November 13, 2023

Commissioning Plan in Run 2
Y. Ohnishi

BPAC Focused Review

Luminosity History

b
o

n

u
w
lo

r
o
pf

=
*
βy

N + N  nb f0
L=
RL
⇤
⇤
4⇡x ynb Ib+ Ib
=2⇡(e2 f0 )x ⌃z ⌃⇤ymm
1

half crossing-angle: ϕx = 41.5 mrad
β*y = 1 mmexpected:

εy+ = 35 pm

Σz = 7.8 mmbunch length: Σz =2(σz+) + (σz−)

2εy− = 25 pmΣ*y =(εy+ + εy−)β*yThe luminosity improves with each passing year: 2020, 2021, and2022. Especially, it is significant for higher nbIb+Ib−.
Improvements:from 2020 to 2021: manage of HER BxB FB gain, impedance (collimator)
from 2021 to 2022: chromatic X-Y coupling correction, unexpected β*y squeezing ?
In order to achieve 1035 cm-2s-1, blowup should be considered. nbIb+Ib− = 1295 mA2 is necessary with β*y = 0.8 mm.
Ib+ / Ib- / nb = 0.89 mA / 0.62 mA /2346
2

Machine Parameters
June 8, 2022

Target at post-LS1 (1)Target at post-LS1 (2)

Unit

Ring

LER

HER

LER

HER

LER

HER

Emittance

4.0

4.6

4.0

4.6

4.0

4.6

nm

Beam Current

1321

1099

2080

1480

2750

2200

mA

2249

Number of bunches

2346

2346

Bunch current

0.587

0.489

0.89

0.63

1.17

0.94

mA

Horizontal size σx*

17.9

16.6

17.9

16.6

17.9

16.6

μm

Vertical cap sigma Σy*

0.303

0.217

0.178

μm

Vertical size σy*

0.215

0.154

0.126

μm

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

β x* / β y*

80 / 1.0

60 / 1.0

80 / 0.8

60 / 0.880 / 0.6

60 / 0.6

mm

σz

4.6

5.1

6.5

6.4

6.5

6.4

mm

Piwinski angle

10.7

12.7

10.7

12.7

10.7

12.7

Crab waist ratio

80

40

80

80

80

80

Beam-Beam ξy

0.04070.02790.04440.03560.06040.0431%

Speciﬁc luminosity

7.21 x 1031

7.62 x 1031

9.31 x 1031

cm-2s-1/mA2

Luminosity

4.65 x 1034

1 x 1035

2.4x 1035

cm-2s-11035 and 2.4 x 1035 are tentative and considered by Y. Funakoshi.

3Strategy toward 2.4 x 1035 cm-2s-1
L
Lsp =Ib+ Ib nb
2.75 A / 2.2 A

2.08 A / 1.48 A
increasing bunch
currents

Target Luminosity in 2024ab
Preliminary

8x1034 - 1035 cm-2s-1+10 mA/day

Total bunch number is assumed to be 2346.
Increase total currents with bunch currents.
max LER
in 2022

Sudden beam loss has to be suppressed.

+20 mA/day

Injection efficiency has to be kept at high currents(Beam lifetime should be improved.)max HER
in 2022β*y = 0.8 mm
β*
y = 1 mm5

Beam background has to be manageable level.
Number of beam aborts/day should be reasonable.
Single beam size blowup should be suppressed by
reduction of the impedance andBxB FB optimization (noise reduction)
Beam optics should be stable at high currents
by reducing beam orbit deviation between low and highcurrents.
Dynamic aperture for β*y = 0.8 mm might be problem
when we try to achieve 1035 cm-2s-1.

Seven Major Issues

1. Sudden beam loss
2. Beam-size blowup due to Beam-Beam interactions
3. Beam-related background
4. Injection efficiency and emittance blowup in the beam transport line
5. Difficulties to keep beam orbit stable and large vertical emittance for single beam
6. Short lifetime and narrow dynamic aperture
7. Beam-size blowup due to -1 mode instability in the LER (almost fixed the problem)

6

Schedule after LS1 at SuperKEKB
Beam tuning and machine study at Linac/e+DR/BT will be 6 weeks before MR start.
Vacuum scrubbing and machine study will be 3 weeks for the MR.
Machine study will be a higher priority even though during physics run.

2023c

2024a

DecemberJanuary2
Linac Oct.
start

Dec. 28
end

Jan. 15
start

27
e+DR Nov.
start

Dec. 28
end

Jan. 15
start

Dec. 28
end

Jan. 15
start

BT

Nov. 30
start

February

2024b
March

April

May

June

LER

Jan. 29
startJun. 30
end

HER

Jan. 29
startJun. 30
end
Jun. 30
end

Physics

Vacuum scrubbing and Machine study

Physics run will be available from end of February.

