TLS and TPS Vertical Beam Size Control and Beam Stability Issues

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Nov 25, 2013 (3 years and 7 months ago)

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NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
1

TLS and TPS Vertical Beam Size
Control and Beam Stability Issues

C.C. Kuo


NSRRC XBPM and Beam Stability Mini Workshop

September 11
-
12, 2008

NSRRC

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
2

Outline

1.
Challenges of a high
-
performance
light source

2.
Sources of the beam perturbations

3.
Emittance coupling control

4.
Orbit stability and beam instabilities
control


NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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3

Challenges of a high
-
performance LS


High brilliance, low emittance,
low emittance coupling ratio, high
nonlinear lattice effects


Small beam size, stringent stable
beam orbit


High current, low beam
impedance, good vacuum


Many insertion devices with small
sizes of vacuum pipes


High reliability, reproducibility
and flexibility


Reasonable beam current lifetime
and top
-
up injection


NSRRC
TLS

TPS

eff
y
eff
x
p
y
p
y
p
x
p
x
photon
I
dt
dN
B
,
,
,
,
,
,
2
'
'
4
/












[photon/sec/mm
2
/mrad
2
/0.1%bandwidth]

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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TLS and TPS Optical functions


OPTICAL FUNCTIONS TPS 79H2
0
10
20
30
40
50
60
70
80
0
5
10
15
20
25
30
S(m)
Optical Functions (m)

x

y

x
*10
emittance = 1.6 nm-rad
TLS: 25.6 nm
-
rad @1.5 GeV

TPS: 1.6 nm
-
rad @ 3GeV

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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5

TLS and TPS Parameters

TLS

TPS

Energy (GeV)

1.5

3.0

Beam current (mA)

300

400

Circumference (m)

120

518.4

Nat. emittance

x
(nm
-
rad)

25.6

1.6

Cell / symmetry / structure

6 / 6 / TBA

24 / 6 / DBA

Straights

6m*6

12m*6+7m*18

Betatron tune
n
x
/
n
y

7.18 / 4.13

26.2 / 13.25

Mom. comp. (
a
1
,
a
2
)

6.678
×
10
-
3
,
-
3.89
×
10
-
3

2.4
×
10
-
4
, 2.1
×
10
-
3

Nat. energy spread

E

7.45
×
10
-
4

8.86
×
10
-
4

Damping time (ms) (
t
x

/
t
y

/
t

s
)

7.2 / 9.3 / 5.5

12.20 /12.17 / 6.08

Nat. chromaticity
x
x

/
x
y

-
15.3 /
-

7.9

-
75 /
-
27

RF frequency (MHz)

500

500

RF voltage (MV)

1.6

3.5

Harmonic number

200

864

SR loss/turn, dipole (keV)

128

852.6

Synchrotron tune
n
s

1.52
×
10
-
2

6.09
×
10
-
3

Bunch length (mm)

6.5

2.86

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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Electron beam size


Emittance ratio=1% due to betatron coupling

Source point

σ
x

(μm)

σ
x


(μrad)

σ
y

(μm)

σ
y


(μrad)

TPS

1.6 nm
-
rad

12 m straight
center

165.1

12.4

9.8

1.6

7 m straight
center

120.8

17.2

5.1

3.1

Dipole

39.7

76.1

15.8

1.1

TLS

25.6 nm
-
rad

6 m straight
center

526.9

50.3

27.7

9.5

Dipole

125.1

287.8

55.8

8.5

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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Sources of the beam perturbations


Emittance coupling change


Collective instabilities


single
-
bunch and
coupled
-
bunch, longitudinal and
transverse


Beam
-
ion instabilities


Orbit perturbations



NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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8

Emittance Coupling Sources


Linear betatron coupling due to skew quadrupole
errors from
(1)

quadrupole rotation errors and
(2)

vertical closed orbit distortion in sextupoles.


Linear betatron coupling from solenoid field.


