The potentiality of the digital holography technique applied to transparent objects is discussed ... more The potentiality of the digital holography technique applied to transparent objects is discussed in terms of the set of refractive optical diagnostics (Interferometry, Shadowgraphy and Schlieren technique), which can be reconstructed with a single interferometric record.
Lecture notes in electrical engineering, Nov 28, 2019
Pulsed plasma discharges are of interest for their capability to produce pulsed high energy radia... more Pulsed plasma discharges are of interest for their capability to produce pulsed high energy radiation and particle beams. One of them is the dense plasma focus, a device that has renewed interest for physics research and possible industrial applications. In this work, the evaluation of UHF antennas is carried out as an alternative remote diagnostic of this device. The measurements were taken from a low energy dense plasma focus device PF-400J operating at 26 kV of charging voltage and using hydrogen at a pressure of 9.5 mbar. The device operation was simultaneously measured with an inductive sensor, an inductive sensor loop, and an antenna. Two antennas were used for evaluating which one of them could be used as a complementary diagnostic of the device operation: a monopole and a Vivaldi antenna. Both antennas were tuned in the UHF range and were previously designed for measuring partial discharge phenomena. The characterization of the device operation with the antennas was carried out comparing the time domain signals of the antennas and the inductive sensor, whose signals features had been known beforehand. Then, for quantifying both types of measurements, signal parameters of the inductive sensor and the antennas were correlated. Peak value and signal energy were determined from the antennas signal and they were correlated with the dip value feature of the inductive sensor which is an important indicator of the plasma dynamic of the discharge. The results indicate that antennas can be used for the detection of abrupt changes in the circuit current of the device. In particular, the plasma maximum compression, known as pinch, could be inferred from the antenna signal as a transient that started when the dip feature was detected with an inductive measurement. The correlation between antenna signals parameter and the dip value of the inductive sensor showed high data dispersion, although an increasing trend of the antennas signal parameter with dip values was found. This work, as an initial experimental survey, concluded that UHF measurement techniques can be applied to the remote diagnostic of pulsed plasma discharges. The understanding of the emitting mechanism of the device and proper design of UHF sensors will be considered in future work.
In this work, new evidence and information about both the origin and evolution of filamentary str... more In this work, new evidence and information about both the origin and evolution of filamentary structures observed in the current sheath of a small plasma focus (PF) discharge are reported. The experiments were carried out in a small generator of low energy (multipurpose generator) at the PF configuration, under different operating conditions. These include different anode and insulator geometries, without return bars and in a high-performance regime of the generator at high pressures ( > 10 mbar). The evolution of the plasma structures is characterized by means of refractive optical techniques. The electrical behavior of the discharge, as well as its performance, are monitored with conventional electrical diagnostics and neutron and x-ray detectors, respectively. Plasma filaments of the same species are present in all tested configurations, however, in experiments with larger effective anode length (and smaller anode radii), the plasma region containing the filaments moves away f...
In the present work, a kilojoule plasma focus device, PF-2 kJ, is adopted as a pulsed x-ray sourc... more In the present work, a kilojoule plasma focus device, PF-2 kJ, is adopted as a pulsed x-ray source to study the effects of pulsed radiation in cancer cells. Low dose hyper-radiosensitivity (LDHRS) effects have been explored in various cancer cell lines using conventional x-ray irradiation. To the best of our knowledge, the LDHRS effects have not yet been explored using pulsed x-rays. Cell death was evaluated in human colorectal (DLD-1 and HCT-116) and breast (MCF-7) cancer cell lines (monolayer cell cultures) irradiated with 10 (∼0.24 Gy), 20 (0.61 Gy), and 40 (∼1.1 Gy) pulses (FWHM ∼ 90 ns, dose rate ∼107 Gy/min with a dose of 0.025 Gy per pulse). The LDHRS cell death effect in the DLD-1 cell line irradiated with pulsed x-ray is three times higher than the reported for a conventional continuous x-ray source at two times higher doses. LDHRS was also observed in HCT-116 and MCF-7 cells exposed to 10 and 20 x-ray pulses, respectively, which are reported not to exhibit LDHRS when conve...
