Junji Nakata

STRIATED COLUMN APPEARING IN HIGH-FREQUENCY GAS DISCHARGE

Stationary striations appearing in the plasma column of low pressure argon h. f. discharge brought about in cylindrical discharge tube of diameter from 5.8 to 18 mm are investigated experimentally for the pressure range from 0.07 to 8 mmHg. Their spatial intervals (so-called “wave-length”) are proportional to the electrodes distance within a limited range of the wave-length. The relation between the wave-length and the electrodes distance is shown by sawteeth-like characteristics. The wave-length increases linearly as the radius of the discharge tube increases. But it decreases exponentially as the gas pressure increases. The influence of the frequency of the h. f. source does not exist over a range from 5 mc to 53 mc. The wave-length, however, increases as the h. f, power increases. When a d. c. voltage is superposed on the h. f. field through another pair of electrodes, striations move from positive side to negative side at a velocity proportional to the d. c. current. These results indicate that the st...

Method to produce a short pulse on rf discharge excitation slab-type carbon dioxide laser

We propose a novel system to produce the short pulse using a halved confocal of the unstable concave-convex resonator on radio frequency discharge excitation slab type carbon dioxide laser. This method is provided a full reflection concave mirror to have a function of variable curvature which can control using a piezo electric device (PZT). Generally, the slab type laser is directly modulated by applying pulse voltage for pulsation of laser. There is a large capacity and fluctuation of plasma at the transition of pulsation. Consequently, the pulse width is longer than 1.0 micro second and repetitive frequency is less than 10 kilo Hertz. On the other hand, the pulse oscillation by our proposed method has the short pulse width which is 300 nano second and maximum repetitive frequency is about 100 kilo Hertz. We can choose the pulse oscillation or the continuous wave (CW) oscillation at the each condition on same resonator. The peak power at the pulse oscillation is about 12 times as high as that at the CW oscillation.

Argon ion laser technique for higher degree of polymerization at deep area of dental restorative resin

We have developed a technique for a higher degree of polymerization at the deep area of dental restorative resins by argon ion laser irradiation. We provide an analysis of the resin materials by Raman spectroscopy and Fourier transform infrared spectroscopy.

Synthesis technique of diamondlike carbon films by laser ablation ion source in atmosphere

We have developed a technique of depositing a synthetic diamond-like carbon film on glass substrates in atmosphere at ambient temperature. By placing a glass substrate within the plume created by irradiating a carbon target with a Nd-YAG laser, we are able to deposit a diamond-like carbon film on the surface of the substrate. Using a highly purified graphite carbon target insures that only carbon ions are ejected and present in the plume. We will provide an analysis of the films by both vertical and diagonal irradiation (see Figs.1(A) and 1(B)), by Raman spectroscopy and electron probe micro analysis.