Identification of gas impurities in helium by selective registration of groups of fast electrons created in Penning ionization of impurities atoms or molecules by metastable helium atoms at pressures of 7-40 Torr is realized. The collisional electron spectroscopy (CES) method is applied and is experimentally verified. Identification of impurities atoms and molecules is accomplished in collisional regime of movement of the particles, where the different groups of electrons have no time to relax in energy by collisions in the volume and behave independently of each other. An original design of microplasma gas analyzer is proposed, containing only nonlocal negative glow plasma of a short dc microdischarge. Registration of the energy spectra of penning electrons by means of an additional electrode-sensor, located at the boundary of the discharge volume is performed. The sensor has large collecting area compared to classical Langmuir probes, contributing to significant enhancement in the measurements sensitivity. Maxima in the EEDF are recorded in helium with small admixtures of krypton, argon and air. The obtained maxima appear at low discharge currents and at characteristic energies corresponding exactly to the expected maxima for penning electrons of the known gas impurities used. The gas analyser is compact, simple in technical performance, has high sensitivity and its size is dramatically reduced compared to the existing devices for gas analysis. This work is an approach to the development of microdischarge gas analyzers for gas impurities detection like poison gases, gas pollutions in the atmosphere or in the industry etc.
The influence of the 3He isotope as a buffer gas on the operating characteristics of the He-Kr hollow cathode laser is studied. A comparison of the laser output power and gain on the KrII 469.4 nm and KrII 431.8 nm lines in 3He-Kr and 4He-Kr gas mixtures is made and an increase of 33% is observed in the case of the 3He-Kr gas mixture. A simple qualitative analysis of the plasma kinetics shows that the observed increase of the laser output parameters is due to the increased rate constant for the excitation transfer reaction and the increased density of the He(2 3S1) metastable atoms and Kr ground state ions. The main reasons for this are the higher mean relative velocity of the colliding particles and the higher rate of electron cooling in 3He-Kr plasma. Peak output powers of 10 W and 1.5 W and small signal gains over the losses of 85% m-1 and 64% m-1 are measured for the blue and violet lines, respectively, from a 21 cm active length at 17.5 kPa 3He pressure, 17 Pa Kr pressure and 96 A peak current. These values are significantly higher compared to earlier investigations. The operating discharge conditions are enlarged considerably; up to 21 kPa He pressure and 100 A peak current. The laser design chosen contributes to the achievement of this goal.
It was shown that the spectrum of Penning electrons in a nonlocal equipotential plasma is associated with the second derivative of their current to a wall electrode (sensor). Analytical calculations are confirmed by experimental studies in a negative glow plasma of short DC glow discharge at moderate and high pressures (up to 150 Torr).
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