scholarly journals Collision of a Positron with the Capture of an Electron from Lithium and the Effect of a Magnetic Field on the Particles Balance

Chemosensors ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 45
Author(s):  
Elena V. Orlenko ◽  
Alexandr V. Evstafev ◽  
Fedor E. Orlenko
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
Cross Section ◽  
Dynamic Equilibrium ◽  
Mass Effect ◽  
Alpha Particles ◽  
Exchange Effects ◽  
The Cross ◽  
Living Tissues ◽  
Comparison Of The Results

The processes of scattering slow positrons with the possible formation of positronium play an important role in the diagnosis of both composite materials, including semiconductor materials, and for the analysis of images obtained by positron tomography of living tissues. In this paper, we consider the processes of scattering positrons with the capture of an electron and the formation of positronium. When calculating the cross-section for the capture reaction, exchange effects caused by the rearrangement of electrons between colliding particles are taken into account. Comparison of the results of calculating the cross-section with a similar problem of electron capture by a proton showed that the mass effect is important in such a collision process. The loss of an electron by a lithium atom is more effective when it collides with a positron than with a proton or alpha particles. The dynamic equilibrium of the formation of positronium in the presence of a strong magnetic field is considered. It is shown that a strong magnetic field during tomography investigation shifts the dynamic equilibrium to the positronium concentration followed by positron annihilation with radiation of three gamma-quants.

scholarly journals Production Cross Sections of Axion in a Static Electromagnetic Field

2013 ◽  
Vol 23 (1) ◽  
pp. 21
Author(s):  
Dang Van Soa ◽  
Tran Dinh Tham
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Field ◽  
Electric Field ◽  
Total Cross Section ◽  
Strong Magnetic Field ◽  
Cross Section ◽  
Cross Sections ◽  
Feynman Diagram ◽  
Production Cross ◽  
The Cross

Photon - axion conversions in staticelectromagnetic fields of the size \(a\times b \times c\) areconsidered in detail by the Feynman diagram methods. Thedifferential cross sections are presented and the numericalevaluations of the total cross section are given. Our result showsthat the conversion cross-sections in the electric field are quitesmall, while in the strong magnetic field, the cross-sections are much enhanced, which can be measurable in current experiments.

Experiments on the reaction T( d , n ) 4 He I. The 90° cross-section

1951 ◽  
Vol 204 (1079) ◽  
pp. 488-499 ◽  
Keyword(s):  
Cross Section ◽  
Heavy Water ◽  
Incident Beam ◽  
Absolute Magnitude ◽  
Alpha Particles ◽  
Low Energy ◽  
Energy Relation ◽  
Conventional Theory ◽  
Simultaneous Observation ◽  
The Cross

The 90° cross-section of the reaction 3 1 H( d , n ) 4 2 He has been investigated over the energy range 100 to 200 keV (energy of bombarding triton) using the 200 keV accelerating set of the establishment. Two methods have been used. As a preliminary experiment the yield of alpha-particles from a thick heavy-ice target was measured per unit charge of incident beam, as a function of deuteron energy, and the variation of cross-section deduced from the gradient of this excitation curve and the range energy relation for tritons in heavy water. Secondly, a comparison was made between the yield of alpha-particles from the D-T reaction and the yield of protons from the D-D reaction when a beam containing both deuterons and tritons was passed through a heavy-water vapour target. (The energy loss in this target was calculated as only a few hundred electron volts.) To do this a simultaneous observation was made of the protons and alpha-particles using the same counter. The values obtained for the cross-section have been compared with the resonance formulae given by Bretscher & French (1949) and by Tascbek, Everhart, Gittings, Hemmendinger & Jarvis (1948) and have been found to be in disagreement with formulae of this type. From considerations of the absolute magnitude of the cross-section it has been deduced that no conventional theory postulating reaction at a distance equal to the sum of the nuclear radii (cf. Konopinski & Teller 1948) will be able to explain this reaction. The evidence for a low-energy resonance (Allan & Poole 1949) is thought to be inconclusive.

Quantum Theory of Stokes Parameters for Thomson Scattering in a Magnetised Plasma

1991 ◽  
Vol 9 (2) ◽  
pp. 325-325
Author(s):  
Chih-Kang Chou ◽  
Hui-Hwa Chen
Keyword(s):  
Magnetic Field ◽  
Angular Distribution ◽  
Quantum Theory ◽  
Free Path ◽  
Strong Magnetic Field ◽  
Cross Section ◽  
Mean Free Path ◽  
Thomson Scattering ◽  
Stokes Parameters ◽  
Scattering Process

Extended abstractThomson scattering in pulsar magnetospheres has previously been studied by several authors. The most distinguishing feature is the fact that the super-strong magnetic field (B ~ 1012 G) greatly affects the Thomson scattering process, resulting in resonances in the scattering cross-section (Canuto et al. 1971; Herold 1979; Chou 1986; Daugherty and Harding 1986). The important consequences of these cyclotron resonances are the increase in the photon mean free path in the scattering regions, and strongly affecting the angular distribution, and polarisation properties of the scattered photons (Chou 1986; Chou et al. 1989).

