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BOREXINO has set new standards in the field of ultra-low background experiments. Such a success was only possible by a strict quality control program during the construction phase of the experiment. In this paper, we describe how construction materials and auxiliary systems of the BOREXINO detector were screened for their residual radioactivity with unprecedented high sensitivity. The highly sensitive assay techniques developed for this purpose were also used to validate the purity of water and nitrogen used in the experiment. Moreover, we report on the production of ²²²Rn-free nitrogen and synthetic air with very low ²²²Rn concentration as well as on the successful search for commercial nitrogen with a particularly low concentration of argon and krypton.

Molecular dynamics study of a binary mixture of inert gases like neon and argon in SPC/E water, with the solute mole fraction of 0.023 have been accomplished at temperatures 288, 293, 298, 303, 308 and 313 K. The solvent–solvent, solute–solute and solute–solvent radial distribution functions have been estimated. The water–water radial distribution function has been found to agree well with the experimental value. Self-diffusion coefficients of both solvent and solutes have been determined by means of respective mean square displacement (MSD) curves using the Einstein's relation. The obtained values for the self-diffusion coefficients of these gases and solvent SPC/E water is found to agree well with available experimental values. The binary diffusion coefficients of these gases in water have then been estimated by using the Darken's relation. The temperature dependence of the diffusion coefficients has also been analyzed. The temperature dependence of estimated values of self-diffusion coefficients of water have been found to obey the Arrhenius relation. Self-diffusion coefficient of neon and argon is found to vary with the temperature according as Arrhenius relation.

In order to investigate the effect of argon introduction on the structural and physical properties of Ba_0.6Sr_0.4TiO₃ (BST) films, epitaxial BST films have been grown by pulsed laser deposition (PLD) on (001) oriented Nb-SrTiO₃ (STON) substrates in the ambient gas of pure oxygen and the mixture of argon and oxygen, respectively. The atomic force microscopy (AFM) reveals that the sample deposited in the mixture of argon and oxygen has a bigger grain size than that deposited in pure oxygen. The dielectric properties of two BST films have been investigated using the Pt/BST/STON parallel plate capacitors. The tunability and the figure of merit (FOM) of the BST film deposited in the mixture gas are about 41% and 7.07 at a DC bias voltage of 8 V at room temperature, which are better than 32% and 4.51, for BST film deposited in pure oxygen. On account of the introduction of argon, the leakage current density of the BST film deposited in the mixture gas has fallen by almost five times, and the leakage current mechanism is both in accordance with ohmic conductive mechanism.

The radio frequency (RF) argon plasma induced surface modification of paper revealed novel surface characteristics and substantially changed surface topography. It was found that RF-argon glow discharge affects surface properties resulting in photo-degradation and chain-scission mechanism on paper network structure. High-power and extended treatment time caused increasing elemental carbon, while decreasing the oxygen concentration on paper surface. However, increased hydroxyls and the creation of new carbonyl functionalities were verified by trifluoroacetoanhydride and pentafluorophenylhydrazine in vapor-phase derivatization reactions.

The second-order optical nonlinearity (SON) of thermally poled fused silica was shown for the first time to be significantly improved by the implantation of multi-energy boron (B) ions, and the outcomes were compared with those obtained from the implantation of multi-energy argon (Ar) ions. Second-harmonic (SH) signals in both samples grew roughly linearly as the poling temperature rose. Samples with Ar implants showed a greater increase in SH signal with rising poling temperature. A qualitative explanation for the formation of ${\chi }^{(2)}$ in poled samples can be found in a model of charge hopping and migration through defects. The diminished SH signal in the B-implanted sample is probably caused by the negative charge trapping layer, as well as by B${}_{2\alpha }$ and E${}^{\prime }$ center defects.

By using the molecular dynamics simulations, the static and dynamic properties of the argon inside the (10, 10), (20, 20) and (40, 40) carbon nanotubes (CNTs) are investigated. Here, the temperatures of 90 K and 298 K are considered to examine the temperature dependence of the concerned properties of the confined argon. The simulation results reveal that there are two clear atomic layers inside the (10, 10) CNTs at the two temperatures. As the diameter of the CNTs increases, the atomic layers become detectable only in the boundary region with the increase in temperature. For the dynamic property, the motion of the argon along the axial direction follows the conventional Fickian diffusion in the most cases, which is very slow in the case of close packing. In the radial direction, the subdiffusion and the Fickian diffusion can only be observed in the initial stage and then the mean squared displacements gradually approach the saturated values. The diffusion coefficients of the confined argon have a consistent tendency with those of the bulk argon after considering the actual reduced density.