Studies of Characteristic and Bremsstrahlung Radiations Emitted from Some Thick Targets by Impact of keV Electrons

Abstract

newline In the present thesis, we have investigated the study of energetic electrons colliding with some solid targets. As a consequence of collision processes, the charged species and radiations may be generated. The emitted radiation considered here is in the form of X-ray photons. The X-rays are mainly of two types, namely, the characteristic (CS) and the non-characteristic or continuous, aptly called bremsstrahlung (BS). The characteristic part of the X-ray spectrum is due to the decay of inner-shell vacancies created in the collisions, while the non-characteristic or continuous radiation is caused due to deceleration of the incident electrons in the Coulomb field of the target atoms. X-rays have several peculiar properties, like, short wavelength and high penetrating ability. The applications of X-rays can be found in industrial as well as in various scientific fields, for instance, in astronomy, astrophysics, plasma physics, medical sciences etc. In a solid target consisting of a large number of atoms, the projectile electrons suffer multiple collisions inside the target and they follow a random trajectory. There are two significant ionization mechanisms, namely, direct electron impact and an indirect process involving the photoelectric absorption of radiation from the continuous and characteristic X-ray spectra. The electrons may emit X-rays and secondary electrons after each interaction with atoms of the target. These X-rays and secondary electrons are free to move randomly inside the target and interact with the other atoms and as a result a secondary process occurs. The produced BS (or CS) X-ray photons inside the target have enough energy to create an inner shell vacancy in the atom; they may get photo-electrically absorbed inside the target and produce indirect characteristic X-rays. In view of different processes that occur in energetic electron-solid target collisions, we felt it necessary to make investigations, so far much less studied, on impact energy and angular dependence of induced X-rays produced from some thick targets of pure elements (Z=22, 29 and 72) in the present work.