December 13, 2022

Overview of Commissioningin 2021c - 2022b
Y. Ohnishi / KEK
The 26th KEKB Accelerator Review Committee

Contents

Overview of 2021c and 2022ab beam commissioning
Achievements in 2021c - 2022b
Obstacles to luminosity improvement
Procedure of increasing beam currents and number of bunches with safe way

Luminosity performance
Specific luminosity
Beam-Beam parameter

Stability of Machine
Beam Lifetime and Dynamic Aperture2

2021c and 2022ab Run
2021c

2022abinjection kicker
accidental fires
in LER (Oct.28-Nov.5)

We reduced beam currents
after replacing the thyratrons
for their conditioning.

3

injection kicker
accidental firein LER (Mar.18)

Machine Parameters : 2021c - 2022b
Dec. 23, 2021c

June 8, 2022b

May 22, 2022b

Unit

Ring

LER

HER

LER

HER

LER

HER

Emittance

4.0

4.6

4.0

4.6

4.0

4.6

nm

Beam Current

1015

797

1321

1099

744

600

mA

1370

Number of bunches

2249

1565

Bunch current

0.741

0.582

0.587

0.489

0.475

0.383

mA

Horizontal size σx*

17.6

16.6

17.9

16.6

17.9

16.6

μm

Vertical cap sigma Σy*

0.339

0.303

0.250

μm *1

Vertical size σy*

0.240

0.215

0.177

μm *2

Betatron tunes νx / νy44.524 / 46.589 45.530 / 43.572 44.525 / 46.589 45.532 / 43.573 44.525 / 46.589 45.532 / 43.574

βx* / βy*80 / 1.0

60 / 1.0

80 / 1.0

60 / 1.0

80 / 0.8

60 / 0.8

Piwinski angle

10.7

12.7

10.7

12.7

10.7

12.7

Crab waist ratio

80

40

80

40

80

40

Beam-Beam parameterξySpeci c luminosity

0.04330.03150.04070.02790.03090.0219Luminosity%

6.45 x 1031

7.21 x 1031

8.74 x 1031

cm-2s-1/mA2

3.81 x 1034

4.65 x 1034

2.49 x 1034

cm-2s-1

4fimm*1) estimated by luminosity with assuming design bunch length*2) divide *1 by √2

Achievements until 2022 (1)Peak luminosity : 4.65 x 1034 cm-2s-1 (4.71 x 1034 cm-2s-1 w/o Belle II data taking and HV OFF)
Integrated luminosity : 424 fb-1 (491 fb-1)
Peak currents : 1.46 A (LER) / 1.14 A (HER), 2346 bunches (2-bucket spacing)β*y : 1 mm (0.8 mm) << bunch length ~6 mm → proof of the nano-beam scheme
Crab waist scheme has been applied (80 % in the LER, 40 % in the HER). → luminosity improvement
Beam-Beam parameter : 0.035 at 0.7 mA (0.045 at 1.1 mA for small number of bunches as machine
study)
Bunch-by-bunch FB tuning (gain, noise reduction) in the HER → luminosity improvements
Bunch-by-bunch FB tuning (number of taps) in the LER → suppress single bunch blowup, luminosity
improvements
Chromatic X-Y coupling correction with rotatable sextupoles in the LER → luminosity improvements5

Achievements until 2022 (2)Long-term drift of QCS magnetic field (beta-beat) ← reduced by new QCS initialization procedure
Orbit deviation due to IP knob tuning (beta-beat) ← suppressed with QCS corrector (ZHQC2RP)
Increase of positron charge for the LER injection : 3 nC at the end of e+ beam transport line
2-bunch injection for the LER and HER → improve injection efficiency (Bunch equalization is difficult.)
Adjustment of injection orbit in the HER (septum, kicker) → improve injection efficiency (not enough)Leakage orbit from injection kickers ← reduced by 60 % with additional inductance for the coils

6What Limits Luminosity Performance ?

