Emittance Preservation
SuperKEKB review
July 9th, 2019
Y. Seimiya
for Emittance Preservation Task Force Group
Iida gives this presentation instead of Seimiya-san who has sudden illness.

SuperKEKB Review in 2018

R8.1: Perform several further analyses to identify the sources of beam jitter as
detailed in the following recommendations.
•
•
•
•
•
•
•

R8.2: The analysis should include the calculation and study of the Bmag term,
which characterizes mismatch in the optics functions. Expand the formulae toinclude this term.
R8.3: Calculate the normalized position jitter amplitude to remove the effect of t
he beam optics.
R8.4: Compare the normalized jitter amplitude and its evolution to the beam loss
locations and an aperture model.
R8.5: Determine the frequency contents of the beam position jitter. In case that
dominant frequencies in the position jitter are found correlate them to possible
technical sources.
R8.6: Perform a quantitative analysis of energy jitter, dispersion and observed beam position jitter to see what part of the position jitter can be explained byenergy jitter and what fraction remains unexplained.
R8.7: Perform a careful and rigorous study on the timing jitter of the RF trigger
and the gun trigger, which might explain the observed energy jitter.
R8.8: In case that further wakefield studies are performed, investigate theposition-dependent direct wakefield kick in linear order, which should bemeasurable for strong wakefields, as they are required for creating beam position
jitter.

We partly answer about green items in my slide. Purple items have not been
preformed yet. We will investigate purple items as soon as possible.

2

Outline
1. Requirement for SuperKEKB
2. Sources of Emittance GrowthA) Residual DispersionB) Beam Phase Space JitterC) Wakefield in Acceleration StructureD) Acceleration of Beam with DispersionE) Radiation Excitation

3. Results of Emittance Measurement
4. Summary3

1. Requirement for SuperKEKB•••

For the e-/e+, initial emittance is at RF
gun/extraction line of DR.
We have to realize the high quality beamtransportation to main ring without
emittance growth as far as possible.
Otherwise, injection rate is worse andluminosity can not reach the target value.

Phase 3(Mar. 2019 −)

final
Beam

e+

e–

Bunch
charge (nC)44

Initial Emit.
(gbe) (µm)
Emit.
@BT end(gbe) (µm)
EnergyspreadA footprint of LINAC and BT
J-ARCSectorA

RTL

Jarc

SectorB

Electron Gun

SectorC

Sector1

Sector2

Sector3

Positron Generation Target

Sector5

LINAC end

10/10

(Hor./Ver.)(Hor./Ver.)

100/1540/20(Hor./Ver.)(Hor./Ver.)

0.16%

0.07%

BT2-e

e+
Sector4

64/0.8RF gun:eV HE RG
7 E KB e
rK
e
p
Su
WS:

DR (damping ring for e+)
LTR

DR:

WS:
BT2-p

Beam Transport lines(BT)

V LER WS:e
BT1
4 G E KBK
er
BT (Beam Transport line)puS4

2. Sources of Emittance Growth
Candidates of emittance growth in LINAC or BT.
A) Residual Dispersion–

Through the residual dispersion, the energy spread converts to the beam size.

B) Beam Phase Space Jitter–

The emittance that includes beam phase space jitter, called as effective
emittance, must be satisfy the SuperKEKB requirement.

C) Wakefield in Acceleration Structure––

Wakefield, generated by a head of bunch, kicks its own tail.
Thus if the beam is off-centered in the structure, the transverse wakefield
increases beam emittance.

D) Acceleration of Beam with Dispersion–

If a beam, which has dispersion, is accelerated by acceleration cavity with offphase, the energy deviation converts to betatron oscillations and causes
emittance growth.

