SuperKEKB Status and plan
Contents• MR• Achievements• Challenges• Other issues• LINAC Summary• LS1• Summary
Makoto Tobiyama, Mika Masuzawa
Accelerator Laboratory
BPAC June 27, 2022

1

• MR
• Achievements• Challenges• Other issues• LINAC Summary• LS1• Summary

BPAC June 27, 2022

2

2022ab Run!"∗ = 0.8((

Achievements• 1460mA in LER, 1143mA in HER• # of bunches was increased to 2346 (2 bucket spacing)• Peak luminosity 4.65×1034 cm2s-1 , 4.71×1034 cm2s-1 (Belle HVoﬀ)• Stable operaRon at higher beam currents• 1.3A or more in LER seemed less stable but we managed to
run the machine at 1.4 A at the end.
• Conﬁrmed speciﬁc luminosity increase when !"∗ = 0.8 ((7 day record•

Integrated luminosity ∼160 U-1

BPAC June 27, 2022

3

From 2019 to 2022ab

COVID-19
There were tough times• No face-to-face meetings• Minimum number of people in thecontrol room required• Travel restrictions
Now we are facing new problems• rising electricity• delay/stop in supply-chain
Integrated recorded luminosity ~428 fb-1
Corresponds to ~ 40% of BELLE data

BPAC June 27, 2022

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Specific luminosity“es;mated”
explained later

BPAC June 27, 2022

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Vertical beta function at the IP !"∗Achieved (0.8mm)

BPAC June 27, 2022

6

• MR
• Achievements• Challenges• Other issues• LINAC Summary• LS1• Summary

BPAC June 27, 2022

7

Challenges : Fast and large beam losses• Observations• Fast and large beam losses within 3 turns, particularly in LER are observed.
• These losses cause collimator damage and QCS quench.
• Empirical rule: Bunch current !"± must not exceed 0.7mA “Matsuoka rule”.
• We had to increase beam currents with !"± lower than 0.7mA.

• Mechanism• Not really understood.
• Some hypotheses, simulations → need to be verified.
• A joint Belle2-SuperKEKB team has been organized(https://kds.kek.jp/event/41394/contributions/209334/attachments/154298/195935/16aA5
61-03.pdf)• Within the framework of ITF (H. Ikeda and H. Nakayama) ?

Y. Funakoshi, IPAC’22

BPAC June 27, 2022

8

Matsuoka rule, well categorized by Matsuoka-san

In the case of a small number of bunches (!" = 793, #$% =61mA, #$' = 31mA)
we could exceed this limit.
Large beam loss in LER happened even within the limit ( #"% ~0.62mA) when the total
beam current #$% ~ 1325mA.
BPAC June 27, 2022

9

Challenges : Fast and large beam losses
An example
Bunch Oscillation Recorder (BOR)
Horizontal
BOR
VerFcal

BOR amplitude= oscillation amplitude × bunch current

Bunch Current Monitor (BCM)
1 turn••Beam loss
Beam was aborted here by beamabort system based on informationfrom beam loss monitors.

Very fast beam loss: within 3 turns
No bunch (dipole) oscillations were observed before beam loss.

– In some cases, beam oscillation in the previous turn of beam loss was observed.

•

No beam size blowup is observed before beam loss.
BPAC June 27, 2022

Y. Funakoshi, IPAC’22
10

Challenges with Injec:on (more later)• SuperKEKB injection scheme• Injector Linac provides e+ and e- beams. (e+: thermionic gun, DR, e-: RF gun)• Synchronization between injector and rings allows 1-bunch or 2-bunch injection per pulse.
• Top-up injection is achieved for e+ and e- beams at 50Hz at maximum(sum of e- and e+).

• Beam current limitation• The maximum stored beam currents in the rings are determined by the balance between
the charge sent from Linac and the charge loss due to beam lifetime.
• Increasing linac charge is important.

• The shorter beam lifetime at smaller by* (dynamic aperture) requires a more powerfulinjection. Conversely, injection sets a limit on the achievable by*.
• Machine operation with the optics of by* = 0.8mm is being tried in this run.

• The injection efficiency is also a very important issue.
• Depends on by*, bunch currents, machine tuning, collimator setting…
• Typical values of injection efficiency with by*=1mm: ~50%(LER), ~40%(HER)• Emittance preservation in Linac and Beam Transport line (BT) is important.
BPAC June 27, 2022

K. Furukawa, IPAC’22
11

Challenges , beam-beam• Luminosity is much lower than simulations with BBSS (Beam-Beam Strong-Strong)• Possible Cause

D. Zhou, IPAC’22• Machine imperfections:• Non-zero linear and chromatic coupling and dispersions at IP, can be corrected by skew sextupole field.
Will explain later• Optics degradation at higher beam current due to orbit changes 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% (???)

