SuperKEKB MR status and upgrade during LS1
Y. Arimoto for SuperKEKB
Oct/10th/2022 B2GM

Contents•

SuperKEKB status•••

Achievements and issues

LS1 activity•

Non-Linear Collimator•

The other activities

SummaryAchievement on 2022ab•

Peak luminosity : 4.65 x 1034 cm-2s-1 (4.71 x 1034 cm-2s-1 w/o Belle II data taking)•Integrated luminosity : 424 fb-1 (491 fb-1)•Peak currents : 1.46 A (LER) / 1.14 A (HER), 2346 bunches (2-bucket spacing) withstable operation over 1 A in LER•

Chromatic X-Y coupling correction with the rotatable sextupoles in the LER:
luminosity improvements•A long-term drift of QCS magnetic eld (beta-beat): reduced by the new QCS
initialization procedure

Ref.: https://agenda.infn.it/event/21199/contributions/168882/fi3

Y. Onishi

2022ab Runβ*
y = 0.8 mm

184 fb-1
160 fb-1

Accidental fire of LER injection kicker on March 18
The reserver voltage of thyratron was adjusted.

Ref. https://kds.kek.jp/event/42954/

Y. Onishi

5

Stable operationin 8 hours
Int. LRecorded = 958 fb-1
Apr/24/2022SuperKEKB Phase 3β*y squeezing

down to 1 mm

β*
y = 3mmβ*y = 1mm
Crab Waistβ*y = 2mm2022abβ*y = 0.8mm

β*
y = 0.8mm

1145 mA

1460 mA

Nextef(Linac)
fire

D06V1
carboncollimator

HER
BxB FBnoise

4.65 x 1034 cm-2s-1(4.71 x 1034 cm-2s-1)

424 fb-1 / 491 fb-1

2019 ab2019 c2020 ab2020 c2021 ab2021 c2022 abhttps://kds.kek.jp/event/42954/

Y. Onishi

6

Vacuum scrubbing since Phase1
It takes ∼ 2.3 months to get 1×103 Ah. (LER)
wholeLERArc2022ab

HERwhole2022ab

ArcK. Shibata
2022/7/13

Phase3 2022ab KCG Summary Meeting

7Issues•Fast Beam Loss abort is a serious problem. It causes QCS quench andcollimator damages if there is a large beam loss.

•Collimator damage of D06V1, D02V1, and D09V1; Impedance increases?
Single beam blowup ( Ib+ > 0.6 mA ) in LER•Beam-line deformation due to "SR heating" or "HOM heating" (Beam position
monitor depends on beam currents.)•Optics degradation after one week of optics corrections; Earthquake alsoaffects optics signi cantly in the HER.

•Injection: stability of e- beams, 2-bunch injection (ef ciency and stability)

fifi

Ref. https://kds.kek.jp/event/42954/

Y. Onishi

Machine Parameters
SuperKEKB : June 8, 2022

Y. Onishi

Ref. https://kds.kek.jp/event/42954/

SuperKEKB : May 22, 2022

Unit

RingLER

HER

LER

HER

Emittance

4.0

4.6

4.0

4.6

nm

Beam Current

1321

1099

744

600

mA

2249

Number of bunches

1565

Bunch current

0.587

0.489

0.475

0.383

mA

Horizontal size σx*

17.9

16.6

17.916.6μm

Vertical cap sigma Σy*

0.303

0.250

μm*1

Vertical size σy*

0.215

0.177

μm*2

Betatron tunes νx / νy44.525 / 46.589 45.532 / 43.573 44.525 / 46.589 45.532 / 43.574

βx* / βy*80 / 1.0

60 / 1.0

80 / 0.8

60 / 0.8

Piwinski angle

10.7

12.7

10.7

12.7

Crab waist ratio

80

4080

40

Beam-Beam parameter ξy0.04070.02790.03090.0219mm%

Specific luminosity

7.21 x 1031

8.74 x 1031

cm-2s-1/mA2Luminosity

4.65 x 1034

2.49 x 1034

cm-2s-19*1) estimated by luminosity with assuming design bunch length*2) divide *1 by √2

Non-linear collimatorNon-linear collimator•

We will install the non-linear collimator (NLC) during LS1.