Shopping List for 2024a
Vacuum scrubbing
80 - 100 Ah (owl shift on weekday, 3 shifts for holiday)

Adjustment and check of hardware devices (need time because it is after 1 year and half shutdown)
beam monitors, magnet polarity, magnet power supplies, timing system, injection system, cooling system, etc.
Mis-wiring of magnet cable and BPM cable should be considered.

Commissioning of nonlinear collimator (including OHO wiggler optics tuning) in LER
Correction of beam obit and optics (including BPM gain mapping, beam based alignment)
Measurements of optics parameters, orbit fluctuations, tune scan, tune shift, TBT BPM analysis, etc.
*′*′
chromatic X-Y coupling(r1 and r2 ) adjustment by using rotatable sextupoles in LER

Measurement and optimization of dynamic aperture (beam lifetime)change sextupole setting, change crab-waist ratio, use QCS octupoles, etc.

Study for single beam blowup and optimization of BxB feedback system
Study of beam background with movable collimators
8Measures Against
Sudden Beam Loss
We replaced the damaged collimator heads during LS1.
Copper coating of collimator heads (D06H3, D06V1, D05V1, D02V1); It is effective if SBL is fire-ball event.
Install more loss monitors to find timing and acoustic sensors to detect sounds of fire-ball events.
Add another BOR to observe beam orbit changes at SBL source; Two BORs will be available to detect.
Impedance
Nonlinear collimator in LER leads wider physical aperture in vertical. It helps to reduce impedance.
Beam Orbit and Optics Changes between Low and High Currents
Beam pipe deformation caused by SR heating (magnets move as the result, orbit offset at sextupoles might
induce beta-beat and X-Y couplings, etc.). → isolation of BPM from quadrupole magnet and install gap sensor
between the BPM and quadrupole magnet.
Cooling water temperature effects → improve control system
9Measures Against (cont'd)

Beam Injection and Emittance Blowup in the Beam Transport Line (BT)Modification of injection point in HER; enlargement of horizontal aperture of beam pipe to reduce coherent
orbit oscillation, then injection efficiency is expected to be improved.
Additional pulse dipole/quadrupole magnets in linac can control beam optics well and contribute better
injection efficiency. (commissioning before MR)
Since the influence of CSR is suspected, we will test shielding effects to suppress CSR in the positron BT.
Machine Error
Vertical angle at IP in HER is optimized by using temperature balance between upper and lower side of beam
pipe due to SR heating at downstream of IP. Then, the vertical angle at IP in LER is optimized by luminosity
scan.
Horizontal angle at IP in HER is optimized by minimizing error of horizontal dispersions. We expect SR on PXD
will decrease at the new IP chamber.

10Summary
Strategy for 1035 cm-2s-1 luminosity
We will increase bunch currents. Max. number of bunches is 2346 (design value).
SBL problem has to be fixed.
Larger dynamic aperture and physical aperture (collimators) should be realized by sextupole setting and better
detector background controls.
Beam injection
Emittance blowup in the beam transport line (BT) has to be fixed.
Luminosity performance at high beam currents
Single beam blowup has to be suppressed enough.
Beam-beam blowup should be suppressed as much as possible by reducing machine error.
How to squeeze beta function at IP ? (still under discussion)
Tentative target is 0.8 mm. We have to decide at some point. We 'd like to check SBL occurs or not first.
Machine study is needed to make larger dynamic aperture (longer lifetime). It takes a lot of time.

11

Appendix

12Max. beam current/day

Plan of Vacuum Scrubbing for LER in 2024a
Y. Ohnishi, Nov. 2 ver.

detunedoptics (Jan. 30 - Feb. 5)

Imax = 600 mA for the first 2 weeks
Bunch number depends on situations.

squeezing βy* down to 1 mm
Feb. 6 (Tu)NEG activation
Feb. 5 (Mo)vacuum scrubbing(holidays)
vacuum scrubbing(holidays)

Day and evening shift (weekday) : machine study
Owl shift (1 am - 9 am) and holiday: vacuum scrubbing

Target integrated dose is 100 Ah until Feb. 17.

