MONOPOL - A traveling-wave magnetic neutron spin resonator for tailoring polarized neutron beams

Erwin Jericha,Stefan Baumgartner,Bernhard Maximilian Berger,Robert Raab,Masahiro Hino,Christoph Gösselsberger,Hartmut Abele,Gerald Badurek,Peter Geltenbort,Tatsuro Oda

doi:10.1038/s41598-020-62612-9

Abstract

We report on first experimental tests of a neutron magnetic spin resonator at a very cold neutron beam port of the high flux reactor at the ILL Grenoble. When placed between two supermirror neutron polarizers and operated in a pulsed traveling-wave mode it allows to decouple its time- and wavelength-resolution and can therefore be used simultaneously as electronically tunable monochromator and fast beam chopper. As a first ‘real’ scientific application we intend its implementation in the PERC (p roton and e lectron r adiation c hannel) project related to high-precision experiments in neutron beta decay.

Highlights

We report on first experimental tests of a neutron magnetic spin resonator at a very cold neutron beam port of the high flux reactor at the ILL Grenoble
In recent years we have developed several prototypes of neutron spin resonators with independent elements, able to be operated in such a traveling-wave mode
The vertical selector field amounted to B0 = 101 μT produced by a DC current of 270 mA which results in a resonance wavelength λ0 ~ 58Å

Summary

Introduction

This method exploits the fact that upon passage through an undulatory horizontal static magnetic field B1 each neutron in its rest frame experiences an oscillating magnetic field with its own specific frequency according to its velocity and the spatial undulation period of the resonator If this frequency equals the LARMOR frequency, determined by the strength of a homogeneous static ‘selector’ field B0 which is applied in vertical direction, a resonant spin flip will take place in close analogy to standard NMR. The first experimental tests at the 250 kW low flux TRIGA research reactor of our university in Vienna could be performed only with a dichromatic beam of thermal neutrons delivered from 1st and 2nd order (002)-reflection of a highly oriented pyrolytic graphite (HOPG) monochromator These experiments allowed us to improve the resonator performance step-by-step from one prototype to the and to demonstrate that our proposed concept is useful for flexible neutron beam property tailoring. Details of the dedicated electronics which we have developed to run MONOPOL will be described in a forthcoming paper

Methods

Results

Conclusion