SuperKEKB MR LS1 Status（Progress after the previous B2GM）

Tetsuya Kobayashi (KEK)(on behalf of SuperKEK Accelerator Group)
B2GM 2023.6.5

1

Contents▼LS1 Status●Introduction- Challenges and Countermeasures- LS1 Schedule●Interaction Region (IR) @Tsukuba straight section●Non Linear Collimator (NLC) @Oho straight section●Other Works in MR▼Sudden Beam Loss (SBL)▼Summary
B2GM, June 5th 2023, T. Kobayashi

2

Challenges as a Luminosity Frontier Machine
shown in the previous B2GM by Shibata-san+ 6) Low injection efficiency especially in HER.
B2GM, June 5th 2023, T. Kobayashi

Y. Suetsugu (2021.09.02)
The 25th KEKB Accelerator Review Committee
3

Countermeasures against Challenges
shown in the previous B2GM by Shibata-san

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

During LS1
Done before LS1
Under consideration(It was found that it is not easy.)

Under consideration
During LS1(collimator head replacements)

B2GM, June 5th 2023, T. Kobayashi

Done before LS1
Under consideration
During LS1
During LS1 (Partially)
During LS1 (Partially)
During LS1 (Partially)4

Schedule• LS1 : ∼15 months from July 2022 to autumn 2023

Ceiling aseismic reinforcing work

• 2022b run stopped earlier than planned due to high electricity costs (22nd June), but LS1
major works began on 11th July as scheduled.
• Beam operation will restart from December 2023.

• Major works during LS1 other than accelerator upgrade:• Belle II maintenance and reinforcement••

Replacement of PXD and TOP MCP-PMTs, new IP beam pipes, and so on.
IR works are required, including QCS extraction & reinstallation, disassembly & reinstallation of magnets,
beam pipes, radiation shields, etc.

• Aseismic reinforcement of the ceiling at the laboratory buildings (Oho Lab. & Fuji Lab.)••

It took about 5 months and it could be done only during long shutdown.
During this work, we could not use ceiling crane required for NLC construction at Oho Lab.!!

S. Nakamura

LS1 schedule
Previous
B2GM
2023

2022

JFY2022

4

5

6

7

9

10

2022b run
Ceiling aseismic reinforcing work
2023

We are here now!!

JFY2023

8

4

5

6

7

8

9

11

12

1

2

3

Long Shutdown 1 (Accelerator upgrade)
Belle II maintenance & reinforcement

10

Long Shutdown 1 (Accelerator upgrade)
Belle II
maintenance &reinforcement

B2GM, June 5th 2023, T. Kobayashi

2024

11

12

1

2

3

2024a run2023c run

5

QCS @ Interaction Region (IR)(@Tsukuba Lab.)
QCS = final focusing superconducting magnet system for the interaction point
IRElectronbeam

Tsukuba lab. &Belle-II

Positronbeam

B2GM, June 5th 2023, T. Kobayashi

6Interaction Region (IR) @Tsukuba Lab.
• Major work items in accelerator tunnel:

Belle II•

Disassembly and reinstallation of concrete radiation shields•

Belle II maintenance & reinforcement work•

Disassembly and reinstallation of magnets, beam pipes for
QCS work•

QCS extraction & reinstallation•

QCSR cryostat leak test•

QCSR cryostat vacuum leak repair•

QCS cryostat modification

QCS movable platform

IR

Progressed works
from previous B2GM

QCS cryostat

Concrete radiation shieldPrevious B2GM
2023

2022
5

6

JFY20227

We are here now!!
4

5

8

9

6

JFY2023
QCS inspection
Belle II
maintenance & reinforcement

10

Magnet & beam pipe disassembly

Concrete shielddisassembly
Belle II work

2022b run

11

12

1

2

8

3

QCS cryostat
modification

QCS extraction
QCSR cryostat leak test

Belle II maintenance & reinforcement

2023
7

PositronbeamElectronbeam

IR (Tsukuba straight section)
4

Tsukuba lab.

