Abstract
The use of polarized protons as a broad-band neutron spin filter is an attractive alternative to the well-established neutron polarization techniques, namely polarized 3He gas and super mirrors, since the spin-dependent neutron proton scattering cross-section is large in a broad wavelength range. We have developed a novel neutron spin filter where we create the necessary large proton polarization in a solid with a recent method of dynamic nuclear polarization (DNP) that uses photo-excited triplet states. This requires only moderate experimental means and allows a compact design. In order to quantify the efficiency of the spin filter, we have measured the relevant spin-dependent and spin-independent terms of the neutron scattering cross-section of a naphthalene single crystal. The data allows to estimate the triplet spin filter performance over a broad wavelength range. With the recently achieved proton polarization of 80% the triplet filter compares well with a state of the art 3He filter.
Highlights
Polarized neutrons are widely used in fundamental physics studies as well as for material investigations in neutron scattering science and the main polarization techniques, super mirrors and 3He filters have constantly been further developed with considerable effort
We demonstrated that using short lived photo-excited triplet states instead of stable radicals for dynamic nuclear polarization (DNP) [3], the necessary high proton polarization can be reached in a naphthalene single crystal with only moderate experimental means, i.e at a magnetic field of ∼ 0.4 T and a temperature between 25 and 100 K [4]
We present a complete set of neutron proton cross-sections that allows us to quantify the efficiency of the triplet spin filter over the whole neutron energy range
Summary
Polarized neutrons are widely used in fundamental physics studies as well as for material investigations in neutron scattering science and the main polarization techniques, super mirrors and 3He filters have constantly been further developed with considerable effort. For thermal or even epithermal neutrons, which are of interest for fundamental physics studies, such as the proposed T-violation search [7], an efficient 3He spin filter would need dimensions and a pressure at the limits of current techniques [8, 9]. In order to better quantify the performance of our triplet spin filter, a sound data set for the relevant neutron proton cross-sections in naphthalene as function of the wavelength is needed. First measurements of the polarization dependent cross section have been presented in [10], while in this note we report on experiments that extend the data set, which is used to asses the efficiency of the spin filtering process
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