Grenoble, France
For the past three years, ILL has modified its polarised 3He filling station and obtained very impressive results: the maximum polarisation has raised from 75 to 83% and the production rate has doubled, reaching 30 bar.l/day. In the meantime, FRM-II has acquired a filling station showing almost identical performance. HMI has almost finished the construction of its own MEOP filling station and ISIS has greatly improved its SEOP station, the maximum polarisation moving from 32 to 70%.
After many investigations at all facilities and some fruitful discussions with colleagues from the USA, we have finally adopted a reliable recipe leading to the production of containers with long relaxation times (200 to 450 hours). Some work has also been done to build large containers that can efficiently be used in front of large neutron detectors. This success opens the door to the application of 3He spin analyser at new neutron sources.
We have also designed, constructed and tested a chamber made of µ-metal and permanent magnets for hosting NSF cells maintaining the 3He polarisation on neutron beams. It can screen low environmental magnetic fields, protects the users from accidental explosion of the container, does not require the use of a battery during transport and maintains the polarisation efficiently. By adding a solenoid producing an oscillating radiofrequency magnetic field, the chamber can also flip the polarisation of the 3He nuclei and therefore selects the polarisation state of the neutron beam. With such a device, the NSF is becoming a very practical device that is going to be widely used at many neutron facilities.
To summarise, the project which will end at the end of this year, has been very efficient but a number of deliverables remain to be delivered: a prototype double cell for SEOP, a SEOP valve-sealed cell with long relaxation time, a SEOP system to polarise 3He continuously, the study of a compact continuous gas-flow MEOP system, and a magneto-static cavity for high-field environment. These items have been discussed during this seventh meeting held in Grenoble. The minutes can be downloaded here.
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Supported by the EU through FP5 and FP6