- Emergency
- Standard
Emergency Cryogenic Procedures
NIRSPEC is cooled continuously by use of Closed-Cycle Refrigeration
(CCR). A compressor unit in the K2 machine room provides pressurized
He gas to two cold heads on-board NIRSPEC. If this system is inoperable
for more than about 15 minutes, then NIRSPEC may require a lengthy 10 day
cooling cycle to become operable again.
- Loss of CCR Cooling: Emergency Procedures
- Loss of CCR Cooling: Vacuum Procedures
- Reading Cryogenic Temperatures
- E-mail CCR alarm
- Loss of CCR Cooling: Emergency Procedures
In the event of CCR shutdown, it is very important to assess the status
of the NIRSPEC main dewar vacuum prior to restarting the CCR compressor
unit.
- Verify CCR shutdown by inspection of unit 3; static pressure
will be high (235-270 PSI), and the green indicator light will be off.
Image of CCR Unit 3.
- Go up to NIRSPEC. Read the Edwards vacuum gauge display.
Gauge 3 (termed Lo-Vac) should be displayed.
Image of Edwards vacuum gauge display
If the vacuum is:
- Less than 1x10e-1, then it is safe to restart
the CCR compressor. Be expeditious; it would be helpful to
have an assistant waiting at the compressor to save valuable time.
- Greater than 1x10e-1, the DO NOT restart the compressor. NIRSPEC
must be vacuum pumped before cooling is restarted. Vacuum pumping
should begin as soon as possible, otherwise NIRSPEC will continue
to warm up and will require a complete cool down cycle. Read on.
- Loss of CCR Cooling: Vacuum Procedure
- Connect the pump to the NIRSPEC vacuum valve fitting.
- Start rough pumping the line. Open the NIRSPEC vacuum
valve as soon as the line is a factor of 10 below the
NIRSPEC vacuum reading.
- When the vacuum reaches 4x10e-2 (40 millitorr), start the
turbo pump. At this time the CCR compressor unit 3 can be restarted.
- Monitor the NIRSPEC vacuum. When it is less than 1x10e-4, valve
off the pump. Verify that the vacuum continues to drop with the CCR
running.
- Reading Cryogenic Temperatures
To read the nirspec cryogenic temperatures, log on to waimea
as "nspeceng" and type "cryotemps". The result is:
[nspeceng@nirspec ~]$ cryotemps
======================================================================
Service = NSDEWAR NIRSPEC Temperatures (K)
======================================================================
Keyword Location Temp
----------------------------------------------------------------------
BENCH1INVAL Bench-1-temp-value 50.411
BENCH2INVAL Bench-2-temp-value 50.084
CCR1050VAL Cold-head-1050-temp-value 45.838
CCR350VAL Cold-head-350-temp-value 16.089
LN2CANVAL LN2-can-temp-value 480.000
OPTPLATEVAL Optical-plate-temp-value 55.658
ROTMOTVAL Rotator-motor-temp-value 56.975
ROTTOPVAL Top-of-rotator-temp-value 75.188
SCAMASICVAL SCAM-ASIC-temp-value 51.134
SCAMFILTVAL SCAM-filter-wheel-temp-value 53.200
SCAMTEMP1VAL SCAM-temp-value 30.001
SCAMTEMP2VAL SCAM-temp-value 29.904
SPECASICVAL SPEC-ASIC-temp-value 60.883
SPECTEMP1VAL SPEC-temp-value 30.000
SPECTEMP2VAL SPEC-temp-value 29.930
TMAVAL Three-mirror-antistigmat-temp-value 57.180
======================================================================
Service = NSDEWAR NIRSPEC Controlled Temperatures (K)
======================================================================
Location HtrMode HtrRng Htr% Target Temp1 Temp2
----------------------------------------------------------------------
Bench1 Closed-loop-PID Low 29.7 50.000 50.409 0.000
Bench2 Closed-loop-PID Low 37.8 50.000 50.409 0.000
SCAM Closed-loop-PID Medium 42.2 30.000 30.001 29.904
SPEC Closed-loop-PID Low 23.3 30.000 30.000 29.931
======================================================================
Note that every sensor reads below liquid nitrogen temperatures (77 K).
- Example of the e-mail alarm message
This message is sent to a group of people including IS's, OA's and
facility staff when Temp 2 above exceeds 15 K. This should be an
indication that the CCR has stopped operating.
********************************************************************
ATTENTION! ATTENTION! URGENT! PLEASE PAY ATTENTION!
********************************************************************
The CCR cooling system for NIRSPEC has apparantly halted. If this
system is not restarted IMMEDIATELY, the instrument will warm up,
which means that it WILL NOT BE USABLE FOR 2 WEEKS!
It is EXTREMELY URGENT to get this system restarted. It may have
halted for the following reasons:
1. The building glycol (not instrument) system has gone down.
2. The CCR controller/compressor has lost power.
3. A leak has developed in the He lines.
********************************************************************
KEEP READING - THIS IS VERY IMPORTANT!
If the CCR compressor has been down for more than 10 minutes, then
NIRSPEC may have lost a good vacuum. Check the vacuum gauge readout
(the grey box with black face/LCD readout located on NIRSPEC's frame
near the floor; labeled "Edwards Pirani").
