Discussions on the long-term
operation plan in the last year
Y. Suetsugu
KEK
The 26th KEKB Review Meeting
09/02/2021
2021/9/2

1SuperKEKB project timeline

Construction: 2011-2016
Phase 1 Test run 2016.2 – 2016.6
Phase 2 Pilot run 2018.3-2018.7
Phase 3 Physics run 2019.3.11-present

The current goal:~6 10 cm s
and
50 ab
by around 2031
2021/9/22SuperKEKB achievements to date
• The performance has been improved steadily.
• SuperKEKB is already exploring uncharted territory!

∗

3.12 10 cm s
(world record)

0.8 mm(world record)
213.5 fb
(July, 2021)

2021/9/2

3

Challenges recognized in recent commissioning• To improve the machine further to achieve the goal, however, various challenges asfollows should be solved:
1) Severe beam-beam effect (vertical beam size blow-up)••

Vertical beam size (vertical emittance) blow-up has been observed at high bunch currents.
Relaxed by the crab-waist collision scheme, but it still remains.

2) Shorter beam lifetime than expected in the design phase.
The maximum bunch currents are limited by the balance between the lifetime and theinjection power.
• The dynamic aperture is very small due to the beam-beam effect and crab-waist sextupoles,
while the physical aperture is limited by the beam collimators.
•

3) Lower bunch-current limit due to TMCI than expected.
•

The cause is higher impedance of beam collimators, where the apertures are smaller thanthe design values to suppress high background to Belle II.

4) Low machine stability••

Abnormal beam aborts, sometimes leading to the damage of collimators.
Operation efficiency during 2021ab, for example, was almost 0.5, lower than expected one,
0.65. (Main causes: machine tunings, machine troubles, maintenance, etc.).

5) Aging of hardware and facilities, and so on.
2021/9/2

4

Long-term operation plan
• Current operation plan (luminosity profile)• The current goal is to achieve~6 10 cm s and
50 ab by around 2031,
which requires an intermediatemachine upgrade around 2026 (LS2)that improves the luminosity by afactor of 2-3.
• The plan was adopted in the MEXT
roadmap 2020.
• The plan and profiles were assessed by
the external review committees(Accelerator Review Committee (ARC,βy* [mm]
2020/7) and BPAC (2020/6, 2021/3, 6))• Over the next year or so, perform beam measurements to determine if the
proposed upgrades are absolutely required to get to the design luminosity.
• Determine which technical studies need to be carried out now, before adecision can be made, within about 2 years. (Excerpt from the last ARC)
2021/9/2(See Appendix A)

5

Long-term operation plan
• Based on the recommendations from these review committees, “Long-term operation
plan meeting” (internal, Chair: H. Koiso) was launched in August, 2020. (See Appendix B)• To solve the confronting challenges and to realize the plan, a variety ofcountermeasures have been proposed and discussed over the last year in various
meetings, such as MDI (Machine Detector Interface) meeting (Chair: H. Nakayama), ITF(Injection Task Force) meeting (Chair: N. Iida), IR technical meeting (Chair: N. Ohuchi,
K. Shibata) and so on, as well as the Long-term operation plan meeting.
• Key measures to improve luminosity and integrated luminosity• To improve luminosity• Increase injection power (injection efficiency, bunch charge) or improve beam lifetime(dynamic aperture and also physical aperture)• Improve beam-beam parameter (low emittance)• Relax TMCI limit (important if emittance is still large).
• Lower background -> Wide collimator aperture (physical aperture)• To improve operation efficiency (Integrated luminosity)

2021/9/2• Improve stability of machines• Increase efficiency of beam tuning (improvement tuning knobs)• Execute anti-aging plans for facilities

6Planned countermeasures• Major countermeasures discussed so far.
• See Appendix C for some details.
Aim

Possible countermeasures
Linac upgrade to designed specification(1)• Increase injection power(efficiency)

Large physical aperture at electron injection point (HER)
Linac upgrade beyond designed specification• Relax beam-beam

(2)

(3)

effect• Expand dynamic
aperture

Utilizing rotatable sextuplole magnets (LER)“Perfect matching”
QCS modification (Option#1): Move QC1RP to the far side of IP
Larger scale QCS modification (Option #8)• Suppress BG

QCS cryostat front panel modification and additional shield to IP bellows• Expand physical

Optimization of collimator location

aperture(4)• Relax TMCI limit(5)• Improve stability(6)• Anti-aging measures

2021/9/2

Enlargemen of QCSR beam pipe (Option#3)“Non-linear collimator”
Robust collimators
Upgrade of beam abort system and loss monitor system
Preparation of standby machines and spares, repair of facilities, etc.
7Planned countermeasures• High-priority countermeasures before LS2
Aim

Possiblecountermeasures

Increaseinjection power(efficiency)

Linac upgrade to
designed specification

Full spec injection (bothpower and quality)

Relax beambeam effectUtilizing rotatablesextupole Magnets

Ready. Need preparation of
Beam-beam parametertuning knob. Knob tuning will be(emittance), beam lifetime
tried during 2021c.

Improve stability Robust collimator

Expected improvement

Sustainability

Ready status

LS1

LS2

2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031~

On going sequentially.

On going sequentially. Need
more R&D and beam test

Upgrade of beam abort
On going sequentially with Belle
Improve stability system and loss monitor Operation stability
II group.
systemOn going sequentially.
Operation efficiency
Anti-aging(standby machine, repair of Especially for long shut down
Anti-aging measures
measuresfacilities)
periods• Essential to achieve ~2x1035 cm-2s-1 before LS2.
Rotatable Sextupole magnet

T. Ishibashi
2021/9/2

M. Masuzawa

8Planned countermeasures• Possible countermeasures in LS1
LS1
LS2
Possible
Expected improvement
Ready status
2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031~
countermeasures
Large physical aperture at
Need further estimation,
Increase injection
electron injection pointHER Injection rate x #?
simulation, design of beam
power (efficiency)
(HER)
pipes
Need further simulation, design,
Expand dynamic
LER beam lifetime
manufacturing of magnets and“Perfect matching”
aperture(Tousheck) x ~1.5.
pipes
Aim

Expand physicalaperture
Suppress BG

QCS cryostat front panel
Background, Physical
Production is on going. Will
modification and additional
aperture, TMCI limit x ~1.2 be ready by 2022.
shield to IP bellows

Expand physicalaperture
Suppress BG

Optimization of collimator Background x ~1/2
location(Storage beam)

Relax TMCI limit “Non-linear collimator”

2021/9/2

TMCI limit x~2
Background x ~1/2
(Storage beam)

On going. Need further
simulation.
Need further simulation, design,
manufacturing of magnets andpipes. Production of PS has
started.

K. Nakamura

K. Oide9Planned countermeasures• Possible countermeasures in LS2
Possible
LS1
LS2
Expected improvement
Ready status
2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031~
countermeasures
QCS modification
Widen dynamic(Option#1): Move QC1RP Found to be no effect.
Will be not adopted
aperture
to far side of IP
13.5 mm -> 15 or 18 mm,
Expand physicalNeed design, manufacturing
QCSR beam pipe
βy*=0.3 will be possible. But noapertureof correction magnets andeffect on dynamic aperture,enlargement (Option#3)
Lower BG
pipes
TMCI limit x ~1.5.
Aim

QCSR configuration

IP

N. Ohuchi
Option #1

2021/9/2

Option #3

10

Preliminary luminosity estimation• Estimated luminosity with countermeasures discussed so far.
• Assumptions: Designed beam injection (after Linac upgrade) and vertical emittance (No
TMCI limit), No background limit, Only Touschek lifetime. (See Appendix D.)
Lp [x1034 cm-2s-1]

Int. L [fb-1]

RM2020Estimation
w/ LS2~20

RM2020Estimation
w/o LS2~30
Estimation
w/o LS2

Estimation
w/ LS2• Mainly due to the short beam lifetime (narrow dynamic aperture), the luminosity will be lower
than expected.
• The ideas of the intermediate upgrade of IR around 2026 we have planed so far are not as
satisfactory from the viewpoint of int. luminosity as given in RM2020.

