Efficient Picosecond X-Ray Sources Generated by Highly Relativistic Irradiation of Vertically Aligned Nanostructures

R.C. HOLLINGER; C. CALVI; A. ROCKWOOD; J.J. ROCCA; A. PUKHOV; A. MOREAU; Y. WONG; A. CURTIS; V.N. SHLYAPTSEV; S. WONG; M.G. CAPELUTO; H. SONG; V. KAYMAK

Conferencia; International Conference on Plasma Science; 2018

The irradiation of high aspect ratio, vertically alignednanoscale rods with ultrahigh contrast (>1012), femtosecondlaser pulses at highly relativistic intensities (>1021Wcm-2)provides a unique combination of drastically enhanced lightpenetration deep into the near solid density target. Thisresults in the material being volumetrically heated to depthstwo orders of magnitude greater than the skin depth of thematerial, creating a large volume, ultrahigh energy density(>109Jcm-3) plasma1. Time integrated spectroscopicmeasurements of Au and Ni nanowire plasmas at an intensityof 5x1018Wcm-2(ao = 1) demonstrated the creation of multikeV, near solid density plasmas ionized to the Au52+ and Ni26+charge states2. The radiative lifetime of these plasmas issignificantly decreased due to their high electron densitywhile their hydrodynamic expansion time is greatly increaseddue to their large size. The result is a large increase in theconversion of the optical laser light into hv >1keV x-rays.Previously, the conversion efficiency has been shown to exceed 20% into 4 pi steradians when irradiating 80nm diameter, 12% of solid density, Au nanowires at an intensity of 4x1019Wcm-2 3 . Here we present the first results of Au nanowires irradiated at highly relativistic intensity of 5x1021Wcm-2corresponding to ao=17. Results of experiments conducted with a variety of nanowire diameters and at various fractions of solid density will be presented and compared to the results of particle in cell simulations.