An X-Ray Micro-Beam Technique: II - A High Intensity X-Ray Generator

Abstract

A high intensity X-ray generator has been constructed which combines the use of small foci and a rotating anode. Improvements in target loading per unit area of about fifty times compared with ordinary stationary target tubes* have been obtained Any width of focus between about 1 mm and 50 μ can be produced by means of an adjustable, biased electron gun. A detailed experimental investigation of the focusing properties of the high voltage gun has been made, the conditions for obtaining small foci and maximum current are derived. The magnitude of the negative bias is found to be the most important factor controlling the focusing action of the electron gun The effect of bias on focal structure is discussed for several types of filament, and is explained on the basis of suppression of emission from different parts of the filaments.