SKB Limitations and upgrade path

Mika Masuzawa
KEK Accelerator Laboratory

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Contents
1. BPAC 2023
2. Progress since
3. Conceptual design of the magnet
4. Luminosity
5. Summary

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1. BPAC 2023

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1. BPAC 2023

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2. Progress since••2024/2/5

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Magnet configuration⇅Optics evaluation using
3D magnetic field
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2. Progress since•

Magnet configuration

Present IR

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

new IR

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2. Progress since•

Optics evaluation using 3D magnetic field profile

1.

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 is reduced to several tens of femtometer.

73. Conceptual design of the magnet
Parameter

Current IRoptics

New IR
opticsL* (mm)935

835

Distance between the coil & HER
helium vessel (mm)

10.8

1.1

Required integrated field GLeff (T)2325.75

Required field gradient G(T/m)

67.88

76.01

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

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We need• Thinner coil
• Superconducting wire that can withstand higher current density(from 1630A/mm2 to >3000A/mm2, beyond NbTi )Nb3Sn magnet
8Current sharing temperature @2.5T

3. Conceptual design of the magnet
2D model calculation(N. Ohuchi)

Leak field
Less than 1 Gauss

Field gradient = 80T/m
Current density in Nb3Sn is 3112 A/mm2
Bmax in the coil ~ 2.5 T
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93. Conceptual design of the magnet

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
accelerator magnets in the world.
Handling of such brittle wire, operating in
the lower magnetic field environment
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

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R&D required10

3. Conceptual design of the magnet

Research collaboration with FNAL and Furukawa Electric Co.,
Ltd. and KEK has started.

Some Furukawa technologies are
subject to Non-Disclosure Agreement(NDA)

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3. Conceptual design of the magnet
Presented by N. Ohuchi@IR upgrade mini workshop Jan.27, 2024••••2024/2/5“mirror” HQM (Nb3 Sn) forLHC upgrade

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

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

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Finalmagnet
design.

4. Luminosity
Path toward 10!"
→Increasing 𝐼# andsqueezing 𝛽$∗ to 0.8 mm
Path toward 2×10!"→ Increasing 𝐼# more andsqueezing 𝛽$∗ to 0.6 mm

Specific luminosity improvement at higher 𝐼(2024/2/5BPAC

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Parameter set examples
by Y.Funakoshi

4. Luminosity

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4. Luminosity

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4. Luminosity
D. Zhou, et al, doi:10.18429/JACoW-IPAC2022-WEPOPT064•

Machine imperfections:• Non-zero linear and chromatic coupling anddispersions at IP.
• Beam-current dependent optics distortion due toorbit change at QCS* and SLY*, etc.

•Imperfect crab waist scheme• The nonlinear optics and optics distortion (machineerrors, current-dependent orbit drift, etc.) aroundthe IR might reduce the effectiveness of CW insuppressing BB resonances.

•Better working point in the tune space?

•Increasing the HER crab waist strength might help.

We will check them during the 2024ab run
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4. Luminosity• Injection is another very important factor for luminosity
performance.
• →LINAC talk by H. Ego.
• New HER BT line (presented at BPAC2023)• Installation of additional high-power klystrons for storinghigher beam current.
• Renewal and maintenance of aging components.
• If new breakthrough found during the 2024 run, then will beconsidered.
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175. Summary
The new IR optics idea was evaluated using the 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•

Nb3Sn magnets are needed.
• We have started collaboration with FNAL and Furukawa Electric Co., Ltd. .

Luminosity strategy• Operate the machine at higher 𝐼# , smaller 𝛽$∗• Improve the specific luminosity at higher 𝐼#• Aim at peak luminosity 1×10!" 𝑐𝑚&' 𝑠 &( and beyond.
• Efforts will be made to establish a reliable model through extensive machine studies during 2024 run
to understand the discrepancies between the simulation and the machine.
• The path to higher luminosity will become clearer.
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