Classification

A1

Remarks

Items

Single-beam causes. Luminosity becomes lower as increasing bunch current. (single-bunch)-1 mode instability

Single-beam causes. Luminosity becomes lower as increasing total current. (multi-bunch)coupled-bunch,degradation of optics(linear parameters) due
to beamline deformation

Single-beam causes, but interference of beam-beam interaction makes luminosity lower.

lattice nonlinearity(QCS fringe, chromatic
X-Y couplings, etc.)

Pure beam-beam interaction limits luminosity. Beam-Beam limit, etc.

crab-waist, resonances,coherent beam-beamhead-tail instability,
parasitic collision

A
A2

B

C

7

Obstacles to Luminosity Improvement
Beam blowup in the LER (single beam, non-collision) : "-1 mode instability" (A1)
Sudden beam loss (both rings, more serious in the LER) → "fireball hypothesis"
Damage of collimator head and/or QCS quench if large beam loss

Optics degradation due to beam current dependence of beam orbit (A2)
Orbit deviation at strong sextupoles is caused by beam line deformation due to intense SR heating.

Lower beam-beam parameter: 0.035 at 0.7 mA for physics run (0.045 at 1.1 mA) (B)
Short beam lifetime (dynamic aperture, physical aperture) : LER 8 min(1.25 A) / HER 25 min(1 A) nb=2346
Beam related background (optimization of collimators, QCS aperture and IR orbit)
Beam injection (small physical aperture of injection region, emittance growth in the beam transport line)
Earthquake : The beam aborts invariably. The εy becomes large in the HER. The optics correction is needed.
Lower online luminosity monitor during LER injection (Beam backgrounds affect the measured value.)8

Executive Summary from the 25th KEKB ARC Report

The most important challenges are:Top-up injection efficiency and injection stability, including HER beam blow up in the transfer line,
mitigating the consequences of accidental kicker-pulser misfiring, problematic HER two-bunch
injection, septum drifts, etc.
Collimation and machine protection strategy, including overcoming the present bunch intensity
limitations due to TMCI → -1 mode instability; developing a strategy for safe beam current
increase; and understanding and avoiding the as yet unexplained sudden large beam losses in the
LER.
Medium and long-term planning including possible upgrade paths; with an overall plan ofincreasing the beam currents, increasing the number of bunches, and lowering β*y to maximize theluminosity.

9

Accidental Fire of Injection Kicker in LER
2021c: We got several accidental fires in the LER at the early commissioning (Oct.28, Oct.30, Nov. 5). There isno accidental fire after the replacement of thyratrons and further conditioning.
Before starting 2022a, the thyratrons were rearranged and replaced with new one.
2022a: We observed large beam loss in the LER on March 18 due to accidental fire of injection kicker in the LER.
Then, the collimator head of D06H3 was damaged (broken). The thyratron was replaced and conditioned.
2022b: No accidental fire of the injection kickers
Accidental fire of injection kicker is caused by a lack of the thyratron conditioning or early failure.
If we use a well conditioned thyratron, there will be no accidental fire.
There is no accidental fire in the HER even though the applied voltage is higher than the LER. The thyratrons in
the HER are well conditioned.

Robust Low-Z (C) head is installed into D06H3 collimator during LS1. (used as the spoiler)
D06H1 on the upstream side is moved to the downstream side (D06H4) to collimate beam scattered by D06H3.
10

No Fatal Accident due to Large Sudden Beam Loss in 2021c
2021c

We had sudden beam loss for both rings.

Sudden Beam Loss
in HER← 1.2 A← 0.7 mA/bunch
Sudden Beam Loss
in LER

11

QCS Quench and Collimator Damage due to Sudden Beam Loss in 2022ab
D09V1

2022abJune 11
D09V1

D06V1
D09V1

← 1.2 Adeviation from plan

← 0.7 mA/bunch
D02V1

D06V1

D06V1

D06V1

D06V1
D06V1
D02V1

June 3
D06V1, D02V1

QCS (LER) quench
collimator damage

We introduced Matsuoka Limit Ib+ < 0.7 mA to avoid sudden large beam loss
which causes QCS quench and collimator damages as much as possible.
Sudden beam loss becomes a serious problem to increase total beam current.
12Luminosity Performance13

Specific Luminosity"estimated" means β*
y is calculated by the horizontal orbit deviation
at SLY(strong sextupoles) in HER due to beam-line deformation.

