First hydrogen operation of NIO1: Characterization of the source plasma by means of an optical emission spectroscopy diagnostic

Abstract

NIO1 (Negative Ion Optimization 1) is a compact and flexible radio frequency H(-) ion source, developed by Consorzio RFX and INFN-LNL. The aim of the experimentation on NIO1 is the optimization of both the production of negative ions and their extraction and beam optics. In the initial phase of its commissioning, NIO1 was operated with nitrogen, but now the source is regularly operated also with hydrogen. To evaluate the source performances, an optical emission spectroscopy diagnostic was installed. The system includes a low resolution spectrometer in the spectral range of 300-850 nm and a high resolution (50 pm) one, to study, respectively, the atomic and the molecular emissions in the visible range. The spectroscopic data have been interpreted also by means of a collisional-radiative model developed at IPP Garching. Besides the diagnostic hardware and the data analysis methods, the paper presents the first plasma measurements across a transition to the full H mode, in a hydrogen discharge. The characteristic signatures of this transition in the plasma parameters are described, in particular, the sudden increase of the light emitted from the plasma above a certain power threshold.

Yacora on the Web: Online collisional radiative models for plasmas containing H, H2 or He

“…Available for Yacora are a multitude of extensively validated and benchmarked CR models for different atomic and molecular species (see for example [8,10]; some of the molecular models include the vibrational or the ro-vibrational sub-levels). These models have been applied for plasma diagnostics at numerous experiments worldwide (see, for example, [11,12,13,14,15,16,17,18]), with focus on lowpressure plasmas. The steadily increasing interest triggered the development of Yacora on the Web, a web application, providing access to the Yacora CR models for atomic and molecular hydrogen and for helium.…”