E) Radiation Excitation––

Radiation excitation effect on emittance is proportional to both Lorenz gamma
to the fifth power and inverse of curvature radius to the third power.
Especially, electron beam (7 GeV) is strongly affected by the radiation excitation
effect.
5A) Residual Dispersion

A) Residual Dispersion in LINAC• Large residual dispersion had been observed at the J-ARC before
dispersion correction.
• By tuning the strength of quadrupole magnets, residual dispersion
became small.
J-ARC

J-ARC

Designx=⌘<latexit sha1_base64="/j+sXJ8fXHgB3mLaSsIyeYHmdjs=">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</latexit>

p
p

=⌘

m

Measured

BeforeRMS Dhx = 0.43 m

gbex = 187  27 µm

Thermionic gunm

Measured

After

Dispersion
correction

Δgbex = -47 µm

m
RMS Dhx = 0.02 m

gbex = 140  33 µm

6A) Residual DispersionA) Other sources of Residual Dispersion• Both orbit and angle of a beam which pass through bending magnets.

• Orbit displacement at quadrupole magnets that have a large strength creates asizable dispersion.
• Orbit of a beam which pass through sextupole magnets.
To keep residual dispersion minimized, orbit feedback is necessary.
Dependence between orbit+angle and dispersion

Effect of sextupole magnets••

Orbit & angle
correction
before J-ARC
Orbit & angle
correction
before chicane

There are 6 sextupole in J-ARC.
Orbit displacement cause
quadratic force.

ON

OFF

LINAC end

J-ARC

Chicane

LINAC end7A) Residual DispersionA) Orbit Feedback•••

An example of orbit FB (Shown BPM place in the LINAC end)
Orbit FB at the end of LINAC was operated correctly.
Orbit FB of J-ARC upstream will be performed next run.

BeforeAfter

8A) Residual DispersionA) Magnet used in the orbit FB at the end of BT
LINAC FB start

LINAC FB start

The orbit FB in LINAC helps thr orbit FB in the BT.

9A) Residual Dispersion

A) Residual Dispersion at BT line••••

We had corrected dispersion of each BT ARC one by one.
After that dispersion of the BT overall was measured changing thebeam energy.
Non-negligible residual dispersion was still observed.
We will minimize Δη and Δηʼ at the end of BT in the autumn run.
Straight line Straight line
Straight line Straight line
(WS@BT)(WS@BT2)(WS@BT1)(WS@BT2)

BT for e-

BT for e+

10

2. Sources of Emittance Growth
Candidates of emittance growth in LINAC or BT.
A) Residual Dispersion–

Through the residual dispersion, the energy spread converts to the beam size.

B) Beam Phase Space Jitter–

The emittance that includes beam phase space jitter, called as effective
emittance, must be satisfy the SuperKEKB requirement.

C) Wakefield in Acceleration Structure––

Wakefield, generated by a head of bunch, kicks its own tail.
Thus if the beam is off-centered in the structure, the transverse wakefield
increases beam emittance.

D) Acceleration of Beam with Dispersion–

If a beam, which has dispersion, is accelerated by acceleration cavity with offphase, the energy deviation converts to betatron oscillations and causes
emittance growth.

E) Radiation Excitation––

Radiation excitation effect on emittance is proportional to both Lorenz gamma
to the fifth power and inverse of curvature radius to the third power.
Especially, electron beam (7 GeV) is strongly affected by the radiation excitation
effect.
11B) Beam Phase Space JitterB) Beam Phase Space Jitter• In 2018, large orbit jitter was measured (1000 shots).
• Emittance estimated from beam jitter, called jitter emittance, was
not negligible.

1nC

J-ARC

e+ target
Bunchcharge (nC)

Orbit jitter (RMS)Emit.
@BT end(gbe) (µm)
Emittance growth
converted from beam jitter

Phase 3
final

4
40/20

(Hor./Ver.)

Linac end:

28/7 μm(Hor./Ver.)q✏ef f = ✏20 + ✏2j + 2✏0 ✏j Bjmag

Design beta function<latexit sha1_base64="upxAsRlptP+Rek8PX09m+E6HLjc=">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</latexit>m✏0 + ✏j

Bjmag ( 1) express amount of
mismatching between beam optics
and the jitter optics.

LINAC end

12B) Beam Phase Space JitterB) Wakefield effect and Beam Phase Space Jitter• Electron beam straightly pass through the positron generation
target hole, whose diameter is 2 mm.
• We suspected wakefield effect as a orbit jitter source.

ewake potential induced bytarget hole (simulation)
Color differences show differencesof distance between center of holeand beam position.