The geometricalluminosity
is good.
Luminosity drop
is too steep.

20 %
12 %

14

Specific Luminosity
The definition of specific luminosity:<latexit sha1_base64="umgITShbmUeUdlfc2EMk6n96NCk=">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</latexit>

Lsp =

L

1
/
⌃z ⌃⇤ynb Ib+ Ib

It was found that even if the setting is 1 mm, β*y can be shifted due to beta-beat caused by a deviation of
the horizontal beam orbit at the strong sextupoles in the local chromaticity correction.
The orbit deviation is caused by beam line deformation due to intense SR heating.
This effect is more significant for the HER rather than the LER.
2, but theHigher specific luminosity for β*
=
0.8
mm
is
obtainedatabunch
current
product
of
0.05
mA
y
specific luminosity rapidly decreases around 0.1 mA2.
2 and decreases to about 12 % at 0.1
Lsp for β*
=
0.8
mm
is
about
20
%
higher
than
1
mm
at
0.05
mA
y
mA2 and above.

This implies that the corrections of the chromatic X-Y coupling and other parameters are not optimized yet
for β*
y = 0.8 mm which affect beam-beam blowup.
15

Chromatic X-Y Coupling Correction with Rotatable Sextupoles in LER
Dec. 20, 2021

β*y = 1 mmsingle beamworking point

March 14, 2022

β*y = 1 mmΔr′1 = − 1single beam
The rotatable sextupoles (6 families for right and left side of IP) areused to make the first synchro-beta coupling resonance weak
together with the second resonance.

Δr′2 = 0
is optimal.

￼￼

SLYTLPs and SLYTRPs were not used here.
Rotatable sextupoles:
M. Masuzawa, T. Kawamoto et al.

16

Beam-Beam Parameterβ*y = 1 mm2021c

2022ab2022a HBC
(nb = 393)

The current
ratio : 6.5/4

ξy−~ 0.035 at Ib+ = 1.1 mA

physics run

physics run

ξy−~ 0.045 at Ib+ = 1.1 mA

Beam-Beam parameter has been improved compared to the 2021c run for higher bunch currents.
The chromatic X-Y couplings (r1' and r2') are corrected in the LER.
HBC = High Bunch current Collision17

Beam-Beam Interaction
Vertical beam-beam parameter (from luminosity)<latexit sha1_base64="f+qBtxase243HB2/Lv3nnHQoPSg=">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</latexit>⇠y± = 2ere

Vertical beam-beam parameter (incoherent)⇤y± L<latexit sha1_base64="cGv+iSeR2/7apCqYZlhpEXoC9u4=">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</latexit>

re
⇠y± =
2⇡ ±

± I±

✓

Ib⌥
ef0

◆

nominal bunch length⇤y±<latexit sha1_base64="JqTpg8GYwqc951KW2KAaPMsFdGE=">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</latexit>⇤x z⌥ y⌥z+ = 4.6 mm
z= 5.1 mm

Lower beam current in the HER tends to cause beam blowup.
This means that the HER beam size is more easy to blow-up when the beam current of the HER decreases.
<latexit sha1_base64="5Ow5osUkTqUYY9HI9RT91nSJuL8=">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</latexit>

The beam current of the HER is larger than the energy ratio (4 GeV / 7 GeV).

