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G. A. Mesyats - One of the best experts on this subject based on the ideXlab platform.
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Parameters of a runaway Electron Avalanche
Physics of Plasmas, 2017Co-Authors: E. V. Oreshkin, S. A. Barengolts, V. I. Oreshkin, G. A. MesyatsAbstract:The features of runaway Electron Avalanches developing in air at different pressures are investigated using a three-dimensional numerical simulation. The simulation results indicate that an Avalanche of this type can be characterized, besides the time and length of its exponential growth, by the propagation velocity and by the average kinetic energy of the runaway Electrons. It is shown that these parameters obey the similarity laws applied to gas discharges.
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ecton or Electron Avalanche from metal
Physics-Uspekhi, 1995Co-Authors: G. A. MesyatsAbstract:The so-called explosive Electron emission observed as individual packets or Avalanches of Electrons is shown to occur in microexplosions at the cathode. This microexplosion of Electrons is called an ecton. Electron current in an ecton starts to flow as a result of the overheating of metal because of the high energy density (104 J g−1), and the current stops owing to the cooling of the emission zone. Ectons occur in electrical discharges in vacuum, in cathode spots of a vacuum arc, in bulk discharges in gases, in pseudo-spark discharges, in corona discharges, etc.
Daniel Palanker - One of the best experts on this subject based on the ideXlab platform.
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Anterior capsulotomy with a pulsed-Electron Avalanche knife.
Journal of cataract and refractive surgery, 2010Co-Authors: Daniel Palanker, Alexander Vankov, Philip Huie, Hiroyuki Nomoto, David F. ChangAbstract:Purpose To evaluate a new pulsed-Electron Avalanche knife design for creating a continuous curvilinear capsulotomy (CCC) and compare the CCC with a mechanical capsulorhexis. Setting Department of Ophthalmology, Stanford University, Stanford, California, USA. Methods In this study, CCCs were created in freshly enucleated bovine eyes and in rabbit eyes in vivo. The cutting velocity was adjusted by controlling the burst repetition rate, voltage amplitude, and burst duration. Tissue samples were fixed and processed for histology and scanning Electron microscopy (SEM) immediately after surgery. Results The study included 50 bovine eyes and 10 rabbit eyes. By adjusting the electrosurgical waveforms, gas-bubble formation was minimized to permit good surgical visualization. The optimum voltage level was determined to be ±410 V with a burst duration of 20 μs. Burst repetition rate, continuously adjustable from 20 to 200 Hz with footpedal control, allowed the surgeon to vary linear cutting velocity up to 2.0 mm/s. Histology and SEM showed that the pulsed-Electron Avalanche knife produced sharp-edged capsule cutting without radial nicks or tears. Conclusions The probe of the pulsed-Electron Avalanche knife duplicated the surgical feel of a 25-gauge cystotome and created a histologically smooth capsule cut. It may improve precision and reproducibility of creating a CCC, as well as improve its proper sizing and centration, especially in the face of surgical risk factors, such as weak zonules or poor visibility. Financial Disclosures Drs. Palanker and Vankov hold patents to the pulsed Electron Avalanche knife technology, which are licensed to PEAK Surgical by Stanford University. Drs. Palanker and Chang are consultants to PEAK Surgical. Dr. Vankov is an employee of PEAK Surgical. Neither of the other authors has a financial or proprietary interest in any material or method mentioned.
