STUDY OF AN ELECTRON COLD-CATHODE TUBE FOR SOFT-X-RAY SPECTROMETRY

An electron gun for soft x-ray emission spectrometry (< 4 keV) is described. Electrons are produced in a capacitive direct current glow discharge tube working at low pressure. The surface area struck by the electrons is about 2 cm2. The electron energy spectrum has been analyzed with a plane parallel retarding field analyzer as a function of the pressure, the voltage and the current of the discharge tube. It is shown that even at relatively high pressure (1 Pa) most of the high energy electrons flowing out of the tube have an energy close to the operating voltage of the discharge tube. Electron energy results are also correlated to electron induced x-ray emission. It is shown by the measurement of the threshold voltage of x-ray lines and of the induced background intensity that the electron beam coming out of the tube can be considered to have an energy corresponding to the applied voltage.