-
Red warning flag on PMAS Status Window for either SPEC LN2 or AG LN2.
-
The PMAS instrument control software monitors the reading of two
flow meters, which measure the evaporation rate of the SPEC and AG
cryostat, respectively.
-
These readings are recorded numerically on the PMAS Status Window.
When a current reading falls beyond an upper or lower limit, a
warning is issued.
-
Note: when the telescope is slewing over large angles, it is normal
that liquid nitrogen is stirred up to produce temporarily high
flow rates.
-
First check whether the two flow meters mounted next to the cryostat
show the same flow rates as recorded on the status window. If so,
an excessive evaporation rate indicates loss of insulation, cold
bridges, or loss of vakuum. Call staff to solve the problem.
-
LN2 rates which fall below the lower margin indicate that the
LN2 supply has been consumed. Call support to refill cryostat
immediately.
-
NOTE: the cryostats have cooling timescales of many hours. It is
not advisable to risk warming up to even a few degrees - it may
jeopardize the rest of an observing night.
|
|
|