2024
9

10

11

QCS reinstallation
Magnet & beam pipe reinstallation
Belle II work

B2GM, June 5th 2023, T. Kobayashi

12

1

2

3

Concrete shield reinstallation
2023c

2024a run
7

Disassembly of Concrete Radiation Shields@ Tsukuba Ex. Hall

Done July 2022

• Concrete radiation shields disassembly
Concrete radiation shields were temporarily removed for IR works.
• They will be reinstalled in November 2023.

IR

Tsukuba lab.

• To suppress background noise of Belle II, 2 concrete shields will be replaced with new ones.
• New shields will be delivered in March 2023.
This shield will be replaced with new one.
Electronbeam

Positronbeam

Concrete shield disassembly work
B2GM, June 5th 2023, T. Kobayashi

8Disassembly of MG & Beam Pipes
for QCS Extraction Done Sep. 2022
(Reported in the previous B2GM by Shibata-san)IR

Tsukuba lab.

• Disassembly of magnets & beam pipes for QCS extraction
To make space for QCS extraction, magnets and beam pipes were removed.
• For QCS cryostat work, some magnets and beam pipes on QCS movable platform
were also removed.
Magnets & beam pipes should be disassembled

QCS movable platform

Electronbeam

Positronbeam

IP

QCS extraction

QCS extraction

QCS movable platform

Disassembly work
B2GM, June 5th 2023, T. Kobayashi

9QCS Extraction

Done Sep. 2022

(Reported in the previous B2GM by Shibata-san)IR• QCS extraction

Tsukuba lab.

• RVC disassembly was performed by Belle II and SuperKEKB for the first time.
• RVC : Remote Vacuum Connection between IP bellows chambers and QCS beam pipes• DESY, who is RVC developer and has been in charge of RVC disassembly so far, also joined
the work online. Thank you very much for the kind work manual and cooperation!!
• Although camera for monitoring the RVC movement did not work, disassembly work went well.

• QCS extractions of both sides were completed successfully in one day!!

Electronbeam

Positronbeam

RVC lock flange of IP bellows chamber

K. Gadow(DESY)

RVC mechanism

Remotemanipulation
wheel

QCS extraction

B2GM, June 5th 2023, T. Kobayashi

10QCS Cryostat Modification(progress after the previous B2GM)• QCS cryostat modification• In order to reduce Belle II background noise,
the material at the tip of QCS cryostat was changed from W to SUS.
• QCSR front cap replacement• QCSL front plate replacement• In order to make more space for Belle II cables,
the tip of QCSR cryostat was changed to thinner one.
• QCSR cryostat modification including front cap replacement

IRElectronbeam

Tsukuba lab.

Positronbeam

BPM feedthroughBPM feedthroughQCS beam pipe

QCS beam pipe
To access QCS pipes & BPMs,
this part should be disassembled.

Y. ArimotoTo access QCS pipes & BPMs,
these windows should be open.

T. Oki

Original
New design

Y. Arimoto
QCSL front plate
replacement

QCSL

QCSR front cap
replacement

QCSR

B2GM, June 5th 2023, T. Kobayashi

11

QCS Cryostat Modification ( Feb. - Mar. 2023)
New QCS-L Front Plate (SUS)
was attached

QCS-L Front Plate (W)was removed

To reduce Belle II background noise,• QCS-L• Changed the material of thefront plate from tungsten to
stainless steel

Beam pipes

Beam pipes

To make more space for Belle II cables,• QCS-R• Replace the front cap

New QCS-R Front cap

with thinner one• Made of stainless steel
QCS-R Front cap
was replaced.

B2GM, June 5th 2023, T. Kobayashi

12

QCSR Sevice Cryostat Vacuum Leakadiabatic vacuum

was found in 2022

(As reported in the previous B2GM by Shibata-san)IR

Tsukuba lab.

• QCSR service cryostat• Pressure in QCSR service cryostat has been higher than that in QCSL.
• Residual gas analysis showed that vacuum leak has occurred in QCSR service cryostat.
• However, vacuum leak test before LS1 did not detect any vacuum leak.

• After QCS extraction, thorough vacuum leak test was performed.
• At last, the location of the vacuum leak was identified!!. (Oct. 2022)→ Repair work was progressed in this year.

This vacuum isfor thermal insulation
to keep superconducting(not in beam line).

