Kermit Hardware Setup


[ Dewar Internals | Dewar | Cryocooler | Temperature Monitor | Motors | Cabling | Power-Up | Disassembly ]


Dewar Internals

To be written:

Dewar

Carefully put the inner shield lid back in place and tighten all the screws. With the grooved (inside) side of the dewar lid facing up, carefully clean the groove using isopropyl, making sure to remove any debris to ensure a good seal. Apply vacuum grease to the O-ring and place it in the groove. Dab some extra vacuum grease onto the corners of the O-ring to tack it in place in the groove.

It takes two people to comfortably lift the lid and place it onto the dewar. Make sure to orient it correctly: the side with the black foot should be above the other black feet on the dewar. Be very careful as you do this, as the O-ring has a tendency to fall out of the groove. If you try to tighten it with an improperly positioned O-ring, the dewar won't seal and you potentially could break the O-ring if it gets pinched. Make sure the O-ring is in the groove, and that the dewar lid is sitting smooth and level on top of the dewar before trying to tighten any of the screws.

To pump the dewar down, use the UH Varian Turbopump. Kermit has a 2" vacuum attachment, while the pump has a 3"; the appropriate adapter hose can usually be found in the UH "Vacuum parts" box in the black cabinet in AEOS Room 3. Once the vacuum pump is attached, just press the "Start" button to begin pumping. Note that the Start button doesn't look at all like a button: it's perfectly flush and looks just like a sticker, so don't be fooled. The turbopump should spin up to about 56 krpm within a few minutes. If it doesn't then you've got a bad seal and need to check the O-ring again. Also, there is a silver thumbscrew on the side of the vacuum pump; this is the purge valve. Make sure it's closed all the way or the pump won't spin up. Finally, make sure that the "Low speed" button right next to the start button is not pressed.

It takes about twelve hours to pump down Kermit with this pump. You may monitor the progress using the vacuum gauge built in to the Varian pump, or better yet the vacuum gauge mounted on Kermit itself. This is a Granville-Phillips series 354, which must be powered using a DC power supply and adapter cable (see picture). It wants 24 V DC, 12 W max, and is protected against reversal and overvoltage. The gauge will automatically turn itself off if the pressure is above 5e-2 Torr. To turn it back on, press the reset switch on the adapter cable.


Cryocooler and Compressor

Kermit is cooled by a CTI Crygenics model 1050 closed-cycle cold head. The compressor for this cold head requires 220 V 3-phase AC power from a five-pin socket.

The hoses should always be stored with the end-caps on to keep them clean; remove the end caps, screw the two end caps together, and store them in the small plastic case labelled "Kermit Cryo Tools". When connecting the cryocooler hoses to the dewar, first apply a drop or two of isopropyl alcohol to the rotating flange on the hose end. Also use a kimwipe to gently clean the ends of the hoses.

They are labelled "Supply" and "Return", matching the connectors on the compressor and cold head. The hoses can be connected in either order. Be very careful to connect the hoses properly! There are wrenches in the "Kermit Cryo Tools" box in two different sizes: one for screwing the flange into place, and the other for holding the cable still so it does not twist while you screw the flange into place.

When connecting the hoses, please make sure to keep the hose end-caps somewhere they can be found when next needed (I suggest the "cryo pump tools and caps" drawer in AEOS Room 3). Similarly, when disconnecting the hoses, make sure to find and replace the caps on both hoses.

Always turn the compressor on first, then the cold head. To shut off, do the reverse.


Temperature Monitor

A Lakeshore model 331 temperature controller is used to monitor and regulate the detector temperature. This should be connected before starting cooldown so you can monitor the cooling progress. Just connect the cable from the Lakeshore to P6 on Kermit, and plug the Lakeshore in to wall power. The Lakeshore has two temperature readouts: A is at the detector heater and B is at the cold plate.

After you have turned on the Lakeshore, press the Heater Range button until the range is High, then press Enter. This activates the heater resistor used to regulate the detector temperature.

A long white serial cable connects the Lakeshore temperature monitor to the Kermit computer sauron. Connect the cable to the serial port on the Lakeshore and to the serial port B on the back of sauron


Motor Controller

The Galil motor controller communicates with sauron over ethernet. It cannot do DHCP, so you have to set the address manually. The procedure for changing the IP address is as follows:
  1. Connect a serial cable from some computer's serial port to the "main port" on the Galil (not the "aux port", mind you!).
  2. Connect over this serial line using the terminal program of your choice. Try tip on Solaris, or use the TCL program serialout.tcl on Linux. The serial settings are 19200, n, 8, 1.
  3. Type
    IA aaa,bbb,ccc,ddd
    BN
    
    Note that the IP address must be separated by commas, not periods! The first command sets the new internet address, while the second one burns it into flash memory for storage when powered off.
  4. On sauron, edit the file ~/kermit.conf so that the set motorcontroller_ip line reflects the new IP address.

Cabling

The cabling for Kermit should be set up according to this diagram.

