This work presents the design, constructioIl and parametrization of pulsed dye lasers, which are ... more This work presents the design, constructioIl and parametrization of pulsed dye lasers, which are economic and easily instrumented by undergraduate students without previous expe- rience. It ana1yzes the Littrow and grazing incidence configurations and presents simple alternatives to reduce the band width. Also studied are the threshold energy and the pump beam focus in didactic experiments. These lasers are pnmped by simple and economic N2 lasers that emit at ultraviolet wavelength (337 nmJ, which allows to pump dyes with emission spectrums from as low as 357 to 708 nm, and a tuning range between 30 and 60 nm.
We report the plasma parameters of a microwave discharge immersed in a magnetic field (ECR type) ... more We report the plasma parameters of a microwave discharge immersed in a magnetic field (ECR type) studied as a function of the type of gas used to induce the discharge. Plasma diagnostics included a Langmuir probe, an ion energy analyzer and an optical emission spectroscopy system. Results of the diagnostics are discussed in connection with the influence of the plasma parameters on the nitriding of steels. Different H 2 -N 2 mixtures were used to form the plasma and carry out the nitriding of AISI-316 stainless steel, with samples at the plasma floating potential, so that the energy of the ions hitting the sample surface depends on the difference between the plasma potential and the floating potential. Treatments were done in the low temperature regime (~ 450 C), where the steel keeps its anticorrosive properties and its structure corresponds to the so-called expanded austenite according to our X-ray diffraction results. The highest surface hardness was obtained when a 60-40 (H 2 -N 2 ) gas mixture was used, corresponding to a 380% hardness increase for a 50-min. treatment.
ABSTRACT In this work we report the plasma-wall interaction delay time and the impurity evolution... more ABSTRACT In this work we report the plasma-wall interaction delay time and the impurity evolution process in Novillo tokamak. The main design parameters of the Novillo tokamak are: mayor radius Ro = 23 cm, minor radius av = 8 cm, plasma radius ap = 6 cm, toroidal field BT = 4.7 kG, plasma current Ip = 12 kA, plasma density ne = 1-2 × 1013 cm-3, electron temperature Te = 150 eV, ion temperature Ti = 50 eV. In order to estimate the time delay between the initial plasma formation and when it hits the wall, we measured the temporal evolution of the emission of the oxygen line O I (lambda, = 7771 Å), the estimated delay was between 80-100 mus. The variation in the concentration of the impurities was monitored by changes in the intensity of the emission lines, from 4700 to 4960 Å, using a gated intensified charged-coupled device (ICCD) connected to a 0.5 m spectrograph. In this wavelength range the ICCD detects the He I singlet at lambda = 4713 Å and the He I triplet at lambda = 4922 Å. The Hbeta was used as a reference to calibrate the spectrograph. For 200 and 300 mus, the mayor impurities detected were C II at lambda = 4794 Å, N II at lambda = 4810 Å, C I at lambda = 4817 Å, C I at lambda = 4893 Å and Fe I at lambda = 4903 Å. We estimated the electron temperature evolution from the intensities using an addition of 10 % He to H2 as impurity.
