High intensity specular reflectometry - first experiments

TL;DR

This paper introduces a new high-intensity specular reflectometry method using a convergent beam and a position-sensitive detector, achieving significant intensity gains for screening wide parameter ranges in neutron scattering experiments.

Contribution

The paper presents the first implementation and experimental validation of Selene, a novel high-intensity reflectometry scheme utilizing an elliptically focusing guide for neutron scattering.

Findings

Achieved a tenfold intensity gain in initial experiments.

Confirmed the general concept and operation modes of the new setup.

Expected a twenty-fivefold gain with improved guide alignment.

Abstract

Selene is the attempt to implement a new scheme for high-intensity specular reflectometry. Instead of a highly collimated beam one uses a convergent beam covering a large angular range. The angular resolution is then performed by a position-sensitive detector. Off-specular scattering in this set-up leads to some background, but for screening of wide parameter ranges (e.g. temperature, electric and magnetic fields) the intensity gain of at least one order of magnitude is essential. If necessary, the high precession measurements (even with off-specular components) then are performed with the conventional set-up. The heart of this new set-up is an elliptically focusing guide element of 2\,m length. Though this guide is optimised for the use on the TOF reflectometer Amor at SINQ, it can be used as stand-alone device to check the possible application also for other neutron scattering techniques. The first measurements on AMOR confirmed the general concept and the various operation modes. A draw-back occurred due to problems with the internal alignment of the guide. Nevertheless in the TOF mode a gain factor of 10 was reached, and a factor 25 can be expected for an improved guide.