Electronbeam

Positronbeam

Vacuum leak test work of QCSR service cryostat

Service Cryostat

Oct. 2022(for thermal insulation system)

B2GM, June 5th 2023, T. Kobayashi

13

Vacuum Leak Repair Work ( Mar. 2023 )• We opened the service cryostat at QCS-R andchecked the O-ring surface

QCS-R service cryostat• The fiber-like object was found on the surface of the
O-ring.

• We replaced the O-ring with the new one, cleaned

the groove and the flange surface, and reassembled
the cryostat.

• As the result of a helium leak test, It was confirmedthat the leak has successfully stopped.

8m

m

Fiber-like object

Permeation through O-ringO-ring
B2GM, June 5th 2023, T. Kobayashi

14New Concrete Shields for IR• To suppress background noise of Belle II,
two-concrete shields will be replaced with new ones.
• New concrete shields have been delivered in March 2023
• They will be reinstalled in mid September 2023.

New concrete shield waiting to be installed to IR

By using the new shields,
this opened space will befilled with concrete.

IR

Electronbeam

Tsukuba lab.

Positronbeam

H. Yamaoka

B2GM, June 5th 2023, T. Kobayashi

15Remaining works for IR• Remaining works in accelerator tunnel:

IR

Tsukuba lab.

• Belle II maintenance & reinforcement (∼ Sep 2023)• QCS periodical self-inspection (Jun 2023)• QCS reinstallation (Oct 2023)• Concrete shield reinstallation (Nov 2023)

PositronbeamElectronbeam• All works can be completed by the end of Nov 2023.
• It is required to coordinate the schedule with Belle II work and NLC construction.

IR (Tsukuba straight section)

Previous B2GM
2023

2022
4

5

6

7

JFY20228

We are here now!!
5

6

JFY2023

10

Magnet & beam pipe disassembly

Concrete shielddisassembly
Belle II work

2022b run

4

9

12

1

8

3

QCS cryostat
modification
Belle II maintenance & reinforcement

2023
7

2

QCS extraction
QCSR cryostat leak test
2024
9

10

QCS inspection
Belle II
maintenance & reinforcement

11

11

QCS reinstallation
Magnet & beam pipe reinstallation
Belle II work

B2GM, June 5th 2023, T. Kobayashi

12

1

2

3

Concrete shield reinstallation
2023c

2024a run16

Oho Straight Section
Tsukuba(Belle II)

Ohostraight section

D04
D05
Electronbeam
Positronbeam

B2GM, June 5th 2023, T. Kobayashi

17Oho Straight Section
Concrete radiation shield• Major work items in accelerator tunnel:

Tsukuba(Belle II)

D05 straight section

Ohostraight section• Disassembly and reinstallation of concreteradiation shields• Non Linear Collimator (NLC) construction (LER)• RF cavity@D05A replacement (LER) … done!
• Ceiling aseismic reinforcing work…done!
• Installation of new radiation shields for NLC

D04
D05

Positronbeam

Oho straight section (D05)
Previous
B2GM
2023

2022
4

JFY20225

6

7

Concrete shieldremoval

JFY2023

10

11

6

12

1

7

NLC construction @D05

3

RF cavity (@D05A)
replacement

Crane not available
Ceiling aseismic reinforcing work

82

NLC construction @D05

2023

We are here now!!
5

9

RF cavity inspection

2022b run

4

8

2024
9

10

11

12

1

2

3

New radiation shield
installation
2023c

2024a run

Concrete shieldreinstallation

B2GM, June 5th 2023, T. Kobayashi

18Concrete Shields Disassembly @Oho
• Concrete radiation shields disassembly (already done, July 2022)

Tsukuba (Belle II)• Concrete radiation shields were temporarily removed for NLC construction.
• They will be reinstalled in October 2023.

D04
D05

Oho
straight section• The concrete shields are placed outside Oho laboratory building,now

Positron
beam

Oho
Lab.

Disassembled concrete shield

Concrete shield disassembly work
B2GM, June 5th 2023, T. Kobayashi

19Non Linear
Collimator(NLC)
Installation
Non-linear collimator

In order to relax the transverse mode coupling instability (TMCI), NLC is applied to LER.

