Emilio Martines

Università degli Studi di Milano-Bicocca | UNIMIB · Department of Physics

The results are presented of an experimental activity performed in the RFX-mod device aimed at characterizing plasma dynamics in the so-called ultralow-q (ULq) magnetic configuration, which corresponds to edge safety factor values below 1. The role of the edge safety factor in determining plasma dynamics is studied. In particular, a characterizatio...

The helical resonator is a scheme for the production of high voltage at radio frequency, useful for gas breakdown and plasma sustainment, which, through a proper design, enables avoiding the use of a matching network. In this work, we consider the treatment of the helical resonator, including a grounded shield, as a transmission line with a shorted...

To reach fusion conditions and control the plasma configuration in ITER, the next step in tokamak fusion research, two neutral beam injectors (NBIs) will supply 16.5 MW each, by neutralizing accelerated negative hydrogen or deuterium ions. The requirements of ITER NBIs (40A/1 MeV D- ions for ≤1 h, 46A/870 keV H- ions for ≤1000 s) have never been si...

Skin wound healing may sometimes lead to open sores that persist for long periods and expensive hospitalization is needed. Among different kinds of therapeutic innovative approaches, mesenchymal stem cells (MSCs) and low-temperature atmospheric pressure cold plasma (ionized gas) have been recently tested to improve this regenerative process. To opt...

The use of plasmas for biomedical applications in encountering a growing interest, especially in the framework of so-called “plasma medicine”, which aims at exploiting the action of low-power, atmospheric pressure plasmas for therapeutic purposes [...]

Background To optimize wound healing, the use of low-temperature atmospheric pressure plasma (ionized gas) has been proposed as an innovative therapeutic method for treating extensive and chronic wound. The aim of this study was to evaluate the specific effects of an indirect helium plasma treatment in a sheep surgical wound model based on clinical...

Plasma Medicine tools exploit the therapeutic effects of the exposure of living matter to plasma produced at atmospheric pressure. Since these plasmas are usually characterized by a non-thermal equilibrium (highly energetic electrons, low temperature ions), thermal effects on the substrate are usually considered negligible. Conversely, reactive oxy...

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 t...

The characterization of the plasma generated by a Hall Effect thruster operating in Nitrogen and Hydrogen is presented. Measurements of the spatial profiles of the electron temperature and density of the plume have been obtained by scanning the region outside the exit plane of the thruster through a Langmuir probe. The measurements are aimed to det...

Background: The integrity of the ocular surface and the transparency of the cornea is crucial to obtain a good visual acuity - a requirement to actively participate in both social and professional environments. The homeostasis of the ocular surface is constantly endangered by microbes and by intrinsic factors with negative influence on wound heali...

Localized heating has been observed in unexpected positions on anodic surfaces in a multi-electrode device insulated by vacuum gaps. In double polarity experiments, a counter-intuitive behavior of current-voltage characteristic has also been observed. The phenomena could depend on a cascade effect of charged particles exchanged between electrodes a...

This paper reports the characterization of a low-power, atmospheric pressure plasma source developed for and successfully tested in applications of plasma medicine. The source produces plasma by ionizing a helium flow, containing traces of air. The effluent gas is thus enriched in reactive oxygen and nitrogen species as well as helium metastable ex...

Background: Skin wound healing includes a system of biological processes, collectively restoring the integrity of the skin after injury. Healing by second intention refers to repair of large and deep wounds where the tissue edges cannot be approximated and substantial scarring is often observed. The objective of this study was to evaluate the effe...

Integrity of the ocular surface and transparency of the cornea as “window of the eye,” necessary to achieve a good visual acuity, are essential of every persons’ quality of life and for their ability to professionally and socially interact in the community. The homeostasis at the ocular surface is constantly endangered both by microbes and by intri...

The externally applied loop voltage, required to drive current carrying magnetic configurations, such as tokamaks or reversed field pinches (RFP), can induce currents between the plasma and the surrounding conducting components, such as limiters, divertor sections, stabilizing plates or enclosing stabilizing shells with insulated electrical gaps. A...

Aim The objectives of this study were to determine the efficacy and mechanisms of inactivation of two clinically relevant ESKAPE bacteria namely Pseudomonas aeruginosa and methicillin‐resistant Staphylococcus aureus by atmospheric pressure cold plasma. Methods and Results Plasma was generated between two brass grids by applying a radiofrequency el...

An insertable probe head called high resolution probe (HRP) has been developed at Consorzio reversed field experiment in the framework of the EUROfusion S1 work program and in collaboration with IPP Greifswald, to study the electrostatic and electromagnetic features of turbulence in the edge region of Wendelstein 7-X using the multipurpose manipula...

We describe an in-vitro study aimed at elucidating the role or Reactive Oxygen and Nitrogen Species (RONS) in promoting a selective killing of cancer cells, and the possibility of emphasizing the selectivity towards cancer cells by combining the plasma treatment with the effect of a molecule known to enhance intracellular ROS production. Lung carci...