More effective measures to boost up the luminosity is required!
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Future Plan
• We will continue the effort to find more effective (x2~3) measures, not limited to the IR
but also to other parts of the MR and Linac, to maintain the target luminosity profile.
• Ideas of a more revolutionary upgrade including some modification of Belle II should beconsidered to reach even higher luminosity; this may require a longer time for R&D(~203x).
• On the other hand, some practical conclusion should be obtained before LS1(2022~2023) on the feasibility and contents of the upgrade around 2026 (LS2),
considering the preparation period of hardware.

• Create an international task force (Coordinator: M. Masuzawa) under the
management of the KEK Accelerator Lab. and B promotion office (BPO) to pursue
effective measures for recovering the luminosity profile and reaching target luminosity.
(See Appendix E and Maszawa-san’s talk next)

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Summaries• Enthusiastic discussions have been on going since last year to examine and realize
the long-term plan presented in MEXT Roadmap2020.
• Although the performance of SuperKEKB has been improving steadily, various
challenges should be solved to further improve the machine to achieve the goal.
• Against these challenges, various countermeasures have been proposed in various
meetings based on the simulation and observations to solve them.
• Some countermeasures were decided to be taken during LS1.
• However, the luminosity seems to be still lower thanInt. L [fb ]expected considering various limitations.
-1• The ideas of the intermediate upgrade of IR around 2026
we have planed so far are not satisfactory.

• We have to continue to find more effective measures,
not only limited to the IR but also including the otherparts of MR and Linac to maintain the target profile.
• The international task force has been createdespecially to discuss ideas to boost up the luminosity
by the intermediate upgrade.
2021/9/2

RM2020Estimation
w/o LS2

Estimation
w/ LS213

We greatly appreciate your corporation!

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Appendix A: Recommendations from ARC and BPAC
(Excerpt)

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Long-term operation plan
• Excerpt from KEKB Review Report (Long-term plan part) -1 (2020/7)• R7.2: Over the next year or so, perform beam measurements to determine if the
proposed QCS upgrades with larger apertures are absolutely required to get to thedesign luminosity or, e.g., to half the design luminosity.
• R7.6: Determine which technical studies (essential beam studies and QCS coilparameter studies) need to be carried out now, before a decision can be made, within
about 2 years, on starting construction of new QCS quadrupoles.
• R7.7: Determine the technical staffing and accelerator experts needed to construct
the required hardware upgrades and examine if new technical staff will need to be
trained or hired to design and execute these upgrades.

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Long-term operation plan
• Excerpt from KEKB Review Report (Long-term plan part) -2 (2020/7)• R7.8: Evaluate a backup plan to simply increase the luminosity with the existing
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 thenintegrate luminosity for about 10-12 years at 7-8 months per year to obtain an
integrated luminosity of 50 ab-1 by 2032-2034.
• R7.9: Present a detailed SuperKEKB upgrade plan with underlying reasoning and dataat the next ARC meeting.
• Detailed long-term upgrade plans should be finally decided once full performance withthose upgrades is predicted within a quantitative performance model. This makes surethat the long-term quadrupole aperture is chosen wide enough, background sources
and paths are understood, lower beam lifetime can be handled, impedance stays undercontrol, and the collimator system is adequate.

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Long-term operation plan
• Excerpt from BPAC Report (2020/6)• Based on the experience in operating SuperKEKB, the machine team has beendeveloping ideas that could achieve the physics goal of the Belle II experiment withlower consumption of electricity . The committee understands that such an operation
scenario over the next ten years was presented 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 and detector. The
BPAC strongly encourages a close collaboration between SuperKEKB and Belle II
to further explore various ideas and conduct the necessary research anddevelopment work. Implementation of the necessary upgrade should then follow
after positive evaluation of technical 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.

2021/9/2

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Long-term operation plan
• Excerpt from BPAC Report (2021/3)• The SuperKEKB machine has been operating at higher luminosities with lower beam
currents than those of the KEKB machine and the committee appreciates the continuous
effort and improvements by the machine group for stable running of the machine. It
appears that there are persistent obstacles, such as the increase of emittance for thehigh energy beam in the injection line, which prevent the machine from increasing
luminosities without raising the background above the acceptable level for theexperiment.
• Another important issue on a relatively short time scale is the consolidation of the ageingmachine components, in particular for the injector linac. The committee urges themachine group and the KEK management to address deferred maintenance in a timely
manner by making an inventory of critical spare parts and making a replacement plan.
• For the longer term, the committee thinks that the characteristics of the machine must be
fully understood and exploited first to increase luminosities, before attempting a major
hardware upgrade such as the new superconducting focusing quadrupole magnets(QCS) in the interaction region. Understanding of the hardware limitation of the machine
would allow a prioritized and optimal upgrade path to be made.
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Appendix B: Long-term operation plan meeting

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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 efficiency on βy* [Y. Funakoshi]
2021/9/2

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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 a viewpoint of beamcommissioning [N. Iida]• Middle and long-term outlook on injection efficiency and luminosity [Y. Funakoshi]• The fifth meeting on 2021/2/17••••

Mid-long term plan at the injector linac [K. Furukawa]Long-term plan at BT and DR [M. Tawada]
Remarks on injection issues discussed in the magnet group [Ohki]
Long-term strategy of beam collimators [T. Ishibashi and S. Terui]• The sixth meeting on 2021/3/25• Upgrade plan of Linac positron source, pulsed magnets etc. (1) [Y. Enomoto]• Expectation of Luminosity [K. Nakamura]• Nonlinear collimator for LER in a dedicated section (1) [K. Oide]

2021/9/2

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Long-term operation plan meeting• The seventh meeting on 2021/5/14••••

Upgrade plan of Linac positron source, pulsed magnets etc. (2) [Y. Enomoto]Nonlinear collimator for LER in a dedicated section (2) [K. Oide]
Effect of collimator aperture on beam lifetime (LER) [Y. Funakoshi]
Current (intermediate) summary and future plan [Y. Suetsugu]• The eighth meeting on 2021/8/27••••

Study results on semi-perfect matching [K. Oide]
RF system and possible beam currents [K. Akai]
Long-term plan of RF system [K. Watanabe]
Upgrade items and their persons in charge [K. Shibata]• The nineth meeting on 2021/9 [planed]• Upgrade of RF gun laser system for high charge low emittance electron beam [R. Zhang]• R&D on RF tubes for high-electric field stable acceleration [H. Ego]

2021/9/2

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Appendix C: Countermeasures discussed so far

2021/9/2

24

Countermeasures discussed so far(1) QCS modification (#1)
• Modification of QCS to avoid interference between the quadrupole magnetic field and the Belle II
solenoid field: A promising method to mitigate the narrow dynamic aperture in LER• Two ideas to relocate QC1P to the places farther from IP were examined.
(1) Retract QC1RP (QC1LP) and QC1RE (QC1LE) 250 mm and 100 mm, respectively.
(2) Retract QC1RP 375 mm.
• The radius of beam pipe inside QC1RP can be enlarged from 13.5 mm to 27 or 30 mm.
• However, it was found by simulations that little improvement in the dynamic aperture was expectedeven without beam-beam effect.
• Low solenoid field (1.5 T  1.2 T) had also no improvement.
QCSR configuration

IP

2021/9/2

N. Ohuchi

QCSR configuration

IP

25

Countermeasures discussed so far(2) Rotatable sextupole magnets• It was also found in a simulation that the narrow dynamic aperture will be cured using the rotatablesextupole magnets installed in the local correction region at Tsukuba (K. Oide).
• Eight rotatable sextupole magnets have been already installed. The operation check has been
completed for each magnet.
• 2021a run was operated with a fixed angle of rotation.
• The effect has not been studied well.
• One problem in using these magnets is that it is now hardly possible to rotate them with beam. In
other words, we cannot fully use them as a tuning knob.
• Developing a new software to rotate them synchronously is on going.
• IP chromatic coupling correction will be tried during 2021c run.
K. Oide (2021/6)
Rotatable Sextupole magnet

