High Temperature Nitrogen Plasma Based Ion Implantation (HT-NPBII) has been used to treat the surface of niobium superconducting reentrant cavities, which are part of parametric transducers in a resonant-mass gravitational wave detector. The aim is to enhance the corresponding electrical quality factors (Q-factors) which are closely related with the increase of the sensitivity of the system. In this experiment, the cavities are immersed in plasma and bombarded by energetic nitrogen ions, which are implanted into the surfaces of these heated substrates. The heating temperature of the cavities is controlled during the treatment and its level directly affects the N implantation depth profile due to the diffusion process. Additional tailoring of the nitrogen doping can be performed by the adjustment of the intensity and the duty cycle of the high negative voltage pulses used for ion implantation. For implantations performed at 5 kV /20 µs /300 Hz/ 700 °C, nitrogen atoms occupy interstitial spaces in the crystal lattice of niobium. The treatment of niobium superconducting cavities under these parameters caused the enhancement of two orders of magnitude of respective Q-factors. A set of characterization techniques was performed herein in order to help with the understanding of the underlying mechanism behind this phenomenon.

One of the main objectives of the research program at ETE is devoted to the study of confinement properties in a low aspect ratio tokamak plasma configuration, and to attain this purpose the determination of plasma parameters of the edge region plays an essential role. A Fast Neutral Lithium Beam (FNLB) diagnostics was developed to perform the measurement of the density profile and its fluctuations at the edge of the plasma in ETE. The first light signals were collected after the filling of ETE chamber with He gas (10-4 Torr), where the optimization of this diagnostics was done, to adjust the better point for focalization of the beam and for the optical detection system setup. An extensive study of the variation of the intensity of the light signal with the variation of the gas pressure was carried out. This calibration will be used during shots in ETE to measure the rapidly varying pressure of the pulsed discharge by FNLB technique, a requirement imposed by the use of puff valves for injection of the gas. This paper will also describe the several phases of the development of this diagnostics, discuss the problems occurred and the adopted solutions and show the first measurements of the probing of the edge plasma of ETE with FNLB.