How can I do an emergency filling of Coralie?

Manual emergency filling of the cryostat must be undertaken when the cryostat run out of nitrogen AND if the temperature of the CCD is under -10 degrees.

It's forbidden to cool the cryostat if the CCD is hot, because in this case the cryostat needs a (emergency) pumping.

The informations concerning the temperatures are written on the monitoring screen of the CCDs.

There are several possibilities for the CCD to heat up, all of which are related to the fact that the cryostat tank has not been filled sufficiently. These are:

The dewar (TP 60) was empty for the last filling.
The dewar was overfilled, with a pression too low preventing the necessary quantity of nitrogen from being sent to the tank of the cryostat
The valve #1 is closed preventing nitrogen from going to the cryostat.
Nitrogen line's leaking.
Bad quality of nitrogen (gas-polluted)
Hardware failure of the electrovalve or timer.

Procedure

There are 2 fill-ups per day for Coralie at a fixed time (according to GMT)

One after the observations, the other before noon. It is possible to check the schedule with this software and look at the temperature in the lakeshore tab.

In case you have the feeling that the refilling is close and that the situation is not dramatic, do not do anything because the refilling will take place and it is useless to make 2 refilling consecutively.

In other case, the procedure is to take a control manual of the timer controlling the electrovalve is:

In the bodega first locate the timer:

Open the timer:

>>>>

You can see 2 "hand" symbols: Hand#1 and Hand#2.

Press Hand#2 (only one time) you will heard the sound coming from the électrovalve and the nitrogen going to the cryostat.

After a few minutes, the excess nitrogen will come out as a drop through this pipe:

It's moment to stop the manual feeling by pressing 3 times the button HAND#2.

You must get this display:with two small clock:

End of the operations

In case of repetitive problems

Check for leaks in the nitrogen line. These leaks can only be detected when filling the cryostat.

So either you have to be there at the right time, or you have to refill manually, if possible in the morning so that the local Coralie has time to stabilize in temperature.

The case of leakage is relatively common, between 6 and 24 months.

Leaks occur (normally) on the connectors, i.e. at the ends. The line near the electrovalve and near the cryostat in the Coralie enclosure must be checked for leaks.

Caution: entering the Coralie enclosure disturbs the thermal environment. Furthermore, the Coralie enclosure contains the optical fibres, which must be given absolute attention. Damage to them will result in the loss of the instrument for several months.

It's best not to do anything if you don't have the skills for this check.

These leaks can only be repaired by qualified personnel.

LW 28/04/2020