M. Masuzawa

2021/9/2

26

Countermeasures discussed so far(3) QCS modification (Option #3)• Enlarge vertical aperture of beam pipes in QC1P without changing the boundary conditions between QCS
and Belle detector.
• It is expected to increase physical aperture and then increase beam lifetime determined by the physicalaperture, and also to reduce background.
• Low background -> large aperture at beam collimators -> relax TMCI limit.
• Correction magnets are relocated to outside of the main quadrupole magnets.
• The inner diameter can be enlarged from 13.5 mm to 18 mm geometrically (QC1P).
• However, it was found by simulations that little improvement in the dynamic aperture was expected.
• The modification will be possible after 2026 even at the shortest case.
Cross section of QC1RP

N. Ohuchi
2021/9/2

27

Countermeasures discussed so far(4) QCS cryostat front panel modification and additional shield to IP bellows••••

Make rooms for cables of Belle II detectors.
Exchange plate material from tungsten to stainless-steel to reduce the beam background.
Add new radiation shield inside the cryostat.
FWD and BWD bellows shields were also developed. In the current mechanics, there is no beam BG
shield around the bellows pipes and a fraction of BG go into CDC and TOP from these regions.
• The preparation for LS1 is on going together with Belle II group.
K. Nakamura

2021/9/2

K. Shibata 2021/3/4

28

Countermeasures discussed so far(5) Perfect matching

Luminosity vs by* (K. Oide)• Beam simulations with beam-beam effect have shown that “perfectmatching” of LER optics significantly increases dynamic aperture(about 60%) and improves luminosity (K. Oide and H. Koiso)• Specific studies are to be completed, but there is a possibility that
this can be achieved with about four normal quadrupole and fourskew quadrupole electromagnets.
• An equivalent electromagnet power supply is also required.
• New production of beam pipe for skew quadrupole electromagnet
is required.
• Work during a long-term shutdown, LS1 or LS2.
Dynamic aperture with CW=80%

Dynamic aperture with CW=40% + “perfect match”
K. Oide2021/9/2“Perfect match”:• Phase shifts between
SLYTRP2/SLYTLP1 and IP arejust 0.5 (x) and 0.75 (y).
• The values of βx and βy at thecenter of four SLY（SLYTLP1&2,
SLYTLP1&2） are set to be thesame, respectively.
29

Countermeasures discussed so far(6) Non-linear collimator• A vertical-type collimator, called as “non-linear collimator”, is located between a pair of specified skewsextupole magnets. The non-linear vertical kicks by the magnet are utilized to enlarge the verticaldisplacement of particles at small βy section, which will reduce the affect of collimator impedance andmitigate TMCI (K. Oide)• The collimator will be installed at after the injection point, before the IP and the dispersion-free section,such as OHO straight section.
• Vertical phase advance of 0.25 between the sextupole magnets and the IP is possible, which reduce beam
background.
• The dynamic aperture looks fine so far by simulation.
• The preparation has started to install the non-linear collimator during LS1.
K. OideIP

OHO

2021/9/2

T. Ishibashi

30

Countermeasures discussed so far(7) Collimators: Optimization of location• Background will be suppressed by optimizing the locations of beam collimators.
• Example 1• A new LER optics, where the phase advance between D03V1 and D02V1 collimators is (half-) integer
was tried in 2020c run [∆νy(D06V1 – D02V1) = 16.0, ∆νy(D03V1-D02V1)=3.5]• Aiming also to protect D02V1 by not only D06V1 but also D03V1.
• TOP storage BG (beam-gas Coulomb) decreased by 30~40%. However, effect of impedance ofcollimators (especially D06V1 with carbon jaws) became prominent in this case (2020c).
• Example 2
T. Ishibashi
IP• Another optics, where the phase advances between QCS1, D06V1 and
D02V1 are (half-) integer, is also said to reduce background (beam gas
Coulomb) by 40%.
D03V1
D02V1
• D02V1 collimator will be relocated during the 2021 summer shutdown,
and effect will be checked during 2021c run.

D06V1
2021/9/2

2020/12/14, Nakayama

31

Countermeasures discussed so far(8) Collimators: Low-impedance and robust collimator• Collimator heads have been damaged several times by beam during heavy beam loss.
• The cause of the beam loss is not clear, but could be so-called “dust event”.
• New D06V1 collimator (carbon jaws, called “Low-Z collimator”), which was located at the place where thephase advance from D02V1 is integer, and was expected to protect D02V1 from strayed beams, but it did
not work (2020c). Furthermore, high impedance of the carbon head induced the heavy TMCI.
• New low-impedance and robust collimator is required for stable operation.
• A test model, composed of tantalum and carbon with copper coating, will be installed during 2021 summer
shutdown, and will be tested during 2021b run.
• The clarification of the beam loss mechanism is also important. Upgrade of loss-monitor system is underconsideration (see (12)).

By T. Ishibashi and S. Terui2021/9/2

Carbon headTop
Bottom32

Countermeasures discussed so far(9) BT (Beam Transport) line and DR upgrade: on going sequentially
•
•
•
•
•

Improvement of extraction kickers
Additional correction kicker at extraction line
Spares of septum magnets
Anti-aging measures for magnets and their PS
Improvement in injection kickers

•
•
•
•

Beam diagnosis lines using SR
Optical fiber loss monitor
Additional Q-mag at ECS chicane
High-precision BPM

Spares of
septummagnets

Continuous COD
Correction (CCC)
Improvementof extraction
kickers

Additionalcorrection
kicker at
extraction line

2021/9/2

Additional Qmag at e+
ECS chicane

Anti-aging
measures formagnets andtheir PS

Improvement
in injection
kickers

Additional
precisecorrection
magnets

High-precision
BPM at BT
Optical-fiber
loss monitor

Beam size
monitorusing SR33

Countermeasures discussed so far(10) Linac upgrade up to designed specification: on going sequentially• Upgrade to the designed specification (4 nC/bunch, 2 bunches, 25 Hz repetition with an efficiency of 80%)
is mandatory.
• Low-emittance, high-charge and stable RF gun.
• Efficient positron capturing.
• Upgrade of accelerating structure is on going.
• Active mover for magnets and accelerating cavities to control emittance growth due to wake field.
• Beam collimators to cut beam halo.
• Additional ECS (Energy Compression System) for electron beam.
• More pulse magnets to supply higher beam.
• Measure against trace amounts of PCB (required by LAW)
Pulsed magnet

BJ-arc
1.5 GeVA

C

Positron generationand capture

1

2

Bunch length
compression

To PF
2.5 GeV
0.2nC x 1

1.1 GeV
e+ damping ringElectron guns
Low-emittance e- 4 nC
Primary e- for e+ generation 10nC

Primary e- fore+ generation
3.2 GeV, 10nC x 2

Active mover

Energy compression

3

Energycompression

4

5
Accelerating structure

2021/9/2

To PF-AR
6.5 GeV
0.2nC

To LER
4.0 GeV
4nC x 2

To HER
7.0 GeV
4nC x 220 um

34

Countermeasures discussed so far(11) Large physical aperture for injection beam (HER)
•
•
•
•
•

One of countermeasures to improve the injection efficiency for HER. (see (9))
Enlarge physical aperture for the injection beam.
Reduction of the residual radioactivity there is expected.
The efficiency should be evaluated more specifically.
Understanding the actual beam orbit of injection beam and monitoring of theoutput of septum magnets are also required.
(Present HER)

2021/9/2(Present LER)

Channel for injection beam

35

Countermeasures discussed so far(12) Improvement of beam abort system and loss monitoring system• Rapid (~10 µs) heavy beam losses have been observed in LER and also HER.
• They have sometimes resulted in damages of collimator, QCS quenches and heavy damages to SVD.
• The cause of them, however, have not been well clarified, but one possibility has been said to be a dust
event (i.e., beam loss due to the collision of circulating beams with dust in beam pipe).
• The mechanism of the beam loss should be clarified for stable operation at high beam currents.
• The beam abort system have been greatly improved, and now the beam can be aborted within 30~40 µs
after a beam-abort trigger. But the beam loss was faster than that time.
• The setup of a beam loss monitor system to localize the energy-loss point is planned using PIN diodes (ordiamond sensors) at collimators.
• It was reported that a beam-abort trigger could be issued ~8 µs faster than the present DIAMOND sensors
by using CLAWS (sCintillation Light And Waveform Sensors) (I. Popov). The system has been in operation
since 2021b run.