Pulsed plasma discharges are of interest for their capability to produce pulsed high energy radia... more Pulsed plasma discharges are of interest for their capability to produce pulsed high energy radiation and particle beams. One of them is the dense plasma focus, a device that has renewed interest for physics research and possible industrial applications. The plasma produced with this device corresponds to the z-pinch phenomena and lasts between 1–10 ns. Electrical quantities such as the voltage across the electrodes of the vacuum chamber where the plasma dynamic takes place and the circuit current are used for the diagnostic of these devices. The short duration of the high density plasma that is produced implies a challenge when choosing a proper sensor. Typically, Rogowski coils wrapped around a conductor are used for measuring the time derivative of the circuit current. The reproducibility of Rogowski coils and variation of its frequency response due to movements can be an issue. An inductive loop sensor was developed as an alternative to measure fast and low amplitude transients of partial discharges. In this work, the use of the inductive loop sensor is proposed as an alternative sensor for the dense plasma focus operation measurement. Simultaneous measurements of both the Rogowski coil and inductive loop sensor were carried out on a low energy dense plasma focus. A comparison between both sensors was made in time and time-frequency domains. Wavelet transform was used in the time-frequency analysis. Further studies regarding the pinch detection were made with correlations between the signal values at this particular instant of the device operation. The results indicated that similar results in the characterization of the dense plasma focus operation can be obtained with the inductive loop sensor. In terms of the frequency response at time of pinch both sensors yielded similar results. A linear tendency between the signal values at time of pinch was found. Future work will be carried out to fully adapt the inductive loop sensor for its application in pulsed power technology.
Abstract Plasma focus devices have been investigated as a pulsed radiation source. Different stud... more Abstract 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 μ F, 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.
Charged particle (CP) measurements in dense plasma focus (DPF) devices are important to understan... more Charged particle (CP) measurements in dense plasma focus (DPF) devices are important to understand the fundamentals of the CP acceleration mechanism, which is under active investigation. In this work, the results of the CP (ion) measurements obtained from a kilojoule DPF device, PF-2 kJ, are presented. The ion signals were observed in the pressure range of 3–11 mbar of hydrogen gas. The ion signals were recorded by means of Faraday cups (FCs). One FC was mounted in the axial direction, and two FCs were mounted in radial directions (at 180° to each other). Three distinct signals of ions were observed in the FC that was in the axial direction and two in the FCs that were in the radial direction. Later, the ion signals were converted into number densities [NDs (m−3)] at each pressure. The maximum NDs were found at 3 mbar in both directions. The variation in the NDs with pressures suggests the existence of more than one ion acceleration mechanism in the PF-2 kJ. Moreover, at the lower p...
This study presents an optical assembly and digital reconstruction method that is based on digita... more This study presents an optical assembly and digital reconstruction method that is based on digital holography for characterizing transparent objects. The image-plane optical setup is based on a versatile Mach-Zehnder interferometer for the formation of controlled parallel fringe patterns, of tens micrometers of separations or less. The numerical reconstruction of the propagated wavefront by the hologram is performed by the Fresnel-Kirchhoff transform, and it is used of three ways: (a) interferometric phase reconstruction (as in interferometry) in the phase object position, (b) reconstruction of the wavefront amplitude at a determined distance from the object (shadowgraph technique), and (c) a composed digital reconstruction process of the wavefront amplitude, defined by a digital optical assembly for the selection of angular deflections produced by the phase object (schlieren technique). The resolving power of holographic reconstruction methodology proposed is determined by the sens...
2016 IEEE International Conference on Automatica (ICA-ACCA), 2016
In this work a multi-frame interferometric system based in digital image processing and digital i... more In this work a multi-frame interferometric system based in digital image processing and digital interferometry is presented. Here, an experimental optical setup which integrates the virtues of the digital interferometry technique and the capacity to capture two interferograms, to two different times, in a single digital recording system is implemented. The digital reconstruction of the interferograms required the capture of three interferometric patterns of very thin parallel fringes (15-20 lines/mm), one of them with information of the phase object and the other two are interferometric patterns of reference. One of the referential pattern is captured in the same condition as the one with plasma and the other one slightly changing the frequency of the pattern fringes. The interferogram associated with each instant of time is separated by means of spatial filtering techniques. Thus, the technique allows obtain digital interferograms in fringes of infinite and finite width in two different times. The interferometric system was tested in a laser-induced spark plasma in air.
