Examinando por Autor "Soto, L."
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Ítem Analysis of Deterioration in a Plasma Focus Device(Institute of Physics Publishing, 2018-06) Zanelli, D.; López, E.; Pavez, C.; Pedreros, J.; Jain, J.; Avaria, G.; Moreno, J.; Bora, B.; Davis, S.; Soto, L.The Plasma Focus (PF) is a kind of dense transient plasmas in with high-pulsed voltage. To produce devices for eld application it is necessary to obtain PF equipment able to operate for a long period of time. Thus, a reliability analysis is indispensable. In this work a reliability analysis program for plasma focus devices is presented. The program considers a criticality analysis using Failure Modes and Effects Criticality Analysis (FMECA) to identify the most important failure modes of the system. Said failure modes are studied operating the Plasma Focus for many cycles, obtaining from them the characteristic curves of V(t) and İ(t). Feature Extraction (FE) techniques are applied to obtain a list of parameters that correlate to the degrading process. Furthermore, Machine Learning tools are used to learn from the obtained data, linking the changes in these parameters during its life cycle to the decay of the system in hope for future implementation of a predictive maintenance system and a reference for data analysis and prediction in PFs. The study was applied to a portable plasma focus device operated at 2 joules of stored energy. © Published under licence by IOP Publishing Ltd.Ítem Bayesian inference of spectrometric data and validation with numerical simulations of plasma sheath diagnostics of a plasma focus discharge(Nature Research, 2022-09) Avaria, G.; Clausse, A.; Davis, S.; Pavez, C.; Villalba, N.; Cuadrado, O.; Moreno, J.; Ruiz, M.; Soto, L.Plasma Foci are pulsed coaxial discharges with numerous radiation applications and interesting scientific phenomena. Although the physics answered much of the processes involved in these discharges, many related fundamental questions still remains doggedly unresolved. One of the obstacles to deeper knowledge is the scarcity of reliable experimental data. This work presents an elaborate experimental assessment of the electron density in the rundown phase of a 400 J Plasma Focus operating with hydrogen. The rundown of the plasma sheath is basically a hypersonic shock wave between two coaxial electrodes accelerated by the Lorentz force, and it is important to control the pinch formation. The electron density of the passing sheath is measured by means of the Stark broadened hydrogen alpha emission with spatial and temporal resolution. The experimental data is post-processed using Bayesian posterior probability assessment. The results are conflated with the numerical model CShock to construe an educated explanation of the sheath behavior during the rundown. In particular, it is possible to reckon the formation of a toroidal instability reported in previous experiments, and to estimate the plasma sheath temperature (4–20 eV) and velocity (62.5 km/s) at this stage.Ítem Differential miRNA expression profiling reveals miR-205-3p to be a potential radiosensitizer for low- dose ionizing radiation in DLD-1 cells(Impact Journals LLC, 2018-05) Andaur, R.; Tapia, J.C.; Moreno, J.; Soto, L.; Armisen, R.; Marcelain, K.Enhanced radiosensitivity at low doses of ionizing radiation (IR) (0.2 to 0.6 Gy) has been reported in several cell lines. This phenomenon, known as low doses hyperradiosensitivity (LDHRS), appears as an opportunity to decrease toxicity of radiotherapy and to enhance the effects of chemotherapy. However, the effect of low single doses IR on cell death is subtle and the mechanism underlying LDHRS has not been clearly explained, limiting the utility of LDHRS for clinical applications. To understand the mechanisms responsible for cell death induced by low-dose IR, LDHRS was evaluated in DLD-1 human colorectal cancer cells and the expression of 80 microRNAs (miRNAs) was assessed by qPCR array. Our results show that DLD-1 cells display an early DNA damage response and apoptotic cell death when exposed to 0.6 Gy. miRNA expression profiling identified 3 over-expressed (miR-205-3p, miR-1 and miR-133b) and 2 downregulated miRNAs (miR-122-5p, and miR-134-5p) upon exposure to 0.6 Gy. This miRNA profile differed from the one in cells exposed to high-dose IR (12 Gy), supporting a distinct low-dose radiation-induced cell death mechanism. Expression of a mimetic miR- 205-3p, the most overexpressed miRNA in cells exposed to 0.6 Gy, induced apoptotic cell death and, more importantly, increased LDHRS in DLD-1 cells. Thus, we propose miR-205-3p as a potential radiosensitizer to low-dose IR. © Andaur et al.