Spurious vertical dispersion caused by


(A)

(1)

vertical bend error from bending rotation

errors and
(2)

vertical closed orbit errors in the

quadrupoles


(B)

dispersion coupling due to skew quadrupole

errors in the dispersive region which are from

(3)

quadrupole rotation errors in the dispersive

region and
(4)

vertical closed orbit distortion in

sextupoles in the dispersive region.


NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
9

)
cos(
,
1
,
1




n
n







l
J
J
G
J
J
H
y
x
y
x
l
y
x

or

2

where
,
2
1
2
1
]
)
(
[
,
1
,
1
co
s
s
l
i
s
y
x
i
l
y
k
k
k
k
ds
e
k
e
G
y
x
y
x

















n
n



B
the minimum separation of the normal mode tunes is

|
|
,
1
,
1
l
G






y
x
n
n
.


Coupling ratio is defined as:

2
2
2
2



G
G

.



















i
i
y
i
x
set
co
i
i
y
i
x
quad
l
k
y
l
k
G
,
,
2
2
,
,
,
,
2
1
2
2
2
2
1






Betatron Coupling driving strength


Betatron Coupling

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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10

Betatron coupling

3
,
,
2

10
9.0
10
1.5
:
TLS
13
,
,
2

10
61
.
3
10
79
.
7
:
TPS
2
2
2
2
,
5
-
2
4
-
2
2
2
2
2
,
3
-
2
4
-
2
































y
x
sex
co
quad
y
x
sex
co
quad
G
G
y
G
G
G
y
G
n
n


n
n


Two major sources:

(1)
Quad rotation

(2)
Vertical orbit through sextupoles

TPS

TLS

Qaud roll=0.1 mrad rms

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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Spurious Vertical Dispersion

m
C
c
c
I
c
q
dipole
y
y
q
dipole
y
y
y
y
y
y
q
y
q
y
13
2
2
2
'
2
2
2
10
832
.
3
,
/
2

/
]
)
(
[

:
dispersion

vertical
to
due

emittance

Vertical















a




























i
i
i
yi
y
i
co
i
i
xi
i
yi
i
i
i
xi
i
yi
i
co
i
i
i
yi
i
i
i
yi
y
dipole
y
L
F
y
L
k
L
k
y
L
k
L
2
2
2
2
,
2
2
2
2
2
2
1
2
,
2
1
2
2
2
2
2
sin
8
1


,



sin
8
1
/

n









n

























sext
i
co
xi
i
quad
i
xi
i
quad
i
co
i
dipoles
i
i
y
k
k
y
k
F
,
,
2
,
1
,
,
1
2
,





Vertical dispersion generated from all error sources can be expressed as:

2
,
-1
2
-3
2
,
-1
2
-3
y
10
7
.
1
10
6
.
7
10
78
.
4

10

18
.
5
)
(
sext
co
quad
quad
co
dipole
y
y
rad
nm
















TPS:

2
,
-1
2
-2
2
,
-1
2
-2
y
10
3
.
2
10
1
.
1
10
3
.
1

10

2
.
1
)
(
sext
co
quad
quad
co
dipole
y
y
rad
nm
















TLS:

Unit: mm, mrad

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
12

Spurious Vertical Dispersion

2
,
-1
2
-3
2
,
-1
2
-3
y
10
7
.
1
10
6
.
7
10
78
.
4

10

18
.
5
)
(
sext
co
quad
quad
co
dipole
y
y
rad
nm
















TPS:

2
,
-1
2
-2
2
,
-1
2
-2
y
10
3
.
2
10
1
.
1
10
3
.
1

10

2
.
1
)
(
sext
co
quad
quad
co
dipole
y
y
rad
nm
















TLS:

Unit: mm, mrad

TPS

TLS

Dipole roll=0.2 mrad rms

Quad roll=0.1 mrad rms

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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Cross Orbit Response Matrix


Vertical orbit and dispersion response

y
m
c
c
G
y
x
K
x
K
s
G



2
~
1
)
(
,

x
c
x
c
y
y
K
K
y
K
G
s
F


2
~
1
1
)
(





NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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Response Matrix


skew quads and sextupoles only










k
Hj
H
kj
V
ik
k
s
Hj
H
sj
V
is
s
m
i
c
R
R
l
K
R
R
ly
K
y
,
)
(
)
(
)
(
)
(
)
(
1
~
)
(
)
(
2