14 mm

e+
e-

From the beam position before
and after target, amplification
factor are derived.

φ2 mmComparison of orbit jitter
Target IN

Growth factor20

Target OUT

Growth factor of beam phase space jitter:

LINAC end

< 0.1@1nC << Measured growth factor

Wakefield effect of target hole is negligibly small.
13B) Beam Phase Space Jitter

B) Dispersion and Beam Phase Space Jitter• We focus on dispersion which convert to orbit jitter through energy jitter.
• By dispersion correction, jitter emittance become less than 1 µm.
J-ARC e+ target

J-ARC e+ target

BeforeAfter

Dispersion
Correction

Linac end:

gbej < 1 μm

14B) Beam Phase Space JitterB) b Function and Orbit Jitter• Remain orbit jitter can be explained by b function.
• Using Twiss parameters measured by WS at C sector, b function
near target is derived.
• b function is highly correlated with orbit jitter.
• We conclude that large orbit jitter sources are mainly bothresidual dispersion and b function.

15B) Beam Phase Space Jitter

B) Other Sources of Beam Phase Space Jitter•

By further investigation, we found that following items were sometimes sources ofjitter. Pulse magnet and RF phase jitter was almost resolved by person in charge.
To identify the jitter source, monitoring beam jitter is important.

Binarization of Pulse Magnet

Three valued RF phase
Large RF phase jitter cause orbit jitter.

x’ [mrad]•x [mm]
Slope of RF phaseΔp/p=0.042%

Δp/p=0.027%

Near zero cross phase

Near crest phase

If RF phase is near zero cross, energy jitter is enlarged
by the slope of phase.

Degree@KL_B3

Degree@KL_C8

16B) Beam Phase Space JitterB) Beam Phase Space Jitter at BT line•••

In the RTL and BT, orbit jitter is much larger than that in LINAC, partly because BPM resolution is poor.
Orbit jitter of first straight line in BT is about ~150 μm@1σ. This value is probably BPM resolution.
Assumed that calculated jitter emittance at the first straight line came from BPM resolution, jitter emittance atsecond straight line is estimated as following:• e- beam: gbejx/gbejy @BT end ~ 40/50 μm• e+ beam: gbejx/gbejy @BT end ~ 30/30 μm• High resolution BPM is strongly desirable at BT. An upgrade of some BPMs for higher resolution isplanned.

e-

Straight line

e+

BT

RTL

LINAC

WS@B
WS@C

WS@3

WS@5

WS@BT1

WS@BT2

Straight line

LINAC

WS@3

BT

WS@5

WS@BT1

17

WS@BT2

2. Sources of Emittance Growth
Candidates of emittance growth in LINAC or BT.
A) Residual Dispersion–

Through the residual dispersion, the energy spread converts to the beam size.

B) Beam Phase Space Jitter–

The emittance that includes beam phase space jitter, called as effective
emittance, must be satisfy the SuperKEKB requirement.

C) Wakefield in Acceleration Structure––

Wakefield, generated by a head of bunch, kicks its own tail.
Thus if the beam is off-centered in the structure, the transverse wakefield
increases beam emittance.

D) Acceleration of Beam with Dispersion–

If a beam, which has dispersion, is accelerated by acceleration cavity with offphase, the energy deviation converts to betatron oscillations and causes
emittance growth.

E) Radiation Excitation––

Radiation excitation effect on emittance is proportional to both Lorenz gamma
to the fifth power and inverse of curvature radius to the third power.
Especially, electron beam (7 GeV) is strongly affected by the radiation excitation
effect.
18

C) Wakefield in Acceleration StructureC) Wakefield in Acceleration Structure•••

Using a steering magnet, we searched an orbit so as tominimize emittance.
Emittance highly depends on beam charge and orbit.
Wake free steering will be performed using RF gun in the nextrun.
Thermionic gun

1nC

4nC

19

2. Sources of Emittance Growth
Candidates of emittance growth in LINAC or BT.
A) Residual Dispersion–

Through the residual dispersion, the energy spread converts to the beam size.

