Felipe Veloso | Pontificia Universidad Catolica de Chile (original) (raw)
Papers by Felipe Veloso
Review of Scientific Instruments, Jun 1, 2021
Talbot-Lau x-ray interferometry has been implemented to map electron density gradients in High En... more Talbot-Lau x-ray interferometry has been implemented to map electron density gradients in High Energy Density Physics (HEDP) experiments. X-ray backlighter targets have been evaluated for Talbot-Lau X-ray Deflectometry (TXD). Cu foils, wires, and sphere targets have been irradiated by 10–150 J, 8–30 ps laser pulses, while two pulsed-power generators (∼350 kA, 350 ns and ∼200 kA, 150 ns) have driven Cu wire, hybrid, and laser-cut x-pinches. A plasma ablation front generated by the Omega EP laser was imaged for the first time through TXD for densities >1023 cm−3. Backlighter optimization in combination with x-ray CCD, image plates, and x-ray film has been assessed in terms of spatial resolution and interferometer contrast for accurate plasma characterization through TXD in pulsed-power and high-intensity laser environments. The results obtained thus far demonstrate the potential of TXD as a powerful diagnostic for HEDP.
![Research paper thumbnail of Publisher’s Note: “Talbot-Lau x-ray deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments (invited)” [Rev. Sci. Instrum. 87, 11D501 (2016)]](https://attachments.academia-assets.com/109238993/thumbnails/1.jpg)
](Review of Scientific Instruments, Aug 15, 2016
Publisher's Note: "Talbot-Lau x-ray deflectometer electron density diagnostic for laser and pulse... more Publisher's Note: "Talbot-Lau x-ray deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments (invited)" [Rev. Sci. Instrum. 87, 11D501 (2016)]
Low-temperature non-thermal plasmas (LTPs) produce highly reactive chemical environments made up ... more Low-temperature non-thermal plasmas (LTPs) produce highly reactive chemical environments made up of electrons, ions, radicals, and vibrationally excited molecules. These reactive species, when combined with catalysts, can help drive thermodynamically unfavorable chemical reactions at low temperatures and atmospheric pressure. One potential area of impact is the direct coupling of methane (CH4) with nitrogen (N2) to produce value-added chemicals via a plasma-assisted catalytic process. To effectively create these plasma catalytic systems, a fundamental understanding of the plasma-phase chemistry alone is imperative. While there have been many studies on methane plasmas and how certain operating conditions (i.e., gas composition and power) affect the plasma, there is limited understanding on how changing bulk reaction temperature affects the plasma properties and ensuing plasma chemistry. In this work, we use a dielectric barrier discharge (DBD) to investigate the effects of temperatu...
Results in Physics, 2021
We report the effect of single and dual radio frequency (RF) plasma discharge on the composition ... more We report the effect of single and dual radio frequency (RF) plasma discharge on the composition and dynamics of a titanium plasma plume produced in a plasma-enhanced pulsed laser deposition (PE-PLD) system. The study was carried out in a nitrogen environment at different pressures. Time-resolved images, optical emission spectroscopy, and interferometry were employed to analyze the plasma. We were able to fit time-resolved images using different expansion models, obtained an expansion velocity between 6 and 30 x 10 3 m/s. Emission lines from N II, Ti II, were observed by changing the pressure and RF conditions. An increase in emission line intensity from N II was observed by increasing the pressure and RF power. We used Ti II lines to estimate the plasma temperature by using the Boltzmann equation, and we obtained the density from the Ti II line (454.9 nm) through Stark broadening. In addition, a Mach-Zehnder interferometer was employed to make a twodimensional map of the electron density at early times. The estimated temperatures and densities are between 0.8-2.0 eV and 10 17-10 18 cm-3 , respectively. The results suggest that increasing RF power enhanced the TiN atoms interaction, which is crucial in titanium nitride film applications.
