SuperKEKB LS1 upgrade status (including injector)

Hiroyasu EGO
KEK Injector Linac division

BPAC Feb. 19, 2023

1

Contents• Operation of SuperKEKB in 2022
• Countermeasures for high luminosity in LS1• Upgrade works

Main rings / Injector linac• Summary
BPAC Feb. 19, 2023

2

Operation of SuperKEKB in 2022
Achievements

Lp = 4.65 x 1034 cm-1s-1
L = 424 fb-1

I [mA]

Inj.
effH [%]

Ip = 1.46 A
Ie = 1.14 A

Qe [nC]QCS BW135[mRad/s]

Improvements

Inj.
effL [%]① e-: The septa in operation at 25Hz
② e+: Fast strip-line kicker for the 2nd

Qp [nC]bunch orbit correction③ HER: Horizontal orbit feedback system

QCS FW135[mRad/s]

To be improved④ e-: Give-up of two-bunch injection due to
2nd bunch drift of the vertical orbit⑤ e+ Decrease in charge due to the BP
diamond aborts

N. IidaBPAC Feb. 19, 2023

3

Countermeasuresagainstchallenges
Countermeasures for highluminosity
in LS1
Y. Suetsugu (2021.09.02)
The 25th KEKB Accelerator Review Committee
K. Shibata
The 26th KEKB Accelerator Review Committee

During LS1
Done before LS1
Under consideration(It was found that it is not easy.)

Under consideration
During LS1
Done before LS1
Under consideration
During LS1
During LS1 (Partially)
During LS1 (Partially)
During LS1 (Partially)

14th Dec. 2022

The 26th KEKB Accelerator Review Committee

BPAC Feb. 19, 2023

44

Oho straight section (D05)

D04
D05

We are here now

5

6

JFY2022782022b run

2023
9

10

11

RF cavity
inspection
Crane not available
Ceiling aseismic reinforcing work

Concreteshield removal

12

1

JFY2023

5

6

7

8

3

RF cavity replacement

2024
9

10

11

12

1

2

3

NLC construction
New radiation shield
Concrete shield
installation
reinstallation

14th Dec. 2022

2

NLC construction

2023
4

Positronbeam

We are here now!!

2022
4

Oho
traight section

concrete radiation shields• NLC construction (LER)
LS1 works of the main rings : Schedule• RF cavity replacement (LER)• Ceiling aseismic reinforcing work
S. Nakamura• Installation of new radiation shields

The 26th KEKB Accelerator Review Committee

2023c run

2024a run13
K. Shibata
The 26th KEKB Accelerator Review Committee

BPAC Feb. 19, 2023

5✔︎✔︎✔︎✔︎IR (Tsukuba straight section) #1
LS1 works of the main rings : IR

QCS movable platform

Belle II

• Major work items in accelerator tunnel:• Disassembly and reinstallation of concreteradiation shields• Belle II maintenance & reinforcement work
• Disassembly and reinstallation of magnets, beam
pipes for QCS work
• QCS extraction & reinstallation• QCSR cryostat leak test
• QCS cryostat modification

IR

QCS cryostat

Concrete radiation shield

We are here now!!

2022
5

6

7

PositronbeamElectronbeam

IR (Tsukuba straight section)
4

Tsukuba lab.

8

2023
9

10

11

12

1

2

3

We are here now

JFY2022

Concrete shield disassembly

2022b run

QCS cryostat
modification

QCS extraction
QCSR cryostat leak test

Belle II work

Belle II maintenance & reinforcement

2023
4

5

6

JFY2023

7

8

QCS reinstallation
Magnet & beam pipe disassembly
Belle II
maintenance & reinforcement

14th Dec. 2022

2024
9

10

11

12

1

2

3

Concrete shield reinstallation

Belle II work

The 26th KEKB Accelerator Review Committee

BPAC Feb. 19, 2023

2023c run

2024a run
K. Shibata
The 26th KEKB Accelerator Review
6 Committee
6LS1 works of the main rings : HER injection point

Major vacuum works during LS1 #4• Vacuum work at HER injection
section:• 3 beam pipes are replaced withnew ones to increase injectionrate.
• Orbit clearance from chamber wall isenlarged by changing wall position
along beam axis.
• Wall length along the beam axis is
shorten as much as possible.

