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The application of a Josephson generator of the terahertz range based on a long superconductor–insulator–superconductor tunnel junction matched with a transmitting antenna and emitting a signal into open space is demonstrated for gas spectroscopy. The generator is used as an active source, the signal of which is absorbed by a sample of a gas mixture in a cell with a length of 60 cm and then recorded by a spectrometer based on a superconductor–insulator–superconductor receiver with a spectral resolution better than 100 kHz. In the experiment, the absorption lines of ammonia and water in the terahertz range were recorded, and the dependence of the spectral characteristics of the absorption lines on the pressure of the gas mixture in a wide range (from 0.005 to 10 mbar) was demonstrated.

Radiation spectra from a 119m Sn Mossbauer source are registered using Nb-based superconducting tunnel junction detectors. Mossbauer and accompanying X-ray radiation are detected via escape peaks with high energy resolution.

A topology of thin-film SQUID sensors that are based on Nb/AlO x /Nb tunnel junctions has been developed and optimized for nondestructive testing of materials and for other systems with a magnetic field sensitivity of

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.

Niobium-based superconducting tunnel detectors were used for the first time to register nuclear gamma-resonance (the Mossbauer effect). Resonant electrons emerging upon irradiation of RhFe alloy enriched with 57Fe isotope by a 57Co(Rh) Mossbauer source were registered in the scattering geometry, offering the possibility of using superconducting tunnel detectors for the conversion Mossbauer spectroscopy at low temperatures and allowing us to compare them to available developments.

The current-voltage characteristics of superconducting tunnel junction (STJ) X-ray detectors were measured in the temperature range from 4.2 to 0.1 K. The freeze-out of the thermal tunneling current was compared between an STJ detector with a traditional Nb/Al/Al2O3/Al/Nb layer structure and a Ti/Nb/Al/Al2O3/Al/Nb/NbN detector whose low-gap Ti film kills the X-ray response of the base electrode. The current decrease and the linear low-temperature I(V) characteristics for the detector with the killed electrode can be qualitatively explained by tunneling current contribu- tions from the subgap states of the Ti film. The data are analyzed on the basis of the proximity theory in the dirty limit.

The first step in the research and development of detectors for 181Ta Mossbauer 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, AlOx/Al/Nb/NbN is successfully executed.

Superconducting tunnel junctions X-ray detectors Ti/Nb/Al,AlO x /Al/Nb(2)/NbN with killed Ti/Nb electrode was studied as a function of bias voltage, energy of the absorbed quantum, and thickness of the Nb(2) layer. The data was compared with a simple diffusion model including the losses of excess quasiparticles due to self-recombination. It was shown that increasing of the electrode thickness reduces the self-recombination contribution and improves the linearity of the detector response.

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.

The dependence of the noise equivalent temperature difference (NETD) of a superconducting integrated receiver (SIR) on the receiver noise temperature and the inputsignal level has been investigated. An unprecedented NETD of 13±2 mK has been measured at a SIR noise temperature of 200 K, intermediate-frequency bandwidth of 4 GHz, and time constant of 1 s. With a decrease in the input signal, an improvement in the NETD is observed. This effect is explained by a reduction in the influence of the instabilities of the receiver power supply and the amplification circuit that occur when the input signal is decreased.

Superconducting tunnel junction X-rays detectors Ti/Nb/Al/AlO x /Al/Nb/NbN with the Ti/Nb/Al/ killed electrode has been studied under irradiation by X-rays photons of different energies produced by the fluorescence method. The nonlinearity of the STJ-detector response versus photon energy has been studied as a function of the bias voltage. The minimum of the nonlinearity is observed when the tunneling probability P 1 has maximum and the detector signals have shortest rise times. The experimental data were analyzed on the basis of the diffusion model taking into account the quasiparticle self-recombination. The simple approximate expression for the self-recombination contributions to STJ-detector signal was obtained. The nonlinearity of the response depends on the ratios of the recombination constant to the diffusion coefficient R/D and the diffusion length to the initial radius of the quasiparticle distribution Λ/a 0 and is inverse proportional to the thickness of the electrode.

The effect of the recombination-and edge-related losses of nonequilibrium quasiparticles on the energy resolution of superconducting tunneling detectors is studied. The dependence of the signal on the energy of X-ray photons is measured and the shape of instrument-related lines is studied for the Ti/Nb/Al/AlOx/Al/Nb/NbN detectors with the Ti/Nb passive electrode. Experimental data are analyzed using the diffusion-based model of tunneling detectors.

The energy resolution of superconducting tunnel detectors is investigated from the point of view of the effect of recombination and boundary losses of nonequilibrium quasiparticles. Using the x-ray fluorescence method, the dependence of the signal on the energy of x-ray quanta is measured for Ti/Nb/Al/AlOx/Al/Nb/NbN detectors. The form of the apparatus line is also investigated. The experimental data are analyzed using the diffusion model of tunnel detectors.

