Versatile apparatus for electron impact ionization experiments at high energies (500 keV)

Abstract

A new high-energy (500 keV) electron–electron coincidence apparatus is described making possible for the first time triply differential cross-section measurements of inner-shell ionization of atoms of a high atomic number. Moreover, the apparatus has also been designed to deliver doubly differential ionization cross sections of the individual shells by using electron–x-ray coincidences as well as noncoincident low background spectra of inelastically scattered electrons. A special feature of the apparatus is the use of electron spectrum analyzers consisting of a nondispersive magnet and a surface barrier detector. Magnetic electron spectrum analyzers consisting of a sector field magnet and a scintillation detector have been built up. Selected measurements on tantalum (Z=73), silver (Z=47), and aluminum (Z=13) target foils are presented.

Relativistic (e, 2e) collisions on atomic inner shells in symmetric geometry

“…The experimental setup used for the measurements is described in detail in a paper of Ruoff et al [8]. Therefore only a short description will be given here.…”

“…The change of the scattering angle is done by means of a microprocessor controlled stepping motor. The same microcomputer allows one to select the desired momentum values and controls the coil currents [8].…”

“…There it was possible to measure the absolute triple differential cross section for K-shell ionisation of atoms with higher atomic numbers (Z = 47 and 73) using an energy-sharing method. These experiments have been continued with improved technical facilities [8] and recently triple differential cross sections have been reported for the K-shell ionisation for silver and gold both in coplanar asymmetric and symmetric geometries [9]. In this paper we report on the extension of the symmetric experiment to copper ( Z = 29).…”

Influence of projectile - nucleus interaction on relativistic electron-impact ionization

“…The study of the dynamics of electron-impact ionization of atoms by electron-electron coincidence (or (e, 2e)) experiments has proved to be a valuable method of investigating the physics of ionization processes (see, for instance, Lahmam-Bennani (1991) and (e, 2e) and Related Processes by Whelan et al (1993)). With the extension of the method into the relativistic energy region (Ruoff et al 1989), the investigation of the ionization process in strong nuclear Coulomb fields became possible (Bonfert et al 1991).…”

A fine-structure selected relativistic (e, 2e) measurement on the subshell of gold

“…The experimental set-up used for the measurement is described in a paper by Ruoff et al (1989). Therefore only a brief description will be given here.…”