SuperKEKB Ring operation
status and plan
Makoto Tobiyama, Yusuke Suetsugu
KEK Accelerator Laboratory
＠BPAC 21/Feb/2022

1

SuperKEKB 2021c run (2021/10/19～12/23)
 Run summary of 2021c(Vacuumscrubbing)

Energy scan

10/19 – 10/27• Vacuum scrubbing and machine studies
at βy* = 8 mm
10/28 – 11/5
• Accidental firing of LER injection kicker. I< 300 mA.
11/01 – 11/10• QCS quench due to earthquake• Thyratron replacement on Nov. 8
11/11 – 11/29• Energy scan
• Thyratron replacement on Nov. 24
11/30 – 12/8
• Increasing beam currents up to 800 mA /640 mA
12/10 -12/19• Extremely large HER σy after earthquake• Mini energy scan (+4 MeV) on Dec. 1• QCS quench due to human error• Increasing beam currents up to 1020 mA/ 820 mA. nb = 1370.
12/20 – 12/23• Machine studies• Chromatic X-Y couplings, resonancestructures, TMCI, beam-beam, injection
performance, collimators, optics, etc.

2SuperKEKB 2021c run (2021/10/19～12/23)
 Major results -1•

Luminosity records•

Energy scan (11/10～11/29)•Protocol to stably and safely increase beam currents•••••••

2021a,bLuminosity: 3.81x1034 cm-2s-1 @1370 bunches.
Int. luminosity: 2.52 fb-1/day (Delivered), 2.22 fb-1/day(Recorded). ~310 fb-1 in total, which is close to the base profile.

Physics run at 10.657, 10.706, 10.751, 10.810 GeV.
Sufficient data was successfully obtained in each energy.
The protocol including “baking run” was established andalmost worked well from 12/10.
The maximum beam currents of 1020 mA in SuperKEKB era
was achieved (LER, 1370 bunches, during physics run).
No severe rapid beam loses and damages to vertical-type
collimators and detectors have happened, although the reason
is not so clear.

2021c

2021a,b2021cTarget

~3.8E34
1 mm

2021a,b2021c Target

2021c~310/fb
Base

Base

2021a,b

𝐼 𝐼
2021c
Daily max. values

Target(Baking run)Target~0.9 A

Base
Base

3

SuperKEKB 2021c run (2021/10/19～12/23)
 Major results -2•

Improvement in the injection efficiency of HER•••

•

2021c

Startup protocol was established.
Injection veto of CLAWS abort system reduces beamaborts during injection tuning (12/1~).

Start up on 12/8 maintenance day
Regular maintenanceImprovement in background•••2021bInjection efficiency improved to approximately 60 %.
Low emittance injection beam, optics matching at BT
considering the fringe-field of septum magnets,
improvement in the tuning methods, etc.

Smooth startup after maintenance work••

Injection efficiencies

Beam background was drastically reduced after themaintenance on 11/24, although the reason has notbeen so clarified.
The effect of D02_V1 collimator relocations seems tobe almost as expected (for outer detectors).

Beam studies•••by H. Nakayama

The last three days’ day and swing shifts werededicated to beam studies (βy* = 1 mm).
Various studies were done, including studies
proposed by sub-groups of ITF.
Fruitful results were obtained and reported in thesummary meeting held on 13 and 14, January.
(https://kds.kek.jp/event/40680/, sorry in Japanese)4

Slow drift of collision energy

Slide by K. Matsuoka
5

Slide by K. Matsuoka

6Beam Energy for Y(4S)

Y. OhnishiNov. 25 2021

difference between 2020 Apr. 26 and 2021 Nov. 10LERHER
Hor. steering
kick angle

Ver. steering
kick angle

δ= -5.95 x10-4

δ= -5.17 x10-4

expected

EL = 3997.620 MeV
EL = 4000.000 MeV (design)

ΔEcm : -5.9 MeV

EH = 7003.66 MeV
EH = 7007.29 MeV (design)

Energy at 2020 is not sure whether on the exact Y(4S) or not.

