SuperKEKB recent status
andnear- (until 2022b) and long-term
operation plan
Y. Suetsugu
KEK Acc. Div.

• Details of long-term plan will be reported by Tobiyama-san.
• Beam injection issues will be covered by Iida-san.
• Collimator and TMCI issues will be covered by Ishibashi-san.
2021/3/1

BPAC

1

Contents• Recent status• Near-term (~2022b run) operation plan
• Long-term operation plan

2021/3/1

BPAC

2

Contents• Recent status• Brief review of MR in 2020c run• Preparation for 2021a run• Present status (2021a run)

• Near-term (until 2022b) operation plan
• Long-term operation plan

2021/3/1

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3

Brief review of MR in 2020c run• SuperKEKB is continuing the physics run (Phase-3 operation) while struggling to
improve the performance.
• 2020c run started on 19th Oct. and ended on 18th Dec., as scheduled.
Run summary of Phase-3 (2019〜)

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BPAC

2020c

4

Brief review of MR in 2020c run• In summary, the 2020c run was very challenging one.
• The operation condition has been far from that in 2020b run.
• Imax(LER) = 690 mA (27th Nov.), Imax(HER) = 600 mA (24th Nov) during vacuum scrubbing.
• Max. peak luminosity was 1.48E34 cm-2s-1 (14th Nov.).
• Min. βy* was 1.0 mm.

• Various challenges and limitations were revealed.
2020c run summary (2020/10/19~2020/12/18)

2021/3/1

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5

Brief review of MR in 2020c run• Initial shift plan
• 60 days (120 shifts) in total.

• Actual shifts• Most of day and swing shifts of weekdays were consumed to beam studies and tunings.

Y. Ohnishi
2021/3/1

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6

Brief review of MR in 2020c run• Statistics• Lots of time were consumed to beam studies and tunings.

• The operation statistics was accidentally similar to that of 2019c run, which wasdedicated to the machine tuning.
Need to increase machine availability for physics run as much as possible.
Please check the detailed run summary reports in “2020c Summary for Belle II”
meeting. (https://kds.kek.jp/event/36742/)

Y. Ohnishi
2019c was dedicated tothe machine tuning.
2021/3/1

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7

Brief review of MR in 2020c run• Achieved luminosities and other major parameters
Int. L [fb-1] (Delivered)Lp [x1034 cm-2s-1]

Min. βy* [mm]From 2019c run

~4.2

1.0

~1/3
~1.5

0.6

Max. I [A]

(

*

~100

Beam dose [Ah]

βy*

~740
~2/3
~500

 Original Plan Result until
2020c

~110

Plan

~1729
~1577

Lp

Int. L

Imax

Beam
dose

0.6 ~4.2E34 ~110 ~740 ~1720

Result 1.0 ~1.5E34 ~100 ~500 ~1580*Note: in the plan, the ratio of LER/HER beam currents are
assumed to be 3.6/2.6, i.e., the ratio of the design currents.

2021/3/1(Geometric mean)

BPAC

8

Brief review of MR in 2020c run• Main causes of the low luminosity• Lower beam currents than expected (~500 mA < ~740 mA)• Low injection efficiency• Unstable beams from BT and Linac• Time change (periodical change and drift) of beam orbits, energy spreads• Frequent break downs of RF-gun cavity• Low injection efficiency on HER (not “explosion” although still large)• Low physical aperture at injection points?
• Short lifetime due to small physical and/or dynamic aperture in the ring
• High background (especially background by injected beam)• Sometimes depended on optics.
• Beam-size blow-up due to beam instability caused by collimator impedance in LER• Beam-size oscillation and/or blow-up due to beam-beam effect at high bunch currents• Hardware troubles -> limit max. beam currents.
• Beam collimator, Cooling water system• Larger βy* than expected (1.0 mm at most > 0.6 mm)• Little time to try the low βy*. Even the condition of βy* = 1 mm has not been resumed.

