Test Ramp for Emittance Calibration
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Transcript of Test Ramp for Emittance Calibration
LHC
Test Ramp for Emittance Calibration
M. Kuhn, V. Kain, F. Roncarolo, B. Dehning, A. G. Ollacarizqueta, G. Trad, J. Gras, J. Emery
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LHC
Motivation: Emittance versus Intensity Loss
o Results from MD I – 15/5/2012:− Emittances decrease during the ramp
o Emittance shrinkage coincides with intensity loss…o Beta functions at wires? Wire scanner calibration?
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LHCMD II (25/6/2012)
Test Ramp for Emittance Calibration
o Conditions:− intermediate collimator settings − 2 bunches per beam with different emittances− Cycle: RAMP - SQUEEZE - COLLISION
o Wire scanner calibration− Orbit bumps at injection and flattop
o K-Modulation− Flattop: point 4− Squeeze: point 4 and triplets
o Wire scans during ramp, squeeze and collision o Luminosity data
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LHC
o Orbit bumps at 450 GeV and 4 TeVo Going from +3mm to -3mm in 1mm steps
− Wire scannerB1V, B2H andB2V similar
o Calibration OK− bump versus wire scanner response fully consistent at flattop and injection− The slopes are 1 within the measurement error− No energy dependence
Wire Scanner Calibration
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LHCK-Modulation @ 4TeV
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BEFORE THE SQUEEZE AFTER THE SQUEEZE
BEFORE THE SQUEEZE AFTER THE SQUEEZE
Bea
m 1
Bea
m 2
• RQ5.L4• RQ5.R4
• RQ6.R4• RQ7.R4
• RQ5.R4• RQ5.L4 • RQ6.L4
G. Trad
LHC
K-Modulation @ 4TeV
Before Squeeze: After Squeeze:
Before Squeeze
G. Trad6
LHC
o Noisy tune measurements specially at flattop with unsqueezed optics
o Preliminary results to be compared− With last MD data (K-Modulation @ 450 GeV)− With the Beta-Beating measurements
K-Modulation @ 4 TeV
G. Trad7
LHCEmittance Growth
o Look at emittance growth during rampo Calculate emittance from luminosity at collision
− Compare with wire scan data
o Emittance determined with measured betas at injection and flattop from Rogelio’s team, interpolation in between
o Error bars indicate difference between in and out wire scan
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LHC
o Results from MD II − intermediate collimator settings to not lose intensity
o Still emittance shrinkage during ramp, but less pronounced than in last MDo Almost no intensity loss – not clear whether correlated to emittance
decrease!
Emittance versus Intensity Loss
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LHC
o Convoluted emittance:− Used measured beta at β* = 0.6m for wire scanners− Single bunch intensity and bunch length
Luminosity: β* error of 15 %, crossing angle error 15 μrad No wire scan data for B2V
o Emittances from wire scans significantly smaller than emittances from luminosity (especially ATLAS)
o Need to check with k-modulation betas
Luminosity Data
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εL [μm] Wire Scan From CMS Luminosity
From ATLAS Luminosity
Bunch 1 4.94 +/- 0.60 5.77 +/- 0.87 6.88 +/- 1.03Bunch 2 2.55 +/- 0.50 3.05 +/- 0.46 3.80 +/- 0.57
LHCSummary
o Preliminary results so far…
o Emittances measured by wire scanners decrease through the ramp.− …despite much reduced intensity loss
o MD to − measure emittances with wires during ramp, squeeze and collisions− measure betas at wires− Re-calibrate wires− Compare to data from luminosity− …to finally know whether the normalized emittances are really smaller at flattop
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LHC
Back up
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LHC
o Emittances grow until ~ 1/3 of Ramp, then decreaseo Except for Beam 2 H
Emittance at Ramp
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LHCAfter Squeeze
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