On the possibility of application of superconducting tunnel-junction detectors in Mössbauer spectroscopy

It is shown that a Nb-based superconducting tunnel-junction detector can be used to record γ radiation in the energy range from 1 to 15 keV. The possibility of application of such detectors in Mössbauer spectroscopy is discussed. Prospects of application of tantalum absorbers are considered, in particular, the possibility of developing a cryogenic resonant detector for ¹⁸¹Ta.     

On the passive electrode signal in X-ray detectors based on superconducting tunnel junctions

X-ray detectors based on superconducting tunnel junctions with the multilayer electrode structure described by the formula Ti/Nb/Al, AlO _x /Al/Nb/NbN were studied. The main signal arose during X-ray absorption in the top electrode and had an energy resolution of ∼90 eV at the 5.9-keV line. The bottom passive Ti/Nb electrode provided rapid absorption of excess quasiparticles. The residual signal of the passive electrode was from 7 to 17% of the main signal amplitude. The dependences of the amplitude of this signal on the voltage and the absorbed X-ray energy were measured for detectors with different thicknesses of the top and bottom electrodes. The rate of quasiparticle trapping by the energy trap in the Ti/Nb bilayer was estimated. The main mechanisms of the formation of the passive electrode signal formation were considered and methods for its suppression were proposed.     

A STJ X-ray detector with a β-tantalum sublayer

The first step in the research and development of detectors for ¹⁸¹Ta Mössbauer spectroscopy based on superconductive tunnel junctions (STJ) is taken. The idea of using β-tantalum as a trapping layer for the inactivation of the base electrode in a detector with the structure β-Ta/Nb/Al, AlO _x /Al/Nb/NbN is successfully executed.     

Superconducting integrated on-board spectrometer of the submillimeter-wave range for atmospheric research

We present the latest results of developing and implementing a fully superconducting integrated receiver of the submillimeter-wave range on the basis of the superconductor-insulator-superconductor tunnel junction. Characteristics of a new-generation unique device operated in the frequency range 500–600 GHz and intended for atmospheric research onboard a high-altitude balloon within the framework of the international TELIS project are given. This frequency range comprises spectral lines of many chlorine-containing compounds, the registration of which is a major problem of the environmental monitoring of the atmosphere. In the process of creating the spectrometer, we developed the technology for manufacturing Nb/AlN/NbN junctions, which made it possible to reduce the emission linewidth of the superconducting local oscillator based on the long Josephson junction and decrease the noise temperature of the receiver. At the same time, the possibility to continuously tune the local-oscillator frequency in the entire operating range was realized.     

Development of the physical principles of the design and implementation of a 500–700 GHz spectrometer with a superconducting integrated receiver

A spectrometer based on the effect of freely decaying polarization in the frequency range 500–700 GHz has been designed. Radiation sources are harmonics from a quantum semiconductor superlattice frequency multiplier. The receiving system of this spectrometer is constructed using a superconducting integrated receiver based on a superconductor-insulator-superconductor mixer and a flux-flow oscillator operating as a heterodyne oscillator. The spectrometer has been used to measure absorption lines of NH₃ in a sample of expired air (572 GHz).     

Investigation of the regimes of mixing of superconducting tunneling structures

The regimes of operation of a superconductor–insulator–superconductor tunnel junction based on three-layer structures Nb/AlOx/Nb and Nb/AlN/NbN as a harmonic mixer (for frequencies of the order of 600 and 20 GHz, respectively) and a frequency up-converter (in the frequency range from 0.1 to 5.0 GHz) have been investigated experimentally. The quasiparticle and Josephson mixing regimes have been compared. It has been shown that, in some practical applications, such as the use of the superconductor–insulator–superconductor junction as a cryogenic harmonic phase detector, the Josephson mixing regime is more preferable, because it can provide a higher signal and a greater signal-to-noise ratio as compared to the quasiparticle mixing regime. It has also been demonstrated that the Josephson mixing regime is promising for the use in signal multiplexing systems for superconducting detectors.     

Superconducting terahertz receivers for space-borne and balloon-borne radio telescopes

A superconducting heterodyne receiver based on superconductor–insulator–superconductor (SIS) junctions and a bolometric receiver based on superconductor–insulator–normal metal (SIN) tunnel junctions developed at the Kotelnikov Institute is described. The noise temperature and noise equivalent power of such a receiver fit the requirements for the TELIS, BOOMERANG, OLIMPO, and LSPE aerostatborne radio telescopes, and the space-based SPICA and MILLIMETRON projects, among others. Applications of such receivers for medical diagnostics and remote control are described.     

Effect of poly (lactic acid)‐graft‐glycidyl methacrylate as a compatibilizer on properties of poly (lactic acid)/banana fiber biocomposites

The main aim of this study was to synthesis of poly (lactic acid) (PLA)‐graft‐glycidyl methacrylate (GMA) as well as its influence on the properties of PLA/banana fiber biocomposites. PLA‐graft‐GMA graft copolymer (GC) was synthesized by melt blending PLA with GMA using benzoyl peroxide and dicumyl peroxide as initiators. Graft copolymerization was confirmed by FTIR and ¹H‐NMR spectroscopic studies. PLA/silane treated banana fiber (SiB) biocomposites with various GC concentrations were prepared by melt blending followed by injection molding techniques. The influence of GC content on the mechanical, thermal and moisture resistance properties of the composite was investigated. The addition of 15 wt% GC content in the biocomposite provided optimum tensile and flexural strength, which is attributed to the greater compatibility between fiber and PLA matrix. The thermal properties of biocomposites have been evaluated using thermogravimetric analysis which provided evidence of improved interfacial adhesion between SiB and PLA by the addition of GC. Additionally, GC enhanced the moisture absorption resistance of biocomposites. These results indicated that GC is indeed a good candidate as a compatibilizing agent to improve the compatibility in PLA/fiber biocomposites. Copyright © 2015 John Wiley & Sons, Ltd.