Development, construction, start of operation and use of a transmission polarizer for the cold three-axis spectrometer IN12 at the high-flux reactor of the ILL in Grenoble

 

The project provided contributions to the research focus on condensed matter on large-scale equipment in the area of natural basic scientific research in the core area development and construction of innovative instrumentation. It served the funding object expansion of the experimental infrastructure and the development of new methods for researching condensed matter with neutrons with the aim of expanding the possible uses of existing large devices, increasing their performance and thus giving new impetus to research into condensed matter.

Specifically, this concerns the design and implementation of a new type of transmission polarizer, which has so far only been used in very few facilities, for the investigation of complex magnetic structures and excitations by means of polarized neutrons on the cold three-axis spectrometer IN12 at the high-flux reactor of the Laue-Langevin Institute (ILL). Such a polarizer allows the detailed investigation of magnetic solid body properties and thus serves both a better basic understanding and the development of new types of magnetic materials for future applications.

The main components developed, built and put into operation as part of the project essentially comprise: the transmission polarizer along with neutron guide element and magnet enclosure, the magnetic guide field from the polarizer to the end of the conductor, a pair of Helmholtz coils around the monochromator shield, polarizer-specific, reinforced gamma and neutron shields as well as a device for the simple change from polarized to unpolarized neutrons.

Extensive test measurements as well as initial applications to scientific questions confirm the excellent performance data of the new polarizer: very good polarization (90-96% at the sample location, flipping ratio 20-27) over a very wide usable wavelength range (2-6 Å) good transmission (30-35% of the unpolarized neutron flux), and this without readjusting the spectrometer when the setup is changed from non-polarized to polarized. Together with the increase in flux achieved through the upgrade of the primary spectrometer (factor 5 to 10 depending on the wavelength), the IN12 now also sets global standards for three-axis spectrometers for polarized neutrons. The instrument is available to German and international solid-state scientists via the measurement time allocation procedure of the Jülich Center for Neutron Science (JCNS) and the Institut Laue-Langevin (ILL).

The use of neutrons for the detailed investigation of new functional materials, in particular magnetic and spintronic compounds, was pursued as a scientific issue of high relevance within the framework of the project. Examples are multiferroics, pnictide superconductors and magnetically frustrated systems.

Team:

Prof. Dr. Georg Roth (Project manager)
Dr. Wolfgang Schmidt (Project scientist)
Dr. Karin Schmalzl (Project scientist)
Dr. Heifeng Li (Project scientist)

  Copyright: © Bundesministerium für Bildung und Forschung

Funding:

Bundesministerium für Bildung und Forschung
Project executing organization: Deutsches Elektronen-Synchrotron (PT-DESY)
Grant Nr.: 05K10PA3
Project period: 01.07.2010 – 30.06.2013