Superconducting tunnel junction X-rays detectors Ti/Nb/Al/AlOx/Al/Nb/NbN with the Ti/Nb/Al/ killed electrode were studied under irradiation by X-rays photons of different energies produced by the fluorescence method. The nonlinearity of the detector response and the shape of the detector line were analyzed on the basis of the diffusion model taking into account the quasiparticle self-recombination and edge losses.

Superconducting tunnel junctions (STJs) with the structure Ti/Nb/Al, AlO x /Al/Nb/NbN and corresponding layer thickness 30/100/8/13/150/30 nm were investigated as X-ray detectors at T =1.35 K. STJs with one active electrode in which the response of the other one is suppressed due to trapping layer on the surface opposite to the tunnel barrier have a number of potential advantages. The best line width (FWHM) is 78 eV for 6400 μm 2 junction. Contribution of the electronic noise is about 50 eV. The intrinsic detector line width is less than 60 eV. The collected charge from inactive electrode is more than 8 times less than that from the active one. Titanium proved to be an appropriate material for a sublayer and a trap.

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 Mossbauer spectroscopy is discussed. Prospects of application of tantalum absorbers are considered, in particular, the possibility of developing a cryogenic resonant detector for 181Ta.

Response of the superconducting tunnel junction X-rays detector Ti/Nb/Al/AlOx/Al/Nb/NbN with the Ti killed electrode was obtained for different photon energies by the X-rays fluorescence method. A strong nonlinearity of the detector response was analyzed on the basis of a diffusion model taking into account the quasiparticle self-recombination and edge losses.

The development of terahertz imaging instruments for security systems is on the cutting edge of terahertz technology. We are developing a THz imaging system based on a superconducting integrated receiver (SIR). An SIR is a new type of heterodyne receiver based on an SIS mixer integrated with a flux-flow oscillator (FFO) and a harmonic mixer which is used for phase-locking the FFO. Employing an SIR in an imaging system means building an entirely new instrument with many advantages compared to traditional systems.

We study microwave properties of a superconducting tunable coplanar waveguide (CPW). Pairs of Josephson junctions are forming superconducting quantum interference devices (SQUIDs), which shunt the central conductor of the CPW. The Josephson inductance of the SQUIDs is varied in the range of 0.08-0.5 nH by applying an external dc magnetic field. The central conductor of the CPW contains Josephson junctions connected in series that provide extra inductances; the magnetic field controlling the SQUIDs is weak enough not to influence the inductance of the chain of the single junctions. The circuit is designed to have left- and right-handed transmission properties separated by a variable rejection band; the band edges can be tuned by the magnetic field. We present transmission measurements on CPWs based on up to 120 Nb-AlOx-Nb Josephson junctions. At zero magnetic field, we observed no rejection band in the frequency range of 8-11 GHz. When applying the magnetic field, a rejection band between 7 GHz and 9 GHz appears. The experimental data are compared with numerical simulations., 8 pages, 8 figures

We present a method to analyze the electromagnetic behavior of superconducting planar microwave metamaterials. Using a laser scanning microscope (LSM), we image the microwave response of two-dimensional arrays of magnetic meta-atoms. This method allows us to investigate contributions of individual meta-atoms to the macroscopic response and thus provides a useful tool for characterization and optimization. The meta-atoms in the present experiment are frequency tunable superconducting quantum interference devices (SQUIDs).

We investigate, by experiments and numerical simulations, thermal activation processes of Josephson tunnel junctions in the presence of microwave radiation. When the applied signal resonates with the Josephson plasma frequency oscillations, the switching current may become multi-valued in a temperature range far exceeding the classical to quantum crossover temperature. Plots of the switching currents traced as a function of the applied signal frequency show very good agreement with the functional forms expected from Josephson plasma frequency dependencies on the bias current. Throughout, numerical simulations of the corresponding thermally driven classical Josephson junction model show very good agreement with the experimental data., Comment: 10 pages and 4 figures

Using superconducting quantum interference devices (SQUIDs) as the basic, low-loss elements of thin-film metamaterials has one main advantage: their resonance frequency is easily tunable by applying a weak magnetic field. The downside, however, is a strong sensitivity to stray and inhomogeneous magnetic fields. In this work, we demonstrate that even small magnetic fields from electronic components destroy the collective, resonant behaviour of the SQUID metamaterial. We also show how the effect of these fields can be minimized. As a first step, magnetic shielding decreases any initially present fields, including the earth’s magnetic field. However, further measures such as improvements in the sample geometry have to be taken to avoid the trapping of Abrikosov vortices.