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pulsed Electron Avalanche knife new technology for cataract surgery
British Journal of Ophthalmology, 2007Co-Authors: Siegfried G. Priglinger, Christos Haritoglou, Martin Grueterich, Claudia S. Alge, Daniel Palanker, Thomas C Kreutzer, Anselm KampikAbstract:Background: The pulsed Electron Avalanche knife (PEAK-fc) is a new pulsed electrosurgical device that allows for precise, “cold” and traction-free tissue dissection. Aim: To evaluate the surgical applicability, safety and potential complications of PEAK-fc in complicated cataract surgery. Methods: The study included five children with congenital cataracts, two patients with advanced senile cataracts, six adults with mature cataracts, three of them with posterior iris synechia, three patients with post-traumatic cataracts with zonulolysis, one patient with intumescent traumatic cataract and three patients with massive anterior capsule opacification. Anterior and posterior capsulotomies, iris synechiolysis, dissection of anterior capsule opacification and fibrotic scar tissue were performed. PEAK-fc was set at voltages of 500–700 V, pulse duration of 0.1 m and repetition rate of 40–100 Hz. Results: Anterior and posterior capsulotomies were successfully and safely performed in all eyes. The edges of capsulotomies appeared sharp, showing only limited collateral damage. PEAK-fc worked best by just gently touching the capsule, thereby avoiding tractional forces or pressure on the lens capsule. Posterior iris synechiae could be released and anterior capsule opacification was dissected without complications. Conclusions: PEAK-fc is a very helpful cutting device for complicated cases of cataract surgery, especially for mature and congenital cataracts, traumatic zonulolysis or anterior segment complications after intraocular inflammation.
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Gene transfer to rabbit retina with Electron Avalanche transfection.
Investigative ophthalmology & visual science, 2006Co-Authors: Thomas W. Chalberg, Alexander Vankov, F.e. Molnar, A. Butterwick, Philip Huie, Michele P. Calos, Daniel PalankerAbstract:PURPOSE. Nonviral gene therapy represents a promising treatment for retinal diseases, given clinically acceptable methods for efficient gene transfer. Electroporation is widely used for transfection, but causes significant collateral damage and a high rate of cell death, especially in applications in situ. This study was conducted in the interest of developing efficient and less toxic forms of gene transfer for the eye. METHODS. A novel method for nonviral DNA transfer, called Electron Avalanche transfection, was used that involves microsecond electric plasma-mediated discharges applied via microelectrode array. This transfection method, which produces synchronized pulses of mechanical stress and high electric field, was first applied to chorioallantoic membrane as a model system and then to rabbit RPE in vivo. Gene transfer was measured by using luciferase bioluminescence and in vivo fluorescent fundus photography. Safety was evaluated by performing electroretinograms and histology. RESULTS. In chorioallantoic membrane, Electron Avalanche transfection was 10,000-fold more efficient and produced less tissue damage than conventional electroporation. Also demonstrated was efficient plasmid DNA transfer to the rabbit retina after subretinal DNA injection and transscleral Electron Avalanche transfection. Electroretinograms and histology showed no evidence of damage from the procedure. CONCLUSIONS. Electron Avalanche transfection is a powerful new technology for safe DNA delivery that has great promise as a nonviral system of gene transfer. (Invest Ophthalmol Vis Sci. 2006;47:4083‐4090) DOI:10.1167/iovs.06-0092
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Pulsed Electron Avalanche knife for capsulotomy in congenital and mature cataract
Journal of cataract and refractive surgery, 2006Co-Authors: Siegfried G. Priglinger, Christos Haritoglou, Arthur J. Mueller, Martin Grueterich, Claudia S. Alge, Daniel Palanker, Daniel Kook, Anselm KampikAbstract:The pulsed Electron Avalanche knife (PEAK-fc, Carl Zeiss Meditec) is an electrosurgical cutting device that allows precise "cold" and traction-free tissue dissection. We describe its applicability and safety for anterior capsulotomy in a child with congenital cataract and an adult patient with mature cataract. The PEAK-fc was set at a voltage of 600 V and a pulse repetition rate of 80 Hz. Anterior capsulotomies were successfully and safely performed in both cases, with the edges of capsulotomies appearing sharp and showing only limited collateral damage. The PEAK-fc appears to be a helpful cutting device for complicated cases of cataract surgery, especially for mature and congenital cataracts.
