X-Ray tube: Hard X-rays detected by fluorescent screen.

X-Ray tube: Hard X-rays detected by fluorescent screen. In this low-energy X ray tube, a high voltage (about 40 kV pulsating D.C. from an induction coil) is placed across two electrodes. A stream of high speed electrons jumps from the cathode towards the anode and hits a flat metal target, knocking out electrons from the inner shells of the target metal atoms (Fig.1). Electrons from outer shells jump in to fill the vacancies, and in the process emit X rays*. A fluorescent screen with a toy bear (with internal copper wire skeleton) is used to demonstrate the presence of X rays: the screen glows green, and the dark shadow of the skeleton is clearly visible. The apparatus is enclosed in a lead-lined box to protect viewers, and the fluorescent screen is visible through panes of lead plastic. *X rays are also emitted by 'bremsstrahlung'. High-speed electrons decelerate down in the proximity of the nuclei of the target metal atoms and give up their energy in the form of X rays. Cathode e Target - Anode Fig.1 X rays Ref.:Modern College Physics by Harvey White, 6th ed., p. 765-775