M. Kikuchi

wall
too smallclearance
New wallY. Suetsugu• Pumping port will be removed toshorten wall length if possible.

• New BPM for injected beam is installed
for precise injection tuning.

• Schedule• Production : JFY2022 (∼ March/2023)• Beam pipe replacement : JFY2023(April/2023 ∼)13th Dec. 2022

The 26th KEKB Accelerator Review Committee

BPAC Feb. 19, 2023

25
K. Shibata
The 26th KEKB Accelerator Review Committee

7LS1 worksof the mainrings : #3
NLC
Ohostraight
sectionTsukuba (Belle II)• Wiggler magnets and beam pipe removal (already done)• Removed wiggler magnet and cable : 50 magnets and their cables
Double pole magnet (3 ton) : 20
Single pole magnet (2 ton) : 10
Half pole magnet (1.5 ton) : 20
Cables : 3 ton

D04
D05

• Removed beam pipe for wiggler magnet : 10 beam pipes• Disassembly procedure
•
•
•
•
•

Removal of wiggler magnet cables
Upper parts of wiggler magnets disassembly
Beam pipes removal
Upper parts of wiggler magnets reassembly
Wiggler magnets removal

Ohostraight section

•
•
•
•

Positronbeam

10 times

S. Nakamura

Wiggler beam pipe removal work
14th Dec. 2022

The 26th KEKB Accelerator Review Committee

BPAC Feb. 19, 2023

K. Shibata
15 Committee
The 26th KEKB Accelerator Review

8LS1 works of the main rings : Others

Others major works (excluding Linac)
T. Ishibashi• Robust collimator head (LER)• As countermeasure against kicker-pulser misfiring and resulting
destruction of collimator
•

MR

•
•
•

Carbon collimator head

Replacement with carbon head of horizontal collimator D06H3 and relocationfrom D06H1 to D06H4
Carbon head production : ∼ March 2023
Head replacement : Spring ∼ Summer 2023
Collimator relocation : Spring ∼ Summer 2023

• New beam pipes with wider aperture at HER injection point• For injection efficiency improvement••••

Y. Suetsugu

Beam pipe at
HER injection point

New beam pipes with wider aperture & New BPM for precise measurement of
injected beam
Beam pipe production : ∼ March 2023
Beam pipe replacement : Spring ∼ Summer 2023
Septum baking : ∼ Summer 2023?

• RF cavity modification and replacement (LER)• For stable operation with larger beam current

DR

•
•

Modification : Input coupler replacement, cooling power enhancement, coaxial
line modification, etc. (done)
Cavity replacement (D05A) : January ∼ February 2023

• Vacuum seal replacement at RF section (DR)• For pressure reduction•

Replacement from elastomer gasket to metal gasket for dummy pipes (done)• DR Extraction kicker power supply modification and repair (DR)• For stable operation•

DR Ext. kicker
14th Dec. 2022

DR RF section

Modification : December 2022 ∼ August 2023

• And so on…

The 26th KEKB Accelerator Review Committee

BPAC Feb. 19, 2023

K. Shibata
The 26th KEKB Accelerator Review
18 Committee
9

✔︎

✔︎

LINAC upgrades : Schedule
2018

2019

2020

2021

2022

2023

2024

2025

New S-band structure①

４prototypes

tests & installation
12 structures

Design

New pulse compressor②

Designprototypereal #1 & installation
real #2
Large-aperture pulsed Q magnet③④

DesignFabrication

Installation

High-speed pulsed kicker
DesignPrototypeInstallation

More fabrication
BTe-ECS

Design
RF Source⑤

Structures and waveguides
Structures and waveguides
Installation
Other instruments
Air conditioners renewal⑥

