Presence Of Light Ions Research Articles

Oscillating Two Stream Instability of a Laser in a Two Ion Species Plasma

The oscillating two stream instability (OTSI) of a high amplitude laser or a plasma wave in near-critical density high-Z plasma is influenced by the presence of light ions. A regime of OTSI arises where the low frequency response of electrons and light ions is adiabatic but the heavy ion response is much slower. As a consequence the low frequency mode is not a purely growing mode but has a finite real frequency as well. In the case of a pump, radially localized in a suitable density profile, the growth rate is reduced and the wavelength of the maximally growing mode is enhanced.

Experimental study of structure and stability of an intense neutralized electron beam

A maximal electron current in a neutralized electron beam is constrained by the beam-drift instability of the primary electrons and the neutralizing ions. To suppress this instability and to increase the threshold of the electron current, the active methods are usually used. As a result of the application of these methods the spectrum of neutralizing ions is changed. The measurement of the ion mass spectrum is performed with the special ion mass analyzer. The experiments on the JINR test bench show that the presence of light ions (hydrogen) in the beam decreases the threshold beam current related to the beam-drift instability.

Determination of thermospheric temperatures and neutral densities at Arecibo from the ion energy balance

We use incoherent scatter measurements of ion and electron temperature and electron density to infer exospheric neutral temperatures and thermospheric atomic oxygen densities from the ion energy balance equation. Measurements obtained at four periods in 1985 and 1986, during the recent solar cycle minimum, are examined. At all seasons, the MSIS‐86 empirical model of the thermosphere is found to overestimate daytime exospheric temperatures at Arecibo by an average of about 50°K. We find that daytime concentrations of H+ are not negligible at Arecibo at solar cycle minimum. Unless the presence of light ions is accounted for when analyzing autocorrelation functions measured by the incoherent scatter technique, significant errors can be made in determining the ion temperature and inferring the exospheric temperature. Deduced atomic oxygen densities are in good agreement with the MSIS model if it is adjusted to match the observed neutral temperatures and the commonly used value of the O+‐O collision cross section is increased by 70%.