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This paper discusses the optimization of the electron flux generated by the interaction of a laser pulse with a shaped gas jet target through numerical simulations in order to formulate experiments for the ultra-high intensity facilities under construction or recently completed. Using such gaseous targets (instead of plasmas created by vaporizing solids using a laser) is a critical step for enabling applications at high repetition rate. The use of gas jets uniquely allows high repetition rates, low debris and relaxed laser contrast operation, thus eliminating the need for replacement of solid targets during experiments requiring high repetition rates. The results obtained reveal that the accelerated electrons can be controlled by target density adjustments. [ABSTRACT FROM AUTHOR]

The necessity to produce superior quality ion and electron beams has been a hot research field due to the advances in laser science in the past decade. This work focuses on the parametric study of different target density profiles in order to determine their effect on the spatial distribution of the accelerated particle beam, the particle maximum energy, and the electromagnetic field characteristics. For the scope of this study, the laser pulse parameters were kept constant, while varying the target parameters. The study continues the work published in [1] and focuses on further studying the effects of target curvature coupled with a cone laser focusing structure. The results show increased particle beam focusing and a significant enhancement in particle maximum energy. [ABSTRACT FROM AUTHOR]

With the latest advances in attainable laser intensity, the need to obtain better quality ion and electron beams has been a major field of research. This paper studies the effects of different target density profiles on the spatial distribution of the accelerated particles, the maximum energies achieved, and the characteristics of the electromagnetic fields using the same laser pulse parameters. The study starts by describing a baseline for a flat target which presents a proton-rich microdot on its backside. The effects of introducing a target curvature and, further on, a cone laser focusing structure are compared with the flat target baseline results. The maximum energy obtained increases when using complex structures, and also a smaller divergence of the ion beam is observed. [ABSTRACT FROM AUTHOR]

We performed a numerical study to observe the influence of the Marangoni convection and external temperature gradient on the temperature and oxygen impurities fluctuations near the solid liquid interface. For this purpose, a 3D numerical model, using the STHAMAS3D software, has been developed for a Cz configuration for 200mm silicon crystals growth. We analyzed the temperature and oxygen impurities fluctuations in a monitor point situated below the solidification interface in two cases: with and without Marangoni convection taken into consideration. Also, we studied the influence of three profiles of the external temperature gradient on the temperature and oxygen fluctuations. Both studies revealed that there is a small dependence of the temperature distribution in the melt near the interface both on the Marangoni convection and on the temperature gradient. The O concentration is more uniformly distributed in the melt if the effects of the Marangoni convection are present and it has a higher value if a smaller external temperature gradient is used. [ABSTRACT FROM AUTHOR]