HER 40%, LER 80% is here

BPAC June 27, 2022

Y. Funakoshi, IPAC’22

12

Challenges , collimator issues
LER TMCI (Transverse Mode Coupling Instability)
The apertures of verGcal collimators ↔TMCITMCI threshold will be lower than the design bunch current of 1.44mA when !"∗ ≤ 0.6mm.
Non-linear collimator may help to increase the limit and to reduce the BELLE II BG.

BPAC June 27, 2022

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Challenges , collimator damages
Collimator damage of D06V1, D02V1, and D09V1: Impedance increases ?

BPAC June 27, 2022

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Challenges , collimator damages

BPAC June 27, 2022

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LER vertical beam size blowup study, the effect of the damaged D06V1 collimator on June 21
When D06V1 collimator bottom was opened, the emittance threshold increased,
Indication that the collimator damage resulted in an impedance increase…
BTM -5.1 mm

393 bunches
V-tune : .5820 -> .5950
D6V1 TOP 4.2 mm

BTM -8 mm!"#~ 0.87mA/bunch!"#~ 0.5mA/bunch
BPAC June 27, 2022

Study by
S. Terui
T. Ishibashi
K. Yoshihara

16

LER vertical beam size blowup study, the effect of the damaged D06V1 collimator on June 21
When D06V1 collimator bottom was opened, tune shift became smaller,
Indication that the collimator damage resulted in a larger tune shift.

2022/6/20

2022/6/21

0.016 /mA

0.019 /mA

BPAC June 27, 2022

S. Terui
T. Ishibashi
172022abQCS Quench Summary

Date

Where

Cause of Abort

2022.3.11
10：08

QC1LP（all coil）
QC2LP

beam loss（CLAWS+Dia.）

2022.3.16
23：35

Not known

Earthquake

2022.4.8
11：55

QC1LP（coil 2）

2022.5.17
14：38
2022.6.1
22：05
2022.6.3
14：48
2022.6.9
00：37
2022.6.9
04：26
2022.6.14
14：34

QC1LP（coil1,2,4）
QC1RP（coil1,2）
QC1LP（coil1,2）
QC1LP（all coil）
QC2LP
QC1RP（coil1,2）
QC1LP（coil1,2）
QC1RP（coil1,2,3）
QC1LP（all coil）
QC1RP
QC1LP（coil1,2,4）

QuenchNot categorized
as Quench
After D06V1, D02V1 were damaged

beam loss（CLAWS+Dia.）beam loss（CLAWS+Dia.）beam loss（CLAWS+Dia.）beam loss（CLAWS+Dia.）beam loss（CLAWS+Dia.）beam loss（CLAWS+Dia.）beam loss（CLAWS+Dia.）
BPAC June 27, 2022

Twice
8 times

4 QmesWang Xudong18

Challenges , Op7cs degrada7on at higher beam currents
Orbit control (to the level of !") at sextupole magnets, especially at Local Chroma7city Correc7on (LCC) sec7on is cri7cal
SLY magnets

An orbital change of 40 !" results in a vertical tune
shift of about 0.025.
Tune Feed back keeps the tune at the target tune
but the orbit at LCC sextupole mangnets is notcontrolled to the level of !".
This results in a beta beat in the entire ring (optics
degradation).

H. Sugimoto#$∗ was estimated to become smaller with theseorbit change than when the optics were corrected
at lower beam current (~50mA).
BPAC June 27, 2022

19

Challenges , Optics degradation at higher beam currents
Orbit control feedback was introduced (Y. Ohnishi).
• But why orbit changes as a function of beam current?
• Duct move due to SR?
• Sextupole magnet moves with respect to the quad (BPM is attached to quad)• What is moving wrt to what?
• Under investigation.

Changing the bump height (blue line) to keep the orbit constant
BPAC June 27, 2022

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Beam oscilla6on excited by injec6on kickers at LER causes
luminosity loss by ~10% (???)

BPAC June 27, 2022

D. Zhou21

Beam oscillation excited by injection kickers at LER causes
luminosity loss by ~10% (???)

Needs more invesHgaHon

BPAC June 27, 2022

22

• MR
• Achievements• Challenges• Other issues• LINAC Summary• LS1• Summary

BPAC June 27, 2022

23

Other issues
Electricity rates

BPAC June 27, 2022

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• MR
• Achievements• Challenges• Other issues• LINAC Summary• LS1• Summary

BPAC June 27, 2022

25

Injector Linac Operation Status
presentation material for BPAC
2022
By courtesy of M. Satoh and N. Iida, 2022.06.21

BPAC June 27, 2022

26

Injector linac opera.on• Simultaneous top-up injec.on to 4 rings w/ two e- sources (thermionic, rf guns) , and 100 pulsed magnets havebeen successfully con.nued.
• Rf gun cavity, laser system, ﬂux concentrator (FC), and other subsystems have been stably operated w/o any
signiﬁcant troubles through run 2022a,b.
e+ target (W), capture section

Mul.-stage laser systemfor e- rf gun• e- bunch charge fromrf gun (blue dot) havebeen kept around 2 nC
w/ bunch charge
feedback system.
BPAC June 27, 2022

• e+ bunch charge at linac end(black dot) can reach around
3.5 nC (final goal is 4 nC).
• Sometimes, bunch charge isintentionally reduced byadjusting FC timing by therequest from SuperKEKB
MR.
27

Injections in 2022ab••

e- beam needs a tuning every few days.
e+ beam is rather stable thanks to the DR.

