10,914 research outputs found
Neutron methods for the direct determination of the magnetic induction in thick films
We review different neutron methods which allow extracting directly the value
of the magnetic induction in thick films: Larmor precession, Zeeman spatial
beam-splitting and neutron spin resonance. Resulting parameters obtained by the
neutron methods and standard magnetometry technique are presented and compared.
The possibilities and specificities of the neutron methods are discussed
Polarized neutron channeling as a tool for the investigations of weakly magnetic thin films
We present and apply a new method to measure directly weak magnetization in
thin films. The polarization of a neutron beam channeling through a thin film
structure is measured after exiting the structure edge as a microbeam. We have
applied the method to a tri-layer thin film structure acting as a planar
waveguide for polarized neutrons. The middle guiding layer is a rare earth
based ferrimagnetic material TbCo5 with a low magnetization of about 20 mT. We
demonstrate that the channeling method is more sensitive than the specular
neutron reflection method
Controlling the dynamics of an open many-body quantum system with localized dissipation
We experimentally investigate the action of a localized dissipative potential
on a macroscopic matter wave, which we implement by shining an electron beam on
an atomic Bose-Einstein condensate (BEC). We measure the losses induced by the
dissipative potential as a function of the dissipation strength observing a
paradoxical behavior when the strength of the dissipation exceeds a critical
limit: for an increase of the dissipation rate the number of atoms lost from
the BEC becomes lower. We repeat the experiment for different parameters of the
electron beam and we compare our results with a simple theoretical model,
finding excellent agreement. By monitoring the dynamics induced by the
dissipative defect we identify the mechanisms which are responsible for the
observed paradoxical behavior. We finally demonstrate the link between our
dissipative dynamics and the measurement of the density distribution of the BEC
allowing for a generalized definition of the Zeno effect. Due to the high
degree of control on every parameter, our system is a promising candidate for
the engineering of fully governable open quantum systems
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