+ I+ <The optimum ratio of LER to HER beam current is 5:4 from luminosity tuning.
The beam-beam parameter of the LER are larger than that of the HER.
The current ratio is kept constant for daily operation in principle.
The beam-beam parameter is sluggish with LER beam currents of around 0.6 ~ 0.8 mA.
18

I

Contribution from Bunch Length
LER<latexit sha1_base64="s4zMvbfoVeQeKJvvHlruq+se2FU=">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</latexit>z+ = 5.46 mm

bunch lengthening

design bunch length<latexit sha1_base64="Uemt8VE6vDQfFuiUbWkFxbfnodU=">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</latexit>z+ = 4.6 mm

beam blowup

HER<latexit sha1_base64="MaZS4fgeK9NaPzFKPdQdjCjG+4s=">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</latexit>z= 6.02 mm<latexit sha1_base64="0pYDvsXwU4ji95B2UuGgej5LD48=">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</latexit>

design bunch length<latexit sha1_base64="XjmBNeIMe5dshmz9JcylR5aUicg=">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</latexit>zp

Lsp = L0sp p= 5.1 mm19<latexit sha1_base64="U796nSa7k4e5gToBdAStzTy/Be8=">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</latexit>( z+ (0))2 + ( z (0))2( z+ (Ib+ ))2 + ( z (Ib ))2z+ (Ib+ ) = 5.46 + 1.587 · Ib+ (mm)z

(Ib ) = 6.02 + 1.371 · Ib

(mm)

Ib+ : Ib- = 5 : 4

Stability of Machine20

Stability of Beam Orbit
Control of beam orbit as well as stability is very important.
The beam orbit cannot be considered in isolation from the beam optics.
BPM gain calibration is performed before optics correction, Quad-BPM (BBA) is sometimes performed if
necessary (after cabling work of BPMs).
Optics correction is scheduled every two weeks (maintenance day) or when we found luminosity degradation.
Magnet initialization is performed every maintenance.
We set the reference orbit, so called "GOLD orbit" when the optics correction is performed. But it is difficult toadjust a measured orbit to the GOLD orbit in several days after the registration.
Residual of measured orbit from GOLD orbit is typically 30 μm. This is not enough to keep optics stable.
Beam position at the strong sextupole is important to correct X-Y couplings and vertical dispersions.
Degradation of consistency, beam-line deformation, change of BPM cable length due to temperature at day and night, etc.

There are many sources to induce orbit fluctuation. Cooling water cycle, all environment as well as earthquake
Moreover, SR becomes intense and the heating might deform the beam-line. Difficulties arise how to treat of theorbit.
Orbit in the vicinity of the IP is not well understood as well as QCS magnetic field.
21

Δx (mm)

LER
Estimated orbit at the IP

Δy (mm)A - GOLD

B-A

Δx (mm)B

The difference between themeasured orbit and the GOLD
orbit becomes large in several
days after optics corrections.

B - GOLD
Δy (mm)A

We can correct B-A, but neither
A-GOLD nor B-GOLD can becorrected.

i=1

N

r
N
X 1
<latexit sha1_base64="/lF0ywoA8+/tiFHplELNi2id1dI=">AAACkXicSyrIySwuMTC4ycjEzMLKxs7BycXNw8vHLyAoFFacX1qUnBqanJ+TXxSRlFicmpOZlxpaklmSkxpRUJSamJuUkxqelO0Mkg8vSy0qzszPCympLEiNzU1Mz8tMy0xOLAEKxQvoxBSX5sZXZ9oa1sb5xRQXFpVUx6QVJSZXG9ZW+9VqVMZn6lbGV6dn1mrGGdXGCygb6BmAgQImwxDKUGaAgoB8geUMMQwpDPkMyQylDLkMqQx5DCVAdg5DIkMxEEYzGDIYMBQAxWIZqoFiRUBWJlg+laGWgQuotxSoKhWoIhEomg0k04G8aKhoHpAPMrMYrDsZaEsOEBcBdSowqBpcNVhp8NnghMFqg5cGf3CaVQ02A+SWSiCdBNGbWhDP3yUR/J2grlwgXcKQgdCF180lDGkMFmC3ZgLdXgAWAfkiGaK/rGr652CrINVqNYNFBq+B7l9ocNPgMNAHeWVfkpcGpgbNZuACR4AlCJjCgxuTEWakZ2imZxJoouzgAI0KDgZpBiUGDWB4mzM4MHgwBDCEAu2dxLCD4SDDISZhJksmByYniFImRqgeYQYUwOQNAETVm5c=</latexit>

