Electron density and temperature in NIO1 RF source operated in oxygen and argon

Abstract

The NIO1 experiment, built and operated at Consorzio RFX, hosts an RF negative ion source, from which it is possible to produce a beam of maximum 130 mA in Hions, accelerated up to 60 kV. For the preliminary tests of the extraction system the source has been operated in oxygen, whose high electronegativity allows to reach useful levels of extracted beam current. The efficiency of negative ions extraction is strongly influenced by the electron density and temperature close to the Plasma Grid, i.e. the grid of the acceleration system which faces the source. To support the tests, these parameters have been measured by means of the Optical Emission Spectroscopy diagnostic. This technique has involved the use of an oxygen-argon mixture to produce the plasma in the source. The intensities of specific Ar I and Ar II lines have been measured along lines of sight close to the Plasma Grid, and have been interpreted with the ADAS package to get the desired information. This work will describe the diagnostic hardware, the analysis method and the measured values of electron density and temperature, as function of the main source parameters (RF power, pressure, bias voltage and magnetic filter field). The main results show that not only electron density but also electron temperature increase with RF power; both decrease with increasing magnetic filter field. Variations of source pressure and plasma grid bias voltage appear to affect only electron temperature and electron density, respectively.

Cs Evaporation in a Negative Ion Source and Cs Cleaning Tests by Plasma Sputtering

“…The plasma conditions were mostly monitored by three diagnostics:  Plasma light detection: a photomultipler (PMT), active in the 230 nm÷920 nm wavelength range, measures the light intensity collected by an optic head placed on the rear side of the source.  Optical Emission Spectroscopy (OES) [20] A Surface Ionization Detector (SID), while being desirable to measure the Cs flux from the oven duct [[24]- [25]], could not be installed due to space limitations. Numerical simulations are planned in future to estimate the Cs flux from the temperatures of the oven components.…”

Plasma Spectroscopy Diagnostics of V2O5 at a Variable of Operating Power and Pressure With Radio Frequency Magnetron Sputtering.

“…On the other hand the electron density excess, through the particle equilibrium been ions which generated by electron influence and ions missing on the source walls, it is maybe that the (T e ) is independent of the (n e ). So higher proceeds in RF power to an increase in electron density (15). The emission spectra of the plasma argon produce between electrodes at pressure (0.03, 0.05 and 0.007) torr are in Fig.…”

Plasma Spectroscopy Diagnostics of V2O5 at a Variable of Operating Power and Pressure With Radio Frequency Magnetron Sputtering.

“…On the other hand the electron density excess, through the particle equilibrium been ions which generated by electron influence and ions missing on the source walls, it is maybe that the (T e ) is independent of the (n e ). So higher proceeds in RF power to an increase in electron density(15).…”