B) Beam Phase Space Jitter–

The emittance that includes beam phase space jitter, called as effective
emittance, must be satisfy the SuperKEKB requirement.

C) Wakefield in Acceleration Structure––

Wakefield, generated by a head of bunch, kicks its own tail.
Thus if the beam is off-centered in the structure, the transverse wakefield
increases beam emittance.

D) Acceleration of Beam with Dispersion–

If a beam, which has dispersion, is accelerated by acceleration cavity with offphase, the energy deviation converts to betatron oscillations and causes
emittance growth.

E) Radiation Excitation––

Radiation excitation effect on emittance is proportional to both Lorenz gamma
to the fifth power and inverse of curvature radius to the third power.
Especially, electron beam (7 GeV) is strongly affected by the radiation excitation
effect.
20

D) Accelerationof Beam witg DispersionD) Acceleration of Beam with Dispersion••

If a beam, which has dispersion, is accelerated by RF cavity, hd converts tobetatron oscillations and causes emittance growth.
From measured dispersion, the dispersion is leak to RF cavity in ECS of SY3

M. Kikuchi
Measured dispersion from ECS in SY3.
There is dispersion at ECS cavity though design
dispersion is zero at the point.

If the cavity has non-zero dispersion, a beam, gaining its
energy depending on z, has net growth in the projectedemittance.
This is an analogue of the synchro-beta excitation at thecavity with non-zero dispersion in the ring.

✏⇠2
Simulation result:✏0<latexit sha1_base64="hD8mNHKhEfmdSxjCHs42ZA6LnMw=">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</latexit>
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21D) Accelerationof Beam witg Dispersion

The bending magnets in ECS/SY3 haveD) Quadrupole component of bending magnet• BL measurement data shows that non-negligible quadrupole
component of bending magnet exists.
• Assumed measured quadrupole component, simulation satisfy
measured dispersion well.
• We will move the each bending magnet about 10 mm in this summer.
• If the qudrupole component still remained in autumn operation, weare also planning to installing a quad in the center of the chicane.
T. MoriThis can explaine the measured dispersion leak.
Slope is quadrupole component.

~10 mmBL of bending magnet along to beam orbit22

2. Sources of Emittance Growth
Candidates of emittance growth in LINAC or BT.
A) Residual Dispersion–

Through the residual dispersion, the energy spread converts to the beam size.

B) Beam Phase Space Jitter–

The emittance that includes beam phase space jitter, called as effective
emittance, must be satisfy the SuperKEKB requirement.

C) Wakefield in Acceleration Structure––

Wakefield, generated by a head of bunch, kicks its own tail.
Thus if the beam is off-centered in the structure, the transverse wakefield
increases beam emittance.

D) Acceleration of Beam with Dispersion–

If a beam, which has dispersion, is accelerated by acceleration cavity with offphase, the energy deviation converts to betatron oscillations and causes
emittance growth.

E) Radiation Excitation––

Radiation excitation effect on emittance is proportional to both Lorenz gamma
to the fifth power and inverse of curvature radius to the third power.
Especially, electron beam (7 GeV) is strongly affected by the radiation excitation
effect.
23

E) Radiation ExcitationE) Emittance growth induced by radiation excitation in BT
Theoretical emittance growth induced by radiation
excitation:

BT2∝ g5, 1/r3
BT2

Particle tracking simulation was performed from the endof LINAC to the end of BT.

Simulation

InitialWith
Phase-III final
particles Radiation requirementBT1e- (7 GeV) gbex [µm]206540 -> The maximum emittance can be relaxed.

e+ (4 GeV) gbex [µm]

64

74

100

• Radiation excitation has little dependence
on initial emittance.
• By the radiation excitation, emittance
growth of e-/e+ beam is about 48/10 µm.

M. Kikuchi Simulation Result

gex = 65 µm
gex = 20 µm

Now in re-considering

e- beam• The beam size at the injection septum is 0.31mm, assuming βx = 20 m. The required
injection aperture is still dominated by the
septum width of 2.5 mm. Although theemittance growth due to synchrotron
radiation is very big, it plays only a minor role24
on the injection aperture itself.