Bulletin of the American Physical Society, 2020
The use of a copper X-pinch as backlighting source for Talbot-Lau X-ray Deflectometry (TXD) is pr... more The use of a copper X-pinch as backlighting source for Talbot-Lau X-ray Deflectometry (TXD) is presented. The TXD technique can provide information about density gradients and elemental composition in HED plasmas, through single-image x-ray refraction and attenuation. In order to test the system in pulsed power environments, a TXD was implemented using a Cu X-pinch as X-ray source in the Llampüdkeñ generator (˜350kA in˜350ns). A minimum source size of˜50um was measured at the crossing point, with pulses of <2ns; as well as an extended x-ray source from the anode side of the array. Characteristic x-rays, as well as a broad continuum under 5keV were detected. A Be object is used as probing object, measuring its density with a difference <13%. No damage from debris or magnetic field was observed in the gratings used for TXD, but it is shown that a protective filter is required. These results are relevant in order to adapt and design further pulsed power experiments that aim to use the Talbot-Lau technique to characterize pulsed plasmas.
Bulletin of the American Physical Society, 2015
We have performed experimental studies of the effect of static axial magnetic fields on the plasm... more We have performed experimental studies of the effect of static axial magnetic fields on the plasma dynamics of laser produced carbon and titanium plasmas. The laser plasmas are produced in vacuum, with a Nd:YAG laser, 3.5 ns, 340 mJ at 1.06 4 µm, operating at 10 Hz, and propagate in static magnetic fields of maximum value ∼0.2 T. Laser plasma features are characterized using 50 ns time resolved plasma imaging, time and space resolved visible spectroscopy and Faraday cup measurements. The presence of the magnetic field is found to affect plasma dynamics, plasma emission and plasma ions energy spectrum. Based on these measurements, a detailed analysis of the confinement effects of the magnetic field on the laser plasma will be presented.
En este trabajo se presenta la comparacion entre simulaciones numericas de descargas en el dispos... more En este trabajo se presenta la comparacion entre simulaciones numericas de descargas en el dispositivo Plasma Focus llamado PF-50J utilizando el codigo CShock. El codigo fue capaz de reproducir las mediciones de la cinematica y de los parametros del circuito electrico asi como la inestabilidad particular que se produce en la lamina de corriente observada en este dispositivo en particular.
2018 IEEE International Conference on Plasma Science (ICOPS), 2018
A ring shape plasma can be produced by focusing a laser beam over a solid target, using a combina... more A ring shape plasma can be produced by focusing a laser beam over a solid target, using a combination of ax icon prism and convergent lens1. We present preliminary experimental studies of the dynamics of an annular plasma in background gases. The initial plasma is produced by focusing a Nd:YAG laser beam (1064 nm, 3.5 ns FWHM, −2cdot109-2\cdot 10^{9}−2cdot109 W / cm2) onto a flat target employing a combination of a 10 mrad axicon prism and a converging lens, which results in an initial ringlike shape plasma of 1 mm radius and sim150mumathrmn\sim 150\mu\mathrm{n}sim150mumathrmn thickness. Observations of the optical self-emission of Titanium plasmas at 80 mTorr Argon background indicate that the plasma propagates inwards in a time scale ~90 ns, which is then followed by on axis stagnation and formation of a jet-like column. The resulting plasma jet propagates axially forming a planar shock, with characteristic initial velocity sim2cdot106\sim 2\cdot 10^{6}sim2cdot106 cm/s. This planar shock transits to a bow-shock in characteristic timescales of ~600 ns. Further investigations employing two parallel coaxial NdFeB magnets, which produce a static magnetic field of ~0.1 T, suggest that confinement effects due to the magnetic field increases the transition time from planar to bow-shock to ~ 700 ns. Additional experiments have been conducted with Graphite and Titanium target in high pressure Argon and air backgrounds. By using schlieren laser imaging (532 nm, 3.5 ns FWHM) from Carbon and Titanium annular plasmas it is found that the characteristic on-axis stagnation times increase up to ~300 ns at 760 Torr. In a first approximation, both, the radial expansion of the annular plasma and the axial propagation of the resulting plasma jet can be described adequately by the drag model2. Based on these observations, a comprehensive description of the dynamics of laser produced annular plasmas, over a wide set of parameters, will be presented.
Physics of Plasmas, 2018
A series of experimental measurements of fast ions generated in a tungsten conical wire array are... more A series of experimental measurements of fast ions generated in a tungsten conical wire array are presented. The ions are detected using a set of negatively biased Faraday cups located on axis above the array at distances between 10 and 67 cm. Significant differences in the signals from the probes are found on varying the background atmospheric pressure between 10−2 and 10−5 Torr. At 10−5 Torr, a pulse of ions moving at 106 m/s is collected by the cups. In contrast, at intermediate (10−4 Torr) and high (10−2 Torr) pressures, both electrons and ions are detected with a velocity of order 106 m/s. The differences with pressure are ascribed to the ionization of the background gas by the tungsten ions. Time-of-flight measurements show the emission of fast ions during the ablation phase of wire array dynamics. Comparing the temporal behavior of the ions and their velocity of propagation with the dynamics observed using UltraViolet / eXtreme UltraViolet imaging allows us to conclude that t...