• As a result, integrated luminosity was also lower than expected.
2021/3/1

BPAC

9

Brief review of MR in 2020c run• Major challenges in 2020c run• Internal leak in a SC cavity of HER• Poor injection efficiency (through 2020c)• Many reasons, such as mis-setting of magnet parameters in BT, frequent break-down of RF-gun
cavity, time change (oscillation and drift) of BT/Linac orbit and energy, narrow physical or
dynamic aperture of the rings, beam instability, and so on.

• Difficulty in squeezing HER βy* to 1 mm
• High background by injected beams• Damage of D02V1 collimator jaw, and exchange work (~1 week break)• Big air leak from D02V1 collimator flange• Difficulty in resuming the LER/HER condition after the collimator trouble• High background by injected beam with new steering-magnet settings• TMCI in LER due to impedance of collimators• Strong excitation of TMCI with new phase-adjusted LER Optics• Vertical beam size oscillation and blow-up in HER due to beam-beam effect• Failure in cooling water pump
See run summaries reports in “2020c Summary for Belle II”• Etc.
meeting. (https://kds.kek.jp/event/36742/)• Some were solved, but some were not and to be studied further.
2021/3/1

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10

Preparation for 2021a run• Main hardware work during 2021 winter shutdown for 2021a run• Replacement of D11D SC cavity to a reserve (HER)• The completion inspection and the issuance of completion certificate as a high-pressure gas
device from the government agency, is expected in around mid of Feb.

• Replacement of D06V1 collimator jaws (LER)• From 60 mm carbon to 5 mm tantalum• Reduction in the impedance is expected.

• Replacement of D09V3 collimator jaws (HER)• KEKB type titanium jaw.

• Replacement of D12V1 collimator drive mechanism (HER)• More precise positioning is expected.

• In situ baking of D02V1 and D06V1 collimators (LER)• Reduction in the base pressure is expected.

• Application of injection-veto modules to LM signals near collimators not to stop collimator
and/or injection tunings• Installation of a collimator in the Linac electron line (BTe SY3)
• Replacement of aged 66 kV high-voltage power supply lines [by Facility Department]• Other maintenance works• Repairs of aged power supplies for magnets, etc.
2021/3/1

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11

Preparation for 2021a run• Other improvements for 2021a run• Upgrade the backet-selection system to offer a degree of freedom in a choice of injection
buckets.
• Enables tow-pulse operation at DR• Prepare an interlock system in case of cooling water trouble for vacuum system.
• Combined interlock with colling-water flow-meters and vacuum pressures.

• Prepare an alarm system which indicates a possibility of collimator damage.
• Combined alarm with pressure bursts and VXD signals.

• Prepare a software to restore, check, and compare various setting parameters in BT (suchas magnet settings) before starting run.
• Discussion has started together with Belle II staff.

• Lessons not to follow the same rut• Do not forget beginner’s mind even if it is a familiar work.
• Use tooling as specified, for example.

• Do not drastically change parameters at once, such as beam optics parameters.
• Change them step by step while checking.
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Present status• 2021a run• The 2021a run has started on 16th Feb, 2021.
• The first week was used for various studies, tunings and vacuum scrubbing of LER, andalso for beam tunings of electron/positron beam transport lines.
• A big progress was already made on the stable two-bunch injection in LER.

• HER started from 24th Feb. after finishing cooling down and RF aging of super-conducting
cavities (SCCs). (one troubled SCC was exchanged during the winter shutdown)• The collision tuning will start from 26th Feb., with βy*=2 mm.
• The physics run with βy*= 1 mm will start from 1st Mar.
2021a run summary (2021/2/16~2/25)

2021/3/1

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13

Contents• Recent status• Near-term (~2022b run) operation plan
• Schedule• Goal• Strategy• Run plan
• Luminosity profile• Long-term operation plan

2021/3/1

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Schedule• Operation schedule• 2021a run will end on 31st Mar.
• Total operation period will be ~6.4 months in FY2020, thanks to the support from our director.