Magnetic-field dependence of the cross section formJmixing in2P1/2Cs and Rb atoms

1994 ◽  
Vol 49 (6) ◽  
pp. 4540-4548 ◽  
Author(s):  
W. Kedzierski ◽  
Ju Gao ◽  
W. E. Baylis ◽  
L. Krause
Keyword(s):  
Magnetic Field ◽  
Cross Section ◽  
Field Dependence ◽  
Magnetic Field Dependence ◽  
The Cross

scholarly journals Compton scatteringSmatrix and cross section in strong magnetic field

2016 ◽  
Vol 93 (10) ◽  
Author(s):  
Alexander A. Mushtukov ◽  
Dmitrij I. Nagirner ◽  
Juri Poutanen
Keyword(s):  
Magnetic Field ◽  
Strong Magnetic Field ◽  
Cross Section

scholarly journals Rotating magnetic field effect on convection and its stability in a horizontal cylinder subjected to a longitudinal temperature gradient

2010 ◽  
Vol 664 ◽  
pp. 108-137 ◽  
Author(s):  
D. V. LYUBIMOV ◽  
A. V. BURNYSHEVA ◽  
H. BENHADID ◽  
T. P. LYUBIMOVA ◽  
D. HENRY
Keyword(s):  
Magnetic Field ◽  
Temperature Gradient ◽  
Prandtl Number ◽  
Cross Section ◽  
Rotating Magnetic Field ◽  
Shear Mode ◽  
Convective Flows ◽  
Longitudinal Temperature Gradient ◽  
Longitudinal Temperature ◽  
The Cross

A rotating magnetic field (RMF) is used in crystal growth applications during the solidification process in order to improve the crystal quality. Its influence on the convective flows in molten metals and on their stability is studied here in the case of a horizontal infinite cylindrical channel subjected to a longitudinal temperature gradient. The steady convective flows, which correspond to the usual longitudinal counterflow structure, with four vortices in the cross-section for non-zero Prandtl number, Pr, are modified by the RMF (parametrized by the magnetic Taylor number Tam). For zero Prandtl number, the flow in the cross-section corresponds to circular streamlines and the longitudinal flow structure is moved in the direction of the magnetic field rotation, with a decrease in its intensity and an asymptotic variation as 1/Tam. For non-zero Prandtl numbers, depending on the respective values of Tam on one side and Prandtl and Grashof numbers on the other side, different structures ranging from the circular streamlines with transport by rotation of the longitudinal velocity and the temperature field, to the more usual counterflow structure almost insensitive to the RMF with four cross-section vortices, can be obtained. The decrease in the flow intensity with increasing Tam is also delayed for non-zero Pr, but the same asymptotic limit is eventually reached. The stability analysis of these convective flows for Tam = 0 shows a steep increase of the thresholds around Pr = Prt,0 ≈ 3 × 10−4, corresponding to the transition between the usual counterflow shear mode and a new sidewall shear mode. This transition is still present with an RMF, but it occurs for smaller Pr values as Tam is increased. Strong stabilizing effects of the rotating magnetic field are found for Pr < Prt,0, particularly for Pr = 0 where an exponential increase of the threshold with Tam is found. For Pr > Prt,0 (i.e. in the domain where the sidewall instability is dominant), in contrast, the stabilization by the RMF is weak.

scholarly journals Radial distribution of electrons rotation moment in hall effect and plasma-ion thrusters

2021 ◽  
pp. 28-34
Author(s):  
Zongshuai Guo
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Cross Section ◽  
Radial Distribution ◽  
Electric Propulsion ◽  
Mirror Reflection ◽  
Radial Magnetic Field ◽  
Ion Thrusters ◽  
Wall Conductivity ◽  
The Cross

The subject matter of the article is the radial distribution of electrons movement parameters inside electric propulsion thrusters with closed electrons drift. The radial magnetic field in Hall effect thrusters is the limits the axial flow of electrons because of interaction with azimuth electron current. In turn, this azimuth current exists as a result of rivalry between the attempt of the magnetic field to transform electrons current completely closed one and the loss of electrons rotation moment in collisions. Similar processes take place in the ionization chamber of plasma-ion thrusters with the radial magnetic field. The attempts to estimate electrons parameters through only collisions with ions and atoms inside volume have given the value of axial electrons current much lower than really being. This phenomenon is called anomalous electrons conductivity, which was tried to be explained as a consequence of various effects including "near-the-wall-conductivity", which was explained as a result of non-mirror reflection of electrons from the Langmuir layer near the walls of the thruster channel. The disadvantage of this name is the fact that the reflection of the electron occurs before reaching the surface from the potential barrier at the plasma boundary with any environment: the wall, but also with the environment vacuum. The potential distribution in the Langmuir layer is non-stationary and inhomogeneous due to the presence of so-called plasma oscillations. The definition of "conductivity" is just as unfortunate in this name, because the collisions are always not a factor of conductivity, but on the contrary – of resistance. The goal is to solve the task of electrons rotation moment distribution in the thruster channel. The methods used are the formulation of the kinetic equation for electrons distribution function over the velocities, radius, and projections of the coordinates of the instantaneous center of cyclotron rotation; solution of this equation and finding with its use the distribution of the gas-dynamic parameters of electrons along the cross-section of the channel. Conclusions. A mathematical model of electrons rotation moment dynamics is proposed, which allows using plasma-dynamics equations to analyze its distribution along the cross-section of thruster channel and to estimate the effect of "near-the-wall-conductivity" using appropriate boundary conditions.

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