Ítem Experimental measurements of high-energy photons in X-rays pulses emitted from a hundred joules plasma focus device and its interpretations(Elsevier, 2020-03) Jain, J.; Moreno, J.; Davis, S.; Bora, B.; Pavez, C.; Avaria, G,; Soto, L.In the present work, efforts are made to identify the presence of high energy photons in X-rays pulses, emitted from a hundred joules plasma focus device, PF-400J. Two different experiments were carried out, with the insertion of a lead piece inside the hollow anode of PF-400J and without insertion of the lead piece. A pair of two photomultiplier tubes (PMTs) was mounted in the axial direction and a similar pair of PMTs was mounted in the radial direction, simultaneously. After establishing a correlation between two PMTs in each pair, one of the PMTs in both directions was blocked by a rectangular slab of the lead of thickness ~17 mm. Linear attenuation coefficient (LAC) of lead was estimated using the PMTs signals. Later, the X-rays energies were interpolated for the estimated LAC values in both cases, with and without insertion of lead piece inside the hollow anode. Interpolated energies reveal the presence of 0.55–0.85 MeV photons in the X-rays pulses in the axial direction, while, in radial direction ranges 0.4–0.9 MeV, for the case without lead inserted inside the hollow anode. Insertion of the lead inside the hollow anode does not change the X-rays energies significantly, nonetheless, it increases X-rays repetition rate per hundred discharges. The presence of high energy photons in the X-rays pulses indicates the existence of relativistic electrons. To explain it, induced electric and magnetic fields were estimated using generalized Ohm’s law. We conclude that the electron acceleration mechanisms might not be the same in the axial and radial directions.Ítem Hundred joules plasma focus device as a potential pulsed source for in vitro cancer cell irradiation(American Institute of Physics Inc., 2017-08) Jain, J.; Moreno, J.; Andaur, R.; Armisen, R.; Morales, D.; Marcelain, K.; Avaria, G.; Bora, B.; Davis, S.; Pavez, C.; Soto, L.Plasma focus devices may arise as useful source to perform experiments aimed to study the effects of pulsed radiation on human cells in vitro. In the present work, a table top hundred joules plasma focus device, namely "PF-400J", was adapted to irradiate colorectal cancer cell line, DLD-1. For pulsed x-rays, the doses (energy absorbed per unit mass, measured in Gy) were measured using thermoluminescence detectors (TLD-100 dosimeters). The neutron fluence and the average energy were used to estimate the pulsed neutron doses. Fifty pulses of x-rays (0.12 Gy) and fifty pulses of neutrons (3.5 μGy) were used to irradiate the cancer cells. Irradiation-induced DNA damage and cell death were assessed at different time points after irradiation. Cell death was observed using pulsed neutron irradiation, at ultralow doses. Our results indicate that the PF-400J can be used for in vitro assessment of the effect of pulsed radiation in cancer cell research.Ítem Influence of electrode geometry on X-ray emission, plasma inductance, voltage, and current derivative signals obtained from a plasma focus device(Elsevier B.V., 2021-04) Jain, J.; Moreno, J.; Bora, B.; Soto, L.Plasma focus devices have been investigated as a pulsed radiation source. Different studies have shown that the shape of the anode affects strongly the plasma dynamic and X-ray emission that takes place in plasma focus devices. In the present work, a hybrid-type plasma focus device (6 μF, 16 ± 1 kV), named PF-2kJ, is operated at various pressures of hydrogen gas with five cylindrical anodes of the same lengths but different in shapes, without cathode bars. The effect of cathode bars on various electric parameters is studied for the anode that has the maximum X-ray emission. The electrical signals of Rogowski coil (current