In a comprehensive program of environmental radioactivity survey in South Caspian region, (137)Cs inventories in soil has been measured at more than 50 sites in the Iranian northern province of Guilan. This has been the first wide-range survey of soil radionuclide inventories in the narrow band sensitive ecosystem of south Caspian shore. Radioactivity measurements were carried out using HPGe gamma-spectrometry system. The activity concentration of (137)Cs in surface soil exhibits a mean value of 17.6 ± 9.4 Bq kg(-1), with a range of 2.3-41.7 Bq kg(-1). In many sites, split-level sampling method has been applied down to a depth of 20 cm. There were found generally two profiles. Most profiles exhibit a negative exponential distribution, while others revealed a clear subsurface peak in 5-10-cm layer. Cesium deposition in the study area has been estimated to be in the range of 0.38-2.9 kBq m(-2) with a mean value of 1.7 kBq m(-2). Distribution patterns of (137)Cs concentration levels and deposition values have been estimated using Kriging interpolation method. Observed hotspots in deposition pattern coincide with areas of higher precipitation.
We may improve plasma ignition quality in a conically guided proton fast ignition scheme by the application of an extra lower intensity, secondary carbon beam. According to the experimental measurements on the number of laser-accelerated ions, the temporal evolution of the hot spot electron, ion, and radiation temperatures was examined using three-temperature plasma model, in radiation pressure acceleration (RPA) mechanisms for a proton-Carbon beam configuration, E avg ≈ 10 MeV/nucleon. The hot spot ignition was evaluated by the well-known stopping power models proposed independently by Li-Petrasso (LP) and Brown-Preston-Singleton (BPS). Based on our analytical results, with time, plasma temperature in the LP model surpasses the BPS model. From this point of view, to compensate this deficiency in the BPS method, we will show that the density ratio of 17% is required when the energy spread is 10%. The results were also validated by the DEIRA-4 code. Moreover, the electron-ion equilibrium will decrease up to 9.3 and 4.4% for the LP and BPS methods, respectively. It is demonstrated that the key features of a higher average ion energy as well as the narrow beam profile in the RPA regime may effectively ignite hot spot much better than in the Target Normal Sheath Acceleration (TNSA) counterpart. It is estimated that the proton-Carbon beam proposal can reduce ion beam energy to 8.42 kJ, approximately saving 15% of ignitor energy.
K E Y W O R D Sconically guided fast ignition, laser-accelerated ion beam, proton and carbon beam, RPA, TNSA
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