,
)
(
)
(
)
(
)
(
~
1
)
(
2
x
V
ik
k
k
x
V
is
s
m
s
i
y
R
l
K
R
ly
K








V
MK


TPS:

M: 16296 X 24 or 48

K: 24 or 48 skew quads

V: 16296 (96*168+168)

168 Monitors, 4 correctors per section,
96 in total. Using SVD method to get K
as wanted correction.

TLS:

M: 1176 X 8

K: 8 skew quads

V: 1176 (24*48+48)

48 Monitors, 4 correctors per section, 24 in
total. Using SVD method to get K as wanted
correction.

M : unified response matrix for a set of horizontal steering and


installed (or virtual) skew quads

V : measured normalized vertical orbit and dispersion,

K : skew quad array in the ring can be obtained using

SVD

for a linear equation
such that the betatron coupling and vertical dispersion can be minimized
simultaneously
.


NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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15

Experimental results (TLS)

correction
after


0016
.
0
|
|
correction

before

0119
.
0
|
|
3
,
1
,
1
3
,
1
,
1




G
G
Coupling ratio is defined as:

2
2
2
2



G
G

C.C. Kuo, et. al EPAC2002

No de
-
convolution yet

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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17

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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18

C.C. Kuo, et. al EPAC2002

TLS results

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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Vertical beam size from interferometer at NSRRC

um


Top
-
up

FBs ON

2008/8/29

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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Sensitivity to alignment in TPS

Error Type
(rms) (<

bend
>



m


Quantity

F(Driving Term)

<

2

>
[m]

<

y
>
[m
m
]


y
[m
-
rad]


y
/

x

Dipole Rotation: 0.2

mrad





2.38E
-
05

6.57E
-
08

1.02E+00

2.07E
-
13

0.01%

Quadrupole Rotation:

0.1mrad






x



1.97E
-
05

2.41E
-
08

6.20E
-
01

7.60E
-
14

0.00%

Vertical Quadrupole Position:

0.1mm


y




y

1.41E
-
04

1.52E
-
06

4.92E+00

4.78E
-
12

0.30%

Vertical Sextupole Position:

0.1mm


y




x

y

2.33E
-
04

5.41E
-
07

2.94E+00

1.70E
-
12

0.11%

Total:

0.43%




Error Type (rms)



G



(%)

Quadrupole Rotation: 0.1 mrad

5.04E
-
02

1.40E
-
03

1.53E
-
01

Vertical Sextupole Position: 0.1 mm

5.04E
-
02

3.00E
-
03

7.07E
-
01

Spurious dispersion

Betatron coupling

Increase tune separation to 0.1 will reduce K by a factor about 4



NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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21

CORRECTION OF VERTICAL DISPERSION AND BETATRON
COUPLING

Lattice: TPS 79H2


Using cross
-
plane
response matrix and SVD
method to correct both
betatron coupling and
vertical dispersion with a
set of skew quadrupoles.



With 48 skew quads, <1%
emittance ratio can be
achieved, and the
maximum strength is <
5.4x10
-
3

m
-
1

100 machines

Before correction

100 machines

After correction

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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Efforts for Beam Stabilization in TLS

1. Orbit stability:


Elimination of sources


Feedback system


2.Coupled
-
bunch instability:


RF gap voltage modulation ( ~ Oct. 2004)


Superconducting RF ( Dec. 2004 ~)


Coupled
-
bunch feedback systems (FPGA
-
based
processor)



Transverse (Nov. 2005), 300 mA top
-
up



Longitudinal (Feb. 2006)

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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TLS orbit

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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Orbit at NSRRC:

