1. Report from meeting Hydrogen system operation from cryocooler and level control Cryocoolers for MICE Tom Bradshaw Elwyn Baynham Yury Ivanyushenkov Rutherford Appleton Laboratory Wing Lau Mike Green Oxford

2. Introduction The costs associated with the provision of conventional refrigeration plant are high ~ £1.5M We have investigated ways of bringing these costs down :  Refurbish existing cryogenic plant  Closed cycle refrigeration - cryocoolers  Use a hybrid system – cryocoolers + conventional

3. H2 system Mike Green described his proposal to operate the H2 absorbers from a cryocooler This uses a cryocooler in a recondensing and thermosyphon mode The absorber volume is connected to a recondensing pot in a separate turret by 2 pipes – the existing pipe from the top of the absorber and an additional one from the bottom of the absorber – this forms a thermosyphon loop The cryocooler cold head is attached to a recondenser in the pot – the pot effectively controls the H2 level and allows the expansion of H2 with temperature rise It was agreed to take this proposal forward Wing to incorporate this proposal firstly into the 2d model to assess space,pipe runs turret etc RAL to assess heat loads and the operation of this system with the hydride bed RAL/OX to assess the cooler options RAL to assess the infrastructure for the cooldown from 300K – additional LN2 and He supplies and the mode of connection

4. Cryocoolers for MICE Mike Green proposal to operate magnets from cryocooler This is similar to the H2 system in concept ie recondenser with thermosyphon Note it also needs the additional cooling loop for cooldown Wing to implement this design in the 2d model for the absorber focus coils Mike to send his heat load audits to RAL RAL to look again at thermal modelling of complete system RAL/OX to continue assessment of available cryocoolers and their compatibility with MICE reqts RAL to consider control requirements for cryocoolers

5. Absorber Cooling with a Small Cooler