Search results for "Rift"
showing 10 items of 526 documents
Electron drift properties in high pressure gaseous xenon
2018
[EN] Gaseous time projection chambers (TPC) are a very attractive detector technology for particle tracking. Characterization of both drift velocity and di¿usion is of great importance to correctly assess their tracking capabilities. NEXT-White is a High Pressure Xenon gas TPC with electroluminescent ampli¿cation, a 1:2 scale model of the future NEXT-100detector, which will be dedicated to neutrinoless double beta decay searches. NEXT-White has been operating at Canfranc Underground Laboratory (LSC) since December2016. The drift parameters have been measured using 83mKr for a range of reduced drift ¿elds at two di¿erent pressure regimes, namely 7.2 bar and 9.1 bar. Theresults have been comp…
A 1D coupled Schrödinger drift-diffusion model including collisions
2005
We consider a one-dimensional coupled stationary Schroedinger drift-diffusion model for quantum semiconductor device simulations. The device domain is decomposed into a part with large quantum effects (quantum zone) and a part where quantum effects are negligible (classical zone). We give boundary conditions at the classic-quantum interface which are current preserving. Collisions within the quantum zone are introduced via a Pauli master equation. To illustrate the validity we apply the model to three resonant tunneling diodes.
The DEPFET based Focal Plane Detectors for MIXS on BepiColombo
2010
X-ray detectors based on arrays of DEPFET macropixels, which consist of a silicon drift detector combined with a detector/amplifier structure DEPFET as readout node, provide a convenient and flexible way to adapt the pixel size of a focal plane detector to the resolving power of any given X-ray optical system. Macropixels combine the traditional benefits of an SDD, like scalability, arbitrary geometry and excellent QE even in the low energy range, with the advantages of DEPFET structures: Charge storage capability, near Fano-limited energy resolution, low power consumption and high speed readout. Being part of the scientific payload of ESA's BepiColombo mission, the MIXS instrument will be …
Self-consistent field theory based molecular dynamics with linear system-size scaling
2012
We present an improved field-theoretic approach to the grand-canonical potential suitable for linear scaling molecular dynamics simulations using forces from self-consistent electronic structure calculations. It is based on an exact decomposition of the grand canonical potential for independent fermions and does neither rely on the ability to localize the orbitals nor that the Hamilton operator is well-conditioned. Hence, this scheme enables highly accurate all-electron linear scaling calculations even for metallic systems. The inherent energy drift of Born-Oppenheimer molecular dynamics simulations, arising from an incomplete convergence of the self-consistent field cycle, is circumvented …
Parametric Excitation of Density Waves in Drifting Electron-Hole Plasmas
1972
The effect of the electronic drift velocity on the conditions for parametric excitation in electron-hole plasmas is investigated in the two-mode approximation using a Vlasov-equations approach. The results show that when the electronic drift velocity approaches the phase velocity of the lower frequency mode of the plasma, a considerable lowering of the threshold for the onset of parametric excitation occurs, thus resulting in more favorable conditions for experimental observation of the process. The dependence of the threshold on other relevant physical parameters involved, such as the electron-to-hole mass and temperature ratios, is also investigated.
Nonlinear nonviscous hydrodynamical models for charge transport in the framework of extended thermodynamic methods
2002
This paper develops a procedure, based on methods of extended thermodynamics, to design nonlinear hydrodynamical models for charge transport in metals or in semiconductors, neglecting viscous phenomena. Models obtained in this way allow the study of the motion of electric charges in the presence of arbitrary external electric fields and may be useful when one wishes to study phenomena in a neighborhood of a stationary nonequilibrium process: indeed, the drift velocity of the charge gas with respect to the crystal lattice is not regarded as a small parameter.
The relaxation-time limit in the quantum hydrodynamic equations for semiconductors
2006
Abstract The relaxation-time limit from the quantum hydrodynamic model to the quantum drift–diffusion equations in R 3 is shown for solutions which are small perturbations of the steady state. The quantum hydrodynamic equations consist of the isentropic Euler equations for the particle density and current density including the quantum Bohm potential and a momentum relaxation term. The momentum equation is highly nonlinear and contains a dispersive term with third-order derivatives. The equations are self-consistently coupled to the Poisson equation for the electrostatic potential. The relaxation-time limit is performed both in the stationary and the transient model. The main assumptions are…
Nonlinear SDE Excited by External Lévy White Noise Processes
2011
A numerical method for approximating the statistics of the solution of nonlinear stochastic systems excited by Gaussian and non-Gaussian external white noises is proposed. The differential equation governing the evolution in time of the characteristic function is resolved by the convolution quadrature method. This approach is especially suited for those problems in which the nonlinear drift term is not of polynomial form. In such cases the equation governing the evolution in time of the characteristic function is not a partial differential equation. Statistics are found by introducing an integral operator of Wiener-Hopf type, called the transformation operator, and applying the Lubich's con…
A novel experimental system for the KDK measurement of the 40K decay scheme relevant for rare event searches
2020
Potassium-40 ($^{40}$K) is a long-lived, naturally occurring radioactive isotope. The decay products are prominent backgrounds for many rare event searches, including those involving NaI-based scintillators. $^{40}$K also plays a role in geochronological dating techniques. The branching ratio of the electron capture directly to the ground state of argon-40 has never been measured, which can cause difficulty in interpreting certain results or can lead to lack of precision depending on the field and analysis technique. The KDK (Potassium (K) Decay (DK)) collaboration is measuring this decay. A composite method has a silicon drift detector with an enriched, thermally deposited $^{40}$K source …
Nonadiabatic spin-transfer torque of magnetic vortex structures in a permalloy square
2014
The stationary displacement of a magnetic vortex core in a permalloy square caused by an ultrahigh direct current has been measured utilizing scanning electron microscopy with polarization analysis. Data have been analyzed for three different generic states of the Landau structure and up to a current density of $3\ifmmode\times\else\texttimes\fi{}{10}^{11}\mathrm{A}/{\mathrm{m}}^{2}$. This procedure allows for separating the effects caused by the Oersted field, the nonadiabatic, and the adiabatic spin-transfer torque. In addition, the spin polarization of the driving current $P=(65\ifmmode\pm\else\textpm\fi{}4)%$ is independently determined from the spin drift velocity of ${v}_{j}=(4.79\ifm…