COD - y
-10
-8
-6
-4
-2
0
2
4
6
8
10
0
20
40
60
80
100
120
s(m)
cod-y (mm)
cod before correction
cod after correction
cod mad simulation before correction
COD - X
-8
-6
-4
-2
0
2
4
6
8
10
0
20
40
60
80
100
120
s(m)
cod-x (mm)
cod-x before correction
cod-x after correction
cod mad simulation before correction
)
(
)
(
)
3
.
9
(
)
(
)
6
.
22
(
)
(
)
10
(
)
(
)
5
.
3
(
)
(
)
3
.
32
(
)
(
2
,
2
2
,
2
2
,
3
2
2
2
,
2
2
,
mrad
mm
z
mm
z
B
B
mm
x
mm
x
rms
BM
s
rms
q
rms
co
rms
rms
q
rms
co












COD before correction (compared with model simulation with errors input) in SRRC

Storage ring at commissioning stage in1993. Corrected COD is shown.

Qx=7.18, Qy=4.13

47 BPM, 24HC, 30 VC

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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25

32 micron, rms (H) and 40 micron, rms (V) after correction

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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Some examples related to orbit perturbations at NSRRC

22
23
24
25
26
27
28
29
30
0
2000
4000
6000
8000
10000
Temperature (degree C)
Time (sec)
inlet temperature
outlet temperature
chamber temperature
-10
-5
0
5
10
15
20
25
30
0
2000
4000
6000
8000
10000
Horizontal orbit (um)
Time (sec)
0.1
0.1 05
0.1 1
0.1 15
0.1 2
0.1 25
0
1 00
2 00
3 00
4 00
5 00
6 00
7 00
Vertical orbit at r3bpm5Y (mm)
Tim e(se c ) 1 0 mi n utes aro un d the ri n g
c ra ne mo ve me nt effec t o n th e orb it
Cooling water temp. variation

While adjusting PID controller

Orbit oscillations

due to cooling water temp.

Vertical orbit changes during crane motion


Orbit drift during ID gap change

w/ and w/o feedback

One turn

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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27

Y Orbit Distortion (inbound)

U5 Gap (mm)

0

50

100

150

200

250

dYrms (micron)

0

1

2

3



Yrms at 138mA 98/10/02



Yrms at 157mA 98/10/02



Yrms at 108mA 98/10/08



Yrms at 124mA 98/10/14



Yrms at 138mA 98/10/28

Orbit feed
-
forward for ID gap change:

H. Chang, SRRC

X Orbit Distortion (inbound)

U5 Gap (mm)

0

50

100

150

200

250

dXrms (micron)

0

1

2

3

4

5



Xrms at 138mA 98/10/02



Xrms at 157mA 98/10/02



Xrms at 108mA 98/10/08



Xrms at 124mA 98/10/14

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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28

Girder Displacement


Main cause: air temperature


Sensitivity to air temp.: ~10
μ
m

/



Induced beam orbit drift: 20
-
100
μ
m

/



Current status: <
±

0.1
μ
m per 8 hr shift



Air temp. :
<
±

0.1


(utility control system improved)



T
hermal insulator jacket

-200
0
200
400
600
800
1000
1200
1400
0.92
0.94
0.96
0.98
1.00
-200
0
200
400
600
800
1000
1200
1400
24.0
24.5
25.0
25.5
26.0
Beam Position
mm
min
Air Temperature
Degree (C)
0
25
50
75
100
24
25
26
27
28
Displacement (£gm)


Tunnel Air Temp.

Girder Disp. Outer

Girder Disp. Inner
Time (Hours)
Temperature (¢J)
-20
-15
-10
-5
0
J.R. Chen et. al.

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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29

Magnet (Water Temp.)

100
200
300
400
22
24
26
28


Mag-Water Temp.

Beam Position
Time(min.)
Temperature (¢J)
0.22
0.23
0.24
0.25
0.26
Position (mm)
Caused by the temperature fluctuations of magnet cooling water


Magnet deformed ~10
μ
m/




䥮摵捥搠扥慭b潲扩琠摲楦琺 5
-
㔰5
μ
m /


䍵牲敮琠獴s瑵s


Cooling water temp.: ~
±

0.1


J.R. Chen et. al.

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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30

Expansion of Vacuum Chamber


Caused by synchrotron light irradiation.



