ground motion
DESCRIPTION
F.O.N.T. Ground Motion. From Ground Motion studies by A.Seryi et al. (SLAC). ‘Fast’ motion (> few Hz) dominated by cultural noise Concern for structures with tolerances at nm level (Final Quads). G.R.White: 1.6.2001. F.O.N.T. Luminosity Loss at IP. - PowerPoint PPT PresentationTRANSCRIPT
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
From Ground Motion studies by A.Seryi et al. (SLAC)
• ‘Fast’ motion (> few Hz) dominated by cultural noise
• Concern for structures with tolerances at nm level (Final Quads)
Ground Motion
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Luminosity Loss at IP
• Relative offsets in final Quads due to fast ground motion leads to beam offsets of several y (2.7 nm for NLC-H 490 GeV).
•Correct using beam-based feedback system or by active mechanical stabilization of Quads or both.
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
LC Bunch Structure
NLC-H 500 NLC-H 500 GeVGeV
TESLA 500 TESLA 500 GeVGeV
CLIC CLIC
500 GeV500 GeVParticles/Bunch x Particles/Bunch x
10101010 0.750.75 2.02.0 0.40.4
Bunches/trainBunches/train 190190 28202820 154154
Bunch Sep (ns)Bunch Sep (ns) 1.41.4 337337 0.70.7xx//y y (nm)(nm) 245 / 2.7245 / 2.7 553 / 5553 / 5 202 / 2.5202 / 2.5
•Feedback system demonstrated for NLC-H 500 GeV
•Can be modified for use at TESLA and CLIC
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Beam-Beam Interaction
•Beam-beam EM interactions at IP provide detectable signal
•Beam-beam interactions modelled with GUINEA-PIG
•Shown is the kick angle and percentage luminosity loss for different vertical beam offsets
0 10 20 30 400
20
40
60
80
100
Vertical Beam Offset ( sy )
% L
um
ino
sity
Lo
ss
0 10 20 30 400
50
100
150
200
250
300
Vertical Beam Offset ( sy )
Be
am-B
eam
Kic
k (
mra
d )
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Fast Feedback Operation
Kicker Gain
Bunch Charge
•Measure deflected bunches with BPM and kick other beam to eliminate vertical offsets at IP
•Feedback loop assesses intra-bunch performance and maintains correction signal to the kicker
•Minimise distance of components from IP to reduce latency
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Feedback Components
Stripline BPMStripline BPM
Distance to IPDistance to IP
Stripline radiusStripline radius
Stripline WidthStripline Width
Stripline lengthStripline length
Stripline ImpedanceStripline Impedance
Roundtrip timeRoundtrip time
4.3 m4.3 m
1 cm1 cm
4.4 mm4.4 mm
10 cm10 cm
50 50 0.7 ns0.7 ns
Stripline KickerStripline Kicker
Distance to IPDistance to IP
Stripline radiusStripline radius
Stripline lengthStripline length
Stripline ImpedanceStripline Impedance
Roundtrip timeRoundtrip time
Azimuthal coverageAzimuthal coverage
Drive voltage requiredDrive voltage required
Drive Power 100nm correctionDrive Power 100nm correction
4.3 m4.3 m
6 mm6 mm
75 cm75 cm
50 50 5 ns5 ns
120 degrees120 degrees
250 mV/nm250 mV/nm
12.5 W12.5 W
•BPM response peak near 714 MHz bunch spacing frequency
•Kicker rise-time represents slowest component
•System Design by Steve Smith (SLAC)
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Feedback Simulation
•Simulations performed using Simulink in Matlab
[[0 SIGMA_Y]; [267e-9 0]]
Y Posi tionBeam 2
[[0 Y_OFFSET ]; [267e-9 0]]
Y Posi tionBeam 1
T erm inator
In1
In2
Store Beam Info
Round-tripDelay
In1
