Operation Status ofSuperKEKB
B2GM
2022-01-24
Takuya Ishibashi
on behalf of SuperKEKB accelerator groupTable of Contents• Summary of 2021c run• Future plans (2022ab, LS1)
• Activities of International Task Force (ITF)2

Summary of 2021c run[Y. Ohnishi]• We had been able to operate with 1 A in the beam current of LER stably.
3• We broke the luminosity record.

History of 2021c run[Y. Ohnishi]• Oct. 19th – Oct. 27th
Ø Vacuum scrubbing and machine study for βy*=8 mm.
• Oct. 28th – Oct. 31stØ Injection kicker accidental firings in LER. The beam current
in LER had been limited to 200 mA or less.
• Nov. 1st – Nov. 10th
Ø QCS quench due to earthquakeØ Injection kicker accidental firings in LER. Thyratrons
replacement work on Nov. 8th.
• Nov. 11th – Nov. 29th
Ø Energy scan: 10.657, 10.706, 10.751, 10.810 GeV
Ø Thyratron replacement work on Nov. 24th.
• Nov. 30th – Nov. 8th
Ø Increasing beam currents up to 800 mA/640 mA (LER/HER).
• Nov. 9th – Dec. 19th
Ø Mini energy scan on Dec. 1. Changed +4 MeV.
Ø QCS quench due to a human error on Dec. 6th
Ø Increasing beam currents up to 1020 mA/820 mA (LER/HER,
number of bunch: 1370).

(We made a protocol of the baking run at the
beginning of 2021c and it looks like it worked.)• Dec. 10th – Dec. 23th
Ø Machine studies

4History of the luminosity

2019ab

2019c[Y. Ohnishi]

2021ab2020ab

2021c

2020c

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Operation Statistics for three years•

βy* squeezing from 2 mm to 1 mm while
taking steps of 1.5 mm and 1.2 mm••

Crab waist
βy* squeezing from 1 mm to 0.8 mm[Y. Ohnishi]•••

Many optics trials
Carbon jaw in D06V1 in LER
Replaced damaged jaws of D02V1• The time to tune the machine increased because of theenergy scans.
• No vertical collimator was damaged during 2021c.
ü Actually, this is the first time it didn’t break during a run period.

••

βy* = 1 mm
Replaced damaged jaws of D02V1•

βy* = 1 mm

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Specific Luminosity

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Status of Sub-systems – RF system[K. Watanabe et al.]• There had been no detuned stations, and they had been able to keep the total
cavity voltage for 1020 mA in LER and 820 mA in HER.
• ARES cavity• Averaged trip ratio = 0.7 times/cavity/90 days
• D05-A cavity: Added a digital camera during summer shutdown to observe abnormal
emission, and this emission has been observed when the break downs occur frequently.
• D04-A: Abnormal emissions with pressure rises had occurred, so we decreased the cavity
voltage temporally. After that, the emissions hadn’t occurred, so we set it the default
value on Dec. 8th.

• LLRF (Low Level RF)• A master oscillator for DR broke and was replaced on Dec. 2nd.
• Beam aborts by μ=-1 mode excitations in HER on Nov. 5th and Dec. 8th.

• High Power RF• Number of beam aborts caused by the high power systems: total 22• Crowbar: 10 times, microwave transmission circuits: 11, steam cooling system: 1, infrastructure: 1
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Status of Sub-systems – Magnet system
QCS• power supply[S. Nakamura et al.]• Minor failure on the digital feedback system.

• Quench• Caused by earthquake on 2021-11-01 06:14. After that, a threshold of the quench detectors has increased.
• Caused by mis-operation for the cryogenic system on 2021-12-06 17:07.
• There was no quench derived from beam loss.

Normal conducting• power supply• Communication failure in D09. Inserted a hub in the middle of the ARCNET chain.
• Major failure on a small size power supply named ZVQLY2RE_1. A circuit board broke, and we were not able toinject the beam. It was replaced immediately.
• Minor failure issued by cooling fans on a small size power supply named ZVQR3OLE.
• Oscillation phenomenon in small size power supplies manufactured by a maker.
• Operation of a synchronous setting system has started [A. Morita].

• magnets• No operation stop due to the troubles by the magnets.
• A downward trend of flow rate in HER-QA type magnets.
• Operation of rotatable sextuple magnets has started to suppress the chromatic coupling. We have been able torotate them with holding the beam in the ring.

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Status of Sub-systems – Magnet system• Suppression of synchro-beta resonance by changing the rotation angle of the rotatable sextuple magnets.
• The degradation of the linear optics by this change is small.
• We can rotate with holding the beam.
• ΔR1’ = -1 has been adopted.

