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E. Jericha, Ch. Gösselsberger, G. Badurek:
"Defining the spectrum and time structure of polarized neutron beams by means of spatial magnetic spin resonance";
Vortrag: International Conference on Neutron Scattering ICNS2013, Edinburgh; 08.07.2013 - 12.07.2013.

We present a novel type of neutron spin resonator for precise wavelength selection and definition of the time structure of thermal, cold and very likely even very cold neutron beams. This device exploits the fact that upon passage of polarised neutrons through a spatially alternating transverse static magnetic field a resonant spin flip will take place for a selected wavelength band of definable shape. Resonance conditions depend on magnetic selector and resonator fields and the resonator geometry. The tailoring of the time structure of the neutron beam is completely decoupled from the wavelength resolution and allows for almost arbitrarily shaped neutron pulses by purely electronic means. We designed prototypes consisting of individually ultra-fast switchable aluminum stages for the generation of neutron pulses in the microsecond regime. These resonators were installed at a polarised neutron beamline at the 250 kW TRIGA reactor of the Vienna University of Technology. Here, we present the related measurements. Driven by their promising results, a new resonator also suitable for very cold neutrons has been realised. These developments are connected to the PERC project which searches for new physics beyond the Standard Model of particle physics via the beta-decay of free neutrons. The envisaged high precision measurements demand perfect knowledge of the key beam parameters like wavelength distribution, degree of polarisation and time structure. Another direction is the implementation of the resonator as integrated monochromator and chopper for advanced neutron time-of-flight spectroscopy. In this context a novel Ramsey-type setup was introduced and experimentally tested.

Polarised neutrons, Neutron optics, Magnetic spin resonator, Travelling wave mode, Spin flipper, Neutron sources; Spin echoes