Development of a High-repetition Rate Tw Co2 Laser Driver for a Compact, Variable Species Ion Source

CO2 laser-driven ion acceleration has been used to generate monoenergetic, MeV proton beams from a gas jet plasma. Use of a gas jet is advantageous because it offers interactions at a density around the critical plasma density for 10 μm pulses (10 cm) and can be run at a repetition rate of 1-100 Hz. This opens the possibility to create a variable species ion source easily switchable from protons to light ions (e.g. He, N and Ne). A TW class high repetition rate CO2 laser driver is required for implementing such a source. At the UCLA Neptune Laboratory we have built a 1 Hz CO2 laser system and demonstrated the amplification of 20 GW, 3 ps laser pulses. However, peak powers on the order of 0.2-1 TW are required for producing ~ MeV proton beams. Here we report progress on an ongoing project in which the peak power of our laser system will be increased by nonlinear chirping and broadening followed by pulse compression. We also discuss a possible strategy for generating 300 mJ, 300 fs CO2 laser pulses for driving a 1 – 10 Hz laboratory ion source.