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The ILL has firmly established itself as a pioneer in neutron science and technology. Neutron beams are used to carry out frontier research in diverse fields.

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Neutron technology at ILL


We have developed flippers, based on adiabatic fast passage (AFP), which can flip the neutron spin or the 3He spin inside the spin-filter cell.

Neutron Flippers

Neutron flippers are attractive to use, as there is no material in the beam, they provide a very high flipping efficiency (>99%) and they cover the full range of neutron wavelengths from hot to ultra-cold neutrons.


3He Flippers

The 3He spin-filter with an AFP 3He flipper acts as a combined polariser and flipper. It works by reversing the polarisation direction of the 3He gas relative to the guide field and thus provides a neutron flipping efficiency of 100% by definition, which is completely independent of neutron wavelength. The main technical challenge consists in keeping the depolarisation of the 3He gas to a minimum when the flipping takes place. We are now able to flip the 3He gas inside a standard “magic box” with a loss of polarisation of about 10-5 per flip. If the flipper is activated once a minute, this depolarisation corresponds to an additional “relaxation time” of 1700 hours – negligible within the time frame of an experiment.

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