This paper reports the main recent results of the RFX-mod fusion science activity. The RFX-mod device is characterized by a unique flexibility in terms of accessible magnetic configurations. Axisymmetric and helically shaped reversed-field pinch equilibria have been studied, along with tokamak plasmas in a wide range of q(a) regimes (spanning from...

Quasi-single helicity (QSH) state has been widely observed in reversed field pinch devices to sustain thermal structures, enclosed by steep temperature gradients interpreted as electron internal transport barriers (eITB). Within the evolution of a QSH cycle, three sub-states can be identified in the RFX-mod experiment, named DAx, SHAxn and SHAxw, w...

The RFX-mod experiment is a fusion device designed to operate as a reversed field pinch (RFP), with a major radius R = 2 m and a minor radius a = 0.459 m. Its high versatility recently allowed operating it also as an ohmic tokamak, allowing comparative studies between the two configurations in the same device. The device is equipped with a state of...

Cold atmospheric pressure plasmas provide the potential for effective treatment of infectious keratitis, a sight-threatening process with a worldwide occurrence of 2 million cases/yr. In microbial keratitis, bacteria, fungi, viruses, or small eukaryotes penetrate and proliferate in the cornea, causing inflammation and tissue ulceration. The require...

In fusion devices strong interest is deserved to the edge filament transport both related to turbulent and ELMy structures, because they are believed to provide important interaction with the plasma facing components and divertor plates. Among their features also the electromagnetic (EM) properties are expected to play an important role and in part...

A high power impulse magnetron sputtering (HiPIMS) plasma has been characterized by means of Langmuir probes measuring floating potential, electron temperature and density. Moreover, magnetic sensors have been employed in the analysis of the magnetic fluctuations. A low frequency electro-magnetic structure has been detected to propogate in the HiPI...

The reversed field pinch (RFP) device RFX-mod features strong internal transport barriers when the plasma accesses states with a single dominant helicity. Such transport barriers enclose a hot helical region with high confinement whose amplitude may vary from a tiny one to an amplitude encompassing an appreciable fraction of the available volume. T...

This paper describes a novel and simple concept of plasma source, which is able to produce a radiofrequency magnetized discharge with minimal power requirements. The source is based on the magnetron concept and uses a permanent magnet as an active electrode. The dipolar field produced by the magnet confines the electrons, which cause further ioniza...

An extensive statistical characterization of the electromagnetic turbulence in the edge region of RFX-mod, operated as a tokamak and as a Reversed Field Pinch, is presented. Striking similarity are observed on the intermittent character of the electrostatic turbulence between the two configurations whereas the difference between magnetic turbulence...

Cold atmospheric pressure plasma has been proposed for sterilization of inert surfaces and disinfection of living tissues. Our recent studies reveal that chemically active species such as reactive oxygen species generated by a low-power atmospheric pressure nonthermal plasma source obtained by ionizing helium gas mixed with ambient air are mandator...

An overview of recent results from the MST reversed field pinch programme is presented. With neutral beam injection, bursty energetic particle (EP) modes are observed. The profiles of the magnetic and density fluctuations associated with these EP modes are measured using a far infrared interferometer–polarimeter. Equilibrium reconstructions of the...

The RFX-mod device is operated both as a reversed field pinch (RFP), where advanced regimes featuring helical shape develop, and as a tokamak. Due to its flexibility, RFX-mod is contributing to the solution of key issues in the roadmap to ITER and DEMO, including MHD instability control, internal transport barriers, edge transport and turbulence, i...

Definition of helical coordinate system as action-angle canonical coordinates, and computation of the helical safety factor profile. 53rd Annual Meeting of the APS Division of Plasma Physics, Salt Lake City (Utah), 14-18 November. Oral presentation titled "Helical coordinate Systems for SHAx RFP states”. Oral session PO4 7.

Three-dimensional non-axisymmetric magnetic fields are purposely applied to toroidally symmetric fusion plasmas in order to modify transport of heat and particle fluxes to the plasma-facing components (PFCs), and specifically to control and suppress edge localized modes (ELMs) in H-mode tokamak plasmas. This paper presents a comparative study betwe...

Background: Atmospheric pressure cold plasma (APCP) might be considered a novel tool for tissue disinfection in medicine since the active chemical species produced by low plasma doses, generated by ionizing helium gas in air, induces reactive oxygen species (ROS) that kill microorganisms without substantially affecting human cells. Objectives: I...

Filament or blob structures have been observed in all magnetic configurations with very similar features despite the difference in the magnetic geometry, and are believed to play an important role in convecting particles and energy towards the wall. Despite their different generation mechanism, turbulent structures and edge-localized mode (ELM) fil...

Transport phenomena affect the performance of fusion devices, reducing heat and particle confinement and consequently leading to a lower fusion triple product and higher fluxes on the plasma facing material. Special attention is devoted in the fusion community to the study of transport mitigation phenomena which lead to the onset of transport barri...

