Er+ medium energy ion implantation into lithium niobate

Erbium-doped lithium niobate (Er:LiNbO₃) is a prospective photonics component, operating at 1.5 μm, which could find its use chiefly as an optical amplifier or waveguide laser. In this study, we have focused on the properties of the optically active Er:LiNbO₃ layers, which are fabricated by medium energy ion implantation under various experimental conditions. Erbium ions were implanted at energies of 330 and 500 keV with fluences of 1.0 × 10¹⁵, 2.5 × 10¹⁵ and 1.0 × 10¹⁶ cm^?2 into LiNbO₃ single-crystalline cuts of various orientations. The as-implanted samples were annealed in air at 350 °C for 5 h. The depth distribution and diffusion profiles of the implanted Er were measured by Rutherford Backscattering Spectroscopy (RBS) using 2 MeV He⁺ ions. The projected range R_P and projected range straggling ΔR_P were calculated employing the SRIM code. The damage distribution and structural changes were described using the RBS/channelling method. Changes of the lithium concentration depth distribution were studied by Neutron Depth Profiling (NDP). The photoluminescence spectra of the samples were measured to determine whether the emission was in the desired region of 1.5 μm. The obtained data made it possible to reveal the relations between the structural changes of erbium-implanted lithium niobate and its luminescence properties important for photonics applications.     

Problems with the mass spectrometric determination of tritium from cold fusion

Among the attempts to measure particles produced in the cold fusion of deuterium in palladium metal is the mass spectrometric observation of tritium. An experiment which has been reported in the popular press involves attaching a hollow Pd electrode to a vacuum chamber and measuring the tritium produced during electrolysis using a mass spectrometer. We present data demonstrating that mass 5 and 6, which could be mistaken for the ions DT⁺ and T₂ ⁺, can arise from ion-molecule reactions in the ionizer of the mass spectrometer giving the ions HD₂ ⁺ and D₃ ⁺. With H₂ and D₂ present in the vacuum chamber, there are at least eight reactions which lead to these triatomic species, and these may contribute to a complex time and pressure dependence of the signals.     

The definition of damage functions from irradiation test data

This report describes a method of determining irradiation effectiveness of different neutron spectra in causing radiation effects to fuel cladding and reactor structural materials. It involves the definition of a semi-empirical damage function or cross section using measured data from specimens irradiated in thermal and fast test reactor spectra. The damage function is applied to design problems involving irradiation effects to reactor structural and fuel cladding materials to predict the fluence which would produce a specific change in material properties.     

3-D-micro-ERDA microscopy of trace hydrogen distributions in diamond using a 2-D-PSD with event reconstruction

A fast-imaging technique for the total elemental hydrogen concentration distribution is described, which is helpful in the study of its chemistry and dynamics in the diamond system. The micro-scanned Heavy-Ion Elastic Recoil Detection Analysis (HI-ERDA) technique can deliver information on hydrogen distributions in three dimensions. In our system, the count rate is enhanced by use of a 2-D position and energy sensitive detector for the hydrogen recoils. Software geometry collimation and recoil energy rebinning ensure that the increased rate is in fact accompanied by an improvement in effective energy resolution. The system has been used to study the mobility and trapping behaviour of a collimated implant of hydrogen into a pre-damaged natural type IIa diamond sample as well as the mobility and trapping behaviour of collimated implants of hydrogen into diamond, which has not been pre-damaged.     

