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Coupler Kick. Igor Zagorodnov and Martin Dohlus DESY, BDM, 2 April, 2007. y. x. upstream coupler. downstream couplers. 115 o. 150 o. 35 o. Resonator für TESLA TEST Facility (asymmetrisch/mit DESY-HOM-Koopler) 0 93 2214/0.000. Notation and Definitions. - PowerPoint PPT Presentation
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Coupler Kick
Igor Zagorodnov and Martin Dohlus
DESY, BDM,
2 April, 2007
x
y
x
y
x
y
downstream couplersupstream coupler
Resonator für TESLA TEST Facility(asymmetrisch/mit DESY-HOM-Koopler)0 93 2214/0.000
150o35o
115o
( ) Gaussian bunch with rms widths
( ) ( ) kick factork W W s s ds
Notation and Definitions
0.520.5rms 2( ) ( ) ( ) rms kick factork W k W s k s ds
It gives an estimation for the head-tail difference in the kick (banana shape)
The picture from R. Wanzenberg,Review of beam dynamics …,Linac Conference, 1996
-2 0 2-3
-2
-1
0
1
2
3
0.0069 3.2 1.1 [m] kV( , )
0.0094 1.1 1.0 [m] nC
xx y
y
k
x
y
x
y
x
y
x
y
0.0142 1.02 1.15 [m] kV( , )
0.0095 1.15 0.07 [m] nC
xx y
y
k
-2 0 2-3
-2
-1
0
1
2
3( , )x yk
[mm]x
[mm]y
downstream couplers upstream coupler
Wake kick near to the axis
( , )x yk
[mm]x
[mm]y
x
y
x
y
0.021 4.3 0.07 [m] kV( , )
0.019 0.03 0.9 [m] nC
xx y
y
k
x
y
x
y
5.3mm
21.3
cr
min
kV5 5
nCe k
+Wake kick near to the axis
[mm]x
[mm]y k
x
y
x
y
x
y
x
y
2
2
x
y
x
y
x
y
x
y
old
new
How to compensate the wake kick on the axis?
We have rotated by 90 degree, but 92.5 is possible better.
0.021 4.3 0.07 [m] kV( , )
0.019 0.03 0.9 [m] nC
xx y
y
k
5.3mm
21.3
cr
min
kV5 5
nCe k
x
y
x
y
x
y
x
y
+ x
y
x
y
x
y
x
y
0.0025 2.33 0.04 [m] kV( , )
0.0002 0.02 1.1 [m] nC
xx y
y
k
1.1mm
0.2
cr
min
kV8 5
nCe k
Wake kick for the new orientation
[mm]x
[mm]yk
[mm]x
[mm]yk
x
y
x
y
x
y
x
y
+ x
y
x
y
x
y
x
y
-0.5 0 0.5-0.04
-0.03
-0.02
-0.01
0
0.01
-0.5 0 0.5-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
kV(0,0)
nCxW
kV(0,0)
nCyW
old
new
old
new
[cm]s [cm]s
Wake kick for the new orientation
RF kickdownstream coupler,new, zpen/mm=6, forwardx/mm =… y/mm=…
x
y
x
y
RF kick
upstream couplerx/mm =… y/mm=…
x
y
x
y
TESLA Cavity in Cryomodule
Zagorodnov I., Weiland T., The Short-Range Transverse Wakefields in TESLA Accelerating Structure// Proceedings of PAC 2003 Conference, USA, 2003.
2400 μm
120 μm
25 μm
European XFEL Project
http://www.desy.de/xfel-beam/index.html
2400 μm
5*8=40 couplers
Injector
Coupler RF kick is the most important. It can be reduced by alternative direction orientation of couplers.
0 1 2 3 4 50
20
40
60
80
100
120
V
nC*cavityrmsk
[mm]r
coupler wake
coupler RF kick
cavity wake
120 μm
12*8=96 couplers
Bunch Compressor
Coupler wake is the most important. It can be reduced with the new orientation of HOM couplers.
0 1 2 3 4 50
5
10
15
20
25
30
V
nC*cavityrmsk
[mm]r
coupler wake
coupler RF kick
cavity wake
100*8=800 couplers
25 μm
Main Linac
Coupler wake is the most important. It can be reduced with the new orientation of HOM couplers.
0 1 2 3 4 50
5
10
15
20
25
30
V
nC*cavityrmsk
[mm]r
coupler wake
coupler RF kick
cavity wake
2400 μm 120 μm 25 μm
Injector Bunch Compressor Main Linac
Effect of new HOM couplers orientation
Coupler wake kick is the most important. It can be reduced with the new orientation of HOM couplers.
Coupler RF kick is the most important. It can be reduced by alternative direction orientation of couplers.
0 1 2 3 4 50
20
40
60
80
100
120
V
nC*cavityrmsk
[mm]r
coupler wake
coupler RF kick
cavity wake
0 1 2 3 4 50
5
10
15
20
25
30
V
nC*cavityrmsk
[mm]r
coupler wake
coupler RF kick
cavity wake
0 1 2 3 4 50
5
10
15
20
25
30
V
nC*cavityrmsk
[mm]r
coupler wake
RMS bunch length,
m
Coupler wake Coupler RF field Cavity wake
2400
Design= 2.5
New= 1.3
2.7 21.6
120 0.14 3.5
25 0.03 0.77
0, 1,rms rms rmsk k k r
1,
* *rms V
knC mm cavity
RMS bunch length,m
Coupler wake Coupler RF field Cavity tilt by
1 mrad
(on crest / 10 grad)
Cavity wake
2400
Design= 16.4
New=1.4
58 23 / 88
0120 2.9 0.06 / 4
25 0.6 0.002 / 0.9
0,
*rms V
knC cavity
Head-Tail Kick (rms kick)
Head-Tail Kick (rms kick)
1. Transverse Coupler Wake is capacitive (integral from bunch shape)
0 1 k k k r 0, 01
3rmsk k 1, 11
3rmsk k
2. RF Coupler Kick (on crest)
( ) Re( )iksx zV s Vx V e 15MVzV
1.3GHz2k
c
0, Im( )rmsk Vx k
3. Cavity tilt by angle
0( )( ) Re(0.5 )i kszV s V e
1/ 220, Re ( ) Re ( ) ( )rmsk V s V s s ds
Conclusion
Coupler RF kick is a main effect in the injector. It can be compensated by an alternative direction orientation of couplers.
Coupler wake kick is a main effect after the 1st bunch compressor. Rotation of the HOM couplers by 90 degree allows to reduce the kick by factor 12.
0 1 2 3 4 50
20
40
60
80
100
120
V
nC*cavityrmsk
[mm]r
coupler wake
coupler RF kick
cavity wake
0 1 2 3 4 50
5
10
15
20
25
30
V
nC*cavityrmsk
[mm]r
coupler wake
coupler RF kick
cavity wake
0 1 2 3 4 50
5
10
15
20
25
30
V
nC*cavityrmsk
[mm]r
coupler wake
