Generation of ultracollimated polarized attosecond γ -rays via beam instabilities

Polarized ultrashort high-energy sources of electromagnetic radiation are widely applied in nuclear physics, astrophysics, high-energy physics, etc. However, generation of a feasible and easy-to-deploy source, especially reaching the attosecond scale in the time-domain and MeV energy levels, is still a great challenge. Here, we put forward a method for producing ultracollimated high-brilliance polarized attosecond γ-rays via the interaction of an unpolarized electron beam with a solid-density plasma. As a relativistic electron beam enters a solid-density plasma, it can be modulated into high-density clusters via the self-modulation instability of itself and further into attosecond slices due to its own hosing instability. This is accompanied by the generation of similar pulse-width photon slices via synchrotron radiation. The severe hosing instability breaks symmetry of the excited electromagnetic fields, resulting in net linear polarization of the photon slices, which challenges the conventional perception that interaction of an axially symmetric unpolarized electron beam with a uniform plasma cannot generate radiation with net polarization. This paper provides new ideas for the generation of ultrashort, high-energy pulses with reduced dependence on the ultraintense peak power of the laser pulse.