FIES building

The temperature setting for the front room was lowered by 2 degrees to allow for excess heat in the FIES room to be removed quicker. The precise temperature difference with the FIES room is not clear as there are doubts about the precise calibration of the sensors, but the front room which is actively cooled is now thought to be colder than the FIES room.

To limit the heating of the FIES room we are still looking at the option to never have the vacuum pump in the FIES room. For this an extended tube should be installed which allows the dewar to be connected to a pump in the front room. Also, a remotely operable valve should be installed on the FIES dewar so there is no need to enter the FIES room at all when the dewar needs to be pumped, while the excess heat generated by the pump does not enter the FIES room either. Note that this also implies that we do not need to touch the detector dewar anymore to attach the tube of the vacuum pump. We have noted in the past that touching the dewar causes shifts of the detector and consequently shifts in the Echellogram which can affect the long-term stability. Also, on one occasion the noise in the detector increased because some cables connected to the controller were accidentally moved.