Suppression of dissipation in Nb thin films with triangular antidot arrays by random removal of pinning sites

The depinning current Ic versus applied magnetic field B close to the transition temperature Tc of Nb thin films with randomly diluted triangular arrays of antidots is investigated. % Our experiments confirm essential features in Ic(B) as predicted by Reichhardt and Olson Reichhardt [Phys.Rev. B 76, 094512 (2007)]. % We show that, by introducing disorder into periodic pinning arrays, Ic can be enhanced. % In particular, for arrays with fixed density n_p of antidots, an increase in dilution Pd induces an increase in Ic and decrease of the flux-flow voltage for B>Bp=n_p Phi_0.Comment: 5 pages, 4 figure

Proposal on Application of the Multi-Wire Proportional Chambers of the LHCb MUON Detector at Very High Rates for the Future Upgrades

The MUON Detector (MD) of LHCb is one of the largest instruments of this kind worldwide, and one of the most irradiated. It has performed exceptionally well during the RUN1 and RUN2 of the LHC at an instantaneous luminosity of 4$\times$10$^{32}$ cm$^{-2}$s$^{-1}$, with tracking inefficiencies at the level of 1$\%$ and 2.6$\%$, respectively. Looking forward for the future LHCb Upgrade 2 (U2) planned in 2031 and aiming in running the detector at increased luminosity by a factor $\sim$50, and at the same time keeping a very high ($\sim$99$\%$) detection efficiency, an option with reuse significant part of the present Multi-Wire Proportional Chambers (MWPC) in a new Muon System is presented. In addition, the first idea of new Front End Electronics (FEE) and an existing test setup applicable for designing both: new MWPCs with a higher granularity of the cathode readout pads and new FEE are described

Proximity effect model of ultra-narrow NbN strips

We show that narrow superconducting strips in superconducting (S) and normal (N) states are universally described by the model presenting them as lateral NSN proximity systems in which the superconducting central band is sandwiched between damaged edge-bands with suppressed superconductivity.The width of the superconducting band was experimentally determined from the value of magnetic field at which the band transits from the Meissner state to the static vortex state. Systematic experimental study of 4.9 nm thick NbN strips with widths in the interval from 50 nm to 20 ${\mu}$m, which are all smaller than the Pearl's length, demonstrates gradual evolution of the temperature dependence of the critical current with the change of the strip width

Direct current superconducting quantum interferometers with asymmetric shunt resistors

We have investigated asymmetrically shunted Nb/Al-AlO$_x$/Nb direct current (dc) superconducting quantum interference devices (SQUIDs). While keeping the total resistance $R$ identical to a comparable symmetric SQUID with $R^{-1} = R_1^{-1} + R_2^{-1}$, we shunted only one of the two Josephson junctions with $R = R_{1,2}/2$. Simulations predict that the optimum energy resolution $\epsilon$ and thus also the noise performance of such an asymmetric SQUID can be 3--4 times better than that of its symmetric counterpart. Experiments at a temperature of 4.2\,K yielded $\epsilon \approx 32\,\hbar$ for an asymmetric SQUID with an inductance of $22\,\rm{pH}$. For a comparable symmetric device $\epsilon = 110\,\hbar$ was achieved, confirming our simulation results.Comment: 5 pages, 4 figure

Early potato

The harvest area of potatoes in South East Europe is about 580 000 ha with a production of about 11 000 000 tonnes. It is estimated that 20–25% of all harvested area is used for early potatoes. Early potato is of high biological and nutritional value, and is suitable for growing on small family-run commercial farms. In the continental area of South and South East Europe, new potato matures for harvest in late May, June and early July. In recent years, early potato has reached the market 20–25 days earlier thanks to the adoption of specific cultivation practices and growing technologies, as well as an increase in financial input per unit area. As the first spring vegetable, early potato is considered a supreme biological and economic crop. The first precondition for high, stable and quality production of early potato is the choice of very early-maturing cultivars with high yield potential, good adaptability and stability. The second precondition is the planting of equally sprouted and certified seedlings with mulching and crop covering with agrotextiles. In the continental area of South and South East Europe, apart from early potato farming in temporary protected areas – for example, direct crop covering with or without mulching and in low plastic tunnels – early potato is also grown in large plastic tunnels without additional heating. Early potato is planted in mid-February in the Mediterranean area. This is 30 days earlier than in the continental area, and when covered with agrotextiles it can be harvested even earlier. This chapter presents some biological and agrotechnological aspects, such as biological needs, fertilization, irrigation, harvesting and storage of early potatoes

Spectroscopy of a fractional Josephson vortex molecule

In long Josephson junctions with multiple discontinuities of the Josephson phase, fractional vortex molecules are spontaneously formed. At each discontinuity point a fractional Josephson vortex carrying a magnetic flux $|\Phi|<\Phi_0$, $\Phi_0\approx 2.07\times 10^{-15}$ Wb being the magnetic flux quantum, is pinned. Each vortex has an oscillatory eigenmode with a frequency that depends on $\Phi/\Phi_0$ and lies inside the plasma gap. We experimentally investigate the dependence of the eigenfrequencies of a two-vortex molecule on the distance between the vortices, on their topological charge $\wp=2\pi\Phi/\Phi_0$ and on the bias current $\gamma$ applied to the Josephson junction. We find that with decreasing distance between vortices, a splitting of the eigenfrequencies occurs, that corresponds to the emergence of collective oscillatory modes of both vortices. We use a resonant microwave spectroscopy technique and find good agreement between experimental results and theoretical predictions.Comment: submitted to Phys. Rev.

Enhancement of superconductivity in NbN nanowires by negative electron-beam lithography with positive resist

We performed comparative experimental investigation of superconducting NbN nanowires which were prepared by means of positive-and negative electron-beam lithography with the same positive tone Poly-methyl-methacrylate (PMMA) resist. We show that nanowires with a thickness 4.9 nm and widths less than 100 nm demonstrate at 4.2 K higher critical temperature and higher density of critical and retrapping currents when they are prepared by negative lithography. Also the ratio of the experimental critical-current to the depairing critical current is larger for nanowires prepared by negative lithography. We associate the observed enhancement of superconducting properties with the difference in the degree of damage that nanowire edges sustain in the lithographic process. A whole range of advantages which is offered by the negative lithography with positive PMMA resist ensures high potential of this technology for improving performance metrics of superconducting nanowire singe-photon detectors