European Southern Observatory New Technology Telescope

General :
Observations :
Operations :

SUSI2 CCD Dewar Refilling

This is the actual procedure to refill the CCD Dewar of SUSI2 once a day, preferably in the morning, at the same time of EMMI dewars refilling:

• Push the wall red interlock.
• Scan the Pulpo for temperature of Sensor #1 :

it should be arround 150 K. (should not excced 152 K).
• Scan the Pulpo for vacuum :

it should be better than 1.0 x10-4.
• If the previous values are noticeable different, do not refill and inform ODT.
• Slowly turn the rotator by hand, watching out that the co-rotator follows it, until the refilling hose of the dewar points to 60 degrees away from the vertical toward the wall red interlock (say 02:00).

It is very important that the dewar electronic conector is not below the nitrogen outlet of the dewar. If this is the case, when the dewar is full, the nitrogen leak will produce severe damage to the sealing of this conector, deteriorating the vacuum.
• If a LN2 tank is empty, IMMEDIATELY  execute NITROGEN TANK exchange procedure.
• Always discharge yourself by touching the instrument structure before touching the CCD dewar

(while holding the metallic LN2 hose in order to discharge the bottle too as it has rubber wheels).
• Remove the metallic ring shape lid of the dewar inlet and slip the tank plastic hose around it.
• Open the tank valve and keep watching (around 10 minutes) until liquid nitrogen overflows from the dewar outlet.
• Close the tank valve.
• Disconect the tank hose from the dewar inlet and remove the tank away of the instrument.
• Put back the lid on the dewar inlet and press it firmly in to seal the inlet.
• Scan AGAIN the Pulpo for vacuum :

it should not have changed significantly.
• Write down the date, time, temperature, pressure and operator signature on the log sheet.
• Release the wall red interlock.
• DO NOT MOVE THE ROTATOR DURING THE NEXT TWO HOURS.
• Fill the log sheet in the control room.

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