All connections to the dewar are using custom cables with hermetic connectors fabricated by UH/UCB. I'll eventually link from here to the wiring diagrams for said cables.

The fiber optic cable specification is, quoting the ARC system documentation: AT&T ST type connectors, 62.5/125 micron multimode Ge-doped silica core fiber cable. See for instance here

The Ethernet links are stock 100base-T cables.

For the computer, balrog, to set it up in dual-monitor mode:


Grounding

THIS IS REALLY IMPORTANT, SO PAY ATTENTION HERE, FOLKS. Unless you get things properly grounded, you're going to get lots of read noise and otherwise messed up frames.

In the event that Kermit is not behaving properly, check that these ground connections are made firmly.

The Leach electronics box generates a fair amount of heat. It is designed to run using water cooling through a heat exchanger to keep the cards cool, and we will try to do it this way during the March run. On the other hand, it's been used with just air cooling (case open, external fan blowing air through) successfully, though it does get a bit warmer than we might want that way.


Initial Power-up

The control computer sauron should be turned on first, but the Kermit software does not need to be running yet.

Turn on the Leach electronics box. There are green LEDs next to the fiber optic receivers inside the electronics box and computer (the one on the back of the computer is easiest to see). If the green light turns on, you have a functional fiber optic comm link and can proceed. If the green light does not turn on, the fiber optic is mis-cabled. Swap the two connectors on one end of the cable. The green light should now be on.

Turn on the Galil motor controller and the motor drivers.

You should now be ready to start the software.


Disassembly

Follow these steps to disassemble Kermit at the end of the run.
  1. Turn off the cold head and compressor. Disconnect the power cable from the cold head. Using the wrenches from the Kermit Cryo Tools box, disconnect the helium hoses from the cold head and compressor. Immediately screw the end-caps from the Cryo Tools box onto both ends of the cables and the attachment points on the cold head and compressor. It's very important to keep the O-rings on the cable ends from getting contaminated with dirt.
  2. Turn off the temperature controller. Disconnect the temperature monitor cable from the dewar and the Lakeshore temperature controller. Disconnect the serial cable from the Lakeshore controller and Kermmit computer.
  3. Turn off the motor controller. There's a switch for the motor driver power, but the Galil motor controller can only be turned off by unplugging it. Disconnect the motor limit switch cable from the dewar. Disconnect the motor power cables from the motor controller; you can't disconnect them from the dewar so just coil them up nicely.
  4. READ THIS CAREFULLY! READ IT THROUGH ENTIRELY BEFORE PROCEEDING! Disconnecting the readout cables from the detector is a very delicate operation. The detector is an extremely expensive static-sensitive device, and if it gets cooked we're utterly screwed. DO NOT FRY THE DETECTOR. In order to not fry the detector, follow this proceedure precisely:
    1. Get a grounding strap. Ground yourself to the dewar. The easiest way to do this is to attach the grounding strap to one of the bolts holding the dewar together. Unscrew the bolt, attach the grounding strap, then screw the bolt back in. Wear the grounding strap throughout the following.
    2. Now again ground yourself to the dewar by briefly touching one of the bolts. Bear in mind that the green and black anodyzed surfaces are NOT conductive, so make sure to touch one of the steel bolts directly.
    3. While touching a dewar bolt with one hand, with the other hand touch the optical table, and then the Kermit readout electronic box. This will dissipate any static electricity which may be present between these objects.
    4. Now carefully unscrew one of the readout cables from the dewar. Immediately cover over the exposed dewar connector with aluminum foil. Tape the foil in place so it doesn't fall off. I'm getting real grounding plugs fabricated but for now this will have to do.
    5. Repeat for the other two cables.
    That's the delicate part of the proceedure. Once that's completed you may disconnect the other ends of the cables from the Leach box and then disconnect the Leach box from power at your leisure. Ideally, once you have moved Kermit to its storage location in Room 3, you will reconnect the Leach cables (with a similar degree of grounding caution!) to keep the detector voltages tied to ground when the system is in storage.
  5. Disconnect the fiber optic cable from the Leach box and from sauron. Coil it up carefully and loosely - it's a fiber optic and is thus fragile and subject to minimum radius of curvature restrictions. Don't try to coil it in a circle any tighter than about a foot or so.
  6. If necessary, move the dewar away from the coronagraph to have adequate clearance around it. Attach the dewar window cover in front of the window. If necessary, replace the tape so it sticks well. Re-attach the two front handles for Kermit which were removed for clearance reasons.
  7. Carefully lift the camera from the table to the ground. It weighs about 250 pounds, so be sure to have adequate lifting power. The black handles on the dewar and the black legs are all acceptable lifting points.
  8. If sauron is to be set up on a different IP address, before shutting it down follow the proceedure to change its IP address. If done before moving the machine, then it will boot properly onto the new network and may be accessed by ssh when it has no monitor.
    This page last updated by Marshall Perrin on 2004 March 04