The ITER scenarios and the project of DEMO involve stable operation above the Greenwald density, which justifies efforts to understand and overcome the density limit, this last observed as a disruptive termination of tokamak discharges and a thermal crash (with no disruption) of stellarator and reversed-field pinch (RFP) ones. Both in the tokamak a...

Electromagnetic features of turbulent filaments, emerging from a turbulent plasma background, have been studied in four different magnetic configurations: the stellarator TJ-II, the Reversed Field Pinch RFX-mod, a device that can be operated also as a ohmic tokamak, and the Simple Magnetized Torus, TORPEX. By applying an analogous diagnostic concep...

Cold plasmas have been proposed for many applications in medicine, such as tissue disinfection and wound healing. Their antibacterial effects have been well demonstrated and depend mainly to the action of reactive oxygen species or ROS, but the molecular mechanisms promoting tissue regeneration in wound healing are not yet fully understood. We prev...

Atmospheric pressure cold plasma (APCP) is a novel tool for tissue disinfection that has also positive effects on wound healing. We recently reported that two minutes of APCP, generated through the ionization of helium gas, exerted an antimicrobial effect without significant damage to cells and tissues (1), effects that may induce also fibroblast p...

A complete description of the effects of magnetic perturbation on the edge region of RFX-mod is here reported. The flexibility of the RFX-mod device [1] allows for the operation of the machine both as a reversed field pinch (RFP, with maximum current 2 MA) and as a low-current, circular ohmic tokamak (Ip,max = 0.15 MA). The present paper summarizes...

The ITER scenarios and the project of DEMO involve stable operation above the Greenwald density, which justifies efforts to understand and overcome the density limit, observed as a disruptive termina-tion of tokamak discharges and a thermal crash (with no disruption) of stellarator and reversed-field pinch (RFP) ones. Both in the tokamak and the RF...

Non-thermal atmospheric pressure plasmas are being developed for a wide range of health care applications, including wound healing. However in order to exploit the potential of plasma for clinical applications, the understanding of the mechanisms involved in plasma-induced activation of fibroblasts, the cells active in the healing process, is manda...

Measured neutron signals relevant for plasma diagnostics on Reversed Field pinch eXperiment, RFX-mod, are obtained by nuclear track methodology with PADC-NTD’s. This technique provides the external neutron field values around the RFX-mod installation during pulsed operation. Charged particles from (n, p) and (n, α) reactions are related to formed l...

A feedforward scheme is applied for drift waves control in a magnetized magnetron sputtering plasma. A system of driven electrodes collecting electron current in a limited region of the explored plasma is used to interact with unstable drift waves. Drift waves actually appear as electrostatic modes characterized by discrete wavelengths of the order...

Infectious keratitis of the eye is induced by proliferation and penetration of microorganisms in the cornea. The possibility of developing a novel treatment for this condition based on the action of a low temperature, atmospheric pressure plasma is presented. In-vitro results show that bacteria and fungi responsible of keratitis are inactivated by...

The plasma–wall interaction (PWI) in the reversed field pinch is strongly influenced by three-dimensional edge magnetic topology. This is true both in the chaotic regime, where several modes interact producing a toroidally localized bulge, and in the helical state, which helically modulates the edge profiles. In both regimes an external region with...

An overview of recent results from the MST programme on physics important for the advancement of the reversed field pinch (RFP) as well as for improved understanding of toroidal magnetic confinement more generally is reported. Evidence for the classical confinement of ions in the RFP is provided by analysis of impurity ions and energetic ions creat...

A better understanding of the edge phenomena regulating plasma transport and turbulence is of primary importance for the whole fusion community. In particular, in reversed field pinches (RFPs) the edge properties are found to have a strong relation with the magnetic topology. The flexibility of the RFX-mod RFP experiment (Sonato et al 2003 Fusion E...

One of the main problems in tokamak fusion devices concerns the capability to operate at a high plasma density, which is observed to be limited by the appearance of catastrophic events causing loss of plasma confinement. The commonly used empirical scaling law for the density limit is the Greenwald limit, predicting that the maximum achievable line...

High current (Ip = 1–1.7 MA) operations in the ohmic reversed field pinch RFX-mod spontaneously access the quasi-single helicity (QSH) regime, in which the magnetic dynamics is dominated by the innermost resonant mode (m = 1, n = −7), the magnetic chaos level is reduced and the internal magnetic field configuration is close to a pure helix. During...

In the reversed field pinch RFX-mod at the highest plasma current of 2 MA, when error fields are not effectively feedback controlled, localized thermal loads up to tens of MW m(-2) can be produced. The graphite tiles withstand such high power loads, but the high hydrogen retention makes density control extremely difficult. Several wall conditioning...

In present fusion research a strong effort is devoted to the studies of non-axisymmetric magnetic perturbations and consequent field ergodization on the external region of the plasma. On this topic interesting results can be drawn from the helical configuration observed in high-current regimes in reversed field pinches (RFPs) where the small edge h...