Speaker
Description
An important area of fundamental research with neutrons is the investigation of magnetic materials. Spherical neutron polarimetry (SPN) can be used. For this, a spin-polarized neutron beam is used, which hits the sample and the scattered intensity is then measured with detectors. In order to adiabatically rotate the polarity of the neutron beam in the required direction, a rotatable magnetic field is required, one possibility being a so-called nutator. With this device, the transverse magnetic directions of the neutron beam are guided and can be turned with a set angle.
For POLI (Polarized Hot Neutron Diffractometer), an instrument of Forschungszentrum Jülich, a new Nutator design has been developed and manufactured by Institute of Technology and Engineering (ITE) of Forschungszentrum Jülich GmbH, to be compatible with the new in-situ SEOP polarizer setup. The new nutators are based on so-called Halbach-rings consisting of different NdFeB magnets. With those permanent magnets, electromagnetic coils are no longer necessary. The arrangement and selection of the permanent magnets is based on magnetic simulations carried out by the ITE.
The Nutators consist of a total of 20 rings, made up of 3 different magnetic configurations. Two of the configurations are rotated, while the third remains fixed. In addition, there is an option to adapt further magnetic rings on each side. These additional rings stabilize the polarized beam at the entrance and exit, so the nutators are adjustable for each requirement. In the previous nutator prototype, the Halbach-rings rotated simultaneously with an angular offset, which required a gearbox. This is no longer necessary with the new magnet configuration. Here, multiple rings could be grouped into two ring assemblies, in addition some magnetic rings can be fixed.
As a result, only two rotary tables were needed as a less complex but effective drive. For this, rotary tables of the company standa where used, which have the demanded accuracy of 0.1 degree. The ring housings are printed by FDM (fuses deposition Modeling) and is made of PETG. The position of the nutator is adjustable in all directions, in the plane with screws, in the height over adjustable machine-foots.
Polarized Neutrons, Nutators, Halbach Magnets, Spin Manipulation, SEOP, FDM
Submitting Author: a.nyc@fz-juelich.de
Key Words
Polarized Neutrons, Nutators, Halbach Magnets, Spin Manipulation, SEOP, FDM