Nuclear and particle radiation source

Particle-in-cell simulations suggest that the interaction of a laser pulse of 5 x 1024 W/cm2 with a thin metallic target could produce GeV proton beams. Pulses of protons with GeV energies can be used to induce and investigate nuclear spallation reactions.

Beams of GeV protons and several hundred MeV gammas can be used to produce pions. At rest pions have a lifetime of 20 ns. However the possibility exists to use a laser plasma accelerator (over picoseconds timescale) to accelerate pions to increase their energy and lifetime. In turn high energy pions decay to produce a source of muons and neutrinos.

The development of HiPER will also enable the study of electron-positron plasmas in the laboratory. At laser intensities about 2 x 1018 W/cm2 the electron quiver energy in the laser field exceeds it’s rest mass energy and superthermal electrons are produced. These relativistic electrons can produce electron-positron pairs via the Bethe-Heitler and trident processes when interacting with high-Z ions. Experiments performed using a petawatt laser at the Lawrence Livermore National Laboratory have demonstrated electron-positron pair production. Simulations with particle-in-cell (PIC) codes have shown that in principle pair densities as high as 10-3 of the background electron density is possible when focusing petawatt class lasers of sufficient duration onto a gold target. The HiPER 70 kJ laser of 10 ps pulse duration illuminating a single gold target would in principle produce copious numbers of electron positron pairs, which when the laser radiation is turned off, will expand much quicker than heavier ions, creating a pair fireball.

Thermonuclear yields due to target implosion can be used to study astrophysical nucleosynthesis processes. Furthermore, high flux bursts of neutrons will be produced in the nuclear burn. These short pulses of neutrons can be used for neutron scattering research, radioisotope production, fundamental physics research, radiography and activation analysis.