The potentiality of the digital holography technique applied to transparent objects is discussed ... more The potentiality of the digital holography technique applied to transparent objects is discussed in terms of the set of refractive optical diagnostics (Interferometry, Shadowgraphy and Schlieren technique), which can be reconstructed with a single interferometric record.
Lecture notes in electrical engineering, Nov 28, 2019
Pulsed plasma discharges are of interest for their capability to produce pulsed high energy radia... more Pulsed plasma discharges are of interest for their capability to produce pulsed high energy radiation and particle beams. One of them is the dense plasma focus, a device that has renewed interest for physics research and possible industrial applications. In this work, the evaluation of UHF antennas is carried out as an alternative remote diagnostic of this device. The measurements were taken from a low energy dense plasma focus device PF-400J operating at 26 kV of charging voltage and using hydrogen at a pressure of 9.5 mbar. The device operation was simultaneously measured with an inductive sensor, an inductive sensor loop, and an antenna. Two antennas were used for evaluating which one of them could be used as a complementary diagnostic of the device operation: a monopole and a Vivaldi antenna. Both antennas were tuned in the UHF range and were previously designed for measuring partial discharge phenomena. The characterization of the device operation with the antennas was carried out comparing the time domain signals of the antennas and the inductive sensor, whose signals features had been known beforehand. Then, for quantifying both types of measurements, signal parameters of the inductive sensor and the antennas were correlated. Peak value and signal energy were determined from the antennas signal and they were correlated with the dip value feature of the inductive sensor which is an important indicator of the plasma dynamic of the discharge. The results indicate that antennas can be used for the detection of abrupt changes in the circuit current of the device. In particular, the plasma maximum compression, known as pinch, could be inferred from the antenna signal as a transient that started when the dip feature was detected with an inductive measurement. The correlation between antenna signals parameter and the dip value of the inductive sensor showed high data dispersion, although an increasing trend of the antennas signal parameter with dip values was found. This work, as an initial experimental survey, concluded that UHF measurement techniques can be applied to the remote diagnostic of pulsed plasma discharges. The understanding of the emitting mechanism of the device and proper design of UHF sensors will be considered in future work.
In this work, new evidence and information about both the origin and evolution of filamentary str... more In this work, new evidence and information about both the origin and evolution of filamentary structures observed in the current sheath of a small plasma focus (PF) discharge are reported. The experiments were carried out in a small generator of low energy (multipurpose generator) at the PF configuration, under different operating conditions. These include different anode and insulator geometries, without return bars and in a high-performance regime of the generator at high pressures ( > 10 mbar). The evolution of the plasma structures is characterized by means of refractive optical techniques. The electrical behavior of the discharge, as well as its performance, are monitored with conventional electrical diagnostics and neutron and x-ray detectors, respectively. Plasma filaments of the same species are present in all tested configurations, however, in experiments with larger effective anode length (and smaller anode radii), the plasma region containing the filaments moves away f...
In the present work, a kilojoule plasma focus device, PF-2 kJ, is adopted as a pulsed x-ray sourc... more In the present work, a kilojoule plasma focus device, PF-2 kJ, is adopted as a pulsed x-ray source to study the effects of pulsed radiation in cancer cells. Low dose hyper-radiosensitivity (LDHRS) effects have been explored in various cancer cell lines using conventional x-ray irradiation. To the best of our knowledge, the LDHRS effects have not yet been explored using pulsed x-rays. Cell death was evaluated in human colorectal (DLD-1 and HCT-116) and breast (MCF-7) cancer cell lines (monolayer cell cultures) irradiated with 10 (∼0.24 Gy), 20 (0.61 Gy), and 40 (∼1.1 Gy) pulses (FWHM ∼ 90 ns, dose rate ∼107 Gy/min with a dose of 0.025 Gy per pulse). The LDHRS cell death effect in the DLD-1 cell line irradiated with pulsed x-ray is three times higher than the reported for a conventional continuous x-ray source at two times higher doses. LDHRS was also observed in HCT-116 and MCF-7 cells exposed to 10 and 20 x-ray pulses, respectively, which are reported not to exhibit LDHRS when conve...