2024
13

Sudden Beam Loss (SBL)
Beam becomes unstable suddenly at high beam current.
Beam loss can lead to severe damage on collimators or final focus magnet (QCS) quench.
LER beam current : 1.4 A
number of bunches : 2249
luminosity : 4.58 x 1034 cm-2s-1

Damage of collimator head

Beam loss within a few turns
without large oscillation before the loss.
1 turnHorizontal
position

LER

Fireball hypothesis

Verticalposition
2 trains

Bunch
current
Amount ofbeam loss

T. Abe at al., RF breakdown trigger, PR-AB 21, 122002, 2018.
M. Aversano

Trigger source can be collimator head.
Copper coating of collimator head will be effective if different sublimation point is problem.
14

Commissioning of Nonlinear Collimator: D05V1 in LERβ*
x = 384 mm / β*y = 48.6 mm
νx = 44.555 / νy = 46.624

Bx L K2 2=(y − x 2)
Δpy =
Bρ
2

B′′ 2
Bx = − (x − y 2)2
By = B′′xy

MSN AP !D05V 1

without D05V1 (day-1 optics)

✓

3.105
0.21737.69
2.311◆

with D05V1

SK2 = -6 m-2@SNAP

SK2 = 0 m-2@SNAP

Beam hits bottom head.

SNAP(skew sextupole magnet)

15

Touschek Lifetime: Simulation and Measurement
CW: Crab Waist
Ib+ = 0.62 mA/bunch, εy = 40 pm

Ib− = 0.50 mA/bunch, εy = 35 pm

Simulation and measured lifetime is consistent with each other.
CW 80 % reduces lifetime significantly.
Dynamic aperture for CW 80 % restricts lifetime.

Machine error should be taken into accountsuch as skew sextupole and skew octupole magnet
gradient error in QCS, dispersion error at strong sextupoles.
Collimator aperture is narrower than dynamic aperturefor β*
y = 1 mm. For β*y = 0.8 mm with CW 40 %,dynamic aperture restricts lifetime.

16

Cooling Water Temperature (Vacuum and Magnet System)
Vertical orbit fluctuation is affected by cooling water temperature of magnet system.
Vacuum system

Magnet system

returngoing

Cooling water system for vacuum system is very stable. If the heat load is lost due to abort, there is nothing that can be done.
Once the heat load is gone, the chiller will shut down for 30 minutes (for protection). This is the reason why it is recommended to slowly ramp up the beam current after abort.
17

HER injection point

K. Shibata

Tsukuba (Belle II)• Required upgrade to improve HER injection efficiency (what we have learned from beam
operation until 2022b);• Enlargement of the horizontal aperture of beam pipe
• Replacement of beam pipes at injection point with new one with larger aperture (last week)• Reduction of amplitude of horizontal oscillation of injected beam
• Replacement of injection septum magnet with new one with improved magnetic field (Oct.)
Aperture enlargement
is required here.

Fuji lab.
Electron
beam

D08
Fuji
straight section

wall

Septum mag. will
be replaced.

Stored beam
Injected beam
Septum mag.

M. Kikuchi (2021.12.03)
BITF meeting

Magnetic field will be
improved.
2023/26/June

BPAC

Beam pipes were
replaced.

19

Injector Linac upgrade #1
For injection efficiency
improvement;•••

New pulsed Quads for thesimultaneous dedicatedmatching of HER/LER
injection beam
New pulsed Quads for low
beta optics of HER injection
beam
Fast kicker for 2nd bunch
orbit correction

For stable operation;••

New accelerating structure
Replacement of air
conditioners in the tunnel

M. Satoh2023/26/June

BPAC

20

H. Ikeda

H. Ikeda

H. Ikeda

SR Simulation in HER

inner

outer

BLC2RE and B2E are same
sign of bending angle.

L-side

inner

outer

R-sideM. Kikuchi,
ITF Beam-Tuning
Sept. 19, 2023

Horizontal Orbit in the vicinity of IP
Orbit at IP

deviation from 41.5 mrad line

LER meas: Δx = -0.159 mm, Δpx = +0.363 mrad
Estimated from QC1R and QC1L BPMs.
HER meas: Δx = -1.006 mm, Δpx = -0.308 mrad
QC2R BPM

QC1R BPM QC1L BPM

e+

+
e-

LER: 2022/06/22 08:14:14
HER: 2022/06/22/08:13:03

e+design
QC2L BPM
orbit
+

+

HER: Δθx = +0.75 mrad (model)
outer

e+

ee+
designorbit

e-+modified eorbit

design
orbit

inner

R-side
HER: QC2RE: -0.7 mm

R-sideL-sideH-angle at IP for HER can be made by steerings outside of QCS.

