Belle II status
Kodai Matsuoka (KEK, Nagoya)Dec. 13, 2022

Basic strategy of Belle II operation• Safe operation not to damage Belle II detector or machinecomponents• First priority on the peak luminosity (machine tuning and study)– Except for safety issues• Physics data taking with a high efficiency➢ Mission of luminosity frontier experiments– Our first target: 90% of data taking efficiency• Beam background control to suppress– Detector deterioration by integrated radiation dose
– Detector performance degradation by high rate beam background➢ Required for precision experiments2Discussion about the abort threshold3(See more detail in the backup slides)• As the beam current and injection charge increased, beam aborts at injections
without apparent trouble/failure happened more frequently.
– e.g. 77 unnecessary beam aborts issued only by the diamond at LER injection• ~30 min to restore the beam current after each abort• A relaxed diamond abort threshold might allow for smooth efficient machine
operation, but it delays the abort trigger and increases the risk of damaging
the detector/machine in case of huge beam loss, which is not assessable.
– [Risk of relaxed threshold] = [frequency (reducible)] × [severity (unknown)]• We had discussion about how to balance the machine operation and risk.
– Decision is particularly delicate due to many huge beam losses, QCS quenches, collimator damages.

– 4 → 6 mrad threshold for one diamond with Belle II off is prepared as a final resort.

• We continue our efforts to compensate the risk of the relaxed threshold.
– e.g. 6 mrad threshold only during injections (which take place 1.5% of time at most)and additional faster abort systems are under consideration.
Risk of damage

Effort to reduce the risk

Smooth efficientmachine operation

4

Integrated luminosity
2021c

2022ab“Target” plan
620 /fb

Delivered308/fb491/fb“Base” plan
Recorded
268/fbRecorded
2.2/fb/day

424/fb“Base” plan

2.5/fb/day

520Plan
18
Result16
1412
10810.706 GeV
64
10.657 GeV
2011/10 11/13 11/16
09:00 09:00 09:00

Online measurement ofthe relative center-of-mass energy

10.810 GeV
10.751 GeV

Maintenance

Maintenance

Recorded luminosity (fb–1)

Higher energy collisions above Y(4S)

Contingency
11/19
09:00

11/22
09:00

11/25
09:00

11/28
09:00
10.810 GeV

𝑁𝜇𝜇 /run > 5E4

10.706 GeV
10.657 GeV
Y(4S)

10.751 GeV
Old B-field map
just for a testOld

New B-field map

Y(4S)exp.run

We appreciate great efforts by the accelerator team.

Collision energy

B counting

6
https://indico.belle2.org/event/8281/contributions/50205/attachments/
19946/29553/Bcounting_phys_12Dec2022.pdf

10%

Momentum analyzer(The absolute scale is unknown.)
Energyscan202010.580 GeV

10.574 GeV

2021

The collision energy had beenshifted by ~4 MeV (5-7% lossof 𝐵𝐵ത ) for 1.5 years

https://indico.belle2.org/event/3644/contributions/18630/attachments/9460/14519/BsBvEcms.pdf
https://indico.belle2.org/event/5396/contributions/27373/attachments/13406/20296/beamPars_tracking_2021_10_15.pdf

7Momentum analyzer
Dec 2021–1.5 MeV
Off-resonance runs

Nmm > 1E5

Off-resonance runs

–3 MeVBelle II operation• There are 3 options of where to take the BCG shift:– Room 225 in 3-go-kan (from the beginning)– His/her own office in 3-go-kan as additional infection prevention (since Apr 25)• Prepared web tools so that anyone can easily see all the BCG monitors.
https://skbsrv.kek.jp/bcg.html (KEK intranet)– Accelerator control room for better communication with KCG (since May 25)

8Feb 21 - Jun 22, 2022

Data taking efficiency in 2022ab

9

Accelerator tuning, Belle II Belle II
Physics run
trouble, etc.
trouble study Baking run
66.1%
29.3%
0.1% 0.7%
1.9%
Whole run time
Scheduledmaintenancefraction
1.9%Stop-Abort-Load-Start
Running
3.0% HV trip
92.6%
Physics run timeor error
fraction
0.2%
Belle II trouble HV rampInjection veto3.4%
5.2%up/down
DAQ dead time
0.8%
5.9% in total
fraction

Fraction (%)

0%

10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

10090807060
50403020100Overall data taking
efficiency = 87.1%(Target 90%)

Physics run / whole run time
Getting worse withDAQ running / physics run(DAQ running - dead time) / physics run the beam background.

2019c

2020ab2020c

2021ab2021c2022ab

10Run stop reasons202022ab
TRG

15
10TOP (4.1)

5TOP

CDC (5.4)02020ab
2020c
PXD SVD CDC

2021abTOP ARICH

2021c
2022abECL KLM TRG

CDCPXDFeb 21 – Jun 22, 2022

FPGA Single Event Upsets on CDC and TOP front-end electronics is the major concern.
• Reduce recovery time
– Reduction of time for HLT LOAD (~70 sec), which dominates time for Stop-Abort-Load-Start (~2 min)•Reduce run-stopping errors
Processing System– TOP firmware update to retire PS → It will eliminate almost all TOP-related run stops.
– CDC software (and firmware) update to withstand corrupted data
→ Run stops will be reduced by ~30% (and more). Need more human resource to work on them.

•Reduce beam background– Additional neutron shield and shield at the QCS bellows– Non-linear collimator

Work in LS1

num of run stops / day

Daily-averaged run stops during physics run timeClosed D02V1

Reset D06V1
x-orbit bump

Off-resonance

Limit

D09V1 damage

by = 0.8 mm

D02/06V1damage

D06V1 damage

Limit

D06V1 damage

D02V1 damage

Maintenance day

Increase of storage beam background

9:00

Damage of D06V1 collimator increased the storage background twice or more.

