Beryllium filter

The ultra-compact beryllium filter is cooled down with a 2.7 W @ 80 K cryocooler from Thales Cryogenics which requires a water cooling line. The vessel of the cryostat is pumped dynamically and the cryostat is translated into the neutron beam when needed. A logic process controller (Schneider M251) monitors the water flow rate and temperature, the pressure in the vacuum vessel, the temperature of the Thales microprocesor and the temperature of the beryllium filter.

The graphical user interface of the humain machine interface (Schenider HMI GTO 4310) proposes 4 screens selected from a tab bar:

• Temperature evolution of the beryllium block
• Temperature evolution of the Thales electronics
• Synoptic of the cryostat displaying all parameters
• Logs of all actions and errors since the beginning of its use

At the top of the screens, indicators are permanently displayed to report potential alarms and defaults. Data are collected and stored in a flash memory. The cooling of the filter is automatic.

The setpoint is fixed to 80 K. A reduction of the water cooling flow-rate raises an alarm for a minute (flow-rate < 2 L/min). The controller waits for a recovery of the water cooling line and stops the cooler if the alarm remains active more than a minute. The pressure in the vacuum vessel of the cryostat must be lower than 1e-4 mbar. If it increases, the controller raises an alarm which becomes a default when it measures 5e-4 mbar. Similairly, the temperature of the cooler drive electronics is monitored and should not exceed the room temperature + 20 °C.