Search

We investigate the magneto-optical (MO) polar Kerr enhancement of Fabry–Pérot cavities with perpendicular magnetic anisotropy for chemical and biological sensing applications. The MO cavities consist of stacked films with a half-mirrored surface layer, a dielectric interference layer, a total-reflection mirror, and a magnetic metal layer. Co80Pt20 and Al-doped ZnO (AZO) thin films were utilized as the magnetic and interference layers, respectively. The cavities produce two types of MO enhancement depending on the thickness of the magnetic layer. The sample with a thick magnetic layer as a total-reflection mirror generates a single peak in the polar Kerr spectrum. Contrarily, inserting a several-nanometer-thick CoPt layer into the AZO layer produces a resonant-type spectrum. Although both samples generate large MO enhancement factors (>50), the magnetic properties significantly differ. The AZO/CoPt/AZO interference layer controls the crystalline and interface conditions and produces a square-shaped out-of-plane hysteresis loop with a large Kerr rotation angle. Moreover, the use of an ultrathin CoPt film significantly reduces the saturation magnetization field. Thus, Fabry–Pérot cavities with a CoPt/AZO interference layer may serve as high-sensitivity, low-energy-consumption sensor elements. [ABSTRACT FROM AUTHOR]

The magneto-optical (MO) properties of perpendicular magnetic nanostructures consisting of a hexagonal close-packed Co80Pt20 nanolayer and noble-metal (Ag or Au) fine grains were investigated under polar Kerr measurement conditions. The samples exhibited an unusual MO hysteresis loop in which the Kerr rotation angle increased at a low magnetic field; this effect was observed in a different wavelength region for the CoPt–Ag and CoPt–Au samples. The nanostructures consisted of two magnetic regions of CoPt layers formed on the grains and on the underlayer. The increase in the Kerr angle was induced by the antiparallel magnetic alignment of these CoPt layers. The opposite MO polarity on the CoPt nanostructures was suggested in a micro-MO observation using scanning near-field polarized optical microscopy. The Ag and Au fine grains induced the MO phase reversal of CoPt in a different wavelength region for each sample. These MO behaviors were attributed to the influence of localized surface plasmons excited on the noble-metal grains. The magneto-plasmonic activities on the CoPt nanostructures were also affected by the underlayer material and the environmental conditions. The perpendicular magnetic nanostructures are expected to provide a new type of probe for chemical and biological sensing applications. [ABSTRACT FROM AUTHOR]

Design and fabrication of a pair of 8kA high temperature superconductor (HTS) current leads is discussed. The current leads are for an accelerator magnet test facility at KEK.

Two 40-kA cable-in-conduit conductor wound from (NbTi)3Sn strands and a titanium conduit were developed by Japan's Atomic Energy Research Institute for the central solenoid of a fusion reactor. Tests were also carried out to determine their superconducting behavior. According to results, the two conductors are characterized by high residual resistivity ratio, the absence of ramp rate limits and a temperature margin higher than two kelvin at 13 T and 40 kA.

Measurements of current-sharing temperature, stability margin, joint performance and resistivity ratio were carried on two cable-in-conduit conductors developed by the Japan Atomic Energy Research Institute. The conductors, which are made of Nb3Sn bronze-processed strands, were shown to have zero ramp-rate limits, non-uniform current distribution and ratio-of-resistivity values of 95 and 100, respectively.

The effect of cyclic pulsed operation on the coil performance was studied from the electrical and mechanical points of view in the second experiment of the [Nb.sub.3]Sn Demo Poloidal Coil (DPC-EX). Current sharing temperatures, ac losses, displacements, and strains were measured before and after cyclic pulsed operation, which consisted of about 350 cycles. No degradation of the electrical and mechanical performance of the DPC-EX was observed in the range of these cycles.

A superconducting magnet system has been designed and constructed for a 1-MW gyrotron operating at frequencies between 110 GHZ and 140 GHz. Aside from superconducting magnets, it is composed of a cryostat, power supplies, a two-stage cooler. The latter is used to minimize the thermal load of liquid helium. Tests with a 5.0-T magnetic field in the resonance region of its superconducting split coil confirm the validity of the design.

The characterization of the Toroidal Model Pancake (TMP) is presented. The TMP is a superconducting coil constructed by the Japan Atomic Energy Research Institute for fusion reactor studies. Built of hollow cooling monolithic superconductors, it begun testing in Aug 1992. Its performance is described along with cooldown, pressure drop, stability and mechanical issues.