The paper reports on the effects of plasma radial inhomogeneity on the power absorption in a helicon plasma source, which are computationally investigated by the CST Microwave Studio code. RF (13.56 MHz) power deposition was studied using three designs of antennas, namely, the Nagoya type-III, the fractional helix, and the single loop. Argon was used as the plasma working gas at the operating pressure of 15 mTorr. We have focused on the collisional power absorption utilizing WKB approximation to describe the plasma inhomogeneity. The obtained results show that the radial inhomogeneity has different effects on the power absorption at the low and the high magnetic fields. It is found that at low magnetic fields (i.e., B0=0.01 T), there is a specific density (nc) ranging from 5×1018 m−3  to 1×1019 m−3, before and after which the radial inhomogeneity decreases and increases the absorbed power, respectively. On the other hand, at high magnetic fields (i.e., B0=0.1 T), the inhomogeneity has no regular effect on the power absorption in various plasma densities. In addition, for a given plasma density (e.g., n=1018 m−3), as the magnetic field increases, the radial inhomogeneity effect on the power absorption would decrease for the Nagoya type-III and the fractional helix designs. However, for the single loop antenna design, this effect is negligible.

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Vibrations of the slab track system propagated to the environment are estimated for railway tracks in which substructures are made from hot mix asphalt concrete (HMAC) and/or rubber modified asphalt concrete (RMAC). Sensitivity analysis is done to determine the ability of such layers to reduce vibrations with various frequencies, load amplitude and thicknesses of asphalt layers. Different types of substructures i.e. with or without the concrete base layer are used to assess propagated vibrations caused by the moving train. A finite element (FE) model of the ballast-less track substructure is built and the dynamic analysis is performed for various track models with asphalt layers. The FE model is in principle a two-dimensional plane-strain model with the parameters according to the common slab track systems. Ground vibrations i.e. dynamic accelerations are extracted at different recording points around the track with lateral distances 0, 10 and 20m from the loading axis. The outputs of numerical simulations for different substructure models are obtained and the possibilities of vibration reductions by various methods are discussed.

In this paper, neutronic calculations were performed to obtain tritium breeding ratio (TBR) for ITER device using developed helium cooled pebble (HCPB) blanket. The designed blanket module has the following combinations; natural lithium, Li 4 SiO 4 (20 %), beryllium moderator and neutron multiplier. To ensure tritium selfsufficiency, the calculated achievable TBR should be equal to or greater than the required TBR. Simulations have been performed by means of Monte Carlo MCNP-4C code using END/B-VII.1 data library. Results show that TBR of 1.14 is obtained for this new HCPB.

Landau damping is one of the most important mechanisms for the description of wave dissipation and efficient power absorption in helicon plasma sources. Numerical analysis using the MATLAB code is carried out to determine the dispersion relation of the helicon plasma and calculate the axial wavenumber for m = 0 mode in both Trivelpiece-Gould (TG) and helicon plasma density regimes. In addition, the MATLAB code is coupled to the CST Microwave Studio (Ms) code to examine the collisionless power absorption due to Landau damping in a helicon source driven by a single-loop antenna. The effects of some parameters, such as the electron temperature (T e ), the external magnetic field strength (B 0 ), and the antenna excitation frequency (f ), on the Landau damping are investigated for electron density ranging from 1 × 10 16 to 1 × 10 20 m -3 . Our findings indicate that, for a given set of plasma parameters, Landau damping shows different behaviors on the power deposition. For instance, increasing the excitation frequency has considerable effect on the collisionless absorbed power in the range of values from 3 × 10 17 to 3 × 10 19 m -3 of the electron density. Also, for f = 13.56 MHz, T e = 3 eV, and B 0 = 100 G, there is a specific electron density (i.e., n e = 2 × 10 18 m -3 ) beyond which increasing the electron temperature causes a decrease in the collisionless power absorption; the opposite is true for lower plasma density (i.e., n e < 2 × 10 18 m -3 ). Furthermore, the obtained results show that Landau damping has considerable effect on the power absorption in the helicon source at low pressure regime (e.g., P = 1 mTorr) with low external magnetic field strength (e.g., B 0 < 200 G).