X-ray photon beams in the keV to MeV energy range are essential to study high energy density (HED) matter and to improve the understanding of inertial confinement fusion and astrophysical systems. HED experiments produce highly transient matter under extreme states of temperatures and pressures and it is essential to develop light sources that are: in the hard x-ray energy range (0.01-1 MeV), directional, high-yield, low-divergence, and short-duration (ps and sub-ps). In this work we show that by using a laser plasma accelerator (LPA) driven by a kJ-ps class laser it is possible to generate a broadband (0.01-1 MeV) hard x-ray source that satisfies the previous requirements. A series of experiments were conducted on the Titan laser at Lawrence Livermore

62,64Cu are radioisotopes of medical interest that can be used for positron emission tomography (PET) imaging. Moreover, 64Cu has β− decay characteristics that allow for targeted radiotherapy of cancer. In the present work, a novel approach to experimentally demonstrate the production of 62,64Cu isotopes from photonuclear reactions is proposed in which large-current laser-based electron (e−) beams are generated from the interaction between sub-petawatt laser pulses and near-critical-density plasmas. According to simulations, at a laser intensity of 3.4 × 1021 W/cm2, a dense e− beam with a total charge of 100 nC can be produced, and this in turn produces bremsstrahlung radiation of the order of 1010 photons per laser shot, in the region of the giant dipole resonance. The bremsstrahlung radiation is guided to a natural Cu target, triggering photonuclear reactions to produce the medical isotopes 62,64Cu. An optimal target geometry is employed to maximize the photoneutron yield, and 62,64Cu with appropriate activities of 0.18 GBq and 0.06 GBq are obtained for irradiation times equal to their respective half-lives multiplied by three. The detection of the characteristic energy for the nuclear transitions of 62, 64Cu is also studied. The results of our calculations support the prospect of producing PET isotopes with gigabecquerel-level activity (equivalent to the required patient dose) using upcoming high-intensity laser facilities.

Enhanced electron-positron (e − e + ) pair production using two obliquely incident lasers interacting with a solid target is investigated through multi-dimensional particle-in-cell (PIC) simulations. Two obliquely incident lasers can strengthen the laser-hole boring effect, which enhances the reflected focusing laser field and the consequent quantum electrodynamics effects. PIC simulations show that by using two 10 PW-scale lasers, a high-yield (3×10 10 ) overdense (∼10 22 cm −3 ) positron beam can be generated and laser to pair energy conversion efficiency can be increased up to one percent. Such positron yield is fifty times higher than that produced from a single laser with the same peak power. The robustness of such a scheme is confirmed by numerically studying parametric influences of the oblique incident angle, temporal asynchrony and phase difference between the two lasers. It is found that the temporal asynchrony and the phase difference have minor effects on the pair production. The proposed scheme may provide great potential for high dense pair plasma generation in experiments with coming approachable high power laser facilities.

We investigate a novel scheme for brilliant attosecond γ-ray emission and high-yield positron production, which is accomplished with an ultra-intense laser pulse incident upon a Nano-Micro array (NMA) with substrate incorporated. This scheme is able to realize effectively electron acceleration and collid ing geometry. Both the γ-ray flash and positron bunch are then generated with high conversion efficiency. At laser intensity of 8 × 10 23 W/cm 2 , ~27% of the laser energy is transferred successfully into the γ-rays, and ~0.7% of the laser energy into the positrons. As a consequence, ultra-short (~440 as) and ultra-brilliant (~10 24 photons s −1 mm −2 mrad −2 per 0.1%BW @ 15 MeV) γ-ray burst, and high-yield (1.48 × 10 11 ) and overdense (~10 22 cm −3 ) positron bunch are generated. We found a sub-linear scaling of laser-to-photon conversion efficiency (∝ 𝐼 0 0.75 ) and a super-linear scaling of laser-to-positron conversion efficiency ( ∝ 𝐼 0 2.5 ) with the laser intensity.Multi-dimensional particle-in-cell simulat ions show that particle (γ photon and positron) generation can be manipulated by laser-focusing position, and NMA's length and spacing.Optimal conditions for particle generation in NMAs are obtained, indicat ing that micro wire array has the advantage over nanowire array in particle generation in the extreme laser fields. Furthermore, positron annihilat ion effect in high-energy-density (HED) environ ment is discussed. The scheme using NMAs would provide effective avenues toward investigating attosecond nuclear science and HED physics with the coming 10 PW laser facilities.

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