Compact spherical neutron polarimeter using high-Tc YBCO films

Abstract

We describe a simple, compact device for spherical neutron polarimetry measurements at small neutron scattering angles. The device consists of a sample chamber with very low (<0.01 G) magnetic field flanked by regions within which the neutron polarization can be manipulated in a controlled manner. This allows any selected initial and final polarization direction of the neutrons to be obtained. We have constructed a prototype device using high-Tc superconducting films and mu-metal to isolate regions with different magnetic fields and tested device performance in transmission geometry. Finite-element methods were used to simulate the device’s field profile and these have been verified by experiment using a small solenoid as a test sample. Measurements are reported using both monochromatic and polychromatic neutron sources. The results show that the device is capable of extracting sample information and distinguishing small angular variations of the sample magnetic field. As a more realistic test, we present results on the characterization of a 10 μm thick Permalloy film in zero magnetic field, as well as its response to an external magnetic field.

Improving polarized neutron imaging for visualization of the Meissner effect in superconductors

“…4(a), two magnetic guide fields B 1 and B 2 are generated by a solenoid and an electromagnet before and after the superconducting YBCO film, respectively. The electromagnets on the back side generate a uniform magnetic field 16 of 20 G, defined by its orientation, up to the superconductor surface. The front solenoid magnetic field diverges and becomes parallel to the superconductor plane at the surface, aligning with the radial direction pointing from the center axis of the solenoid.…”

Wide Angle Spherical Neutron Polarimetry at Oak Ridge National Laboratory

“…The wide-angle design for our device is based on an existing small angle SNP development (CryoCUP) [5]. It will be used on the Polarized Triple-Axis Spectrometer (PTAX) and the General-Purpose Small Angle Neutron Scattering instrument at the High Flux Isotope Reactor (HFIR).…”

Implementation of a new Cryopad on the diffractometer POLI at MLZ

“…However this compact device is presently limited in its scattering angle range to direct transmission and SANS measurements. Moreover, similar to the first Cryopad, the same cryostat controls the temperature of both the sample and Meissner shields, limiting the sample temperature range to 20-80 K [37].…”