Abstract
We report the design of the beam-transport system (especially the vertical geometry) for a cold-neutron disk-chopper spectrometer AMATERAS at J-PARC. Based on the elliptical shape, which is one of the most effective geometries for a ballistic mirror, the design was optimized to obtain, at the sample position, a neutron beam with high flux without serious degrading in divergence and spacial homogeneity within the boundary conditions required from actual spectrometer construction. The optimum focal point was examined. An ideal elliptical shape was modified to reduce its height without serious loss of transmission. The final result was adapted to the construction requirements of AMATERAS. Although the ideas studied in this paper are considered for the AMATERAS case, they can be useful also to other spectrometers in similar situations.
Highlights
Recent progress in fabricating high-quality supermirrors has changed spectrometer design
In our previous study [7], we examined the elliptical shape for AMATERAS and found that it offered significant advantages
Based on our previous conceptual study [7], we developed a practical design for the vertical geometry of the beam-transport system of AMATERAS
Summary
Recent progress in fabricating high-quality supermirrors has changed spectrometer design. The spectrometer is dedicated to inelastic and quasi-elastic neutron scattering from cold to subthermal energies As expected for this type of instrument, high intensity and low background are critical to the performance of the spectrometer. We developed the actual design of the vertical beam-transport geometry and simultaneously started construction of the spectrometer. Because the longer slits make a disk fragile, reducing the disk-slit heights is critical for the AMATERAS high-speed choppers. This criterion limits the beam height in the transport section. We used Monte Carlo simulations to optimize the beam-transport design, especially with regard to the vertical geometry. For the given boundary conditions, the mirror shape was optimized to maximize beam-transport performance
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