• The process for the FY2021 budget request is ongoing. The followings are present plan.
• 2021b run will start on 1st Apr. and end on 5th July. [Fixed]• 2021c run will start in the mid of Oct. and end around late Dec..
• 2022a run will start in Feb. and end at the end of Mar..
• Total operation period will be ~7 months in FY2021.
• 2022b run will start on 1st Apr. and end in the middle of Jul..
• Total operation period will be at most ~3.5 months in FY2022.

• The PXD exchange work (LS1) will start from July, 2022.  See Ushiroda-san’s talk.
• Here we roughly divide the runs to two phases: “2021a, b, c” and “2022a, b”
2020
4

FY2020Present plan (20th Oct.)

2021
5

6

7

8

9

10

11

12

4

4/1

FY2022~2M~1.4M ~6.4M/y
2022

5

6

7

8

9

10

12

2021/3/1

~3.5M

1

2

7/5

6

10/19

~2.2M

10

11

12/23

8

9

12

1

Total

~1.7M ~7.0M/y

2/9

2023
7

3
2022a

2021c

2022
5

11

2

3
Total

2022b

Plan (not fixed)

Total

~3M

~3.1M
4

3
2021a

2021b

Plan (not fixed)

2

2020c

2021
FY20211

2020bLS1 (PXD exchange)
7/15

BPAC

~3.5M/y15

Goal• Goal for 2021a, b, c runs
• Put priority on the luminosity production.
• Produce new physical results from enough data, over 400 fb-1 at least by the end of year.
• For ref., the final integrated luminosity of BaBar is 424.2 fb-1 @Υ(4s). (NIM A726 (2013) 203)

 Realize stable operation at a high luminosity.

• Goal for 2022a, b runs
• Shift focus onto the machine study and tuning anticipating luminosity boost after the LS1.
• Gain a greater understanding of this difficult machine.
• Get more information for making a decision of middle-upgrade of IR planned around 2026 (seeLong-term plan)• Accumulate more luminosity before the LS1.
2020
4

FY2020Present plan (20th Oct.)

2021
5

6

7

8

9

10

11

12

4

4/1

FY2022~2M~1.4M ~6.4M/y
2022

5

6

7

8

9

10

12

2021/3/1

~3.5M

1

2

7/5

6

10/19

~2.2M

10

11

12/23

8

9

12

1

Total

~1.7M ~7.0M/y

2/9

2023
7

3
2022a

2021c

2022
5

11

2

3
Total

2022b

Plan (not fixed)

Total

~3M

~3.1M
4

3
2021a

2021b

Plan (not fixed)

2

2020c

2021
FY20211

2020bLS1 (PXD exchange)
7/15

BPAC

~3.5M/y16

Strategy• Operation strategy for 2021a, b, c runs (1)• Operation strategy until 2020b run• Squeeze βy* and increase luminosity with moderate total beam currents within the limited
background level, and then accumulate the data.
• Suppress the increase in background resulting from βy* squeezing by adding or closing collimators.
• Generally successful until 2020b• Achieved the world-record luminosity with moderate beam currents in 2020b at βy* = 1 mm.

• 2020c run followed the strategy• Planned to squeeze βy* down to ~0.6 mm and improve luminosity further.
• Add D03V1 collimator• However, lots of challenges were standing in the way before squeezing βy* down toless than 1 mm.
• High background and low injection efficiency (unstable conditions of injection beam).
• Strong beam instabilities (TMCI) due to high impedance of collimators• Strong beam-beam effects at high bunch currents, etc.
• The situation would be worse if βy* is squeezed further in this condition.

Revise the strategy to achieve the goal of 2021a, b, c runs, throughdiscussion with Belle II.
2021/3/1

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17

Strategy• Operation strategy for 2021a, b, c runs (2)• Revised operation strategy for 2021a, b, c runs
• Aim at stable operation• Remove the high-impedance carbon collimator to avoid beam instability.  Done.
• Use the proven optics with βy* of 1 mm.
• Increase the total beam current by increasing the number of bunches and run within amoderate bunch current.
• Establish stable injection condition (essential).

