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In this work the experimental results of an electron beam generated from a Cu photocathode are reported. Anexcimer laser of 222 nm wavelength illuminated the cathode. The electron beam generated got a maximum outputcurrent of 410 mA at 50 kV accelerating voltage. To assess the geometrical beam qualities an emittance meter wasdeveloped. This instrumentation allowed to determine the electron beam characteristics measuring the current directionby small Faraday cups. The emittance values were calculated analysing the beamlet spatial distribution and calculatingthe distribution function containing the 80%, 50% and 10% of total points in the phase space. The correspondingnormalised emittances were 10, 9 and 0.6p mm mrad. The emittance in the zero charge limit was also calculated whichcan be ascribed to the thermal emittance, the plasma e•ect and the surface imperfections. Analysing even 2 ns theFaraday cup pulses, we also measured the time evolution of the emittance on x-axis and y-axis. The values foundincreased as the current intensity increased, while they decreased at the tail of the current demonstrating a residualemittance. Considering a cathode plane surface, we developed a mathematics package for calculating the theoreticalvalue of the emittance. O 2000 Elsevier Science B.V. All rights reserved.PACS: 29.25; 42.55; 41.80Keywords: Electron beam; Emittance; Photocathode

We show that the classical non-abelian pure Chern-Simons action is related in a natural way to completely integrable systems of the Davey-Stewartson hyerarchy, via reductions of the gauge connection in Hermitian spaces and by performing certain gauge choices. The B\"acklund Transformations are interpreted in terms of Chern-Simons equations of motion or, on the other hand, as a consistency condition on the gauge. A mapping with a nonlinear $\sigma$-model is discussed., Comment: 11 pages, Latex

A modified version of the Ishimori model endowed with SU(1,1) symmetry is proposed. Some classes of both rational and biperiodic exact singular solutions are obtained. These solutions are characterized by a topological charge.

The Lie algebra of the symmetry group of the three-wave resonant interaction system in three (or more) space dimensions is shown to be infinite-dimensional and to have the structure of the direct sum of three Kac-Moody-Virasoro u (1) algebras. The symmetry group is obtained and its one- and two-dimensional subgroups are used to perform symmetry reduction. A wide range of new solutions is obtained. The methods presented in this article are applicable to any system of partial differential equations with an infinite-dimensional symmetry group.

The scaling invariant solutions of the three-wave resonant system in one spatial and one temporal dimension satisfy a system of three first-order nonlinear ordinary differential equations. These equations can be reduced to one second-order equation quadratic in the second derivative. This equation is outside the class of equations classified by Painleve and his school. However, it is a special case of an equation recently found to be related via a one-to-one transformation to the Painleve VI equation.

A new recursion operator generating the KP hierarchy is found. Much simpler than the one previously known, it possesses all the good canonical properties and generates the elementary Backlund transformation. This operator naturally suggests a canonical recursion operator in 3+1 dimensions generating a bihamiltonian hierarchy of nonlinear evolution equations, their Backlund transformation and nonlinear superposition principle.