We considered a mesoscopic superconductor/normal metal (S/N) structure in which the N reservoirs are maintained at different temperatures. It is shown that in the absence of current between the N reservoirs a voltage difference VT arises between the superconducting and normal conductors. The voltage VT oscillates with increasing phase difference ϕ between the superconductors, and its magnitude does not depend on the small parameter (T /ǫF ).

The international Muon Ionization Cooling Experiment (MICE), which is under construction at the Rutherford Appleton Laboratory (RAL), will demonstrate the principle of ionization cooling as a technique for the reduction of the phase-space volume occupied by a muon beam. Ionization cooling channels are required for the Neutrino Factory and the Muon Collider. MICE will evaluate in detail the performance of a single lattice cell of the Feasibility Study 2 cooling channel. The MICE Muon Beam has been constructed at the ISIS synchrotron at RAL, and in MICE Step I, it has been characterized using the MICE beam-instrumentation system. In this paper, the MICE Muon Beam and beam-line instrumentation are described. The muon rate is presented as a function of the beam loss generated by the MICE target dipping into the ISIS proton beam. For a 1 V signal from the ISIS beam-loss monitors downstream of our target we obtain a 30 KHz instantaneous muon rate, with a neglible pion contamination in the beam.

The conceptual design for a nonscaling fixed field alternating gradient accelerator suitable for charged particle therapy (the use of protons and other light ions to treat some forms of cancer) is described.

We analyse the measured critical current Im in a mesoscopic 4-terminal S/N/S structure. The current through the S/N interface is shown to consist not only of the Josephson component Ic sin ϕ, but also a phase-coherent part Isg cos ϕ of the subgap current. The current Im is determined by the both components Ic and Isg, and depends in a nonmonotonic way on the voltage V between superconductors and normal reservoirs reaching a maximum at V ∼ = ∆/e. The obtained theoretical resultas are in qualitative agreement with recent experimental data.Recent achievements in nanotechnology have revived interest in the study of nonequilibrium and phase-coherent phenomena in superconductor-normal metal (S/N) structures. One of the most remarkable, discovered recently [1], was the observation of the sign reversal of the Josephson critical current I c (the so-called π-junction) in a multiterminal mesoscopic Nb/Au/Nb structure under nonequilibrium conditions. By passing an additional current through the N layer or, in another words, by applying a voltage V to the normal reservoirs (see Fig.1) with respect to the superconductors, one can create a nonequlibrium electron-hole distribution, or at least one can shift this distribution with respect to the electron-hole distribution in the superconductors. Under this condition, the critical current I c decreases with V and changes sign at a certain value of the applied voltage V . This effect was predicted first in Ref.[2] where a ballistic 3-terminal structure was considered (for more details, see also Refs. [3,4]). In diffusive 4-terminal S/N/S structures, the sign-reversal effect has been considered in Refs. [5][6][7] (see also [8,9]). The sign-reversal effect and switching of the π-junction into a state where ϕ = π has much in common with an instability of an uniform superconductor with a nonequilibrium distribution function [10,11].In multi-terminal S/N/S structures one can observe not only the sign reversal effect, but also a number of other interesting phenomena. For example, the conductance of a normal wire between N reservoirs oscillates with varying phase difference ϕ (see review articles [12,13]). In addition, as shown in Refs. [5,14], the measured critical current I m depends on the geometry of a particular structure and instead of decreasing may also increase with increasing voltage V . In particular one can observe Josephson-like effects (plateau on the I 3 (V S ) curve, oscillations of the measured critical current I m in a magnetic field etc) even if the Josephson coupling between superconductors under equilibrium conditions is negligable. The reason for these effects is that the current I m in a multi-terminal S/N/S structure is determined not only by the Josephson component I c sin ϕ, but also by the phase-dependent subgap current I sg cos ϕ through the S/N interface. Therefore even in the case of a small I c , the current I m can be altered by varying the phase φ. An increase of the critical current was observed in the recent paper [15] where a mesoscopic three-terminal ...