Outline
1. Requirement for SuperKEKB
2. Sources of Emittance GrowthA) Residual DispersionB) Beam Phase Space JitterC) Wakefield in Acceleration StructureD) Acceleration of Beam with DispersionE) Radiation Excitation

3. Results of Emittance Measurement
4. Summary25

3. Results of Emittance Measurement (e-)

•
•
•
•
•
•
•

Unfortunately, tuning time of the LINAC was seriously limited in Phase 3.
Emittance in Phase 3 is worse than that in Phase 2.
Though residual dispersion and jitter emittance is small in LINAC, emittance growth perhaps
come from wakefield of cavity.
Measured emittance at 27/Jun is worse than 10/Jun without special tuning.
We hope that orbit FB, which start from 20/Jun, hold emittance quality.
In the end of BT, emittance growth occurred. Vertical emittance can be explained by bothresidual dispersion and jitter emittance.
It seems that measured horizontal emittance growth at BT2 is larger than that of both residual
dispersion and jitter emittance. We are investigating this reason now.

X

Y
1 nC

B

C

3 5 BT1 BT2

N. IidaT. Mori
M. Kikuchi

BC

3 5 BT1 BT2
26

3. Results of Emittance Measurement (e+)• In Phase 3, emittance growth was almost same as that in Phase 2.
• Emittance growth under ECS off was smaller than that under ECS on.
• Vertical emittance growth between BT1 and BT2 can be explained byresidual dispersion and jitter emittance.
• While, ratio of the horizontal emittance at BT2 to that at sector 5 isabout 4 though simulation result is 2. We are investigating this reason
now.

Y

X
1 nC

2019.6.28

3

N. IidaT. Mori
M. Kikuchi

5 BT1 BT23 5 BT1 BT2
27

SUMMARY••In LINAC and BT, high charge and low emittance beamtransportation is necessary for SuperKEKB project.
Current main emittance growth sources are residual dispersion(beam phase space jitter), wakefield in acceleration cavity, andacceleration of beam with dispersion.

Countermeasure:
Residual dispersion:− Minimize Δη and Δηʼ in the BT end.

Wakefield in acceleration cavity:− For the main ring operation, tuning time of the LINAC was seriously limited.
For stable low emittance transportation, continuous emittance measurement
is strongly desirable. We will consider new diagnostic line at BT.
− Automatic orbit correction for minimizing emittance growth is also desirable.
We will introduce such wake free steering program using a screen in the newline, for example.

Acceleration of beam with dispersion:− The bending manets realignment and the quad installation in the ECS of SY3
are planned so as to cancel the quadrupole component of the bending
magnet.
28

Back up2930A) Residual dispersion in the DR extraction line•

This table shows values of residual dispersion before and after correction.

• Residual dispersion became smaller in both ARCs.
• In 1st ARC, residual dispersion is not still small enough.
<hx2>1/2 [m]e+There are two
ARCs in the DR
extraction line.

<hy2>1/2 [m]Fudge Factor of
Quad.

Correction

BeforeAfter

BeforeAfter[%]

2nd ARC

0.079

0.019

0.00940.0077- 4.5

1st ARC

1.05

0.09

0.02

0.01

- 8.2

Example: 1st ARC

Need more study
BeforeY. Seimiya,
N. Iida,M. Kikuchi

After dispersion correction

Optics of theextraction line

The third graphshows residual
dispersion.
Blue is horizontal
and red is vertical.

Extraction Kicker
Extraction Septum

DC Bends

31A) Residual dispersion and emittance growth
Emittance improvement by dispersion correction
Residual Dispersion/Normalized EmittanceDR designe+emittance

0.7 [nC]<hx2>1/2[m]gbex [µm]Before correction

After 2nd ARC correction

0.079
1.05
29344.5

0.019
19222.4

After 1st ARC correction

0.09
1268.2

64.3• Horizontal emittance became less than half
• It is still twice as large as that of DR design.