Automatic beam tuning

LINAC has no LS1 because of injection to SR rings !
BPAC Feb. 19, 2023

LS1
10

LINAC upgrades : Difficulty in stabilizing beam condition

Best tuning condition is destroyed gradually in a day
2022.5.29 8:42:42

Beam orbit and emittance of etuned ne in the morning

Beam orbit unstable and emittance worse
charge lost in the afternoon
BPAC Feb. 19, 2023fi

2022.5.29 13:18:53

11

Upgrade works : Difficulty in stabilizing beam condition
Best tuning condition destroyed by change in air temperature arising from seasonal and daily conditions
UPGRADE : Renewal of air conditioners for the klystron gallery and linac tunnel（2022 - 2023）

32

Air temperature [deg.C]

Normalized emi ance [μm]・εx ・εyY. Shimosaki

tt

12

30

28

26
5/1

5/13

5/25

6/2

6/14
2022

6/26

7/8

LINAC upgrades : Beam tuning
PY_R0_01

PY_A1_M

Orbit adjustment

Manual adjustment of magnets upstream and accelerating phase of
the sectors 3 to 5 by using beam-destructive pro le monitor
UPGRADE : Automatic adjustment by using none-destructive monitor (2022-2025)

tilt tuning

Energy spread adjustment

Improved injection ef ciency
RF_3φ

PY_R0_63

RF_4φ

RF_5φ

Screen monitor in BT

Screen monitor in BT

Tuned beam

Tilted and spread beamfifi

BPAC Feb. 19, 2023

13

LINAC Upgrades : Beam-degrading areas
J-arc
BT

In exible optics
for matching of ebeams

Unstable beam in BT
by bare longitudinalemittance, selfinduced SR and so on

e+ capture

Suitable focus for e+ beam but weak focus for e- beam

Horizontal orbit

Vertical orbit

ChargeBeam position in LINAC and BT to HERfl

BPAC Feb. 19, 2023

14

LINAC upgrades : Beam optics 1
Large-aperture pulsed Q magnet & High-speed pulse kicker

e- beam orbit

Bmag Y

Y. Seimiya

Four Q magnets

面
Bmag X

High-speed pulse kicker

c
i
t
p
o
e
n
Fi

a
m
s

g
n
i
h
c
t

Four Q magnets

Matching simulation

Y. Okayasu

C. Mitsuda, Y. Enomoto• At the entrance and exit of 180 deg. J-ARC region,a good optics matching is very important to mitigate beam loss andemittance growth.
• Simultaneous matching for both of HER and LER injection beams
requires the pulsed Q magnets.
• From the simulation results, four pulsed Q magnets at both of entrance
and exit of J-ARC are sufficient for the matching.
• Pulsed kicker with a speed of about 100 ns has been demonstrated tocontrol the vertical orbit of 2nd bunch independently.

K. Yokoyama, T. Natsui

Large-aperture pulse Q-magnet

BPAC Feb. 19, 2023

15

Linac upgrades : Beam optics 2

Pulsed Quads at J-ARC Pulsed
for e- lowbetaatoptics(cont’d)
Quads
J-ARC
for e- low beta optics (cont’d)Upgrade during LS1

Upgrade during LS1

ly these four pulsed
quadsonly
are optimized
the ebeam,
betatronfor the e- beam, the betatron• Afterthese four forpulsedquads
aretheoptimized
can be decreased. function can be decreased.
Four Large-aperture pulsed Q magnets
on result shows that
it
can
help
to
decreasetheemittance
less
than
half.
• Simulation result shows that it can help to decrease the emittance less than half.
Current optics

New optics

Δγε𝑥 ~ 100 um, 𝛽𝑥 = 45.2 m••

End of LAS cavity
Start of S-band
cavity••Bunch tail is kicked back byquad, and temporally
emittance is reduced.

e+ target

Δγε𝑥
~ 40
𝛽𝑥 m
= 16.3 mΔγε𝑥 ~ 100um,
𝛽𝑥 um,= 45.2Δγε𝑥 ~ 40 um, 𝛽𝑥 = 16.3 m• Large emittance e+• The four pulsed Q magnets

End of LAS cavity
Start of S-band
cavitybeam is accelerated from
0.1 GeV to 1.1 GeV for
DR injection.
Bunch tail is kicked back bytemporally
O p anderation of DC Q
• quad,emittance is reduced.
achieved
smaller for-magnetsis optimized
e+ betatronbeam. function• For e- beam (3 to 4
GeV), the focusing force
is so weak as to cause
its emittance growth.