(yi

ygi

)2
i=1

r
N
X
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1(xiNxgi )2

Residual of Measured Orbit from GOLD Orbit in 2022ab

LER
HER

optics correction,
GOLD is registered.

optics correction,
GOLD is registered.

23/users/onishi/svn-work/SuperKEKB/operation/2022ab/momentum

Beam Lifetime and Dynamic Aperture24

Lifetime Evaluations in LER
2021c

We tested three different kinds of sextupole settings in the LER. (Original, proposed by Y. Cai, B2)
Assuming constant gas pressure and beam emittances during the measurements, the itting out lifetimes (w/ bunch current of 1 mA) are
Optics parameters (I= 50 mA, 1370 bunches)

Lifetime (sec)Δηy [mm]εy [pm]ξx/y

IP knobs

original

4.2

4.5

~20

-1.24/3.58≠0Yunhai

5.3

3.7

~20

-1.24/3.66

0

B2

6.5

7.9

~20

0.1/1.90Ib = 0.6 mA

Ib = 1 mA

original

843 ± 14716 ± 7

Yunhai825 ± 14662 ± 8B2761 ± 13596 ± 81/τ is not a straight line,
it is different between lowerand higher than 0.6~0.7 mA.
<latexit sha1_base64="VxjwQoKrcgdoA0UvUKqmaOVHO1o=">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</latexit>

1= cT Ib+⌧T

1/τ (1/s)(Δβ/β)y [%]Bunch current (mA)
Vertical emittance is uncertain at high bunch current
due to beam blowup (-1 mode instability).
25
fSingle bunch current was measured by DCCT.
No information of beam size from XRM.

Simulation of Dynamic Aperture in the LER
Crab-Waist : 80 %Emittance: εx = 4 nm/εy = 20 pm

Ib+ = 0.6 mA

without collimator aperture (QCS only)
initial phase = 0, π/2

Original

300 sec @ 1 mA

YunhaiB2

larger momentum acceptance than original

8.2 min

6.3 min

8.5 min

The Touschek lifetime is evaluated by an ellipse inscribed in the dynamic aperture (stable region). → too short lifetime
Lifetime (sec)There are various methods of evaluation and lifetime depends on the method from DA.
Vertical emittance is uncertain at 1 mA bunch current (larger than 20 pm or bunch lengthening).
26

Ib = 0.6 mA

Ib = 1 mA

original

843 ± 14716 ± 7

Yunhai825 ± 14662 ± 8B2761 ± 13596 ± 8LER

Beam Lifetime and Vertical Emittance

HER

2021b
nb:1174

current

1174

nb:1174

ver. emittance
60 pm

nb:393
nb:39322 pm

collision

45 pm

25 pm

single beamcollision

single beamεy depends on bunch current.

Lifetime
30 min

8 min
7 min

26 min

HER

βx*

80 mm

60 mm

βy*

1 mm

1 mm

I

800 mA

650 mA

nb

1174

1174

40 pm

28 pm

1174

LER

32 minIb

0.681 mA 0.545 mA

εycollision

60 pm

45 pm

εy
single

25 pm

40 pm

life
collision

8 min

30 minlife
single6 min

32 mine+inj: 2.3 nC x 2 x 12.5 Hz x 80 %Imax= 1.5 A for lifetime: 8 min

6 min
27

Simulation of Dynamic Aperture and Lifetime
Open and close the collimator uniformly from the nominal setting to examine the change in lifetime.
LER
HER
Zero means the nominal setting for the collimators.

