Development of low temperature solid state detectors for ultra-cold neutrons within superfluid He-4

摘要

As part of an R&D programme for the development of a next-generation experiment to measure the neutron electric dipole moment, in which ultra-cold neutrons (UCN) are produced and stored in superfluid He-4 (superthermal source), we have developed cryogenic detectors of UCN that can operate in situ within the superfluid. Surface barrier detectors and PIN diode detectors have been tested and proven to work well at temperatures as low as 80 mK. When combined with a layer of (LiF)-Li-6 which converts neutrons to charged particles, these detectors form a reliable UCN detection system which has been tested in liquid helium down to 430 mK. The detectors have operated within superfluid helium for periods of up to 30 days with no signs of degradation. The development of this detection system has enabled us to measure the flux of UCN from a superthermal UCN source with no intervening transmission windows which can attenuate the flux. The addition of thin films of magnetically aligned iron also enables these detectors to be used in situ for neutron spin-polarisation analysis. (C) 2003 Elsevier Science B.V. All rights reserved. [References: 11]