SuperKEKB upgrade plans＆International Task ForceBPAC
Kyo Shibata (KEK Accelerator Laboratory)
2022.02.22

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)Challenges as a luminosity frontier machine
Y. Suetsugu (2021.09.02)
The 25th KEKB Accelerator
Review Committee+ 6) Low injection efficiency especially in HER.
2022/22/Feb.

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Countermeasures against challenges
Y. Suetsugu (2021.09.02)
The 25th KEKB Accelerator Review Committee

LS1
After LS1? (if necessary)
After LS1? (under consideration)

LS1
DoneLS1? (under consideration)
Done (partially)
LS1 (already started)
LS1 (already started)

2022/22/Feb.

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Revised schedule• Until JFY2023 (until the end of March 2023)• 2022a Run：21/Feb. ∼ 31/Mar.
• 2022b Run：1/Apr. ∼ 30/Jun.
• 2022 Summer Shutdown：Jul. ∼ Sep. New LS1：
• 2022c run：Oct. ∼ Dec.
Jul. 2022∼ Sep. 2023
• Long shutdown 1 (LS1)：
10 months from Jun. 2023
 Due to rise in electric bill, 2022c run is cancelled.
 Start time of LS1 is advanced to Jul. 2022

• Subsequent schedule• International Task Force (ITF) is considering
how to increase luminosity.
• If upgrades that require a long shutdown isneeded, we will have LS2 after 2026.
2022/22/Feb.

If LS2 is required, we will have it after JFS 2026.

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継続。

Upgrade items until LS2
Current status
Will be done in LS1. (Discussed later)
It may be possible without hardware upgrade. Machine study isnecessary, but it turned out to be difficult and time consuming.
Will be done in LS1 (Discussed later)
Done in 2021 summer shutdown. Its effect was confirmed in 2021c.

NewImprovestability

Machine studies in 2022ab is required in deciding whether to install an
NLC in LS1. (Discuss later)
Countermeasures against “undesirable residual kick” and “kicker-pulser
misfiring”. Will be done partially in LS1. (Discussed later)

injection kicker
modification

Machine study was done in 2021c. It was turned out that the rotatable
magnets are useful to relax beam-beam effect. No hardware update will berequired.
Trial model of robust collimator was installed in 2021 summer shutdown.
Beam test will continue in following runs.
Already started.
Already started.

• Upgrades during and after LS2
2022/22/Feb.

Under consideration by ITF. (Discussed later)
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Aperture enlargement of HER injection channel 1• HER injection efficiency should be improved.
• Injection of HER beam is unstable.

• Understanding of injection became deeper during 2021c.
• It was turned out that horizontal aperture of injection channel
should be enlarged to improve injection efficiency.
• To enlarge aperture of injection channel, beam pipes around HER
injection point will be replaced new ones during LS1.

• Stable physics run requires stable injection.
• Low injection efficiency can limit the maximum beam
current.
LER injection status during 2021c

HER injection status during 2021c

N. Iida (2022.1.21) BITF meeting

Our target is 80%.

2022/22/Feb.

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Aperture enlargement of HER injection channel 2• Problem of HER injection

No enough room

• Wall can be an obstacle to injection.

wall• A wall should be placed between beam channels
for stored beam and injected beam.
• Injected beam orbit is too close to the wall.
• High levels of radiation detected at the injection
BPM chamber indicates that the injected beamhits the wall.
• It is hard to modify the injection beam orbit.
⇒ it is necessary to enlarge the horizontal apertureof the injection channel.
N. Iida (2022.1.21) BITF meeting•

What is planned during LS1•

Replacement of three beam chambers with newones.
• Update of injection BPM⇒ More precise injection tuning

2022/22/Feb.

M. Kikuchi (2021.12.03)
BITF meeting
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IR radiation shield modification 1

K. Nakamura (2022.02.03)
10th SuperKEKB long-term operation plan meeting
2022/22/Feb.

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IR radiation shield modification 2K. Nakamura

New heavy metal shield on IP bellows
Y. Arimoto

K. Nakamura (2022.02.04)
10th SuperKEKB long-term
operation plan meeting
2022/22/Feb.

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Material change from W to SUS (QCS cryostat front plate)(Tip of QCS cryostat will be modified to make more space)9

IR radiation shield modification 3• Additional concrete shield (IR) & polyethylene shield (Belle2)• For shielding fast neutrons• New concrete shields and polyethylene (PE) shield will be added to a spacethat currently has no shield.
• Additional PE shields around QCS are also planed.

• Expected effects of shield modification• Physics run with wider collimator setting• Physics run with larger total currents and bunch current

Add concrete shields

Add PE shields

shield mockup

PE shield

H. Yamaoka (2021.11.04)
IR meeting

H. Yamaoka (2021.11.04) IR meeting
2022/22/Feb.

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Non-linear collimator 1• 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. Ishibashidynamics.

2022/22/Feb.

∼38 m
S. Nakamura (2021.08.06)
Nonlinear collimator meeting
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Non-linear collimator 2• Understanding of NLC scheme has advanced in 2021c, but further study is required.

• It was turned out that beam blow-up becomes remarkable when βy* (vertical β-function at IP) is squeezed.
• Vertical β-function (βy) at collimator and impedance (kick factor k) of collimator do not depend on βy*. (Σkβ of collimators does
not depend on βy*.)• Is beam blow-up is caused by ordinal TMCI, which occurs when Σkβ becomes larger than the threshold?
• It seems that there are other impedance sources, that increase kβ when βy* is squeezed.
⇒ Possible candidate : Tapered beam pipes for the beam final focus system (QCS) at IR

T. Ishibashi (2022.1.21)
NLC meeting

Tapered QCS beam pipe

• Further machine studies in 2022ab is needed indeciding whether to install an NLC.
• Impedance measurement of QCS beam pipes• Investigation of the countermeasure against beam
blow-up other than NLC• And so on.
• Final decision will be made around May 2022.

