermionic and rf e- gun)• Stable simultaneous top up injection to 4 storage rings (HER, LER,PF, and PF-AR) w/ thermionic gun, rf gun, pulsed magnets.
Hor. orbit
Ver. orbit

Bunch charge
rf gunThermionic gun and damping ringHor. orbit
Ver. orbit
Bunch charge

Thermionic gun
37

Thermionic gunPrevious software structure
In some events, LabVIEW/EPICS IOC communication is delayed or failed.

Windws8.1 Pro.

mrfioc2

user mode
LabVIEW
Control application coreSet magnet
current

EPICS IOCCAclient

kernel mode
device driver for
EVR-230

PXI-EVR-230

device driver for
ADC/DAC

H/W

MagnetPower supply

PXI ADC/DAC
Trig.

New software structure (Apr. 9 ～)• NI VISA based EVR driver (w/o EPICS IOC for EVR control) (H. Saotome)• Most part of control core (LabVIEW) was rewritten (Y. Enomoto)

Windws8.1 Pro.

New driver

rewrittenLabVIEW
Control application coreuser mode
Set magnet
current

EPICS IOCCAclient

kernel mode
NI VISAPXI-EVR-230

device driver for
ADC/DAC

H/WMagnet
Power supply

PXI ADC/DAC
Trig.

Measured emittancee+ beam (Phase3.2(6.Nov.2019))

gex[mm]gey[mm]DR

35

BT1 BT2

DR35

BT1 BT2

e- beam (Phase3.2(4.Dec.2019))

e+e-gex [mm]

150

100

gey [mm]3040

sd [%]

0.16(1s)0.1(1s)Emittances increase• DR → Sector3• BT1 → BT2
Beam study will be continued

Emittances increase• C→Sector3• BT1→BT2

gey[mm]gex[mm]Phase3.3

Beam study will be continued
BC

３5 BT1 BT2

N. Iida, 31. Jan., 2020

BC

３5 BT1 BT240

Dispersion measurement and correction
J-ARC

Designchicane• Horizontal dispersion leakage from J-ARC
causes the beam position jitter.
• Applying fudge factors to quads in J-ARC,dispersion is well corrected.

After correction

Before correction
Measured

Disp. correction
w/ quads

41

Y. Seimiya

Injection efficiency and background

Vertical emittance vs. HER Injection efficiency

Y. Ohnishi

42Injection efficiency and background・LERgex[mm]gey[mm]DR

35

BT1 BT2DR35

BT1 BT2e+ horizontal emittance has been improved after ECS bendalignment.

Y. Ohnishi

Reducing emittance is in time for by*=1mm(6/Nov/2019)(28/Jun/2019)43

2020/6/21
N. Iida, SuperKEKB workshop, 201944

PF injector

KEKB

Tristan

2020/6/21

SuperKEKB

45

Monitors• Beam position monitor (x 103)
– Four strip line electrodes (x 97)• Measurement precision ~ 10 mm– Eight strip line electrodes (x 6) (J-ARC, LTR x2, PF BT, HER BT, LER BT)• Profile monitor (x 104)
– Al2O3/CrO3 (AF995R, Demarquest Co.). (t: 1 mm, 0.1 mm), YAG:Ce (t: 0.1 mm)• Wire scanner (WS) (x 6)– SectorA, B, C, 2, 3, 5

• Streak camera (ST) (x 2)•– SectorA, C, 3
RF monitors for klystron, SLED, acc. structure
STWS

WS46

STWS
WS

WS
ST

WS

Pulsed magnet system• Pulsed quads (x 28) (w/ ceramic duct) and steering (x 36) were installed at Sector3 toSector5 in 2017 (on movable girder).
• Pulsed bend, additional quad and steering were installed in 2018 summer and wintershutdown.
• PXIe based control system (Windows 8.1, LabVIEW, EPICS) have worked fine w/oany serious trouble.
• Power supply stability: 0.01% (24 hours)
Pulsed magnet
BPM

47

Movable girder for pulsed magnet(remote controllable, 10 mm step)

e+ source setup 2
FC head + BC + target = FC assembly
LAS (large aperture S-band)

BC (bridge coil)targetFC(flux concentrator) head48

solenoid

Y. Enomoto, SuperKEKB review, 2019

Movable girder for accelerating structure• Six movable girders have been installed in Sector3 (in summer
shutdown of 2019).
– Four 2-m-long accelerating structures are mounted on one girder.

• It could help to suppress emittance growth due to misalignment.