• Put priority on (Int.) luminosity rather than background.
• Relax the background limit, for example, the TOP hit rate, which has been sometimes a major
limit of increasing the total beam current.
• Open collimators within the tolerable range, which could increase injection efficiency anddecrease the impedance• Increase machine availability for physics run as much as possible.
• For example, move on physics run as soon as possible after the maintenance even though
the possible βy* is 2 mm in the day.

• Continue the effort to understand various issues of the machine for the future asnecessary.
• Obtain experience at high current operation, too.

 2021a, b, c runs are very important in predicting the future2021/3/1

BPAC

18

Strategy• Operation strategy for 2022a, b runs
• Although the strategy will depend on the results until 2021c run, main time will beoffered to deeply understand the machine through beam studies, and to get more
information for making a decision of middle-upgrade of IR planned around 2026.
• More aggressive studies than 2021 runs will be tried, such as• βy* squeezing• High bunch current studies• Other machine studies will be continued, such as• Background• Physical and dynamic apertures• Injection efficiency and stability• Beam-beam effects (beam size blow-up, oscillation)• Beam instability (TMCI) and impedance• Chromatic coupling around IP• Beam loss and damage of collimators• Optics measurement and corrections, and so on• Physics run in parallel with machine studies to make good use of the spare time.
• Actually, a certain period of physics run is required to check and evaluate the results ofbeam studies.
2021/3/1

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Run plan• Basic run plan for 2021a, b, c runs
1. Resume the ring condition at βy*= 1 mm, which was realized in 2020b run.

• The starting point. Peak luminosity of ~2.4E34 cm-2s-1 at ~700 mA, 978 bunches.
• It will take one month (by the end of March)?
• Establish stable beam injection condition.
• Use the proven optics, which had been used when the maximum luminosity was recorded in
2020b (reduction of background by D03V1 will not be expected.)2.

Gradually increase beam currents at βy* = 1 mm with 1565
bunches.
• TOP could relax the limit on the background from 1.2 to 3 MHz/PMT,
which allows to increase total beam currents.
• Considering the possibility of replacing PMT in 2026.
• 3 MHz/PMT, for example, corresponds to LER = 1.3~1.4 A.

• The number of bunches might be increased step by step,
depending on the machine condition.

3.
4.

Adiabatic beam tuning• Study on Rotatable sextupole magnets
Option: Squeeze βy* down to 0.8 mm (and more)• If possible and if there is any indication to raise luminosity.
• Note: We will not stop challenging lower βy* for the future.
2021/3/1

BPAC

K. Kojima

20

Run plan• Basic run plan for 2022a, b runs
• The run plan will also strongly depend on the results until 2021c run.
• The details will be finalized seeing the progress.
• Basically, main part of shifts will be offered to the machine studies and tunings.
• Similar to 2019c run.

• Shifts at midnight, week ends, and holidays will be basically served as physics run.
• Physics runs with higher beam currents and also lower βy* will be tried.

2021/3/1

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21

Luminosity profile• The luminosity profile was re-evaluated based on the results of 2020c and following
the operation strategy until 2022b run• Assumptions for re-evaluating luminosity projection for 2021a, b, c runs
• Beam current  Key point• Considering the results of 2020c run, it seems reasonable to assume that the beam current willbe ~1.1 A, although the TOP limit is relaxed.

• Specific luminosity• Same level to 2020b run• Expected to be improved gradually by ~10%?

• Others• The “efficiency factor” used for the calculation of Int.
luminosity, is 0.65, based on the results so far andanticipating a stable operation.
• Physics run for 28 days per month basically.
• Move to 1565 bunches from 4/1.
• The Int. luminosity includes that during the off-resonance run. (~1 week?)• Reduction in dP/dI ~ 60% at 6000 Ah.
• No long-term break

Y. Funakoshi• No trouble in collimators and other hardware (~1 week break in the case) -> ~10 fb-1 loss

• No intervene by COVID-19
2021/3/1

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Luminosity profile• Assumptions for evaluating luminosity projection for 2022a, b runs
• Beam current• Beam current will be increased gradually up to 1.6 A.