[Y. Ohnishi]

10Status of Sub-systems – Vacuum system• Beam dose during 2021c (HER: 553.1 Ah, LER: 678.4 Ah)[K. Shibata et al.]• Troubles• D06H3 collimator was damaged by the accidental firings of the injection kickers in LER. →We replaced themwith new ones during this shutdown.
• A chiller, which was used for the QCS beam-pipes and so on, on IR D02 side stopped twice by the overload on
Nov. 13th and Dec. 14th. → We have plans to install an additional chiller on IR D02 side during this shutdown.
• An abnormal pressure rise at an arc section in LER D04 (CCG D04_L09D, L10). The cause is still unknown, but
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the pressure has decreased and kept the lower level (~2×10-8 Pa).

Status of Injection[N. Iida et al.]

• Injection efficiency in HER has been improved from 60% to 80% in maximum for βy*=1 mm.

• The horizontal orbit from the septum magnets to the injection point has been closer to the design orbit.
• A BPM named “injection-BPM” to monitor the injection beam has been started to use in the operations andvery useful for the injection tunings.

• Beam clearance in the injection beam channel is very tight.

→We have plans to widen an aperture of the injection beam channel at the injection point during LS1 (Long
Shutdown-1), and this could improve the injection efficiency further.

• Emittance blow-ups in the beam transport lines have still occurred.

• The horizontal emittance blowups may be caused by radiation excitation and CSR (Coherent Synchrotron
Radiation). Some simulation works are on going in order to understand this.

[Y. Funakoshi][M. Kikuchi]

12Impedance Issues in LER• The Σβyky on this study (βy*=1 mm) is almost same as that on Oct. 26th (βy*=8 mm), however the tune shift on thisstudy in βy*=1 mm is somehow larger.
• During this study, we had opened apertures of some vertical collimators to reduce the Σβyky by ~20%, but themeasured tune shift didn’t change much.
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Impedance Issues in LER

Assuming σz = 6 mm
Σβyky on Dec. 22nd

βy* = 1 mm

Narrow setting [V/C] Wide setting [V/C]βy [m]

βy ky,D [V/C]βy ky,Q [V/C]

QCSR

402.765.96e15

9.91e10v. collimator

3.41e162.62e16

QCSL

431.745.43e15

4.54e10

QCS + v. collimator

4.65e+16

3.80e16

Measured

4.86e16

4.47e16βy* = 8 mm

Σβyky on Oct. 26th
βy [m]

βy ky,D [V/C]βy ky,Q [V/C]

[V/C]

QCSR

49.73

7.36e14

1.22e10v. collimator

3.47e16

QCSL

49.89

6.71e145.60e10

QCS + v. collimator

3.55e+16

Measured

3.48e+16• The Σβyky becomes comparable between the calculated and measured one by adding the wake in QCS beam-pipes.
• However, there is still a discrepancy between them when we opened the apertures on Dec. 22nd.
ü Note: The βy in the QCS beam-pipes is averaged value between QC1LP515 and QC2LP2475 or QC2RP2715 and
QC1RP485.
• The detail was presented on the MDI parallel session on Jan. 20th (https://kds.kek.jp/event/40691/).
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Future plans (2022ab)• Scenario to increase beam currents [Y. Ohnishi, Y. Funakoshi].

• We’re going to gradually increase the total beam currents with increasing the number of bunches and keeping
the bunch current.
• At some point, we’re going to squeeze the βy* to 0.8 mm.
• Periodic machine studies are planed (once a month, for example).

βy*=0.8 mm:

5.44×1034

8.16×1034

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Future plans (2022ab)[Y. Ohnishi, 2021c summary meeting]16

Maintenance works during winter shutdown
Damage of D06_H3 collimator heads• Replacement of LER D06H3 collimator jaws.
• The jaws were found to be heavily damaged bysteered abnormal beam due to accidental firings ofinjection kickers.

• Exchange of screen monitors in beam transport lines• Some alumina-fluorescence-type screen monitors were
exchanged 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
dummy loads 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

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Leakage of vacuum insulation tank of QCSR
Pressure during heating at QCSR

July, 2021

[N. Ohuchi]

Dec., 2021

• QCS refrigerator stopped on Dec. 24th, 2021.
• The increase of vacuum pressure (peak value)in the insulation tank was almost the same tothat after 2021b.
• July, 2021: The existing vacuum pump had
driven.
• Summer shutdown: a turbo molecular pump
was added and directly connected to the tank.
• Dec, 2021:The existing pump was stopped
during the heating, and only an additional
pump had driven.
→This may indicate that the leak rate getslarger because the effective pumping speed of
the additional pump is higher than that of theexisting one.
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Future plans (LS1)• A biggest task planned in LS1 is Non Linear Collimator (NLC) at LER OHO straight section.
• NLC could fully work instead of D06V1 collimator and reduce the impedance by opening the aperture of
D06V1.
• However, the impedance around IR could be dominant with squeezing the βy*.
• On the other hand, there are some mitigation schemes that we‘ve found, which are BxB FB, chromaticity,tune and so on, to suppress the vertical beam size blow-up.
• We need to discuss carefully whether NLC is really needed.
Scheme of NLC