Non-linear collimator

Plan –Non-linear
collimator
at LEROHO section
Enlarge beam
size bynonlinearkick of the skew-sextupole

Tsukuba (Belle II) Enlarge beam size by nonlinear kick of the skew-sextupole• Scheme • Restore the[K.position.
Oide]−𝐼 size with the pair skew-sextupole placed at –I

D04

Oho
straight section• Could use smaller vertical betatron function at the vertical collimator.
• Restore
thelarger
sizecollimatorwith the• Better collimation
effect with muchgap. pair skew-sextupole placed at –I position.

• Could use smaller vertical betatron function at the vertical collimator.
D05• Better collimation effect with much larger collimator gap.
Positronbeam

NLC is installed at Oho D05 section in LER,
2
where
the optics satisfies the requirements for NLC
𝜋
∆𝜇𝑦 =
2

17

Oho straight section is optimum for NLC-installation.

B2GM, June 5th 2023, T. Kobayashi

20

NLC Composition (Re-configuration of Beam Line)@Oho Straight Section (downstream of D05 RF section)is continuing…
QFWOP_5← IP (Tsukuba)

QDWOP_6

We estimate that benefits of NLC outweigh the demerits of wiggler-reduction. (This section is only one candidate for the location of NLC)

Beforefor NLC configuration

Wiggler magnets were removed (done).

HER(e-) →LER(e+) ←After(e+) ←(installation done)

NLC Skew sextupole magnet
Quadrupole magnets were replaced.
& New collimator was installed.

New collimator (D05V1)

Skew sextupole magnet

New skew sextupole magnets will be installed in September
B2GM, June 5th 2023, T. Kobayashi

21Removal of Wiggler and Beam-Pipe• Wiggler magnets and beam pipe removal (already done)

Done in 2022

Tsukuba (Belle II)• Removed wiggler magnet and cable : 50 magnets and their cables
Double pole magnet (3 ton) : 20
Single pole magnet (2 ton) : 10
Half pole magnet (1.5 ton) : 20
Cables : 3 ton

D04
D05

• Removed beam pipe for wiggler magnet : 10 beam pipes• Disassembly procedure
•
•
•
•
•

Removal of wiggler magnet cables
Upper parts of wiggler magnets disassembly
Beam pipes removal
Upper parts of wiggler magnets reassembly
Wiggler magnets remova

Ohostraight section

•
•
•
•

Positronbeam

10 times

S. Nakamura

Wiggler beam pipe removal work
B2GM, June 5th 2023, T. Kobayashi

22

Magnet Re-Cabling for New Configuration

at D05 section

BeforeTwo power supplies drove 5 or 6 quadruple magnets, respectively.

QFWOP_5
QDWOP_6← IP (Tsukuba)
After

One power supply drives one or two magnets. → more power supplies are needed.
QFWOPQDWOP_2

QN8OP

QN6OP
QN5OP
QN7OP

QN3OP

QN1OP

S. Nakamura

QN2OP_2

for sextupole
Additionally new power supplies will be installed in September, and test operation of them will start in October.
Re-wiring works between the power supplies and magnets has done.
B2GM, June 5th 2023, T. Kobayashi

23

Remaining1: New Radiation Shield Installation
New Pb radiation shield is required to be installed for NLC← IP (Tsukuba)
BeforeWiggler magnets were removed.

HER(e-) →LER(e+) ←After

New Pb shields

5m

New collimator (D05V1)
A 5-m Pb radiation shield will be
installed at downstream side of
the new collimator,
in early to middle October.

Collimator

New Collimator

∼5 m
Pb/
SUS
∼50 mme+beam

New Pb radiation shield

B2GM, June 5th 2023, T. Kobayashi

24Remaining2: Concrete Shields Addition
The additional concrete shields will be install
to protect the OHO experimental hall from the radiation from the collimator.
Additional
concrete shields∼5 m

Collimator

Pb/
SUS∼50 mmNew Pb radiation shield
Y. Sakaki

concrete shields

After the reinstallation of the concrete shields,
additional concrete shields will be placed on top of theconventional concrete shields.

