Figure 9:
Control GUI for the LN2 Autofill Sequencer.
Liquid nitrogen is provided to the LN2 heat shield from the
Hall C cryogenics through a vacuum insulated hose.
The hose splits at the cryostat end, leading to two
cryogenic-rated solenoid valves.
The first SV91110, or ``CoolDown Valve'', vents
the incoming nitrogen to atmosphere, while the second,
SV91111, supplies nitrogen to the cryostat.
When the sequencer is ENABLED, the operation is as follows.
When the LN2 level falls below MIN, the CoolDown
Valve opens, permitting nitrogen to flow through the
hose. This precools the hose, as came be seen by monitoring
a silicon diode thermometer, TD91110, installed near the
junction between the two valves. When the Set pt.
temperature is achieved, the CoolDown valve closes and
the Fill Valve opens. When the MAX LN2 level is
reached, the Fill Valve closes. The current status
of the LN2 sequencer is displayed at the top of the control
screen.
The LN2 jacket can be filled at any time by
operating the CoolDown and Fill solenoids manually.