Collimator Location[K. Oide]βy and aperture of vertical collimators

NLC

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Activities of International Task Force (ITF)• Optics sub-group (A. Morita, H. Koiso)• 3rd meeting on 2021-11-17 (https://kds.kek.jp/event/40129/)
Ø Dynamic Aperture in the Low Energy Ring of SuperKEKB, Yunhai Cai• Beam-beam sub-group (D. Zhou, K. Ohmi)• 6th meeting will be hold on 2022-01-25 4:30pm JST (https://kds.kek.jp/event/40786/)
Ø Preliminary Simulation Study with 'realistic' Crab Sextupoles, Yuan Zhang
Ø Analysis of beam-beam instability with longitudinal impedance for SuperKEKB, Chuntao LinØ Updates on beam-beam simulations and results of recent beam-beam machine study, Demin ZHOU

• 5th meeting on 2021-12-15 4:30pm JST (https://kds.kek.jp/event/40470/)

Ø Beam-beam performance in the presence of lattice resonances in SuperKEKB, Kazuhito Ohmi
Ø Analysis of coherent beam-beam instability, Chuntao Lin
and so on• TMCI sub-group (M. Migiliorati, T. Ishibashi)• 5th meeting will be hold on 2022-01-27 5pm JST (https://kds.kek.jp/event/40778/)
Ø Machine study report, Takuya Ishibashi
and so on• 4th meeting on 2021-12-16

Ø ECHO3D and its application, Igor Zagorodnov
Ø Computation of the impedance of collimators in the LHC, Mounet Nicolasand so on• Linac sub-group (M. Sato, S. Matsumoto)• Organization is in progress.

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Activities of ITF• Anyone can join the group-mail-list by sending an email to {group-name}request AT ml.post.kek.jp with a subject of “subscribe”• Mailing list of the sub-groups
Øskb-itf-bb AT ml.post.kek.jp: for Beam-beam
Øskb-itf-opt AT ml.post.kek.jp: for Optics
Øskb-itf-tmci AT ml.post.kek.jp: for TMCIØskb-itf-linac AT ml.post.kek.jp: for Injector Linac

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Thank you for your attention.

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backup23

Specific Luminosity[Y. Ohnishi](HBC: High Bunch Current study)

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Future plans (2022ab)• Attainable luminosity scaled from high bunch current study [Y. Funakoshi].
LER

HER

LER

HER

LER

HER

# of
bunches

392+1

1564+12345+1

Luminosity

1.49 x 1034 cm-2s-1

5.94 x 1034 cm-2s-1

8.91 x 1034 cm-2s-1

I_total0.4349 A 0.2694 A

1.73A

2.60 AI_bunch1.11mA

0.685mA

scaling

1.07 A

1.61 Aby*=0.8mm

sx *
sy*

0.225µm 0.256µm

nx
ny
xy

0.03940.03647.43 x 1034 cm-2s-1
Ib(LER) x Ib(HER) = 0.758mA2
Ratio = 1.61 =0.92 x (7/4)

1 x 1035 cm-2s-1

1mm/0.8mm = 1.25
1mm/0.6mm = 1.67
8.91 /0.8 = 11.1
5.94/0.6 = 9.9
As beam currents increase, optimum current ratio seems to approach the inverse of beamenergy ratio.

25[Y. Suetsugu]

2022a and b run plan
• 2022a run will start from 21st, February, 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)• by* squeezing down to 0.8 mm, and 0.6 mm if
possible.
• 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 current ratio.
• Note: For some studies, we will perform them inproper timing during physics run, and needsome period (~one week?) to see the effect of
the settings on the luminosity.

2021a,b 2021c

2021a,b 2021c

2022a,b2022a,bTarget

1mm -> 0.8 mm
in 2021b?
~5E34
1 mm

Base

0.8 mm𝐼!𝐼"
2021a,b 2021c
2022a,bTarget2021a,b 2021c
Target2022a,bBase~1.4 A

Base~490 /fb26

[Y. Suetsugu]

FY2022 operation plan

• Budget• KEK requested the operation budget to MEXT expecting approximately 6 months operation for
FY2022, based on an electric-power unit price at that time (anticipating some increase in theprice, of course).
• The budget assessed by MEXT was found to be somewhat low, and was enable approximately
4.8 months operation with the assumed unit price.
• However, as you know, the unit price has been rising abnormally, and further shorter operation
time is forecasted now.

• Operation plan
• Case study: if we assume a unit price at this March (no increase after that)• If the unit price continue to increase, the situation will get worse.
H alf a year delay (2022/1/11)
2022

2023

4

With 2022c

2022b

0 Yen/kWh/M
Without 2022c

1.0M(1.5 months)

5

6

7

8

9

10

11

12

1

2

2022c
4/30

QCSR L. T.

2022b

2.7M

10/16

1.5M 11/30

3
T otalLS1¤ 2.5M /y
T otal
¤ 2.7M /y

6/20

2022c

≤ 3 months!

• We are now under negotiation with KEK to find the best plan.
• Discussion on the FY2022 operation plan will be necessary including the start time of LS1(before May).
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