Sector2 end e+ target
e+ targetachieved smaller
betatron function

Sector2
end end e+ target
Sector2•

can optimize both the eand e+ beams, thebetatron functions can be
decreased.
Simulations shows thatthey can help to decrease
the emittance growth toless than half.

Sector2 end

BPAC Feb. 19, 202313-14,
Before optimization
After
optimization
BeforeDec.
optimization
KEKB Accelerator Review Committee,
13-14, 2022
optimization
Y.2022
Seimiya 30
KEKB Accelerator Review Committee, Dec.After

Y. Seimiya 30

16Linac upgrades : Injection efficiency
BTe-ECS (Energy Compression System)

ECS reduces the longitudinal emittance of electron beams for HER
Simulations for best operating parameters

Installation plan in BTeby the beam-analysis group

Injection ef ciency

2Jz of injection beam

M. Yoshida
HER limit

N. Iida, T. Yoshimoto
S-band 3m-long TW structures• Design of the components have finished.
• High-power RF sources are under construction.
• Component layout are in the process of design.
• 3m-long TW accelerating structures ready for high-power conditioning

Results:• Longitudinal emittance, 2Jz, becomes small by ECS.
• Even with R56 = - 0.6 m Vc = 70 MV, 2Jz can be lower than the energy
acceptance of HER.
• Investigation with a parameter of R56 = -1.0 m will be done soon.

fi

BPAC Feb. 19, 2023

17

Linac upgrades : Accelerating structures
New S-band structure

New pulse compressor

Success in beam acceleration !

Discharged damages

New S-band 2m-long TW accelerating structure

Success in pulse compression !

Super-compact pulse compressor• Mitigation of accelerating structure failures• Originally designed for 8 MeV/m (PF injector), but used at 20 MeV/m (KEKB upgrade)• Degradation that lead to high field emission rate and discharges• Water leaks, field emission, discharge in waveguide, and so on (29 of 60 units have some problems)• Not only future Y(6S) but even Y(4S) could be suffered

Water leakages• 5-year upgrade plan to fabricate and install new accelerator structures (FY2018 – FY2022)• 4 units (16 acc. structures) will be replaced by new one. (Unit44 was replaced in this summer)• New acc. structure: acc. gain up 7%, surface field down 20% (reduce breakdown)• Suppression of instabilities arising from long-range wakefields
H. Ego• New pulse compressor (SCPC) was also developed and installed in Unit44.
BPAC Feb. 19, 2023

18

Summary• Achievements; Ie = 1.14 A, Ip = 1.46 A, Lp = 4.65 x 1034 cm-1s-1 and recorded int. L = 424 fb-1
• Fatal shortage of operation time due to incredible increase in electricity costs• Main ring upgrades in LS1••••

IR works
Non Linear Collimator (NLC) installation
Beam pipe replacement at the injection point of HER for large physical aperture
Etc• LINAC Upgrades• No LS1 because of beam injection for not only SuperKEKB but also the SR rings• Beam optics improvements by installing new large-aperture pulsed Quads at J-arc and positron capture section• Fast kicker for 2nd bunch orbit correction• New accelerating structures against deterioration over time
• Replacement of air conditioners• ECS in the electron BT• Severe difficulties in procurement for electric devices, materials and so on

BPAC Feb. 19, 2023

19

BPAC Feb. 19, 2023

20

Appendix

21

K. Shibata
The 26th KEKB Accelerator Review Committee

IR (Tsukuba straight section) #4
IR• Future works

Tsukuba lab.

• QCS cryostat modification• To reduce Belle II background noise, the material at the tip of QCS cryostat will be changed from
W to SUS.
• QCSR front cap replacement• QCSL front plate replacement• To make more space for Belle II cables, the tip of QCSR cryostat will be thinner.

