SLAC
SD0/QD0 Cryomodule Jitter
Tolerance
Glen White
SLAC
March 27th 2007
Overview



Asses jitter tolerance on final cryomodule
containing QD0/SD0.
Calculate lumi-loss based on IP beam-beam
offset and beam-growth through off-center
passage through SD0.
Use Lucretia + GUINEA-PIG to measure
LUMI loss criteria for QD0/SD0 offset with
IP fast-feedback compensating.
IP Fast-Feedback
Use ILC IP FFB, tuned for ‘noisy’ conditions

Less than 5% lumi-loss with GM ‘K’ + 25nm component vibration (pulsepulse) & ~ 0.1 sigma intra-bunch uncorrelated beam jitter.

Assume BDS-entrance FFB has perfectly flattened beam train (flat
trajectory into Final Doublet).
No ‘banana’ effect on bunches.
Calculate Luminosity from measured bunches, with mean of last 50
weighted to account for the rest of the beam train (2820 bunches).
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-7
x 10
14
Beam Position at IP / m
12
Electron
10
8
6
Positron
4
2
0
50
100
150
200
Bunch #
250
300
350
IP FFB Kicker Position
BPM
BPM
IP ->
SF1
OCT
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QF1
IP FB Kicker
SD0
QD0
OCT
IP FFB kicker in ~1m gap between 2 cryomodules
near IP.
Distance of kick from SD0 face effects lumi as beam
is kicked off-center going through SD0.
Advantage to using shorter kicker?
100


95
90
85
80
2000
3000
4000
SD0/QD0 x-offset / nm
5000
6000
Fraction Luminosity
Loss due to FFB
1000
90
80
70
60
0
Fraction Luminosity
Loss due to FFB
% Nominal Luminosity
100
% Nominal Luminosity
Effect of SD0/QD0 Offset
500
1000
SD0/QD0 y-offset / nm
1500
0.6
0.4
0.2
0
0
1000
2000
3000
4000
SD0/QD0 x-offset / nm
5000
6000
0.8
0.6
0.4
0.2
0
200
400
600
800
1000
SD0/QD0 y-offset / nm
1200
1400
Luminosity loss as a function of SD0/QD0 offset and relative importance
of offset through SD0 vs. IP offset.
Shows beam size growth through offset SD0 dominant over FFB beam
offset conversion time (more so in vertical plane).

e.g. for y at 500nm offset, ~85% of luminosity loss through beamsize growth
effect, 15% through conversion time of FFB system.
100
Distance
FB
Kick SD0
% Nominal Luminosity
98
96
94
92
0
0.1m
0.2m
0.3m
0.4m
0.5m
90
88
86
84
0



100
200
300
400
RMS SD0/QD0 Offset / nm
500
Mean % Nominal Luminosity (all jitter cases)
Luminosity vs. QD0/SD0 RMS Jitter
and Kick Distance
94.4
94.3
94.2
94.1
94
93.9
0
0.1
0.2
0.3
0.4
FFB Kick - SD0 Distance / m
0.5
Calculate Luminosity loss for different jitter / kick distance cases using ‘SD0 lumi loss’ and
‘FFB lumi loss’ look-up tables (horizontal + vertical).
Left plot shows % nominal luminosity with given RMS SD0/QD0 jitter and varying kickSD0 distance.
Right plot shows all jitter cases plotted vs. kick distance and shows the expected dependence
on kick distance.
Tracking Simulation Results with RMS Offsets of both
Final Doublet Cryomodules
100
% Nominal Luminosity
95
90
85
80
75
70
0


100
200
300
400
500
600
RMS SF1/QF1 + SD0/QD0 x & y vibration / nm
Track 80K macro particles (e- & e+ side) from QF1 -> IP with RMS
SF1/QF1 and SD0/QD0 vibration in horizontal and vertical planes.
Results show mean and RMS of luminosities from a number of
consecutive pulses (100 max).
Summary

Results show added luminosity loss due to jitter of
SD0/QD0 cryomodule.
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These effects need to be convolved with ‘background’
environment of GM and other jitter sources.
Don’t just add this to previous lumi studies.
Results are worse-case here where everything else is
perfect, other errors (e.g. non-linear train shape) will
mask this effect to some degree.
Small effect due to kicker distance from SD0,
becomes more pronounced in cases with larger RMS
jitter.

It is fairly trivial to shorten length of kicker to ~0.2m if
required.
IP FFB Stripline Kicker
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S.Smith design for ILC stripline kicker:
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e.g. FONT kicker:
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2 amps -> 25W 1m stripline gives 100 sigma-y
IP kick (100 ns risetime).
15 amps -> 50W 0.2m stripline (<100 ns
risetime).
Easily increase drive of ILC kicker to allow
length to decrease factor 10.
Possible for larger kicks with ferrite-loaded
kicker.
20 mr Crossing Scheme Kicker
Parameter
Value
Parameter
Value
Length
1m
Current
2 Amps
Turns
1
Voltage
43 Volts
Gap height
20 mm
Power
75 Watt
Inductance
2.5 mH
Rise time
100 ns
(L/Z)
Gap width
40 mm
Impedance
25 Ohms
Max kick
±130 nradians
2 mr Crossing Scheme Kicker
Parameter
Value
Parameter
Value
Length
1m
Current
13 Amps
Turns
1
Voltage
300 Volts
Gap height
180 mm
Power
4 kW
Inductance
1.3 mH
Rise time
100 ns
(L/Z)
Gap width
180 mm
Impedance
12.5 Ohms
Max kick
±100 nradians