Journal of Physics: Conference Series, 2016
We present preliminary experimental observations of the collision processes between two orthogona... more We present preliminary experimental observations of the collision processes between two orthogonal laser produced plasmas in a low pressure neutral gas background. A Nd:YAG laser, 340 mJ, 3.5 ns, at 1.06 µm, operating at 10 Hz, is used in the experiments. The main laser beam is divided in two beams by a 50% beam splitter, and then focused over two rotating graphite targets, with characteristic fluence 3.5 J/cm 2. Experiments are conducted in a range from a base pressure of 0.3 mTorr, up to 50 mTorr argon. The dynamics of the laser plasmas is characterized by time resolved and time integrated optical emission spectroscopy (OES), with 20 ns and 10 ms time resolution, and 50 ns time resolved plasma imaging of visible plasma emission. Clear effects of the neutral gas background on the postcollision plasma dynamics are identified. The overall dynamics of the post-collision plasma is found to be consistent with high collisionality of the carbon plasma plumes, which results in full stagnation on collisioning.
IEEE Transactions on Plasma Science, 2012
Abstract Wire-array $ Z −pinchexperimentshavebeenperformedontheLlampu¨dkengenerator(-pinch experiments have been performed on the Llampüdkeñ generator (−pinchexperimentshavebeenperformedontheLlampu¨dkengenerator( si... more Abstract Wire-array $ Z −pinchexperimentshavebeenperformedontheLlampu¨dkengenerator(-pinch experiments have been performed on the Llampüdkeñ generator (−pinchexperimentshavebeenperformedontheLlampu¨dkengenerator( sim 470kAin470 kA in 470kAin sim $410 ns)[Chuaqui et al., Laser Part. Beams 15, 241 (1997)] using an overmassed load of aluminum wires. Time-resolved optical laser schlieren and extreme ultraviolet imaging were used in order to study the plasma ablation dynamics. The results show the formation and subsequent ablation of plasma from the wires, followed by the appearance of a precursor plasma column on the axis. According to these results ...
Journal of Physics: Conference Series, 2018
We present preliminary experimental observations of the plasma dynamics of laser produced annular... more We present preliminary experimental observations of the plasma dynamics of laser produced annular plasmas, expanding freely in a 80 mTorr Argon background. A Nd:YAG laser, 340 mJ, 3.5 ns, at 1.06 µm, operating at 10 Hz, is used in the experiments. To produce the annular plasma the laser pulse is focused on a titanium target using a combination of axicon and convergent lens. The dynamics of the laser plasma is characterized by 50 ns time resolved plasma imaging of the visible plasma emission. The inwards radial expansion of the initial plasma ring result in on-axis stagnation, giving rise to an expanding axial laser plasma plume. A quantitative description of the laser plasma dynamics is presented.
Physics Education
Water waves in the ocean can be easily observed at any place regardless of the distance from the ... more Water waves in the ocean can be easily observed at any place regardless of the distance from the shore. However, measurements of wave speeds with respect to the ground can be rather complicated due to the non-trivial oscillation water does. In this article, indirect measurements of the speed of shallow water waves are made after observations of shapes in the undertow water current over the beach sand. The measurements were taken using only a video recorded with a smartphone camera and no additional hardware. These particular shapes take the form of conical shock fronts (also known as Mach cones) which relate the speed of the undertow current with the water wave speed. Using this technique, a Mach number of M = 3.0 ± 0.2 and wave speeds of c wave = (19 ± 2) cm s−1 are obtained which agree with shallow wave speed equations.