2021/9/2

36

Countermeasures discussed so far(13) Anti-aging measures
•
•
•
•
•
•
•
•

Leaking roofs, corroded equipment's such as cooling system for RF
MR power supply building and ancillary equipment are very old.
Leakage may cover the power supply and interrupt operation.
First-aid measures have been taken, such as installing a roof inside, but drastic measures are required toprevent rain leaks in the power supply building.
Further, for example, corrosion of the klystron cooling system is often in a dangerous state.
Some of the electromagnets and power supplies of the BT (Beam Transport Route) have been usedsince the Tristan era, and they are very old.
The amount of cooling water is also frequently reduced, and the operation is interrupted.
It has been confirmed that the inside of the cooling water pipe is clogged with copper oxide. If nothing isdone, it will hinder driving.

Corrosion of cooling fan for RF system

2021/9/2

Water leak of MR power supply buildingBT

37

Countermeasures discussed so far(14) Large scale modification of IR (Option #8)• Dynamic aperture increases as the distance between IP and QC1P decreases.
• To get sufficient effect, twice the beam lifetime for example, it is required to make distance between IP and
QC1RP half.
• QCS magnets will be moved forward as much as possible while keeping the 17-degree-lines.
• More drastic IR upgrade, including Belle II upgrade, will be required.
• The R&Ds will take more than ten years or more.

New IR upgrade option

Current IR configuration
2021/9/2

N. Ohuchi, 2021/2/18
38

Countermeasures discussed so far(15) Linac upgrade to beyond designed specification• For e+, for example (by Y. Enomoto)• Increase FC current• Increase primary electron current• Increase accelerating field gradient• Optimize FC structure• Adopt moving target (pass e+ and e- beams on the same orbit)• Shorten the distance between FC and the first accelerating structure• Put electron gun after J-arc to increase bunch charge.
• Use L-banc accelerating structure to increase aperture.
• Use super-conducting FC to increase the magnetic field.

B
J-arc
1.5 GeVA

C
2021/9/2

1.1 GeV
e+ damping ringElectron guns
Low-emittance e- 4 nC
Primary e- for e+ generation 10nC

Primary e- fore+ generation
3.2 GeV, 10nC x 2

Positron generationand capture

1

2

Bunch length
compression

To PF
2.5 GeV
0.2nC x 1

Energy compression

3

Energycompression

4

5

To PF-AR
6.5 GeV
0.2nC

To LER
4.0 GeV
4nC x 2

To HER
7.0 GeV
4nC x 220 um

39

Appendix D: Luminosities under bunch-current limitations

2021/9/2

40

Luminosities under bunch-current limitations• The challenges add new bunch-current limits in addition to original RF-power andhardware limits to the operation, and will limit the luminosity.
•

Lifetime (injection power) limit based on the formula presented by K. Oide.
-EF
"#$

-EF
G$ '$ 67

H$- ∗ =*#TMCI limit+(,"#$•RF power limit

%&
"#$

•

Hardware limit (for example by BPM)

•

1 23
"#$

-EF
"#

1.4 /0 "#+(,- 1.5 /0
'( )
'$( )
"#%&
*#
*#
2 /0

"#1 23

G '

-EF

67

H-

∗

*#

=

H$H-

3.6
1.2

'$( ) =2.59 A, ' ( ) = 1.87 A before LS2'$( ) =2.82 A, ' ( ) = 2.04 A after LS2

2 /0• Emittance (εy) is also a key parameter.
• Luminosity formula1*# "#$ "#∗445 67 sin:, ;<=2021/9/2

>

?@
25A

10I
10J

; ∗∓ '@ D @ ?@ '@ D @1B ∗~(when limited by beam-beam parameter, ξy)∗;)
25A ∗ @
41@

Luminosities under bunch-current limitations• The luminosities under these bunch-current limitations were estimated by H.
Nakayama and K. Nakamura.
• Reported in MDI meeting, IR technical meeting, and LTOP meeting.
• Here, the maximum luminosity was searched by scanning Nb (500~2500) for each βy*.
• Assumptions:
Background does not matter.
Beam-beam parameter (ξy) and emittance (εy) are constant (no dependence on βy*).
Beam lifetime is determined by Touschek lifetime (due to dynamic aperture).
'$( ) 2.59 A
Beam current ratio of HER to LER is free.

• The calculation is not astrict simulation, butwill give someguideline of achievable
luminosities underthese limitations.

Luminosity
limited by
RF power

Luminosity
limited bybeam-beameffectLuminosity
limited by
TMCILuminosity [cm-2s-1]

•
•
•
•

beam-beam
RF power
TMCI

1663

0.075

Max. beam currents
Bunch lengthMax. number of bunches
Vertical emittanceLER ver. beam-beam
parameter

3.6 10I
Lifetime parameter1.2 10J-EF
Inj. efficiency
G$
G -EF 0.8
-EF
-EF
Inj.
bunch
charge
N$
N
4 nC
-EF
-EF
*#$
*#
2 Inj. number of bunches

Inj. power

βy* [mm]

D ($ )
H$H-

Max.

*#
2021/9/2

Luminosity
limited byinjectionpower' ( ) 1.87 A;< 6.5 mm*#( ) 2500
=
20 pm

-EF

Max.
luminosity
under alllimitations

-EF

62$

62

"$1 2325 Hz Inj. repetition rate

2 mA

" 1 232 mA"$+(,-

1.4 mA " +(,-

1.5 mA

Hardware limit

42

TMCI limit

Luminosities under bunch-current limitations• The maximum luminosities before and after LS2 were estimated using possible
parameters.
• Assumptions: full-power injection, that is, 4 nc/bunch, 2 bunches, 25 Hz injection with anefficiency of 80%. (After Linac upgrade)• Designed vertical emittance (No TMCI limit), No background limit, Only Touschek lifetime.

'$( )Before LS2Luminosity [cm-2s-1]•

Before LS2(βy* ≥ 0.5 mm), L = 1.9x1035 [cm-2s-1]

beam-beam

RF power

D ($ )

Inj. power

Min. L

2021/9/2

βy* [mm]"$1 23"$+(,-

0.075
3.6

10

H-

1.2

10J

-EF

1663

After LS2

H$G$
-EF
N$
-EF
*#$

'$( )

2.59 A'
1.87 A;< 6.5 mm*#( ) 2500
=
20 pm

TMCI

*#

After LS2(βy* ≥ 0.3 mm), L = 2.3x1035 [cm-2s-1]( )I

G -EF 0.8
N-EF 4 nC
-EF
*#
2

62$

-EF

62

2 mA

" 1 23-EF

1.4 mA " +(,-

25 Hz
2 mA
1.5 mA

Luminosity [cm-2s-1]•

RF power
beam-beam

TMCI
Inj. power

1980'
2.04 A;< 6.5 mm*#( ) 2500=
10 pm
D ($ )

3.6

10I

H-

1.2

10J

-EF

G -EF 0.8
N-EF 4 nC
-EF
*#
2

-EF

62

-EF

25 Hz

2 mA " 1 23
1.4 mA " +(,-

2 mA

62$

βy* [mm]"$1 23"$+(,-

0.081

H$G$
-EF
N$
-EF
*#$

Min. L
*#2.82 A( )43

1.5 mA

Luminosities under bunch-current limitations• The maximum luminosities before and after LS2 were calculated using possible
parameters.
• Assumptions: full-power injection, that is, 4 nc/bunch, 2 bunches, 25 Hz injection with anefficiency of 80%. (After Linac upgrade)• No background limit, Only Touschek lifetime.