• βy*• Keep 1 mm
• But will be squeezed further if we have chance.

• Specific luminosity• Same level to 2020b run• Others

2021/3/1• The “efficiency factor” is assumed to be 0.4, considering that the run is mainly served forthe machine studies while assuming physics runs of 28 days per month basically.
• Number of bunches will be kept to1565, but will be changed depending on the machine condition.
• Reduction in dP/dI ~ 40% at 10000 Ah.
• The Int. luminosity includes that during the off-resonance run.
• No long-term break• No trouble in collimators and other hardware• No intervene by COVID-19• No physics run at 10.750GeV etc. (to be discussed)• It will take approximately 3 weeks at least considering the preparation, physics run, andrestoration time.
BPAC
23

Luminosity profile• Luminosities• Run strategy 2021a, b, c runs: Put priority on (Int.) luminosity rather than background.
• Run strategy for 2022a, b runs: Shift focus onto the machine study and tuning.

FY2020

FY2021

Lp [x1034 cm-2s-1]

Max. I [A]

βy* [mm]
FY2022

FY2020

FY2021~1.6

FY2022

FY2020

FY2021

Int. L [fb-1] (Delivered)

FY2022

FY2020

FY2021

FY2022

~730

~1.2
~1.1

~410
~280

LS1

LS1

LS1

βy*

Lp [E34]

Int. L [/fb]~2021b

1.0

~3.8

~280

~1.1

~2021c

1.0

~4.8

~410

~1.2

~2022b

1.0

~8.0

~730

~1.6

• Key point to realize the plan
• How much can we store the beam currents?
• Can we keep the injection condition stable?
• Can we control beam instability and beambeam effect at high bunch currents?
2021/3/1

BPAC

LS1

Imax
1.5~2 fb-1/day

24

Contents• Recent status• Near-term (~2022b run) operation plan
• Long-term operation plan
• MEXT roadmap 2020
• Current situation

2021/3/1

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25

MEXT Roadmap 2020
• For MEXT Roadmap 2020, we proposed to update the previous long-term operation
plan (2019) considering the actual situation and the results obtained until 2019c.
Operation plan proposed for MEXT 2020 Roadmap

2021/3/1

BPAC• Peak luminosity ~6E35 cm-2s-1 in ~2028• Integrated luminosity 50 ab-1 in ~2030 (40 ab-1
in ~2029)• PXD exchange in 2021~2022• Partial RF-power upgrade (2 stations) in 2026
• IR (QCS and its beam pipes etc.) upgrade in2026• βy*=0.3 mm in 2026 after IR upgrade, and ~0.5mm before that• Max. beam currents: LER 2.8 A, HER 2.0 A(1761 bunches) in 2027
• Basically, 8 moths’ operation per year.
[Investment in equipment]• QCS and its beam pipes etc.
• Partial RF-power upgrade (2 stations)• Beam collimator upgrade• Linac upgrade• Belle II upgrade

26

MEXT Roadmap 2020
• Key point : Intermediate upgrade of IR around 2026
• Relocation of magnets: Make it possible to squeeze βy* to 0.3 mm, mitigate the beambeam effect in the high bunch-current region• Enlargement of QCS beam pipes: Protect QCS, and reduce the background.
Long-term Operation plan••

Improvement of• Background• Beam lifetime• Collision efficiency

Intermediate
remodeling of IR(QCS, Belle, RF

Remodeling of Linac

Boost up of luminosity
βy* : ~0.5  ~0.3 mm
Lpeak : ~3E35  ~6E35 cm-2s-1

Partial replacementof detectors• Until the upgrade, βy* will be
gradually squeezed, and thebeam currents will be increased
gradually.
2021/3/1