Bulletin of the American Physical Society, 2016
Bulletin of the American Physical Society, 2015
Results in physics, 2020
A novel application for conical wire array Z-pinches to surface science is presented. The axial o... more A novel application for conical wire array Z-pinches to surface science is presented. The axial outflows emitted by a tungsten conical wire array in the form of both a dense plasma jet and energetic ions are used to produce morphological modification of substrate surfaces without using any kind of chemical treatment. In particular, surface modifications of (100) oriented Si substrates in the form of micropores and stripes-like formations after a single interaction of the Si to the axial outflows are obtained. It is found that the prevalence of each kind of formation, either micropores or stripes, on the treated substrate depends on the relative position of the target with respect to the wire array. The results indicate that at distances of 11cm over the array there is still effect of the dense plasma jet outflow since both micropores and stripes are found. On the contrary, solely stripe-like patterns are found at greater distances where the effect of the dense plasma outflow is mini...
, FONDECYT COLLABORATION , PLASMA TEAM-Dual radio frequency capacitively coupled plasma assisted ... more , FONDECYT COLLABORATION , PLASMA TEAM-Dual radio frequency capacitively coupled plasma assisted pulsed laser deposition (PA-PLD) have the advantage of preventing the microparticles reaching the substrate during thin film depositions. The plasma DC selfbias activates the substrate surface and destroy the large micro-particles reaching on it. The dual frequency offers the advantage of controlling the ion bombardment energy independently of the ion flux by tuning the low frequency (LF) power. We have compared transition metal nitride thin films such as the titanium nitride (TiN) and tungsten nitride (WN) in the hybrid configuration PAPLD. Optical emission spectroscopy was carried out during deposition. Standard surface science diagnostics like, x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy and atomic force microscopy were used to characterize the deposited thin films. A comparative analysis of the thin films deposited by conventional PLD and PA-PLD, has shown that the PA-PLD technique improves the quality of the deposited films with respect to their stoichiometry, morphology and deposition rate.
Journal of Physics: Conference Series
The use of copper x-pinch plasmas as backlighting source for radiographing insects is described. ... more The use of copper x-pinch plasmas as backlighting source for radiographing insects is described. The experiments use 4x 25m Cu wires driven by a ~400kA, ~350ns current pulse to produce a localized source of soft x-rays in the micrometer range. Both source size and energy range of the x-rays photons produced by the x-pinch enable the imaging of low contrast objects such as the rich inner structures of insects with excellent spatial resolution. The technique is used in three different insects: a moth, a fly and a beetle. These radiographies allow clear observation of the details of outer (e.g., wings) and internal systems of the insects. A description of the method and ways to improve the quality of the radiographs are shown and discussed.
Review of Scientific Instruments, Jun 1, 2021
Talbot-Lau x-ray interferometry has been implemented to map electron density gradients in High En... more Talbot-Lau x-ray interferometry has been implemented to map electron density gradients in High Energy Density Physics (HEDP) experiments. X-ray backlighter targets have been evaluated for Talbot-Lau X-ray Deflectometry (TXD). Cu foils, wires, and sphere targets have been irradiated by 10–150 J, 8–30 ps laser pulses, while two pulsed-power generators (∼350 kA, 350 ns and ∼200 kA, 150 ns) have driven Cu wire, hybrid, and laser-cut x-pinches. A plasma ablation front generated by the Omega EP laser was imaged for the first time through TXD for densities >1023 cm−3. Backlighter optimization in combination with x-ray CCD, image plates, and x-ray film has been assessed in terms of spatial resolution and interferometer contrast for accurate plasma characterization through TXD in pulsed-power and high-intensity laser environments. The results obtained thus far demonstrate the potential of TXD as a powerful diagnostic for HEDP.
Review of Scientific Instruments, Aug 15, 2016
Publisher's Note: "Talbot-Lau x-ray deflectometer electron density diagnostic for laser and pulse... more Publisher's Note: "Talbot-Lau x-ray deflectometer electron density diagnostic for laser and pulsed power high energy density plasma experiments (invited)" [Rev. Sci. Instrum. 87, 11D501 (2016)]
Low-temperature non-thermal plasmas (LTPs) produce highly reactive chemical environments made up ... more Low-temperature non-thermal plasmas (LTPs) produce highly reactive chemical environments made up of electrons, ions, radicals, and vibrationally excited molecules. These reactive species, when combined with catalysts, can help drive thermodynamically unfavorable chemical reactions at low temperatures and atmospheric pressure. One potential area of impact is the direct coupling of methane (CH4) with nitrogen (N2) to produce value-added chemicals via a plasma-assisted catalytic process. To effectively create these plasma catalytic systems, a fundamental understanding of the plasma-phase chemistry alone is imperative. While there have been many studies on methane plasmas and how certain operating conditions (i.e., gas composition and power) affect the plasma, there is limited understanding on how changing bulk reaction temperature affects the plasma properties and ensuing plasma chemistry. In this work, we use a dielectric barrier discharge (DBD) to investigate the effects of temperatu...
