Unique X-ray emission characteristics from volumetrically heated nanowire array

J.J. ROCCA; C. BARGSTEN; R.C. HOLLINGER; V. N. SHLYAPTSEV; A. PUKHOV; V. KAYMAK; M.G. CAPELUTO; D. KEISS; A. TOWNSEND; A. ROCKWOOD; Y. WANG; S WANG

Conferencia; 57th Annual Meeting of the APS Division of Plasma Physics. Oral Session TO4: X-Ray Sources and Diagnostics; 2015

Highly anisotropic emission of hard X-ray radiation (>>10 keV) is observed when arrays of ordered nanowires (50 nm diameter wires of Au or Ni [1]) are volumetrically heated by normal incidence irradiation with high contrast 50-60 fs laser pulses of relativistic intensity. The annular emission is in contrast with angular distribution of softer X-rays (>>1 KeV) from these targets and with the X-ray radiation emitted by polished flat targets, both of which are nearly isotropic. Model computations that make use the electron energy distribution computed by particle-in-cell simulations show that the unexpected annular distribution of the hard x-rays is the result of bremsstrahlung from fast electrons. Volumetric heating of Au nanowire arrays irradiated with an intensity of 2 x 10 19 W cm-2 is measured to convert laser energy into hv>> 1KeV photons with a record efficiency of extgreater 8 percent into 2pi, creating a bright picosecond X-ray source for applications. [1] M.Purvis et al. Nature Photonics 7, 796 (2013).Bulletin of the American Physical Society 60 (19)APS, New Yorkhttp://absimage.aps.org/image/DPP15/MWS_DPP15-2015-001669.pdf