SuperKEKB LS2 Upgrade plans

Mika Masuzawa, Accelerator laboratory

BPAC Feb.19, 2023

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Contents
1. Introduction
2. Main Ring (IR)
3. Injector complex
4. Summary

BPAC Feb.19, 2023

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1. Introduction• We need another long shutdown (LS2) to improve the machine performance beyond~2×10!" cm#$ s #% and toward the target peak luminosity of 6×10!" cm#$ s #% .
• It probably requires
a. modifications of the IRb. an upgrade of the injection complex.

• The modifications must be effective enough that the integrated luminosity lost during
LS2 is recovered quickly afterwards, aiming for the target.
BPAC Feb.19, 2023

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2. Main Ring (IR)Three scenarios are under consideration.
1. Moderate scale modification around 2027 (more than 1 year shutdown):• New QC1 with larger physical aperture, installed closer to the IP for larger dynamic
aperture, keeping the boundary as is.
• R&D work on Nb3Sn quadrupole magnet is necessary.
• Evaluate the impact of modifications on machine performance by 2025 at the latest.

2. Larger scale modification, in addition to 1:• New anti-solenoid configuration, which probably requires detector modifications.
• Optical evaluation of the anti-solenoid field profile and coil design needed.
• R&D work on Nb3Sn thin solenoid is necessary.
• New cryostats and a cryogenic system for anti-solenoid coils need to be designed and fabricated.

3. Much Larger scale modification sometime later (~203x)• New ideas to be sought for, by the ITF, for example.
Ø SuperKEKB-wide effort needs to be made to establish a reliable model through extensive
machine studies after LS1.
BPAC Feb.19, 2023

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StatusThree scenarios are under consideration
1. Moderate scale modification around 2027 (more than 1 year shutdown):• New QC1 with larger physical aperture, installed closer to the IP for larger dynamic
aperture, keeping the boundary as is.
• R&D work on Nb3Sn quadrupole magnet is necessary.
• Evaluate the impact of modifications on machine performance by 2025 at the latest.

2. Larger scale modification, in addition to 1:• New anti-solenoid configuration, which probably requires detector modifications.
• Optical evaluation of the anti-solenoid field profile and coil design needed.
• R&D work on Nb3Sn thin solenoid is necessary.
• New cryostats and a cryogenic system for anti-solenoid coils need to be designed and fabricated.

3. Much Larger scale modification sometime later (~203x)• New ideas to be sought for, by the ITF, for example.
Ø SuperKEKB-wide effort needs to be made to establish a reliable model through extensive machinestudies after LS1.
BPAC Feb.19, 2023

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1. Moderate scale modification around 2027 (more than 1 year shutdown):
New QC1(Nb3Sn)• winding correction coils (NbTi) outside of quadrupole
coils for larger physical aperture• moving closer to the IP for larger dynamic aperture• keeping the detector boundary as is.

RVC modification probably needed
BPAC Feb.19, 2023

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StatusThree scenarios are under consideration
1. Moderate scale modification around 2027 (more than 1 year shutdown):• New QC1 with larger physical aperture, installed closer to the IP for larger dynamicaperture, keeping the boundary as is.
• R&D work on Nb3Sn quadrupole magnet is necessary.
• Evaluate the impact of modifications on machine performance by 2025 at the latest.

2. Larger scale modification, in addition to 1:• New anti-solenoid configuration, which probably requires detector modifications.
• Optical evaluation of the anti-solenoid field profile and coil design needed.
• R&D work on Nb3Sn thin solenoid is necessary.
• New cryostats and a cryogenic system for anti-solenoid coils need to be designed and fabricated.

3. Much Larger scale modification sometime later (~203x)• New ideas to be sought for, by the ITF, for example.
Ø SuperKEKB-wide effort needs to be made to establish a reliable model through extensive machinestudies after LS1.
BPAC Feb.19, 2023

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Detector solenoid cancellation between IP and QC1

In addition to 1. (previous page)• New anti-solenoid configuration, which probably requires detector modifications.
• Optical evaluation of the anti-solenoid field profile and coil design needed.
• R&D work on Nb3Sn thin solenoid is necessary.
• New cryostats and a cryogenic system for anti-solenoid coils need to be designed andfabricated.
Concept• make the beam trajectory parallel to the QC1 magnet axis.
• Zero coupling/zero chromaticity between the IP and QC1.
• minimize 𝜀! by redesigning the solenoid field profile 𝐵" 𝑆 . 𝜀! ∝ ∫ 𝐵#$

Solenoid field profile must satisfy

Expected• The offsets of QC1P and QC2P and the rotation of QC1E/QC2E
are expected to be considerably smaller than the present values
with the new design.
• Wider working area in tune space (next page)• IR nonlinearity reduction (next page)
BPAC Feb.19, 2023

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2. Larger scale modification

Detector solenoid cancellation between IP and QC1Wider working area in tune space

IR nonlinearity reduction

K. Ohmi, D. Zhou,MAC2014 𝛽!∗ = 0.3 𝑚𝑚

Luminosity degradation, which arises fromIR nonlinearity and beam-beam effects may
be recovered.
→further simulation work is necessary.
K. Oide Mar, 2020𝛽!∗ = 1 𝑚𝑚

BPAC Feb.19, 2023

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2. Larger scale modification

Detector solenoid cancellation between IP and QC1

Detector modification is needed.
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3. Much Larger scale modification
New ideas to be sought for, by the ITF (Chair, Y. Ohnishi) working groups, for example.

