A dedicated home-made controller with embedded PC has been developed to
provide an automatic liquid nitrogen filling system (LN2)
for the Clover detectors. The supply of LN2 is from a 1000 l
dewar (INOX make) which can be periodically (once in 2 days) filled from
a larger dewar (20,000 l), kept outside the beam hall. The distribution
of LN2 is done with a four-column manifold catering to
sixteen detectors of backward array and another two-column manifold
catering to eight detectors of forward array.
Electrically operated cryogenic valves of Jefferson make (1/2″
diameter, normally closed), are employed for controlling the flow of
LN2 to the detectors. These can be operated under software
control by the program linserv working in linux operating
system. The temperatures at the overflow ports of the Clover
detectors and the filling manifolds are measured using platinum
resistance thermometers (PT100) and the valves are closed under
overfill condition. A graphical user interface (named, fill)
enables the user to monitor the filling status of individual
detectors. The detectors are filled automatically twice a day.
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