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We have built a high-resolution soft x-ray spectrometer using a 3 × 3 array of superconducting Nb-AI-AIOx-AI-Nb tunnel junctions. The detector is cooled to ∼0.1 K by a two-stage adiabatic demagnetization refrigerator while being held at the end of a 40-cm-long detector snout that can be inserted into an experimental chamber. The 0.6 mm × 0.6 mm array has an energy resolution of 10-15 eV FWHM for x-ray energies below I kev and total count rate capabilities above 100 000 counts/s. We demonstrate the capabilities of the instrument in a study of anisotropy in c-axis oriented MgB[sub 2] films by near edge x-ray absorption spectroscopy. The absorption fine structure at the B K-edge differs for excitation with x-rays polarized along the c-axis and in the ab-plane of the MgB[sub 2] film. We discuss the implications of the anisotropy for the density of states in MgB[sub 2] at the Fermi surface. [ABSTRACT FROM AUTHOR]

Studies the extreme ultra-violet response of niobium-based superconducting tunnel junction detectors. Energy resolution; Monte Carlo simulations of the energy relaxation process upon photon absorption in heterogeneous superconducting multilayers; Causes of line splitting between peaks originating from niobium and aluminum layers.

Reports on the use of superconducting tunnel junctions coupled to superconducting absorbers, as high-resolution, high-efficiency X-ray spectrometers. Testing of devices with niobium X-ray absorbing layers; Measurement of current pulses.

Presents a superconducting x-ray detector with charge amplification due to multiple quasiparticle tunneling. Use of coupled superconducting tunnel junctions and absorbers; Proportionality of quasiparticles to the incident particle energy; Features and characteristics of the device.

Describes the design of a solid-state microrefrigerator based on normal-insulator-superconductor tunnel junctions. Limitation of the junction area by the need for defect-free tunnel barrier; Combination of the substrate and superconducting electrode in a macroscopic superconducting single crystal.