Comparison of Influence of the Fast Atom Beam and Ion Beam on the Metal Target

A comparative analysis of a fast atom beam and ion beam effect on a metal target in the binary collision model is performed. Irradiation by fast atoms has been shown to more closely correspond to neutron radiation in a nuclear reactor, in terms of the primary knocked-on atom spectrum and the efficiency and mechanism of the radiation defect formation. It was found that upon irradiation by fast carbon atoms with an energy of 0.2-0.3 MeV, the average number of radiation defects in the displacement cascade of one atom is four to five times higher than the calculated values using the SRIM program for ions with the same energy. It is shown that during penetration in the target, the probability of ionization of atoms with energies less than 0.4 MeV is negligible.

Generation of Electron and Fast Atom Beams by a Grid Immersed in Plasma

We present a new method of product processing with beams of accelerated electrons and fast neutral atoms, which are generated by an immersed in plasma grid under a high negative voltage of 5 kV. The electrons appear due to secondary emission from the grid surface provoked by its bombardment with ions accelerated from the plasma. At the gas pressure not exceeding 0.1 Pa the ions with energy of 5 keV reach the grid without collisions in the space charge sheaths near its surface and their current in the grid circuit is by 2-3 times lower than the electron current. At higher pressures accelerated ions due to charge exchange collisions in the sheaths turn into fast neutral atoms leaving the sheaths and forming the beams. With the pressure increasing, the electron beam current diminishes and the current of fast atom beam grows.

Design and Fabrication of Diffractive Light-Collecting Microoptical Device with 1D and 2D Lamellar Grating Structures

This paper presents the optimal design method of diffractive light-collecting microoptical device and its fabrication method by E-beam lithography, fast atom beam etching, and hot-embossing processes. The light-collecting device proposed in the paper is comprised of 9 (3 × 3) blocks of optical elements: 4 blocks of 1D lamellar grating structures, 4 blocks of 2D lamellar grating structures, and a single block of nonpatterned element at the center, which acts for lens to be able to collect the diffracted and transmitted lights from the lamellar grating structures into the focus area. The overall size of the light-collecting device is 300 × 300 μm2, and the size of each block was practically designed as 100 × 100 μm2. The performance of 1D and 2D lamellar grating structures was characterized in terms of diffraction efficiency and diffraction angle using a rigorous coupled-wave analysis (RCWA) method, and those geometric parameters, depth, pitch, and orientation, were optimized to achieve a high light-collecting efficiency. The master molds for the optimized structures were fabricated on Si substrate by E-beam lithography and fast atom beam etching processes. The 100 μm thick patterned polymethyl methacrylate (PMMA) film was then replicated by a hot-embossing process. As a result, the patterned PMMA film collected 63.0% more incident light than a nonpatterned one.