Sensitivity to water temp.: ~10
μ
m

/



Move the girder (~0.3
μ
m
/

) and BPM (~1
μ
m
/

)


Induced beam orbit drift: ~10
-
30
μ
m

/



Current status


Vacuum cooling water temp.: ~
±

0.5


0
6
12
18
24
19.5
20.0
20.5
21.0
21.5

Girder Displacement

Beam Current
Time (Hours)
Displacement (£gm)
0
100
200
Beam Current (mA)
0
200
400
600
800
1000
1200
1400
-0.08
-0.06
-0.04
-0.02
0
200
400
600
800
1000
1200
1400
0.5
1.0
1.5
2.0
0
200
400
600
800
1000
1200
1400
24
25
26
27
28
0
200
400
600
800
1000
1200
1400
0
100
200
Beam Position
mm
min
BPM Displacement
um
Vac-chamber Temp
Temp (C)
Beam Current
mA
J.R. Chen et al.

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
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31

TLS beam response to ground
wave and mechanical vibration

0
10
20
30
40
50
60
70
80
90
10
-10
10
-5
10
0
10
5
Frequency[Hz]
P
x
(f) [

m
2
/Hz]
Horizontal Ground Vibration at NSRRC Site.
Measured on Ground
Measured on Magnet
e-Beam(R
m
a
x
* Measured on Magnet)
0
10
20
30
40
50
60
70
80
90
10
-4
10
-2
10
0
10
2
Frequency[Hz]
I
x
(f) [um]
Measured on Ground
Measured on Magnet
e-Beam(R
m
a
x
* Measured on Magnet)
0
10
20
30
40
50
60
70
80
90
10
-10
10
-5
10
0
10
5
Frequency[Hz]
P
y
(f) [

m
2
/Hz]
Vertical Ground Vibration at NSRRC Site.
0
10
20
30
40
50
60
70
80
90
10
-4
10
-3
10
-2
10
-1
10
0
10
1
Frequency[Hz]
I
y
(f) [um]
Measured on Ground
Measured on Magnet
e-Beam(R
m
a
x
* Measured on Magnet)
Measured on Ground
Measured on Magnet
e-Beam(R
m
a
x
* Measured on Magnet)
V=500 m/s

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
32


Closed

Orbit

:

tens

micron

rms

w
.
r
.
t
.

target

orbit

with

DC

correction

schemes
.




Orbit

distortions
:

<

10

micron

rms

during

insertion

gap

scan

can

be

compensated

for

using

look
-
up

correction

tables
.




Beam

orbit

stability
:

a

few

micrometer

level

(peak
-
to
-
peak)

with

a

global

feedback

system
.

(temperature

control,

electricity

upgrade,

etc
.
)


Closed Orbit and Orbit Stability

(low frequency)

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
33

TLS orbit log (0.1Hz sampling)

2008/08/29

mm

mm

K.T. Hsu will talk about high frequency behavior

mm

mm

mm

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
34

TLS instabilities and cures

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
35

R
e
f
-
2
0

d
B
m
A
t
t

1
0

d
B
*
*

A

S
G
L
R
B
W

3

k
H
z
V
B
W

3
0

k
H
z
S
W
T

1
1
.
5

s
C
e
n
t
e
r
4
9
9
.
6
5
4

M
H
z
S
p
a
n
1
0
0

M
H
z
1
0

M
H
z
/
1

A
P
C
L
R
W
R
-
1
2
0
-
1
1
0
-
1
0
0
-
9
0
-
8
0
-
7
0
-
6
0
-
5
0
-
4
0
-
3
0
-
2
0
A22
Date: 12.APR.2005 02:19:56
R
e
f
-
2
0

d
B
m
A
t
t

1
0

d
B
*
*

A

S
G
L
R
B
W

3

k
H
z
V
B
W

3
0

k
H
z
S
W
T

1
1
.
5

s
C
e
n
t
e
r
4
9
9
.
6
5
4

M
H
z
S
p
a
n
1
0
0

M
H
z
1
0

M
H
z
/
1

A
P
C
L
R
W
R
-
1
2
0
-
1
1
0
-
1
0
0
-
9
0
-
8
0
-
7
0
-
6
0
-
5
0
-
4
0
-
3
0
-
2
0
A22
Date: 12.APR.2005 02:19:06
TFB OFF
TFB ON
TLS
-