Sum of kick angles of horizontal dipole correctors was not kept well before 2020c.
The closed orbit correction (CCC) algorithm was improved to keep the energy.

Horizontal Steerings in LER

Y. OhnishiFeb. 3, 2021

EPICS PVs (KRB)

CCCで設定しょうとしたキック角の総和

sum of horizontal
kick angle
for each correction
at CCC(rad)sum ofhorizontal
kick angle(rad)1455 点のランダムウオーク？

CCCでは|θx|>4x10-8 radで足切りを行っている。
(~24 bit)(上のキック角を積分)/2π

Momentum
Analyzer
Referenceis 19:00, Dec. 16

水平ステアリングで、本当にエネルギーを変えてしまった？

(Sum of K0)/2π

2.24 x 10-5

2.76 x 10-5

両者の違いは、設定精度の問題?

8 In the COD correction algorithm used in SuperKEKB, in orderto maintain beam energy, the sum of the total kick angle of thehorizontal steering magnets were kept below a certain amount.
 We have found the poor convergence (10^-7) before 2020c.
After 2021a, the correction algorithm was improved to havebetter convergence (10^-18).
 The energy drift is suspected to be caused by the poorconvergence.
 Even with the current correction algorithm, slow drift of theenergy might happen. Monitoring the energy drift by Belle IIdetector and/or periodic mini-energy scan will be needed.

Slide by K. Matsuoka

9SuperKEKB 2021c run (2021/10/19～12/23)
by Y. Ohnishi

10SuperKEKB 2021c run (2021/10/19～12/23)
 Some results from beam studies -1• Rotatable sextupole magnets

by Y. Ohnishi

Rotatable Sextupole magnet

M. Masuzawa• Succeeded to suppress emittance blow-up by tuning rotation angle.
• Succeeded to rotate sextupoles with beam, although single and low beam currents.
• No need to optics correction each rotation.

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SuperKEKB 2021c run (2021/10/19～12/23)
 Some results from beam studies -2• Collimator and TMCI studies

by T. Ishibashi

by T. Ishibashi• Very interesting and informative results to the future wereobtained, although still further investigation is required.
• Please check Ishibashi-san’s report in the summary
meeting (in English). https://kds.kek.jp/event/40680/

12SuperKEKB 2021c run (2021/10/19～12/23)
 Some results from beam studies -3• High-bunch current (HBC) studies
by Y. Ohnishiby Y. Ohnishi• The decrease in the specific luminosity with bunch-current products is still observed. The cause
should be understood.
• The specific luminosity at high bunch current seems to be improved compared to that in 2021b.
• Increase in the beam-beam parameter seems to be still expected for higher bunch current.

13SuperKEKB 2021c run (2021/10/19～12/23)
 Major challenges -1•

Frequent accidental firing of LER injection kickers••

The beam currents was kept low for safety. Deterioration of 30 years’ old thyratron exchanged during summer
shutdown could be a cause. They were replaced to those that had been used until 2021b. Long-term
countermeasures are under consideration.
D06_H3 collimator head was damaged. It was replaced to new one this winter shutdown.

•Increase in the vertical beam size at high bunch current•

Bunch current limit of LER••••

Single beam: Synchro-beta resonance? Head tail or strong head-tail instability (TMCI)?
Two beam: Beam-beam effect? Chromatic x-y coupling at IP?
The cause has not been understood yet. Detailed study is on going.
Limiting factor seems not a simple TMCI due to high impedances of collimators. Other instabilities?

• Rapid beam loss and abort••••by H. Nakayama

No severe beam loss at IP and damage ofvertical-type collimators were happened in thisrun, though rapid beam losses were observed
several times. High risks for increasing beamcurrents.
The large losses were more frequent for HER.
The cause has not been clarified. Damaged
collimator head might be a reason, but it should
be studied further.
New and rapid loss monitors at collimators arebeing prepared by Belle II.

