Beam in Gap Data Acquisition R' L' Witkover

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Beam in Gap Data Acquisition R. L. Witkover
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Action Items from July 2002 Review

• There is concern that the BIG measurement can be
  calibrated to the 20 resolution level
• The concern is justified. But we believe that the
  20 calibration accuracy is possible.
• Loss studies still need to be done modeling the
  calibration technique.
• Monitoring the losses with a fast detector at a
  single point will not detect the total kicked
  beam loss but it may provide a proportional
  measure.
• Note that the final measure of the BIG efficiency
  would be how much beam hits the extraction kicker
  during the gap time. An additional gated PMT
  should be located viewing the kicker to monitor
  this.

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BIG Measurement Approach

• Limiting apertures are the collimators
• Locate detector near collimators (Further study
  needed)
• Collimators designed to intercept controlled
  losses
• Beam cleaned from gap will be lost in collimators
• In place all the time allows measurement during
  normal operation
• Will be warm area possible high background
  which may make fine measurement difficult
• Beam Halo measurement scraper can be used for
  higher resolution BIG measurement
• Becomes temporary limiting aperture
• Lower background region
• Cannot be used continually losses to high
• Use both approaches

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Loss Distribution Near Collimator
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The Problem

• Estimate of Controlled Losses at the Collimator
• Loss during bunch but may be significantly more
  during commissioning or studies, saturating
  detector
• Gate detector off during bunch to keep from
  saturating

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Gated Photo-multiplier Tubes
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Detector

• Several gated high gain, high speed detectors
  available
• Hamamatsu H7680/-01
• Gated Photo-multiplier
• 5 x 104 gain swing
• 1.7 ns rise time
• Solid state gating and HV ps in unit (in tunnel)
• Hamamatsu R5916U-50
• Gateable Micro-channel plate
• 108 gain swing
• 0.18 ns rise time
• Leaning towards Micro-channel plate

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Wideband Amplifier for FBLM
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Data Acquisition

• With lt 300 nsec gap, need high sample rate ADC to
  acquire signal, such as
• Dedicated 1 GSa/s scope under Labview control
  .Very expensive
• BCM/BPM PCI card with 80-100 MSa/s ADCRequires
  development
• Commercial PCI Fast ADC module
• Acquiris (Module under test at ORNL)
• DP-105 0.5 GSa/s, 8-bit 1 Mb 150
  samples
• DP-110 1.0 GSa/s, 8-bit 2 Mb 300
  samples
• DP-210 2.0 GSa/s, 8-bit 4 Mb 600
  samples
• CompuScope 82G (Gage-Applied) 2GSa/s, 8-bit
  600 samples
• 100 MHz BW, 400 MSa/s, 8-bit 125 samples
• Unit to be determined by BNL-SNS Controls Group

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Calibration

• Technique
• Inject 1 turn (0.1 of full beam)
• Execute resonant gap cleaning during the beam
  pulse
• Measure turn-by-turn change in total charge with
  BCM
• Measure losses at the collimator (or Halo
  Scraper), turn-by-turn, over kick duration
• Measure change in total intensity, turn-by-turn,
  over kick duration
• Need AP studies to estimate accuracy of the
  measurement
• Can 20 be achieved?
• Relative measurement still important
• Estimate of cleaning efficiency can also be made
  by locating a Gated PMT at Extraction Kicker.
• Measure loss at Extraction Kicker during gap with
  BIG cleaner Off and On.

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Summary

• Need to purchase and test samples of Gateable
  PMT-MCP
• Need to coordinate purchase and test of fast PCI
  ADCs with ORNL
• Further simulation and analysis needed for
• Losses caused by Halo scraper due to BIG kick
• Losses at collimator due to BIG kick
• Loss pattern at Extraction Kicker during
  extraction