Mikhail A. Monastyrski

500-fs photoelectron gun for time-resolved electron diffraction experiments

A photoelectron gun as a source of a photoinduced, monoen- ergetic (energy spread ,0.5 eV), well-collimated (divergence ,0.5 deg), sharp (diameter ,0.7 mm at the 1/e level), and ultrashort (<500 fs) bunch of electrons to be used for time-resolved electron diffraction (TRED) experiments is computer designed, assembled, and tested. In single-shot mode, it generates up to 10 3 of 30 keV electrons, and the electron pulse can be either measured in streak mode or focused onto a solid state target chosen from a set of interchangeable targets. High temporal resolution enables measurement with femtosecond precision of the diffraction pattern perturbation after the exiting laser radiation drops onto a target. Demonstration experiments with a 300-A A1 target in transmission-type mode result in diffraction images of reasonable quality under accumulation of up to 4310 4 500-fs photoelectron pulses.

Dynamics of electron bunches in subpicosecond streak tubes

Abstract The dynamics of electron bunches in subpicosecond streak tubes is studied numerically taking into account space-charge effects and various initial photoelectron energy distributions. Three computing and analytical models (aberrational-Lorentz model, the model describing the limiting case of zero initial energy and simplified analytical model) are used.

The New Streak Image Tube PIF-01

A new, small-size image-converter tube type PIF-01 has been developed for recording of various high speed phenomena with subpicosecond time resolution. The designing goal of the new image-converter tube having four electrodes geometry (photocathode, acceleration mesh, focusing electrode, anode diaphragm) and incorporating with a modern deflection system, was to simultaneously improve temporal resolution and dynamic range.Preliminary experimental results confirm the efficiency of the software developed for picofemtosecond streak tube computation and optimization.

Theoretical and computer study on the possibility of sub- femtosecond (attosecond) temporal focusing of photoelectron probing bunches with quasi-stationary electromagnetic fields

The problem of ideal first-order temporal focusing of photoelectron bunches with quasi-stationary electromagnetic fields is discussed on the basis of theoretical electron optics and computer modelling.

Formation of subfemtosecond photoelectron bunches in time-dependent electric fields

In the paper new theoretical aspects of temporal focusing of photoelectron bunch in time-dependent fields are elucidated. The results of computer modeling on electron-optical system with combined time-dependent eletric and static magnetic fields which ensure both spatial focusing of the bunch and its temporal compressing up to the sub-femtosecond level are presented.

A grid photocathode free of the first-order temporal chromatic aberration

The paper is devoted to the problem of temporal resolution in electron-optical streak tubes intended for ultrafast processes investigation. The temporal threshold of about 150-200 femtoseconds can be hardly overcome without a principally new approach to the design of electron-optical scheme of such tubes. One of the possibilities, namely the use of a photocathode having rather fine grid structure, is numerically analyzed on the basis of 3D field calculations.

Electrodynamics and electron optics of slow-wave comb structures

Abstract Electrodynamic and electron-optical properties of periodic slow-wave structures are calculated by finite-difference methods. It includes direct numerical determination of Laplacian eigenvalues and eigenfunctions which satisfy certain boundary conditions, and electron trajectories calculation based on aberration theory. Test calculations of the comb structure are carried out and its deflection properties are studied. It is shown that maximum deflection sensitivity is reached when the electron beam and wave-phase velocities are approximately equal but do not coincide. The obtained results give the approach to numerical calculation of more sophisticated three-dimensional periodic slow-wave structures.

Comparative analysis of two approaches to image tube computation

Two different approaches to image tube computation, numerical optimization and design being developed in GPI (Russia) and BIT (China) are presented and comparatively discussed as applied to a Russian-made streak image tube.

Iterative solution to the self-consistent problem of an electron gun with an arbitrarily shaped cathode based on combined finite difference: an integral equation approach

A new approach to solve the self-consistent problem for electron gun with arbitrary-shaped cathode is suggested. The main feature of the approach is that the most effective numerical techniques of charged particle optics, namely finite-difference and integral equation methods for field calculation on the one hand, and direct ray-tracing and aberration analysis for trajectory calculation on the other, are integrated within a versatile iterative procedure. Some testing problems are considered and analysed in details.

Computer design of modern streak tubes

Streak tubes design in General Physics Institute of Russian Academy of Sciences is traditionally supported by computer modeling. Numerical examples which illustrate the main phases of electron image formation inside such tubes are presented and discussed in this paper. Some factors resulting in spatial and temporal resolution decrease are examined in details. These factors include various geometric and chromatic aberrations of electron-optical focusing system, dynamic aberrations of deflection system, temporal instrumental function broadening due to Coulomb interaction effects inside the electron beam. Contribution of photoelectrons spread in energy and angles to spatial and temporal resolution is also studied for various photocathode types and streak speeds.