Nahid Sadeghi

Institute For Humanities and Cultural Studies | IHCS · Department of Communication

Background: Transulnar approach (TUA) has been classified as an appropriate surrogate for the transradial approach (TRA), but the safety of TUA in the presence of ipsilateral radial artery occlusion (RAO) is not well studied. In this article, we aimed to assess the feasibility and occurrence of complications of this approach in Iranian individuals...

Background: Acute coronary syndrome (ACS) is a common condition that needs appropriate treatment like percutaneous coronary intervention (PCI). Glycoprotein IIb/IIIa inhibitors (GPI) like eptifibatide prevent procedural ischemic complications after PCI. Eptifibatide has increased the risk of bleeding complications, although it is effective in redu...

Different diagnostic techniques are used to monitor the dynamics of electrons and Ar*(1s5) metastable atoms in the active plasma phase and in the afterglow of a capacitively coupled radio-frequency (RF) discharge operated in different gas mixtures and at different input powers. Diode laser absorption at 772.38 nm is used to measure the time resolve...

Diffuse dielectric barrier discharges in atmospheric-pressure helium can be sustained over a wide range of excitation frequencies (from, but not restricted, 25 kHz to 15 MHz). The aim of the present paper is to identify the specific characteristics of the discharge modes that can be sustained in this frequency range, namely, the atmospheric-pressur...

The measurement of absolute densities of reactive species and radicals such as OH is of growing interest for many plasma applications. In this paper, we extend the use of a self-absorption model for atomic emission spectroscopy to molecular emission spectroscopy. The proposed analysis of self-absorbed molecular emission spectra is a simple and inex...

Using tunable diode laser absorption spectroscopy, the spatio-temporal distributions of the helium He(2 3 S 1 ) metastable atoms’ density were measured in a plasma jet propagating in ambient air. The plasma jet was produced by applying short duration high voltage pulses on the electrodes of a DBD-like structure, at a repetition rate in the range 1–...

Parallel Micro Hollow Cathodes Discharges are characterised by electrical and spectroscopic studies and by using an ICCD camera. V-I curves present a hysteresis cycle between Townsend and normal glow regimes. For I d =4-10mA, gas temperature ranges between 300-500{\textdegree}C. When the diameter of a hole decreases, a more significant discharge vo...

Several issues associated with plasma etching of high aspect ratio structures originate from the ions' bombardment of the sidewalls of the feature. The off normal angle incident ions are primarily due to their temperature at the sheath edge and possibly to charging effects. We have measured the ion velocity distribution function (IVDF) at the...

The laser pump-probe technique is used to study the electron impact transfer between the 1s5 and 1s4 states of argon (in Paschen's notation) belonging to the 2P3/2 ion core for electron temperatures in the range of 1-2 eV. A rate coefficient of m3s-1 is determined for the transfer from 1s5 to 1s4 state. Different pumping schemes between the 1s and...

The apparent rate coefficients for the electron-impact excitation from argon 1s to 3p states are determined in the electron temperature (T e) range of 0.8 to 1.2 eV, in the afterglow of a capacitive argon discharge by using the temporal behavior of different state densities. The measured parameters include the densities of the 3p states (by optical...

The density of helium He (23S1) metastable atoms is measured in a 1.6 mm diameter MHz-driven atmospheric pressure helium plasma jet by laser absorption spectroscopy with spatial and temporal resolution. The surrounding atmosphere of the jet is varied from pure oxygen to pure nitrogen with a gas shielding device. The highest metastable density of 1....

In this paper, a detailed investigation of the spatio-temporal dynamics of a pulsed microwave plasma is presented. The plasma is ignited inside a dielectric tube in a repetitively pulsed regime at pressures ranging from 1 up to 100?mbar with pulse repetition frequencies from 200?Hz up to 500?kHz. Various diagnostic techniques are employed to obtain...

In this work we present Thomson scattering measurements on a nanosecond pulsed high voltage dielectric barrier discharge (DBD)-like helium plasma jet, operated in ambient air. With the low detection limit offered by a triple grating spectrograph equipped with a high quantum efficiency intensified charge-coupled device (ICCD) camera, temporally and...

Tunable diode laser absorption spectroscopy was used to measure the spatio-temporal evolution of helium metastable atoms He (23S) in an atmospheric plasma jet. The production of these atoms is clearly correlated to the propagation of an ionization wave, the so-called plasma bullet. Whatever the applied voltage, the spatial structure of the density...

The time-resolved OH density in a nanosecond pulsed filamentary discharge in an atmospheric pressure He–H2O(0.05%) mixture is measured using laser induced fluorescence. The lifetime of the excited OH(A) state is found to be strongly time dependent during the plasma pulse, with the shortest decay time occurring at the moment the plasma is switched o...

The gas temperature in non-equilibrium plasmas is often obtained from the plasma-induced emission by measuring the rotational temperature of a diatomic molecule in its excited state. This is motivated by both tradition and the availability of low budget spectrometers. However, non-thermal plasmas do not automatically guarantee that the rotational d...

A power-modulated radio-frequency (f = 13.56 MHz) argon plasma supplied by reactive acetylene to deposit an amorphous hydrocarbon film on the electrodes is studied. The effects of gradual film deposition on electron density, electron temperature, argon metastable Arm(3P2) density, and dc-bias voltage are investigated. The time evolutions of plasma...

Micro hollow cathode discharges (MHCD) were produced using 250 lm thick dielectric layer of alumina sandwiched between two nickel electrodes of 8 lm thickness. A through cavity at the center of the chip was formed by laser drilling technique. MHCD with a diameter of few hundreds of micrometers allowed us to generate direct current discharges in hel...

The self-absorption technique is a simple method to determine the line integrated density of metastable atoms in low-pressure plasmas. In order to employ this technique, it is necessary to make an assumption on the spatial profiles of both the emission intensity and the absorbing species, which usually are unknown and can be highly nonuniform. Taki...

The absolute density of OH radicals generated in a nanosecond pulsed filamentary discharge in atmospheric pressure He +0.84% H2O is measured independently by UV absorption and laser induced fluorescence (LIF) calibrated with Rayleigh scattering. For the calibration of LIF with Rayleigh scattering, two LIF models, with six levels and four levels, ar...

In a microwave argon plasma, the electron-impact population transfers between the first four excited states of argon are studied by time-resolved laser pump–probe technique. Metastable atoms in the 1s 5 state (in Paschen's notation) are selectively pumped up to the 2p 3 state, with a nanosecond pulsed dye laser tuned to the 706 nm argon transition...

Absolute OH densities are obtained in a radio-frequency-driven Ar–H2O atmospheric-pressure plasma jet by laser-induced fluorescence (LIF), calibrated by Rayleigh scattering and by UV broadband absorption. The measurements are carried out in ambient air and the effect of air entrainment into the Ar jet is measured by analyzing the time-resolved fluo...

This study presents the absolute argon 1 s (in Paschens's notation) densities and the gas temperature, T{sub g}, obtained in a surfatron plasma in the pressure range 0.65<p<100 mbar. The absorption signals of 772.38, 772.42, 810.37, and 811.53 nm lines, absorbed by atoms in 1s{sub 3}, 1s{sub 4,} and 1s{sub 5} states, were recorded with two tunable...

Neutral depletion, which is mostly caused by gas heating under typical material processing conditions, is an important phenomenon in high-density plasmas. In low pressure pulsed discharges, experiments show that additional depletion due to electron pressure (Pe) may have a non-negligible influence on radical transport [1]. To evaluate this effect,...

At atmospheric pressure in Ar, a micro-thin-cathode discharge operates in a self-pulsing mode due to periodic ignition of a nanosecond spark discharge with a long living afterglow (several hundred nanoseconds). In this mode, optical emission spectra of the nanosecond spark and the afterglow are investigated. The electron density and temperature in...

form only given. Recently, interest in plasma micro-jet at atmospheric pressure has increased due to their unique capabilities and novel applications, such as biomedicine[Laroussi M. and Lu, X., 2005] thin film disposition[Rabbaland, V. et al., 2009] and chemical decontamination[Laroussi M. and Akan T., 2007]. In this work we report on the measurem...

The measurement of radical densities in atmospheric-pressure plasmas has gained increasing importance in recent years in view of their crucial role in many applications. In this paper we present absolute OH density measurements by broadband UV absorption in diffuse atmospheric-pressure RF glow discharges in mixtures of He and H2O. The use of a 310...

This paper reviews recent progress in the development of time-resolved diagnostics to probe high-density pulsed plasma sources. We focus on time-resolved measurements of radicals' densities in the afterglow of pulsed discharges to provide useful information on production and loss mechanisms of free radicals. We show that broad-band absorption spect...

The dynamic of charged particles in pulsed plasma is relatively well known since the 1990s. In contrast, works reporting on the impact of the plasma modulation frequency and duty cycle on the radicals’ densities are scarce. In this work, we analyze the impact of these modulation parameters on the radicals’ composition in Cl2 and HBr plasmas. The ra...

Pulsed plasmas are promising for etching applications in the microelectronic industry. However, many new phenomena are involved when a high density discharge is pulsed. To better understand these processes it is necessary to probe the radicals' kinetics with a microsecond resolution. We have developed several diagnostics to reach this goal includin...

A micro-hollow cathode discharge was used to generate radiation on the chlorine atom resonance lines. Such radiation could be used to measure, by resonance absorption spectroscopy, the density of chlorine atoms in either ground state (3p5 2P3/2) or in the fine structure metastable state (3p5 2P1/2), which is located at 882.35 cm−1. Among the nine a...

Absolute densities of metastable He(23S1) atoms were measured line-of-sight integrated along the discharge channel of a capacitively coupled radio-frequency driven atmospheric pressure plasma jet operated in technologically relevant helium–oxygen mixtures by tunable diode-laser absorption spectroscopy. The dependences of the He(23S1) density in the...

