Closing and pumping
Logfile of openings.
- Print a copy of this checklist and check off each item as it is
- 24 hours in advance, dismount the getter from NOTCam
(three wing nuts) and remove the
lid (three hex screws). Place the getter with the charcoal
(but not the lid) into the oven in the cleanroom and set the
temperature dial to 140C and switch it on. let the getter and
charcoal bake for least 24 hours.
- Find all the tools you will need.
- Set of Allen (hex) keys
- 10mm spanner
- Nitrile gloves
- Check the vacuum pump is ready in the electronics lab. and you
have the digital pressure display unit for the pump.
- To protect the detector against static connect the provided earth wire
to the instrument and the other end (if not already) to a mains earth
pin. It is also good to leave the power cable for the instrument connected
to the mains though make sure the array controller is off.
- Make sure that all wheels and internal parts are assembled correctly.
Check all covers are firmly fastened. Make sure there are no screws
of unknown origin kicking around. Note that all screws must be used
when putting on the lid of the aperture unit.
- Ensure that all wires and connectors are properly connected.
- Visually inspect for broken wires.
- Use the high quality vacuum cleaner to remove possible dust.
- Test that all wheels initialise without problems. Connect the
Ethernet cable and power on the motor controller. From a computer
e.g. cassandra, log on to selena as user 'obs' e.g. ssh -X obs@selena,
cd notcam and run the command notcam-interface to
start the UIF and check one wheel at a time.
- Check that the readings of the temperature and pressure sensor are
- Turn off the oven and remove the getter using the gloves provided.
Screw the lid on and then mount the getter in the instrument.
- Put on the nitrile gloves and the anti-static wrist straps, you
should not touch any of the internal parts with your bare hands.
- Install the radiation shield. Touch the shield on the anti-static
black mat on the table to ensure it is not got any static charge on
it. Take care with the wires through the small holes. There are two
screws on each side of the shield which should be tightened when
the shield is in place. (Two screws are gone because the thread
on the cold table have been stripped.)
- Check that all wheels initialise again, to ensure no wire has
been broken. One wheel at a time. Check also the temperature
readings, that none of these wires are broken.
- Make sure the large, square O-ring is cleaned with a dry
lens tissus. Clean the underside edge of the top of the vessel
- Raise the table carefully below the instrument lid, and make sure
you don't trap any of the heat shield blanket. Release the lid
from the ceiling, and take the table down again to the position
where it can be secured.
- Mount the baffle:
- Wearing clean nitrile gloves and the anti-static wrist strap
mount the goldplated spherical reflector (8 long screws; don't touch
- Mount the black-painted baffle plate to the front of the spherical
baffle (8 small countersunk screws).
- Slide the the insulation cap over this assembly
- Mount the entrance window (8 large screws)
Ensure that the O-ring is in place on the vessel first (it may still be
stuck there from the last opening). Make sure that the O-ring is
exactly in place. Clean the O-ring with a dry lens tissus. Clean
the inside surface of the entrance window housing which contacts
the o-ring with alcohol. Do not tighten the screw now, wait to you start
pumping to allow the vacuum to suck the window on uniformly, then tighten.
- Move NOTCam from the clean room to the electronics room, connect
the mains to the instrument and plug in the motor controller.
- Plug in the vacuum pump to no-break mains (red sockets).
- Connect the vacuum pump to the dewar. If you are uncertain about the
pumping procedure, please check
the general pumping instructions. If NOTCam has been opened,
then start the pump then immediately open the pump valve followed
by the vessel valve.
- While the instrument is pumping remount the array controller.
- For remote monitoring of the pressure and temperature:
- Connect the ethernet cable to the serial/ethernet convert. The cable
can be found rolled up down the left side of the large work bench.
- Connect the power supply for the serial/ethernet convert to a no-break
outlet and power on the motor controller.
- Start the temperature monitoring system as instructed on
the monitoring page if not already running.
- You can also monitor the pressure on the motor controller display panel.
Position number 7 shows the pressure in mBar. To read off the display
toggle the two black buttons nearest to the display to browse through
the positions. It should take no more than 1/2 hour to reach 1 mBar,
if the getter or charcoal has been baked, or 3-4 hours if it hasn't.
Note that it usually takes about 10 minutes for the pump to reach
full operating speed.
- When pressure is below 1 mBar, tighten all the nuts (6 on
each side) that hold the lid onto the vessel and the eight
large screws holding the entrance window on. Then put on the
two metal straps holding NOTCam to its frame.
- If you suspect there is a problem with the pressure then make a
leakage test as described under
Leak testing NOTCam.
- Monitor the pressure regularly. If you don't reach 1E-2 mbar within 12
hours, there might be a leakage. We usually reach about 1E-3 mbar
in 48 hours. When the vacuum pressure is below E-2 mbar it is safe
to start cooling.
- It may be desired that we bake the vessel. to do this follow the
instructions on baking.
Data taken from 13 - 24 March & 25 - 1 April, 2008, While NOTCam was in the Service Building
and after damage to the entrance window was identified!
|Pressure During Pumping
|Pressure After Valve Closed