HYDROGENATED TARGETS FOR HIGH ENERGY PROTON GENERATION FROM LASER IRRADIATING IN TNSA REGIME

Lorenzo Torrisi,Jiri Ullschmied,Mariapompea Cutroneo

doi:10.14311/ap.2015.55.0199

Abstract

<p>Polyethylene-based thin targets were irradiated in high vacuum in the TNSA (Target Normal Sheath Acceleration) regime using the PALS laser facility. The plasmais produced in forward direction depending on the laser irradiation conditions, the composition of the target and the geometry. The optical properties of the polymer use nanostructures to increase the laser absorbance. Proton kinetic energies from hundreds keV up to about 3MeV were obtained for optimal conditions enhancing the electric field driving the ion acceleration.</p>

Highlights

One of the objectives of studies of high-intensity lasergenerating plasmas has been to attain high proton acceleration, and the results are becoming competitive with traditional ion acceleration systems
Our measurements of proton production by plasma-laser are conducted at laser intensity of the order of 1016 W/cm2 using laser pulses of 300 ps duration, at 1315 nm wavelength, in order to examine in grater depth the optimization of the composition and the geometry of the target, and even the irradiation conditions for maximizing the proton energy emission using Target Normal Sheath Acceleration (TNSA) regime
The faster protons, which occur during the rapid ascent of the peak at 77 ns, correspond to a kinetic energy of 300 keV and the subsequent faster carbon ions, which occur at about 135 ns, correspond to maximum kinetic energy of about 1.23 MeV

Summary

Introduction

One of the objectives of studies of high-intensity lasergenerating plasmas has been to attain high proton acceleration, and the results are becoming competitive with traditional ion acceleration systems. Proton beam acceleration reaches about 50 MeV using f s lasers, but the yield is low and of the order of 1011 particles/laser shot [3]. Using thick hydrogenated targets, such as polymers, Backward Proton Acceleration (BPA), obtainable at laser intensities of the order of 1015 W/cm, shows the advantages of giving high proton yields and generating a continuum proton current emission using repetitive laser pulses. Using Target Normal Sheath Acceleration (TNSA) regime, at intensities of the order of 1016–1018 W/cm, laser interaction confers higher acceleration and protons may reach energies above 10 MeV. Further proton acceleration can be obtained using the Radiation Pressure Acceleration (RPA) regime, at intensities above 1018 W/cm, at which the ion energies grow significantly but at which protons have high energy spread and low yield emission [6]. The laser absorption increment, permits a great laser energy release to the polymer and to the generated plasma, resulting in higher proton acceleration, as it will be presented and discussed here

Material and methods

Results and Discussion

Conclusions