Collimated ultra-bright gamma-rays from electron wiggling along a petawatt-laser-irradiated wire in the QED regime

Even though high-quality X and gamma-rays with photon energy below mega-electron-volt (MeV) are available from large scale X-ray free electron lasers and synchrotron radiation facilities, it remains a great challenge to generate bright gamma-rays over ten MeV. Recently, gamma-rays with energies up to MeV level were observed in Compton scattering experiments based on laser wakefield accelerators, but the yield efficiency was as low as 10−6 , owing to low charge of the electron beam. Here, we propose a scheme to efficiently generate gamma-rays of hundreds of MeV from sub-micrometer wires irradiated by petawatt lasers, where electron accelerating and wiggling are achieved simultaneously. The wiggling is caused by the quasistatic electric and magnetic fields induced around the wire surface, and these are so high that even quantum electrodynamics (QED) effects become significant for gamma-ray generation, although the driving lasers are only at the petawatt level. Our full three-dimensional simulations show that directional, ultra-bright gamma-rays are generated, containing 1012 photons between 5 and 500 MeV within 10 femtosecond duration. The brilliance, up to 1027 photons s−1 mrad−2 mm−2 per 0.1% bandwidth at an average photon energy of 20 MeV, is the second only to X-ray free electron lasers, while the photon energy is 3 orders of magnitude higher than the latter. In addition, the gamma-ray yield efficiency approaches 10%, i.e., 5 orders of magnitude higher than the Compton scattering based on laser wakefield accelerators. Such high-energy, ultra-bright, femtosecond-duration gamma-rays may find applications in nuclear photonics, radiotherapy, and laboratory astrophysics.