Kicker Angle
Kicker Monitor
Kicker
IP angle Def lection at BPM
IP-to-BPMDynamics
IP scope
Beam 1
Beam 2Out1
IPDynamics
1
Gain1
1Gain
[[0 bunch_charge]; [250e-9 0]]
Bunch ChargeBeam 2
[[0 bunch_charge]; [ 250e-9 0]]
Bunch ChargeBeam 1
Q
Y Out1
Beam2
Q
Y Out1
Beam1In1 Out1
Beam Ji tter
BeamQ
Y
BeamParameters
BPMCableDelay
Kick angleKick at IP
BPM-to-IPDynamics
BPMScope
Beam In Position Out
BPM
[[0 SIGMA_Y]; [267e-9 0]]
Y Posi tionBeam 2
[[0 Y_OFFSET ]; [267e-9 0]]
Y Posi tionBeam 1
T erm inator
In1
In2
Store Beam Info
Round-tripDelay
In1
Kicker Angle
Kicker Monitor
Kicker
IP angle Def lection at BPM
IP-to-BPMDynamics
IP scope
Beam 1
Beam 2Out1
IPDynamics
1
Gain1
1Gain
[[0 bunch_charge]; [250e-9 0]]
Bunch ChargeBeam 2
[[0 bunch_charge]; [ 250e-9 0]]
Bunch ChargeBeam 1
Q
Y Out1
Beam2
Q
Y Out1
Beam1In1 Out1
Beam Ji tter
BeamQ
Y
BeamParameters
BPMCableDelay
Kick angleKick at IP
BPM-to-IPDynamics
BPMScope
Beam In Position Out
BPM
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
BPM Processor3 ns rise- time
[[0 SIGMA_Y]; [267e-9 0]]
Y Posi tionBeam 2
[[0 Y_OFFSET ]; [267e-9 0]]
Y Posi tionBeam 1
T erm inator
In1
In2
Store Beam Info
Round-tripDelay
In1
Kicker Angle
Kicker Monitor
Kicker
IP angle Def lection at BPM
IP-to-BPMDynamics
IP scope
Beam 1
Beam 2Out1
IPDynamics
1
Gain1
1Gain
[[0 bunch_charge]; [250e-9 0]]
Bunch ChargeBeam 2
[[0 bunch_charge]; [ 250e-9 0]]
Bunch ChargeBeam 1
Q
Y Out1
Beam2
Q
Y Out1
Beam1In1 Out1
Beam Ji tter
BeamQ
Y
BeamParameters
BPMCableDelay
Kick angleKick at IP
BPM-to-IPDynamics
BPMScope
Beam In Position Out
BPM
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Feedback Performance
Latency = 37.3 nsLatency = 37.3 ns
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Feedback Performance
[[0 SIGMA_Y]; [267e-9 0]]
Y Posi tionBeam 2
[[0 Y_OFFSET ]; [267e-9 0]]
Y Posi tionBeam 1
Terminator
In1
In2
Store Beam Info
Round-tripDelay
In1
Kicker Angle
Kicker Monitor
Kicker
IP angle Def lection at BPM
IP-to-BPMDynamics
IP scope
Beam 1
Beam 2Out1
IPDynamics
1
Gain1
1Gain
[[0 bunch_charge]; [250e-9 0]]
Bunch ChargeBeam 2
[[0 bunch_charge]; [ 250e-9 0]]
Bunch ChargeBeam 1
Q
Y Out1
Beam2
Q
Y Out1
Beam1In1 Out1
Beam Ji tter
BeamQ
Y
BeamParameters
BPMCableDelay
Kick angleKick at IP
BPM-to-IPDynamics
BPMScope
Beam In Position Out
BPM
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Kicker Gain Optimisation
[[0 SIGMA_Y]; [267e-9 0]]
Y Posi tionBeam 2
[[0 Y_OFFSET ]; [267e-9 0]]
Y Posi tionBeam 1
Terminator
In1
In2
Store Beam Info
Round-tripDelay
In1
Kicker Angle
Kicker Monitor
Kicker
IP angle Def lection at BPM
IP-to-BPMDynamics
IP scope
Beam 1
Beam 2Out1
IPDynamics
1
Gain1
1Gain
[[0 bunch_charge]; [250e-9 0]]
Bunch ChargeBeam 2
[[0 bunch_charge]; [ 250e-9 0]]
Bunch ChargeBeam 1
Q
Y Out1
Beam2
Q
Y Out1
Beam1In1 Out1
Beam Ji tter
BeamQ
Y
BeamParameters
BPMCableDelay
Kick angleKick at IP
BPM-to-IPDynamics
BPMScope
Beam In Position Out
BPM
Luminosity loss as function of Luminosity loss as function of gain input and beam offsetgain input and beam offset
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Luminosity Performance
•Lower gains gives better performance at smaller offsets, higher gains give better performance at higher offsets
•Vary gain dependent on observed beam conditions
0 5 10 15 20 25 30 35 400
10
20
30
40
50
60
70
80
90
100
Vertical Beam Offset ( sy )