• Larger εy'$( )Before LS2Luminosity [cm-2s-1]•

Before LS2(βy* ≥ 0.5 mm), L = 1.4x1035 [cm-2s-1]

D ($ )RF power
Inj. power

H$H-EF

G$
-EF
N$
-EF
*#$

Min. L-EF*#
2021/9/2

1800

0.04
3.6

10I

1.2

10J

G -EF 0.8
N-EF 4 nC
-EF
*#
2
25 Hz

"$1 232 mA " 1 23

2 mA"$+(,-

1.4 mA " +(,-

1.5 mA62'$( )After LS2

-EF

62$

βy* [mm]2.59 A

1.87 A;< 6.5 mm*#( ) 2500=
60 pm

beam-beam

TMCI

After LS2(βy* ≥ 0.3 mm), L = 1.9x1035 [cm-2s-1]'( )Luminosity [cm-2s-1]•

beam-beam

2.04 A;< 6.5 mm*#( ) 2500=
30 pm

RF power
TMCI

Inj. power

1721

D ($ )
H$H-"$1 23"$+(,-

3.6

10I

1.2

10J

G -EF 0.8
N-EF 4 nC
-EF
*#
2

-EF

62

-EF

25 Hz

2 mA " 1 23
1.4 mA " +(,44

2 mA

62$

βy* [mm]

0.05

-EF

G$
-EF
N$
-EF
*#$

Min. L
*#2.82 A'( )1.5 mA

Luminosities under bunch-current limitations• The maximum luminosities before and after LS2 were calculated using possible
parameters.
• Assumptions: full-power injection, that is, 4 nc/bunch, 2 bunches, 25 Hz injection with anefficiency of 80%. (After Linac upgrade)• No background limit, Only Touschek lifetime.

• Larger εy, lower TMCI limit'$( )Before LS2Luminosity [cm-2s-1]•

Before LS2(βy* ≥ 0.5 mm), L = 1.2x1035 [cm-2s-1]

D ($ )RF power
Inj. power

H$H-EF

G$
-EF
N$
-EF
*#$

Min. L-EF*#
2021/9/2

1805

62$

βy* [mm]2.59 A

0.04
I

3.6

10

1.2

10J

G -EF 0.8
N-EF 4 nC
-EF
*#
2
-EF

62

'$( )

After LS2

1.87 A;< 6.5 mm*#( ) 2500=
60 pm

beam-beam

TMCI

After LS2(βy* ≥ 0.3 mm), L = 1.8x1035 [cm-2s-1]

'( )

25 Hz

"$1 232 mA " 1 23

2 mA"$+(,-

1.0 mA " +(,-

1.2 mA

Luminosity [cm-2s-1]•

beam-beam

RF power
TMCI

Inj. power1721

by* [mm]

D ($ )"$1 23"$+(,-

0.05

H$-

3.6

10I

H-

1.2

10J

-EF

G -EF 0.8
N-EF 4 nC
-EF
*#
2

62$

-EF

62

-EF

25 Hz

2 mA

" 1 23

2 mA

G$
-EF
N$
-EF
*#$

Min. L
*#2.82 A' ( ) 2.04 A;< 6.5 mm*#( ) 2500=
30 pm

1.0 mA " +(,451.2 mA

Luminosities under bunch-current limitations• The maximum luminosities before and after LS2 were calculated using possible
parameters.
• Assumptions: full-power injection, that is, 4 nc/bunch, 2 bunches, 25 Hz injection with anefficiency of 80%. (After Linac upgrade)• No background limit, Only Touschek lifetime.

• Larger εy, much lower TMCI limit (LER)'$( )Before LS2Luminosity [cm-2s-1]•

Before LS2(βy* ≥ 0.5 mm), L = 1.0x1035 [cm-2s-1]

D ($ )RF power
TMCI
Inj. power

H$H-

0.04
10

1.2

10J

-EF

Min. L

2021/9/2

1827

25 Hz

"$1 232 mA " 1 23

2 mA"$+(,-" +(,-

62$

βy* [mm]

G -EF 0.8
N-EF 4 nC
-EF
*#
2
-EF

-EF

*#

I

3.6

G$
-EF
N$
-EF
*#$

0.8 mA62'$( )Before LS21.87 A;< 6.5 mm*#( ) 2500=
60 pm

beam-beam

Before LS2(βy* ≥ 0.5 mm), L = 1.2x1035 [cm-2s-1]

2.59 A'( )1.2 mA

Luminosity [cm-2s-1]•'
1.87 A;< 6.5 mm*#( ) 2500=
60 pm

beam-beam

D ($ )RF power
TMCI

Inj. power

1805

H$H-

3.6

10I

1.2

10J

G -EF 0.8
N-EF 4 nC
-EF
*#
2

-EF

62

-EF

25 Hz

"$1 232 mA " 1 23

2 mA"$+(,-

1.0 mA " +(,-

1.2 mA62$

βy* [mm]

0.04

-EF

G$
-EF
N$
-EF
*#$

Min. L
*#2.59 A( )46

Trial re-estimation of luminosity profile• Long-term luminosity profile was re-estimated based on recent findings, that is,luminosities under bunch-current limitations, various countermeasures proposed sofar, and also recent operation experiences.
• Assumptions for re-estimation: Before LS2(1) Injection power reaches to the designed one (4 nc/bunch, 2 bunch injection, 25 Hz, injection
efficiency =0.8).
(2) LER beam lifetime will be 1.5 times higher than the present owing to the perfect matching.
(3) TMCI is improved by a factor of 1.5.
(4) Emittance will be improved to 20 pm. (TMCI limit might be not so important in this case)(5) Beam lifetime will be limited by the Touschek effect. Actually, there will be other factors.
(6) βy* can be squeezed to 0.5 mm (as before)(7) Maximum luminosity will be ~2x1035 cm-1s-1. (Cf. ~3x1035 MEXT RM)(8) Operation efficiency will be 0.6, expecting some improvement.
(9) LS1 will be from July 2022 to May 2023.
(10) Eight months operation per year basically.
(11) LS2 will start from July 2026.
(12)Effective operation day is 28 days per month considering two maintenance days. It is assumed
to be 20 days for months just after long break and those including βy*squeezing.
2021/9/2

47

Trial re-estimation of luminosity profile• Assumptions for re-estimation: After LS2(1) Injection power is already the designed one (4 nc/bunch, 2 bunch injection, 25 Hz, injection
efficiency =0.8).
(2) RF-system will be partially upgraded.
(3) βy*can be squeezed to down to 0.3 mm (as before)(4) Beam lifetime will be limited by the Touschek effect.
(5) LER beam lifetime will be 1.5 times higher than the present owing to the perfect matching.
(6) QCSR beam pipe aperture will be enlarged. TMCI is improved by a factor of 1.5.
(7) Emittance will be improved to 10 pm. (TMCI limit might be not so important in this case)(8) Maximum luminosity is ~3x1035 cm-1s-1. (Cf. MEXT RM assumed x2 luminosity upgrade)(9) Operation efficiency will be 0.6, expecting some improvement.
(10) Eight months operation per year basically.
(11) LS2 will be from July 2026 to September 2027, 15 months.
(12) Effective operation day is 28 days per month considering two maintenance days. It is
assumed to be 20 days for months just after long break and those including by*squeezing.
(13) After LS2, starting βy* will be 3 mm. It takes one year to recover the machine performance
before LS2 with βy* = 0.5 mm. It will take around two more years to squeeze βy* to around 0.3
mm and to achieve the goal luminosity.
2021/9/2

48

Luminosities under bunch-current limitations• The maximum luminosities before and after LS2 were estimated using possible
parameters.
• Assumptions: full-power injection, that is, 4 nc/bunch, 2 bunches, 25 Hz injection with anefficiency of 80%. (After Linac upgrade)• Designed vertical emittance (No TMCI limit), No background limit, Only Touschek lifetime.