βy* [mm] BPAC

1.0

0.6

0.5

0.3

27

Current situation• Current situation• The MEXT updated their roadmap 2020 in August, 2020.
• The SuperKEKB/Belle II project was selected as one of 15 highest priority projects
with an “AA” grade (the highest grade).
• The plan was assessed by the external review committees (BPAC, 2020/6 andAccelerator Review Committee (ARC, 2020/7)).
• Based on the recommendation from the review committees, “Long-term operation
plan meeting” was launched in August, 2020.
• Five times meeting have been held so far, and various subjects were discussed and investigated.
• Some practical conclusion should be obtained in these two or three years, i.e., before thedecision of whether the IR have to be upgraded or not around 2026.

• Will be reported by Tobiyama-san• The actual long-term plan will be revised and finalized seeing the progress of thecurrent luminosity improvement.
2021/3/1

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28

Summaries• SuperKEKB is continuing physics run (Phase-3)• 2020c run was very challenging one, and various challenges and limitations were revealed,
although they were beneficial for the future operation.

• Near-term operation plan was revised and proposed based on the results in 2020c run.
• The long shutdown (LS1) was postponed until summer, 2022.
• Put priority on the luminosity rather than the background and aim at a stable operation for2021a, b, c runs.
• Shift focus onto the machine study and tuning for 2022a,b runs, anticipating luminosity
boost after the LS1.
• The goal int. luminosity is around 700 fb-1 by the end of 2022b, before the LS1.

• The present long-term operation plan follows that in the MEXT Roadmap 2020.
• Various ideas and measures are under discussion in the “long-term operation plan meeting”,
and also other regular meetings.
• Some practical conclusion should be obtained in these two or three years, i.e., before thedecision of whether the IR have to be upgraded or not around 2026.
• The actual operation plan will be revised and finalized seeing the progress of the current
luminosity improvement.

2021/3/1

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Thank you for your attention

2021/3/1

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Backup

2021/3/1

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31

Luminosity profile for 2021 runs
• The luminosity profile was re-evaluated based on the results of 2020c and following
the strategy for 2021 runs.
• Assumptions for revaluating luminosity projection -1• Beam current  Key point
Improvement factors

Higher risk ofcollimator damage
and QCS quench

Remove carbon
collimator

Relax BG limit
Vacuumscrubbing(not so drastic)

Anxiety factors~1.6A
Wider collimator
gap

Higher total beam
currents with large
number of bunches
Lower bunch
currents for the same
total current
Relax beam-beameffect2021/3/1

Lower impedanceWider physicalapertureLong
lifetime
Improve injection
efficiency~1.5 A

Relax TMCI limit~1mA/bunch ~ 1.5 A

Frequent Belle aborts

Strong beam-beam effectat high currents• Beam-size blow up• Bema-size oscillation• To be studied

Longer dead time

No experience over 1 A

Injection beam
Stable 2 bunch inj. at~25Hz?

Stable high injection
efficiency?

• Considering these, it will be reasonable to assume thatthe beam current should be increased gradually, andthe maximum beam current with 1565 bunches is1.1~1.2 A (0.7~0.8 mA/bunch) for 2021a and b runs.
BPAC

32

Luminosity profile for 2021 runs
• Assumptions for revaluating luminosity projection -2• Specific luminosity

Y. Funakoshi• Same level to 2020b run• Expected to be improved gradually by ~10%?

• Others• The luminosity used for the calculation of Int.
Luminosity is 0.65 times of the peak luminosity,
which has been assumed to be 0.7 so far.
• Low reproducibility after run break• More tuning time will be required at high currents• Aging run before physics run, for example• But, no Linac study after maintenance day• Start physics run from night of the day• Physics run for 28 days per month basically. But,
• First week after starting run has no physics run (4 days physics run between 2/16〜2/28.)• Move to 1565 bunches from 4/1.

• The Int. luminosity includes that during the off-resonance run.
• ~1 week?