Particle accelerator failures lead to unscheduled downtime and lower reliability. Although simple to mitigate while they are actually happening such failures are difficult to predict or identify beforehand. In this work we propose using machine learning approaches to predict machine failures via beam current measurements before they actual occur. To demonstrate this technique in this paper we examine beam pulses from the Oakridge Spallation Neutron Source (SNS). By evaluating a pulse against a set of common classification techniques we show that accelerator failure can be identified prior to actually failing with almost 80% accuracy. We also show that tuning classifier parameters and using pulse properties for refining datasets can further lead to almost 92% accuracy in classification of bad pulses. Most importantly, in the paper we establish there is information about the failure encoded in the pulses prior to it, so we also present a list of feasible next steps for increasing pulse classification accuracy.

We have calculated the temperature dependence of the conductance variation (δS(T )) of mesoscopic superconductor normal metal(S/N) structures, in the diffusive regime, analysing both weak and strong proximity effects. We show that in the case of a weak proximity effect there are two peaks in the dependence of δS(T ) on temperature. One of them (known from previous studies) corresponds to a temperature T1 of order of the Thouless energy (ǫ T h ), and another, newly predicted maximum, occurs at a temperature T2 where the energy gap in the superconductor ∆(T2) is of order ǫ T h . In the limit L φ < L the temperature T1 is determined by Dh/L 2 φ (L φ is the phase breaking length), and not ǫ T h . We have also calculated the voltage dependence δS(V ) for a S/F structure (F is a ferromagnet) and predict non-monotonic behaviour at voltages of order the Zeeman splitting.Pacs numbers: 74.25.fy, 72.10Bg, 73.40Gk, 74.50.+r Since the late 1970's it has been known that the conductance (G) of S/N mesoscopic structures depends on temperature (T ) (and voltage (V )) in a non-monotonic way (see reviews [1,2]). This behaviour was first predicted in Ref.[3] where a simple point S/N contact was analysed. The authors of Ref.[3], using a microscopic theory and assuming that the energy gap in the superconductor (∆) is much less than the Thouless energy ǫ T h ≡hD/L 2 (D is the diffusion constant), showed that the zero-bias conductance G coincides at zero temperature with its normal state value (G n ). With increasing T , G exhibits a non-monotonic behaviour, increasing to a maximum of G max ≈ 1.25G n at T m ≈ ∆(T m ) and then decreasing to G n for T > T m .Recently mesoscopic S/N structures have been fabricated in which the limit ∆ >> ǫ T h is realised. In this case Nazarov and Stoof [4] (also see [5][6][7]) argued that the temperature dependence of the conductance G has a similar non-monotonic behaviour with a maximum at a temperature comparable with the Thouless energy, while simultaniously Volkov, Allsopp and Lambert [8] predicted that the voltage dependence of the conductance in an S/N mesoscopic structure (Andreev interferometer) has a similar form with a maximum at eV m ≈ ǫ T h . This non-monotonic behaviour has been observed both in very short S/N contacts [9] and in longer mesoscopic S/N structures [10][11][12]21]. In ref [6] it was noted that the conductance δG = G − G n consists of two contributions. The first, δG DOS , is negative due to a proximity effect induced decrease in the density of states (DOS) of the normal wire which makes contact with a superconducting strip [13]. The other contribution δG MT (positive) is analogous to the Maki-Thompson (MT) contribution to the paraconductivity of S/N/S and N/S/N mesoscopic structures and was calculated in [14]. At T = 0 and V = 0 both contributions to the conductance are equal, as T or V increase the contribution δG MT dominates until a maximum is reached, then both these contributions decay.During the past decade a great deal of interest in the transport properties of N/S n...

We observe a maximum in the conductance of Al/n-GaAs junctions at temperatures 20 mK lower than the superconducting transition temperature (T(c)). This is the first observation of a peak in the conductance near the superconducting transition in superconducting-normal (S/N) junctions. To accommodate this effect we calculate the full temperature dependence of the conductance of these structures, invoking quasiclassical Green's functions in the diffusive limit. In addition to the well-known low-temperature peak at temperatures on the order of the Thouless energy, we find a maximum near T(c). This peak has the same origin as the subgap conductance observed in S/N junctions at low temperatures.

We consider the interaction between a particle beam and a propagating electromagnetic wave in the presence of a metamaterial. We show that the introduction of a metamaterial gives rise to a novel dispersion curve which determines a unique wave particle relationship, via the frequency dependence of the metamaterial and the novel ability of metamaterials to exhibit simultaneous negative permittivity and permeability. Using a modified form of Madey's theorem we find that the novel dispersion of the metamaterial leads to a amplification of the EM wave power.PACS numbers: