Marcelo Pego Gomes

Electric and spectroscopic properties of argon-hydrogen RF microplasma jets at atmospheric pressure

Microplasma jets of argon–hydrogen (Ar–H2) gas mixture were generated by 144.0 MHz radio-frequency (RF) waves at powers of 5 W, 10 W, 20 W and 50 W. The experimental setup employed creates stable microplasmas at atmospheric pressure from 5.0 mm up to 20.0 mm visual glow lengths. We have determined the rms voltages, the rms electric currents and the power absorptions of these microplasma jets. By making use of optical spectroscopy, the emission spectra of Ar–H2 microplasma jets were recorded in the range 3060–8200 A, in order to estimate the axial distribution profiles of electron density, rotational temperature, excitation temperature and hydrogen atomic temperature.

Measurements of extremely low frequency waves (1–12 Hz) produced by ionospheric high-frequency waves

In a recent study, a process for the generation of Extremely Low Frequency (ELF) waves in the range of 1–12 Hz produced by diamagnetic currents generated by heat in ionosphere by high frequency (HF) waves has been proposed. HF waves that reach the ionosphere can be generated, for example, on the Earths surface by the High Frequency Active Auroral Research Program (HAARP) instruments or solar processes. Using a EMF low frequency spectrum analyzer with high sensitivity (1 μΥ) operating in the range of 1–12 Hz and using a low sampling time (5 ms), it was possible to measure HF waves. A series of measurements were carried out in São José dos Campos, Brazil, from September, 2016 to March, 2017, under dry conditions and with the analyzer isolated from electrical discharges to detect and record these waves. The positive results of the experimental observations suggest a possible confirmation of the occurrence of diamagnetic currents in ionosphere.

Radon Gas Measurements through Geiger and Sodium Iodide Scintillator----Study Efficiency Comparison

With the use of a Geiger proportional counter with sensor tube of Russian and Chinese origin, a comparison was made in this work between measurements of environmental ionizing radiation with these detectors and a sodium iodide scintillator activated with TI (Thallium NaI). Through measurements carried out in a room located inside a tower 25 meters high on the ITA (Technological Institute of Aeronautics) campus, it was possible to study the efficiency of the three instruments for the environmental measurement of ionizing radiations at that location. Between March 7th and June 2nd of 2017, in that region, nine intense and weak rains were observed with 12 cold fronts coming from southern Brazil. Radiation measurements and the local meteorology involved are analyzed in this work to verify possible correlations.

Study of a Portable Experimental Set for the Monitoring of Ionizing Radiation in the Tropical Region of Brazil

The Geiger is a proportional counter that detects the ambient ionizing radiation using a sensor tube and an associated electronics that allows feeding the desired voltage to the tube and acquiring the data in a certain time interval. With a sensor tube of Chinese and Russian origin and associated electronics based on the Arduino system, an experimental set of very low cost and easy handling for the monitoring of the local environmental ionizing radiation was set up. The main objective of this work is to disseminate this very low cost technique for the environmental study in secondary schools in Brazil.

Correlation between Rainfall and Cold Fronts with Gamma Ray Measurements near Ground Level in Southeastern Brazil

Gamma radiation measurements integrated between 200 keV and 10.0 MeV were performed between 03/07/2017 and 05/24/2017 from a tower of 25 meters of altitude in the region of São José dos Campos, SP, Brazil. Throughout this period, there were 9 intense and moderate rains with 11 arrivals of cold fronts coming from southern Brazil. Through measurements of gamma radiation integrated in the energy range mentioned above, the presence of these meteorological parameters and their variations in the region can clearly be observed. Through a potential calibration between the measured gamma radiation intensity and the observed rainfall intensity, it is possible to monitor rains by time interval using this gamma ray detector. Another very important parameter for the region consists of monitoring the number of passages of cold fronts that interfere in the local climatology. This low-cost, easy-to-operate technique can be applied and used in any tropical and equatorial region of the earth’s surface.

Dynamics in Times of Ionizing Radiation and Rainfalls in Tropical Region of Brazil

Low energy gamma rays and rainfalls were monitored each minute in the region around Sao Jose dos Campos, (23 0 :10`S, 45 0 :53`W) in Brazil, from March 7th to June 28th in 2017. In this period, it was possible to see the dynamic process that occurs between the presence of ionizing radiation (gamma rays) of low energy and the variation of rain intensity in (mm) / min in the same region. During this period, 12 major peaks of radiation intensity corresponding to 12 rains of high and low intensities were observed. This positive rainfall / radiation correlation is very noticeable in the tropical region of Brazil, which is certainly due to the presence of the decay of 238U uranium into radium 226Ra and arriving at the 222Rn radon with α emission particles and low energy gamma radiation. Therefore, the rain interferes in the presence of the local exhalation of the radon gas, causing the washing of this gas in the low atmosphere, increasing the intensity of radiation measured momentarily in that location. This work shows this dynamic measured in this interval in the year 2017, where there was rainy and dry weather in the place.

Dynamics of Environmental Ionizing Radiation between May to September 2016 in the Region of São José dos Campos, SP, Brazil

Measurements of gamma radiation (200 keV to 10 MeV) were performed between May 25 to September 3

Electric field gradient in microplasmas

Linear Stark splitting of the Hβ Balmer line components and spatially resolved optical emission spectroscopy (OES) measurements were used to estimate the electric field gradient in the cathode sheath region (~70 μm long) of an atmospheric pressure direct current argon flow-stabilized microplasma jet. Also, plasma parameters in the negative glow region were investigated by both OES and electrical diagnostics. OES was used to diagnose near-cathode region (negative glow and cathode sheath) of the microplasma jet in order to measure both, the basic discharge parameters, in the plasma bulk, and electric field distribution along the cathode sheath. In addition, the main mechanisms responsible for Hβ spectral line broadenings were investigated.

Enhancing wettability of high density polyethylenes (HDPE) through microplasma jets

This paper aims at the characterization of plasma microjets generated by open microhollow cathodes to ionize gases such as air, N2, He and O2. The electrical and optical parameters were raised. Through the optical emission spectroscopy, gas temperature (Tg) and the excitation temperature were estimated. Tg ranging from 2100K to 600K for a gas flow rate ranging from 0 to 400ml/min. From 150 to 400ml/min Tg remained close to 700K. As an application, the treatment of smooth surfaces of high density polyethylenes (HDPE) was performed with a view to improve the hydrophilic property of the surface.

The electromagnetic spectrum from 1 Hz to 9.4 GHz near ground level in the region of São José dos Campos, SP, Brazil

In the period from June 2012 to May 2013 measurements of the electromagnetic spectrum from 1 Hz to 9.4 GHz were collected in São José dos Campos, SP, Brazil. At this site, the electromagnetic spectrum is produced by both natural and artificial sources. The intensities of the electric and magnetic fields were measured in two frequency ranges (1 Hz to 1 MHz, and 1 MHz to 9.4 GHz) with hand-held detectors and compact antennas. Measurements were performed in sweep-time mode and changing precision in the resolution bandwidth (RBW). Main peaks in the spectrum correspond to Schumann resonances at 7.8, 14, 20 and 33 Hz, emissions by power lines, radio frequencies, navigational radio beacons, mobile phone and Wi-Fi systems, C- and X-band radars (ground stations and on board aircraft).