LS2: Next Long shutdown

Mika Masuzawa
KEK Accelerator Laboratory

2024/3/26

ARC1

Contents
1. BPAC 2023
• Strategy• Progress since 2022
2. Other possible upgrade ideas
3. Summary

2024/3/26

ARC

2

SuperKEKB can provide
higher luminosity with lower beam current than KEKB→ “nano-beam” SuperKEKB is a “eco” “sustainable” machine

But we are a luminosity frontier machine
Luminosity increase is our 1st mission

2024/3/26

ARC

Y. Suetsugu

31.BPAC 2023
•Strategy•Progress since 2022

If to go for LS2 or not depends on• how SuperKEKB performs• MEXT evaluation sometime ~ 2026.

And more

2024/3/26

ARC4

1.BPAC 2023
•Strategy•Progress since 2022

1. Improvement inTouschek lifetimeexpected.

2. Improvement inTouschek lifetime andchromatic x-y
coupling reductionand emittance growth
suppression areexpected.

3. No constraint,
can include
redesign of thecrossing angle,extensive
beamlinemodifications andso on.
This will take a
lot longer timeand need a lot
more manpower
to evaluate.
2024/3/26

ARC5

1.BPAC 2023
•Strategy•Progress since 2022•••

2024/3/26

ARC

Magnet configuration
Current distribution⇅Optics evaluation using
3D magnetic fieldprofile

6

1.BPAC 2023
•Strategy•Progress since 2022

Present IR

QC1Ps from L*=935mm to 835mm
Cover QC1Ps with the magnetic yoke
Install new solenoid coils between IP and QC1Ps

new IR

2024/3/26

ARC

7

1.BPAC 2023
•Strategy•Progress since 2022

3D field calculation carried out by Y. Arimoto& the data were given to the optics G.
2024/3/26

ARC8

1.BPAC 2023
•Strategy•Progress since 2022

By A. Morita

IR orbit, straighter with New IRPresent IR

2024/3/26

New IR

ARC

91.BPAC 2023
•Strategy•Progress since 2022

IR dispersion

Present IR

2024/3/26

By A. Morita

New IRARC10

1.BPAC 2023
•Strategy•Progress since 2022

1.

By A. Morita

LER DA
Present IR lattice
by*=0.27mm

New IR lattice
by*=0.27mm

Touschek lifetime from~260 s to ~420 s.

2.

3.

Chromatic coupling improves significantly,
L*(mm)

𝜕𝑅1⁄𝜕𝛿

𝜕𝑅2⁄𝜕𝛿

𝜕𝑅3⁄𝜕𝛿

𝜕𝑅4⁄𝜕𝛿

935−8.9×10!"+4.0×10!"−5.0×10#$+2.9×10#$835+2.3×10!%−6.0×10!&−4.4×10!'+5.5×10!"

Emittance growth arises from IR is reduced to several tens of femtometer.

11

1.BPAC 2023
•Strategy•Progress since 2022

By N. Ohuchi
Parameter

Current IRoptics

New IRoptics

L* (mm)935

835

Distance between the coil & HER
helium vessel (mm)

10.8

1.1

Required integrated field GLeff (T)

23

25.75

Required field gradient G(T/m)

67.88

76.01

Cross sectional view along the LER beam line, if we scale the current NbTi QC1P

We need• Thinner coil• Superconducting wire that can withstand higher current density(from 1630A/mm2 to >3000A/mm2, beyond NbTi )Nb3Sn magnet
12

1.BPAC 2023
•Strategy•Progress since 2022

Current sharing temperature @2.5T

By N. Ohuchi

2D model calculation(N. Ohuchi)

Leak field
Less than 1 Gauss

More temperature margin

Field gradient = 80T/m
Current density in Nb3Sn is 3112 A/mm2
Bmax in the coil ~ 2.5 T2024/3/26

