title: 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.
authors.affiliation: Consorzio RFX (CNR, ENEA, INFN, Univ. of Padua, Acciaierie Venete SpA), C.so Stati Uniti 4, 35127 Padova, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Barbisan
authors.affiliation: Consorzio RFX (CNR, ENEA, INFN, Univ. of Padua, Acciaierie Venete SpA), C.so Stati Uniti 4, 35127 Padova, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Baltador
authors.affiliation: Consorzio RFX (CNR, ENEA, INFN, Univ. of Padua, Acciaierie Venete SpA), C.so Stati Uniti 4, 35127 Padova, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Zaniol
authors.affiliation: INFN-LNL, v.le dell'Università 2, I-35020 Legnaro, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Cavenago
authors.affiliation: Max-Planck Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Fantz
authors.affiliation: Consorzio RFX (CNR, ENEA, INFN, Univ. of Padua, Acciaierie Venete SpA), C.so Stati Uniti 4, 35127 Padova, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Pasqualotto
authors.affiliation: Consorzio RFX (CNR, ENEA, INFN, Univ. of Padua, Acciaierie Venete SpA), C.so Stati Uniti 4, 35127 Padova, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Serianni
authors.affiliation: Università degli Studi di Padova, Via 8 Febbraio, 2, 35122 Padova, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Vialetto
authors.affiliation: Max-Planck Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Wünderlich