919 research outputs found
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
410 cms, 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 50, and at the same time keeping a very high
(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 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/Nb direct current
(dc) superconducting quantum interference devices (SQUIDs). While keeping the
total resistance identical to a comparable symmetric SQUID with , we shunted only one of the two Josephson junctions with
. Simulations predict that the optimum energy resolution
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 for an asymmetric
SQUID with an inductance of . For a comparable symmetric device
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
, Wb being the magnetic flux
quantum, is pinned. Each vortex has an oscillatory eigenmode with a frequency
that depends on 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 and on the bias current 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
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