If the pressure is GREATER than 1 x 10^-1 Torr (100 mT),
DO NOT RESTART CCR UNIT #3 WITHOUT TOM BIDA'S APPROVAL.
********************************************************************
Inspect CCR Unit 3 in the Keck-2 Machine Room AND
Read the NIRSPEC Vacuum RIGHT AWAY!
CALL Dennis McBride (161), and/or Tom Bida (165, 883-9565) ASAP.
Standard Cryogenic Procedures
Planned cryo cycles on NIRSPEC require some coordination between
summit and HQ staff, to ensure that everything gets done in the right
order. The steps below include suggestions as to who can carry them
out most easily, but these are only suggestions. Experience shows
that the whole process is usually smoother when both summit and HQ
staff are involved.
- Procedure for a planned warmup
- Move NIRSPEC into stow if not already there.
- Lock out unwanted activity. (For Instrument Scientist)
Stop all VNC sessions corresponding to numbered accounts. E.g. log into nspec1@nirspec. Then issue the command "kvnc stop servers". Do this for ALL VNC sessions that are up and running. This will prevent random astronomers from
attempting to start the NIRSPEC software or move motors while the
instrument is not at thermal equilibrium. Be sure to make a note of
the new password, so you can reverse the change later! Send an email
to the "instrument" alias to announce that you have done this.
- Procedure for a planned
cooldown
- Pump for as long as practical. (IT) Before cooling down,
pump the dewar for 4-5 days if possible.
- Bake the getters. (IT) Make a note of the vacuum
reading on the pump (and dewar if possible) before beginning this
step. During the first day of pumping, connect a DC power supply to
the banana jacks on the rear module leg (by the vacuum valve) to power
the heaters in the getter material on the cold heads. The heaters are
two 25-ohm resistors wired in parallel adjust the power supply so that
the total DC power supplied to both heaters (voltage times current) is
about 12.5 watts or 6.25 watts per resistor. Make a note of the
vacuum reading on the pump (and dewar if possible) after the heaters
have been on for at least a half-hour.
- Turn off getter heaters. (IT) Run the getter
heaters as described above for only about 24 hours, then continue
pumping.
- Decide when to start CCRs. (IS) This decision will
usually be dictated by the observing schedule. It's best to allow 12
full days of CCR operation before the first science night. Subject to
that constraint, pump the dewar for as long as practical before
starting the CCRs.
- Lock out unwanted activity. (IS) If this has not
already been done as part of the warmup, log on to the HQ workstation
hanauma as user nirspec and change the password
using the unix command yppasswd. This will prevent random
astronomers from attempting to start the NIRSPEC software or move
motors while the instrument is not at thermal equilibrium. Be sure to
make a note of the new password, so you can reverse the change later!
Send an email to the "instrument" alias to announce that you have done
this.
- Configure the software on waimea. (IS)
Log in to the instrument host waimea as user
nirspec and perform the following steps:
- Make sure waimea is healthy. Check the time
since the last reboot with the unix command uptime. If
it's been more than a week, reboot
waimea before proceeding. This will help prevent crashes that
would interrupt temperature logging while NIRSPEC is warming up.
- Get the server running. Check the status of the
server with the unix command ct, and verify that you see
three server processes running. If you see none, start the server
with the command runserver. If there are 1 or 2 processes
running, or if the server won't start normally, see the troubleshooting page for help.
- Start temperature logging. If you had to restart the
server in the previous step, then any cryo logging that was running
before is now dead. Check for any lingering processes with the
command:
Kill any suspended logcryo jobs found. If there is not a working
logcryo job running, start it. In the home directory of
the nirspec account on waimea issue the command:
- logcryo > logs/cryotemps.warmup.[date] &
to start the temperature logging process. This will record the
temperatures on all the dewar sensors, every five minutes, in the file
you just created. For the [date] part of the filename, use
some identifier that will include the day, month and year such as
23jul01.
- Turn up the Aladdin detector temperature setpoint.
To protect the Aladdin detector from condensation, it must not ever be
the coldest point in the system. The normal temperature setpoint is
30 Kelvin. Set it up to 300K with the following command:
- m change.detector.temp=300
The detector block heaters do not have enough power to take it to
300K, but setting the temperature to 300 will run the heaters flat
out, which will keep the Aladdin about 10-15 degrees K warmer than the
rest of the system.
- Touch base. (IS) Contact the summit Instrument
Technician on duty to confirm that all the steps above have been
completed, and that NIRSPEC is ready for cooling down.
- Check the vacuum. (IT) Turn
on the Varian SenTorr vacuum gauge controller, and after it stabilizes make a
note of the vacuum reading on the "high vacuum" channel.
Also note the vacuum reading on the pump. Touch base with the
responsible Instrument Scientist to confirm that the vacuum is good
enough to restart CCR cooling.
- Stop pumping. (IT) Close the dewar vacuum valve,
and turn off the pump.
- Start the CCRs. (IT) In the Keck 2 mechanical room,
switch on the CCR compressor No. 3 that serves NIRSPEC. Immediately
advise the responsible Instrument Scientist as to the time the CCRs
were turned on, and as to the vacuum reading on the Varian SenTorr gauge
controller before and after.
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