Results in Physics, 2021
We report the effect of single and dual radio frequency (RF) plasma discharge on the composition ... more We report the effect of single and dual radio frequency (RF) plasma discharge on the composition and dynamics of a titanium plasma plume produced in a plasma-enhanced pulsed laser deposition (PE-PLD) system. The study was carried out in a nitrogen environment at different pressures. Time-resolved images, optical emission spectroscopy, and interferometry were employed to analyze the plasma. We were able to fit time-resolved images using different expansion models, obtained an expansion velocity between 6 and 30 x 10 3 m/s. Emission lines from N II, Ti II, were observed by changing the pressure and RF conditions. An increase in emission line intensity from N II was observed by increasing the pressure and RF power. We used Ti II lines to estimate the plasma temperature by using the Boltzmann equation, and we obtained the density from the Ti II line (454.9 nm) through Stark broadening. In addition, a Mach-Zehnder interferometer was employed to make a twodimensional map of the electron density at early times. The estimated temperatures and densities are between 0.8-2.0 eV and 10 17-10 18 cm-3 , respectively. The results suggest that increasing RF power enhanced the TiN atoms interaction, which is crucial in titanium nitride film applications.
Bulletin of the American Physical Society, 2020
The use of a copper X-pinch as backlighting source for Talbot-Lau X-ray Deflectometry (TXD) is pr... more The use of a copper X-pinch as backlighting source for Talbot-Lau X-ray Deflectometry (TXD) is presented. The TXD technique can provide information about density gradients and elemental composition in HED plasmas, through single-image x-ray refraction and attenuation. In order to test the system in pulsed power environments, a TXD was implemented using a Cu X-pinch as X-ray source in the Llampüdkeñ generator (˜350kA in˜350ns). A minimum source size of˜50um was measured at the crossing point, with pulses of <2ns; as well as an extended x-ray source from the anode side of the array. Characteristic x-rays, as well as a broad continuum under 5keV were detected. A Be object is used as probing object, measuring its density with a difference <13%. No damage from debris or magnetic field was observed in the gratings used for TXD, but it is shown that a protective filter is required. These results are relevant in order to adapt and design further pulsed power experiments that aim to use the Talbot-Lau technique to characterize pulsed plasmas.
Bulletin of the American Physical Society, 2015
We have performed experimental studies of the effect of static axial magnetic fields on the plasm... more We have performed experimental studies of the effect of static axial magnetic fields on the plasma dynamics of laser produced carbon and titanium plasmas. The laser plasmas are produced in vacuum, with a Nd:YAG laser, 3.5 ns, 340 mJ at 1.06 4 µm, operating at 10 Hz, and propagate in static magnetic fields of maximum value ∼0.2 T. Laser plasma features are characterized using 50 ns time resolved plasma imaging, time and space resolved visible spectroscopy and Faraday cup measurements. The presence of the magnetic field is found to affect plasma dynamics, plasma emission and plasma ions energy spectrum. Based on these measurements, a detailed analysis of the confinement effects of the magnetic field on the laser plasma will be presented.
En este trabajo se presenta la comparacion entre simulaciones numericas de descargas en el dispos... more En este trabajo se presenta la comparacion entre simulaciones numericas de descargas en el dispositivo Plasma Focus llamado PF-50J utilizando el codigo CShock. El codigo fue capaz de reproducir las mediciones de la cinematica y de los parametros del circuito electrico asi como la inestabilidad particular que se produce en la lamina de corriente observada en este dispositivo en particular.