With transparent target materials it is possible to get both front-side and rear-side laser ablat... more With transparent target materials it is possible to get both front-side and rear-side laser ablation. Rear-side laser ablation has been investigated as a new configuration for thin film deposition of transparent materials. In order to study the features of this configuration, the analysis of the propagation of laser ablation plumes of the rear and front-side plasmas was performed. The shock wave associated with rear and front-side ablation plumes were recorded by shadowgraphy and the corresponding velocities were determined in each case. We found a spherical wave front in both cases, with the shock wave of the rear-side plasma having a higher velocity. Optical emission spectroscopy measurements were carried out in order to identify the excited species present in each plasma
High voltage trigger pulses are required for initiating conduction in triggered spark gaps, xenon... more High voltage trigger pulses are required for initiating conduction in triggered spark gaps, xenon flashtubes, or to provide an ignition type pulse for other spedal devices requiring a high impcdance voltage source. This work describes the design, construction and operation of three prototypes: two high-voltage pulse generators and a spark-gap. For the first generator the F\VHM was 28.9 I's with an amplitude of 20.8 kV at frequencies of 1-12 Hz. For the secoud generator, the amplitude varied between 20-40 kV with a F\VHM of ;50 ns amI rise-times of 820 ns at a frequency of 0.3-18 Hz. The spark gap driveu by these generators works at voltages of up to 20 kV. In our case the gcnerators and the spark-gap were used to control lascr gaseous dischargcs. RESUMEN. Para controlar llaves rapidas (spark gaps), lamparas de xenon o para proveer de pulsos de disparo de aparatos que requieran de una fuente de alto voltaje se utilizan generadores de pulsos de alta tension. En este trabajo se presenta el diseno, construccion, caracterizacion y operacion de tres prototipos: dos generadores de pulsos de alta tension, uno electromecanico, otro totalmente electronico, y una llave rapida. Con el primero se han obtcnido pulsos de 20.8 kV con anchos medios de 28.9 I's a frecuencias de 1-12 Hz. Con el segundo se lograron pulsos de amplitud variable de 20 a 40 kV con anchos medios de ;50 ns y tiempos de subida de 820 os a frecuencias de 0.3- 18 Hz. La llave rapida controlada con estos generadores trabaja con tensiones de hasta 20 kV. Los generadores, junto eOIl el spark-gap, fueron utilizados para el control de laseres de descarga gaseosa.
Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation o... more Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation of a sintered ceramic SrFe 12 O 19 target with and without the presence of a nonhomogeneous magnetic field of m 0 H = 0.4 T perpendicular to substrate plane and parallel to the plasma expansion axis. The field was produced by a rectangular-shaped Nd-Fe-B permanent magnet and the substrate was just placed on the magnet surface (Aurora method). An appreciable increment of optical emission due to the presence of the magnetic field was observed, but no film composition change or thickness increment was obtained. It suggests that the increment of the optical emission is due mainly to the electron confinement rather than confinement of ionic species.
ABSTRACTA summary of experimental findings on the luminescence from conical bubble collapse, CBL ... more ABSTRACTA summary of experimental findings on the luminescence from conical bubble collapse, CBL is presented. Spatial, temporal, and spectral features of luminescence were investigated. In the experimental runs, two inert gases (Ar, Xe) and 1,2-Propanediol, PD, as work liquid were used. Single and multiple light emission events were recorded. Results show that there is a spectral evolution inside each pulse and through the whole experimental sequence. The average spectra consist of a broad continuum background, on which line emissions of OH°, CN, Na+, K+, and Swan lines are superimposed. An increase in continuum intensity from 300 to 860 nm was observed. The molecular and atomic lines as well as the continuum emission arise from different chemical pathways that take place during the bubble compression. Pathways come from the degradation of the liquid due to the repetition of the compression process, resulting in changes of the thermo-chemical conditions inside the cavity, such that...
Pampas deer (Ozotoceros bezoarticus) constitutes an emblematic species of the Southern cone grass... more Pampas deer (Ozotoceros bezoarticus) constitutes an emblematic species of the Southern cone grasslands due to its serious risk of extinction. Isolated populations are spread throughout some regions of Argentina, south of Brasil, and Uruguay. The main semicaptive population, with approximately 80 individuals, is located in Uruguay, at the Estación de Cría de Fauna Autóctona, Cerro Pan de Azúcar (34º3’ S, 55º1’ W). In this population we characterized the marking behavior, and its variation in relation to age and season. Further, since olfactory signals play a major role in mammal communication, we also characterized the main compounds of the cutaneous glands (preorbital, tarsal, and interdigital), as possible candidates of scent marking pheromones. Two groups of males, one of 6 adults (4-6 years old) and one of 6 yearlings (1.5 years old) were studied during 13 months. To typify marking behavior, an ethogram for the species was first described, and subsequently the frequency of each d...