BPAC Feb.19, 2023

Y. Ohnishi

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3. Injector complex

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3. Injector complex• Injector upgrade work during LS1• Pulsed Quads (x8) at J-ARC for the simultaneous dedicated matching of HER/LERinjection beam
• Pulsed Quads (x4) at Sector1, 2 for low beta optics of HER injection beam
• New accelerating structure• Replacement of air conditioners at SectorA, B (in the accelerator tunnel)• Fast kicker for 2nd bunch orbit correction• Injector upgrade plan/ideas after LS1• e- ECS installation in the current e- BT line
• New e- BT line construction in PF-AR BT tunnel• To mitigate emittance growth due to ISR and CSR effect• Replacement of vacuum duct with the narrower one to mitigate CSR effect• Modification of SY3 dump line for the pulse-by-pulse beam diagnostics (2024)
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BT e- ECS

In line with the budget rules, components of a
new ECS and fabrication of components for acooling water system were approved andfabricated in 3 years.

BPAC Feb.19, 2023

•Linac group has just started the study ofthe effectiveness and feasibility of e- ECS,
including beam loss rates.

•Additional radiation shields might be needed
to incorporate e- ECS.

•Comprehensive study is ongoing.

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New BT line for HER
New BT line for the HER has been proposed, aiming at keeping the CSR/ISRemittance growth under control.

①→ISR induced emittance growth of the new BT line decreased to 1/3 of that in
the current BT line (simulation).
From ARC: Qualify the reduction in terms of CSR emittance growth as well.
Current HER transport line

②Linac②①③
Picture by: SSSEPB 2015 linac and bunch
compressor lecture #2, Tor Raubenheimer

Coherent/Incoherent
Synchrotron Radiation④④
New HER transport lineShares the tunnel in part with
PF-AR transport line

③15

Narrower beam duct for CSR shielding
Horizontal emittance growth
CSR is one of the causes.
CSR shielding by• operating with a vertical bump• reducing the beam-pipe aperture←

T. AgohKasokuki Vol.3, No.1, 2006(24-30)

or• Changing the BT layout to a new (more)straight line (previous page)

ARC:
Detailed optics investigation, 3D
model for the CSR and so on
should be done.
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Dump line modification for pulse-by-pulse beam diagnostics during injection

Current layout of SY3

ECS detailed configurationis omitted here

SY3:3rd beam Switch Yard

Future layout planof SY3
New pulsed bend
will be installedaround hear

ECS detailed configurationis omitted heree+beamebeam
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4. Summary (MR & Injector complex)• The MR/Injector complex modification ideas/plans are being consideredfor LS2• SuperKEKB-wide effort needs to be made to establish a reliable model throughextensive machine studies after LS1.
• R&D work also needed.

• We continue our efforts to improve the machine performance after LS1and to develop a strategy for LS2.

BPAC Feb.19, 2023

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BPAC Feb.19, 2023

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1. Moderate scale modification around 2027
preparation 3.5 years, shutdown 1.5 years
Items#QC12(L/R)

2022

2023

R&D

2024

2025

PrototypeFabrication

2026

2027

Assembly
Installation
tests, fieldmeasurements(Nb3Sn)Cancel coil
Leak field
to HER(b3,b4)x2(L/R)

Corrector
coil

a1,b1,a2,b4(L) +?
a1,b1,a2,a3(R)+?

Cryostatfront part2(L/R)

Fabrication(NbTi)BNL* 1.5 months/coil

Fabrication

2. Larger scale modificationpreparation > 5 years, shutdown > 2 years
Items#Solenoid
coils?

QC12(L/R)

2022(NbTi)

2023

2024

2025

Optical evaluation of ﬁeld proﬁleConceptual Design
R&D

2026

2027

Detail design

Prototype(Nb3Sn)
Corrector
coil

a1,b1,a2,b4(L) +?
a1,b1,a2,a3(R)+?

DesignFabrication

Iron shield
for leak field
to HER

2(L/R)

DesignCryostats
for solenoid
coils

New 2(L/R)
Modified2(L/R)

Design(Nb3Sn)

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