Ultra-bright γ-ray emission by using PW laser irradiating solid target obliquely

By using intense laser irradiating a micro plane target obliquely, an
enhanced γ-ray source is generated. Due to the superposition of the incident and the reflected laser pulses, electron bunches with density of ∼ 300nc are extracted and accelerated. When these electron bunches separate from the edge of the target that the laser is leaving, they co-propagate with the laser field and emit dense γ-rays simultaneously. Simulation results show that the emitted γ photons are 253nc dense with an averaged energy of ∼ 12 MeV. The yield of γ photons is ∼ 7×1012, achieving a high brightness of ∼ 4 × 1023 photons=s=mm2=mrad2=0:1%BW. Influences of the laser intensity and the incident angle on the γ-rays emission are discussed. The γ-ray yield, the conversion efficiency from the laser to the γ-rays and the averaged γ-ray energy are increasing when irradiating a higher intensity laser. With the increasing of the incident angle, the peak photon density increases when the angle is smaller than 20◦ and then drops to a stable value, while the divergence decreases when the incident angle is smaller than ∼ 16◦ and then increases.