FOCAS Cooler Start-up manual

Note

CCDs should be operated under -100C. To avoid dew condensation within the dewar containing CCDs and the electronics circuit, they should be kept under high vacuum environment while the cooler is operating. Breaking the vacuum under <-10C would seriously damage the CCD system.

Introduction

There are two electrical configurations of the cooler power supply: External and Internal. Please understand which mode the FOCAS is in.

External mode: the power is supplied from the wall outlet. Only local power on/off can be possible.

This is only for maintenance, or while the instrument exchange.

[wall outlet] --- (AC120V) --- (A)

Internal mode: the power is supplied from the flange. The power is controlled remotely through computer-controlled solid state relay (SSR).

This is for normal operation while observing.

[flange power connector] --- (AC120V) --- [FOCAS main power distribution panel --- breaker] --- [SSR Relay] --- (B)

(A) or (B) is connected to the cooler controller

(A) or (B) --- [cooler controller --- orange power switch] --- (DC 12V) --- [cooler]

The cooler controller is mounted at the lower portion of the FOCAS. White panel seen in the above picture is the controller. You can see an orange switch (covered with a black tape) at the left edge of the panel. The orange light is ON when the cooler is in operation. An AC-120V outlet (gray) connected from the panel is the power supply socket (A) or (B). The socket (B) is marked as "REMOTE".

(A) or (B) is connected to the cooler controller. Internal or External modes can be switched by re-connection of the power cable manually.

Check items before powering on the cooler

Vacuum gauge reads 3E-4 torr or less.
An ion pump is running.
External pump is detached.

Procedure for start cooling

Check the vacuum condition (see above)
Check which socket (A) or (B) is connected to the controller. Replace the socket when requested to do so (ask SA).
If in the remote mode (B is connected)

open the FOCAS main power distribution panel, and check the cooler breaker is ON.
Ask SA to power it on remotely from the computer.

If in the local mode (A is connected)

Connect another power socket to the wall outlet.

Check if the orange power switch is ON.
Check the CCD temperature.

If temperature drops 0.1C in about 30 second, it is normal. Note that it will take a few minutes before the first temperature drop of 0.1C due to heat resistance inside the CCD dewar.
Wait for a while (~5 min.) to see the temperature goes down at least 0.5C.

Ask SA to monitor the temperature remotely.