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Pedreros J.,University of Santiago de Chile | Pavez C.,Comision Chilena de Energia Nuclear | Pavez C.,Center for Research and Applications in Plasma Physics and Pulsed Power P4 | Pavez C.,Andrés Bello University | And 8 more authors.
2016 IEEE International Conference on Automatica, ICA-ACCA 2016 | Year: 2016

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. © 2016 IEEE.


Veloso F.,Comision Chilena de Energia Nuclear | Veloso F.,Center for Research and Applications in Plasma Physics and Pulsed Power P4 | Pavez C.,Comision Chilena de Energia Nuclear | Pavez C.,Center for Research and Applications in Plasma Physics and Pulsed Power P4 | And 9 more authors.
Journal of Fusion Energy | Year: 2012

Dynamical discharge characteristics and their relation with the total neutron yield emitted from a 400 J plasma focus operating in deuterium gas are presented. The dynamical nature of the plasma focus is obtained merely from the analysis of the voltage and current electrical signals without considering any particular geometry for the plasma sheath. It is calculated that large neutron yields are obtained when plasma inductance, mechanical energy and plasma voltage at pinching time have larger values. In contrast, no correlations are found among neutron yields either with plasma propagation velocities or quantities at the beginning of the radial phase. There is also found that the current sheath geometry changes according to the gas pressure, having larger curvature for lower pressures. The calculations also provide estimations of sheath thicknesses at the detachment from the insulator in the range of 0.5-1 mm, being thicker for larger neutron yield. © Springer Science+Business Media, LLC 2011.


Veloso F.,Comision Chilena de Energia Nuclear | Veloso F.,Center for Research and Applications in Plasma Physics and Pulsed Power P4 | Veloso F.,Andrés Bello University | Veloso F.,University of Santiago de Chile | And 16 more authors.
Plasma Physics and Controlled Fusion | Year: 2012

The kinematics of the plasma sheath in two very low energy plasma focus devices (70 and 300J) is studied by means of non-perturbative optical diagnostics. Experiments are performed in deuterium at the filling pressure where neutron emission is maximum on each generator. In both devices, the sheath movement is monitored close to the anode surface, from where their thicknesses and their average propagation velocities are obtained. It is found that the sheath thicknesses are closer to or lower than 1mm, which is significantly smaller than those measured in larger devices. Moreover, it is found that the sheaths remain attached for a period of time close to 20-30% of the quarter period of the discharge, and it coincides with estimations using theoretical models of sheath formation. These results suggest that the usual modeling tools used in plasma focus need further revision given that some discarded parameters such as plasma resistance and detachment time are important in very low energy devices, which is not necessarily true for high-energy devices. Some calculations and comparison with models are presented and discussed. © 2012 IOP Publishing Ltd.


Pavez C.,Comision Chilena de Energia Nuclear | Pavez C.,Center for Research and Applications in Plasma Physics and Pulsed Power P4 | Pavez C.,Andrés Bello University | Pedreros J.,University of Santiago de Chile | And 16 more authors.
Plasma Physics and Controlled Fusion | Year: 2012

Currently, a new generation of small plasma foci devices is being developed and researched, motivated by its potential use as portable sources of x-ray and neutron pulsed radiation for several applications. In this work, experimental results of the accumulated x-ray dose angular distribution and characterization of the x-ray source size are presented for a small and fast plasma focus device, PF-400J (880nF, 40nH, 27-29kV, 350J, T/4300ns). The experimental device is operated using hydrogen as the filling gas in a discharge region limited by a volume of around 80cm3. The x-ray radiation is monitored, shot by shot, using a scintillator-photomultiplier system located outside the vacuum chamber at 2.3m far away from the radiation emission region. The angular x-ray dose distribution measurement shows a well-defined emission cone, with an expansion angle of 5°, which is observed around the plasma focus device symmetry axis using TLD-100 crystals. The x-ray source size measurements are obtained using two image-forming aperture techniques: for both cases, one small (pinhole) and one large for the penumbral imaging. These results are in agreement with the drilling made by the energetic electron beam coming from the pinch region. Additionally, some examples of image radiographic applications are shown in order to highlight the real possibilities of the plasma focus device as a portable x-ray source. In the light of the obtained results and the scaling laws observed in plasma foci devices, we present a discussion on the potentiality and advantages of these devices as pulsed and safe sources of x-radiation for applications. © 2012 IOP Publishing Ltd.


