scholarly journals High-energy threshold reaction rates on 0.8 GeV proton-irradiated thick Pb-target

2007 ◽  
Author(s):  
Yu. E. Titarenko ◽  
V. F. Batyaev ◽  
A. Yu. Titarenko ◽  
M. A. Butko ◽  
K. V. Pavlov ◽  
...  
Keyword(s):  
Reaction Rates ◽  
High Energy ◽  
Energy Threshold ◽  
Threshold Reaction

Fuel Composition Effects on Forced Ignition of Liquid Fuel Sprays

2018 ◽  
Author(s):  
Sheng Wei ◽  
Brandon Sforzo ◽  
Jerry Seitzman
Keyword(s):  
Physical Properties ◽  
Liquid Fuel ◽  
Chemical Properties ◽  
Reaction Rates ◽  
High Energy ◽  
Fuel Spray ◽  
Successful Outcome ◽  
Fuel Composition ◽  
Ignition Probability ◽  
Fuel Sprays

In gas turbine combustors, ignition is achieved by using sparks from igniters to start a flame. The process of sparks interacting with fuel/air mixture and creating self-sustained flames is termed forced ignition. Physical and chemical properties of a liquid fuel can influence forced ignition. The physical effects manifest through processes such as droplet atomization, spray distribution, and vaporization rate. The chemical effects impact reaction rates and heat release. This study focuses on the effect of fuel composition on forced ignition of fuel sprays in a well-controlled flow with a commercial style igniter. A facility previously used to examine prevaporized, premixed liquid fuel-air mixtures is modified and employed to study forced ignition of liquid fuel sprays. In our experiments, a wall-mounted, high energy, recessed cavity discharge igniter operating at 15 Hz with average spark energy of 1.25 J is used to ignite liquid fuel spray produced by a pressure atomizer located in a uniform air coflow. The successful outcome of each ignition events is characterized by the (continued) presence of chemiluminescence 2 ms after spark discharge, as detected by a high-speed camera. The ignition probability is defined as the fraction of successful sparks at a fixed condition, with the number of events evaluated for each fuel typically in the range 600–1200. Ten fuels were tested, including standard distillate jet fuels (e.g., JP-8 and Jet-A), as well as many distillate and alternative fuel blends, technical grade n-dodecane, and surrogates composed of a small number of components. During the experiments, the air temperature is controlled at 27 C and the fuel temperature is controlled at 21 C. Experiments are conducted at a global equivalence ratio of 0.55. Results show that ignition probabilities correlate strongly to liquid fuel viscosity (presumably through droplet atomization) and vapor pressure (or recovery temperature), as smaller droplets of a more volatile fuel would lead to increased vaporization rates. This allows the kernel to transition to a self-sustained flame before entrainment reduces its temperature to a point where chemical rates are too slow. Chemical properties of the fuel showed little influence, except when the fuels had similar physical properties. This result demonstrates that physical properties of liquid fuels have dominating effects on forced ignition of liquid fuel spray in coflow air.

Contribution of High-Energy Particles to Thermonuclear Reaction Rates

Nature ◽  
1958 ◽  
Vol 182 (4643) ◽  
pp. 1140-1142 ◽  
Author(s):  
G. EDER ◽  
H. MOTZ
Keyword(s):  
Reaction Rates ◽  
High Energy ◽  
Thermonuclear Reaction ◽  
High Energy Particles

Hybrid simulation of instabilities in capacitively coupled RF CF4/Ar plasmas

2022 ◽  
Author(s):  
Wan Dong ◽  
Yi Fan Zhang ◽  
ZhongLing Dai ◽  
Julian Schulze ◽  
Yuan-Hong Song ◽  
...  
Keyword(s):  
Electric Field ◽  
Electron Temperature ◽  
Electron Impact ◽  
Electron Density ◽  
Etching Rate ◽  
Reaction Rates ◽  
High Energy ◽  
Density Fluctuations ◽  
Negative Ion ◽  
Capacitively Coupled

Abstract Radio frequency capacitively coupled plasmas (RF CCPs) sustained in fluorocarbon gases or their mixtures with argon are widely used in plasma-enhanced etching. In this work, we conduct studies on instabilities in a capacitive CF4/Ar (1:9) plasma driven at 13.56 MHz at a pressure of 150 mTorr, by using a one-dimensional fluid/Monte-Carlo (MC) hybrid model. Fluctuations are observed in densities and fluxes of charged particles, electric field, as well as electron impact reaction rates, especially in the bulk. As the gap distance between the electrodes increases from 2.8 cm to 3.8 cm, the fluctuation amplitudes become smaller gradually and the instability period gets longer, as the driving power density ranges from 250 to 300 W/m2. The instabilities are on a time scale of 16-20 RF periods, much shorter than those millisecond periodic instabilities observed experimentally owing to attachment/detachment in electronegative plasmas. At smaller electrode gap, a positive feedback to the instability generation is induced by the enhanced bulk electric field in the highly electronegative mode, by which the electron temperature keeps strongly oscillating. Electrons at high energy are mostly consumed by ionization rather than attachment process, making the electron density increase and overshoot to a much higher value. And then, the discharge becomes weakly electronegative and the bulk electric field becomes weak gradually, resulting in the continuous decrease of the electron density as the electron temperature keeps at a much lower mean value. Until the electron density attains its minimum value again, the instability cycle is formed. The ionization of Ar metastables and dissociative attachment of CF4 are noticed to play minor roles compared with the Ar ionization and excitation at this stage in this mixture discharge. The variations of electron outflow from and negative ion inflow to the discharge center need to be taken into account in the electron density fluctuations, apart from the corresponding electron impact reaction rates. We also notice more than 20% change of the Ar+ ion flux to the powered electrode and about 16% difference in the etching rate due to the instabilities in the case of 2.8 cm gap distance, which is worthy of more attention for improvement of etching technology.

