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Beam in Gap PDR Fast Beam Loss Monitor DAQ Dave Gassner

Beam in Gap PDR Fast Beam Loss Monitor DAQ Dave Gassner. 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)

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Beam in Gap PDR Fast Beam Loss Monitor DAQ Dave Gassner

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  1. Beam in Gap PDRFast Beam Loss Monitor DAQDave Gassner

  2. 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 SNS BIG & FBLM

  3. Calibration 15mA • 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 675ns beam Kicker current 200ns rise to 95% • Measure losses in ring (50ns), FBLM’s • 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 SNS BIG & FBLM

  4. Loss Pattern for Dirty Gap – Extraction Kicker • As extraction kicker current increases: • Initially beam lost on collimator • Then on ring components • Lambertson • RTBT SNS BIG & FBLM

  5. 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 SNS BIG & FBLM

  6. 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 FBLM’s. • Compare measurements from cleaned and un-cleaned gap. 275ns Gap 675ns beam 675ns beam Kicker current 200ns rise to 95% SNS BIG & FBLM

  7. 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 FBLM’s when we extract with cleaned gap • Further simulation and analysis needed. SNS BIG & FBLM

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