Horizontal
DA > PA

Horizontal
DA ~ PA

1 mm

200 μm

Vertical
DA > PA

100 μmτ = 8 min(meas. 6 min,vac. lifetime inc.)

VerticalDA < PAThe simulation isalmost consistent withmeasurement.

100 μmτ = 52 min(meas. 32 min,vac. lifetime inc.)
Dynamic aperture issmaller than what
we expected ?
Or machine error ?

28

No Summary-1 mode instability

K.Ohmi"Impedance issues (BxB FB, etc.)"

Dec. 14

Sudden beam loss

H. Ikeda"Sudden Beam Loss"

Dec. 14

Optics degradation and others

H. Sugimoto"Optics issues"

Dec. 14Beam-Beam simulations,interference of lattice nonlinear, etc.

D. Zhou"Beam-Beam, comparison of Beam-Beam interaction
between simulations and experiments"

Dec. 14Collimators

T. Ishibashi"Collimator issues"

Dec. 14Issues of beam injection

N. Iida"Injection"

Dec. 1329

Appendix

30

2019 a/b

2020 a/b

8%

5%2021a/b

4%

6% 3%
2%

7%

1%
37%

22%

2022a/b

5%

16%

4%

15%

28%
59%

4%

72%

73%
28%

Physics Run
TroublesMachine Tuning
Maintenance, Others

Machine Study

Physics Run
TroublesMachine Tuning
Maintenance, Others

2019 cMachine Study

Physics Run
TroublesMachine Tuning
Maintenance, Others

2020cMachine Study
Physics Run
TroublesMachine Tuning
Maintenance, Others

Machine Study

2021 c
3%

4%

12%

4%

12%

28%

Operation statistics
2019 -2022

10%
37%

18%

23%

60%

47%

42%

Physics Run
TroublesMachine Tuning
Maintenance, Others

Machine Study

Physics Run
TroublesMachine Tuning
Maintenance, Others

Machine Study

Physics Run
TroublesMachine Tuning
Maintenance, Others

Machine Study

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⇤2
2
=
µ
"y
y

✓

s

⇤
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2

⇤
y

= µ "y y⇤ + (⌘y⇤2◆

+ (⌘y⇤

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⇤
2
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⇤
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+
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(r
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4
3
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⇤ ⇤2
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x x r1⇤ 2

x

X-Y couplings
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01physical coordinate

0

1

0

0

1

0

u
⌘u
µ
B pu C B ⌘ p u C
B 0
B
C+B
C =B
@ v A @ ⌘v A
@ r1
pv
⌘pv
r3
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B
C=B@ ⌘ v A @ r1
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r3

0
µ
r2
r4

0
µ
r2
r4

r4
r3
µ
0

r4
r3
µ
0

10

1

10

1

r2
x
B px C
r1 C
CBC
0 A@ y Aµpyr2⌘xB ⌘px C
r1 C
CBC
0 A @ ⌘y Aµ
⌘py

Vertical emittance, vertical dispersion, coupling parameters r1 and r2 at the IP are fundamental parameters for luminosity performance.
32

Beam-Beam Parameters2022absingle beamemittanceβ*y = 1 mm

Vertical beam-beam parameter0εy−= 40 pm⇤y± L<latexit sha1_base64="f+qBtxase243HB2/Lv3nnHQoPSg=">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</latexit>⇠y± = 2ere0
εy+= 25 pm± I±

Vertical beam-beam parameter (incoherent)<latexit sha1_base64="Vh38dlIlY9wLx8S+zi0QGsnmtB8=">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</latexit>

re
⇠y± =
2⇡ ±
Beam-Beam parameter
appears to be saturated
at 0.6 mA.