Image of installation of additional concrete shields↓ conventional concrete shields

These shields will be prepared by the middle of July and installed in November.
B2GM, June 5th 2023, T. Kobayashi

25Oho Straight Section
Tsukuba(Belle II)
Ohostraight section• Remaining works in accelerator tunnel:• NLC construction (will be completed by Sept. 2023)• New radiation shield installation (Oct.~ Nov. 2023)• Concrete shield reinstallation (Oct. 2023)

D04
D05

• All works will be completed in December 2023.
• Schedule is very tight.

Positronbeam

Oho straight section (D05)
Previous
B2GM
2023

2022
4

5

6

Concrete shieldremoval

JFY2023

5

9

10

11

6

NLC construction

12

1

7

3

RF cavity replacement

Crane not available
Ceiling aseismic reinforcing work

82

NLC construction2023

We are here now!!
4

8

RF cavity inspection

2022b run

JFY2022

7

2024
9

10

11

12

New radiation shield
installation
2023c

1

2

3

2024a run

Concrete shieldreinstallation

B2GM, June 5th 2023, T. Kobayashi

26

Other Works in MR

B2GM, June 5th 2023, T. Kobayashi

27

Other Major Works in MR during LS1• Robust collimator head (LER)
T. Ishibashi

MR•

As countermeasures against collimator destruction due to kicker-pulser
misfiring
•
•
•
•
•

Carbon collimator head

Replacement with carbon head of horizontal collimator D06H3
Relocation from D06H1 to D06H4
Carbon head production : ∼ March 2023 (done)
Head replacement : Spring ∼ Summer 2023
Collimator relocation : Spring ∼ Summer 2023

• New beam pipes at HER injection point for wide aperture•

For injection efficiency improvement••••

Y. Suetsugu
Old (narrow aperture) beam pipe
at HER injection point

Beam pipe design at HER injection is changed for wider aperture& New BPM will be applied for precise measurement of injected beam
New beam pipe production : ∼ March 2023 (done)
Beam pipe replacement : now ∼ Summer 2023
Septum baking : ∼ Summer 2023?

• RF cavity modification and replacement (LER) …..Done!
•DR

For stable operation with larger beam current••

Modification : Input coupler replacement, cooling power enhancement, coaxial line
modification, etc. (done)
Cavity replacement (D05A) : January ∼ February 2023 (done)• Vacuum seal replacement at RF section (DR)…..Done!
•

For pressure reduction•

Elastomer gaskets were replaced with metal gaskets for dummy pipe connections.(done)• DR Extraction kicker power supply modification and repair (DR)•For stable operation•

DR Ext. kicker

DR RF section

Modification : December 2022 ∼ August 2023

• And so on…

B2GM, June 5th 2023, T. Kobayashi

28

Change to

Robust Collimator Head (LER)• As countermeasures against collimator destruction due tokicker-pulser misfiring,• Replacement with carbon head of horizontal collimator D06H3.
• Collimator relocation from D06H1 (upstream of D06H3) to D06H4(downstream of D06H3) to collimate the beam passing through D06H3.

Extracted Head from D06H3
Contact Finger

D06H3 collimator
Structure of collimator
T. ISHIBASHI et al.
for horizontal (a) and vertical (b)replace

PHYS. REV. ACCEL. BEAMS 23, 053501 (2020)(in progress)

New Carbon Head(wider head for robustness)

Ta or W Heads
D06H4

For details of the collimators,
refer to “T. Ishibashi et al. Phys. Rev. Accel. Beams 23, 053501 (2020)”

B2GM, June 5th 2023, T. Kobayashi

relocated from D06H1

e+
beam
29

Damaged Collimator Head Replacement in progress
HER D01V1 collimatorHER D01V1

LER D06V1 collimator
LER D06V1
Structure of collimator
ISHIBASHIet al. (a) and vertical (b)for horizontal

PHYS. REV. ACCEL. BEAMS 23, 053501 (2020)

e+ beam

New Ti HeadTa Head
B2GM, June 5th 2023, T. Kobayashi

replace30

Sudden Beam Loss (SBL)
One of the major concerns for the operation

B2GM, June 5th 2023, T. Kobayashi

31Sudden Beam Loss (SBL)
An obstacle for high luminosity of 1035cm−2s−1 is sudden beam loss (SBL).
Horizontal Oribt● Frequently, (10~20% of all aborts)
the beam suddenly disappears just before the abort.
This is very rapid phenomenon within few turns.
(1-turn = revolution period = 10us)● The cause of SBL is still unknown.
● Harmful effects of SBL;

Vertical Orbit

Bunch Current

2 turns
60 us

Beam Loss● Damage to collimators and other accelerator components,● Quench of the final focusing superconducting magnets (QCS),● Large backgrounds to the Belle-II detector,● Inability to store high current due to beam abort.
→A task force was established to investigate and resolve the causes of SBL.

