SuperKEKB status report
Kyo Shibata(on behalf of SuperKEK Accelerator Group)2021.10.18
40th B2GM Plenary Session

Inter-University Research Institute Corporation High Energy Accelerator Research Organization (KEK)
大学共同利用機関法人 高エネルギー加速器研究機構 (KEK)Overview of 2021ab run
Luminosity record

2021ab run

Peak luminosity : 3.12×1034 cm−2s−1(2021.6.22 18:30)

Y. Ohnishi (2021.09.01)
The 25th KEKB Accelerator
Review Committee
2021/10/18

B2GM Plenary Session

2

Best day
Luminosity record

Peak luminosity : 3.12×1034 cm−2s−1(2021.6.22 18:30)

Y. Ohnishi (2021.09.01)
The 25th KEKB Accelerator
Review Committee
2021/10/18

B2GM Plenary Session

3

Operation summary
Y. Ohnishi (2021.09.01)
The 25th KEKB Accelerator Review Committee

2021/10/18

B2GM Plenary Session

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Machine parameters
Y. Ohnishi (2021.09.01)
The 25th KEKB Accelerator
Review Committee

2021/10/18

B2GM Plenary Session

5Specific luminosity (2021ab)
Y. Ohnishi (2021.09.01)
The 25th KEKB Accelerator Review Committee• Luminosity
𝐿𝐿 =𝑁𝑁+ 𝑁𝑁− 𝑛𝑛b 𝑓𝑓0∗
4𝜋𝜋𝜎𝜎x,eff
𝜀𝜀y 𝛽𝛽y∗• Specific luminosity
𝐿𝐿
𝐿𝐿sp =∝
𝐼𝐼b+ 𝐼𝐼b− 𝑛𝑛b1𝜀𝜀y 𝛽𝛽y∗𝜎𝜎y∗• Lsp depends on 1/σy*.
• Lsp doesn’t depend on Ib+Ib-.
• However, it was observed that
Lsp decreases as Ib+Ib- increases.
Beam blowup due to Beam-Beameffect at large Ib+Ib-.
2021/10/18

B2GM Plenary Session

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Projection of specific luminosity in 2021ab
Y. Ohnishi (2021.09.01)
The 25th KEKB Accelerator
Review Committee

2021/10/18

B2GM Plenary Session

7

Difficulties in increasing beam currents• It was hard to increase beam intensity.
• Beam current

𝐿𝐿 =𝑁𝑁+ 𝑁𝑁− 𝑛𝑛b 𝑓𝑓0≈ Beam current

Y. Ohnishi (2021.09.01)
The 25th KEKB Accelerator Review Committee Design values：(HER, LER) = (3.6 A, 2.6 A) @ 2500 bunches Typical beam currents during 2021b：(HER, LER) = (∼0.70 A, ∼0.84 A)@ 1174 bunches∗
4𝜋𝜋𝜎𝜎x,eff

𝜀𝜀y 𝛽𝛽y∗• Reasons why the beam currents can not be increased
 Short beam lifetime
1.

2.

Narrow dynamic aperture (DA)• Beam-beam effect reduce DA.
• Crab Waist (CW) collision scheme can suppress the
reduction of beam lifetime.
• It is necessary to optimize magnets for CW.
Narrow physical aperture• It is necessary to narrow collimators to reduce thebackground noise in Belle 2.

 Insufficient injector power•

Injector power has not yet reached the design value.

•

Low injection efficiency especially in HER.

•

Operation with high currents increases the risk of damage to
Belle2 and collimators.

 Insufficient injection tuning？

 Unexplained sudden large beam losses

2021/10/18

B2GM Plenary Session8Collimator works during summer shutdown• HER

T. Ishibashi• Upgrade of D12V4 driver unit

• Not vacuum work. For precise jaw position control.

• Damaged jaw replacement;• D09V2 : Replaced with new jaws
• D09V1 : Replaced with new jaws

• LER

• Relocation of D02V1• In order to match the betatron phase at D02V1 and QC1RP(superconducting final focusing magnet)• We will be able to open D02V1 wider and suppress TMCI.

• Damaged jaw replacement;• D06V2 :Replaced with new hybrid-type jaws
Robustness of hybrid-type jaws will be tested.
• D06V1 :Replaced with new jaws
• D06H3 : Damaged due to accidental kicker-pulser misfiring.
Since we have no spare jaws, damaged jaws were
replaced with healthy D06H1 jaws.
• D06H1 :Replaced with short-stroke jaws.
Minimum aperture is limited to ±14 mm.

