Beam in Gap PDR Fast Beam Loss Monitor DAQ Dave Gassner

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Beam in Gap PDRFast Beam Loss Monitor DAQDave
Gassner
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Calibration Cleaning

• Calibration using reduced intensity beam pulse.
• BIG Cleaner
• Extraction kicker
• Clean Beam in Gap
• BIG Cleaner
• Beam lost in Ring Collimator
• Extraction Kicker rising edge (typical extraction
  timing)
• Beam lost in
• Ring collimator
• Ring components
• Extraction Lambertson
• RTBT Dump

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Calibration

• Technique 1
• Inject 1 turn, 15mA 1011 protons
• Fire extraction kicker during beam pulse, 200ns
  rise time
• 1-30ns, beam lost in collimator
• 30-80ns, beam progressively lost in ring
• 80-120ns, loss on Lambertson
• 120-200ns, loss RTBT collimator

15mA
675ns beam
Kicker current 200ns rise to 95

• Measure losses in ring (50ns), FBLMs
• Assume equally distributed at 5 locations
• 1011(50/675)/5 1.5 x109 protons/location

• Technique 2
• Inject 1 turn, 15mA 1011 protons
• Execute resonant gap cleaning during the beam
  pulse
• Measure losses at the collimator

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Loss Pattern for Dirty Gap Extraction Kicker

• As extraction kicker current increases
• Initially beam lost on collimator
• Then on ring components
• Lambertson
• RTBT

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Ring Collimator Losses - What Can We See?

• Controlled Loss Distribution
• SNS AP Tech note 7

Controlled loss 0.19 of 2MW 3.8kW at
collimator. 500 R/hr at cable tray during normal
operation. 2.16 x 105 pulses/hr 2.5mR/pulse
FBLM signal during pulse During 1ms beam pulse
2.5R/sec 2.5R/sec X 100uC/Rad 250uA Beam in
Gap loss 3.8kW/200W 19 times less signal Assume
1 of BIG loss in 10ns (250uA/19)(.01)/(10X10-6)
13.1mA FBLM signal during gap into 50
Ohms 65mV
Assuming 0.1 beam in halo lost in ring collimator
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BIG Kicked at Extraction

• Fire extraction kicker during the gap (1000
  turns, typical extraction timing)
• Observe fast losses
• Ring collimators
• Ring components
• Extraction Lambertson
• RTBT Dump using FBLMs.
• Compare measurements from cleaned and un-cleaned
  gap.

275ns Gap
675ns beam
675ns beam
Kicker current 200ns rise to 95
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Summary

• HEBT laser BIG is gone, and with it our planned
  calibration!
• We can use linac BCM to get relative calibration
  of Ring FBLMs by
• Extracting on 15mA bunch
• Gap cleaning on a 15mA bunch
• We can use this calibration to measure
  beam-in-gap by normal extraction on the
  un-cleaned gap
• We can hope to use this measurement to
  calibrate the FBLM that looks at the collimator
  during gap cleaning
• We can estimate efficiency of gap cleaning by
  spray on (calibrated - see second bullet above)
  Ring FBLMs when we extract with cleaned gap
• Further simulation and analysis needed.