Proton Fast Ignition as a path to commercial fusion energy

Among possible approaches to fusion energy, we regard the Proton Fast Ignition (PFI) as the most credible. PFI as an alternate route to ignition was triggered by the discovery of ultra-bright beams of protons produced by ultra-intense lasers.

Protons are advantageous to other ion species and electrons. Because of their highest ionic charge-to-mass ratio, they are accelerated most efficiently up to the highest energies. They can penetrate deep into a target to reach the high-density region, where the hot spot is to be formed. And they exhibit a characteristic maximum energy deposition at the end of their range, desirable to heat a localized volume. Thus, Focused Energy Inc. has chosen PFI for the primary pathway to fusion energy.

We discuss different ignition scenarios with respect to their applicability for Inertial Fusion Energy (IFE). Focused Energy has chosen the target-normal sheath acceleration (TNSA) ion acceleration mechanism as the most carefully studied one. The required pulse duration of a few ps eases the burden on the driving lasers. TNSA has been demonstrated to exhibit good conversion efficiency and excellent beam focusing capability. The overlap of multiple, ps high energy lasers can further enhance the efficiency and beam quality. We summarize the recent results and discuss the individual aspects that have led us to choose PFI as our path for IFE.