2021/10/18

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Relocation of LER D02V1 collimator
T. Ishibashi (2021.09.30)
MDI taskforce meeting• Expected effect;• Due to better phase matchingwith QC1RP, D02V1 relocation
reduces IR backgrounds by∼20% and ∼50% for Touschek
and Coulomb components,
respectively.
• Physics run with wider
collimator aperture will bepossible.
• TMCI bunch current limit will be
relaxed.
• Increasing beam intensity andluminosity

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Robust hybrid-type collimator• Robust hybrid-type jaws were installed into LER D06V2.
• Conventional jaw material (High-Z)••••

Tantalum (Ta), Tungsten(W)
Short radiation length, short jaw length
Low impedance, large TMCI bunch current limit
Easily damaged• Low-Z collimator••••

Carbon (C)High melting point
Long radiation length, long jaw length
High impedance, low TMCI bunch
current limit• Hardly damaged• Limited beam current in 2020c• Robust Ta-C hybrid-type jaw

T. Ishibashi (2021.09.01)
The 25th KEKB Accelerator
Review Committee• Adopting good points of both High-Z
and Low-Z material• Thin Ta part can cut beam halo.
• Carbon base is hardly damaged.
• Low impedance, large TMCI bunch
current limit
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Injection kicker-pulser misfiring
T. Ishibashi (2021.09.30)
MDI taskforce meeting• Countermeasure;• Thyratrons for LER kickers
were replaced with theequivalents of those for HER
kickers.
• So far, HER has not had
kicker-pulser misfiring.
• LER will also have no kickerpulser misfiring in the future.

2021/10/18

B2GM Plenary Session122021c operation plan
• First half;• Machine tuning & study:••••

HER beam injection
TMCI
Beam-beam effect
LER crab waist

•
•
•
•

10.657 GeV
10.706 GeV
10.751 GeV
10.810 GeV• On-resonance run• Energy scan:• βy* squeezing:• βy* = 1mm• Second half;• On-resonance run with 1mmβy*• Machine study plan is underconsideration.
2021/10/18

Y. Ohnishi (2021.10.8)
KCG meeting
B2GM Plenary Session

132021c start-up schedule
Y. Ohnishi (2021.10.8)
KCG meeting

2021/10/18

B2GM Plenary Session

142021c start-up schedule
Y. Ohnishi (2021.10.8)
KCG meeting

2021/10/18

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Major challenges
Y. Suetsugu (2021.09.02)
The 25th KEKB Accelerator Review Committee• Upgrade to overcome thesechallenges are underconsideration now.

+ 6) Low injection efficiency especially in HER.
2021/10/18

B2GM Plenary Session

16International Task Force• KEK has assembled a powerful International Task Force to address the challenges of the upgrade.
• ITF has held three meetings so far;
• July 28 : kick-off meeting.
• Sep. 2 : Joint meeting with ARC meeting• Oct. 15 : third meeting• ITF has four subgroups at this point;• Beam-beam, optics, TMCI, Linac• Deep discussions are actively conducted byeach subgroup.
• Beam-beam subgroup meeting;• Aug 24th, Sep. 28th, Oct. 28th

• TMCI subgroup meeting;• Aug. 27th, Sep. 2nd, Oct. 1st• Optics subgroup meeting;• Sep. 22nd, Oct. 13th

• Linac subgroup• Just starting its activity• Gathering the members
2021/10/18

We are here now.

B2GM Plenary Session

Final report(before LS1)

M. Masuzawa (2021.09.02)
The 25th KEKB Accelerator
Review Committee

17

Recommendations from ARC• The 25th KEKB Accelerator Review Committee (ARC) meeting• Meeting was held remotely on 1-2 September 2021.

• Slides of the presentations and the report are available at https://superkekb.kek.jp/event/131/• Most significant recommendations and more general recommendations;• Answers and reactions to ARC recommendations are under discussion now.

