IK/JJ May 6th 2012Slide 0

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

May 6th 2012

Ian Kirkman, James Jones

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.

IK/JJ May 6th 2012

Measurements

Slide 1

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

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

IK/JJ May 6th 2012

Measurements

Slide 2

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

Variation of Bunch Charge from FC with Attenuation level

Slide 3

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

IK/JJ May 6th 012

Details of data analysis at attenuation value = 0.3

Slide 4

• 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 2012

Variation of 4 Summed Pickups with Attenuation Level

Slide 5

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

IK/JJ May 6th 2012

Horizontal bunch movement with bunch charge (IL-BPM02)

Slide 6

• 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

Vertical bunch movement with bunch charge (IL-BPM02)

Slide 7

• 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

Beam positions at IL BPM-02 with bunch charge

Slide 8• Summarises plots in slides 6 and 7