Correction elements for ultra-high resolution NSE spectrometer

Abstract

Neutron spin-echo (NSE) spectrometers are the neutron scattering instruments with the highest available effective energy resolution. Their primary signal corresponds to the intermediate scattering function S( Q,τ) with τ as the Fourier time. The Fourier time depends on the field integral J=∫ IBI d l and the cube of the wavelength. The homogeneity of the field integrals for different neutron paths is hardly better than 10 −3. For higher field integrals up to J = 1 Tm this homogeneity is not sufficient and additional correction elements that realise certain radial current distributions in the beam cross section are required. The requirements imposed by increased field integrals and larger beam cross section and divergences have to be met. The challenges are to combine high precision, good neutron transparency and current carrying capability. For next generation NSE instruments correction elements are to be developed with current carrying capability beyond 100 A/mm-radius with appropriate cooling. Neutron transmission is optimised by an all-aluminium design. The shape and the influence of current connection has been customised and analysed by comprehensive computer modelling. Here we report on the progress of this research and development work, which is also essential for the ultra-high resolution NSE spectrometer for the SNS.