Electronbeam

Positronbeam• QCSR cryostat modification including front cap replacement• QCS cryostats will be disassembled for these works.
BPM feedthroughBPM feedthrough• It is necessary to shift QCS beam pipes in longitudinal direction.
QCS beam pipe

QCS beam pipe

Y. ArimotoTo access QCS pipes & BPMs,
this part should be disassembled.

To access QCS pipes & BPMs,
these windows should be open.

T. OkiY. Arimoto
QCSR front plate
replacement

QCSL
14th Dec. 2022

QCSR front cap
replacement

QCSR

The 26th KEKB Accelerator Review Committee
22

11LINAC status : S-band Linac Layout & Energy Scheme
Simultaneous top-up beam Injector for four storage rings
60 klystron-units and 226 accelerating structures
B

A
Thermionic gun

Damping ring

PhotocathodeRF gune+ 1.1 GeV

PF: 2.5 GeV e- 0.3 nC

J-arc

e- 1.5 GeV
C

1

2

3

4

5

ECS

LER: 4 GeV e+ 4 nC x 2
HER: 7 GeV e- 4 nC x 2

e+ W-target

PF-AR: 6.5 or 5 GeV
0.3 nC
Pulse magnets

HER: 7 GeV e-・Two electron sources:
Beam energy

PF-AR: 6.5 GeV eor 5 GeV
LER: 4 GeV e+
PF: 2.5 GeV eA

B

C

1

2

3

4

RF gun: HER injection
Thermionic DC gun: LER, PF, PF-AR
・Sector 3-5: All magnets are pulsed magnets.
Continuous orbit feedback

5・DC magnet settings are same for different beam mode

Sector23

LINAC status : Electron Charge History 2020a to 2022c for HER
e- emittance
Measured εnx,ny (2 nC) : 20/20 µm (at BT1)
Goal : εnx,ny (4 nC) : 40/20 (H/V) µｍ
2020a, b2020c2021a, b2021c2022a, b

6High bunchcharge study

e- bunch charge [nC]・RF gun output

5

2022c
(LS1)

・BT

test beamreached to the design
charge of 4 nC !

4

Bunch charge
feedback

3
2
1
M. Satoh024

LINAC status : Positron Charge History 2020a to 2022c for LER
e+ emittance
Measured εnx,ny (3 nC) : 103.5/4.7 µm (at BT1)
Goal εnx,ny (4 nC) : 100/15 (H/V) µｍ
2020a, b2020c2021a, b

2021c

・after e+ target

・Solenoid current (SL_16_)optimization・before DR・beam tuning (primary e- bunch charge up)

2022a, b

2022c
(LS1)

・decrease bunch charge(MR request)

e+ bunch charge [nC]・Linac end
・BT・Steering, BPM
in Unit 1-5, 1-6
・beam tuning
・New FC
・Solenoid
focus upM. Satoh25

ARC Recommendations• R7.1: Perform systematic measurements of the orbit jitter of the two electron bunches and correlations with possible
sources. Advance the synchronous data acquisition between Linac and BT.
• R7.2: More generally, perform a feasibility study for the implementation of synchronous beam data acquisition, which
will be extremely useful for studying drift and instability.
Improve the analysis tools using the synchronous beam, rf monitor, pulsed magnet data
• R7.3: Implementation of an orbit feedback if the use of pulsed magnets allows for this.
Orbit FB with pulsed magnet is already in operation (Sectors 3-5).
• R7.4: Continue with the upgrade plan as presented in the summary slide.
In progress• R7.5: Concerning the emittance growth of the second electron bunch, study the effect of long range-wakes in the
linac.
Fast kicker for 2nd bunch orbit correction could mitigate the 2nd bunch emittance growth.
• R7.6: Identify the causes limiting the charge of the electron bunch along the injector.
Simulation work and beam study are being conducted.
• R7.7: Discover the loss locations and causes for the positron transport in the linac.
Simulation work is now in progress. Beam matching after e+ target will be tested soon to reduce the beam loss.

26