A search with the large solid angle spectrometer (ARES) for the lepton-number-nonconserving decay mu + to e+e+e- has been carried out. Cylindrical multiwire proportional chambers and cylindrical scintillation hodoscopes were used. The upper limit for the branching ratio Gamma ( mu + to e+e+e-)/ Gamma ( mu + to e+ nu e nu mu )

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A scheme for calculating populations of excited levels and intensities of spectral lines in the positive column of helium discharges at intermediate pressures ( p > 5 Torr) is proposed. The electron distribution obtained from the Boltzman equation is taken into account. The distribution is strongly non-Maxwellian for electrons of energy more than 19.8 eV.Concentrations of atoms on excited levels (n= 2, 3, 4, 5) are obtained from balance equations for the population of those levels. The concentration of level 2 % is the highest. The concentration of 2 % is much less than that which would exist in the case of quasithermodynamic equilibrium between levels 2% and 2IS. The population of higher levels (n> 2) is determined by excitation from levels 23s and 2% For singlet levels the excitation from level 2% is important.Population inversion is obtained between levels 3lP-3ID, 4 I P 4 D , S1S4'P, 43S-33P, 53%I3P and 5 3 P 4 D .

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supplies, and data acquisition system. Basic characteristics of the spectrometer are systems, cylindrical scintillation hodoscopes, a magnet, electronics with power proportional chambers (~l5000 signal wires) with gas supply and gas leakage particle and nuclear processes is described. The spectrometer consists of cylindrical A magnetic spectrometer intended for wide range of investigations of rare