Laser Ionized Plasma Sources for Plasma Wakefield Accelerators

Plasma wakefield accelerators (PWF A) have demonstrated GeV/m scale accelerating gradients; however, current PWFAs tend to increase the particle beam's emittance (volume of the beam in transverse phase-space) as the beam propagates through the plasma. The beam's emittance can be preserved by tailoring the longitudinal density profile of the plasma to properly focus the beam into the plasma. We present optical techniques to create controlled plasma densities via laser ionization. The longitudinal plasma density profile is determined by the evolution of the intensity of a high power laser pulse as it propagates through a gas. Control of the pulse intensity is achieved using a superposition of Bessel beams created by a tandem lens setup. The width of the plasma is limited by the refraction of the laser pulse off of the ionizing gas, but we have developed several optical techniques to create wider plasmas. Our simulations show that suitable plasma filaments with lengths up to a meter and widths up to a millimeter can be generated in an argon gas using a~ 1 0 TW peak-power Ti:sa laser pulse.