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pulsed Electron Avalanche knife peak fc for dissection of retinal tissue
Archives of Ophthalmology, 2005Co-Authors: Siegfried G. Priglinger, Christos Haritoglou, Claudia S. Alge, Arnd Gandorfer, Daniel Palanker, Anselm KampikAbstract:Objective To evaluate the effectiveness and precision of tractionless retinal tissue dissection by the advanced version of the pulsed Electron Avalanche knife for fine cutting (PEAK-fc; Carl Zeiss Meditec, Jena, Germany). Methods Porcine retina (in vivo) and human retina (in vitro) were incised with the PEAK-fc using various pulse parameters. The globes were then processed for light microscopy. Evaluation of all specimens focused on depth of the retinal cuts and on the degree of collateral damage. Results Retinal cuts performed both in vivo on porcine eyes and on human donor eyes showed very sharp edges with only little collateral damage. With probes of 600 μm in length, the optimal pulse parameters for precise and reproducible cutting of the retina were an amplitude of 350 to 380 V, a repetition rate of 300 Hz, and 30 “minipulses” per pulse of 100-microsecond duration. With increasing voltage, cuts also affected the retinal pigment epithelium and the choroid, followed by intravitreal bleeding during in vivo application. Conclusion We demonstrated that PEAK-fc is capable of precisely cutting retinal tissue in vivo and in vitro using optimal pulse parameters. Further in vivo studies will be necessary to determine the efficacy of this new tractionless cutting device in vitreoretinal surgery.
William H. Beasley - One of the best experts on this subject based on the ideXlab platform.
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Radio frequency emissions from a runaway Electron Avalanche model compared with intense, transient signals from thunderstorms
Journal of Geophysical Research D: Atmospheres, 2005Co-Authors: Heidi E. Tierney, Robert A. Roussel-dupré, E. M. D. Symbalisty, William H. BeasleyAbstract:We present a one-dimensional model of a runaway Electron Avalanche in a thunderstorm electric field. Previous simulations have calculated the ionization rates and energy distribution functions for runaway Electrons, for various atmospheric values of E/p, through the solution of the modified relativistic Boltzmann equation. We use the field- and pressure-dependent ionization rates in a hydrodynamic macroscopic treatment. The runaway Electron Avalanche modeled here includes the production of runaway and low-energy Electrons, electric field relaxation, Electron attachment, and runaway Electron loss. The model ambient electric field is established from two disks of charge with a sinusoidally spatially varying charge density of 9 nC/m3 peak amplitude. The peak ambient electric field from this configuration is 538 kV/m at 5 km. The numerically calculated radio frequency radiation exhibits relativistic effects. We hypothesize that runaway Electron Avalanches are sources of intense HF/VHF impulses radiated from within electrified clouds. The results from this case study are compared with ground-based and FORTE satellite observations of HF and VHF radiation observed during the rise portion of narrow bipolar pulses (NBP). Given the specified rates and ambient environment, the radiation electric field HF and VHF spectra covering 3–25, 26–48, and 60–66 MHz are in agreement with observations for limited angular ranges. The modeled peak radiation electric field in the time domain is just below one standard deviation from the observed mean for NBPs.
Heidi E. Tierney - One of the best experts on this subject based on the ideXlab platform.
