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Test Ramp for Emittance Calibration. M. Kuhn, V. Kain, F. Roncarolo, B. Dehning, A. G. Ollacarizqueta, G. Trad, J. Gras, J. Emery. Motivation: Emittance versus Intensity Loss. Results from MD I – 15/5/2012: Emittances decrease during the ramp

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test ramp for emittance calibration

Test Ramp for Emittance Calibration

M. Kuhn, V. Kain, F. Roncarolo, B. Dehning, A. G. Ollacarizqueta, G. Trad, J. Gras, J. Emery

motivation emittance versus intensity loss
Motivation: Emittance versus Intensity Loss
  • Results from MD I – 15/5/2012:
    • Emittances decrease during the ramp
  • Emittance shrinkage coincides with intensity loss…
  • Beta functions at wires? Wire scanner calibration?
md ii 25 6 2012
MD II (25/6/2012)

Test Ramp for Emittance Calibration

  • Conditions:
    • intermediate collimator settings
    • 2 bunches per beam with different emittances
  • Wire scanner calibration
    • Orbit bumps at injection and flattop
  • K-Modulation
    • Flattop: point 4
    • Squeeze: point 4 and triplets
  • Wire scans during ramp, squeeze and collision
  • Luminosity data
wire scanner calibration
Wire Scanner Calibration
  • Orbit bumps at 450 GeV and 4 TeV
  • Going from +3mm to -3mm in 1mm steps
    • Wire scanner

B1V, B2H and

B2V similar

  • Calibration OK
    • bump versus wire scanner response fully consistent at flattop and injection
    • The slopes are 1 within the measurement error
    • No energy dependence
k modulation @ 4tev
K-Modulation @ 4TeV
  • RQ6.R4
  • RQ7.R4
  • RQ5.L4
  • RQ5.R4

Beam 1


  • RQ5.R4
  • RQ5.L4
  • RQ6.L4




Beam 2

G. Trad


Before Squeeze

G. Trad


@ 4TeV

Before Squeeze: After Squeeze:

k modulation @ 4 tev
K-Modulation @ 4 TeV

G. Trad

Noisy tune measurements specially at flattop with unsqueezed optics

Preliminary results beta functions at wire scanner:

emittance growth
Emittance Growth
  • Look at emittance growth during ramp
  • Calculate emittance from luminosity at collision
    • Compare with wire scan data
  • Emittance determined with measured betas at injection from Rogelio’s team, at flattop and squeeze from k-modulation, interpolation in between for ramp
  • Error bars indicate difference between in and out wire scan
emittance versus intensity loss
Emittance versus Intensity Loss
  • Results from MD II
    • intermediate collimator settings to not lose intensity
  • Still emittance shrinkage during ramp, but less pronounced than in last MD
  • Almost no intensity loss – not clear whether correlated to emittance decrease!
luminosity data
Luminosity Data
  • Convoluted emittance:
    • Used measured beta from k-modulation at β* = 0.6m for wire scanners
    • Single bunch intensity and bunch length
    • Only same bunch numbers colliding
          • Luminosity: β* error of 15 %, crossing angle error 15 μrad
  • Emittances from wire scans significantly smaller than emittances from luminosity (especially ATLAS)
  • Preliminary results so far…
  • Emittances measured by wire scanners decrease through the ramp.
    • …despite much reduced intensity loss
  • 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