2022/22/Feb.

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Injection Kicker modification 1• Problems with the injection kickers (mainly for LER)
1.

Undesirable residual kick due to difference in magnetic field waveforms between K1 kicker and K2 kicker

Causes;
1. Difference in ceramic chamber profile for eachkicker.
2. Difference in waveform of current supplied toeach kicker.

2.

Countermeasure;
1. Waveform tuning of current supplied to K2 (2022ab)• Magnetic field waveform of K2 is adjusted to be
the same as K1 by adding inductance.
2. Replacement of K1 ceramic chambers with sameones as K2 (LS1 if necessary)

Kicker-pulser misfiring and resulting destruction of collimator
Causes;
1.
2.
3.
4.

Countermeasures;
1. Thyratron replacement with new ones with higher
breakdown voltage
2. Update to noise-resistant trigger system
3. Robust collimator head (ex. carbon collimator)

Thyratron misfiring
Fake trigger signal due to noise
Trigger amplifier unit failure
Malfunction of Event Receiver

Drastic countermeasures：• “Double kicker system” where K1 and K2 kickers are driven by one power supply• Replacing thyratrons with semiconductor switches
2022/22/Feb.

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Translation fromT. Mimashi’s slide
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Injection Kicker modification 2
T. Mimashi

Kicker K2

Septum magnets

Kicker K1

Injection Point

Injected beamStored beam

Kicker K2
2022/22/Feb.

Kicker K1
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Injection Kicker modification 3• Measures against undesirable
residual kickTi coating thickness = 6µm
K1 ceramic duct

• Waveform adjustment by additionalinductance in 2022ab• Replacement of K1 ceramic chamberswith same ones as K2 in LS1

Difference in profile of ceramic ducts• Measures against kicker-pulser
misfiring

Difference in K1 and K2• Collimator heads could be
replaced with robust ones.

Difference in magnetic field waveforms
due to eddy current

Magnetic fieldwaveform
Waveform tuning by adding inductance in K2

2022/22/Feb.

Input current
K1
K2

w/o inductance in K2
w/ inductance in K2• Consideration of double kicker
system has just started.
• It is hard to change to double
kicker system during LS1K2 ceramic duct

T. Mimashi

BPAC

Residual horizontal kick(difference in K1 and K2 waveforms)
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International Task Force (ITF) 1
While achieving steady progress,
SuperKEKB encounters some challenges as a luminosity frontier machine

M. Masuzawa

ITF has beenorganized
Kick-off meeting on July 28, 2021

ITF charge
Y. Suetsugu (2021.07.28) ITF kick-off meeting
2022/22/Feb.

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International Task Force (ITF) 2• Activity period is about one year until the start of LS1• Online meeting per month basicallyTranslation fromM. Masuzawa’s slide• Meeting is basically open session, but can be closed session if necessary.

• Review by ARC six months after the kick-off meeting• Review meeting will be held on Feb. 25.

• Final report is made by end of July 2022.

Y. Suetsugu (2021.07.28) ITF kick-off meeting
2022/22/Feb.

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International Task Force (ITF) 3• Subgroup for each topic was created to promote high activity.

Translation fromM. Masuzawa’s slide• Main and sub contact persons for each subgroup were assigned.
• Mailing list for each subgroup were created.
https://www-linac.kek.jp/linac-com/skb-itf/ml/• Participants of each subgroup were recruited.

• ITF has four subgroups;••••

Beam-beam : D. Zhou (main)/ K. Ohmi (sub)Optics : A. Morita (main) / H. Koiso (sub)TMCI : M. Migliorati (main) / T. Ishibashi (sub)
LINAC: M. Satoh (main) / S. Matsumoto (sub)2022/22/Feb.

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International Task Force (ITF) 4
Examples of activities;• Machine studies at SuperKEKB proposed by ITF• Examples; New sextupole setting trial, Chromatic coupling resonance survey, etc.
• New setting of LER sextupole magnets did not increase the beam lifetime so far, but the machine study
will be continued.
• Sharing of SuperKEKB lattice file• has made it possible to perform optics calculations with different codes and to check them.
• increased the number of person performing optics calculation.
• Lecture on “SuperB IR chromaticity correction” by Pantaleo Raimondi, the proponent of Crab waist• And so on.
Additional effect:
ITF framework can facilitate information exchange and cooperation
between research institutes.

Translation fromM. Masuzawa’s slide

Goal:Work together to improve SuperKEKB performances in the framework of the SuperKEKB/Belle-II collaboration and withthe accelerator community in the world.
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Summary• LS1 schedule was revised.

• Start time of LS1 was advanced from Jan. 2023 to July 2022.
• 2022c run is cancelled due to rise in electric bill.

• Physics run will be resumed in the autumn of 2023 (2023c run).

• Accelerator (MR) upgrade items planed in LS1;

• Aperture enlargement of HER beam injection channel• IR radiation shield modification (large-scale work)• Belle2 detector will be upgraded in parallel.

• Non-linear collimator installation? (large-scale work)• Further machine studies in 2022ab is needed in deciding whether to install an NLC.

• Replacement of ceramic ducts for LER injection kicker• And so on.

• International Task Force• KEK has assembled a powerful International Task Force to address the challenges of the upgrade.
• Activity period is about one year until the start of LS1. （From July 2021 to July 2022）• Deep discussions are actively conducted by four subgroups.
• 4 Subgroups : Beam-beam, Optics, TMCI, Linac• Final report will be made by end of July 2022.
2022/22/Feb.

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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)Backup2022/22/Feb.

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