How wrong is collisional Monte Carlo modeling of fast electron transport in high-intensity laser-solid interactions?
The interaction of a high-intensity laser with a solid target generates a large current of fast electrons flowing into the target. Due to the large value of the current, the fast electrons generate significant electric and magnetic fields in the target and rapidly heat it to high temperatures. However, these effects were neglected in interpreting x-ray emission experiments, so the details of the fast electron generation that were inferred could be incorrect. This is considered, theoretically, for layered target, Kalpha emission experiments, by using a hybrid Monte Carlo code that includes field generation. The code is used to model such experiments with aluminum and plastic targets, using fast electron parameters taken from experimental results for average intensities of around 10(18) W cm(-2). These numerical results are then interpreted in the same manner as previous experiments, using only the Monte Carlo part of the code. The field generation leads to lower total emission and to an apparent two-temperature fast electron distribution. The laser absorption into fast electrons inferred by Monte Carlo modeling is consistently lower than the actual value. The mean fast electron energy inferred could be either higher or lower than the actual value, depending on the experimental setup and the cone angle and energy distribution used in the Monte Carlo modeling. The errors caused by neglecting the fields are, in general, greater for plastic than aluminum targets, leading to inconsistencies in results obtained by Monte Carlo modeling.
Davies
J R
JR
Instituto Superior Técnico, GoLP, 1049-001 Lisboa, Portugal.