CSR calculation (depend on beam charge and bunch length)
CSR wake potential

x 10-5

D. Zhou
ΔP/P

Theoretical
Analytical

1
W (z) =
2⇡<latexit sha1_base64="2axviYwfkhmdl0aDWNtscDlFkPM=">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</latexit>

Tracking Result

Z 1

1

Charge [nC]Δgbex/gbex

0.7

3.2 x 10-6

4

3.1 x 10-5

• CSR at RTL is negligible.

d!Z(!) (!)e

i!
cz

32

A) Residual dispersion in BT• Until BT-Wire Scanner (WS) position, dispersion correction was done.
• In some ARC, dispersion correction is not finished. → Continue to Phase-III
As a same manner,
we corrected
dispersion in each
ARC of BT.
This table shows
residual dispersion
before and after
correction for eand e+ beam.
These ARC names
are listed from the
upstream of thebeam line.

eCorrection<hx2>1/2 [m]<hy2>1/2 [m]Quad
Fudge Factor

BeforeAfter

BeforeAfter[%]

Slope

0.13

0.11

0.05

0.01

1.05.9

BTe Arc#0

0.11

0.02

0.01

0.02

06.7

BTe Arc#1

0.102

0.038

0.029

0.036

2.37

BTe Arc#2&3

0.066

0.029

0.037

0.034

2.52

Slope

0.104

0.091

0.192

0.015

3.55

BTe Arc#4

e+Correction

2.17<hx2>1/2 [m]<hy2>1/2 [m]After

BeforeAfter[%]

LTR Arc#1

0.037

0.018

0.019

0.016

-3.3, -2.4

RTL Arc#1

0.079

0.019

0.00940.0077- 4.5

RTL Arc#2

1.05

0.021

0.02

0.01

- 8.2

BTp Arc#0

0.27

0.02

0.01

0.03

-2612.9

BTp Arc#1

0.037

0.047

0.126

0.102

2.5

Slope

0.011

BTp Arc#2&3

0.123

0.029

0.253

0.313

2.55.1

Slope 2

0.012

0.012

0.324

0.017

3.4

BTp Arc#4

BT-WS placed

Inj. point to MR

Quad
Fudge Factor

Before

0.029

Y. Seimiya,
N. Iida,M. Kikuchi

BT-WS placed

2.5

2.5

Inj. point to MR

33A) Dispersion induce by ST-1A@PY172, PY1820.5A@PY184• Dispersion generated by ST is lessthan 0.05 m.
• The dispersion affect to beam size
less than 1%.

34B) Effective emittance•

Effective emittance, design emittance, emittance growth by beam jitter：✏ef f =•p

< (x +x)2 >< (x0 +x0 ) 2 >< (x +x)(x0 +x0 ) > 2 .

Effective emittance can be described by design emittance and emittance growth
included by beam phase space jitter,0<<latexit sha1_base64="8GwSLqarbG8y/a8mhIjexYKFHEk=">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</latexit>x >✏0 + ✏j•

Bmag ( 1) express amount of mismatching between< x>
beam optics and the jitter optics. (Not between beam
Nominal emittance
optics and the design optics.) If matching is perfect,
Emittance growth by beam jitter
Bmag=1.

•Once beam position and transfer matrix between two BPMs is identified, we can35
derive beam angle.

B) Positron generation target• As jitter source, components around target is suspected.
• Schematic layout of component around target.

T. Kamitani slide

Target hole for electron beam
• Electron beam straightly pass through the positron
36
generation target hole, which diameter is 2 mm.

B) Dummy Target• To reveal beam jitter source directly, we temporally replaced the target todummy target with several hole, which had different diameter.
• In autumn 2018, we studied the target hole effect on beam jitter.
Y. Enomoto et al.

37B) Binarization effectof pulse ST
In binarization

Binarization was stopped

38B) Dispersion effect on position jitter
Measured Dispersion
Position jitter induce bydispersion, assumed that Δδ
from J-ARC orbit jitter (2).
Measured position jitter (1)(1) – (2)• After the target, not small orbit jitter is still exist.
• The remain jitter come from beta function as mentioned inour slide.
39B) Orbit jitter and beta function

40B) RF Phase Jitter and Energy Jitter••••

Using RF monitor, energy jitter from RF phase was derived.
1000 shots, 15 minutes.
Significant correlation can be seen at both J-ARC and LINAC end.
Mainly the dependence come from RF zero cross phase as
mentioned in our slide.
J-ARC

Li. endB) Orbit FB at BT
FB start

FB start42C) Simulation for minimizing emittance growth
induced by wakefield in acceleration structure

Particle tracking simulation was performed to evaluate
this emittance growth.
Simulation conditions:•
Measured misalignments of acc. structure andquadrupole magnet were used.
•
Aris diameter of acc. structure is about 20 mm.

