Charge Exchange Of Hydrogen Atoms Research Articles

COLLISIONLESS SHOCKS IN A PARTIALLY IONIZED MEDIUM. III. EFFICIENT COSMIC RAY ACCELERATION

In this paper we present the first formulation of the theory of non-linear particle acceleration in collisionless shocks in the presence of neutral hydrogen in the acceleration region. The dynamical reaction of the accelerated particles, the magnetic field amplification and the magnetic dynamical effects on the shock are also included. The main new aspect consists however in accounting for charge exchange and ionization of neutral hydrogen, which profoundly change the structure of the shock, as discussed in our previous work. This important dynamical effect of neutrals is mainly associated to the so-called neutral return flux, namely the return of hot neutrals from the downstream region to the upstream, where they deposit energy and momentum through charge exchange and ionization. We also present the self-consistent calculation of Balmer line emission from the shock region and discuss how to use measurements of the anomalous width of the different components of the Balmer line to infer the cosmic ray acceleration efficiency in supernova remnants showing Balmer emission: the broad Balmer line, which is due to charge exchange of hydrogen atoms with hot ions downstream of the shock, is shown to become narrower as a result of the energy drainage into cosmic rays, while the narrow Balmer line, due to charge exchange in the cosmic-ray--induced precursor, is shown to become broader. In addition to these two well-known components, the neutral return flux leads to the formation of a third component with intermediate width: this too contains information on ongoing processes at the shock.

Possibility of using active secondary charge-exchange particle diagnostics for measuring the magnetic field direction in the plasma of a magnetic fusion reactor

An active particle diagnostic method based on the secondary charge exchange of hydrogen atoms of a probing (diagnostic) beam is proposed for local measurements of the magnetic field direction in the plasma of a thermonuclear fusion reactor. Experiments with new-generation large devices require searching for novel methods for measuring the direction of the total magnetic field in a plasma at different points along the radius of the plasma column. The main idea of the method proposed, which holds great promise for large devices, is outlined. The possibility of using the method on ITER—a large fusion reactor that is now at the design stage—is illustrated by carrying out relevant numerical simulations. The results obtained for one of the main discharge scenarios, with the injection geometry and probing beam energy (100 eV) that are now adopted for the ITER design, show that the method can provide local measurements of the magnetic field direction (the magnetic pitch angle) and of the spatial variations of the field vector. Further analysis has revealed, however, that, from the standpoint of signal intensity and signal-to-noise ratio, it is expedient to increase the energy of the beam atoms to 200–250 keV. With such probing beams, the method ensures a spatial (radial) resolution of about 10 cm in the plasma core during a signal acquisition time of 10 ms. The magnetic pitch angle can be measured with an accuracy of 5 × 10−3 rad. An important advantage of the method proposed is its ability to directly measure the pitch angle of the magnetic field lines.

Charge exchange of hydrogen atoms on nuclei of multicharged ions

Charge exchange of hydrogen atoms on nuclei of multicharged ions

Polarization characteristics of the emission of the 1 D 2-state of an oxygen atom obtained as a result of charge exchange of an oxygen ion at a hydrogen atom

The possibility of significantly polarizing the emission of an ensemble of oxygen atoms obtained as a result of charge exchange of hydrogen atoms at oxygen ions is demonstrated.

Charge exchange of hydrogen atoms in carbon foils at 0.4–120 keV

Charge exchange properties of H atoms passing through thin carbon foils at incident energies from 0.5 to 120 keV/u are discussed in the context of charge transfer models. A model is presented in which the charge state equilibrium in the solid is explained by the overlap of the atomic and the solid-state electron wave functions in k space. Outside the solid, near the surface, charge exchange occurs by tunneling of electrons between the carbon surface and the exiting projectile.