Sistemi per la generazione di raggi X da plasma indotto da laser e possibili applicazioni

During the three years of doctorate, the plasma X soft radiation generation system, developed by the Engineering Faculty, Enterprise Engineering Department of the University of Rome "Tor Vergata", has been studied and used from me for numerous applications. Generally a plasma comes created sending focused laser radiation with opportune wavelength λ and intensity I (I ≥ 107W/cm2, where 107W/cm2 it represents the threshold intensity for the plasma generation) on a solid or liquid or gaseous target placed to the inside of a chamber (commonly called X–rays chamber and that works in vacuum) and that has a distance from the focalization lens approximately equal to the focal distance f of the same lens. In the case of the system that we use for the generation of X soft radiation from plasma, the laser source used for the plasma creation is constituted from a solid state Nd:Yag/Glass laser that can emit infrared impulses with wavelength λ = 1064nm, with duration τ = 15ns and with maximum theoretical energy Emax=20J (the maximum effective energy is, instead, equal exactly to the half). The target that we used and on which the laser beam comes focused is a solid target usually constituted from metallic tapes that can rotate on an appropriate mechanical support. With our plasma X soft radiation generation system, it is possible to obtain laser beam intensities on the focal plane of the focalization lens comprised between 1011W/cm2 and 8,49 × 1012W/cm2, with the laser spot dimensions on the target approximately equal to 100µm. This system has been developed for: 1) the survey, the study and the analysis of the X emission spectra from laser induced plasma (X spectroscopy); 2) the microlithography applications in that the X soft radiation is used; 3) X microscopy; 4) the radiographs of biological samples; 5) the use of crystals or of LiF (lithium fluorine) films like X–rays detectors, in order to produce images of samples (as for example test reticulums or biological systems) with elevated spatial resolution that is inferior to the micron (exactly is of the order of 400nm); 6) calibrated measures of energy for the X radiation emitted from a laser induced plasma in the near of a specific wavelength. Moreover, because the laser source plays a fundamental role in the plasma X radiation generation process, we have tried to optimize its performances to the aim to maximize the efficiency of X–rays generation. Finally, always in our laboratories, we are putting to point a laser system for UV ultrashort pulses with wavelength λ = 248nm, with duration τ = 100fs, with energy equal to E = 100mJ and with a repetition frequency of 100Hz, based on a Titanium:Sapphire oscillator in mode locked regime, with which we hope to reach a laser beam intensity on the focal plane at least 1016W/cm2 (in truth, we hope to reach a intensity value of 1018W/cm2 for being able to generate relativistic plasmas) and to obtain a UV – X generation efficiency equal to 10% at least, advanced to that obtainable currently with our Nd:Yag/Glass laser source (inferior to 1%).