derivative), voltage divider (voltage at the anode), and photomultiplier tubes (X-rays) were analyzed for all the anodes. Inductance and the voltage at the time of the pinch were derived from the measured voltage and current derivative signals. The X-ray dose measurements were performed using thermoluminescent dosimeters (TLD-100). The PF-2kJ performance is not the best while using the cathode bars. Our results show that by changing the anode shape just over the insulator sleeve the plasma focus devices can be switched between close energies stored in the capacitor bank. © 2021 The AuthorsÍtem Ion emission study using visible spectroscopy and ToF method in a plasma focus device of two kilojoules(Institute of Physics Publishing, 2015-03) Moreno, J.; Morales, D.; Avaria, G.; Cuadrado, O.; Soto, L.Different studies have been developed in order to understand the dynamics and processes involved in the particle emission from plasma focus devices operating in the kilo joule range. The use of chemical compound gasses and noble gas mixtures has proven to produce different charged particles, as well as increase the neutron yield from deuterium plasma discharges. Nevertheless, the processes and parameters involved in these discharges are not fully understood. In this work we will present results of visible spectroscopy and “time-of flight” observations of the different ion species and ionization levels obtained in a 2kJ plasma focus device, when using deuterium or hydrogen with small percentage impurities.Ítem Pulsed x-rays dose measurements from a hundred joules plasma focus device(Institute of Physics Publishing, 2018-06) Jain, J.; Moreno, J.; Avila, R.E.; Avaria, G.; Pavez, C.; Bora, B.; Davis, S.; Soto, L.Present work is aimed to perform dosimetric measurements to characterize dosis obtained from pulsed x-rays emitted from a hundred joules plasma focus device PF-400J using thermoluminescent dosimeters (TLD-100). Two dosimeter arrays (containing 21 dosimeters in each) were used. One of the arrays was kept inside the PF-400J vacuum chamber and other outside the vacuum chamber, simultaneously. It was found that dosis obtained from the inside array (∼200.7 mGy) were hundred times larger than the outside array (∼1.1 mGy) for hundred pulses of x-rays. Later, the vacuum window of PF-400J, which was made of 1 mm aluminum, was replaced by a plastic window and a similar dosimeter array was kept outside the chamber over the plastic window. With this arrangement, the obtained doses (100 pulses of x-rays) were of the same order of magnitude (∼106 mGy) as it was inside the vacuum chamber. Later, a lead piece was inserted inside the hollow anode of PF-400J, which increased dose (∼250 mGy) per hundred pulses of x-ray outside the vacuum chamber using plastic vacuum window. Our results suggest that PF-400J could be a useful device to study low dose pulsed radiation effects on cancer cell lines in in vitro experiments. © Published under licence by IOP Publishing Ltd.Ítem Ti film deposition process of a plasma focus: Study by an experimental design(American Institute of Physics Inc., 2017-10) Inestrosa-Izurieta, M.J.; Moreno, J.; Davis, S.; Soto, L.The plasma generated by plasma focus (PF) devices have substantially different physical characteristics from another plasma, energetic ions and electrons, compared with conventional plasma devices used for plasma nanofabrication, offering new and unique opportunities in the processing and synthesis of Nanomaterials. This article presents the use of a plasma focus of tens of joules, PF-50J, for the deposition of materials sprayed from the anode by the plasma dynamics in the axial direction. This work focuses on the determination of the most significant effects of the technological parameters of the system on the obtained depositions through the use of a statistical experimental design. The results allow us to give a qualitative understanding of the Ti film deposition process in our PF device depending on four different events provoked by the plasma dynamics: i) an electric erosion of the outer material of the anode; ii) substrate ablation generating an interlayer; iii) electron beam deposition of material from the center of the anode; iv) heat load provoking clustering or even melting of the deposition surface.