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Radio frequency emissions from a runaway Electron Avalanche model compared with intense, transient signals from thunderstorms
Journal of Geophysical Research D: Atmospheres, 2005Co-Authors: Heidi E. Tierney, Robert A. Roussel-dupré, E. M. D. Symbalisty, William H. BeasleyAbstract:We present a one-dimensional model of a runaway Electron Avalanche in a thunderstorm electric field. Previous simulations have calculated the ionization rates and energy distribution functions for runaway Electrons, for various atmospheric values of E/p, through the solution of the modified relativistic Boltzmann equation. We use the field- and pressure-dependent ionization rates in a hydrodynamic macroscopic treatment. The runaway Electron Avalanche modeled here includes the production of runaway and low-energy Electrons, electric field relaxation, Electron attachment, and runaway Electron loss. The model ambient electric field is established from two disks of charge with a sinusoidally spatially varying charge density of 9 nC/m3 peak amplitude. The peak ambient electric field from this configuration is 538 kV/m at 5 km. The numerically calculated radio frequency radiation exhibits relativistic effects. We hypothesize that runaway Electron Avalanches are sources of intense HF/VHF impulses radiated from within electrified clouds. The results from this case study are compared with ground-based and FORTE satellite observations of HF and VHF radiation observed during the rise portion of narrow bipolar pulses (NBP). Given the specified rates and ambient environment, the radiation electric field HF and VHF spectra covering 3–25, 26–48, and 60–66 MHz are in agreement with observations for limited angular ranges. The modeled peak radiation electric field in the time domain is just below one standard deviation from the observed mean for NBPs.
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Radio-frequency emissions from runaway Electron Avalanche models compared with intense, transient radio-frequency signals associated with thunderstorms.
2002Co-Authors: Heidi E. TierneyAbstract:The results of a one-dimensional model of a runaway Electron Avalanche, initiated by a high-energy cosmic ray secondary Electron, in a thunderstorm electric field are presented. The time-evolution of the Electron densities, characterized by mean energies of 7.2 MeV and 1-2 eV, and the associated radiation electric fields are reported. The dominant rates that control the evolution of the Electron Avalanche in the troposphere and in an external electric field are: Avalanche ionization, low-energy Electron attachment, and high-energy Electron loss. The self-consistent evolution of the electric field is included. Relativistic effects are salient features of the numerically calculated radio-frequency radiation. The peak radiation electric fields and VHF spectra are in agreement with observations of a class of lightning waveforms known as narrow bipolar pulses (NBPs). It is hypothesized that the runaway Electron Avalanche is responsible for the rise time, and associated VHF impulses, of the NBP signals. Further work is needed to explain other aspects of the observations.
Avrilios Lazaros - One of the best experts on this subject based on the ideXlab platform.
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New experimental evidence for the stabilizing effect of a superthermal Electron Avalanche during Electron cyclotron resonant heating
Physics of Plasmas, 2002Co-Authors: Avrilios Lazaros, Akihiro Shimizu, Yasuo Yoshimura, Keisuke Matsuoka, Shoichi Okamura, Chihiro SuzukiAbstract:New experimental evidence for the stabilizing effect of the superthermal Electrons [A. Lazaros, Phys. Plasmas 6, 148 (1999)], which are produced through the Avalanche effect [A. Lazaros, Phys. Plasmas 8, 1263 (2001)] during Electron cyclotron resonant heating (ECRH), is provided by the suppression of the “fishbone” mode with ECRH in the “compact helical system” [S. Okamura et al., Nucl. Fusion 39, 1337 (1999)], in an experimental arrangement which favors the development of a superthermal Electron Avalanche and excludes any other stabilizing effect. The significance of the radial location of the EC resonance and the Electron density, for the development of the superthermal Electron Avalanche, is confirmed by radial scans of the EC resonance and by density scans.
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Development of a superthermal Electron Avalanche and tearing mode suppression during Electron cyclotron resonant heating
Physics of Plasmas, 2001Co-Authors: Avrilios LazarosAbstract:The critical velocity, for Electron acceleration up to the superthermal region, is expressed in terms of the heating power per particle, instead of the inductively applied electric field. This expression is used to evaluate the superthermal Electron production rate in a superthermal Electron Avalanche during Electron cyclotron resonant heating (ECRH). The comparison between the predicted growth time of the superthermal Electron Avalanche and the experimental decay time of tearing modes provides an additional confirmation of the recent theory for the suppression of magnetohydrodynamic modes by superthermal Electrons during ECRH.