SuperKEKB commissioning

1. LS1 work
2. Commissioning plan
2-1 Vacuum scrubbing
2-2 Tentative weekly schedule
2-3 Current, luminosity

2024/1/29

B2GM SuperKEKB Commissioning, Mika Masuzawa

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1. LS1 work
(1) Reinforcement of radiation shielding around the IP, replacement ofthe cap at the head of the QCS cryostat→ Background reduction(2) Installation of a new type of collimator (Non-Linear Collimator) inthe Oho straight section→ reduction of beam instability caused by the collimator,
collimator protection, and etc.
(3)Chamber modification of the HER injection section→ injection injection efficiency improvement(4) Replacement of collimator head→ installation of more robust collimator, replacement ofdamaged collimators, Cu coating on the collimator head(against SBL from “fireball,” etc.)＃Monitors added, acoustic sensors around the collimators (SBL)

2024/1/29

B2GM SuperKEKB Commissioning, Mika Masuzawa2

2-1 Vacuum scrubbing

Vacuum scrubbing needed for LER (Vacuum work area indicated by•••••••2024/1/29

IR WorkBeam pipe and other installation work for NLC construction
Collimator related• Head replacement: D02V1, D06V1, D06H3 (carbon), D06H4• Collimator relocation: D03V1 to D05V1, D06H1 to D06H4• Chamber with HOM absorber installed near D06V1Replacement of bellows in Nikko-Oho Wiggler section (to preventtemperature rise)
Magnetic field measurement in K1 and K2 ceramics chambers
Vacuum leak due to broken feedthrough for strip-type NEG pump
(D09 arc section)
Beam dose required for vacuum scrubbing (approx.): 100 Ah

B2GM SuperKEKB Commissioning, Mika Masuzawa3

2-1 Vacuum scrubbing~100Ah scrubbing plan (LER)

100Ah4

2-1 Vacuum scrubbing

Vacuum scrubbing needed for HER (Vacuum work area indicated by•••••

IR WorkCollimator related• Head replacement: D01V1, D09V1
Bellows replacement on the gate valve collision point side (D01 arcsection)• During beam operation, pressure jumps were frequently occurring in
CCG D01̲H116 near the gate valve.
• The bellows on the gate valve collision point side was removed forinternal observation, and it was found that the depth of the RFcontact groove upstream of the bellows chamber was 1 mm deeper
than the design value (the design value of 1.95 mm was actually
2.95 mm).
• The bellows was replaced with one of the correct dimensions.
Chamber replacement at injection section
Vacuum leak at ion pump HV feedthrough (D09, D12 arc section)
Vacuum leak at bellows chamber weldment (D04 arc section)•Beam dose required for vacuum scrubbing (approx.): 50 Ah•

2024/1/29

B2GM SuperKEKB Commissioning, Mika Masuzawa

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Y. Ohnishi

2-2 Tentative weekly schedule
2024

January27(Sat)

February
28(Sun)29(Mon)

C: OwlOwl

B: Evening

Evening

31(Wed)1(Thu)

2(Fri)HER vacuum
scrubbing
100 mAHER vacuum
scrubbing
200 mALER vacuum
scrubbing
100 mAHER vacuum
scrubbing
250 mALER vacuum
scrubbing
200 mAHER vacuum
scrubbing
250 mALER vacuum
scrubbing
250 mALER βy* = 48.6 mm(with D05V1)

HER βy* = 81.0 mm

LER βy* = 48.6 mm(without D05V1)

Find COD
HER BCMLER New
Find COD beamline

HER BxB FB tuning

LER BxB FB tuning

HER injection tuning D05V1 study
HER kicker jump
LER impedance
HER septum tuning meas.

DA measurement

HER BxB FB tuning

LER BxB FB tuning

LER injection tuning
LER kicker jump
LER septum tuning

LER/HER QuadBPM

acoustic sensor(SBL)

HER BPM gain
mapping
HER optics
correction
HER injection tuning

LER BPM gain
mapping
LER optics
correction
LER injection tuning

LER/HER QuadBPM LER/HER QuadBPM

acoustic sensor(SBL)

A: DayDay30(Tue)LER/HER TBT BPM
study

HER BCMLER optics
correction
D05V1 study

DA measurement

6Y. Ohnishi

2-2 Tentative weekly schedule2024

C: OwlOwl

A: DayDay

B: Evening

Evening

February3(Sat)

4(Sun)

5(Mon)

6(Tue)

7(Wed)

8(Thu)