• Perfect match'$( )Before LS2Luminosity [cm-2s-1]•

Before LS2(βy* ≥ 0.5 mm), L = 2.3x1035 [cm-2s-1]

beam-beam

RF power

D ($ )

Inj. power

Min. L

5.4

H-

1.2

10J

-EF

62$

βy* [mm]"$1 23"$+(,-

2021/9/2

0.075
10I

-EF

1663

After LS2

H$G$
-EF
N$
-EF
*#$

'$( )

2.59 A'
1.87 A;< 6.5 mm*#( ) 2500
=
20 pm

TMCI

*#

After LS2(βy* ≥ 0.3 mm), L = 2.8x1035 [cm-2s-1]( )G -EF 0.8
N-EF 4 nC
-EF
*#
2
-EF

62

2 mA " 1 23
1.4 mA " +(,-

25 Hz
2 mA
1.5 mA

Luminosity [cm-2s-1]•

RF power
beam-beam

TMCI
Inj. power

*#

1988

D ($ )

5.4

10I

H-

1.2

10J

-EF

G -EF 0.8
N-EF 4 nC
-EF
*#
2

-EF

62

-EF

25 Hz

2 mA " 1 23
1.4 mA " +(,49

2 mA

62$

βy* [mm]"$1 23"$+(,-

0.081

H$G$
-EF
N$
-EF
*#$

Min. L

2.82 A' ( ) 2.04 A;< 6.5 mm*#( ) 2500=
10 pm

1.5 mATrial re-estimation of luminosity profile• Re-estimated luminosity profile under new limitations.
• Presented in RM2020, Re-estimated w/ and w/o LS2
Lp [x1034 cm-2s-1]

βy* [mm]Int. L [fb-1] (Delivered)

RM2020Re-estimatedw/ LS2

RM2020Re-estimatedw/ LS2Re-estimatedw/o LS2

Re-estimatedw/o LS2
Re-estimatedw/o LS2

Re-estimatedw/ LS2

RM2020• The estimated luminosity is lower than expected considering various limitations withthe countermeasures discusses so far.
• For the case of upgrade option #3, the intermediate upgrade of IR around 2026 seems noteffective compared to the case without the upgrade from a viewpoint of int. luminosity.

• We continue to find more effective measures, not only limiting to IR but also including
MR other parts and Linac.
2021/9/2

50

Luminosities under bunch-current limitations• Present parameters (Y. Ohnishi, 2021/7, BPAC)

2021/9/2

51

Luminosities under bunch-current limitations• Luminosity under present condition• Almost limited by injection power (beam lifetime).
L = 3.7x1034 cm-2s-1 (I+= 970 mA, I-=1020 mA)••

L = 1.9x1035 cm-2s-1

Before LS2

beam-beam
TMCI
RF power
Inj. power

beam-beam

Luminosity [cm-2s-1]

Luminosity [cm-2s-1]

Present

RF power
Inj. power
TMCI
Min.

Min.
*#

1013 βy* [mm]*#'$( ) 2.59 A ' ( ) 1.87 A ;< 6.5 mm *#( ) 2500=
90 pm D ($ ) 0.045 H$- 3.6 10I H - 1.2 10J
-EF

-EF

-EF

1.8 nC *#$G$

0.6 N$

G -EF

0.3

N-EF

"$+(,-

1.0 mA " +(,-

2021/9/2

1.2 nC

-EF
*#

-EF
2 62$

12.5 Hz

-EF

1 62
25 Hz
1 23
" 1 23"2mA
1.5 mA $

2 mA

1663

βy* [mm]'$( ) 2.59 A '( ) 1.87 A ;< 6.5 mm *#( ) 2500=
20 pm D ($ ) 0.075 H$- 3.6 10I H - 1.2 10J
-EF
-EF
-EF
-EF
2 62$
G$
0.8 N$
4 nC *#$
25 Hz
G -EF
"$+(,-

0.8 N-EF 4 nC *#-EF 2 62-EF 25 Hz
1.4 mA " +(,- 1.5 mA "$1 23 2 mA " 1 23

2 mA

52

Luminosities under bunch-current limitations• Present condition + Full injection power• Present condition

Luminosity [cm-2s-1]

Present
Luminosity [cm-2s-1]

beam-beam

RF power
TMCI
Inj. power

beam-beam
TMCI
RF power
Inj. power
Min.

Min.
*#

1493

'$( ) 2.59 A ' ( ) 1.87 A ;< 6.5 mm *#( ) 2500=
90 pm D ($ ) 0.045 H$- 3.6 10I H - 1.2 10J'$( ) 2.59 A '( ) 1.87 A ;< 6.5 mm *#( ) 2500=
90 pm D ($ ) 0.045 H$- 3.6 10I H - 1.2 10J
-EF

•

-EF

G$

0.8 N$

4nC

G -EF

0.8

N-EF

"$+(,-

1.0 mA " +(,-

4 nC

-EF

*#$

-EF
2 62$

-EF
*#

-EF
62

2
1.5 mA "$1 23

-EF

G$

25 Hz

25 Hz
2. mA " 1 23

2 mA

L = 1x1035 cm-2s-1 (I+=1490 mA, I-=1870 mA)

2021/9/2

1013 βy* [mm]*#βy* [mm]•-EF

0.6 N$-EF

1.8 nC *#$G -EF

0.3 N-EF"$+(,-

1.0 mA " +(,-

1.2 nC

-EF
*#

-EF
2 62$

1
1.5 mA "$1 23

12.5 Hz

-EF
62

2 mA

25 Hz
" 1 232 mA

L = 3.7x1034 cm-2s-1 (I+=970 mA, I-=1020 mA)
53

Luminosities under bunch-current limitations• Present condition + Full injection power +Higher TMCI limit

RF power
TMCI

beam-beam

Luminosity [cm-2s-1]

Luminosity [cm-2s-1]

beam-beam• Present condition + Full injection power

Inj. power

RF power
TMCI
Inj. power

Min.
*#

1316

Min.
*#

βy* [mm]'$( ) 2.59 A '( ) 1.87 A ;< 6.5 mm *#( ) 2500=
90 pm D ($ ) 0.045 H$- 3.6 10I H - 1.2 10J
-EF

•

-EF

4 nC

*#$

-EF

-EF
2 62$

4 nC

-EF
*#

-EF
62

G$

0.8 N$

G -EF

0.8

N-EF

"$+(,-

1.4 mA " +(,-

2
1.5 mA "$1 23

βy* [mm]'$( ) 2.59 A '( ) 1.87 A ;< 6.5 mm *#( ) 2500=
90 pm D ($ ) 0.045 H$- 3.6 10I H - 1.2 10J
-EF

-EF

4 nC

*#$

-EF

-EF
2 62$

4 nC

-EF
*#

-EF
62

25 Hz

G$

0.8 N$

25 Hz
2 mA " 1 23

G -EF

0.8

N-EF

"$+(,-

1.0 mA " +(,-2 mA

L = 1.4x1035 cm-2s-1 (I+=1840 mA, I-=1870 mA)

2021/9/2

1493

•

2
1.5 mA "$1 23

25 Hz

25 Hz
2 mA " 1 23

2 mA

L = 1x1035 cm-2s-1 (I+=1490 mA, I-=1870 mA)
54

Luminosities under bunch-current limitations• Present condition + Full injection power,
higher TMCI limit + lower emittance(higher b-b parameter)• Present condition + Full injection power +higher TMCI limit

RF power

TMCI

beam-beam

Luminosity [cm-2s-1]

Luminosity [cm-2s-1]

beam-beam

Inj. power

RF power
Inj. power

TMCI

Min.
*#

1663

Min.
*#

βy* [mm]'$( ) 2.59 A '( ) 1.87 A ;< 6.5 mm *#( ) 2500=
20 pm D ($ ) 0.075 H$- 3.6 10I H - 1.2 10J
-EF