•
•
•
•

γβeinj = 10 µm
sz = 1.3 mm
sd = 0.4%
Q = 5 nC

After orbit displacement is minimized

LINAC end:
γβεx240 μm
γβεy120 μm

LINAC end:
γβεx 22 μm
γβεy 11 μm
γβBlue and red line
shows horizontal
and verticalrequirement ofPhase-III.

γβBlue and red dot
show horizontal
and verticalemittance,
respectively.

Phase-III requirement:
Horizontal  ( 50μm)
Vertical   ( 20 μm)
After emittance is minimized at theend of LINACs (m)End of LINACs (m)By the orbit correction for minimizing emittance growth, requirement of Phase-III can be satisfied.
43

Emittance measurement (e-)
in Phase 2••

Left and right figure show horizontal and vertical emittance measured at each sector, respectively.
Green and blue plot show emittance of beam generated by RF gun.

• Manual orbit correction was done so as to reduce the orbit distortion. By this correction,
emittance was reduced.
• In Phase-II, the requirement of e- emittance at the end of LINAC was satisfied.
• However, emittance was increased in BT though dispersion correction was done.
• This growth is not caused by radiation excitation because BT-WS is placed around the start of BT.

1.2n
C

X

N. IidaY

Phase-IIreduced byorbit
correction

Phase-III
B C

5 BT

Phase-II
Phase-III
B C

5 BT

44

Emittance measurement (e+)
in Phase 2• In Phase-II, the requirement of e+ emittance at the end of LINAC was also satisfied.
• However, e+ emittance was also increased in BT though dispersion correction was done.
• Investigations for this emittance growth source in BT are under going.

0.7nC

X

N. IidaY

Phase-II

Phase-II

Phase-III

Phase-III
B C

5 BT

B C

5 BT

45

ex) Single-bunch effects: Longitudinal: CSR➤ CSR at RTL of SuperKEKB
D. Zhoul Dependence between BCS acceleration voltage (Vrf) and CSR
effect46ex) Single-bunch effects: Longitudinal: CSR➤ Tracking with CSR: (Vrf=21.5 MV, Q=0.7 nC, Nbin=128)
D. Zhou● Np=1e6, GCUT=5
BSE1

BRS.1

BRS.2

BRS.3

BL1S.1

BL1S.2BL2S.1BL2S.2BL2S.347ex) Single-bunch effects: Longitudinal: CSR

D. Zhou

Np=1e6➤ Vrf=0. MV:● W/O CSR, !"x = 91.484 nm● With CSR, !"x = 91.484 nm@4nC➤Vrf=21.5 MV:● W/O CSR, !"x = 91.563 nm● With CSR, !"x = 91.566 nm@4nC➤ Vrf=23. MV:● W/O CSR, !"x = 91.577 nm● With CSR, !"x = 91.583 nm@4nC

48ex) Very Rough Estimation of CSR
N. IidaHandbook of Accelerator Physics and Engineering
3rd Printing

k=1/sz=150~1000 << g3/R=2.9e9

dE=Z(k)L*I/E
dex=(hx*dE)2/bx
Dgex=Sum∑ dex)i=0.81µm < 40µm

Z0=377R=3.35m
sz=1~7mm
L=0.7938m
cc=1nC,
E=1.1GeV
I=cc/sz*c49

N. Iidaex) Very Rough Estimation of
Resistive
Wall
Handbook of Accelerator Physics and EngineeringdE=(Z0/L)*L*I/E
dex=(hx*dE)2/bx
Dgex=Sum∑ dex)i=0.0012µm << 40µm

Z0=377R=3.35m
sz=1~7mm
L=0.7938m
cc=1nC,
E=1.1GeV
I=cc/sz*c
m=050