Сomparison of ion pressure variations derived from Cluster/CODIF and the combined Cluster/CODIF&RAPID data during prolonged dipolarizations in the near Earth magnetotail

2020 ◽  
Author(s):  
Andrey Malykhin ◽  
Elena Grigorenko ◽  
Elena Kronberg ◽  
Patrick Daly
Keyword(s):  
Energy Range ◽  
Energy Flux ◽  
Total Pressure ◽  
High Energy ◽  
Plasma Pressure ◽  
Energy Threshold ◽  
Superposed Epoch Analysis ◽  
Flux Increase ◽  
Epoch Analysis ◽  
Thermal Part

<p>Usually, for the plasma pressure estimation in the plasma sheet  ion observations in the energy range up to ~40 keV are used. However, the thermal part of the distribution function can pass beyond the high energy threshold of an instrument during active events like dipolarizations. In such cases the entire ion population is not measured and the ion pressure can be underestimated. We study this problem by using Cluster mission observations provided  by two instruments: thermal plasma instrument - CODIF (up to 38 keV) and suprathermal instrument - RAPID (from 40 up to 1500 keV). We analyzed 11 dipolarization events and showed that in all events the maximum of ion energy flux was shifted to high energy threshold of CODIF instrument. Simultaneously, the energy flux increase in suprathermal energy range was observed by RAPID. For H<sup>+</sup> and O<sup>+</sup> ion components we calculate the pressure of suprathermal population and showed that the total pressure estimated by using both CODIF and RAPID instruments at some intervals exceeds the pressure estimated only from CODIF data up to 5 times. The superposed epoch analysis applied to 11 dipolarization events from our data base showed that the total pressure of H<sup>+</sup> and O<sup>+</sup> ion components can be in 2-5 times underestimated in the course of dipolarization.</p>

scholarly journals Quantemol Electron Collisions (QEC): An Enhanced Expert System for Performing Electron Molecule Collision Calculations Using the R-Matrix Method

Atoms ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 97 ◽  
Author(s):  
Bridgette Cooper ◽  
Maria Tudorovskaya ◽  
Sebastian Mohr ◽  
Aran O’Hare ◽  
Martin Hanicinec ◽  
...  
Keyword(s):  
Expert System ◽  
Cross Sections ◽  
Electron Attachment ◽  
Dissociative Recombination ◽  
Biological Tissues ◽  
Reaction Rates ◽  
High Energy ◽  
Electron Collision ◽  
Low Energy Electrons ◽  
Ionization Cross Sections

Collisions of low energy electrons with molecules are important for understanding many aspects of the environment and technologies. Understanding the processes that occur in these types of collisions can give insights into plasma etching processes, edge effects in fusion plasmas, radiation damage to biological tissues and more. A radical update of the previous expert system for computing observables relevant to these processes, Quantemol-N, is presented. The new Quantemol Electron Collision (QEC) expert system simplifyies the user experience, improving reliability and implements new features. The QEC graphical user interface (GUI) interfaces the Molpro quantum chemistry package for molecular target setups, and the sophisticated UKRmol+ codes to generate accurate and reliable cross-sections. These include elastic cross-sections, super elastic cross-sections between excited states, electron impact dissociation, scattering reaction rates, dissociative electron attachment, differential cross-sections, momentum transfer cross-sections, ionization cross sections, and high energy electron scattering cross-sections. With this new interface we will be implementing dissociative recombination estimations, vibrational excitations for neutrals and ions, and effective core potentials in the near future.

