Chamber with Controlled Atmosphere (AIRFLY)

1
Chamber with Controlled Atmosphere(AIRFLY)

• Michal Doubrava CTU Prague
• Václav Vacek CTU Prague
• Libor Nožka, Miroslav Hrabovský, Petr Schovánek,
  Miroslav Palatka, Miroslav Pech, Dušan Mandát
  Joint Laboratory of Optics, Olomouc
• Martina Bohácová, Jan Rídký Institute of
  Physics of Academy of Sciences of the Czech
  Republic

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Purpose of Chamber

• Simulation of Earth atmosphere up to about 30 km
  above its surface

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Variables to Handle

• Operating pressures from 1010 mbar (standard
  atmosphere) to about 0 mbar
• Operating temperatures from normal ambient
  temperature 20 C to about -50 C
• Moisture content of inside atmosphere

4
The First Prototype

• Cooling performance generated by liquid nitrogen
  flow through two heat exchangers
• Regulated flow-rate
• Robust, heavy construction

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The First Chamber Problems

• Chamber started to leak after a few hours of
  cooling (as cold penetrates through body)
• Insufficient cooling performance during the last
  experiment at Van der Graaf accelerator site (too
  high energy dissipation)

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The Second Prototype

• Cooling effect realized by dry ice (CO2), that
  has melting temperature -79 C
• Standard stainless steel vacuum cross should
  secure leak-tightness
• Temperature controlled through heating tape
  that is wound round the cylindrical surfaces
• Other equipment (PMTs, etc.) is placed in
  nitrogen atmosphere to prevent the condensation
  of air moisture on it

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Overview
Placement of heating tape
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Initial Tests

• May 2006, Prague
• Two runs, each with 5 kg of dry ice
• Packing of dry ice lasts more than 5 hours
• The first run with dry ice only
• The second run with implemented heating tape
  (up to 25 W)

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The First Tests Overview
10
Temperature Profile
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Further Steps, Improvements

• More tests should be performed in order to learn
  the behavior of the chamber and to discover
  possible imperfections of this design
• Difficult to estimate the behavior of chamber
  when installed on a beam line
• Installation of additional circuit with liquid
  nitrogen (tube heat exchanger) could assure the
  cooling power
• N2 flush line recommended to reduce
  condensation of moisture on the dry ice crystals

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N2 Flush Line

• Should prevent the air moisture condensation that
  disables dry ice crystals movement
• Unmovable crystals create the air-gap around
  chamber that decreases the cooling performance

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Summary

• Two different prototypes available so far
• The first one worked relatively normally in
  Frascati, so can be used there again (if leakage
  problem is solved) if necessary
• The second prototype could be acceptable for
  measurements in States (AWA, Van der Graaf) but
  needs more testing before its final usage