Answer/Reaction

 Sufficient beam time should be allocated for beam studies (other than routine tuning) to better understand and characterize the Arranging longer study time andmachines and their limitations, and to develop solutions or mitigation measures. More beam diagnostics would be helpful.
participation by foreign experts.
Planned, dedicated machine study periods would also enable remote participation by Task Force members and other foreign
experts.
Timing check and Check the RF gun timing and perform careful RF conditioning of the QTW RF gun to recover the RF pulse width and, possibly, tondcareful conditioning of RF gun
improve the 2 bunch emittance.
 Develop refined procedures including triggers so that Belle II can operate closer to the background limits of its sub-detectors.
Under consideration
 The six LER kickers should be rewired to use a common power supply, or three power supplies each of which feeds a pair ofMore stable thyratron
upstream and downstream magnets, to avoid problems related to thyratron misfiring and injection impact on circulating bunches.
Experimental data analysis
 Localize, identify and eliminate the source of vertical coupling in the HER injection line.
 Develop a safe plan for increasing beam intensity in documented phases/machine states, that are each formally verified for
Making safe plan
optimized performance, background and adequate machine protection.
 Establish a realistic model of the transverse impedance including accurate collimator wake fields and correct weighting with local Under consideration
beta functions; assess TMCI threshold for this model.
 Measure the single-bunch tune shift created by each collimator as a function of its gap, compare with theoretical expectation and Beam study in 2021c
verify that collimator contributions to the impedance are correctly understood.
 Further develop and study the non-linear collimation scheme (including the removal of some wiggler sections) and quantify its
Under consideration
implications on beam optics and beam dynamics.
 Carry out more comprehensive beam-beam simulations, incl. crab waist, impedance, lattice errors, etc., to guide the upgrade path. Discussion in ITF BB subgroup Consider increasing the number of focused task-force groups to other key areas such as linac, injection, collimation and machine Under consideration
protection.
 Invite external international task-force members to share organization efforts for the ITF sub-task groups.
Under consideration

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Upgrade plan during LS1• Upgrade items during LS1.

Y. Suetsugu (2021.09.02)
The 25th KEKB Accelerator Review Committee• LS1 (Long Shutdown1):• scheduled from July 2022
to May 2023.
• can be delayed by 6months or 1 year.

• What to be manufactured:• New beam pipes (HER)• It turned out that it may bepossible to do this without
hardware upgrade. (LER)• New front caps of QCS,
radiation shields (IR)• Already done (LER)• New magnets, powersources, beam pipes (LER)

2021/10/18

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Background noise reduction (IR)• Addition and modification of radiation shields at IR

Current status• Additional radiation shields around IP bellows pipes and Belle2 detector• Modification of front caps of QCSs
• Front plate material will be changed from W to SUS to suppress thegeneration of radiation.
• To make more space for the cables, new front cap of QCSR will be smaller
than current one.

K. Nakamura
Additional concrete shield

Y. Arimoto (2021.10.13)
B2GM PXD/SVD joint session

Current status

H. Yamaoka
Additional PE shield

W → SUSH. Yamaoka

Current status
B2GM Plenary Session

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Relaxation of TMCI limit (LER)• New non-linear collimation (NLC) scheme less likely to cause TMCIK. Oide (2021.05.14)
The 7th long-term operation plan meeting• Non-linear kick by skew sextupole magnet can make avertical displacement at the collimator.
• It is possible to open the collimator wider.
• It is possible to place the collimator at larger beta-function.
⇒ It is possible to relax TMCI bunch current limit.

• NLC will be constructed at OHO straight section.

• 50 wiggler magnets need to be removed.
• 2 skew sextupole magnets and 5 quadrupole magnets need to beinstalled.
• New magnet power sources andcabling works are required.
• New collimator and beam pipes
are also required.
Construction site of• Further development and studyof NLC scheme is needed.

non-linear collimator• Consideration of the effect of theremoval of some wiggler sections.
• Quantification of its implications
on beam optics and beam
T. Ishibashi
dynamics.

2021/10/18∼38 m
S. Nakamura (2021.08.06)
Nonlinear collimator meeting
B2GM Plenary Session

21

Three operation scenarios until JFY2024• Delaying LS1 due to COVID-19 is under consideration.
• Three possible scenarios are being considered.

• Present plan (start LS1 in July 2022), 6-months delay (start LS1 in January 2023), 1-year delay (start LS1 in July 2023)
Present plan (Aug. 2021)
2021
4

FY2021

6

7

8

9

10

~3.2M

7/5

2022
4

FY202256

8

9

FY2023

LS1

5

1

2

6

10/19

~2.2M

10

11

7

2022a
12/23

12

1

9

10

11

10/11

~2.5M

12

2

3
Total

~3.5M/y

1

2

3
2024a

2023c
7/14

Total

~1.7M ~6.2M/y

2/8

12/22

Total

~1.7M ~7.0M/y

2/9

2024
8

2023b
5/16 ~2M

3LS1 (PXD, TOP exchange)