• Reduction in dP/dI ~ 60% at 6000 Ah.
• No long-term break• No trouble in collimators and other hardware (~1 week break in the case)2021/3/1• No intervene by COVID-19

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33

Long-term operation planPrevious plan (Revised based on the results until Phase-2) (2019)
Peak luminosity 8E35 cm-2s-1 in ~2026
Integrated luminosity 50 ab-1 in ~2028
by*= 0.3 mm in 2021
PXD exchange in 2021~2022
RF full upgrade (4 stations) in 2024
Max. beam currents: LER 3.6 A, HER 2.6
A (2500 bunches) in 2026
• Basically, 8 moths’ operation per year.
•
•
•
•
•
•

[Investment in equipment]• Full-scale RF-power upgrade (add 4
stations)• Beam collimator upgrade• Linac upgrade• Belle II upgrade
2021/3/1

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34

Long-term operation plan
Original plan (~2018)• Peak luminosity 8E35 cm-2s-1 in ~2025• Integrated luminosity 50 ab-1 in ~2027• PXD exchange in 2020~2021• RF full upgrade (4 stations) in ~2023• Max. beam currents: LER 3.6 A, HER
2.6 A (2500 bunches)• Basically, 8 moths’ operation per year.
Investment in equipment• Full-scale RF-power upgrade (4stations)• Beam collimator upgrade• Linac upgrade• Belle II upgrade
2021/3/1

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35

2021 and long-term operation plans• Comparison of luminosity profiles in the revised 2021 plan and the long-term plan
Min. βy* [mm](1565)
(978)

(978)

Int. L [fb-1] (Delivered)Lp [x1034 cm-2s-1](978)(1565)(978)

Lpx0.65 (2021a~) (978)From 2019c(1565)(978)

From 2019c run

Max. I [A]
(978)

(

Beam dose [Ah](1565)
(978)

(978)

Lsp x βy* [E31 mA2]

 Long-term
Plan Revised
2021 Plan(base)
 Result until
2020c(1565)(978)
Result in 2020b

Note: Constant Lp
was assumed
even for ib+*ib- >0.6 [mA2]

2021/3/1

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36

2021 and long-term operation plans• The revised luminosity
profile for near-term
operation is far from that forthe present long-term one.

From 2019c run
• The peak and Int.
luminosities at the end of2021 are almost a half or
one third of original plan.

• Main Reasons:• Larger βy*2021/3/1

• Similar total beam current,
but lower bunch current.

BPAC

Long-term Plan
Revised 2021 Plan(base)
Result until 2020c• The specific luminosities
are almost the same.

37

2021 and long-term operation plans• What to do tocatch up with thelong-term plan

• What to be improved
IssuesBackground(Storage)

Squeeze βy*

Increase total
beam current

Increasebunch current

Background(inj.)

2021/3/1

Vacuumpressure

~2021

2022~

2026~

Vacuum scrubbing (not so drastic)
QCS beam pipe remodeling

Physical
aperture (QCS)

Add shielding

Collimator(Phys. aperture,
Impedance

Relocation, Optics optimization
Remodeling (low impedance, robust)

Beam lifetime
Dynamic
apertureBeamInstability
Beam size
blowup

Improve Spe.
Luminosity

Causes• How to improve (some possible measures)

Inj. efficiency(rate, stability)

Rotatable Sx, Perfect match

QCS remodeling?

Beam-beameffectUnderstanding of the mechanism (Chromatic coupling)?
Improvement in optics measurement and correction

Inj. quality(emittance,stability)

Understanding the reasons of low efficiency (especially on HER)FB system in BT and Linac (orbit, energy)

Inj. Charge(2unch Inj.)

