Elevated Gas Temperatures Research Articles

Electron Attachment in Ionized Flows at Elevated Gas Temperatures

An ionized argon flow (electron concentration of the order of 1012 per cm3), at elevated gas temperatures, is obtained by arc heating. The flow is admitted in a mixing chamber where small additive fractions (order of 10-4) of an electrophilic compound, (SF6), are injected into and mixed with the flow. The mixtures are incubated under specified incubation conditions (3000° to 5000°K, 0.1 to 1 atm, 10-3 to 10-4 sec). Electron and ion concentrations are determined at the end of the incubation and for this, both single and double Langmuir probes are used. Auxiliary probing is also carried out by an x-band microwave beam. Suppression of the electron concentration by factors ranging from 2 to over 1000 are determined, depending on experimental conditions. By experimental evidence it is demonstrated that the suppression of the electron concentration is the result of negative ion formation and survival. Charge neutralization processes are relatively negligible.

Electron temperatures in hot argon-potassium discharges

The mean electron energy in argon-potassium plasma at elevated gas temperatures (1000-1300°K) and at high gas pressure (1 atm) has been obtained from the analysis of floating double-probe curves. Because of the potassium vapour deposit on the probe surface, considerable thermionic electron emission takes place. As a result, the probe curves straighten so that neither the ion saturation current nor the electron temperature can be determined any longer. These curves can, however, be used for estimating the electron temperature by comparing them with a standard curve obtained at a known electron temperature which is equal to the gas temperature when the discharge is absent. Thus the ratio of the electron temperatures equals the ratio of the slopes of two probe curves.

Electron Removal During the Early Oxygen Afterglow

Microwave diagnosis showed that the early afterglow of an oxygen plasma was controlled by ambipolar diffusion and by recombination (αr), depending upon pressure (from 0.15–4.0 mm Hg), at elevated gas temperatures (up to 900°K). At Tgas=300°K attachment also seemed to be important for higher pressures (p>0.65 mm Hg). For low plasma excitation energy the measurements yielded αr=2.1×10−7 cm3 sec−1 at Tgas=300°K, dropping gradually to 1.4×10−7 cm3 sec−1 at 894°K. The plasma excitation energy had a marked effect on the apparent recombination and attachment rates which tend to indicate that vibrationally excited ions and molecules do affect these rates as has been suggested previously.

The electric strength of fibrous glass

The ideal, and probably future, use of fibrous glass for electrical insulation is without an organic filler. Therefore, it is important first to know its electric strength in unimpregnated condition. Test results show its high qualities at elevated gas pressures and temperatures.