Microbeam RBS on flat panel displays

We have demonstrated the utility of microbeam-Rutherford BackScattering (μ-RBS) in spatially resolved studies of operational plasma effects on the interior surfaces of plasma flat panel displays manufactured by Photonics Imaging. The experiments were performed at the Sandia Nuclear microprobe using a 2.8 MeV He beam with an average beam spot size of less than 8 μm. The interior surface of the top panes of the flat panels is composed of approximately 800 nm of MgO on top of a 2000 nm thick PbO layer. μ-RBS of sample panels operated under varying conditions measured changes in the surface MgO film thickness due to plasma erosion and redeposition as accurately as ± 1.5 nm. The high accuracy in the MgO thickness measurement was achieved by inferring the MgO thickness from the shift of the Pb front edge in the RBS spectrum. An estimate for the thickness accuracy as a function of the acquired statistics is presented. The surface of the flat panels' bottom panes is also comprised of MgO on top of PbO. However, troughs 100 μm wide by 10 μm deep were partially filled with phosphor and cover the entire width of the surface. This leaves only 100 μm long sections of MgO within the trough exposed. Using μ-RBS, we were able to analyze the surface composition of these regions.     

Overview of R&D at TLK for process and analytical issues on tritium management in breeder blankets of ITER and DEMO

Safe, reliable, and efficient tritium management in the breeder blanket will have to face unprecedented technological challenges. Beside the efficiency for tritium recovery from the breeder blanket (Tritium Extraction (TES) and Coolant Purification Systems (CPS)), the accuracy for tritium tracking between the inner and the outer fuel cycle must also be demonstrated. This paper focuses on the recent R&D carried out at the Tritium Laboratory Karlsruhe to tackle these issues. For ITER, the recently consolidated TES and CPS designs comprise adsorption columns and getter beds operated in semi-continuous mode. Different approaches for the tritium accountancy stage (TAS) have been evaluated. Balancing static (batch-wise gas collection at the TBM outlets and the tritium plant) or dynamic (in/on-line) approaches with respect to the expected analytical performances and integration issues, the first conceptual design of the TAS for EU TBMs is presented. For DEMO, the overall strategy for tritium recovery and tracking has been revisited. The necessity for on-line real-time tritium accountancy and improved process efficiency suggest the use of continuous processes such as permeator and catalytic membrane reactor. The main benefits combining the PERMCAT process with advanced membranes is discussed with respect to process improvements and facilitated accountancy using spectroscopic methods.     

Site occupancy and annealing behavior of helium in high purity copper

High purity copper has been cyclotron-irradiated with alpha particles to inject roughly 200 at ppm helium. Changes in the lattice parameter due to the helium injection and subsequent isochronal annealing are reported and discussed in terms of the site occupancy of atomic helium and precipitation to form bubbles. The results are interpreted in terms of an earlier model in which the injected helium is present as a stable defect consisting of two or more helium atoms in a single vacant lattice site.     

Measurement of the depth distribution of light impurities in first-wall materials: He in Nb

We have measured the concentrations and depth profiles of implanted helium in niobium by a method demonstrated previously with hydrogen and lithium in copper. The three targets, bombarded at room temperature with 10 keV He⁺ at doses of 0.01, 0.16 and 0.98 C/cm⁺, were respectively: unblistered; covered with circular blisters; and marked with “microrelief”, without blisters. The corresponding doses retained in the metal were 0.0076, 0.039 and 0.052 C/cm² (i.e.≈3 × 10²² He atoms/cm³) with a 10% normalization uncertainty. The profile shapes did not change much: in particular we did not observe, as the dose increased, an accumulation near the surface, which is receding by erosion (sputtering, blistering). These results show that a mechanism of helium loss starts operating at a dose ?0.16 C/cm², i.e. before the bursting of blisters (if they burst at all), and it is most effective near the surface.     

Visible light emission from silicon: a quantum effect in highlyporous materials

The authors discuss progress in the control of the luminescent properties of porous silicon and in the understanding of the basic mechanisms which govern the light emission. The main features of porous silicon formation and properties are briefly recalled. The photoluminescence characteristics are reported. It is shown that anodic oxidation of porous silicon is a technique which provides photoluminescent layers with good mechanical properties and enhanced emission efficiency. A model accounting for the quite long measured carrier lifetimes is outlined. The electroluminescence which appears during the anodic oxidation of porous silicon in pure water was studied