Monte-Carlo Simulation and Measurements of Electrons, Positrons, and Gamma-rays Generated by Laser-Solid Interactions

Alexander Henderson, Rice University, Texas

Friday September 25, 2015, 11:00 a.m.

SERF, Room 329


ABSTRACT: Lasers have grown more powerful in recent years, opening up new frontiers in physics. From earlyintensities of less than 1010 W/cm2, lasers can now achieve intensities over 1021 W/cm2. The pair production efficiency is equal to or greater than that of linear accelerators, the most common method of antimatter generation in the past. The gamma-rays and electrons produced can be highly collimated, making these interactions of interest for beam generation. Monte-Carlo simulation has long been used in physics for simulating various particle and radiation processes, and is well-suited to simulating both electromagnetic cascades resulting from laser-solid interactions and the response of electron/positron spectrometers and gamma-ray detectors. We have used GEANT4 Monte-Carlo simulation to design and calibrate charged-particle spectrometers using permanent magnets as well as a Forward Compton Electron Spectrometer to measure gamma-rays of higher energies than have previously been achieved. We have had some success simulating and measuring high positron and gamma-rays yields from lasersolid interactions using gold target at the Texas Petawatt Laser (TPW). We have also developed a new method for measuring the yield and angular distribution of gamma-rays using a two-dimensional dosimeter array. In our experiments, we measured narrow energy-band positrons and electrons which have potential medical uses. In addition, the gamma-rays produced by our experiments could be useful for photo-nuclear reactors and homeland security purposes. In this work, we examine these results as well as the physical processes behind them.

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