% L
um
ino
sit
y L
os
s Feedback OffGain = 4.0 ́10 -6
Gain = 5.0 ́10 -6
Gain = 6.4 ́10 -6
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Bunch Jitter Effects
•Introduction of random bunch-bunch jitter causes feedback system to exacerbate luminosity loss at larger gains
•Shown is the effect of randomly offsetting the bunches in a train about a zero offset, assuming a gaussian noise distribution
1e-7 4e-6 8e-6 1.2e-5 1.6e-5 2.0e-50
10
20
30
40
50
60
70
Kicker Gain
Pe
rce
nta
ge
Lu
min
os
ity
Lo
ss
No Beam Offset
Beam Jitter RMS = 0.1 sy
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Effect of Angle Offset
0 1 2 3 40
10
20
30
40
50
60
70
Vertical Beam Angle Offset ( sy'
)
Pe
rcen
tag
e L
um
ino
sity
Lo
ss
0 0.5 1 1.5 2 2.5 3 3.5 40
0.5
1
1.5
2
2.5
3
3.5
4
Vertical Beam Offset ( sy'
)
Be
am-B
eam
Kic
k ( m
ra
d )
•Beams get small additional kick if incoming with non-compensated crossing angle, also additional lumi loss
•Effect not addressed with this feedback system- if significant angle offset present, additional feedback system further up-stream of IP required
y’y’= 27 = 27 radrad y’y’= 27 = 27 radrad
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
IR Layout With FB System
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
IR Pair Backgrounds
•e+e- Pairs and ’s produced in Beam-Beam field at IP
•Interactions with material in the IR produces secondary e+e- ,, and neutron radiation
•Study background encountered in Vertex and tracking detectors with and without FB system and background in FB system itself
•Use GEANT3 for EM radiation and Fluka99 for neutrons
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
EM Backgrounds at BPM
•Absorption of secondary emission in BPM striplines source of noise in Feedback system
•System sensitive at level of about 3 pm per electron knocked off striplines
•Hence, significant noise introduced if imbalanced intercepted spray at the level of 105
particles per bunch exists
•GEANT simulations suggest this level of imbalance does not exist at the BPM location z=4.3m for secondary spray originating from pair background
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Detector EM Backgrounds
•Insertion of feedback system at z=4.3 m has no impact on secondary detector backgrounds arising from pair background
•Past studies suggest backgrounds adversely effected only when feedback system installed forward of z=3 m
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Detector n Backgrounds
Default IR: 6.6 Default IR: 6.6 ± 1.5 × 10± 1.5 × 1099
IR with FB: 8.6 ± 2.6 × 10IR with FB: 8.6 ± 2.6 × 1099
(neutrons/cm(neutrons/cm22/1 MeV n equiv./yr)/1 MeV n equiv./yr)
•No significant increase in neutron flux in vertex detector area seen arising from pair background
•More statistics being generated
VTD Layer
Hit
s/cm
2 /1
MeV
n e
qu
iv./y
r
G.R.White: 1.6.2001G.R.White: 1.6.2001
F.O.N.F.O.N.T.T.
Summary
•Ground motion moving final Quads major source of luminosity loss at a future linear collider
•Fast IP feedback system simulations shows considerable luminosity recovery even beyond linear kick region
•Backgrounds do not seem to be an issue for detector components or the FB system itself in suggested BPM and kicker installation positions
•Hardware tests commencing at SLAC (Simon Jolly)
•Simulations to be extended to include TESLA and CLIC