Zambra M.,Comision Chilena de Energia Nuclear | Zambra M.,Center for Research and Applications in Plasma Physics and Pulsed Power P4 | Zambra M.,Diego Portales University | Pavez C.,Comision Chilena de Energia Nuclear | And 5 more authors.
39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics | Year: 2012

A. Da Re et al. [1] shown one of the first preliminary studies on X-rays coming from an experimental Plasma Focus (PF) device. Using radiographic films to obtain images of different thick plexiglass filters it was possible to diagnose some aspects of the X-rays emitted by PF source of nanosecond exposition times. Beside of the scientific interest in the X-ray PF characterization, some efforts have been made to improve this emissions as a useful X-ray application technique [2] including moving objects at high rpm [3]; despite a very nice radiographies experimentally obtained, a good quality PF X-ray images must be improved when they are contrast with radiographies obtained by means conventional techniques.


Pavez C.,Comision Chilena de Energia Nuclear | Pavez C.,Center for Research and Applications in Plasma Physics and Pulsed Power P4 | Pavez C.,Andrés Bello University | Pedreros J.,University of Santiago de Chile | And 6 more authors.
IEEE Transactions on Plasma Science | Year: 2012

The work presented in this paper proposes a simple interferometric technique of recording and digital processing, which allows the obtaining of three possible interferometric records of variations at the refraction index, both in large scale and in small scale. The experimental setup basically consists of the Mach-Zehnder interferometer and a digital camera (with CMOS technology) coupled to a PC. The interferometric arrangement originally forms a pattern of very thin parallel fringes (15-20 lines/mm on the CMOS device), which could eventually be used to obtain information of the refractivity of the phase object to submillimeter scales, looking directly to the original interferogram. The digital interferometric technique shown here is for triple exposure: the first exposure contains the plasma information and the next two are only referential records (reference interferometric patterns), similar to optical holographic interferometry, but instead of each exposure occurring on the same holographic plate, the record is done in consecutive captures of a digital acquisition system. One of the referential records is captured in the same condition as the one with plasma and the other one slightly changing the incidence angle of the reference beam. Thus, with this digital interferometry technique, it is possible to obtain (for the same plasma) a microinterferogram, which is an interferogram in fringes of infinite width and an interferogram in fringes of finite width. The technique is depicted in three different cases, namely, synthetic interferograms of a Gaussian plasma profile (simulated), laser-produced plasma, and a Z-pinch discharge at the SPEED2 generator. The first case describes the actual scope of the technique. For the other two pulsed plasmas, an Nd-YAG power laser (at the second harmonic, 532 nm) is used to produce the fringe pattern. © 2012 IEEE.


Veloso F.,Comision Chilena de Energia Nuclear | Veloso F.,Center for Research and Applications in Plasma Physics and Pulsed Power P4 | Veloso F.,Andrés Bello University | Veloso F.,University of Santiago de Chile | And 16 more authors.
Measurement Science and Technology | Year: 2012

The description and use of a non-perturbative optical diagnostic technique for measuring sheath movement in plasma focus are presented. The method is based on a lens that collects the light emitted by the plasma sheath which is detected by fast photodiodes. Two different circuit connections for the photodiodes are presented using either several or a single scope channels to record the photodiode signals. The technique is applied to a 300 J plasma focus with a spatial resolution of ∼0.25mm measuring its average propagation speeds (axial and radial) as well as its detachment time and an estimated thickness. The setup required in this technique is easy to implement and cost-effective, and it can be applied in any plasma focus, regardless of its stored energy or operational gas. © 2012 IOP Publishing Ltd.


Pavez C.,Center for Research and Applications in Plasma Physics and Pulsed Power P4 | Soto L.,Center for Research and Applications in Plasma Physics and Pulsed Power P4 | Soto L.,University of Talca | Soto L.,University of Concepción
IEEE Transactions on Plasma Science | Year: 2010

Recently, it has been demonstrated that it is possible to produce a pinch focus discharge with a device operating at only 0.1 J, i.e., nanofocus (NF). Evidence of pinch has been obtained from electrical signals and from images in the visible region of the plasma dynamics registered with a single-frame image-converter camera with few nanoseconds of exposure time. Here, the evidence of X-ray emission from the NF device is presented (NF: 5 nF, 510 kV, 510 kA, 60250 mJ, and 16-ns time to peak current). The experiments were performed using submillimetric anode radii. Evidence of X-ray emission from this ultraminiature pinch plasma focus device that operates at only 0.1 J/shot is shown for discharges in H2, Ar, and Ne. © 2010 IEEE.

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