. We report the plasma parameters of a microwave discharge immersed in a magnetic field ECR type ... more . We report the plasma parameters of a microwave discharge immersed in a magnetic field ECR type studied as a function of the type of gas used to induce the discharge. Plasma diagnostics included a Langmuir probe, an ion energy analyzer and an optical emission spectroscopy system. Results of the diagnostics are discussed in connection with the influence of the plasma parameters on the nitriding of steels. Different H rN mixtures were used to form the plasma and carry out the nitriding of 2 2 AISI-316 stainless steel, with samples at the plasma floating potential, so that the energy of the ions hitting the sample surface depends on the difference between the plasma potential and the floating potential. Treatments were carried out in the low Ž . temperature regime ; 450ЊC , where the steel keeps its anticorrosive properties and its structure corresponds to the so-called Ž . expanded austenite according to our X-ray diffraction results. The highest surface hardness was obtained when a 60:40 H rN 2 2 gas mixture was used, corresponding to a 380% hardness increase for a 50-min treatment. ᮊ 2000 Elsevier Science S.A. All rights reserved.
A summary of experimental findings on the luminescence from conical bubble collapse, CBL is prese... more A summary of experimental findings on the luminescence from conical bubble collapse, CBL is presented. Spatial, temporal, and spectral features of luminescence were investigated. In the experimental runs, two inert gases (Ar, Xe) and 1,2-Propanediol, PD, as work liquid were used. Single and multiple light emission events were recorded. Results show that there is a spectral evolution inside each pulse and through the whole experimental sequence. The average spectra consist of a broad continuum background, on which line emissions of OHº, CN, Na+, K+, and Swan lines are superimposed. An increase in continuum intensity from 300 to 860 nm was observed. The molecular and atomic lines as well as the continuum emission arise from different chemical pathways that take place during the bubble compression. Pathways come from the degradation of the liquid due to the repetition of the compression process, resulting in changes of the thermo-chemical conditions inside the cavity, such that each collapse was different. This becomes evident, by using low gas pressures, in which the luminescence was spatially and temporally non uniform. On the other hand if Xe instead of Ar is used the intensity of the luminescence increased one order of magnitude. These findings indicate that several components are presents in the bubble, besides the residual air and inert gas, vapor and liquid droplets, and within the latest water vapor, inert gas and alkali solutions are dissolved.
This work presents the design, constructioIl and parametrization of pulsed dye lasers, which are ... more This work presents the design, constructioIl and parametrization of pulsed dye lasers, which are economic and easily instrumented by undergraduate students without previous expe- rience. It ana1yzes the Littrow and grazing incidence configurations and presents simple alternatives to reduce the band width. Also studied are the threshold energy and the pump beam focus in didactic experiments. These lasers are pnmped by simple and economic N2 lasers that emit at ultraviolet wavelength (337 nmJ, which allows to pump dyes with emission spectrums from as low as 357 to 708 nm, and a tuning range between 30 and 60 nm.
We report the plasma parameters of a microwave discharge immersed in a magnetic field (ECR type) ... more We report the plasma parameters of a microwave discharge immersed in a magnetic field (ECR type) studied as a function of the type of gas used to induce the discharge. Plasma diagnostics included a Langmuir probe, an ion energy analyzer and an optical emission spectroscopy system. Results of the diagnostics are discussed in connection with the influence of the plasma parameters on the nitriding of steels. Different H 2 -N 2 mixtures were used to form the plasma and carry out the nitriding of AISI-316 stainless steel, with samples at the plasma floating potential, so that the energy of the ions hitting the sample surface depends on the difference between the plasma potential and the floating potential. Treatments were done in the low temperature regime (~ 450 C), where the steel keeps its anticorrosive properties and its structure corresponds to the so-called expanded austenite according to our X-ray diffraction results. The highest surface hardness was obtained when a 60-40 (H 2 -N 2 ) gas mixture was used, corresponding to a 380% hardness increase for a 50-min. treatment.
