Abstract
We measure up to positrons per steradian ejected out the back of thick gold targets when illuminated with short () ultraintense () laser pulses. Positrons are produced predominately by the Bethe-Heitler process and have an effective temperature of 2–4 MeV, with the distribution peaking at 4–7 MeV. The angular distribution of the positrons is anisotropic. Modeling based on the measurements indicate the positron density to be , the highest ever created in the laboratory.
- Received 5 September 2008
DOI:https://doi.org/10.1103/PhysRevLett.102.105001
©2009 American Physical Society