Cold electrons acceleration in TNSA laser‐generated plasma using a low‐contrast fs laser

Abstract

The fs laser facility in Bordeaux, delivering an intensity of 10 18 W/cm 2 at normal incidence on thin foils, has been used to induce forward electron and ion acceleration in target-normal-sheath-acceleration (TNSA) regime. Micrometric thin foils with different composition, thickness, and electron density, were prepared to promote the charge particle acceleration in the forward direction. The plasma electron and ion emission monitoring were performed on-line using SiC semiconductor detectors in time-of-flight (TOF) configuration and gaf-chromics films both covered by thin absorber filters. The experiment has permitted to accelerate electrons and protons. A special attention was placed to detect relativistic hot electrons escaping from the plasma and cold electrons returning to the target position. The electron energies of the order of 100 keV and of about 1 keV were detected as representative of hot and cold electrons, respectively. A high cold electron contribution was measured using low-contrast fs laser, while it is less evident using high-contrast fs lasers. The charge particle acceleration depends on the laser parameters, irradiation conditions, and target properties, as will be presented and discussed.

SiC, Si and diamond detectors for comparison of laser-generated plasma in TNSA regime

“…It shows a net photopeak with an intensity Y(Cu)=17 V, a value between that detected irradiating Al and Au, indicating that the X-ray plasma emission is proportional to the atomic number of the irradiated target, according to the literature. The photopeak is followed by narrow peaks probably due to backscattered photons or fast electrons from the chamber walls [33]. Successively the TOF timescale shows the proton peak with a maximum kinetic energy of about 790 keV and a large carbon ion peak, due to the different contribution of the different ion charge state, which maximum one has an energy of about 4.6 MeV, corresponding to about six times the proton energy, according to the CBS theory of ion acceleration proportional to the charge state [23].…”

SixMeVproton acceleration from plasma generated by high‐intensity laser using advanced thin polyethylene targets

“…In this way, fusion energy using inertial confinement can be studied and innovative neutron sources can be developed to be well controlled in yield and in switching on and off via the laser source. [9,10] In many other fields, the plasma-produced X-rays and protons can be used to induce characteristic fluorescence emission as a probe for elemental recognition or as a beam for X-ray microscopy, as recently demonstrated. [11,12] Hot and dense plasma can be produced in forward and backward directions, especially if the target is not too thin.…”