● We continue to review the data before LS1 from various aspects.

Beam Abort

Another ex. of SBL
Bunch Current

Beam Loss

2 turns
Beam Abort

B2GM, June 5th 2023, T. Kobayashi

32

SBL : Observation (more details)

Horizontal Orbit

Vertical Orbit● The orbit is changing < O(1mm) after the beam loss.
● No oscillations, which could be precursors to beam loss, are observed.
● Pressure bursts have been observed all over the place.
( They rarely occur in the same place except at the collimator section.)● Regarding the pressure of D06H3 and H1 collimators, there are rapid or
nonlinear increase of pressure depending on the beam current.
B2GM, June 5th 2023, T. Kobayashi

Bunch Current

60 us
Beam Loss

Abort

Pressure [Pa]

SBL

Time
Pressure [Pa]● The beam suddenly disappears just before the abort.
● Beam loss occurs in both HER and LER, but the damage to thehardware is particularly large when loss occurs in LER.
● We don't know if it will happen even with a single beam or low current
beam because we haven't operated for a long time.
● The starting point of beam loss depends on the tuning of the collimatorand is not limited to a specific location.
● Just before the beam loss begins, the orbit appears to move,but its value is small〜O(0.1 mm).

1mm

H-Collimators

Beam Current

33

Candidates for Reason of SBL(Supposition of the reasons: none of these candidates are proved)● Damage of vacuum component (RF Finger) @KEKB & PEP-II● Beam phase changes (beam energy losses) observed ms to several hundred µs before aborts.
→ The time scale differs from that of SBL.
● Abnormal temperature rise at bellows chambers had been observed and the catastrophic damages in the RFfinger had been confirmed. → We could not find that damage.
● Dust : Early stage @ SuperKEKB● Vacuum chambers were cleaned or tapped to remove as much dust as possible.
● Electron Cloud● SBL should be measured only in LER.→ SBL is also measured in the HER beam.
● Curious behavior of the pressure in D06H3 collimator may suggest the formation of a discharge or electron cloud.
● Simulations show that the electron density distribution changes with time and a maximum electron density is on
the order of 1E13/m3 to 1E14/m3 → How this relates to SBL?
● Fireball (Measured @ RF cavity):
Microparticle heated by beam-induced field may cause plasma-growth or vacuum arc at metal surface.
● The vacuum chamber is made of copper with low sublimation point and collimator head is made of tungsten or
tantalum with high sublimation point.
→ The situation has the potential for a fireball to be formed.
● This fireball hypothesis could explain SBL (~µs) due to the fast plasma evolution (~100 ns at the fastest)
B2GM, June 5th 2023, T. Kobayashi

34

Works during LS1 for SBL (in progress)● Replacing damaged collimator head.
● Copper coating of collimator heads.
● Applying an external magnetic field of 40G or higher to collimator head.
● Enhancement of monitors (acoustic sensor, loss monitor, beam oscillation recorder...) .
● Simulations of plasma and beam interactions (Study for fireball hypothesis).
are in progress.
Investigation of SLB has to be continued…

B2GM, June 5th 2023, T. Kobayashi

35

Summary• Many upgrade & maintenance works are progressed during LS1.
• LS1 started in July 2022 and will end in November 2023.
• Next beam operation is scheduled to restart in December 2023.

• Progress of “IR works” & “NLC construction” were reported.
• And also, damaged collimator heads were replaced with new ones.
• Most planed works will be completed by October 2023.
• Beam operation will resumed from December 2023.

• Sudden Beam Loss (SBL) is one of the concerned issues to be solved.
• Frequently, the beam suddenly disappears within few turns just before the abort.
• The cause of SBL is still unknown. (Several candidates for the cause are considered.)• Continuation of investigation or study of SBL is needed to avoid it.

