Probably the most urgent thing to do with the camera is to get the dewar attached to the vacuum pump, and under vacuum. The CIRSI dewar is shipped with a small vacuum valve attached and with the unit under vacuum. This has to be removed and the large diameter valve with vacuum gauge and T-piece are then attached to the vacuum dewar. It is perfectly practical to pump the CIRSI dewar with it still inside its packing case. It is not necessary to remove it from the case in order to start this procedure. Once it is pumping you can take your time assembling the hardware and the computer systems. As part of the pumping procedure it is good to attach the getter supply so that the sorb pump inside the dewar can be properly purged. This requires a power supply that delivers 20 volts and 1.1 amps to be attached to the connector from the auxiliary port that has two wander plugs (one red and one black) attached to it (these wander plugs may just be bare ends of wire, but they are marked). There has been some evidence of a change in the wiring and you may find that it operates with a Laura voltage and a higher current. You should try to operates its at approximately 20 Watts power. The power supply should be run for about two hours while the system is pumping. You may well see the vacuum level increase substantially while this is underway but it should eventually start to improve again. Once the getter supply has been turned of the vacuum should improve considerably. It should be able to get down to perhaps 10^-5 at a pinch.
There are two metal plates. One is large and round while the other is smaller and rectangular with its corners removed. CIRSI is mounted in a frame that is made from Alluset and it is important to identify all the pieces that are needed to construct the frame. There are also parts that are needed for the CIRSI dewar handling trolley or cradle. Unless there are problems with the dewar there should be no need to use this handling cradle and therefore no need to build it up. The construction of the CIRSI frame is as follows. The large round plate attaches directly to the mounting ring at the prime focus of the INT using the outer-most circle of holes. On the WHT the inner-most circle of holes on this large round plate is used. There are four approximately triangular spacing pieces which are bolted onto one side of the round plate and which in turn have the rectangular plate mounted on them. The first thing to do with the round plate is to attach these triangular sections directly of the rear face (away from the telescope mount) mounting plate.
All the Alluset mounting sections should be identified and carefully laid out. Two sections with five holes that are square and two that also have five holes and are twice the thickness should be identified. They also have lifting eyes in the top side and wheels in the bottom end. These four sections should be joined together first followed by the vertical sections connecting the other Alluset pieces that have wheels attached.
Once the box is constructed it may be moved over the round plate and the 20 bolts inserted from the rear of the unit and then bolted down carefully onto the main circular plate. It is important to use the correct bolts to attach the Alluset frame to the round plate. The standard thickness Alluset sections use 55 mm stainless-steel bolts while the double thickness pieces use 5 off 105 mm mild steel (black) volts. The correct 105 mm long bolts may be recognized because their ends have been cut down to make 105 mm and so are shiny. There are also bolts in use which are 110 mm long and these should not be used. It is important to check after assembly that no bolts are protruding through to the front face of the round plate because these will cause problems when the unit is mountede on the telescope and may cause the plate not to connect correctly and lie flat on the telescope mounting ring.
The rectangular plate should now be mounted. On one surface is a black foam square. It is to this surface that the CIRSI dewar is attached. The four bolts that are used are 70 mm long stainless-steel 10 mm diameter and they need to be assembled with a round thick washer (of 37.5 mm diameter 10 mm thick) on top of each triangular section plus a pair of curved surface washers, then the metal plate itself, then a second pair of curved surface washers with the bolt connecting them all together. This should be tightened carefully as they will the main load bearing joint involved in connecting the dewar to the telescope. Check that the curved washers are all lying flat and square (they allow the unit to be tilted if any defocus across the field be noticed. We have never seen this but it is essential to get them flat at this stage.)
The next stage is to install the CIRSI dewar into the frame. It is easiest if one of the cross sections (the one that is farthest away from the round plate and at the bottom (wheel side) of the frame) is temporarily removed to give easier access to lower the dewar into the frame. The orientation of the dewar is that the motor drive shaft for the filter wheel will be at the bottom (on the wheel side of the plate). Any other structures that are bolted to be back of the main dewar front section (such as the multiplexer box) need to the removed before it is installed into the Alluset frame.
