Beam characterization of a lab bench cold cathode ultra-soft X-ray generator

Abstract

The aim of this work is to characterize the Ultra Soft X-ray (USX, 1.5keV, Al Kα) photon beam of a customized lab bench cold cathode generator. Within this generator, the electron beam is slowed down in a thin aluminium foil (16μm) supported by an easily exchangeable anode. It is shown that the thickness of the foil and the anode configuration determine the spatial distribution and the fluence rate of the photon beam, whereas accelerating voltage determines both fluence rate and energy spectrum feature. It is shown also that under specific operation parameters (i.e. accelerating voltage), a Gaussian energy distribution of the beam can be generated which is centred on the energy of the Al Kα line (1.5keV). Dosimetric films of GAFCHROMIC® HD-810 were used to estimate the photon fluence rate distribution of the beam. Its variation, when the generator acts as a monoenergetic source, was characterized with the two different configurations of the anode assembly. Finally, it is verified that the anode assembly consisting in a flat washer, on which the aluminium foil is set, acts as a simple point-source.