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SuperKEKB 2021c run (2021/10/19～12/23)
 Major challenges -2•

Long-term (~ weeks) drift of collision tuning knobs and betatron tunes••

Drift of magnetic fields of QCS is said to be a cause. The measurement in a test bench is on going.

Injection efficiency•••

Efficiency has greatly improved in this run especially for HER, but further improvement is requiredconsidering future increase in beam current and operation at low βy*.
Beam clearance in the injection beam channel is very tight. Expansion of the apertures is under discussion.
Quality and stability of the injection beam. Emittance blowup in the beam transport line.
Long-term drift of tunes

Small beam clearance at HER injection beam channel

by M. Kikuchi

by H. Koiso

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Maintenance works during winter shutdownDamage of D06_H3 collimator heads

Replacement of LER D06_H3 collimator heads.
•The heads was found to be heavily damaged bysteered abnormal beam due to accidental firing ofinjection kickers.

• Exchange of screen monitors in beam transport lines••

Some alumina-fluorescence-type screen monitors wereexchanged to OTR (Optical Transition Radiation)-type ones
for improving the sensitivity.

Exchange of screen monitors in BT lines

Replacement of primary transformer of DR bending magnet power
supply•The problem was found in the last summer shutdown and the rental
trance had been used since then.

•

Other usual maintenance, including periodic inspection of refrigerator
system.

•Measures against aging facilities•••

Replacement of pure water pumps for vacuum
chamber lines at Tsukuba.
• We had no spears up to now since 2021a run.
Repairment of untreated water pumps for RF dummyloads lines at Fuji.
• It was failed during 2021c run.
Roof waterproofing work at Fuji power-supply building.

Water pumps at Fuji

Water leak of MR power supply building

16

Leakage of vacuum insulation tank of QCSRby N. Ohuchi• QCS refrigerator stopped on
12/24, 2021.
• The increase of vacuum
pressure (peak value) in theinsulation tank was almost thesame to that after 2021b.
• There seems no increase in theleak rate.

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2022a and b run plan

2022a run will start from 2/21, as scheduled.
••The electricity charge is rising abnormally, as you know.
The budget is already short, but KEK will make up for it.

In 2022a and b runs, we will continue physics run aiming higher luminosity and stable datataking, in parallel with necessary beam studies for improving luminosities, for investigating
various challenges, and for finding effective upgrade plans in the future (LS1 and LS2).
• Luminosity ~5E34 cm-2s-1 (Base)• Integrated luminosity ~490 fb-1 (Base)•Assumed Operation efficiency ~0.4

• Beam currents ~1.4 A (Base)• βy* squeezing down to 0.8 mm, and 0.6 mm ifpossible.
• Try new sextupole magnet setting to improve
dynamic aperture.
• Practical use of rotatable sextupole magnets
during collision.
• Try new tune and/or chromaticity values.
• Change crab-waist ratio and beam currentratio.
• Note: For some studies, we will perform themin proper timing during physics run, and needsome period (~one week?) to see the effect of
the settings on the luminosity.

𝐼 𝐼18

 Budget••

FY2022 operation plan

Good news: the total budget increased from the last year.
Good news: the facility maintenance cost was secured in the initial budget.
• Measures against aging facilities and upgrades of Linac, MR and Belle II are possible.
• It is expected that approximately 4 billion yen will be required in the same way in the future
although whether it is approved or not is judged every year.

••

Bad news: six months operation requirement reduced to 4.8 months.
Bad news: the situation will be more severe due to the increase in the electricity unit price.

 Operation plan••••

The ratio of electric unit price around the last May to this March will be ~1.5 (operating month).
If the unit price is kept to that in March and does not increase after that, we will be able tooperate for ~3 months in FY2022.
If the unit price continue to increase after March, we will be able to operate only for ~ 2 monthsin FY2022.
Therefore, no matter when we start LS1, there is a high possibility that we will not be able tooperate 2022c run.