7/15

2023
4

12

2023
7

2022b

~3.5M

4/1

11
2021c

2021b
4/1

Expected int. luminosity2022
5

Half a year late (FY2022 Budget request)

FY2021

6

7

8

9

10

~3.2M

7/5

2022
4

FY2022
4/1

5

6

4

2021/10/18

12

10/19

~2.2M

Base

TargetBase

Present

∼680

∼680

∼1260

∼910

6-months delay

∼850

∼850

∼1320

∼940

1-year delay

∼1160

∼1160

∼1200

∼870

8

9

10

11

2

~3.2M

10/4

~2.8M

10

11

7/4

6

7

8

LS1 (PXD, TOP exchange)

9

3

4

2022a
12/23

12

2022c

5

2021

1

2023
7

2022b

2023

FY2023

11
2021c

2021b
4/1

Int. Lumi. until 2024b [fb−1]

Target2022
5Int. Lumi. Before LS1 [fb−1]

One year late(b)

2021
4

Plan

12/26

12

2

Total

~6.0M/y

2
2/6

4/1

~1.8M ~3.7M/y

FY2022
4/1

~3.2M

9

7/5

5

6

~3.9M

10

FY2023

5

6

7

2023b
4/1

~3.5M

11

12

1

2

10/19

~2.2M

8

9

10

11

12/23

7/14

12

2

10

11

3
2023a

1/28

12

1

Total

~2.1 M ~6.0M/y

2024
9

Total

~1.7M ~7.0M/y

2/9

1

TOP Exchange
8

3
2022a

2023
7
7/27

2023

B2GM Plenary Session

8

2022b

4
Total

7

2021c

2022

3
2024a

6

2021b

4

2024
1

FY2021

3

LS1

2023c

~1.9M 12/25
10/31~1.7M ~7.0M/y

2/9

1

Total

2022
5

2

3
Total

LS1 (PXD exchange)~3.5M/y22

Summary• 2021ab run;

• Peak luminosity : 3.12×1034 cm−2s−1• βy* = 1mm, Beam current [mA]= 790 (LER)/687(HER), Number of bunches = 1174

• Total integrated luminosity : 213.5 fb−1

• Maximum Daily integrated luminosity (delivered) = 2.233 fb−1

• Maximum beam current [mA]: 1000 (LER)/940 (HER) w/o physics run• Collimator works during 2021 summer shutdown;• Jaw replacement• HER : D09V1, D09V2• LER : D06V1, D06V2 (hybrid-type jaws), D06H3, D06H1(short-stroke jaws)• LER D02V1 relocation• 2021c run plan;• Energy scan : 10.657 GeV – 10.810 GeV• Machine tuning & study items• HER beam injection, TMCI, beam-beam effect, LER crab waist• βy* = 1 mm
2021/10/18

B2GM Plenary Session

23Summary (cont’d)• Challenges and countermeasures;• Major challenges recognized so far:

• Vertical beam size blow-up, short beam lifetime, TMCI, low machine stability, aging of hardware and facilities, low
injection efficiency (HER), etc.

• Upgrade plans are under consideration to overcome the challenges.

• KEK has assembled the International Task Force to address the challenges of the upgrade.
• 4 subgroups : Optics, Beam-beam, TMCI, Linac• Answers and reactions to ARC recommendations are under discussion now.

• Major upgrade items that may be done during LS1;
• Addition and modification of radiation shield at IR• Construction of Non-linear collimation section (LER)• Operation plan until JFY2024;• Three possible scenarios:• Start LS1 in July 2022 (present plan)• Start LS1 in January 2023 (6-months delay)• Start LS1 in July 2023 (1-year delay)

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Fin.
Thank you for your attention.

Inter-University Research Institute Corporation High Energy Accelerator Research Organization (KEK)
大学共同利用機関法人 高エネルギー加速器研究機構 (KEK)Backup

2021/10/18

B2GM Plenary Session

26Improvement of injection efficiency (HER)• Can we improve HER injection efficiency by enlargement of physical aperture forY. Suetsugu (2021.09.02)
injection beam？

The 25th KEKB Accelerator
Review Committee• Beam Injection Task Force is considering
the need to enlarge the aperture.
• If necessary,• Three beam pipes will be replaced withnew ones with large aperture.
• Beam position monitor (BPM) for
injection beam will be modified for more
precise injection tuning.
BPM for injection beam

G. Mitsuka
2021/10/18

B2GM Plenary Session

32