2018 IEEE International Conference on Plasma Science (ICOPS), 2018
A ring shape plasma can be produced by focusing a laser beam over a solid target, using a combina... more A ring shape plasma can be produced by focusing a laser beam over a solid target, using a combination of ax icon prism and convergent lens1. We present preliminary experimental studies of the dynamics of an annular plasma in background gases. The initial plasma is produced by focusing a Nd:YAG laser beam (1064 nm, 3.5 ns FWHM, −2cdot109-2\cdot 10^{9}−2cdot109 W / cm2) onto a flat target employing a combination of a 10 mrad axicon prism and a converging lens, which results in an initial ringlike shape plasma of 1 mm radius and sim150mumathrmn\sim 150\mu\mathrm{n}sim150mumathrmn thickness. Observations of the optical self-emission of Titanium plasmas at 80 mTorr Argon background indicate that the plasma propagates inwards in a time scale ~90 ns, which is then followed by on axis stagnation and formation of a jet-like column. The resulting plasma jet propagates axially forming a planar shock, with characteristic initial velocity sim2cdot106\sim 2\cdot 10^{6}sim2cdot106 cm/s. This planar shock transits to a bow-shock in characteristic timescales of ~600 ns. Further investigations employing two parallel coaxial NdFeB magnets, which produce a static magnetic field of ~0.1 T, suggest that confinement effects due to the magnetic field increases the transition time from planar to bow-shock to ~ 700 ns. Additional experiments have been conducted with Graphite and Titanium target in high pressure Argon and air backgrounds. By using schlieren laser imaging (532 nm, 3.5 ns FWHM) from Carbon and Titanium annular plasmas it is found that the characteristic on-axis stagnation times increase up to ~300 ns at 760 Torr. In a first approximation, both, the radial expansion of the annular plasma and the axial propagation of the resulting plasma jet can be described adequately by the drag model2. Based on these observations, a comprehensive description of the dynamics of laser produced annular plasmas, over a wide set of parameters, will be presented.
Physics of Plasmas, 2018
A series of experimental measurements of fast ions generated in a tungsten conical wire array are... more A series of experimental measurements of fast ions generated in a tungsten conical wire array are presented. The ions are detected using a set of negatively biased Faraday cups located on axis above the array at distances between 10 and 67 cm. Significant differences in the signals from the probes are found on varying the background atmospheric pressure between 10−2 and 10−5 Torr. At 10−5 Torr, a pulse of ions moving at 106 m/s is collected by the cups. In contrast, at intermediate (10−4 Torr) and high (10−2 Torr) pressures, both electrons and ions are detected with a velocity of order 106 m/s. The differences with pressure are ascribed to the ionization of the background gas by the tungsten ions. Time-of-flight measurements show the emission of fast ions during the ablation phase of wire array dynamics. Comparing the temporal behavior of the ions and their velocity of propagation with the dynamics observed using UltraViolet / eXtreme UltraViolet imaging allows us to conclude that t...
Journal of Physics: Conference Series, 2016
We present preliminary experimental observations of the collision processes between two orthogona... more We present preliminary experimental observations of the collision processes between two orthogonal laser produced plasmas in a low pressure neutral gas background. A Nd:YAG laser, 340 mJ, 3.5 ns, at 1.06 µm, operating at 10 Hz, is used in the experiments. The main laser beam is divided in two beams by a 50% beam splitter, and then focused over two rotating graphite targets, with characteristic fluence 3.5 J/cm 2. Experiments are conducted in a range from a base pressure of 0.3 mTorr, up to 50 mTorr argon. The dynamics of the laser plasmas is characterized by time resolved and time integrated optical emission spectroscopy (OES), with 20 ns and 10 ms time resolution, and 50 ns time resolved plasma imaging of visible plasma emission. Clear effects of the neutral gas background on the postcollision plasma dynamics are identified. The overall dynamics of the post-collision plasma is found to be consistent with high collisionality of the carbon plasma plumes, which results in full stagnation on collisioning.
IEEE Transactions on Plasma Science, 2012
Abstract Wire-array $ Z −pinchexperimentshavebeenperformedontheLlampu¨dkengenerator(-pinch experiments have been performed on the Llampüdkeñ generator (−pinchexperimentshavebeenperformedontheLlampu¨dkengenerator( si... more Abstract Wire-array $ Z −pinchexperimentshavebeenperformedontheLlampu¨dkengenerator(-pinch experiments have been performed on the Llampüdkeñ generator (−pinchexperimentshavebeenperformedontheLlampu¨dkengenerator( sim 470kAin470 kA in 470kAin sim $410 ns)[Chuaqui et al., Laser Part. Beams 15, 241 (1997)] using an overmassed load of aluminum wires. Time-resolved optical laser schlieren and extreme ultraviolet imaging were used in order to study the plasma ablation dynamics. The results show the formation and subsequent ablation of plasma from the wires, followed by the appearance of a precursor plasma column on the axis. According to these results ...