1112Performance degradation by injection background
12.3% last week
Dead time fraction for physics runs
∝ Veto time×injection repetition rate
D06V1
damaged10%Injection vetodead time
3/1

4/1
CDC dE/dx mean04

8 12 16 20 40 60 80 200 12000

time since LER injection (ms)

5/1

6/1

TOP busy

13

Performance degradation by injection background
ECL waveform data

reduced# CDC hits

→ Pedestal calculation will be improved.

ECL online delivered luminosity dropped
by a few % during LER injection (due toan event selection for background eventrejection)→ Considering injection veto

14Major upgrades in LS1
Belle II detector upgrade• Exchange of PXD (pixel detector) for the full 2nd layer• TOP conventional MCP-PMT replacement• Migration to new back-end readout (COPPER → PCIe40)• Buildup of HLT units (L1 limit: ~15 → ~20 kHz)
Beam background mitigation• IP beam pipe of new design to mitigate SR• Additional shield on the QCS bellows• Additional shield for neutron background• Installation of a non-linear collimatorProtection of machine and Belle II• Collimator heads of more robust material• Faster beam abort system

All acceptance criteria were passed.

Gold film delamination

PXD2 gliding mechanism issue

It was found gliding mechanism
did not work.
The countermeasure is underinvestigation.
We will set time limit in Feb. todecide which scenario to take.

15

Summary• We have improved our system for stable operation, but all ourefforts were compensated by the increase of the beam
background. 90% data taking efficiency is challenging.
• Impact of the beam background became notable in 2022.
– Significant increase of the beam background not only by the increaseof the beam current but also by collimator damage– Frequent stop of DAQ due to SEU of FPGAs by neutrons– Dead time (>10%) due to injection background veto
– Performance degradation for CDC and ECL due to injection background• Several upgrades are planned during LS1 to cope with thehigh beam background.

16

17Summary• We are on track to the base luminosity profile.
• The target profile is necessary for success ofBelle II physics program.
(fb–1)
Shown by Suetsugu-san on Jan. 27, 2022

Target profile

LS1
Base profile

19Baking run• We set a protocol and plan for increasing the beam current:– Take a baking run (with collisions and Belle II HV standby) to increase thecurrent step-by-step above the max achieved one in 2021c.
• 10 mA step for 20 min.
𝐼target• [collimator alert], [3 beam aborts per ring], [time limit = 10 mA × 40 min]are the stopper of the baking run.
– Increase by 10 mA from 840 mA every weekday.
– Keep the same total current during the day when Nbunch is increased.

6/27

6/20

6/13

6/6

5/30

5/23

5/16

5/9

5/2

4/25

4/18

4/11

4/4

3/28

3/21

3/14

3/7

2/28

2/218060
40200Step size (mA)LER current (mA)∗𝛽𝑦 = 0.8 mm
1800
Step size in baking run
Plan (Feb 16)
QCS quench
1600
Plan (Mar 25)
Plan (Apr 22)
QCS quench
QCS quench
QCS quench
Plan (May 10)
Achievement
1400
D06V1 damaged
D06V1
1200
Recovery from damaged
QCS quench
big earthquake
1000
D02V1, D06V1damaged
QCS quench
800
Golden Week
QCS quench
D02V1 damaged
600
400 Accidentalof LER
200 firing
injection kicker
0 x2

20

Diamond beam aborts at LER injection (only when I > 60 mA)
1412
104-5 mrad

6-9 mrad≥ 10 mrad

Only BP_BW_35 exceeded the thresholdfor all the aborts < 10 mrad.

82

D02V1 D06V1
damage damage

HER IP knob scan

4

D02V1,D06V1
damageFC gainFC gain
70%
65%
Known Linac
troubles6

D06V1
damage03/1 3/8 3/15 3/22 3/29 4/5 4/12 4/19 4/26 5/3 5/10 5/17 5/24 5/31 6/7 6/14 6/21 6/28

BTp energy scan

Orbit correction D06V1BTM wasopened by 500 um.
at D06V1
Closed D06V1BTM
BTp energy tuning

Only that particular diamond sensor (and CLAWS if not vetoed) issued “unnecessary” aborts
very frequently. There must be some minor issue on the machine, but the beam loss at thoseaborts is not a problem. The frequent abort reduced the flexibility of the tuning and madethe diagnosis of the cause very difficult. It was also a show-stopper for the machine progress(as we spent ~3 weeks to cope with these frequent aborts). Recently until Jun 7, it prevented
us from increasing the LER beam current above 1.25 A and the injection charge to LER.

21
G. Rizzo

Aborts with >100 mrad from 7 Jun 2021 to 5 Jun 2022 analyzed by G. Rizzo and L. Vitale

22

Delay in the case of 6 mrad threshold only for BW_35
Statistics is small (33 abort events in total)• Diamond abort was faster than CLAWS
for 2 out of 33 abort events.
• CLAWS is inactive for 1.5% of time atmost due to the injection veto.
2.5-5 us delay
no delay (2.5-5 us delay without CLAWS)no delay (BW_35 at 6 mrad could trigger without delay)
no delay (the other 3 triggered behind a little)

BW_35 triggered first

no delay (the other 3 triggered first)• Higher dose by unknown amount for ~1/33 aborts is the risk we have to take by increasing
the threshold from 4 to 6 mrad for BW_35 only in return for efficient machine operation.
• The balance of risk against benefit is not technical in this case and the decision rests with
the Belle II management.
• We should consider how to reduce the risk. (e.g. divide BW_35 signal and apply 4 mrad(equiv.) for one with injection veto and 6 mrad (equiv.) for the other without veto.)