Setsuo Suzuki

Improvement in the Output Characteristics of a Large-Bore Copper Vapor Laser by Hydrogen

It has been experimentally confirmed that addition of about 1% hydrogen gas to the copper vapor laser (CVL) discharge improves the output characteristics of a large-bore CVL with 80 mm beam diameter and 1500 mm discharge length. The annular distribution of the beam intensity became uniform and the output power increased. The increase in the green laser power was larger than that in the yellow one. The hydrogen gas addition was effectual when the input power to the discharge was large and the copper temperature was high. A 120 W output power was obtained continuously for 26 hours.

Characteristics of a large-bore copper vapor laser with gas-cooling plates

It has been experimentally found that the insertion of plates into the plasma tube has improved the output characteristics of an 80-mm copper vapor laser. It has been revealed that the buffer gas temperature decreases and the metastable-state (the lower laser level) density of copper atoms decreases near the center axis of the plasma tube. Moreover, electric power is transferred into plasma more efficiently because of the increase in plasma impedance. As a result, the average output power is increased by 57 % and the beam intensity profile has become uniform.

Copper density measurement of a large-bore CVL

The ground state and the lower laser level copper densities were measured in a large-bore copper vapor laser (CVL). The beam diameter was 80 mm, the discharge length 1500 mm, and the output power about 100 W at an operation of a repetition frequency 5 kHz. A new laser-absorption method has been developed to measure the copper ground state density. The measured copper density of the ground state was 1 to approximately 5 X 1021 m-3 and the radial profile was hollow. The profile can be explained from the radial gas temperature profile. The lower laser level (metastable state) densities were measured by the ordinary laser-absorption method. The density of the lower laser level for green emission was about 1 X 1018 m-3 and that for yellow emission was about 3 X 1017 m-3 at the center. The lower laser level densities were higher at the center than near the wall in contrast with the ground state density.

Output characteristics and improvement in beam-profile of large-bore copper vapor lasers

Alumina plates (Gas-cooling plates) were inserted into the plasma tube of copper vapor lasers to cool the buffer gas at the center of the plasma tube. Consequently, the laser intensity increased, especially at the center, and higher output power was obtained. It was revealed by measurement that the gas-cooling plates reduce the buffer gas temperature and the lower laser level density of copper atoms at the center of the plasma tube. Output characteristics were measured by varying the repetition frequency. Plate insertion improved the central intensity at higher frequencies. Output power was most dependent on the frequency with the plate inserted, and increased proportionally as the frequency increased.

Glow Auxiliary Electrical Discharge for CW High-Power CO2 Lasers

A new discharge technique for DC glow auxiliary electrical discharge (GAED) lasers has been developed in order to realize efficient, stable and compact CW transverse-flow high-power CO2 lasers. The auxiliary discharge power source for GAED is common to that of the main discharge. This paper describes the discharge technique and characteristics of GAED. The luminous region of the positive column with auxiliary discharge became wider and more uniform than that without auxiliary discharge. The limited glow discharge power Wg* (the discharge power for initiating unstable glow discharge) with auxiliary discharge was about 2.2 times that without auxiliary discharge. It was also found that the maximum value of Wg* was obtained when the CO2 gas mixture ratio was 2-4%.

Discharge And Output Characteristics Of CW-CO 2 Laser With Auxiliary Glow-DC-Discharge

A transverse-flow, cross-discharge cw-C02 laser with an auxiliary glow-DC-discharge was developed. The maximum input power increased twice to four times as large as that without the auxiliary discharge. A single-path resonator with 65 mm-aperture and a Z-path resonator with 45 mm-aperture were set up. The output power exceeding 3 kW was obtained for both type resonators with 40 cm-long-discharge area. We deduced an equation which gave the output power for the Z-path resonator. The calculated results agreed with the measured output power.

Multiple hollow‐cathode vacuum‐ultraviolet plasma source excited by pulsed glow discharge

A multiple hollow‐cathode vacuum‐ultraviolet source excited by a pulsed glow discharge in a mixture of Xe and He has been developed. A MgF2 window with a diameter of 55 mm was used, and the repetition frequency was varied between 3 and 9 kHz. Stable output was maintained for about 3 h. Measurements of 147 nm radiant illumination were made at various distances from the window at various repetition frequencies. The peak radiant illumination decreased while the average radiant illumination increased with increasing repetition frequency. The output power density near the center of the window could be estimated from the relationship between measured radiant illumination and distance from the window. The peak and average output power densities at 6 kHz were 30 and 1.5 W/m2, respectively.

Output characteristics of a transversely excited copper vapor laser

A maximum output power of 13.2 W was obtained at a high repetition frequency of 5 kHz by a transversely-excited copper vapor laser with an excited volume of 112 cm3. Its specific output power density was 118 mW/cm3. It corresponded to a specific output energy density of 24 (mu) J/cm3. We also examined the dependence of the output power on the buffer gas pressure, the repetition frequency, and the charging voltage.

Radial Profiles of Electron Density and Current Components at Cathode Surface in LaB6 Hollow Cathode Arc

Experimental studies on a hydrogen-fed LaB6 hollow cathode arc have been pursued. The plasma parameter in the cathode has been measured by a Langmuir probe. The radial variation in the electron density inside the cathode was calculated using the continuity and momentum equations, showing good agreement with the experimental results. The electron density at the cathode surface was estimated to be 15%–20% of that at the cathode axis. It was also found from the current balance that the arc current components at the cathode surface consist of a thermionic current which takes into account the Schottky effect, the ion current and the secondary electron current induced by ion bombardment. The ion current and the cathode surface is larger than the electron current emitted from the cathode.