Establishment of stable 2 bunch injection
Stable operation of RF gun

BPAC

38

Long-term operation plan
• BPAC Report (2020/6)• Based on the experience in operating SuperKEKB, the machine team has
been developing ideas that could achieve the physics goal of the Belle IIexperiment with lower consumption of electricity . The committee
understands that such an operation scenario over the next ten years waspresented in the KEK submission to the MEXT Roadmap selection
process, and finds this development timely and very attractive.
Implementing such a plan requires an upgrade of the machine anddetector. The BPAC strongly encourages a close collaboration between
SuperKEKB and Belle II to further explore various ideas and conduct thenecessary research and development work. Implementation of thenecessary upgrade should then follow after positive evaluation oftechnical designs by the relevant committees. The BPAC is looking
forward to hearing the progress in future meetings and strongly hopes fora positive outcome from the MEXT Roadmap selection.

2021/3/1

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39

Long-term operation plan
• KEKB Review Report (Long-term plan part) -1 (2020/7)• R7.2: Over the next year or so, perform beam measurements todetermine if the proposed QCS upgrades with larger apertures are
absolutely required to get to the design luminosity or, e.g., to half thedesign luminosity.
• R7.6: Determine which technical studies (essential beam studies and
QCS coil parameter studies) need to be carried out now, before adecision can be made, within about 2 years, on starting construction of
new QCS quadrupoles.
• R7.7: Determine the technical staffing and accelerator experts needed toconstruct the required hardware upgrades and examine if new technicalstaff will need to be trained or hired to design and execute these
upgrades.
• R7.9: Present a detailed SuperKEKB upgrade plan with underlying
reasoning and data at the next ARC meeting.
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Long-term operation plan
• KEKB Review Report (Long-term plan part) -2 (2020/7)• R7.8: Evaluate a backup plan to simply increase the luminosity with theexisting hardware to about 2-3x1035 cm-2s-1 (with small upgrades but
without major upgrades and the associated long installation downtimes
and serious recommissioning) and then integrate luminosity for about 1012 years at 7-8 months per year to obtain an integrated luminosity of 50
ab-1 by 2032-2034.
• Detailed long-term upgrade plans should be finally decided once full
performance with those upgrades is predicted within a quantitative
performance model. This makes sure that the long-term quadrupole
aperture is chosen wide enough, background sources and paths areunderstood, lower beam lifetime can be handled, impedance stays undercontrol, and the collimator system is adequate.

2021/3/1

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41

Long-term operation plan meeting• Four meetings have been held so far (~2021/2/4)• The first meeting on 2020/8/21• The process so far [Y. Suetsugu]• Present status of QCS update project [N. Ohuchi]• Future plan of this meeting [H. Koiso, Chair]• The second meeting on 2020/9/3• Summary of the first meeting [H. Koiso]• Examination status of the optics for QCS upgrade [A. Morita]• Crab waist, dynamic aperture and beam lifetime [K. Oide]• The third meeting on 2020/9/26• Effect of IR Model V-20-20A (large physical aperture in QC1) on the beam optics [H.
Sugimoto]• Examination of QC0P (Permanent magnet) [A. Morita]• Luminosity and lifetime (update) [K. Oide]• Effect of the enlarged physical aperture in QC1P on MDI mechanical design andbackground [H. Nakayama]• On flange at the top of QCS cryostat [N. Ohuchi]• Dependence of the injection efficiencyBPAC
on βy* [Y. Funakoshi]
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42

Long-term operation plan meeting• The fourth meeting on 2021/1/22• Progress report on QCS of upgrade project [N. Ohuchi]• LER dynamic aperture and luminosity (update) [K. Oide]• Status, issues and future plan of BT and Linac from the view point of beamcommissioning [N. Iida]• Middle and long-term outlook on injection efficiency and luminosity [Y. Funakoshi]• The fifth meeting on 2021/2/17 (planned)• Long-term strategy of BT [M. Tawada]• Long-term strategy of Linac [K. Furukawa]• Long-term strategy of beam collimators [T. Ishibashi and S. Terui]• We have been also discussing about IR upgrade on other meetings, such as IRtechnical meeting (hosted by N. Ohuchi) and MDI meeting (hosted by H.
Nakayama).

2021/3/1

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2021/3/1

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