G$

G -EF
"$+(,-•-EF

24nC *#$

-EF

-EF
2 62$

0.8 N-EF

-EF
*#

-EF
62

0.8 N$
1.4 mA

4 nC" +(,-

1.5 mA2"$1 23

-EF

G$

G -EF

2021/9/2"$+(,-2 mA

L = 1.9x1035 cm-2s-1 (I+=1460 mA, I-=1870 mA)

βy* [mm]'$( ) 2.59 A '( ) 1.87 A ;< 6.5 mm *#( ) 2500=
90 pm D ($ ) 0.045 H$- 3.6 10I H - 1.2 10J

25 Hz

25 Hz
2 mA " 1 23

1316

•

-EF

24nC *#$

-EF

-EF
2 62$

0.8 N-EF

-EF
*#

2 62

0.8 N$
1.4 mA

4 nC" +(,-

1.5 mA

25 Hz-EF"$1 2325 Hz
2 mA " 1 23

2 mA

L = 1.4x1035 cm-2s-1 (I+=1840 mA, I-=1870 mA)
55

Trial re-estimation of luminosity profile• Revised luminosity profile• Revised w/ LS2 and Revised w/o LS2

Revisedw/ LS2

Revisedw/o LS2

Revisedw/ LS2
Revisedw/o LS2

Revisedw/o LS2

2021/9/2

Revisedw/ LS256

Trial re-estimation of luminosity profile• Revised luminosity profile• Ref. Revised w/ LS2 (two times higher Luminosity after LS2) and Revised w/o LS2

Revisedw/ LS2

Revisedw/ LS2
Revisedw/o LS2

Revisedw/ LS2
Revisedw/o LS2

Revisedw/o LS2• If we could boost up the luminosity to the twice of that before LS2 (~4.6x1035 cm-2s-1), theintegrated luminosity will be almost the same around 2033.

2021/9/2

57

Countermeasures discussed so far• For reference, proposed countermeasures after LS2 (~2031?)• Still preliminary discussion
Aim

Possible
Expected improvement
countermeasures
Large scale QCS andalso Belle II modification LER beam lifetime x ~2.2
(Option #8)

Improvedynamic
aperture
Increase
Linac upgrade beyond
injection power
designed specification(efficiency)

Injectin power x ~2?

Ready status

LS1

LS2

2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031~

Need further simulation
Need further
invesitgation• With these countermeasures• L = ~2x1035 cm-2s-1  ~4x1035 cm-2s-1
IR modification (option #8) including Belle II (SVD etc.)

2021/9/2

58

Trial re-estimation of luminosity profile• With perfect match• LER lifetime x1.5

• With perfect match• If charge of injection beam x2
L = 4.1x1035 cm-2s-1 (I+=1740 mA, I-=2040 mA)
beam-beam•

L = 2.8x1035 cm-2s-1 (I+=1380 mA, I-=2040 mA)

After LS2

After LS2

Luminosity [cm-2s-1]

RF power
Inj. power

TMCI
Min.

RF power

Luminosity [cm-2s-1]•

beam-beam
Inj. power
TMCI

Min.
*#

1840

βy* [mm]*#'$( ) 2.82 A ' ( ) 2.04 A ;< 6.5 mm *#( ) 2500=
10 pm D ($ ) 0.081 H$- 5.4 10I H - 1.2 10J
-EF

G$
G

-EF

"$+(,--EF

0.8 N$
0.8 N-EF

1.4 mA

8 nC

*#$

-EF

-EF
2 62$

8 nC

-EF
*#

-EF
62

" +(,-

2

1.5 mA "$1 23

-EF

-EF

4nC

*#$

-EF

-EF
2 62$

4 nC

-EF
*#

2 62

G$

0.8 N$

25 Hz
2 mA " 1 23

G -EF

0.8

N-EF

"$+(,-

1.4 mA " +(,-• The same effect for twice longer beam lifetime
2021/9/2'$( ) 2.82 A ' ( ) 2.04 A ;< 6.5 mm *#( ) 2500=
10 pm D ($ ) 0.081 H$- 5.4 10I H - 1.2 10J

25 Hz
2 mA

1988 βy* [mm]1.5 mA "$1 23

25 Hz

-EF

25 Hz
2 mA " 1 23

2 mA
59

Trial re-estimation of luminosity profile• Re-estimated luminosity profile• If we could have a long shutdown around 2031 and boost up the boost up the luminosity by afactor of 2, from ~2x1035 to =~4x1035 cm-2s-1;
Lp [x1034 cm-2s-1]

βy* [mm]Int. L [fb-1] (Delivered)Re-estimatedRe-estimatedRe-estimatedRe-estimatedw/o LS2

Re-estimatedw/o LS2

Re-estimatedw/o LS2• We need to continue to search effective measures like that.

2021/9/2

60

Appendix E: Task force

2021/9/2

61

Task force• Members• ARC members prepared a list of possible candidates in June, 2021, following therequirement from the management of the KEK Accelerator Lab. and B promotion
office (BPO).
• Initial members have been identified through the discussion with KEKB
commissioning team.
• Coordinator: M. Masuzawa (KEK)• More members who have required expertise and strong interest are welcome.
International Task Force members
2021/7/27
International members
Maria Enrica Biagini
Georg Hoffstaetter
Evgeny Levichev
Mark Palmer
Yunhai Cai
Rogelio Tomas
Pantaleo Raimondi
Katsunobu Oide

2021/9/2

INFN
Cornell
BINP
BNL
SLAC
CERN
ESRF
CERN/KEKKEK ACCL members
Mika Maszawa (Chair)
Yukiyoshi Ohnishi
Akio Morita
Hiroshi Sugimoto
Renjun Yang
Haruyo Koiso
Yoshihiro Funakoshi
Tsukasa Miyajima
Kazuhito Ohmi
Demin Zhou
Kentaro Harada

SKEKB
SKEKB
SKEKB
SKEKB
SKEKB
SKEKB
SKEKB
SKEKB
SKEKB
SKEKB
KEK-PF

Belle II members
Hiroyuki Nakayama
Francesco Forti

Belle II
Belle IIBPO members
Masanori Yamauchi
Tadashi Koseki
Makoto Tobiyama
Kazuro Furukawa
Kyo Shibata
Yusuke Suetsugu

KEK
ACCL
SKEKB
SKEKB
SKEKB
SKEKB

Naohito Saito
Shoji Uno
Yutaka Ushiroda
Toru Iijima
Kodai Matsuoka

IPNS
Belle II
Belle II
Belle II
Belle II

62

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 II detectors.
• 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 ofaccelerator components.
• Consider longer-term alternative idea to achieve ~6x1035 cm-2 s-1 or more, even bylargely modifying the IR and the Belle II detector.

2021/9/2

63

Task force• Standing position and main role
• Conceptual diagram (Draft)

ARC
Review
Beamcommissioning,studies

ITF

Acc. hardware
group
Belle II

“Hands on” work is required• Proposals of new ideas• Countermeasures against challenges• Study plans, commissioning plans (strategies)• Simulations• Beam-beam, optics, instabilities, etc.
• Participation in the commissioning• Remote for the time being, on site (after Covid-19)• Discussions and comments on various issues
2021/9/2

64

Task force• Activity period• Coming one year, before the LS1.

• Rough schedule• (Online) meeting per month basically.
• Meetings are basically open, but may occasionally have closed sessions.
• Special review by ARC per ~6 months.
• Final report is to be submitted by the end of July, 2022.
2021
Meeting
Review by Arc

7

8

〇

〇

Kick off

9
〇

2022

10

11

12

〇

〇

〇

1
〇

2

3

〇

〇

4
△

As
needed

5

6

〇

〇

7
〇

ReportMachine operation

2021/9/2

65

Task force• Activity period• Coming one year, before the LS1.

