Gaussian energy distribution of fast ions emitted by laser-produced plasmas

Abstract

The analysis of ion collector signals with the use of a time-of-fight signal function derived from a shifted Maxwell–Boltzmann velocity distribution is used to quantify the ion characteristics as the ion temperature and velocity of centre-of-mass motion of groups of ionized species constituting the ablated plasma. The analysis is also focused on velocity and energy distributions derived from the signal of a time-of-flight detector taking into account the underlying principle of sensor operation. The energy Maxwell spectra of ions are compared with the Gauss distribution with respect to the ratio of the centre-of-mass energy of ions to their temperature. The difference threshold between the Gauss and energy Maxwell spectra is determined via the limited validity of the basic relationship between spreads in energy and time-of-flight spectra ½ΔE/E=Δt/t. The analysis of velocity spectrum of fast ions emitted by Ti plasma produced with 300ps, kJ-class iodine laser operating at PALS facility shows that ion bursts consist of almost monoenergetic ion beams.