Manipulation of laser-accelerated proton beam profiles by nanostructured and microstructured targets

L Giuffrida,T Wiste,V Scuderi,G Milluzzo,A Picciotto,P Lutoslawski,M Crivellari,G Korn,D Margarone,P Bellutti,Alvise Bagolini ,G.a.p Cirrone ,Anders Persson ,Jan Kaufman ,Arkady Gonoskov ,Joel Magnusson ,Malay Dalui ,Henrik Ekerfelt ,Claes‐Göran Wahlström ,Krister Svensson ,I Gallardo González ,J Pšikal ,Olle Lundh ,T Laštovička

doi:10.1103/physrevaccelbeams.20.081301

Abstract

Nanostructured and microstructured thin foils have been fabricated and used experimentally as targets to manipulate the spatial profile of proton bunches accelerated through the interaction with high intensity laser pulses (6 x 1019 W/cm(2)). Monolayers of polystyrene nanospheres were placed on the rear surfaces of thin plastic targets to improve the spatial homogeneity of the accelerated proton beams. Moreover, thin targets with grating structures of various configurations on their rear sides were used tomodify the proton beam divergence. Experimental results are presented, discussed, and supported by 3D particle-in-cell numerical simulations.

Highlights

Table-top laser systems, using the chirped-pulse amplification (CPA) technique, which were developed in the last decades, are able to reach ultrahigh intensities through the generation of femtosecond laser pulses [1], offering new possibilities in the study of relativistic laser-matter interactions [2,3]
Laser-accelerated protons by introducing grating microstructures on the target front surface [19]. We have extended these previous investigations by a study where the spatial profile of the proton beam is manipulated, both in terms of divergence and spatial homogeneity, by introducing nanospheres or μm-sized grating structures on the rear side of the target
Nanospheres covering the rear surface of a flat plastic foil affect the final proton beam spatial profile in terms of beam divergence and homogeneity, such that it has a larger divergence and a more homogeneous spatial distribution compared to a proton beam emerging from a flat plastic foil of equivalent total thickness

Summary

Introduction

Table-top laser systems, using the chirped-pulse amplification (CPA) technique, which were developed in the last decades, are able to reach ultrahigh intensities (above 1018 W=cm2) through the generation of femtosecond laser pulses [1], offering new possibilities in the study of relativistic laser-matter interactions [2,3]. Laser-driven ion acceleration is one of the most promising and intensively investigated research topics [4], where target normal sheath acceleration (TNSA) is the experimentally most investigated technique. TNSA is based on the relativistic interaction of a thin target and an intense laser pulse and can be used to accelerate protons to several tens of MeV [5,6,7,8]. A significant part of the laser pulse energy is absorbed and heats the plasma electrons which subsequently propagate through the target. As these hot electrons exit the rear of the target, they set up very strong electrostatic sheath fields that ionize atoms and molecules present on the target rear surface.

Methods

Results

Conclusion