ABSTRACT In this work we report the plasma-wall interaction delay time and the impurity evolution... more ABSTRACT In this work we report the plasma-wall interaction delay time and the impurity evolution process in Novillo tokamak. The main design parameters of the Novillo tokamak are: mayor radius Ro = 23 cm, minor radius av = 8 cm, plasma radius ap = 6 cm, toroidal field BT = 4.7 kG, plasma current Ip = 12 kA, plasma density ne = 1-2 × 1013 cm-3, electron temperature Te = 150 eV, ion temperature Ti = 50 eV. In order to estimate the time delay between the initial plasma formation and when it hits the wall, we measured the temporal evolution of the emission of the oxygen line O I (lambda, = 7771 Å), the estimated delay was between 80-100 mus. The variation in the concentration of the impurities was monitored by changes in the intensity of the emission lines, from 4700 to 4960 Å, using a gated intensified charged-coupled device (ICCD) connected to a 0.5 m spectrograph. In this wavelength range the ICCD detects the He I singlet at lambda = 4713 Å and the He I triplet at lambda = 4922 Å. The Hbeta was used as a reference to calibrate the spectrograph. For 200 and 300 mus, the mayor impurities detected were C II at lambda = 4794 Å, N II at lambda = 4810 Å, C I at lambda = 4817 Å, C I at lambda = 4893 Å and Fe I at lambda = 4903 Å. We estimated the electron temperature evolution from the intensities using an addition of 10 % He to H2 as impurity.
With transparent target materials it is possible to get both front-side and rear-side laser ablat... more With transparent target materials it is possible to get both front-side and rear-side laser ablation. Rear-side laser ablation has been investigated as a new configuration for thin film deposition of transparent materials. In order to study the features of this configuration, the analysis of the propagation of laser ablation plumes of the rear and front-side plasmas was performed. The shock wave associated with rear and front-side ablation plumes were recorded by shadowgraphy and the corresponding velocities were determined in each case. We found a spherical wave front in both cases, with the shock wave of the rear-side plasma having a higher velocity. Optical emission spectroscopy measurements were carried out in order to identify the excited species present in each plasma
High voltage trigger pulses are required for initiating conduction in triggered spark gaps, xenon... more High voltage trigger pulses are required for initiating conduction in triggered spark gaps, xenon flashtubes, or to provide an ignition type pulse for other spedal devices requiring a high impcdance voltage source. This work describes the design, construction and operation of three prototypes: two high-voltage pulse generators and a spark-gap. For the first generator the F\VHM was 28.9 I's with an amplitude of 20.8 kV at frequencies of 1-12 Hz. For the secoud generator, the amplitude varied between 20-40 kV with a F\VHM of ;50 ns amI rise-times of 820 ns at a frequency of 0.3-18 Hz. The spark gap driveu by these generators works at voltages of up to 20 kV. In our case the gcnerators and the spark-gap were used to control lascr gaseous dischargcs. RESUMEN. Para controlar llaves rapidas (spark gaps), lamparas de xenon o para proveer de pulsos de disparo de aparatos que requieran de una fuente de alto voltaje se utilizan generadores de pulsos de alta tension. En este trabajo se presenta el diseno, construccion, caracterizacion y operacion de tres prototipos: dos generadores de pulsos de alta tension, uno electromecanico, otro totalmente electronico, y una llave rapida. Con el primero se han obtcnido pulsos de 20.8 kV con anchos medios de 28.9 I's a frecuencias de 1-12 Hz. Con el segundo se lograron pulsos de amplitud variable de 20 a 40 kV con anchos medios de ;50 ns y tiempos de subida de 820 os a frecuencias de 0.3- 18 Hz. La llave rapida controlada con estos generadores trabaja con tensiones de hasta 20 kV. Los generadores, junto eOIl el spark-gap, fueron utilizados para el control de laseres de descarga gaseosa.
Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation o... more Thin films were grown by pulsed laser deposition, PLD, on Si (1 0 0) substrates by the ablation of a sintered ceramic SrFe 12 O 19 target with and without the presence of a nonhomogeneous magnetic field of m 0 H = 0.4 T perpendicular to substrate plane and parallel to the plasma expansion axis. The field was produced by a rectangular-shaped Nd-Fe-B permanent magnet and the substrate was just placed on the magnet surface (Aurora method). An appreciable increment of optical emission due to the presence of the magnetic field was observed, but no film composition change or thickness increment was obtained. It suggests that the increment of the optical emission is due mainly to the electron confinement rather than confinement of ionic species.