•The NLC scrapes unwanted-beam particles even in a large aperture.
•

Reducing wake- eld kick at the collimator•

Relaxing Transverse Mode Coupling Instability•

The NLC consists of a pair of sextupole magnets and a collimator.

•

A new sextupole magnet is designed and under construction.
Non-Linear CollimatorCollimator

Sextupole: IQuadrupolefiSextupole magnet kickunwanted-beam particles

Sextupole : -I

Collimator scrapes unwanted-beamparticles with large aperture

Quadrupole

Second sextupole magnet brings good beamback to its original angle.

Illustration byK. Shibata

Non-linear collimator: Location•NLC will be constructed at OHO straight section.
IPTSUKUBA
Construction site of
non-linear collimator

NIKKO

OHO

FUJI
T. Ishibashi

Non-linear collimator: Construction

S. Nakamura← IP (Tsukuba)
HER(e-) →LER(e+) ←Skew sextupole magnet

New collimator (D05V1)• Take away these wiggler magnets.
Twenty double pole magnets, ten single pole magnets, ten
half pole magnets.
The weight of the power cable, which is removed together
with magnets, is about 3000 kg.
• Relocation quadrupole magnets.
• Install a pair of new skew sextupole magnet.
• Install new vertical collimator (D05V1).
Now we start to remove the wiggler magnets.

Skew sextupole magnet

Wiggler magnets~40 mSextupole magnet for Non-linear colliemator
Parameters of sextupole magnet for NCL
56.0
300
600
21400-500
33.4
11.8
2012.016.510.415105

3D Model of sextupole magnet

I = 600 A

By

Mechanical parameters
Bore radius [mm]Lamination length [mm]Electromagnetic parameters
Maximum current [A]Number of turns in a coil [Turns/pole]B”[T/m2]
Resistance at 30+ΔT℃ [mΩ]Inductance [mH]
Voltage [V]Power consumption [kW]Thermal parameters
Flow rate of cooling water [L/min/mag]
Temperature rise [℃]Maximum pressure[kg/cm2]
Working pressure [kg/cm2]
Pressure drop [kg/cm2]x

B vs x (Simulated by OPERA)

R. Ueki

The other activity during LS1

QCS-R Vacuum-Leak Check•

QCS-R vacuum-leak incident:•••

We found a large leak in the vacuum chamber( Reported by Ohuchi-san at MDI meeting onSep. 2021 )Helium leak check on Sep/2022:•by Vacuum group and QCS group•

We found a vacuum leak at the service vessel,
not the cryostat.

Repairing the vacuum leak•

We will repair at IR during LS1.

Photos by Z. Zong

Leak area of QCS-R
Service cryostat

3

Leak rate (Pa*m /s)

Magnet cryostat: no Leak !

Leak !

Trend of He leak rate

5E-05

by Z. Zong

1E-05 16:02~ GHe to
1E-06

Service cryostat
O-ring at the middle

1E-07
1E-08
1E-09

16:00

2 min

2x10-5 Pa m3/s
Vacuum level:
1.9E-3 Pa Pump guage
4.1E-3 Pa cryos. guage

16:10

16:20

Modi cation of QCS front cap

QCS-L front
plateMotivation••

Making space for cables of Belle II•

Reducing background produced at QCS
front surface.

QCS-L

•

•

Changing front plate material from tungsten
to stainless steel

Tungsten →Stainless steel

QCS-R front cap

QCS-R

••

Making the front cap smaller•

Changing material to all stainless steel

Current designfi

Next design

Major issues 6• HER collimator D09V1 damageCollimators• 6/11 22:09 Belle2 CLAWS+Belle2 VXD diamond Abort (Both rings)• Large beam loss, Large pressure burst at D09V1 collimator• It was very likely that D09V1 head was damaged.