• Rough schedule• (Online) meeting per month basically.
• Meetings are basically open, but may occasionally have closed sessions.
• Special review by ARC per ~6 months.
• Final report is to be submitted by the end of July, 2022.
2021
Meeting
Review by Arc

7

8

〇

〇

Kick off

9
〇

2022

10

11

12

〇

〇

〇

1
〇

2

3

〇

〇

4
△

As
needed

5

6

〇

〇

7
〇

ReportMachine operation

2021/9/2

66

Task force• Subgroups (as of August 2021)
1) beam-beam• Contact person : Demin Zhou <dmzhou@post.kek.jp>• Sub : Kazuhito Ohmi <ohmi@post.kek.jp>• Mailing list skb-itf-bb@ml.post.kek.jp

2) optics• Contact person : Akio Morita <akio.morita@kek.jp>• Sub : Haruyo Koiso <haruyo.koiso@kek.jp>• Mailing list skb-itf-opt@ml.post.kek.jp

3) TMCI and impedance matters• Contact person: Rogelio Tomas Garcia• Sub: Takuya Ishibashi• Mailing list skb-itf-tmci@ml.post.kek.jp2021/9/2

67

Backup

2021/9/2

68

Near-term operation plan and luminosity profile• Operation schedule (from the last BPAC, 2021/3/1)• FY2021• Now we finished 2021b run, and are in the summer shutdown• 2021c run will start on 19th October, and end 23rd December (fixed).
• 2022a run will start on 9th February, and end at the end of March (not fixed, depends
on budget, etc.). Then the total operation period will be ~7 months.
Now
2021
4

FY2021

2022
5

6

7

8

9

10

2021b
4/1

12

1

2

7/5

10/19

~2.2M

10

11

12/23

2022
6

7

8

9

12

1

2

3
Total

2022b

~3.5M

4/1

~3.5M/y

LS1

7/15

2023
FY2023

4

2024
5

6

7

8

9

10

2023b

LS1

2021/9/2

Total~1.7M ~7.0M/y

2/9

2023
5

3
2022a

2021c

~3.1M
4

FY202211

5/15 ~2M

11

12

1

2

7/15

10/9

~2.5M

3
2024a

2023c
12/22

2/9

Total

~1.7M ~6.2M/y69

Near-term operation plan and luminosity profile• Operation schedule (from the last BPAC, 2021/3/1)• FY2022 (Not yet fixed)• 2022b run will start on 1st April, and end in the middle of July
• The PXD exchange work (LS1) is scheduled to start from July, but it is fluid dependingon the situations of COVID-19 and also budget.
• A possible schedule is to start LS1 from January, 2023.
• Here we assume the present schedule, then the total operation period will be ~3.5
months.
2021
4

FY2021

2022
5

6

7

8

9

10

2021b
4/1

12

1

2

7/5

10/19

~2.2M

10

11

12/23

2022
6

7

8

9

12

1

2

3
Total

2022b

~3.5M

4/1

~3.5M/y

LS1

7/15

2023
FY2023

4

2024
5

6

7

8

9

10

2023b

LS1

2021/9/2

Total~1.7M ~7.0M/y

2/9

2023
5

3
2022a

2021c

~3.1M
4

FY202211

5/15 ~2M

11

12

1

2

7/15

10/9

~2.5M

3
2024a

2023c
12/22

2/9

Total

~1.7M ~6.2M/y70

Results so far• Results of 2020/4/1~2021/7/5 (Blue pints)
FY2020Lp [x1034 cm-2s-1]

Max. I [A]

βy* [mm]
FY2021

FY2022

FY2020

FY2021~1.6

FY2022

FY2020

FY2021

Int. L [fb-1] (Delivered)

FY2022

FY2020

FY2021

~730

~1.2
~1.1

~4.8
~3.8

~1

LS1

•
•
•
•
•
•
•
2021/9/2

FY2022

~8

LS1

~410
~280

LS1

LS1

βy* = 1 mm
Max. luminosity = 3.12x1034 cm-2s-1 (5/17)
Int. luminosity (Delivered, 2019c ~ 2021/7/5) = 235 fb-1
Max. beam current '$ ' = 0.83 A (4/20) [HV on] (0.95 A (4/20) [HV off])Max. 7-days int. luminosity (Recorded) = 12.4 fb-1 (5/14〜5/20)
Max. daily int. luminosity (Recorded) = 1964 pb-1 (5/18)
All values exceeded the records of KEKB
71

Works planed in this summer shutdown• Regular maintenance (Water flow meters, Power supplies for RF and magnets, etc.
• Collimators• Replacement of 2 collimator heads (HER).
• Upgrade of driving device of 2 collimators (HER)• Installation of new collimator heads with 3 mm Tantalum and graphite (at LER arc).
• Robust against damages from beam.

• Relocation of LER D02V1 collimators? (under discussion)• Exchange of the mirror and its folder of SR beam size monitor for LER.
• Installation of a HOM absorber at RF section (HER Nikko).
• BT• Installation of beam profile monitors with OTR screen.
• Installation of a beam shutter in LER injection line.

• Installation of a strip-line kicker into RTL line at DR• Anti-aging measures• Replacement of HV (66 kV and 6.6 kV) power cables.
• Repair of water leak from roof of some power stations.
• Replacement of some old water pumps.
2021/9/2

72

Summaries of near-term operation plan
• Near-term operation plan and luminosity profile• The operation is in progressing almost as planned.
• Seven months operation is planed in this fiscal year.
• Budget request for FY2022 is on going.
• The maximum beam currents, the peak luminosity are almost as expected.
• Number of bunches was increased to 1272.
• We are in the midst of replacing the highest records.
• Integrated luminosity, however, was ~70% of the expected one.
• Operation efficiency is around 0.5, not 0.65.
• If the machine is stable, the operation efficiency of over 0.65 is achievable.
• We will basically keep the present operation plan and luminosity profile, making best effort tocatch up with the target values.

2021/9/2

73

Designed luminosity• Assumptions in the present luminosity profile: Before LS2
The maximum beam-beam parameter (D ($ ) ) was assumed to be 0.075.
βy* will be squeezed to 0.5 mm before LS2.
Luminosity was determined by the beam-beam parameter.
Beam currents were determined by RF power.
D ($ )

0.075
?@
25A

>

'$( )

; ∗∓ '@ D @ ?@ '@ D @
1B ∗
~
∗
;)
25A ∗ @@

2.59 A , ' ( )1.87 A• At βy*=0.5 mm,
( )
##

•
2021/9/2

3.4

10

Tcm s

1
*# "#$ "#∗445 67 sin:, ;<=Luminosity [cm-2s-1]

•
•
•
•

beam-beamU*# 1565 ;< 6.5 TmmU"#$ 1.65 TmA bunch U"#
1.19 TmA bunch U=
19.7 TpmU

by* [mm]'$( )2.59 A , ' ( )1.87 AD ($ )

*#( )

2500

0.075

74

Designed luminosity• Assumptions in the present luminosity profile: After LS2
The maximum beam-beam parameter (D ($ ) ) was assumed to be 0.081.
βy* will be squeezed to 0.3 mm finally.
Luminosity was determined by the beam-beam parameter.
Beam currents were determined by RF power. Need partial RF-system upgrade.
D ($ )

0.081
?@
25A

>

'$( )

; ∗∓ '@ D @ ?@ '@ D @
1B ∗
~
∗
;)
25A ∗ @@

2.82 A , ' ( )2.04 A• At βy*=0.3 mm,
( )
##

•
2021/9/2

6.6

10

Tcm s

1
*# "#$ "#∗445 67 sin:, ;<=Luminosity [cm-2s-1]

•
•
•
•

beam-beamU*# 1761 ;< 6.5 TmmU"#$ 1.60 TmA bunch U"#
1.16 TmA bunch U=
10.8 TpmU

βy* [mm]'$( )2.82 A , ' ( )2.04 AD ($ )

0.081 *#( )

2500
75

End

2021/9/2

76