The goal of this project is to demonstrate efficient generation of gamma-ray beams and characterize their energy spectra. The emission of MeV photons will be achieved by driving a multi-GigaGauss quasi-static azimuthal magnetic field inside a dense plasma that is rendered transparent by an ultra-high-intensity laser pulse. Plasma electrons serve as a mediator in the conversion of the laser energy into a dense beam of energetic gamma-rays. The confining azimuthal magnetic field facilitates electron energy gain from the laser, while, at the same time, the electron deflections within the magnetic field cause the electrons to emit MeV gamma-rays in the direction of the laser propagation. The extreme magnetic field strength and high electron energy boost the quantum nonlinearity parameter characterizing the photon emission to the level where a single photon can carry an appreciable fraction of the emitting electron’s energy, which ensures high efficiency of gamma-ray emission.

The experiment will provide key insights into physics of extreme magnetic field generation and efficient production of dense gamma-ray beams in laser-irradiated plasmas. Both aspects are critical to probing, in the laboratory, phenomena that are currently accessible only in extreme astrophysical environments. Specifically, the experiment will give insights to creating matter and antimatter from light alone in laboratory by developing an efficient mechanism for creating dense gamma-ray beams. None of the existing photon sources are capable of creating electron-positron pairs through gammagamma collisions due to low photon density in the MeV energy range.

The experiment will use the multi-PW F1 laser. The ability of this laser to reach ultra-high on-target intensity is the key to accessing the desired regime. The experiments will utilize low-mass foam targets to produce a dense plasma whose electron density is well above the classical cutoff density, but below the relativistically adjusted cutoff density for the laser intensities used in the experiments. This choice of target density will enable laser propagation into the plasma.