Beam In Gap Design Review

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Beam In Gap Design Review

• Michelle Wilinski
• March 26, 2003

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Outline

• Action items from July 2002 Review
• Motivation
• Overview
• AP Analysis Cousineau, et al
• Process Variables
• Acceptance Criteria
• Summary

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July Review Action Items Critical Findings

• Disconnect between diagnostics AP regarding
  magnitude of cleaning kick
• Consensus reached that magnitude should be /-
  7kV
• Number of kicker modules not determined
• Using 3 stripline kickers of 1.5m each in one
  location

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Action Items Observations/Recommendations

• Gap cleaning stripline kickers should be designed
  for 50 ohm impedance in differential mode
• They are designed in this manner
• Pay attention to effective rise time of kicker
  system as multiple kicker modules are powered
  electrically in series
• Done
• Measure of beam in gap to 20 accuracy will be
  difficult
• Working on calibration methods for such
• Gated phototube system will probably be required
• Design has either gated PMT or MCP (R. Witkover)
• Concern regarding achievable absolute accuracy of
  BIG calibration using method of kicking out a
  known quantity of beam not in the gap
• It is a practical method (R. Witkover)

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Motivation

• Should be no beam in the gap from linac
• Chopper should be 100 efficient
• Linac team claims nothing can make it from one
  end of the Linac to the other, and at the same
  time find its way from the mini-bunch to the gap
• However, nuclear scattering, foil losses, RF
  noise, collimation inefficiency, etc. exist
• Experience has taught us that in existing
  machines there is beam in the gap, claimed to
  sometimes be at the percent level
• Loss budget is 10-4. Dont use it up in the gap!

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BIG/Halo Overview

• Hardware used pulser, kicker, FBLM (gated PMT
  or MCP) associated processing electronics,
  collimator and/or scraper and associated motion
  controls
• Gap/Halo calculations performed in LabVIEW
• AP range 0-0.1A
• AP required accuracy 20
• Operated during last 100 turns of accumulation
  cycle

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BIG Block Diagram
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Principle of Operation

• Kick the gap beam onto collimators/scraper
  during last 60-100 turns of accumulation pulser
  duty cycle limited to 100 kicks/machine cycle
• Measure with fast loss monitors (PMT or MCP)
• Function as both gap monitor and gap cleaner
  (reduce activation of extraction region)
• Scraper will be located at wire scanner
  location immediately adjacent to the IPM
• Cross calibrate losses
• Greater sensitivity than collimator

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Gap Cleaning Analysis

• SNS Beam-In-Gap Cleaning and Collimation
• EPAC 2002
• Sarah Cousineau, Indiana
• Daniele Davino, BNL
• Nuria Catalan-Lasheras, BNL/CERN
• John Holmes, ORNL

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BIG Holmes 1
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BIG Holmes 2
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Gap Cleaning Simulation S. Cousineau
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Loss Locations
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Process Variables System Inputs

• Kick polarity
• Determines output polarity of kick (/- or -/)
• Plane to kick
• Determines plane to kick (horizontal or vertical)
• Kick trigger
• When to trigger the pulser for kick(s)
• Tune
• Feedback for proper BIG cleaning
• Power supply on/off
• Remote control for the power supply
• RTDL
• Event Link

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Process Variables - System Outputs

• Kick mode
• Determines mode of pulser operation (Tune or BIG)
• Power supply remote/local
• Readback to determine mode
• Power supply on/off
• Readback to determine if supply is on/off
• Capacitor bank voltage
• Readback to assure power supply is charged as
  expected
• Gap Current
• Amount of beam measured in the gap
• PMT or MCP voltage

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Acceptance Criteria

• List still in development
• Meets applicable FBLM acceptance criteria
• Meets AP specifications
• Range 0-0.1A
• Accuracy 20
• Pulser meets requirements
• Output /- 7kV
• Polarity change turn-by-turn
• Select plane to kick
• 1MHz burst of 60-100 pulses
• System integration demonstrated

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Summary

• One pulser unit kicker to be shared between
  Beam in Gap and Coherent Tune systems
• PC containing standard NI motion control, FDAQ
  digitizer, LabVIEW (Wims template)
• Using gated FBLM for data acquisition
  presentation by R. Witkover to follow

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extras
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Pulser Block Diagram
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Schedule - BIG