Toshio Atsuta

Development of high‐power chemical oxygen‐iodine laser for industrial application

A scaling up of kW‐class chemical oxygen‐iodine laser (COIL) is achieved. The key issues for the system design of COIL for industrial application is discussed. The scaled up COIL system of 1‐kW output power is now under trial operations. In these operations, a maximum output power of 1100 W, and a continuous operation time of more than 2 h with a power of over 500 W is recorded.

Long-term stability in the operation of a chemical oxygen-iodine laser for industrial use

The influence of solution composition to the generation of the excited oxygen O2(1Δ) for a chemical oxygen‐iodine laser is studied. Moderate power operation of 100 W for a duration of more than 3 h was achieved. For the achievement of long‐term operation, new types of devices for water vapor trapping and new NaCl separation were developed.

FLOW AND OPTICAL FIELDS IN A SUPERSONIC FLOW CHEMICAL OXYGEN-IODINE LASER

The flow and optical fields of a supersonic, flow chemical oxygen-iodine lasers are simulated by solving the three-dimensional Navier-Stokes equations and the paraxial wave equation, and the laser power extraction characteristics are studied. The effects of the wall catalysis are also discussed by introducing the surface catalytic efficiency into the wall boundary condition. The numerical results show that the pair of contrarotating vortices behind the curved jet greatly enhance the mixing and the simultaneous chemical reaction. The effect of the residual flow non-uniformity on the output laser beam is small due to the low Mach number and the fairly good mixing. The wall catalysis reduces the laser performance in case a plenty of excited species diffuse toward the wall of nozzle blades.

Development of chemical oxygen-iodine laser for industrial application

Since the first oscillation of a ruby laser obtained in 1960, an enormus amount of efforts have been concentrated on laser researches. Fundametal researches were almost finished in 1960s, then aims of investigations were turned to find out new applications.

COIL activities in Japan (Industrial COIL development)

Chemical oxygen iodine laser (COIL) is the only laser expected to be applied for thick plate cutting, for instance, by high laser power over 5 kW transferred to the processing fields by the optical silica fiber. As a result of the first stage of industrial COIL development, a 1 kW subsonic COIL was delivered as a commercial processing device first in the world in 1992. The supersonic COIL development was carried out at the second stage and the output power of over 5 kW was obtained in 1995. Using this high power beam, superiority of the COIL as an industrial laser was studied by processing metals.

Mixing/Reacting Zone Structure and Small Signal Gain Coefficient of a Supersonic Flow Chemical Oxygen-Iodine Laser

The flow field of a supersonic flow chemical oxygen-iodine laser is simulated solving three-dimensional Navier-Stokes equations, and the dependence of the mixing/reacting zone structure and the resulting gain region on the effective velocity ratio of I2 jet to the primary flow is studied. It is assumed that the flow is laminar and the water vapor condensation due to the supersonic cooling is ignored. A chemical kinetic model encompassing 21 chemical reactions and 10 chemical species is used to determine the chemical composition of gas mixture. The I2He ratio and plenum pressure of the secondary flow are varied in order that the amount of iodine injected into the primary flow is kept constant in each effective velocity ratio. The present results demonstrate that a pair of contrarotating vortices generated behind the I2 jet greatly enhances the mixing and the simultaneous chemical reaction of I2 and O2(1

Industrial chemical oxygen-iodine laser

DELTA). It is shown that the optimum condition for the secondary I2 jet momentum exists. The I2 jet which causes the high gain penetrates into the primary flow moderately deeply and does not collide with the counter one.

Current status of industrial COIL development

Having succeeded the oscillation of 6 kW output power by a supersonic flow, the chemical oxygen iodine laser (COIL) is now going to be realized as a new industrial laser by adopting various leading technologies.

Fatigue Design of an Offshore Structure

The chemical oxygen iodine laser (hereafter referred to as COIL) has been attracting attention for its potential on the usage for material processing. The completion of the COIL for material processing with such systems as the fuel recirculation equipment, continuous water vapor trapping facilities, and so on, is informed. The suitable resonator design is investigated. The experimental test was carried out with the stable-unstable resonator and a high quality beam of near diffraction limit at the unstable side was achieved. Now, the possibility of the COIL for processing is actually ascertained.

Theoretical and experimental investigation of a supersonic flow chemical oxygen-iodine laser

As a procedure of the safety design of offshore structures, a method of fatigue design is presented utilizing the dynamic response analysis of the structure and the stochastic data of wave, wind and tidal current. An actual design calculation was performed on a trussed leg of an offshore jack-up platform. The power spectra of wave and wind were first established using their significant values at the working area. The dynamic response of the platform was then investigated using a lumped mass model of three degrees of freedom system. From the frequency distribution function of the plastic strain variation obtained by the elastic stress concentration factors and the Neubers formula, the fatigue life of the platform was estimated applying the Palmgren-Miner rule and the prescribed design fatigue curve of the material, in which the cumulative damage was evaluated taking into account all the loads of wave, wind and tidal current.