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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