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An overview of the recent operations and the main results of cesium injection in the Source for the Production of Ions of Deuterium Extracted from Rf plasma (SPIDER) negative ion source are described in this contribution. In experiments without cesium injection, all SPIDER plants were tested to verify the basic expectations on the operational parameters (e.g., electron cooling effectiveness of magnetic filter field) and to determine its operational region. For beam properties, it was shown that the current density varies across the beam in the vertical direction. In preliminary cesium experiments, the expected increase of negative ion current and simultaneous decrease of co-extracted electrons were found, along with the influence of the control parameters (polarization of the plasma electrodes, magnetic filter field) on the SPIDER beam uniformity in the horizontal and vertical directions. It was shown that non-Gaussian tails can be identified in the angular distribution on the plane perpendicular to the beam propagation direction. Stray particles, nonhomogeneous beam and large divergence might result in unexpected heat and particle loads over ITER neutral beam injector (NBI) accelerator grids; it is the goal of SPIDER to assess and possibly to identify suitable methods for controlling these beam features. A major shutdown, planned for late 2021, to solve the issues identified during the operation and to carry out scheduled modifications, is outlined. Such improvements are expected to allow SPIDER to pursue the ITER requirements in terms of negative ion current, electron-to-ion ratio, and beam duration.

A utility program has been written which locates variables in BASIC programs. The program can be used to list the lines where a variable appears, and it can also be used to avoid GOTO bugs when deleting a line. The program itself is in BASIC and is listed. It can be easily modified for special cases.

The electroless deposition of silver on Hydrogen terminated Silicon (100) substrates has been investigated with 2.0 MeV He+ions Rutherford backscattering measurements and electron microscopy observations for 1 mM and 5 mM AgNO3solutions. The RBS analyzes provide the amount of deposited Ag atoms as a function of the immersion time (1 s-160 s), the particle size and density are given by electron microscopy. A nuclei density in excess of 1011cm−2was instantaneously generated. The amount of deposited Ag increases with the square root of the immersion time, following the Cottrell equation, for the 1 s-5 s interval. A diffusion coefficient of about 2 × 10−5cm2s−1for the Ag ions in the solution fits the experimental data. At longer deposition times the Ag ions flux is constant and the diffusion is governed by a static boundary layer few hundred microns thick. With increasing deposition time the particles density decreases of about a factor two. Experiments indicate that clusters dissolution occurs mainly through Ostwald ripening. The cluster radius growth follows a time dependence as tαwith α equal to 0.24 for 1 mM and 0.33 for 5 mM solution respectively, i.e. it is mainly planar (1D) diffusion governed although Ostwald ripening, aggregation and coalescence effects should be considered too.

Electroless silver deposition (for 1–100s) has been simultaneously performed on (100) and (111) planes of macro and micro patterned silicon, fabricated using optical lithography and anisotropic etching with alkaline solution. Metal clusters formation occurs preferentially on the upper edge region separating the two main planes. Their density and mean size are higher on the (100) plane. Similar experiments performed on same patterned samples but with the surface amorphized by ion implantation elucidated the role played by the preferential mass transport caused by the pattern geometry. For the micro-sized pyramidal holes, the non uniform surface distribution of metal clusters is enhanced. The metal deposition occurs mainly on the (100) top strips surrounding the pyramids. The subsequent preferential oxidation of silicon under the metallic clusters gives rise to nanowires of (100) and (111) orientation in the macro and to nanopillars in the micro patterns respectively. Nanowire's tips are preferentially sites for metal deposition as shown after re-immersion in the plating solution. Samples with contiguous one dimensional nanostructures of different orientation could be used for the study of transport properties’ anisotropy. The formation of metal tips on top of the nanostructures might be of relevance in the field of metal-semiconductor contacts.

A systematic study of silver-catalyzed etching in (100) and (111) n-type Silicon substrates is carried out by varying the amount and the morphology of electroless deposited silver clusters. Deposition rate is very fast during the first few seconds and then it levels at a lower value of one order magnitude for both oriented wafers. For small and well separated clusters the Si nanowires formed by the etching are aligned along the (100) axes, while for large and interconnected they are oriented along the normal to the surface. For the (100) Si substrate partially covered with small silver clusters the etching proceeds both in vertical and horizontal [100] directions. For larger coverage (70%) the Ag nanoparticles sink all together along the vertical direction. For the (111) Si substrate, when the Ag nanoparticles are isolated they sink in all the equivalent [100] directions with an irregular path; when the Ag nanoparticles begin to coalesce uniform domains of Si nanowires aligned along [100] directions are formed. When the silver clusters are well interconnected (70% of coverage), the etching is vertical. Silver coverage is then another experimental parameter to induce a preferred orientation of the etched Si nanowires.