Xray Survey System: Gas subsystem

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X-ray Survey SystemGas sub-system

• K. McFarlane
• Hampton University
• CERN, Feb 13-20, 2001

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Summary

• Purpose gain and wire-position surveys on
  completed barrel TRT modules.
• Requirements
• Proposed gas system for X-ray survey system
  (XRSS).

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Requirements

• Gain to 2 at at least 14 points on every straw
• XY position to 0.05 mm at 4 points on many
  straws
• Z position to 1 mm
• Complete each survey in one day

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X-ray survey system (XRSS)

• Micro-focus 80kV tube
• XY linear motions with resolution of 0.01mm in X
  and 0.2mm in Z
• GasSiplex front-end chips
• Cross-point switch, amplifiers and multi-channel
  analyzer DAQ
• PC-based readout and control
• Analysis by paw or ROOT

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Schematic
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Safety, H S

• Gases used are non-toxic (except in a fire), and
  not flammable, but do exclude oxygen
• A full cylinder of Argon exhausting into the XRSS
  room in a short time can reduce the oxygen level
  below 19 (cf. 21)
• A leak of CO2, can raise the fraction of CO2
  above 5 000 ppm (the OSHA limit)
• ODH detection and training necessary.

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Gas system

• Active gas for gain test likely has three
  components Ar, CO2, CF4 optimum proportions are
  not completely determined.
• Normal gas for flushing outside of straws is CO2
• No contaminants (esp. not Si) should be
  introduced
• No active gas analysis.

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Basic schematic
GPIB
Controller
ODH
Channel 1
PT
Channel 2
Module
Channel 3
Channel 4
Each channel cylinder, regulator, manual valve,
flow controller.
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Features

• Oxygen and CO2 levels in room monitored
• System allows mixing of three components, to
  about 2 accuracy on each component
• Could use pre-mix
• Flow rate envisaged is up to 3 vols/h for above
  precision (baseline is 1 vol/h)
• Active gas can be re-circulated through module.

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Equipment selection

• Industrial ODH monitors (oxygen and carbon
  dioxide levels)
• High-purity or UHP gases and components
• Wetted parts are stainless steel, nylon, Viton,
  Kel-F, brass, nickel, chrome
• No grease of any kind

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Equipment

• Oxygen monitors (fixed and portable) from
  BioSystems CO2 from Telaire.
• Gases are zero, research, or UHP grade from
  Air Products, Scott, or Matheson
• Cylinders are as supplied by gas company
• Regulators will be Scott Model 218
• Manual valves will be Swagelok BN series (SS
  bellows).

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Equipment and components

• Flow controllers and pressure transducer will be
  MKS Instruments.
• Tubing will be electro-polished stainless steel
  (Valex) or nylon.
• Fittings will be stainless steel (cleaned by us)
• Controller will be an MKS 8-channel controller
  with GPIB to BridgeView.

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Issues

• How leak-tight is the radiator volume?
• Is the 70/20/10 Ar/CO2/CF4 the correct mix for
  gain tests for barrel modules?
• What gas should be used for flushing the radiator
  volume? CO2 as in the TRT? An Ar/CO2 mix? The gas
  from the module?
• Can a different (cheaper?) gas be used for wire
  position surveys? (contd.)

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Issues (contd)

• What is Hamptons responsibility?
• HV aging done at Duke/IU
• Basic testing (and repair) done at Duke/IU
• On gain survey, how many points are needed (plan
  is for 14 per straw)?
• On wire position (relative to mounting pins), how
  many wires (4 places per wire)?
• Should Hampton plan to do tension testing? Wire
  replacement?

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Current status

• All components on hand or on order, except bulk
  CF4. Pre-mix Ar/CO2/CF4 on hand.
• Gas system is to be assembled and tested