D09V1thatcollimator
damage• It wasHER:
visually confirmed
jaw was damaged.
(6/15)•Replacement of damaged collimator•LER: D02V1, D06V1•

HER: D09V1•

Damaged by sudden beam loss•

•June 2nd (No damage)June 15th (new damage)

Replacement to Low-Z (Carbon) collimator
D06H3

T. Ishibashi•

Damaged by the accidental re of the kicker magnet•

Expected to be robust against beam loss

2022/7/13

Phase3 2022ab KCG Summary Meeting

Carbon collimator headRelocation for NLC•

D03V1 → D05V1•

Set at the NLC section

T. Ishibashifi•Aperture enlargement of HER injection channel• Problem of HER injection

No enough roomwall• Wall can be an obstacle to injection.
• A wall should be placed between beam channels for stored
beam and injected beam.
• Injected beam orbit is too close to the wall.
• High levels of radiation detected at the injection BPM
chamber indicates that the injected beam hits the wall.
• It is hard to modify the injection beam orbit.
it is necessary to enlarge the horizontal apertureof the injection channel.
N. Iida (2022.1.21) BITF meeting•

What is planned during LS1••

Replacement of three beam chambers with new ones.
Update of injection BPM
More precise injection tuning

M. Kikuchi (2021.12.03)
BITF meeting

K. Shibata

Vacuum work locations during LS1
Collimator head replacement(D02V1)LERHER

Collimator relocation(D03V1 -> D05V1)

Installation of new bellows
to suppress temperature rise
Collimator head replacement(D09V1)

NLC (D05V1)

Magnetic field measurement inK1 and K2 ceramic chambers

2022/7/13

Collimator head replacement(D06V1, D06H3)
Collimator relocation(D06H1 -> D06H4)

Injection chamber replacement

Phase3 2022ab KCG Summary Meeting

K. Shibata21••MR•

Replacement of HER injection chamber.

•Replacement of HER septum magnet (SE1) and modi cation of the power supply to improve
eld quality•

Re-alignment of HER 4th arc quadrupole magnets•

Install OTR screen monitors as many as possible•

Modi cation of voltage divider circuits of LER kickers to increase reliability•

Replacement of ceramic chambers for LER kicker K1 to make the same pulse shape between
K1 and K2 kickers•

Modi cation of thyratron’s trigger circuit of HER/LER abort kickers for faster triggeringDR•

Replacement of main capacitors of DR ext. kickers to improve stability

fifiM. Tawada
fifi

Upgrade items during LS1 (BT)

Update items during LS1 (Control group)•

Apply “Bunch Current Equalizing” system for two-bunches injection•Revise the algorithm of the injection ef ciency determination- Bunch current after injection is monitored one pulse later.

•Improve the timestamp synchronization for Abort Trigger modules- utilize White Rabbit module- need discussion of the software development for the abort analysis.

•

Upgrade the Beam Gate system for HER- delayed control signal based on White Rabbit to synchronize the control of
the gun and septum/kicker magnet triggers.
- that for LER is followed in 2024.

fiH. KajiBeam dynamics issues

Ref. D. Zhou, eeFACT2022 workshop,Frascati, Rome, Italy, and references therein• Many sources of luminosity degradation were better understood during 2022b run, leading tobetter agreements in simulated and measured luminosity• Known sources of luminosity degradation- Bunch lengthening; Chromatic couplings; Single-beam blowup in LER caused by an interplay of impedance andfeedback system; Optics distortion due to synchrotron radiation heating; Luminosity loss correlated with injection; …

