On the simulation of gas ionization by fast electrons

The gas-dynamic parameters of an ionized medium formed during impact ionization of a rarefied gas by fast electrons are considered. The concentration, drift velocity, and specific energy of low-energy secondary electrons are constructed by an approximate solution of the kinetic equation. Approximations of the spatial homogeneity of the kinetic equation and the isotropy of the initial distribution of secondary electrons during impact ionization are used. Additional approximations are related to the structure of the distribution function of secondary electrons and averaging of the cross sections.

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Doubly differential cross sections for electron impact ionization of atomic hydrogen

Canadian Journal of Physics ◽

10.1139/p92-211 ◽

1992 ◽

Vol 70 (12) ◽

pp. 1309-1311 ◽

Cited By ~ 2

Author(s):

H. Ray ◽

A. C. Roy ◽

U. Werner

Keyword(s):

Electron Impact ◽

Cross Sections ◽

Differential Cross ◽

Atomic Hydrogen ◽

Impact Ionization ◽

Theoretical Calculations ◽

Electron Impact Ionization ◽

Differential Cross Sections ◽

Secondary Electrons ◽

Primary Electrons

The Glauber approximation is used to calculate doubly differential cross sections (DDC's) for electron impact ionization of atomic hydrogen at incident energies of 100, 150, and 250 eV. The angular dependences of DDC's are presented for the scattered (primary) electrons. The energies of ejected (secondary) electrons were chosen to be 5, 10, and 14 eV. A comparison is made of the present DDC's with the results of other theoretical calculations.

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Aerothermodynamic modelling of meteor entry flows

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3559 ◽

2019 ◽

Vol 492 (2) ◽

pp. 2308-2325 ◽

Cited By ~ 2

Author(s):

Federico Bariselli ◽

Aldo Frezzotti ◽

Annick Hubin ◽

Thierry E Magin

Keyword(s):

Cross Sections ◽

Impact Ionization ◽

Rarefied Gas ◽

Direct Simulation Monte Carlo ◽

Vapour Phase ◽

Molecular Flow ◽

Material Transport ◽

Dsmc Method ◽

Detailed Chemistry ◽

Ionization Coefficients

ABSTRACT Due to their small size and tremendous speeds, meteoroids often burn up at high altitudes above 80 km, where the atmosphere is rarefied. Ground radio stations allow us to detect the concentration of electrons in the meteoroid trail, which are produced by hyperthermal collisions of ablated species with the freestream. The interpretation of these data currently relies on phenomenological methods, derived under the assumption of free molecular flow, that poorly accounts for the detailed chemistry, diffusion in the vapour phase, and rarefied gas effects. In this work, we employ the direct simulation Monte Carlo (DSMC) method to analyse the detailed flowfield structure in the surroundings of a 1 mm meteoroid at different conditions, spanning a broad spectrum of Knudsen and Mach numbers, and we extract resulting ionization efficiencies. For this purpose, we couple the DSMC method with a kinetic boundary condition which models evaporation and condensation processes in a silicate material. Transport properties of the ablated vapour are computed following the Chapman–Enskog theory starting from Lennard–Jones potentials. Semi-empirical inelastic cross-sections for heavy- and electron-impact ionization of metals are computed analytically to obtain steric factors. The ionization of sodium is dominant in the production of free electrons, and hyperthermal air–vapour collisions play the most important role in this process. The ionization of air, classically disregarded, contributes to the electron production as significantly as ionization of magnesium and iron. Finally, we propose that DSMC could be employed as a numerical experiment providing ionization coefficients to be used in synthetic models.

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A Dynamical Study of Fusion Hindrance with Nakajima-Zwanzig Projection Method

Progress of Theoretical and Experimental Physics ◽

10.1093/ptep/ptab005 ◽

2021 ◽

Author(s):

Yasuhisa Abe ◽

David Boilley ◽

Quentin Hourdillé ◽

Caiwan Shen

Keyword(s):

Cross Sections ◽

Degrees Of Freedom ◽

Operator Method ◽

Initial Distribution ◽

Physical Parameters ◽

Relaxation Processes ◽

Fast Variable ◽

Dynamical Study ◽

Injection Point ◽

Slow Variables

Abstract A new framework is proposed for the study of collisions between very heavy ions which lead to the synthesis of Super-Heavy Elements (SHE), to address the fusion hindrance phenomenon. The dynamics of the reaction is studied in terms of collective degrees of freedom undergoing relaxation processes with different time scales. The Nakajima-Zwanzig projection operator method is employed to eliminate fast variable and derive a dynamical equation for the reduced system with only slow variables. There, the time evolution operator is renormalised and an inhomogeneous term appears, which represents a propagation of the given initial distribution. The term results in a slip to the initial values of the slow variables. We expect that gives a dynamical origin of the so-called “injection point s” introduced by Swiatecki et al in order to reproduce absolute values of measured cross sections for SHE. A formula for the slip is given in terms of physical parameters of the system, which confirms the results recently obtained with a Langevin equation, and permits us to compare various incident channels.

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Few Body Effects in the Electron and Positron Impact Ionization of Atoms

Atoms ◽

10.3390/atoms9020033 ◽

2021 ◽

Vol 9 (2) ◽

pp. 33

Author(s):

R.I. Campeanu ◽

Colm T. Whelan

Keyword(s):

Electron Impact ◽

Cross Sections ◽

Differential Cross ◽

Impact Ionization ◽

Inert Gas ◽

Interference Effects ◽

Positron Impact ◽

Competing Interactions ◽

Energy Sharing

Triple differential cross sections (TDCS) are presented for the electron and positron impact ionization of inert gas atoms in a range of energy sharing geometries where a number of significant few body effects compete to define the shape of the TDCS. Using both positrons and electrons as projectiles has opened up the possibility of performing complementary studies which could effectively isolate competing interactions that cannot be separately detected in an experiment with a single projectile. Results will be presented in kinematics where the electron impact ionization appears to be well understood and using the same kinematics positron cross sections will be presented. The kinematics are then varied in order to focus on the role of distortion, post collision interaction (pci), and interference effects.

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