Transverse Performance

Beam Spectrum

Courtesy by K.T. Hsu

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
36

TLS
-

Transverse Performance

Transverse Feedback OFF

Transverse Feedback ON

Synchrotron Radiation Monitor

Courtesy by K.T. Hsu

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
37

Loop Closed

Loop Open

Snapshot of Synchrotron
Radiation Beam Profile

(w/o Longitudinal Feedback)

Grow/Damp test results @ 300 mA

0
5
10
50
100
150
200
0
10
20
30
40
50
60
Time (ms)
a) Osc. Envelopes in Time Domain
Bunch No.
Arb. Unit
0
5
10
0
50
100
150
0
2
4
6
8
Time (ms)
b) Evolution of Modes
Mode No.
Arb. Unit
0
5
10
50
100
150
200
0
5
10
15
Time (ms)
a) Osc. Envelopes in Time Domain
Bunch No.
mm
0
5
10
0
50
100
150
0
1
2
3
4
Time (ms)
b) Evolution of Modes
Mode No.
mm
0
50
100
150
200
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Mode Number
Relative Magnitude
Horizontal Plane
0
50
100
150
200
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Mode Number
Relative Magnitude
Vertical Plane
Horizontal

Vertical

Vertical

Horizontal

Modal

Spectrum

Courtesy by K.T. Hsu

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
38

TLS
-

Longitudinal Performance

Courtesy by P.J. Chou and M.H. Wang

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
39

TLS
-

Longitudinal Performance

Evolution of the stable longitudinal mode during user shift

No longitudinal feedback

SRF 5 ~ 10 increase in threshold current

Courtesy by K.T. Hsu

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
40

Conventional RF cavity + RF gap voltage modulator => Longitudinal stable beam

Superconductor RF cavity => Longitudinal stable beam no feedback

Time dependence of beam profile (SR monitor @




0)

TLS
-

Longitudinal Performance

Time dependence of beam profile (SR monitor @




0)

Courtesy by K.T. Hsu

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
41

Streak Camera Observation

Loop Open

Loop Closed

One Turn

One Turn

Loop Closed
-
> Open
-
> Closed

One Turn

Loop Open

Loop Open

Snapshot of the
Synchrotron Radiation
Beam Profile

Loop Closed

Loop Open

Courtesy by K.T. Hsu

TLS performance with
longitudinal feedback

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
42

Photon Beam stability through 50 um pinhole

2008/08/29


Top
-
up 300 mA,

Orbit feedback ON

Transverse and longitudinal feedbacks ON

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
43

TLS operation

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
44

TLS photon beam stability

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
45

TLS orbit reproducibility from
pinhole monitor

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
46

TPS orbit

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
47

TPS COD Correction Scheme

Precision ~ 15

m

7 BPM each cell

3 HC(+1) and 4 VC(+1) each cell for SVD

but all sextupoles are with HC and VC.

CV

CH

CV

CH

CV


CH

CV

SQ

SQ

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
48

COD Error Sources and Amplification Factor

Error Source (rms) 3 sigma truncated

Girder displacement x, y (mm)

0.1

Girder roll
θ

(mrad)

0.1

Quad and sext displacement x,y
w.r.t. girder (mm)

0.03

Dipole displacement x,y (mm)

0.5

Dipole roll
θ

(mrad)

0.1

Dipole field error (10
-
3
)

1

BPMs displacement x, y (mm)

0.1

Amplification factor

Ax

rms (max)


Ay


rms (max)

Quad displacement

55 (97)

40 (51)

Girder displacement

30 (54)

8 (10)

Dipole roll
θ

-

5.8 (7.8)

Dipole field error

1.1 (1.9)

-

COD due to Errors:

Horizontal: 3.8 mm r.m.s.

Vertical : 2.2 mm r.m.s.

