Target material dependence of positron generation from high intensity laser-matter interactions

• Published in: Physics of plasmas Vol. 23; no. 12
• Main Authors: Williams, G. J., Barnak, D., Fiksel, G., Hazi, A., Kerr, S., Krauland, C., Link, A., Manuel, M. J.-E., Nagel, S. R., Park, J., Peebles, J., Pollock, B. B., Beg, F. N., Betti, R., Chen, Hui
• Format: Journal Article
• Language: English
• Published: 01.12.2016
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/1.4971235

The effective scaling of positron-electron pair production by direct, ultraintense laser-matter interaction is investigated for a range of target materials and thicknesses. An axial magnetic field, acting as a focusing lens, was employed to measure positron signals for targets with atomic numbers as low as copper (Z = 29). The pair production yield was found to be consistent with the Bethe-Heitler mechanism, where the number of positrons emitted into a 1 steradian cone angle from the target rear was found to be proportional to Z 2. The unexpectedly low scaling results from Coulomb collisions that act to stop or scatter positrons into high angles. Monte Carlo simulations support the experimental results, providing a comprehensive power-law scaling relationship for all elemental materials and densities.