Experimental determination and computational modeling of threshold reaction rates in 0.8 GeV proton-irradiated lead target

Atomic Energy ◽  
2009 ◽  
Vol 107 (1) ◽  
pp. 48-59 ◽  
Author(s):  
Yu. E. Titarenko ◽  
V. F. Batyaev ◽  
A. Yu. Titarenko ◽  
V. M. Zhivun ◽  
K. V. Pavlov ◽  
...  
Keyword(s):  
Computational Modeling ◽  
Experimental Determination ◽  
Reaction Rates ◽  
Lead Target ◽  
Threshold Reaction

scholarly journals Interactions between Terrestrial Cosmic-Ray Neutrons and III–V Compound Semiconductors

2020 ◽  
Author(s):  
Daniela Munteanu ◽  
Jean-Luc Autran
Keyword(s):  
Bulk Material ◽  
Complementary Metal Oxide Semiconductor ◽  
Cosmic Ray ◽  
Compound Semiconductors ◽  
Reaction Rates ◽  
Binary Compound ◽  
High Energy ◽  
Oxide Semiconductor ◽  
Secondary Products ◽  
The Impact

This work explores by numerical simulation the impact of high-energy atmospheric neutrons and their interactions with III–V binary compound semiconductors. The efforts have focused on eight III–V semiconductors: GaAs, AlAs, InP, InAs, GaSb, InSb, GaN, and GaP. For each material, extensive Geant4 numerical simulations have been performed considering a bulk target exposed to a neutron source emulating the atmospheric neutron spectrum at terrestrial level. Results emphasize in detail the reaction rates per type of reaction (elastic, inelastic, nonelastic) and offer a classification of all the neutron-induced secondary products as a function of their atomic number, kinetic energy, initial stopping power, and range. Implications for single-event effects (SEEs) are analyzed and discussed, notably in terms of energy and charge deposited in the bulk material and in the first nanometers of particle range with respect to the critical charge for modern complementary metal oxide semiconductor (CMOS) technologies.

Non-Conventional Feedstock and Technologies for Biodiesel Production

2018 ◽  
pp. 96-118
Author(s):  
Edith Martinez-Guerra ◽  
Tapaswy Muppaneni ◽  
Veera Gnaneswar Gude ◽  
Shuguang Deng
Keyword(s):  
Alternative Fuels ◽  
Edible Oils ◽  
Reaction Rates ◽  
Waste Cooking Oil ◽  
High Energy ◽  
Biodiesel Production ◽  
Biodiesel Fuel ◽  
Transportation Fuels ◽  
Animal Fats ◽  
Security Issues

Increased consumption and energy security issues have led many developed and developing countries to seek methods to produce alternative fuels. Biodiesel is one such high-density alternative fuel that can increase the longevity of transportation fuels. Biodiesel can be produced from a wide range of feedstock using simple process schemes. In the past, edible oils were used as feedstock for biodiesel fuel production; however, use of non-traditional feed stock like waste cooking oil, non-edible oils, animal fats, and algae can make biodiesel production a sustainable process. The high free fatty acids content in the feedstock, longer reaction rates, high energy consumption, and the catalysts used in the conversion process pose some limitations for current biodiesel production. These limitations can be addressed by developing novel process techniques such as microwaves and ultrasound and by developing non-catalytic transesterification methods. Enhancing byproduct recovery seems to be an important strategy to improve the energy footprint and economics of current biodiesel production.

scholarly journals MetroMMC: Electron-Capture Spectrometry with Cryogenic Calorimeters for Science and Technology

2019 ◽  
Vol 199 (1-2) ◽  
pp. 441-450 ◽  
Author(s):  
P. C.-O. Ranitzsch ◽  
D. Arnold ◽  
J. Beyer ◽  
L. Bockhorn ◽  
J. J. Bonaparte ◽  
...  
Keyword(s):  
Electron Capture ◽  
Science And Technology ◽  
High Energy ◽  
Low Energy ◽  
Energy Threshold ◽  
High Energy Resolution ◽  
Wide Energy Range ◽  
Good Resolution ◽  
X Ray ◽  
Wide Range

AbstractAccurate decay data of radionuclides are necessary for many fields of science and technology, ranging from medicine and particle physics to metrology. However, data that are in use today are mostly based on measurements or theoretical calculation methods that are rather old. Recent measurements with cryogenic detectors and other methods show significant discrepancies to both older experimental data and theory in some cases. Moreover, the old results often suffer from large or underestimated uncertainties. This is in particular the case for electron-capture (EC) decays, where only a few selected radionuclides have ever been measured. To systematically address these shortcomings, the European metrology project MetroMMC aims at investigating six radionuclides decaying by EC. The nuclides are chosen to cover a wide range of atomic numbers Z, which results in a wide range of decay energies and includes different decay modes, such as pure EC or EC accompanied by $$\gamma $$γ- and/or $$\beta ^{+}$$β+-transitions. These will be measured using metallic magnetic calorimeters (MMCs), cryogenic energy-dispersive detectors with high-energy resolution, low-energy threshold and high, adjustable stopping power that are well suited for measurements of the total decay energy and X-ray spectrometry. Within the MetroMMC project, these detectors are used to obtain X-ray emission intensities of external sources as well as fractional EC probabilities of sources embedded in a $$4\pi $$4π absorber. Experimentally determined nuclear and atomic data will be compared to state-of-the-art theoretical calculations which will be further developed within the project. This contribution introduces the MetroMMC project and in particular its experimental approach. The challenges in EC spectrometry are to adapt the detectors and the source preparation to the different decay channels and the wide energy range involved, while keeping the good resolution and especially the low-energy threshold to measure the EC from outer shells.

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