A novel plasma jet with RF and HF coupled electrodes

In order to achieve low processing temperature and efficient coatings deposition for manufacturing applications, a novel torch has been developed that couples in a double DBD design high frequency (HF ~17 kHz) and radio frequency (RF ~27 MHz) excitations. The design allows to obtain a stable RF plasma also in reactive processes and with the possibility to control on the treated substrates ions flux and surface charging, avoiding the micro-discharges. The plasma has been electrically and optically characterized by emission spectroscopy

On the Electrical and Optical Features of the Plasma Coagulation Controller Low Temperature Atmospheric Plasma Jet

We report on the electrical and optical characterization of the Plasma Coagulation Controller (PCC) device, a low temperature atmospheric plasma source for biomedical applications. This device, designed for the study of plasma-induced blood coagulation, has been developed to operate flexibly in several operational conditions, since it is possible to vary the applied voltage V p and the pulse repetition rate f in a quite wide range ( V p range: 2–12 kV, f range: 1–40 kHz). Emission spectroscopy measurements were conducted by varying the line of sight along the axis of helium and neon plasma plumes. The increase of the Reactive Oxygen and Nitrogen Species (RONS) has been observed, as one moves from inside the gas pipe to the outside, as a consequence of the gas mixture with the surrounding air. Furthermore, high-speed photographs of the plasma jet were taken, showing that the plasma is not uniformly distributed in a continuous volumetric region, the plasma being concentrated in localized structures called Pulsed Atmospheric-pressure Plasma Streams (PAPS). The propagation velocities of these objects have been examined, noting that they are not related to the propagation of ion sound waves. Rather, we provide indications that the streamer propagation speed is proportional to the electron drift velocity

Overview on electrical issues faced during the SPIDER experimental campaigns

SPIDER is the full-scale prototype of the ion source of the ITER Heating Neutral Beam Injector, where negative ions of Hydrogen or Deuterium are produced by a RF generated plasma and accelerated with a set of grids up to ~100 keV. The Power Supply System is composed of high voltage dc power supplies capable of handling frequent grid breakdowns, high current dc generators for the magnetic filter field and RF generators for the plasma generation. During the first 3 years of SPIDER operation different electrical issues were discovered, understood and addressed thanks to deep analyses of the experimental results supported by modelling activities. The paper gives an overview on the observed phenomena and relevant analyses to understand them, on the effectiveness of the short-term modifications provided to SPIDER to face the encountered issues and on the design principle of long-term solutions to be introduced during the currently ongoing long shutdown.Comment: 8 pages, 12 figures. Presented at SOFT 202

Use of electrical measurements for non-invasive estimation of plasma electron density in the inductively coupled SPIDER ion source

SPIDER is the full-scale prototype of the ITER Neutral Beam Injector ion source. The plasma heating takes place inside eight drivers via inductive coupling, through the radio frequency (RF) coil. To achieve the optimum conditions during source operation it is necessary to know the plasma behaviour under various operational conditions. One of the essential parameter, is the plasma electron density. It is possible to experimentally measure this parameter, and currently, different methods are being explored, like the estimations coming from the Langmuir probe and optical emission spectroscopy. However, these methods are either available for temporary measurements or require dedicated analyses with large uncertainties. In this perspective, an alternative, reliable, and fast diagnostic tools will be beneficial for the estimation of the order of magnitude of electron density inside the driver. Two models for the estimation of electron density are recalled, discussed, and further modified in this work: one is based on the classical power balance equation and the other is recently described in the literature and relies on classical plasma conductivity. Both models use equivalent electrical parameters of the driver derived from available electrical measurements at the output of the RF generator and through the knowledge of the matching network and the transmission line length. This work explicitly focuses on the application of these models to estimate the plasma electron density in a single driver of SPIDER. Furthermore, the estimations are compared with the first experimental results obtained from temporary electrostatic probe measurements and are found to be in good agreement in terms of magnitude and trends

Removal of persistent organic pollutants from water using a newly developed atmospheric plasma reactor

A new bench-top reactor employing a streamer discharge in air was developed and tested for potential use in an advanced oxidation stage in water treatment processes. The complex heterogeneous system and the ensuing chemical processes were characterized using an integrated approach to map the morphology of the plasma/gas/liquid interface, identify the plasma short-lived excited species, determine the oxidants in solution and monitor the organic pollutants degradation. Three model pollutants were used in these experiments, rhodamine B, phenol and metolachlor. The first two are common standards used to evaluate the performance of advanced oxidation processes. Metolachlor is a widely used herbicide listed among the most important recalcitrant emerging organic pollutants. Energy efficiency, kinetics and products of our tests show a good performance of the reactor. Specifically, mineralization appears feasible also in the case of metolachlor

Spectroscopic and chemical characterization of atmospheric plasmas produced in hydrocarbon contaminated air by DC and pulsed corona discharges

Optical emission spectroscopy was used to characterize the plasma produced by DC and pulsed corona discharges in air at ambient pressure in a wire-cylinder reactor. The experiments have been performed both in dry and humid air and also in the presence of n-hexane, used in 500 ppm concentration as a model pollutant. The results provide a thorough characterization of different plasma regimes in terms of electron, vibrational and rotational temperature and are discussed with reference to chemical reactivity data

First experiments with the negative ion source NIO1

Neutral Beam Injectors (NBIs), which need to be strongly optimized in the perspective of DEMO reactor, request a thorough understanding of the negative ion source used and of the multi-beamlet optics. A relatively compact radio frequency (rf) ion source, named NIO1 (Negative Ion Optimization 1), with 9 beam apertures for a total H- current of 130 mA, 60 kV acceleration voltage, was installed at Consorzio RFX, including a high voltage deck and an X-ray shield, to provide a test bench for source optimizations for activities in support to the ITER NBI test facility. NIO1 status and plasma experiments both with air and with hydrogen as filling gas are described. Transition from a weak plasma to an inductively coupled plasma is clearly evident for the former gas and may be triggered by rising the rf power (over 0.5 kW) at low pressure (equal or below 2 Pa). Transition in hydrogen plasma requires more rf power (over 1.5 kW). © 2015 AIP Publishing LLC