MR 2022 operationOutline✓ 2022ab operation status
Improved stability
Challenges✓ Remaining program for June
✓ Accelerator side works during LS1
Xudong Wang
B2GM@KEK, 6 June 2022
B2GM

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2022ab operation status
Βy*:0.8mm
Off momentum run since Apr. 27 to May 112

Latest operation status
4.224×1034 cm-2s-1 Twice of the KEKB record!!!

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Beam currents and number of bunches

16627834

Specific Luminosity vs bunch currents product

0.8 mm 2022ab

Estimated

1 mm
2021c1 mm
2022ab5

Improved stability◼ Continuous excitation of HER injection septum• Continuously excite with 25Hz rep.

◼ Injection synchronized beam abort• Irregular beam injection after closing beam gate without kicker excitation.
• Introducing additional kicker excitation after closing the beam gate.

◼ Correction of horizontal beam orbit around local chromaticity
correction(LCC) section.
• Horizontal orbit changes at sextupole magnets of LCC could introduce additional
focusing (defocusing) at IP, which usually cause additional beta-beating and resulting
reduction of injection efficiency (and reduction of beam lifetime).

Y.Ohnishi Commisioning meeting on June 36Challenges◼ Injector• Stability (orbit, energy, beam size, energy spread, etc.)• Frequent re-tuning is needed up to now.
• Seems to be affected by the outside temperature.
• Photo RF gun (Laser, intensity, repetition)◼ Ring• Very rapid beam loss of LER had damaged the D6V1 collimator.
• Increases beam background.
• Higher environmental temperature (around end of May) caused
many failures on the power supplies due to extremely high room
temperature of the power supply buildings (>40 degC).

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D6V1 collimator
D6V1 collimator was damaged in a major beam loss event on May 17th.
D6V1 collimator upper jaw

D6V1 collimator lower jaw

8Remaining program for June
◼ We will try to increase peak luminosity until the end of this run.
◼ Also need to make many machine studies before LS1.
・ Investigating the damaged collimators
Impedance measurement, etc.
・ Horizontal beam orbit shift around LCC section needs further
investigation
What is the source? Effect to the optics. How to correction.
・ Optimization of the vertical orbit in QCS of LER for the BG
reduction and related correction of HER
・ Collimator studyetc.

9Accelerator side works during LS1◼ Non-linear collimator at OHO straight section.
• Remove ~1/3 damping wigglers and install a pair of skew sextupoles, quadrupole
magnet(s) and a vertical collimator.
We will remove 50 wigglers, (quads and correctors, too) in the fall10

Accelerator side works during LS1◼ Non-linear collimator at OHO straight section.
• Remove ~1/3 damping wigglers and install a pair of skew sextupoles, quadrupole
magnet(s) and a vertical collimator.
We will chop up the power cables and remove them this summer/fall✂️
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Accelerator side works during LS1◼ Non-linear collimator at OHO straight section.
• Remove ~1/3 damping wigglers and install a pair of skew sextupoles, quadrupole
magnet(s) and a vertical collimator.

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Accelerator side works during LS1◼ Exchange of QCS front cap and plate• Exchange a smaller QCS-R front cap to widen the gap between the front cap andCDC.
The gap is expected to increase up to 8 mm at the cap tip.
• Exchange the material of QCS-R front cap and QCS-L front plate from W to SUS.

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Accelerator side works during LS1◼ Exchange of HER vacuum chamber around injection point,including injection BPM for much wider horizonal aperture.
◼ Repair of the damaged collimator heads (D6V1, D2V1, etc)
◼ Install a carbon-head collimator at D6H2 for robust beam stopper.
◼ QCS-R cryostat vacuum leak searching and repairing◼ Add a radiational shield around QC1 bellows on Belle II sideThank you for your attention！
The slides are based on Tobiyama-san’s talk at Belle II EB for 1st June.

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