✓

Ib⌥
ef0

◆

<latexit sha1_base64="/yegeatniFTgn4h7wFJhTTNwJv0=">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</latexit>⇤y±⇤x z⌥ y⌥

/ Ib⌥

⇤
y±

"y⌥

Here, the nominal bunch length is used.
<latexit sha1_base64="JqTpg8GYwqc951KW2KAaPMsFdGE=">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</latexit>

Bunch lengthening is important parameter.

z+ = 4.6 mm
z

33

s

= 5.1 mm

Beam Size in 2021c

2021c

2021c
2021c HBC

ΔR1', LER νy← 6.0 nm
2021c HBC

lower νx in the LER

bunch current product34

bunch current← 4.5 nm← 3.6 nmlower νx in the LER

Location of Movable Collimators
Collimators and Radiation Dose (measured on June 22, 2022)
LER

measured by Radiation Safety Group

HER

D06H3
17 m

Injection
Point
D06H3 damaged
due to accidental fire of
injection kicker on March 18

e+ →

D02H3

D09H1

D12V4

IP

← e-

Injection
Point

D02H3 is 17 m downstream of D02V1
which is damaged on March 11.

The bottom jaw of D06V1 was opened from the usual setting due todamage of the collimator head. In stead of D06V1, D06V2 was used toprotect D02V1 and QCS from mid. of June.
35

The radiation dose at the injection point is very high in HER.

Local Chromaticity Correction: Strong Sextupoles (SLY)LER

Right-side

Left-side

-I'

-I'

K2: 1.23 1/m2

K2: 3.48 1/m2

K2: 1.33 1/m2

βy = 521 m
Δνy =

βy

K2Δx

HER

β*
y = 1 mm~0.0028 for Δx = 20 μm

4π
Horizontal tune shift can be ignored.

K2: 3.53 1/m2

Right-side

Left-side

-I'

-I'

K2: -8.76 1/m2

K2: -9.62 1/m2

βy = 702 m

βy = 525 m

Horizontal orbit in-phase for each pair
induces large beta-beat which changes β*y.
36

K2: 8.36 1/m2

K2: 7.66 1/m2

βy = 675 m
Δνy ~0.01 for Δx = 20 μm
3.6 times larger than LER

Beta-Beat due to Orbit Deviation
H. Sugimoto, 2022ab Summary Meeting

The SR heating deforms the beam line.
The horizontal orbit deviation induces tune shift and beta-beat. As the result, β*y also changes.
The orbit deviation in the local chromaticity correction (SLY) is always in the outward direction of the ring.
This implies a squeezing of β*y.
The HER is larger effects rather than the LER.
In order to reduce optics degradation, the local bumps correct the orbit at the strong sextupoles.
(Horizontal bump for beta-beat and vertical bump for X-Y couplings)

37

Measurement of Resistive-Wall Tune Shift

β*
x /β*
y = 200 mm/8 mm (no crab waist)

The bunch current is fixed to be 0.2 mA.
10 μm

nb: 783

nb: 978

10 μm

nb: 1565

nb: 393reference
2 μm
2 μm

referencetune shift due to Δνx /I = + 2.2 × 10−5 (1/mA)
resistive wall
−5
Δν
/I
=
−
2.0
×
10
(1/mA)
yimpedance:→ − 1.64 × 10−5 (1/mA)
corrected value

18:50 - 23:10, October 26, 2021

10 μm

10 μm

HER

Dynamic Aperture in the LER

CW 80 %

initial amplitude at injection point

Collimators : full open, QCS aperture only

QC1

δ0 = − σδδ0 = 0δ0 = + σδ

QC2

AQC1: AY =20.0 mm
AQC1: AY =18.0 mm
AQC1: AY =13.5 mm

Tested three different
vertical apertures for
QC1

Horizontal dynamic aperture is reduced by the crab waist scheme.
If the vertical physical aperture of QC1P is increased to 17 mm, the stable region is extended in the small horizontal amplitude.
(Above 17 mm is limited by the dynamic aperture.)is determined by the physical aperture of QC1 and QC2

δ0 = − σδ

CW 0 %

δ0 = 0δ0 = + σδIntra-Beam Scattering in LERεy (pm)Ib = 0.6 mA

εx (nm)40