The CIRSI dewar is extremely heavy and it is quite unsafe to attempt to move the dewar without proper lifting equipment. At the INT there is a small collapsible crane just like the one that the Instrumentation Group has in Cambridge. This should be used to lift CIRSI out of its packing case and to put it into the frame. Provided that everything else has been removed from the packing case it is quite practical to lift the dewar about 30 cm from the base of the packing case, tip the packing case on one side and slide it out sideways. It should be lowered carefully into the Alluset frame so that the bolts may be installed loosely and then the dewar lowered gently into place. It can be difficult to arrange the arm of crane to be long enough to lift the dewar vertically. In may then be necessary to lift the CIRSI case and support it on (e.g.) foam panels so that the feet of the crane may be slid into place.
The next stage involves installing the computer, camera controller, multiplexer box, and vacuum gauge inside the frame. The computer goes at the top of the frame, nearest to the front plates with its front panel to the right when viewed from the rear of the assembly. It is attached to two horizontal bars by a pair of brackets on each side. This means that an additional horizontal bar has to be install running from front to back at the top of the frame. This bar is marked as bar L. Its exact position needs to be adjusted to match the brackets attached to the host computer.
The camera controller is also mounted between two horizontal bars. One goes from the back of the bottom left-hand side of the frame viewed from the rear and the second one parallel to it half way up the left-hand side. This places the controller very close to the side of the dewar. It is mounted with two horizontal aluminium bars which are bolted onto the eight M3 holes in the base of the camera controller. Take care not to use M3 bolts that are unnecessarily long as these could protrude into the controller and damage electronic parts within it. The vacuum gauge is mounted between the computer and the back of the frame at the top. It is held in place with a single horizontal line of three Alluset bolts.
The camera multiplexer box is bolted onto the rear face of the dewar between the two 55 way connectors for chips themselves. They are held in place by two M8 bolts. It is usually necessary to install several washers to give the correct bolt length. Cable up the system as follows: Connect the two cables that go from the 55 way connectors to the multiplexer box by carefully inserted the 37 way D-connectors in the correct position. Looking at the front of the multiplexer box with the blue connector at the top, detector 1 is top right, detector 2 is bottom right, detector 3 is top left and detector 4 is bottom left.
WARNING: PROCEED NOW WITH GREAT CARE
Connect the four 25-way standard D-connectors first and then connect the pair of 55 way connectors to the chip sockets with great care. This must be done to minimise the risk of static damage to the HAWAII detector chips which are completely unprotected from these connectors. Ensure that you are either connected to the dewar with an anti-electrostatic wrist strap or ensure that you are touching directly at all times the metal work of the dewar. Touch the shell of each 55-way connector against the shorting cap which covers each connector on the side of the dewar body. Then remove the shorting cap and attach the connector immediately. There is a locating series of detents that need to be matched. Twist clockwise until it latches. Do not overtighten or twist any further.
Then connect to the OS/DOS cable between the multiplexer and the controller, taking care to match the labels marked on both. Connect the short cable with 60 way insulation displacement connectors at each end, taking care not stress the connectors and the contacts on it. These connectors are not really strong enough for this kind of application so do take care.
The controller is connected to the computer by two cables. One uses SCSI-like connectors for the PCI data cable and the other conventional D-connectors for the AT-Link cable. Attach these now. They connect to interface cards that are at the extreme right of the rear pane; of the camera control computer.
Connect the temperature monitoring unit with all the appropriate thermocouples installed (in the correct order: they are numbered) and connect the filter wheel monitor cable to the socket on the small filter wheel monitor box which should be positioned near the filter wheel mechanism for ease of access.
The vacuum gauge should also be connected although there is no need to have this monitored by the computer unless you are having trouble with the vacuum. It is a good idea to check and record in the CIRSI Day Book the vacuum reading from time to time to make sure that there is no sign of the vacuum degrading. You can also start to see this if there is any increase in the operating temperature of the detectors. It takes a couple of minutes for the reading of the vacuum gauge to stabilise after the "HV" button on its front panel is pressed, and the gauge comes on automatically. There is some evidence of interference of the vacuum gauge with the HAWAII detector controller so switch this unit off when not in use.
The thermocouples are connected as follows:
1. Liquid nitrogen cylinder
2. Getter (the absorption pump inside the dewar)
3. Sub-plate. The plate that the detectors are mounted on and is the main structural plate at the bottom if the assembly.
4. Solid copper heat strap near chip box
5. Detector chip box
6. Filter box, underside. Should give a good idea of filter temperatures. The filter box is connected only poorly to the cold surfaces.
7. This is disconnected and therefore measures ambient temperature approximately.
Prepared by cdm@ast.cam.ac.uk Please contact with comments, etc. Last updated 22 May 2001.