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E. Jericha, S. Baumgartner, B. Berger, T. Gerstmayr, Ch. Gösselsberger, S. Gumpenberger, S. Nowak, R. Raab, G. Badurek:
"MONOPOL - An ultra-flexible resonator for the tailoring of polarised neutron beams";
Poster: Symposium "Research at European Neutron and Synchrotron facilities by Austrian researchers", Wien; 11.11.2013 - 12.11.2013.

We present a novel type of neutron spin resonator for precise wavelength selection and definition of the time structure of thermal, cold and even very cold polarised neutron beams [1]. This device exploits the fact that upon passage of neutrons through a spatially alternating transverse static magnetic field each neutron in its rest frame experiences an alternating field with a frequency depending on the neutron velocity and the spatial period of the resonator. If this frequency equals the Larmor precession frequency a resonant spin flip will take place [2]. Furthermore, the tailoring of the time structure of this neutron beam is completely decoupled from the adjustment of the wavelength resolution and allows for almost arbitrarily shaped neutron pulses by purely electronic means.

To demonstrate the feasibility of this technique, we designed and engineered two prototypes consisting of individually ultra-fast switchable aluminum stages for the generation of neutron pulses in the microsecond regime [3]. These resonators were installed at a polarised neutron beamline at the 250 kW TRIGA reactor of the Vienna University of Technology. Driven by the promising results of these test measure¬ments, a new resonator, for the application at very cold neutron (VCN) beamlines, has been developed. Here, we present results which demonstrate the successful operation of this device [4].

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 [2]. The related 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 our device 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 [5].

[1] G. Badurek, E. Jericha, Physica B 335, 2003, 215.
[2] Ch. Gösselsberger, H. Abele, G. Badurek, E. Jericha, S. Nowak, G. Wautischer, A. Welzl, Physics Procedia 17, 2011, 62.
[3] G. Badurek, Ch. Gösselsberger, E. Jericha, Physica B 406, 2011, 2458.
[4] Ch. Gösselsberger, H. Abele, G. Badurek, E. Jericha, W. Mach, S. Nowak, T. Rechberger, J. Phys.: Conf. Ser. 340, 2012, 012028.
[5] Ch. Gösselsberger, M. Bacak, T. Gerstmayr, S. Gumpenberger, A. Hawlik, B. Hinterleitner, E. Jericha, S. Nowak, A. Welzl, G. Badurek, Physics Procedia 42, 2013, 106.