9(Fri)HER vacuum
scrubbing
300 mALER vacuum
scrubbing
300 mAHER vacuum
scrubbing
300 mALER vacuum
scrubbing
300 mAHER vacuum
scrubbing
350 mALER vacuum
scrubbing
350 mAHER vacuum
scrubbing
350 mALER vacuum
scrubbing
350 mAHER vacuum
scrubbing
400 mALER vacuum
scrubbing
400 mAHER vacuum
scrubbing400 mA
LER vacuum
scrubbing
400 mAHER vacuum
scrubbing
450 mALER vacuum
scrubbing
450 mAHER βy* = 81 → 8mm
HER βy* = 8 → 3mm
HER βy* = 3 → 2mm
HER βy* = 2 → 1mm

collision tuning
LER D05V1 study
find collision backet

HER optics
correction

collision tuning

Standardize
magnets

LER βy* = 48.6 →8 mm
LER βy* = 8 → 3mm
LER NEG activation
LER βy* = 3 → 2mm
LER βy* = 2 → 1mm

LER NEG activation

LER optics
correction

LER D05V1 study

HER opticscorrection
LER optics
correction

LER BxB FB tuning HER BxB FB tuning

LER TBT BPM
studycollimator tuning

HER injection
LER injection tuning
tuningLER collimator
HER collimatortuningtuning
LER impedance
HER impedance
meas.
meas.

HER TBT BPM
studycollimator tuning7

Y. Ohnishi

2-2 Tentative weekly schedule
2024

Owl

C: OwlFebruary
10(Sat)11(Sun)12(Mon)13(Tue)14(Wed)15(Thu)16(Fri)

HER vacuum
scrubbing
500 mALER vacuum
scrubbing
500 mAHER vacuum
scrubbing
500 mALER vacuum
scrubbing
500 mAHER vacuum
scrubbing
500 mALER vacuum
scrubbing
500 mAHER vacuum
scrubbing
550 mALER vacuum
scrubbing
550 mAHER vacuum
scrubbing
600 mALER vacuum
scrubbing
600 mAHER vacuum
scrubbing
600 mALER vacuum
scrubbing
600 mAHER vacuum
scrubbing
600 mALER vacuum
scrubbing
600 mAHER sextupole
study

LER sextupole
study

LER rotating
sextupole

HER sextupole
study

LER sextupole
study

LER rotating
sextupole

HER TBT BPM
study

LER TBT BPM
study

HER TBT BPM
study

LER TBT BPM
study

21(Wed)

A:Day
Day

B:Evening
Evening
2024

C:Owl
Owl

A:Day
Day

February
17(Sat)18(Sun)19(Mon)20(Tue)HER vacuum
scrubbing
600 mALER vacuum
scrubbing
600 mAHER vacuum
scrubbing
600 mALER vacuum
scrubbing
600 mAHER vacuum
scrubbing
600 mALER vacuum
scrubbing
600 mAHER vacuum
scrubbing
496 mALER vacuum
scrubbing
620 mAtuning for physicsrun

22(Thu)23(Fri)maintenance(regular)tuning for physics
run

B:Evening
Evening82-3 Current, luminosity
Y. Ohnishi

Recover the 2022 peak luminosity with 𝛽!∗ = 1𝑚𝑚↑↓𝛽!∗ = 0.8 𝑚𝑚 study↑↓Aim at Luminosity run with 𝛽!∗ = 0.8 𝑚𝑚
It is not possible to say at this stage when 𝛽!∗ willbe changed.
↑↓

2024/1/29(Needless to say that) luminosity will be lower
while tuning the machine with new parameters,such as 𝛽!∗ .

B2GM SuperKEKB Commissioning, Mika Masuzawa

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2-3 Current, luminosity
Slide presented at thecommissioning meeting on
Jan.12, 2024 by Y. Ohnishi.

Crab waist (CW)• Reduces resonance lines and beam-tail due tobeam-beam interactions.

•Increasing the total beam currents (bunch currents)(obstruction) Sudden Beam Loss•

Squeezing 𝛽!∗
Dynamic aperture, lifetime, background control, injection►sextupole settings, collimator settings•

Optimizing the Crab waist ratio for both LER and HER.

2024/1/29

B2GM SuperKEKB Commissioning, Mika Masuzawa• CW seemed to have improved luminosity.
• We will confirm the luminosity gain.
• The CW ratio (LER 80%, HER 40% in 2022) willbe optimized• lifetime vs luminosity gainMachine study time↑↓Physics run10

2-3 Current, luminosity

Let's continue to work together to achieve our goals.
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B2GM SuperKEKB Commissioning, Mika Masuzawa

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2024/1/29

B2GM SuperKEKB Commissioning, Mika Masuzawa

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2024/1/29

B2GM SuperKEKB Commissioning, Mika Masuzawa

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Luminosity degradation
Possible causes• Machine imperfections: Non-zero linear and chromatic coupling and dispersions at IP, beam-current dependent optics
distortion due to orbit change at QCS* and SLY*, etc.
• Imperfect crab waist scheme; Interplay of beam-beam interaction and beam coupling impedance.
• Beam oscillation excited by injection kickers at LER causes luminosity loss by ~10%.
D. Zhou, et al, doi:10.18429/JACoW-IPAC2022-WEPOPT064

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B2GM SuperKEKB Commissioning, Mika Masuzawa

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