Adischarge cleaning experiment was carried out in JFT-2 Tokamak by using a low electron temperature plasma of hydrogen produced by electron cyclotron resonance (ECR) discharge. By the use of 2.45 GHz, 2 kW cw microwave. The electron temperature and density of the plasma were typically 4 eV and 1.2 x 10¹⁰ cm^-3 respectively. Under quasi-equilibrium condition, comparison between the ECR discharge cleaning and the Taylor discharge cleaning (TDC) was done by observing the partial pressures of CH₄, H₂O and CO gases. The TDC was carried out with a plasma with electron temperature of 4.1 eV and density of 3.5 x 10¹² cm^-3, produced with a pulse width of 10 ms and a repetition frequency of 0.67 Hz. Both cleaning methods were found to have the approximately equal cleaning effect. This shows the applicability of the ECR-DC to advanced Tokamaks.

抄録全体を表示

The design and performance of a new type of ionization gauge, specifically developed for an accelerator, equipped with an ionsource constructed in combination of three electrodes (a hemisphere mesh anode, an annular filament and a funnel-shaped electron reflector) is described. In order to improve the signal-to-noise ratio, the ion current is converted into an alternating current signal by a modulator grid located beneath the ion outlet of the ion source. The new gauge has a sensitivity factor for nitrogen of 14 Torr^-1 and a modulation factor of 1.00.

抄録全体を表示

R. F. reactive sputtering of iron in mixed argon-oxygen atmospheres has been investigated by means of measurements of deposition rate, electrical resistivity, and X-ray and electron diffraction. Thin films of iron oxides were deposited on glass, alumite, and (001) NaCl substrate, while changing the oxygen partial pressure from 2 × 10^-4 to 5 × 10^-2 Torr at a total pressure of 1.5 × 10 ^-2 Torr.
A hysteresis of the deposition rate was found in an increasing and decreasing cycle of the oxygen partial pressure. This phenomenon was explained by a model based on the relative relation between the sputtering rate and the oxidation rate of an iron target surface. Hence, two stationary reactive sputtering states were found to exist between certain critical values p^* and p^**, where the depositon rate changed drastically. One was a high deposition rate, the other was a low one, associated with a clean iron target and an'oxidized one, respectively. In the former state, Fe₃O₄ single phase films were obtained by controlling the deposition rate. Properties such as lattice constant, microstructure, and orientation of the deposited Fe₃O₄ films formed at various oxidation degrees were also examined.

抄録全体を表示

A new type of high-speed ion pump using a multipactor cathode is proposed and the results, obtained in our experiments of the pump which was manufactured by way of the first trial, are described. The multipactor cathode has excellent characteristics for such a use, as follows; 1) it does not contaminate vacuum condition, because it is a cold cathode made of some pure metal, as like as Al. 2) electron emission density is considerably high. 3) ionization rate of supplied electrons can be increased largely compared with any other electron supply method. 4) supply of electrons into a considerably wide area is quite easy.
We could confirm an advantageous characteristic of the pump, that is, the maximum pump current per unit volume reached up to 30 times as much as that of a usual ion pump in vacuum conditions of less than 10 ^-4 Pa.

抄録全体を表示