19Operation Plan

2021
4

FY2021

2022
567

8

910

12

FY2022

~3.2M

10/19

7/5~2.2M

FY20234

2/21 ~1.2M

12/23

567

8

910

QCSR leak check

~3.0M

1112

12Total~6.6M/y3Total

LS1 (PXD, TOP exchange)~3.0M/y

6/30

2023

To be discussed further

32023
2022b

4/1

22022a2022
412021c2021b
4/1

1120245678

LS1 (PXD, TOP exchange)

910

1112

1

2

10/1

~2.9M 12/25

32024a2023c
2/6Total~1.8M ~4.7M/y20

21

22

International Task force for SuperKEKBupgrade Members• ARC members prepared a list of possible candidates in June, 2021
• Initial members have been identified. More members who have required expertiseand strong interest are welcome.
• Should work in close collaboration with KEKB commissioning team.

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International Task Force Charges• Consider effective ideas to realize luminosity of ~6x1035 cm-2 s-1 as a result of anintermediate upgrade around 2026, which could include modifications of IR, final
focus systems, injectors, but without changing the boundary to the Belle IIdetectors.
• Find a realistic way before long shutdown 1 (LS1) scheduled to start Jul/2022 inorder to achieve luminosity of the order of 1035 cm-2 s-1 without large
modification of accelerator components.
• Consider longer-term alternative idea to achieve ~6x1035 cm-2 s-1 or more, evenby largely modifying the IR and the Belle II detector

 Four working groups (sub-groups) organized and their indicosites created••••

OpticsBeam-beam
TMCI
Linac

(contact person: Akio Morita)(contact person: Demin Zhou)(contact person: Mauro Migiliorati)(contact person: Masanori Satoh)https://kds.kek.jp/category/2242/24

International Task Force for SuperKEKB upgrade Examples of activities on the International Task Force• Share the lattice file of SuperKEKB, examined the result with independent codes.
• Successfully reproduced the result with LEGO (Y. Cai)
• Try to find better dynamic aperture• Tried new sextupole sets found using LEGO.

• Beam-beam simulation, Impedance calculation by international collaborators.
• Deep discussions on the simulation results. Proposed many machine study items.
Discussion on the results.

 Mid-term review is scheduled by the KEKB Accelerator Review
on 25th, Feb.

25

Summary 2021c runs
• New peak luminosity record and new daily integrated luminosity. Achieved baseplan of the luminosity profile (despite the difficulties coming from LER injection
kicker accidental fires).
• Energy scan (10.657, 10.706, 10.751, 10.810 GeV)
• Established the procedure to increase beam current safely. Performed physics
run over 1A of LER.
• Improved HER injection efficiency.
• Initial trial of correction of chromatic R1’ using rotatable sextupoles. Good
response have been achieved.
• A new mystery on the TMCI related ? vertical beam size blowup.
• Planned continuous study on the transverse impedance around QCS• (Frequent) Accidental fire of LER injection kicker.
• Counter measure: Double kicker system and robust beam collimator (made of carbon)26

 2022a/b run• We will continue physics run aiming higher luminosity and stable data taking, inparallel with necessary beam studies for improving luminosities, for investigating
various challenges, and for finding effective upgrade plans in the future (LS1 andLS2).
••
•
•
•
•
•

Evaluation of transverse impedance, especially around QCS.
Correction of chromatic couplings (R1’ and R2’) using rotatable sextupoles.
Betatron tune search.
Beam injection improvements, stability.
BT emittance blowup.
Squeezing of beta_y* (0.8 mm at first). Check the beam background.
Higher bunch / total beam current. etc..

 International Task Force• Very actively working with devoted international cooperation.
• Mid-term review is scheduled on 25/Feb.

27