We propose a new scheme to obtain a compact ultra-bright, high-energy-density gamma ray source by ultra-intense laser interaction with a near-critical-density (NCD) plasmas filled gold cone-capillary. By using the particle-in-cell code EPOCH, it is shown that NCD electrons are accelerated by the laser ponderomotive force in the gold cone and emit strong radiation. Considering the effect of large radiation back-reaction force, some electrons are kicked into the laser field. The trapped electrons oscillate significantly in the transverse direction and emit ultra-bright gamma ray in the forward direction. By attaching a capillary to the gold cone, the trapped electrons are able to keep oscillating for a long distance and the radiation emission can be significantly enhanced. Three-dimensional simulations show that the total gamma photon flux with the photon energy in the range of 3 MeV to 30 MeV is approximately 10(13)/shot, and the corresponding peak brightness is in the order of 1023 photons/s/mm(2)/mrad(2)/0.1% BW. The average energy-density of the radiated gamma photons is about 10(17)J/m(3), which is six orders of magnitude higher than the threshold of high-energy-density physics. The energy conversion efficiency from the laser to the gamma photons is estimated to be about 5% at the irradiation of a laser with intensity similar to 1:37 x 10(22)W/cm(2). (C) 2015 AIP Publishing LLC.
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