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
49

COD Correction



Before Correction COD and
Optics correction

After Correction

XC=2,4,6/YC=1,3,5,7



Horizontal

Vertical

Horizontal

Vertical

COD at BPMs mm (r.m.s.)

3.79

2.22

0.0807

0.0676

Max. COD mm

21.11

9.27

0.371

0.338

Max. Cors Strength mrad





0.402

0.245

Mean Cors Strength mrad





0.0788

0.0484

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
50

Correction Capability and Residual COD



Correctors

Used

Number of

eigenvalues

used

Mean of

<|cor. Str.|>

(mrad)

Max of

|cor. Str.|

(mrad)

Max
|COD|
at
BPM
(mm)

rms COD at
BPM


(mm)

(2,4,6)

72

7.88E
-
02

4.02E
-
01

3.71E
-
01

8.07E
-
02

(1,4,6)

72

7.34E
-
02

3.97E
-
01

3.46E
-
01

8.35
E
-
02

(2,4,7)

72

7.35E
-
02

4.34E
-
01

3.66E
-
01

8.32E
-
02

(1,4,7)

72

6.69E
-
02

3.41E
-
01

3.67E
-
01

8.55E
-
02

72

3.20E
-
02

1.70E
-
01

3.53E
-
01

8.17E
-
02

96

5.44E
-
02

4.35E
-
01

2.92E
-
01

6.87E
-
02

144

1.22E
-
01

7.93E
-
01

2.12E
-
01

4.06E
-
02


Horizontal

168,
(C1
-
C7)x24

168

1.63
E
-
01

9.73E
-
01

4.92E
-
02

7.71E
-
03

(1,3,5,7)

96

4.84E
-
02

2.45E
-
01

3.38E
-
01

6.76E
-
02

(2,3,5,7)

96

5.64E
-
02

3.51E
-
01

3.36E
-
01

7.18E
-
02

48

1.35E
-
02

8.73E
-
02

3.95E
-
01

9.23E
-
02

72

1.98E
-
02

1.43E
-
01

3.42E
-
01

7.97E
-
02

96

3.08E
-
02

1.92E
-
01

3.10E
-
01

6.82E
-
02

144

7.21E
-
02

4.43E
-
01

2.99E
-
01

4.13E
-
02

Vertical

168,
(C1
-
C7)x24

168

1.10E
-
01

8.95E
-
01

7.52E
-
02

1.43E
-
02


NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
51

Ground vibration effects


To

guarantee

the

photon

brilliance,

beam

orbit

disturbance

due

to

ground

wave

need

to

be

controlled
.

V

H

Amplification v=500 m/sec, girder transmission = 1

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
52

TPS Collective Effects


SC RF cavities will not cause coupled bunch instability in
nominal operation.


Resistive wall impedance will cause transverse coupled bunch
instability. To stabilize the beam requires positive
chromaticity( > 5), not recommended.


At present the microwave instability is the dominant limitation
of single bunch current.


The more insertion devices we install, the more detrimental the
transverse instabilities are.


Active transverse feedback system is required for stable
operation.


We must strive to keep good vacuum condition in the storage
ring.

P.Chou

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
53

Major sources of broadband impedance and
microwave instability threshold

Total broadband impedance: |Z/n|= 0.36
W

A. Rusanov

(K. Oide’s code)

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
54

summary


The beam size control including coupling correction,
instability cures or feedback system in TLS and TPS are
discussed. Some orbit perturbation issues included in
this talk. Orbit feedback issues will be covered by
Kuotung Hsu.


With a set of skew quadrupoles in the ring, one can
control both betatron coupling and vertical dispersion.


ID gaps and phases will change coupling strength and
orbit.


Both TLS and TPS need transverse feedback systems to
stabilize the beam in the transverse planes.


In TLS, we need longitudinal feedback system for high
current operation (>200 mA) even we replaced the room
-
temperature cavity with superconduting type.


With SRF in TPS, we might not need longitudinal
feedback system if the vacuum components are well
taken care of.

NSRRC XBPM and Beam Stability Mini Workshop

2008/09/11~12 cckuo
-
55

Thank you