Test ramp for emittance calibration
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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

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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

  • Emittance shrinkage coincides with intensity loss…

  • Beta functions at wires? Wire scanner calibration?


MD II (25/6/2012)

Test Ramp for Emittance Calibration

  • Conditions:

    • intermediate collimator settings

    • 2 bunches per beam with different emittances

    • Cycle: RAMP - SQUEEZE - COLLISION

  • 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

  • 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

  • RQ6.R4

  • RQ7.R4

  • RQ5.L4

  • RQ5.R4

Beam 1

AFTER THE SQUEEZE

  • RQ5.R4

  • RQ5.L4

  • RQ6.L4

BEFORE THE SQUEEZE

AFTER THE SQUEEZE

BEFORE THE SQUEEZE

Beam 2

G. Trad


Before Squeeze

G. Trad

K-Modulation

@ 4TeV

Before Squeeze: After Squeeze:


K-Modulation @ 4 TeV

G. Trad

Noisy tune measurements specially at flattop with unsqueezed optics

Preliminary results beta functions at wire scanner:


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

  • 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

  • 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)


  • Summary

    • 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


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