Zero-dimensional, space-averaged global models of argon dust-free and dusty afterglow plasmas are developed, which describe the time behaviour of electron ne(t) and Ar* metastable nm(t) densities. The theoretical description is based on the assumption that the free electron density is smaller than the dust charge density. In pure argon, fairly good...

Broad band UV-visible absorption spectroscopy is widely used to measure the concentration of radicals in reactive plasmas. We extended the applicability of this technique to the VUV (115 nm to 200 nm), the spectral range in which the electronic transitions from the ground state to the Rydberg or pre-dissociated states of many closed-shell molecules...

The lowest 1Π state of the NaK molecule, B(1) 1Π, which dissociates to Na (2S1/2) + K (2P3/2), has been studied in three ways: (i) by laser-induced fluorescence recorded at high resolution by Fourier-transform spectrometry, (ii) by dye-laser excitation spectroscopy, and (iii) by observations of the effect of an electric field, which mixes the e and...

Based on micro-hollow cathode discharge (MHCD) as a plasma cathode, a second anode was added to the device for obtaining large volume and uniform plasma at high pressure. The discharge producing condition of MCSD was investigated in the experiments. And the rotational structures of the N2 first positive bands were analyzed with traces of nitrogen a...

Space resolved concentrations of helium He* (3S1) and argon Ar* (3P2) metastable atoms in an atmospheric pressure radio frequency micro-plasma jet were measured using tunable diode laser absorption spectroscopy. Even small absorptions down to 10-4 could be measured using lock-in technique. The absolute density of metastable atoms densities at diffe...

A microplasma is generated in the microhole (400μm diameter) of a molybdenum-alumina-molybdenum sandwich (MHCD type) at medium pressure (30–200Torr) in pure argon. Imaging and emission spectroscopy have been used to study the sheath and electron density dynamics during the stationary normal regime and the self-pulsing regime. Firstly, the evolution...

We report in this paper simulation results and experimental measurements to characterize a micro-discharge generated in a single micro cavity device operating in helium. By spatially limiting the cathode surface area using a dielectric layer, we demonstrate the ability of the micro-discharge to work in a steady-state abnormal glow regime. The physi...

The velocity component of singly charged xenon ions in a plane perpendicular to the thrust axis of the 1 kW-class PPS100-ML Hall effect thruster is deduced from laser induced fluorescence measurements on the 5d 2F7/2→6p 2D5/20 electronic transition at 834.72 nm. Measurements are carried out at several locations in the near field of the channel exha...

We report in this paper simulation results and experimental measurements to characterize a micro-discharge generated in a single micro cavity device operating in helium. By spatially limiting the cathode surface area using a dielectric layer, we demonstrate the ability of the micro-discharge to work in a steady-state abnormal glow regime. The physi...

Silicon etching in Cl2-based plasmas is an important step for the fabrication of IC circuits but the plasma surface interactions involved in this process remain poorly understood. Based on the developments in plasma and reactor wall diagnostics, this paper reviews the recent progress in the understanding of radicals' interactions with surfaces duri...

A microplasma is generated in the microhole (400 µm diameter) of a molybdenum-alumina-molybdenum sandwich (MHCD type) at medium pressure (30-200 Torr) in pure argon. Imaging and emission spectroscopy have been used to study the light emission mechanisms in the microdischarge. We find that emission intensities of both argon atom and argon ion lines...

The 8th Workshop on Frontiers in Low Temperature Plasma Diagnostics (FLTPD) was held in Blansko, near Brno, Czech Republic. FLTPD is a biennial European event in which scientists working on low temperature plasmas present their recent results, pointing out in particular the originality of the diagnostic techniques used. The idea of starting this se...

Diode laser absorption at 772.38 nm is used to measure the time resolved density of Ar* (3P2) metastable atoms in a capacitively coupled radio-frequency (RF) discharge running in an argon/acetylene mixture at 0.1 mbar. The RF power is pulsed at 100 Hz and the density of Ar* (3P2) atoms in the 5 ms ON time and in the afterglow is recorded. Different...

Neutral depletion is an important phenomenon in high-density plasmas. We show that in pulsed discharges, the neutral depletion caused by the electron pressure Pe plays an important role on radical transport. In the afterglow, Pe drops rapidly by electron cooling. So, a neutral pressure gradient built up between the plasma bulk and the reactor walls...

As to microhollow cathode discharge (MHCD) in argon, the discharge characteristic was analyzed, the gas temperature was determined from the emission spectroscopy with traces of nitrogen added, and the electron density was also evaluated through the Stark broadening of the Balmer Hβ line from hydrogen as trace impurity in the gas. The electron densi...

A microplasma is generated in the 400 μm diameter micro hole of a molybdenum-alumina-molybdenum sandwich (MHCD type) at medium pressure (30-300Torr) in pure argon. Experiments are performed during the normal regime, when the plasma is not only confined in the hole but also expands on the cathode backside. Imaging and emission spectroscopy allows th...