a special large aperture bpm at flash nicoleta baboi for kirsten hacker bpm workshop, lüneburg,...
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A special large aperture BPM at FLASH
Nicoleta Baboi
for Kirsten Hacker
BPM Workshop, Lüneburg, Nov. 30, 2006BPM Workshop, Lüneburg, Nov. 30, 2006
FLASH
• 0.5-1nC / bunch
• 1 MHz … 100 kHz, up to 800 s
• up to 700 GeV (later 1 GeV)RF gun
FEL experimental
area
bypass
4 MeV 150 MeV 450 MeV 1000 MeV
undulatorscollimator
bunch compressorLaser
bunch compressor
accelerator modules
250 m
Magnetic chicanes
bunch compression
x = R16*E/E
Energy stability
• Energy jitter position jitter in dispersive sections (e.g. magnetic
chicanes) arrival-time jitter after chicane
• Requirement– timing jitter < 30 fs energy jitter < 10-4 (35 m
position jitter in BC)
• Use BPM to measure position jitter– resolution: 5 m (single bunch)– challenge: large horizontal aperture in BC2
unconventional design needed
BPM for the Bunch Compressor
beam
stripline vacuumstripline vacuumStripline Vacuum
Beam
beam
tapering
SMA outputRF
pulses
beam
tapering
SMA output
Beam
Tapering
SMA output RF
Pulses
cannot reach 5 m res. with analogue electronics use optical method
BPM installed in BC2
Compact!
Thanks to:
Jan HauschildtDirk NoelleSilke VilcinsHolger SchlarbNils MildnerChristopher GerthAnd many more…
T1-T2=T3
D=T3*c
dE/E=D/R16T1
T2
T3
EBPM
~300mm
0 0.5 1 1.5 2
-30
-20
-10
0
10
20
30
simulation and oscilliscope readout
time (ns)
Vo
lts
scopesimu
0 0.2 0.4 0.6 0.8 1
-200
-100
0
100
200
simulation and oscilliscope readout
time (ns)
Vo
lts
40 GHz
8 GHz
beam
stripline pickup
resolution < 3um
-15 -10 -5 0 5 10 15-6
-4
-2
0
2
4
6Beam position ( = 18.0 deg)
delta [%]
po
sitio
n (
cm)
R16T166R3666
-0.4 -0.2 0 0.2 0.4 0.6 0.8-40
-30
-20
-10
0
10
20
30
40
time (ns)
Vo
lts
chicane BPM scope traces for 12-16 MV/m gradient
~ 150 um resolution => 5*10-4 resolution
Scope in tunnel
-20 -15 -10 -5 0
0.9
1
1.1
1.2
1.3
1.4
1.5BPM slope
phase (deg)
slo
pe
at z
ero
cro
ssin
g (
V/p
s)
-25 -20 -15 -10 -5 00
0.5
1
1.5
2
2.5
3Beam position ( = 18.0 deg)
phase (deg)
po
sitio
n (
cm)
Scope in tunnel
Dphase = (-Etot+Egun+Eacc1*cos(pi*phase/180)) Etot
12 13 14 15 1655
60
65
70
75
80BPM amplitude
gradient (MV/m)
am
plit
ud
e (
V)
12 13 14 15 160.9
1
1.1
1.2
1.3
1.4
1.5
1.6BPM slope
gradient (MV/m)
slo
pe
at z
ero
cro
ssin
g (
V/p
s)
-15 -10 -5 0 5 10 15-6
-4
-2
0
2
4
6Beam position ( = 18.0 deg)
delta [%]
po
sitio
n (
cm)
R16T166R3666
-0.4 -0.2 0 0.2 0.4 0.6 0.8-40
-30
-20
-10
0
10
20
30
40
time (ns)
Vo
lts
chicane BPM scope traces for 12-16 MV/m gradient
~ 150 um resolution => 5*10-4 resolution
Scope in tunnel