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IK/JJ May 6 th 2012

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Results from EMMA Injection Line BPM-02 measurements on 25-04-12 May 6 th 2012 Ian Kirkman, James Jones. IK/JJ May 6 th 2012. Slide 0. Measurements. Data taken quickly at end of the final shift of the April 2012 commissioning run (25 th / 26 th )

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slide1

Results from EMMA Injection Line BPM-02 measurements on 25-04-12

May 6th 2012

Ian Kirkman, James Jones

IK/JJ May 6th 2012

Slide 0

slide2

Measurements

Data taken quickly at end of the final shift of the April 2012 commissioning run (25th / 26th)

Initial aims: to demonstrate that the summed value of the 4 pickup voltages from a cylindrical BPM varies linearly with bunch charge; to examine beam position vs bunch charge.

Method:

  • ALICE in SB mode at 5 Hz
  • Switch off DIP-02, monitoring charge in Faraday cup DUMP-01
  • Set ALICE attenuation level (proportional to laser power?)
  • View FC response on ‘scope, and save digitised data to file
  • Issue multiple EPICS ‘caget’ commands at each attenuation level to read BPM-02, and save data to file

IK/JJ May 6th 2012

Slide 1

slide3

Measurements

Oscilloscope screens for attenuation level at the 2 extreme values, 1.0 (left) and 0.3 (right)

  • For each attenuation value:
  • 10000 points in each saved data file
  • Determine background level from mean and σ of points 500-2500
  • Determine background subtracted peak height, and apply ± σ
  • Note that below attenuation ~ 0.3, the pulse becomes hard to distinguish

IK/JJ May 6th 2012

Slide 2

slide4

Variation of Bunch Charge from FC with Attenuation level

  • The ‘threshold’ attenuation level required for non-zero bunch charge in EMMA is ~ 0.1

IK/JJ May 6th 2012

Slide 3

slide5

Details of data analysis at attenuation value = 0.3

  • Pedestal values v4 and v8 are nicely constant, with ~ 1mV jitter
  • Apparent jitters on horizontal (Xm) and vertical (Ym) beam positions
  • Apparent systematic variation of mean Xm and Ym with attenuation level (slides 6, 7, 8)

IK/JJ May 6th 012

Slide 4

slide6

Variation of 4 Summed Pickups with Attenuation Level

  • Nicely linear with reasonable statistics
  • Threshold attenuation level again ~ 0.1

IK/JJ May 6th 2012

Slide 5

slide7

Horizontal bunch movement with bunch charge (IL-BPM02)

  • Systematic narrowing of the horizontal spread of positions with increasing bunch charge
  • Systematic mean movement outwards with increasing bunch charge

IK/JJ May 6th 2012

Slide 6

slide8

Vertical bunch movement with bunch charge (IL-BPM02)

  • Indication of downwards beam movement with increasing bunch charge (to Att. ~ 0.7)
  • Some indication of vertical narrowing (again to Att. ~ 0.7)

IK/JJ May 6th 2012

Slide 7

slide9

Beam positions at IL BPM-02 with bunch charge

  • Summarises plots in slides 6 and 7

IK/JJ May 6th 2012

Slide 8

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