Average Charge State Research Articles

The Ion Temperature in a Plasma with Hot Electrons

The ratio between electron temperature and ion temperature in a hot plasma is calculated, using the following assumptions. The ion life time in the plasma is considered to be large as compared to the time required for the energy relaxation between different ion species. Ion confinement is due to an electrostatic potential well resulting from ambipolar diffusion in a trap confining the electrons. The different heating and cooling processes are considered and it is found that the ion temperature is proportional to the square of the average charge state of the plasma.

Delayed-Coincidence Study ofO++ Ne Collisions at 50-200 keV

Delayed-coincidence techniques have provided measurements of the distributions in values of $Q$, the energy transferred to inelastic processes, during ${\mathrm{O}}^{+}$ + Ne collisions at 50-200 keV. The average values $\overline{Q}$ of the $Q$ distributions remain almost constant as a function of ${r}_{0}$, the distance of closest approach of the colliding particles. For fixed ${r}_{0}$, the $\overline{Q}$ values vary slowly with bombarding energy and lie, for example, approximately 40 eV higher at 100 keV than at 50 keV. The flatness of the $\overline{Q}({r}_{0})$ functions is reflected in a similar independence of ${r}_{0}$ found in measurements of the average charges of the particles after collision. These results indicate that the collisions produce excitations only among $L$-shell electrons. However, some data describing the widths of certain $Q$ distributions indicate that $K$-shell excitations may occur infrequently among collisions that produce ${\mathrm{O}}^{+4}$ ions. Supplementing the data for inelastic energy transfers are determinations of average ionic charge states after collision, measurements of angular distributions of scattering cross sections, and calculations of inelastic energy-loss cross sections deduced from the $\overline{Q}$ data.

Charge Distribution of 16O Ions Produced from Tandem Accelerator

In an effort to obtain information about the acceleration of heavy ions in tandem accelerators, the charge state distribution of oxygen ions accelerated in the University of Washington FN tandem accelerator was measured at three terminal voltages and over a range of stripper pressures. It is found that the stripper pressure normally used is below the value required for equilibrium in the charge exchange process, but that at higher terminal voltages the average charge state of the ions can rise above the equilibrium value due to focusing effects in the accelerating tubes. This phenomenon has implications in the use of foil strippers with heavy ion beams. A useful empirical relation for the optimum stripper pressure for a given charge state is obtained.