Opening

As the internal temperature of NOTCam finally comes within a few degrees of ambient temperature, the vessel can be opened.

At least the following equipment will be required:

• An adequately clean room with space for various dismounted parts.
• A selection of mm-size hex-keys.
• A bottle with at least 1m of dry air, with hose and KF25 fitting.
• A hoist or other lifting device.

The opening procedure is as follows:

1. The first thing to do is to move the instrument to a room where it can be opened without getting too dirty, and where some device for lifting the top half off is available. When handling parts that are to be in vacuum, use gloves or keep hands clean.

2. While the inside is still evacuated, remove all the nuts holding the two halves together. Doing this after pressurization will be more difficult, and will wear the threads down faster.

3. Fill the vessel with dry air to a pressure of 1 Bar. To do this, a bottle of dry air must be connected to the valve using a hose and KF25 fittings. It is very important that the hose is clean on the inside. This can be ensured by evacuating the hose before it is used. Assuming that the hose is clean, adjust the valves of the bottle so that air is flowing at a slow rate. Then hold the hose against the KF25 valve by hand - do not fasten it using a clamp, and open the valve. It will take several minutes to fill the vessel. You will know that it is at 1 Bar when the fitting is no longer sucked onto the valve. Close the valve and leave the vessel to rest for 15 minutes or more, so that the majority of pores are filled with dry air.

4. Remove the entrance window flange by unscrewing the 10mm bolts around the outer rim. An O-ring with aluminum rings around it will probably stick to the vessel. Leave it there, as you then avoid the hassle of putting it back later.

5. The entrance baffle must be then be removed. First step is to lift off the super-insulation cap. Then the baffle plate can be removed by unscrewing the bolts at the edge, and then the spherical reflector is removed. Do not touch the spherical part of it.

6. Now the top half of the vacuum vessel can be lifted off. This should be done very carefully, because the O-ring between the halves may stick so well to both surfaces that the bottom is lifted also, and it may suddenly drop when the O-ring let go of it. Therefore, lift the upper part until the bottom is just barely in contact with it's support. Most likely, the bottom will drop after a short while, otherwise it might be necessary to push down on the bottom half. When the bottom is no longer sticking to the top, lift the top about 2 centimeters and place the O-ring back into it's groove. Then lift the top half clear of the cold shield inside.

7. Removing the cold shield: The lower super-insulation blanket is kept tight around the junction by a string of PTFE cable, which must be removed. Then loosen the eight screws that are keeping the upper cold shield in place. These are partly hidden in the insulation. The thread in one of the fasteners is very poor. For removing the shield, lift at the holes for cable entry and the entrance window. Avoid bumping the shield against the instrument inside. If a temperature sensor is mounted on the back of the detector flange it can easily be damaged or displaced.