B2GM, June 5th 2023, T. Kobayashi

36

Thank you for your attention.

B2GM 2023.6.5

37

Backup Slides

B2GM, June 5th 2023, T. Kobayashi

38

Remaining Works for NLC
Magnet power supply room (ground level)• Required works for NLC construction
Collimator relocation from D03V1
Q magnet relocation (done) and alignment
Skew sextuple magnets installation
Beam pipe installation
Installation of new power supplies
Magnet cabling works

D04
D05

Cable pit 1

Cable pit 2

Positronbeam• Radiation shielding enhancement• Production & installation of new Pb radiation shields• Production & installation of additional concrete shields• Reinstallation of concrete shields

Ohostraight section

•
•
•
•
•
•

Tsukuba (Belle II)

S. Nakamura

Additional concrete shields

collimator

∼5 m
Pb/
SUS
∼50 mmNew Pb radiation shield
Y. Sakaki

concrete shields

B2GM, June 5th 2023, T. Kobayashi

39

RF Cavity Replacement @ D05A

T. AbeBreakdown often occurred at D05A cavity. (down rate was high at D05A)
IP→ Defeat of brazing was found in the coupling cavity. → Replaced

Done Feb. 2023

ARES Cavity (normal conducting)

S-Cav

A-Cav

D04
D11

This part was replaced with a spare

C-Cav

Oho

Nikko

D05A

D10

D05
Replace

Fuji
ARES Cavity

D07
D08

FIG. 1. Illustration of the ARES cavity structure (Ref. [9]). The accelerating (A-)cavity is coupled
to the storage (S-)cavity via a coupling (C-)cavity. The C-cavity has a parasitic-mode (0 and πmode) damper. An illustration of the coupled pendulum model is also shown.

D05 Acc. Section

S-C connection flange→ After the replacement,
RF conditioning was successfully donein April 2023 (No problem was found).
B2GM, June 5th 2023, T. Kobayashi

40l 次ページにあるようなベローズに繋がる変換フランジの新規製作を検討中
VacuumSeal
Replacement@
DRRF
sectionl 現行のダクトを改造品と交換後、オールメタルにする• Vacuum seal replacement at RF section (DR)…..Done!

Done in 2022

• For pressure reduction• Elastomer gaskets were replaced with metal gaskets for dummy pipe connections.

１回目の大電力試験時

T. AbeO-Ring Replacement Work

２回目の大電力試験時
RF Cavities for DR

現在

HOM Damper

メタル化
Metal O-Ring

Cavity Side

Beam Duct Side

B2GM, June 5th 2023, T. Kobayashi

41

Plan – Non-linear collimator at LER OHO section

T. Ishibashi, IAS Program on HEP 2022

• Present collimator setting (2021ab)• D06V1: primary collimator: most tightly closed and suppresses the injection BG.
• D02V1: second collimator: closest vertical collimator to IP and very important to suppress BG• D06V2, D03V1: backup: not so tightly closed. D03V1 can be used for a backup of D02V1.

•If we can replace D06V1 collimator with
non-linear collimator (NLC) for example, theΣ𝛽𝑦 𝑘𝑦 dramatically decreases.
(βy: vertical beta function, ky: vertical kick factor)
NLC

15

B2GM, June 5th 2023, T. Kobayashi

42

Plan – Non-linear collimator at LER OHO section

T. Ishibashi, IAS Program on HEP 2022

• Collimator setting (half-aperture) during physics run in 2021b (βy*=1 mm)• The βy at the D06V1 is large, and the aperture is narrow.
• The βy at the NLC is small, and the aperture is wide.
→ We could dramatically decrease the Σ𝛽𝑦 𝑘𝑦 if we can replace D06V1 with NLC.
16

B2GM, June 5th 2023, T. Kobayashi

43Plan – Non-linear collimator at LER OHO section• Scheme

T. Ishibashi, IAS Program on HEP 2022

[K. Oide]

−𝐼

𝜋
∆𝜇𝑦 =
2

17

B2GM, June 5th 2023, T. Kobayashi

44

Fireball Hypothesis

T. Abe21(T. Abe)
B2GM, June 5th 2023, T. Kobayashi

45