Search Results (4 total)

In SOLEIL, 5 solid state amplifiers provide the required rf power at 352  MHz: 1×35  kW in the booster and 4×190  kW in the storage ring. They consist in a combination of a large number of 330 W elementary modules (1×147 in the booster and 4×724 in the storage ring), based on a design developed in-house, with MOSFETs (metal-oxide-semiconductor field-effect transistors), integrated circulators, and individual power supplies. Although quite innovative and challenging for the required power range, this technology is very attractive and presents significant advantages as compared to the more conventional vacuum tubes, klystrons, or inductive output tubes (IOTs). The booster and two of the storage ring power plants have been successfully commissioned and the first operational experience is quite satisfactory. The amplifiers proved to be very reliable as well as easy and flexible in operation; they have not been responsible for any beam time loss.

The influence of Lorentz- and CPT-violating terms of the extended standard model on a semiclassical two-level system is analyzed. It is shown that the Lorentz-violating background (when coupled with the fermion sector in a vector way) is able to induce modifications on the Rabi oscillation pattern, promoting sensitive modulations on the usual oscillations. As for the term involving the coefficient coupled in an axial vector way, it brings about oscillations both on energy states and on the spin states (implied by the background). It is also seen that such backgrounds are able to yield state oscillations even in the absence of the electromagnetic field. The foreseen effects are used to establish upper bounds on the Lorentz-violating coefficients.

This paper addresses the training of network models from data produced by systems with symmetry properties. It is argued that although general networks are global approximators, in practice some properties such as symmetry are very hard to learn from data. In order to guarantee that the final network will be symmetrical, constraints are developed for two types of models, namely, the multilayer perceptron (MLP) network and the radial basis function (RBF) network. In global modeling problems it becomes crucial to impose conditions for symmetry in order to stand a chance of reproducing symmetry-related phenomena. Sufficient conditions are given for MLP and RBF networks to have a set of fixed points that are symmetrical with respect to the origin of the phase space. In the case of MLP networks such conditions reduce to the absence of bias parameters and the requirement of odd activation functions. This turns out to be important from a dynamical point of view since some phenomena are only observed in the context of symmetry, which is not a structurally stable property. The results are illustrated using bench systems that display symmetry, such as the Duffing-Ueda oscillator and the Lorenz system.

In this paper we reexamine the one-dimensional interaction of electromagnetic and ion acoustic waves in a plasma. Our model is similar to one solved by Rao et al. [Phys. Fluids 26, 2488 (1983)] under a number of analytical approximations. Here we perform a numerical investigation to examine the stability of the model. We find that for slightly overdense plasmas, the propagation of stable solitary modes can occur in an adiabatic regime where the ion acoustic electric-field potential is enslaved to the electromagnetic field of a laser. However, if the laser intensity or plasma density increases or the laser frequency decreases, the adiabatic regime loses stability via a transition to chaos. Different asymptotic states are attained when the adiabatic regime no longer exists. In these states the plasma becomes rarefied and the laser field tends to behave like a vacuum field.