Journal of Physics: Conference Series, 2018
We present preliminary experimental observations of the plasma dynamics of laser produced annular... more We present preliminary experimental observations of the plasma dynamics of laser produced annular plasmas, expanding freely in a 80 mTorr Argon background. A Nd:YAG laser, 340 mJ, 3.5 ns, at 1.06 µm, operating at 10 Hz, is used in the experiments. To produce the annular plasma the laser pulse is focused on a titanium target using a combination of axicon and convergent lens. The dynamics of the laser plasma is characterized by 50 ns time resolved plasma imaging of the visible plasma emission. The inwards radial expansion of the initial plasma ring result in on-axis stagnation, giving rise to an expanding axial laser plasma plume. A quantitative description of the laser plasma dynamics is presented.
Physics Education
Water waves in the ocean can be easily observed at any place regardless of the distance from the ... more Water waves in the ocean can be easily observed at any place regardless of the distance from the shore. However, measurements of wave speeds with respect to the ground can be rather complicated due to the non-trivial oscillation water does. In this article, indirect measurements of the speed of shallow water waves are made after observations of shapes in the undertow water current over the beach sand. The measurements were taken using only a video recorded with a smartphone camera and no additional hardware. These particular shapes take the form of conical shock fronts (also known as Mach cones) which relate the speed of the undertow current with the water wave speed. Using this technique, a Mach number of M = 3.0 ± 0.2 and wave speeds of c wave = (19 ± 2) cm s−1 are obtained which agree with shallow wave speed equations.
Bulletin of the American Physical Society, 2016
Bulletin of the American Physical Society, 2015
Results in physics, 2020
A novel application for conical wire array Z-pinches to surface science is presented. The axial o... more A novel application for conical wire array Z-pinches to surface science is presented. The axial outflows emitted by a tungsten conical wire array in the form of both a dense plasma jet and energetic ions are used to produce morphological modification of substrate surfaces without using any kind of chemical treatment. In particular, surface modifications of (100) oriented Si substrates in the form of micropores and stripes-like formations after a single interaction of the Si to the axial outflows are obtained. It is found that the prevalence of each kind of formation, either micropores or stripes, on the treated substrate depends on the relative position of the target with respect to the wire array. The results indicate that at distances of 11cm over the array there is still effect of the dense plasma jet outflow since both micropores and stripes are found. On the contrary, solely stripe-like patterns are found at greater distances where the effect of the dense plasma outflow is mini...
, FONDECYT COLLABORATION , PLASMA TEAM-Dual radio frequency capacitively coupled plasma assisted ... more , FONDECYT COLLABORATION , PLASMA TEAM-Dual radio frequency capacitively coupled plasma assisted pulsed laser deposition (PA-PLD) have the advantage of preventing the microparticles reaching the substrate during thin film depositions. The plasma DC selfbias activates the substrate surface and destroy the large micro-particles reaching on it. The dual frequency offers the advantage of controlling the ion bombardment energy independently of the ion flux by tuning the low frequency (LF) power. We have compared transition metal nitride thin films such as the titanium nitride (TiN) and tungsten nitride (WN) in the hybrid configuration PAPLD. Optical emission spectroscopy was carried out during deposition. Standard surface science diagnostics like, x-ray diffraction, scanning electron microscopy, x-ray photoelectron spectroscopy and atomic force microscopy were used to characterize the deposited thin films. A comparative analysis of the thin films deposited by conventional PLD and PA-PLD, has shown that the PA-PLD technique improves the quality of the deposited films with respect to their stoichiometry, morphology and deposition rate.
Journal of Physics: Conference Series
The use of copper x-pinch plasmas as backlighting source for radiographing insects is described. ... more The use of copper x-pinch plasmas as backlighting source for radiographing insects is described. The experiments use 4x 25m Cu wires driven by a ~400kA, ~350ns current pulse to produce a localized source of soft x-rays in the micrometer range. Both source size and energy range of the x-rays photons produced by the x-pinch enable the imaging of low contrast objects such as the rich inner structures of insects with excellent spatial resolution. The technique is used in three different insects: a moth, a fly and a beetle. These radiographies allow clear observation of the details of outer (e.g., wings) and internal systems of the insects. A description of the method and ways to improve the quality of the radiographs are shown and discussed.