• Sources of luminosity degradation to be investigated via simulations and experiments- Imperfect crab waist; Beam-beam driven synchro-betatron resonances; Interplay of beam-beam, longitudinal andtransverse impedances, and feedback system; Global couplings; Interplay of beam-beam and nonlinear lattices;
Coupled bunch instabilities; …
2022b run: Luminosity degradation corresponds to an extra blowup of vertical beam sizes
Speci c luminosity

Electron σ*
yPositron σ*yfi

D. Zhou24

Beam dynamics issues (cont’d)• TO-DO list of investigations during LS1- Impedance budgeting (T. Ishibashi): Impedance models are ready for both LER and HER. Benchmarks and further-re nements are ongoing.
Strong-strong beam-beam simulations with impedances: Use the latest impedance models as input.
Strong-strong beam-beam simulations with impedances and complete lattices: Codes are under development
considering GPU-boosting (K. Ohmi, Joint SuperKEKB-CEPC team)Strong-strong beam-beam simulations with impedances and other factors (such as space charge, realistic feedback,etc.): Code development, benchmark, and investigations
Impact of the nonlinear collimator (NLC) on machine performance• International collaboration on accelerator physics challenges at SuperKEKB- Joint e orts on simulation codes for reliable predictions of luminosity: Teams of SuperKEKB, CEPC, and FCC-ee- An international workshop on “Luminosity of colliders: Predictions, experiments, and machine tunings” (Tentative-title) is under preparation
Joint e orts on theories/simulations of impedance modeling and impedance e ects in colliders- The rst international workshop on “Impedance modeling and impedance e ects at SuperKEKB and futurecolliders” (Tentative title) is under the organization• From the viewpoint of beam dynamics, during LS1, we must develop an executable strategy/plan of luminosity tuning/optimization, and machine studies, together with the Belle II team

ffff

ff

ff

fifiD. Zhou

25

Toward LS2•

We are revisiting the investigation of IR section to achieve integrated
luminosity of 50 ab-1 around 2030.

•Beam optics investigate IR optics•QCS group considers magnet design.

•Vacuum group and QCS group investigate the mechanical design.
QC1Pとビームパイプ

Option-3

コイル内半径R24.925
R24.725
R23.225

Main quad.

R20.725 (vertical)Correctors

t=1.5mm

QC1P cross section
Correctors
Main quad.

ビームパイプ材質
QC1Pの部分だけでも重金属を使えないか？
2022/9/16

Gap=1.5mm

t=1.0mmSuperKEKB QCS Upgrade打合せ

6Summary•Main ring status•

Achievement: peak luminosity: 4.65 x 1034 cm-2s-1, integrated luminosity : 424 fb-1 (491 fb-1)•

Issues: Fast beam loss, Injection ef ciency, current dependence of beam position.

NLC•

•

•

We decided to install NLC during LS1, now in construction.

Works during LS1•

We found a vacuum leak at QCS-R•

Installation the low-z collimator at D06H3•

Replacement of HER injection chamber.

•The control system will be updated•

The optics group investigate beam-beam simulation

Toward LS2•

We are revisiting the investigation of IR section.

fi•Backup

QI4E用ビームパイプ:隔壁の変更
現状縦方向に50倍しています。

QI4E centere- Beam

縦方向に50倍しています。

変更案

データを元に作図
QI4E centere- Beam
⻩⾊が隔壁
Kicker Orbit
4σx

オレンジ⾊が隔壁
3σxInjection Orbit

Ring
BPM

Inj.
BPM

By菊池さん

Kicker Orbit
4σx

3σx
Injection Orbit
4σx

3σx

Ring
BPM

Inj.
BPM

• 方針：蓄積ビーム側と入射ビーム側を隔てている壁(隔壁)を薄くしたり、オフセットしたりして、クリアランスをできるだけ確保する。
• 壁を曲げたりはしない。製作が難しい(精度がでない)。
Phase3 2022ab KCG Summary Meeting

Y. Suetsugu

5

K. Shibata