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Pumping and cooling CCD#4

Sometimes the O2 soaking of CCD#4 fails and the preparation procedure must be repeated. This procedure must therefore be started at least 2 days before an observing run.

If CCD#4 is warm, the full preparation recipe must be followed. If a mistake is made, start again!

  1. Switch on the CCD controller
  2. Heat the CCD to +35°C to evaporate gases/polution from its surface by:
    • Select CCD temperature on the display using the two black buttons right to the display.
    • Set CCD temperature to +35°C using the third black button, positioned a little further from the display.
  3. Connect pump to dewar with pump and dewar valves closed.
  4. Start pump, open the pump valve and after a few seconds (when the pump has got up to at least 15KRPM) open the dewar valve. When the pump display says Normal Operation 75 KRPM, pump for at least 12 hours.
    Vacuum should be between 10E-3 and 10E-4 bar after this.
  5. Close dewar and pump valves and disconnect the pump pipe.
  6. On the N2/O2-bottle, blow a stream of N2/O2 mixture through the tube for at least 5mins to clear any contaminants.
  7. Set the flow to a value such that blocking the tube with your finger does not give a big pressure increase.
  8. Blow the N2/O2 mixture over the dewar valve area to fill the valve cavity with clean air. Fix the tube onto the valve on the CCD dewar and open the valve on the dewar in small steps to suck in N2/O2.
  9. After some seconds, stop heating of the CCD by resetting the CCD controller on the on/off switch.
  10. Close the valve, shut off the flow of N2/O2, set the CCD heater to -100°C, and wait at least 30 minutes.
  11. Connect pump to dewar with dewar valve closed and pump valve open.
  12. Start pump, and after a few seconds when the pump display says 15 KRPM, open valve on dewar. This ensures that you get the right direction of the air in the pipe. When the pump display says Normal Operation 75 KRPM, pump for about 10-15 mins, until achieving a vacuum of less than 10E-3 bar.
  13. Cool the CCD by filling the dewar with LN2, and when the LN2 can (not the CCD!) temperature reaches -50°C, close the valves and switch off the pump.
  14. Wait until the CCD reaches a temperature of near -60°C and take some flatfields.
  15. How to identify a failed O2 soak
Back to top Last modified: May 31 2023