Pulsed plasma discharges are of interest for their capability to produce pulsed high energy radia... more Pulsed plasma discharges are of interest for their capability to produce pulsed high energy radiation and particle beams. One of them is the dense plasma focus, a device that has renewed interest for physics research and possible industrial applications. The plasma produced with this device corresponds to the z-pinch phenomena and lasts between 1–10 ns. Electrical quantities such as the voltage across the electrodes of the vacuum chamber where the plasma dynamic takes place and the circuit current are used for the diagnostic of these devices. The short duration of the high density plasma that is produced implies a challenge when choosing a proper sensor. Typically, Rogowski coils wrapped around a conductor are used for measuring the time derivative of the circuit current. The reproducibility of Rogowski coils and variation of its frequency response due to movements can be an issue. An inductive loop sensor was developed as an alternative to measure fast and low amplitude transients of partial discharges. In this work, the use of the inductive loop sensor is proposed as an alternative sensor for the dense plasma focus operation measurement. Simultaneous measurements of both the Rogowski coil and inductive loop sensor were carried out on a low energy dense plasma focus. A comparison between both sensors was made in time and time-frequency domains. Wavelet transform was used in the time-frequency analysis. Further studies regarding the pinch detection were made with correlations between the signal values at this particular instant of the device operation. The results indicated that similar results in the characterization of the dense plasma focus operation can be obtained with the inductive loop sensor. In terms of the frequency response at time of pinch both sensors yielded similar results. A linear tendency between the signal values at time of pinch was found. Future work will be carried out to fully adapt the inductive loop sensor for its application in pulsed power technology.
Abstract Plasma focus devices have been investigated as a pulsed radiation source. Different stud... more Abstract 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 μ F, 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.
Charged particle (CP) measurements in dense plasma focus (DPF) devices are important to understan... more Charged particle (CP) measurements in dense plasma focus (DPF) devices are important to understand the fundamentals of the CP acceleration mechanism, which is under active investigation. In this work, the results of the CP (ion) measurements obtained from a kilojoule DPF device, PF-2 kJ, are presented. The ion signals were observed in the pressure range of 3–11 mbar of hydrogen gas. The ion signals were recorded by means of Faraday cups (FCs). One FC was mounted in the axial direction, and two FCs were mounted in radial directions (at 180° to each other). Three distinct signals of ions were observed in the FC that was in the axial direction and two in the FCs that were in the radial direction. Later, the ion signals were converted into number densities [NDs (m−3)] at each pressure. The maximum NDs were found at 3 mbar in both directions. The variation in the NDs with pressures suggests the existence of more than one ion acceleration mechanism in the PF-2 kJ. Moreover, at the lower p...
This study presents an optical assembly and digital reconstruction method that is based on digita... more This study presents an optical assembly and digital reconstruction method that is based on digital holography for characterizing transparent objects. The image-plane optical setup is based on a versatile Mach-Zehnder interferometer for the formation of controlled parallel fringe patterns, of tens micrometers of separations or less. The numerical reconstruction of the propagated wavefront by the hologram is performed by the Fresnel-Kirchhoff transform, and it is used of three ways: (a) interferometric phase reconstruction (as in interferometry) in the phase object position, (b) reconstruction of the wavefront amplitude at a determined distance from the object (shadowgraph technique), and (c) a composed digital reconstruction process of the wavefront amplitude, defined by a digital optical assembly for the selection of angular deflections produced by the phase object (schlieren technique). The resolving power of holographic reconstruction methodology proposed is determined by the sens...
2016 IEEE International Conference on Automatica (ICA-ACCA), 2016
In this work a multi-frame interferometric system based in digital image processing and digital i... more In this work a multi-frame interferometric system based in digital image processing and digital interferometry is presented. Here, an experimental optical setup which integrates the virtues of the digital interferometry technique and the capacity to capture two interferograms, to two different times, in a single digital recording system is implemented. The digital reconstruction of the interferograms required the capture of three interferometric patterns of very thin parallel fringes (15-20 lines/mm), one of them with information of the phase object and the other two are interferometric patterns of reference. One of the referential pattern is captured in the same condition as the one with plasma and the other one slightly changing the frequency of the pattern fringes. The interferogram associated with each instant of time is separated by means of spatial filtering techniques. Thus, the technique allows obtain digital interferograms in fringes of infinite and finite width in two different times. The interferometric system was tested in a laser-induced spark plasma in air.
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