ABSTRACTA summary of experimental findings on the luminescence from conical bubble collapse, CBL ... more ABSTRACTA summary of experimental findings on the luminescence from conical bubble collapse, CBL is presented. Spatial, temporal, and spectral features of luminescence were investigated. In the experimental runs, two inert gases (Ar, Xe) and 1,2-Propanediol, PD, as work liquid were used. Single and multiple light emission events were recorded. Results show that there is a spectral evolution inside each pulse and through the whole experimental sequence. The average spectra consist of a broad continuum background, on which line emissions of OH°, CN, Na+, K+, and Swan lines are superimposed. An increase in continuum intensity from 300 to 860 nm was observed. The molecular and atomic lines as well as the continuum emission arise from different chemical pathways that take place during the bubble compression. Pathways come from the degradation of the liquid due to the repetition of the compression process, resulting in changes of the thermo-chemical conditions inside the cavity, such that...
Pampas deer (Ozotoceros bezoarticus) constitutes an emblematic species of the Southern cone grass... more Pampas deer (Ozotoceros bezoarticus) constitutes an emblematic species of the Southern cone grasslands due to its serious risk of extinction. Isolated populations are spread throughout some regions of Argentina, south of Brasil, and Uruguay. The main semicaptive population, with approximately 80 individuals, is located in Uruguay, at the Estación de Cría de Fauna Autóctona, Cerro Pan de Azúcar (34º3’ S, 55º1’ W). In this population we characterized the marking behavior, and its variation in relation to age and season. Further, since olfactory signals play a major role in mammal communication, we also characterized the main compounds of the cutaneous glands (preorbital, tarsal, and interdigital), as possible candidates of scent marking pheromones. Two groups of males, one of 6 adults (4-6 years old) and one of 6 yearlings (1.5 years old) were studied during 13 months. To typify marking behavior, an ethogram for the species was first described, and subsequently the frequency of each d...
. We report the plasma parameters of a microwave discharge immersed in a magnetic field ECR type ... more . We report the plasma parameters of a microwave discharge immersed in a magnetic field ECR type studied as a function of the type of gas used to induce the discharge. Plasma diagnostics included a Langmuir probe, an ion energy analyzer and an optical emission spectroscopy system. Results of the diagnostics are discussed in connection with the influence of the plasma parameters on the nitriding of steels. Different H rN mixtures were used to form the plasma and carry out the nitriding of 2 2 AISI-316 stainless steel, with samples at the plasma floating potential, so that the energy of the ions hitting the sample surface depends on the difference between the plasma potential and the floating potential. Treatments were carried out in the low Ž . temperature regime ; 450ЊC , where the steel keeps its anticorrosive properties and its structure corresponds to the so-called Ž . expanded austenite according to our X-ray diffraction results. The highest surface hardness was obtained when a 60:40 H rN 2 2 gas mixture was used, corresponding to a 380% hardness increase for a 50-min treatment. ᮊ 2000 Elsevier Science S.A. All rights reserved.
A summary of experimental findings on the luminescence from conical bubble collapse, CBL is prese... more A summary of experimental findings on the luminescence from conical bubble collapse, CBL is presented. Spatial, temporal, and spectral features of luminescence were investigated. In the experimental runs, two inert gases (Ar, Xe) and 1,2-Propanediol, PD, as work liquid were used. Single and multiple light emission events were recorded. Results show that there is a spectral evolution inside each pulse and through the whole experimental sequence. The average spectra consist of a broad continuum background, on which line emissions of OHº, CN, Na+, K+, and Swan lines are superimposed. An increase in continuum intensity from 300 to 860 nm was observed. The molecular and atomic lines as well as the continuum emission arise from different chemical pathways that take place during the bubble compression. Pathways come from the degradation of the liquid due to the repetition of the compression process, resulting in changes of the thermo-chemical conditions inside the cavity, such that each collapse was different. This becomes evident, by using low gas pressures, in which the luminescence was spatially and temporally non uniform. On the other hand if Xe instead of Ar is used the intensity of the luminescence increased one order of magnitude. These findings indicate that several components are presents in the bubble, besides the residual air and inert gas, vapor and liquid droplets, and within the latest water vapor, inert gas and alkali solutions are dissolved.
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Papers by M. Villagrán