SuperKEKB MR Status

Akio Morita
2021/06/21

New Achievements●Peak Luminosity– 2.95668 x 1034 cm-2s-1 @ 2021/05/17 21:26

β*y=1mm I = 837.4 / 676.5 mA (LER/HER) nb = 1174●

Integrated Luminosity– 1964.22 pb-1/day @ 2021/05/18– 747.19 pb-1/shift @ 2021/05/19 swing shiftβ*y=1mm Imax = 840 / 680 mA(LER/HER) nb = 1174

2021a/b Operation
Baking Run @ 2021/04/21
Imax=1000/920mA(LER/HER) nb=1370

Stable collision on Imax=840/680mA(LER/HER) nb=1174
QCS Quench●
QCSL/ESL●QC1LE●QC1*P

β*y=1mm

Ecm = -60MeV

β*y=2mmHigh current
collision trial

Enable LER Sextupole Rotator
Deploy Chromatic IPTilt Knob

CLAWS abort

x1x3x6

Maximum Current @ PhysicsRun
Imax=840/820mA(LER/HER) nb=1272
2021/04/14~19

Lpeak ~ 2.95668x1034 cm-2s-1~25% Lsp gain by reducing
HER Vert. BxB FB gain(-6dB)
LER FB gain is not affected.
D02V1 collimator works

Specific Luminosity
Almost same Lsp with 2020b β* y=0.8mm collision

2020c current is limitedby TMCI of carbon collimator.

Vacuum Scrubbing

Vacuum pressures are gradually improved by integral beam dose.
from vacuum_scrubbing.pptx @ KCG 2021/06/15

QCS Quenchs●

03/20 – QCSL/ESL Quench (Lv.4 Earthquake)●

03/28 – QC1LE Quench due to QC1LE PS trouble●

03/39 – QC1LE Quench due to QC1LE PS trouble●

04/19 – QC1LE Quench (20msec after VxD abort)●

05/10 – QC1[LR]P Quench with D2V1 CCG raise●

05/14 – QC1RP Quench with D06H3 CCG raise●

05/23 – QC1[LR]P Quench with D06V1 CCG raise●

05/28 – QC1RP Quench with D06V1 GGC raise●

06/02 – QC1[LR]P Quench with D02V1 CCG raise●

06/06 – QC1[LR]P Quench

QC1P quench frequency is big issue for stable collision operation.

Damaged D02V1 Collimator Head
D02V1 BOTTOM

D02V1 TOPe+e+

After 05/10 QC1P Quench with D02V1 CCG raisefrom 20210510.pptx @ KCG 2021/05/11

After 06/02 QC1P Quench with D02V1 CCG raisefrom 20210603D2V1.pptx @ KCG 2021/06/03●●

D02V1 serious damage is suggested by bad detector background after QC1P quench @ 06/02.
D02V1 surface damage is confirmed by Horizontal Bump Study @ 2021/06/03 11:30~12:00.

D02V1 collimator head was replaced during 2021/06/07~09.

Operating Software Improvements●BT end orbit feedback– Feedback stability & reliability are improved by using single waveform

EPICS PV containing synchronized BPM data set instead of individual
EPICS PVs (x, y position and charge PVs per BPM).
●●

Fix data propagation race among individual PVs.

CCC(slow global orbit feedback)– Ring energy analyzer drift is improved by fixing calculation algorithm.
– Interference with collision feedback (iBump V-OFFSET drift) is improvedby reducing degree of corrector freedom.

Ring Energy Analyzer Drift2020a/b2020c

2021a/bEnergy analyzer drift is reduced by improving conservation of total horizontal steering kick angle.
(Fix kick angle sum drift due to truncating small component in correction vector.)Collision Feedback V-OFFSET Drift
Excluding ZVQC1[LR]E correctors●●

iBump damper keeps V-OFFSET
within hardware limit.

ZVQC1RE●●ZVQC1LELarge V-OFFSET drift is observed during 2021/04.
To keep iBump V-OFFSET within hardware limit,
iBump damper is required.
Overall V-OFFSET drift absorbed by damper is 80μm.
In order to reduce V-OFFSET drift rate, ZVQC1LE &ZVQC1RE sterrings are excluded from CCC orbit
corrector set.

Reduce iBump damper height step-by-step by hand.

iBump V-OFFSET Drift Mechanism
1. CCC’s global orbit correction makes common mode kick between ZVQC1LE and ZVQC1RE.
●Its mode is hard to observe by BPM system.
2. It makes vertical displacement at the IP and iBump FB is responding to such displacement.
3. iBump V-OFFSET drift is damped via iBump damper by using ZVQC1LE/ZVQC1RE.

IP Chromatic Coupling Issue●●●

LER sextupole rotator default angle parameter set is changed from “zero”
to the angles minimizing model IP chromatic coupling since 2021/03/11.
Chromatic IPTilt knob tool is deployed to control IP chromatic coupling for both
LER and HER since 2021/03.
Now IPTilt(coupling/v-dispersion) and chromatic IPTilt COULD be controled
independently in linear perturbation region.
Typical IPTilt knob strength exceeds linear perturbation region.
●
Typical strength of skew quadrupole correctors are increased due to additional constraint.
●– The orbit displacement side effect at changing IPTlit knob becomes more serious.
– The orbit on some strong skew quadrupole corrector (ex. QKARP) SHOULE be off-centered.
●●

Chromatic IPTilt knob scan ranges are limited by corrector strength & detector BG.
The work point reducing beam-beam blow up, which is predicted from beam-beamsimulation, is not found at this moment.

Summary●Achives better specific luminosity compared with β*y=1mm collision in2020.
– Achives almost same I+I- - Lsp curve with β*y=0.8mm collision in 2020b.

●HER BxB FB side effect to HER beam size & luminosity is found.
– LER BxB FB looks like OK.

●●

Adiabatic chromatic IPTilt tuning during PhysicsRun is tried, however,significant luminosity improvement is not found at this moments.
Collision operation stability is improved by both hardware and operationsoftware improvements.