HER: QC2LE: +0.7 mm

H-offset (LER -HER) : 0.847 mm
H-angle (LER -HER) : 0.671 mrad

L-sideZHQLC6RE, ZHQLC2RE, ZHQLC2LE, ZHQLC4LE
25

Synchrotron Radiation on PXD
outer (backward)

outer (forward)

After squeezing the horizontal beta at IP in HER from 80 mm to 60 mm
SR pattern on
the modules

e-

HER

inner

We scanned horizontal angle at IP in HER:
-0.14 mrad, +0.14 mrad, +0.28 mrad, +0.42 mrad
However, this angle adjustment affects
horizontal dispersions in HER.

26

Y. Ohnishi, Monday Meeting 2019 Dec. 16

Deterioration of Horizontal Dispersion for Horizontal Angle at IP in HER
H. Sugimoto

27

SR Simulation in HER

M. Kikuchi,
ITF Beam-Tuning
Sept. 19, 2023

Abort Statistics in 2021c
total aborts: 253 for 64 days
ave. 4.0 aborts / day
Belle II aborts: 147 (58.1 %)LER injection: 68
HER injection: 41

29

Abort Statistics in 2022ab
total aborts: 588 for 119 days
ave. 4.9 aborts / day
Belle II aborts: 316 (53.7 %)LER injection: 83
HER injection: 60

30

Aborts in 2022ab

Belle II
VXD diamond

Belle II
CLAWS +VXD diamond
Belle II
CLAWS

Loss
Monitor
D10-2

31

Number of Aborts per Day
2021c

2022ab32

2022abMachine Troubles
2021c
HER XRM trouble

HER

Monitor

2

HER optics dgradation due to earthquake

HER

Others2

Linac RF-gun laser trouble

Linac

Gun

2

HER RF D10AB KPS 66kV OPEN PHASE deu to air fan motor trouble

HER

RF

1

BTe BH1E_11_15 PS trouble

BTe

Magnet5Linac RF-gun laser trouble

Linac

Gun

4

HER XRM trouble

HER

Monitor

3

HER optics degradation deu to earthquake

HER

Others3

LER BWDNLP PS trouble

LER

Magnet3

LER RF D07C KLY OC

LER

RF

3

Linac magnet trouble (control)

Linac

Magnet3

BTp BPM FO trouble

BTp

Monitor

2

LER BLC2LP PS trouble

LER

Magnet2

LER RF D08 window temp

LER

RF

2

Linac network trouble

Linac

Control

2

QCS oxygen alarm due to Belle II environment monitor trouble

Belle II

Control

1

Belle II -KEKB gateway abort trouble

Belle II

Control

1

LER Cooling water pump trouble for D07AB dummy load

LER

Infrastructure

1

LER thyratron replacement and conditioning

LER

Injection

1

BTe VT17E PS trouble

BTe

Magnet1

LER XRM trouble

LER

Monitor1

BTe B1E magnet PS water stop

BTe

Magnet1

LER longitudinal FB cable trouble

LER

Monitor1

BTp/RTL BPM trouble

BTp

Monitor1

BTp BH1P PS down

BTp

Magnet1

DR injection kicker E/O trouble

DR

Control

1

HER abort kicker cooling system sequencer trouble

HER

Infrastructure1

HER septum trouble

HER

Injection

1

HER QD1E PS tracking error

HER

Magnet1

HER RF D10C tuner trouble

HER

RF

1

LER D02 chiller trouble

LER

Vacuum1

LC7 displacement monitor trouble

LER/HER

Monitor

1

QCS quench due to earthquake

LER/HER

Others1

QCS quench due to cryogenic operation error

LER/HER

Others1

IR cooling water trouble

LER/HER

Vacuum1

HER D04G μTCA trouble

HER

RF

1

M3 cooling water trouble

Linac

Infrastructure

1

HER RF D11: He control NIM PS trouble

HER

RF

1

LER thyratron replacement and conditiong

LER

Injection

1

LER 2-bunch injection trouble

LER

Injection

1

LER D07E SQC abort trouble

LER

RF

1

LER D04 vacuum trouble

LER

Vacuum1

QCS/ECS quench due to earthquake

LER/HER

Others1

Linac EVENT system trouble

Linac

Control1

Linac QDA23 PS trouble

Linac

Magnet1

Linac KL A3 trouble

Linac

RF

1

Linac KL 45 trouble

Linac

RF

1

M0A cooling water trouble

Linac

Infrastructure1

Linac SXC81 PS and QF1656 PS trouble

Linac

Magnet1

Linac KL 22 down

Linac

RF

1

Linac KL A1B trouble

Linac

RF

1