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A nitrogen cluster beam (neutral particle intensity of 28.6 mAeq) is ionized by electron collisions in a Bayard-Alpert gauge type ionizer. The extraction efficiency of about 65% is obtained at an electron current of 10 mA with an energy of 50 eV. The mean cluster size produced at a pressure of 663 Torr and temperature of 77.3 K is 2×105 molecules per cluster. By the Coulomb repulsion force, multiply ionized cluster ions are broken up into smaller fragments and the cluster ion size reduces to one-fourth at an electron current of 15 mA. Mean neutral cluster sizes depend strongly on the initial degree of saturation Φ0 and are 2×105, 7×104 and 3×104 molecules per cluster at Φ0's of 0.87, 0.66 and 0.39, respectively.

Studies have been made of the problems encountered in the development of a large-sized catalytic pump for the pumping of hydrogen in nuclear fusion apparatus. An experimental pump having a speed of about 5000 liter/sec is assumed to use at partial pressures between 10-7 and 10-5 Torr. The influence of water vapor on the atomization of hydrogen at the rhenium filament is one of the problems, and is discussed from the structural point of view. The lifetime of the cuprous oxide layer is another important problem. A convenient method of oxidation of copper plates by atomic oxygen produced at an incandescent rhenium filament is proposed for the generation and regeneration of the oxide. The optimum temperatures of the cuprous oxide layer are also determined for the rapid desorption of water vapor from the oxide and for the effective reaction with hydrogen atoms.

An instrument has been constructed which can directly display on an oscilloscope time-resolved profiles of a spectral line emitted from a transient plasma. It has closely spaced 17 optical channels, and the wavelength coverage between the outermost channels can be varied from 10.4 to about 0.8Å by the proper choice of a grating and a magnifying cylindrical lens. Profile measurements can automatically be repeated with time resolution from 0.1 to 2 µs. The display of these time-resolved line profiles has been accomplished by means of electronic circuit. An example of application to a transient plasma is shown.