Speaker
Description
Monochromatic neutron beams are essential for most neutron scattering experiments and can be produced using crystal monochromators, the time-of-flight (ToF) method, or neutron velocity selectors (NVS). While crystal monochromators and ToF techniques provide superior wavelength resolution, neutron velocity selectors offer high neutron transmission and widely variable wavelength range, making them indispensable for many neutron instruments, especially in the long wavelength range, where Bragg-crystals are limited.
A neutron velocity selector consists of a rotating drum with helical slits coated with a neutron-absorbing material, typically Boron-10 or Gadolinium. The helical geometry transmits only neutrons within a selected velocity range while absorbing neutrons of other velocities.
Mirrotron Ltd’s original mechanical neutron velocity selectors were first developed at the KFKI research centre (now Budapest Neutron Centre). The first multidisc (MDR) design, patented in 1988, represented a major breakthrough by replacing conventional heavy drum selectors with a lightweight multidisc structure, enabling significantly improved performance. Following a technology transfer in 1992, Mirrotron began manufacturing and distributing these selectors. In the past 30 years several improvements of the parameters and various technical solutions have been made.
Between 2022 and 2024, Mirrotron completed a comprehensive major redesign of both the mechanical and electrical systems. The development required overcoming several manufacturing challenges, implementation of modern manufacturing technologies, optimization of assembly procedures, and the qualification of a reliable Boron-10 coating process.
The upgraded design delivers a wider selectable neutron wavelength range through an increased maximum rotation speed, reduced maintenance requirements with keeping the long operational lifetime.
This presentation reviews the history of this unique device and compares its original and upgraded designs. It discusses the motivation for the redesign, the principal engineering and manufacturing challenges encountered during development, the implemented design solutions, and the performance of the upgraded neutron velocity selector.
Key Words
Neutron Velocity Selector