①④<latexit sha1_base64="vODvUY1+R+fgKV7ByRa18ui3+ig=">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</latexit>

I [mA]HER

1st bunch
2nd bunch

HER LER②

Inj.

1st bunch(BCM)
2nd bunch(BCM)
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Qe [nC]③

QCS BW135<latexit sha1_base64="avEtlbzgDRJ4ib/7xBlCq+43/cQ=">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</latexit>[mRad/s]Inj.
<latexit sha1_base64="KVf0zoPcuXoQZtVcYdlKKnM3jR8=">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</latexit>

1st bunch(BCM)
2nd bunch(BCM)
DCCT
1st bunch
2nd bunche↵L [%]<latexit sha1_base64="bSrtq8zR/RERgfxCG5ccbEE+NTA=">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</latexit>

Qp [nC]QCS FW135<latexit sha1_base64="x5qgGLoF0Saona3botSI6n5LXBo=">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</latexit>[mRad/s]BP<latexit sha1_base64="8zWbvlVPtBy84Ex43bd1PzCa9bM=">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</latexit>

LER

The injection efficiency depends on;• the quality of injection beam
• injection parameters such as septum angle• status of the stored beams and collimatorsin the SuperKEKB ring

diamondby*=1mm (basically)Oﬀ-resonanceby*=0.8mm

BPAC June 27, 2022⑤

Improvements① The injection was improved by the currentdependent correction of the horizontal
orbit at SLYTE * in HER. Now the orbit
feedback systems are working well.
② The septa have been operating at 25Hz.
③ The fast strip line kicker has been used tocorrect the horizontal orbit for the 2ndbunch
To be improved④ Since the injection efficiency of the 2nd ebunch decreased due to the drift of thevertical orbit and the worse emittances ofthe 2nd bunch, the two-bunch injection was
temporarily given up.
⑤ e+ bunch charge has been reduced to avoid
the CLAWS aborts. See the lower rightfigure in the previous page.

28

• MR
• Achievements• Challenges• Other issues• LINAC Summary• LS1• Summary

BPAC June 27, 2022

29

LS1
• IR radia8on shield modiﬁca8on• For BG reduc8on• New heavy metal shields around IP bellows• Addi8onal concrete & polyethylene shields around Belle II• Material change from W to SUS of QCS cryostat front plate• Non-linear collimator (LER)• For impedance and BG reduc8on• New collima8on scheme less likely to cause TMCI at smaller !"∗• Removal of 50 wiggler magnets,
emiWance, circumference• Installa8on of 2 skew sextupole and 5 quadrupole magnets• Installa8on of new ver8cal collimator with wider aperture• Robust collimator head (LER)• As countermeasure against kicker-pulser misﬁring and resul8ng destruc8on ofcollimator• Replacement with carbon head of horizontal collimator D06H3• New beam pipes with wider aperture at HER injec8on point• For improvement of injec8on eﬃciency• New beam pipes with wider aperture• New BPM for precise measurement of injected beam
• QCS leak test
• Others
BPAC June 27, 2022

Y. Funakoshi, IPAC’2230

LS1 schedule (~March, 2023)

BPAC June 27, 2022

31

International Task Force (ITF)
Examples of activities• Lattice translation and repository for SuperKEKB; Optics optimization and simulations
with independent codes.
• Dynamic aperture optimization, new optics design.
• Beam-beam simulation, impedance calculation, instability theories.
• Deep discussions on the simulation results and new ideas.
• Proposed many machine study items and discussion on the results.

BPAC June 27, 2022

4 working groups
Optics, Beam-beam, TMCI, LINAC+New group “beam loss”
The next one will be held in mid/late July
Hybrid (zoom + face-to-face)

32

• MR
• Achievements• Challenges• Other issues• LINAC Summary• LS1• Summary

BPAC June 27, 2022

33

Summary
We achieved• LER beam current: 1460 mA• HER beam current: 1143 mA• Number of bunches: 2346 bunches (2-bucket spacing, design) with a stable operaPon over 1 A in LER• Peak luminosity: 4.65 x 1034 cm-2s-1 / 4.707 x 1034 cm-2s-1 with Belle II HV OFF
Challenges• Understanding various beam loss mechanism• Collimator damages• OpPcs degradaPon due to orbit change at higher beam current• InjecPon: stability of e- beams, 2-bunch injecPon
LS1 started• Beam circulaPon in 2023 a[er various upgrade/modiﬁcaPon work.

BPAC June 27, 2022

34