Present Commissioning Issues&Tentative Next Run Plan
Akio Morita
2019-06-17

Luminosity Performance●

5.495 x 1033 cm-2s-1 is achieved during Belle2 data taking with continuous injection.

●

Actual daily production rate is reached to 297.85 pb-1 @ 2019-06-02 00:00 ~ 24:00.

●

Expected maximum daily production rate is 334.20 pb-1.
– 111.40 pb-1 per shift is achieved @ 2019-06-05 00:00 ~ 8:00.

nb=789Nb=1576 trial w/o DAQ

nb=1576

Cooling time
due to QCS Quench

Specific Luminosity(β*y = 3mm)●Phase-3 Lsp is almost same as best Lsp on Phase-2 nb=789 operation.
– Beam-beam parameter is not improved from Phase-2.

●

Phase-3 Lsp on nb=1576 WOULD be scaled until 6 x 1034 cm-2s-1.
– Phase-3 nb=1576 operation(red) is different with Phase-2(gray).
350 x 340mA
nb = 789

700 x 680mA
nb = 1576(scaled)QCS Quenches●

2019/05/27 15:08 QC2LE Quench/No beam
– QC2LE PS slow down due to IPM IL●

2019/05/28 01:32 QC1LE/QC2LE Quench/LER Inj.(499/494mA)– QC2LE PS slow down due to IPM IL●

2019/05/31 19:49 QC1RP Quench/LER Inj.(596/600mA)– D06V1 loss monitor trip at first●

2019/06/06 14:53 QC1LE/QC2LE Quench/LER Inj.(650/618mA)– QC2LE PS IPM IL●

2019/06/06 16:41 QC2LE Quench/No beam
– QC2LE PS IPM IL●

2019/06/09 22:11 QC*R & ESR/QC1LP Quench/LER Inj.(654/616mA)– Long down time to recover cooling system(~ 2days) due to outflow of large amount of He gas.
– LER D02V1 bottom collimator head is damaged.
– Big beam loss(~100mA during 3~4turns) is observed before beam abort.

QCS Quench Issues●Unstable QC2LE PS IPM(4 events)– Repair works is ongoing by NICHICON. (2019/05/28, 2019/06/13)●QCS quench due to beam loss(2 events)– Possibility that QCS quench is caused by dust event is pointed out.
– Current beam abort system is too slow to protect beam collimator & Belle2 VXD for 2019-06-09

event.
– Discussion to speed-up beam abort has been started.
– Lower limit of abort latency of current fill pattern is 10μsec(1-turn) for synchronizing next abort gap.
●In order to break this limit with current abort kicker system...
– Introduce fill pattern with multi abort gap (Reduce total number of bunches)– Accept extra beam loss caused by raising edge of abort kicker (A part of aborted beam bunches hits accelerator components &Belle2 detector)

Luminosity Performance Issues●

Specific luminosity & beam-beam parameter are lower than designed/planedvalue.
– Achieved beam-beam parameter is only 0.02.
●

Extrapolated luminosity is 2 x 1035 at design current & design β*y if beam-beam is not improved.

– Big beam-beam blowup is observed.
●●A possibility of big IP chromatic aberration is pointed out from beam-beam simulation, however,off-momentum optical function measurement result is not consistent with such big aberration.

Operation beam current limit due to Belle2 detector background– Storage beam background due to LER beam-gas Coulomb scattering– CDC HV trip due to injection beam backgroundMachine Study at This June●

●High current operation test & machine studies arescheduled during 2019/06/24 ~ 31.
Extra 1 shift for RF μ=-1 mode damper tuning toprepare high current operation is proposed during
2019/06/19 ~ 21 (day or swing shift).

Squeezing β* Trial?

Tentative Run Plan until 2020-07-01●

2019/10/15 ~ 2019/12/12 (~8weeks)– Vacuum scrubbing & restore β*y=3mm - 3weeks (Assuming D02V1 head replacement)– Prepare β*y=2mm collision - 1week– Physics run - 4weeks●

2020/01/15 ~ 2010/07/01 (~24weeks)– Vacuum scrubbing - 1week– TEPCO power line work - 1week– Vacuum scrubbing & restore β*y=2mm - 1week– Squeezing β* study - 1week– Prepare β*y=1.5mm collision – 1week– Physics run – 18weeks (except 03/20 for TEPCO power line work)– High current study - 1week

Machine study time for future beam development is NOT included.

Luminosity Projection
ASSUMPTIONS(risky●Integral Luminosity
13.9 fb-1 (2019-10 ~ 2019-12)
112.8 fb-1 (2020-01 ~ 2020-07)

realistic)

Integral Efficiency (~65%)– Integration Time Efficiency ~90%●●

8H maintenance & 4H startup / 2weeks
12H linac study / week

– SuperKEKB Availability 85%– Belle2 Availability 85%●●Availability @ 2019-06-02 is 89.6%.

Luminosity Performance

1200/1100mA– Baseline: 0.5 x 1034 @ 600/550mA(nb=1576, β*y=3mm)– No beam-beam parameter improvement

600/550mA– β*y staging: 2mm @ 2019-11 → 1.5mm @ 2020-02– Improvement by squeezing β*y: 1/√β*y →1/β*y during operation period●

Assuming detector background independence with β*y.

840/770mA– Beam current limit improvement: x√2 @ 2019-12-12 → x2 @ 2020-06-24

Assuming factor 2 improvement of CDC current limit until next summer.
●
Assuming no current limit for protecting detector.
●●Machine Study– No future beam development time is counted.

Scrub/Prepare 2mm

β*y3mmScrub/Prepare 1.5mm

2mm

High Current Study

1.5mm