ARC

13

1.BPAC 2023
•Strategy•Progress since 2022

Nb3Sn accelerator magnets at CERN
Another success for the HL-LHC magnet programme: after the successful endurance testof a 4.2-metre-long niobium–tin quadrupole magnet in the United States in spring 2022,
the HL-LHC quadrupole’s longer version proved its worth later in the year. “MQXFBP3”, thethird full-length quadrupole prototype to be tested at SM18, reached nominal current plus
an operational margin in September–October 2022, confirming the success of theniobium–tin technology for superconducting magnets.
Our QC1P face similar challenges and, on
the other hand, quite different challenges.
• Much smaller any other Nb3Sn acceleratormagnets in the world.
• Making a small magnet with such brittlewire.
• Operating in the lower magnetic fieldenvironment than LHC.
• QC1P filament size < 5 𝜇𝑚 , much smaller
than LHC filament (~50 𝜇𝑚).
→ →To prevent quenches from flux jump
and to reduce long-term drift.

https://home.cern/news/news/accelerators/hilumi-news-72-m-long-niobium-tin-quadrupolemagnet-manufactured-cern

2024/3/26

ARCR&D required14

1.BPAC 2023
•Strategy•Progress since 2022

We have started a study group on hardware assembly and installation for IR modifications.
•••••

Magnet group
Monitor group
Vacuum group
Belle II groupotherAn example of topics being discussed
2024/3/26

ARC15

1.BPAC 2023
•Strategy•Progress since 2022
CopperalloyNb3Sn• Research collaboration with FNAL and Furukawa Electric Co., Ltd. andKEK has started.
Some Furukawa technologies aresubject to Non-Disclosure Agreement (NDA)• Coils were test wound with the sample wire we sent @ FNAL.
• We made an application for U.S.-Japan Science and Technology
Cooperation Program in High Energy Physics.
• We are planning to train students under International Leading Research（科研費：国際先導研究).

2024/3/26

ARC

Before heat treatment

16

1.BPAC 2023
•Strategy•Progress since 2022
Presented by N. Ohuchi@IR upgrade mini workshop Jan.27, 2024

Perform a step-bystep, careful evaluation.

••“mirror” HQM (Nb3 Sn) forLHC upgrade2024/3/26••

Mirror and prototype magnet design.
Making the Nb3Sn cable specification andproduction.
Construction of the mirror magnet.
Excitation test of the magnet.

•••

Construction of the prototype magnet.
•Excitation test of the magnet.
Magnetic field measurements of the magnet.

Depends largely on budget and manpower

17Finalmagnetdesign.

2. Other possible upgrade ideas•Injection is another very important factor for luminosity performance.
From M. Satoh for BPAC Feb,2023•

Installation of additional high-power klystrons for storing higher beam current.

•Renewal and maintenance of aging components.

•If new breakthrough found during the 2024 run, then they will be considered.
•Some can be done before the next long shutdown, during the summer/winter18
shutdown.

2. Other possible upgrade ideas

19Chiral Belle

Slide from Z. Zhanguo
U.S.-Japan Science and Technology Cooperation Program in High Energy Physics.

Status• Simulation work are being carried out by people outside of SuperKEKB.
• Our priority is improving luminosity performance.
• No budget has been allocated from the SuperKEKB LINAC side.
• The first meeting between Chiral Belle and the SuperKEKB LINAC team (Ego-san) was held last December.
20

3. Summary

The new IR optics idea was evaluated using a 3D magnetic field profile.
• Longer lifetime is expected.
• Beams go straight through the IP, through the center of the quads.
• Chromatic x-y coupling becomes a lot smaller.
• Luminosity degradation, which arises from IR nonlinearity and beam-beam effects, may berecovered. Further simulation work is necessary.
• Emittance growth from the new IR is expected to become much smaller.
→ Very simple IR→ To realize this, Nb3Sn magnets are needed.

• Regular meetings started, to discuss IR hardware assembly and installation issues.
• We believe that establishing the technology to make compact magnets using the Nb3Sn
superconducting wire will be useful not only for SuperKEKB IR upgrade but also for futureaccelerators and accelerator application.
We ask for your support• R&D with KEK Cryogenics Science Center, FNAL and Furukawa Electric Co., Ltd. has begun.
Luminosity strategy•

Efforts will be made to establish a reliable model through extensive machine studies during 2024 run tounderstand the discrepancies between the simulation and the machine.

• The path to higher luminosity will become clearer.

21

2024/3/26

ARC22