Investigating Instabilities of Long, Intense Laser Pulses in Plasma Wakefield Accelerators

Laser wakefield acceleration (LWFA) is a promising method for reducing the cost and size of the state of the art and industrial accelerators. In the recent AE71 experimental campaign at the Brookhaven National Laboratory, a long (4 ps) powerful (300 GW) CO
₂
laser pulse was sent into a hydrogen gas to produce plasma wakefields. We analyzed the evolution of the laser numerically and found three distinct regions: where the laser self-modulates, where it is transversely disrupted, and where it self-channels. The laser disruption process is similar to the hosing instability that occurs in particle-beam-driven plasma wakefield accelerators. Although hosing instability has been well studied for particle-driven acceleration, the similar instability for long laser pulses has not been clearly explained, and a technique to prevent it is still lacking. Our numerical simulations were done with Particle-In-Cell code OSIRIS. Here we show the impact that plasma ionization and laser focal position have on the interaction of the laser with the plasma in the three distinct regions.