We have demonstrated the measurements of attenuation constant of a multi-mode fiber (300μm core diameter and 1km
length) at 1070nm. The observed attenuation constant was below 0.7dB/km. The laser power of 5kW was coupled into
the 1km fiber at 1070nm. The overall transmittance was 85 %. We observed the first Raman stokes in the transmitted
laser spectrum.
We demonstrated concrete cutting with a 4kW fiber laser at 1070nm. The demonstrated slab thickness was 100mm.
This technique can be extended to thick concrete slabs more than 1m without laser power increasing.
A new nozzle bank for an ejector-chemical oxygen-iodine laser consisting of two-dimensional slit nozzles with a trip-jet mixing system was designed, fabricated, and tested in the cold flow operation regime. A computational fluid dynamics (CFD) is used to optimize the trip system design. Horizontal Pitot scan experiments demonstrated that the mixing ability of the trips is excellent. The Mach number of the mixed flow was approximately 3. The average Pitot pressure at the laser cavity was more than 100 Torr. Backpressure tests were conducted, and the results of these tests revealed that the static pressure in the cavity remained constant at approximately 10 Torr until the supersonic diffuser breaks back and the cavity unstarts at a backpressure of approximately 80 Torr.
The transmission of chemical oxygen-iodine laser (COIL) emission through several kinds of multimode quartz optical fiber is measured in order to explore the applicability of COILs for the extraction of natural resources. The minimum transmission loss through these fibers is 0.64 dB/km, and high-power transmission for a distance of kilometers is shown to be feasible. Laser emission at an average input power of 1 kW is successfully transmitted through a multimode optical fiber for a distance of 1 km with an efficiency of 80%.
Chemical oxygen-iodine laser (COIL) has a great potential for applications such as decommissioning and dismantlement (D&D) of nuclear reactor, rock destruction and removal and extraction of a natural resource (Methane hydrate) because of the unique characteristics such as power scalability, high optical beam quality and optical fiber beam. Five-kilowatt Chemical oxygen-iodine laser (COIL) test facility has been developed. The chemical efficiency of 27% has been demonstrated with a moderate beam quality for optical fiber coupling. Our research program contains conventional/ejector-COIL scheme, Jet-SOG/Mist-SOG optimization, fiber delivery and long-term operation.
KEYWORDS: Methane, Chemical oxygen iodine lasers, Fiber lasers, Wind energy, Energy efficiency, High power lasers, YAG lasers, Optical fibers, Physics, Gas lasers
Possibilities to extract methane from methane hydrate are discussed. COIL is a unique solution from technological and economical stand points and systems for excavation are proposed
This report describes the experimental and theoretical analysis of a cross-flow jet-type singlet oxygen generator (cross-flow J-SOG) in order to identify the optimal conditions needed to satisfy the ejector-COIL requirement. The optimal conditions had been analyzed under various generator geometries (reaction region length, jet diameter, and chlorine inlet height), gas/BHP flow rates, and gas pressures. The performance was achieved Cl2 utilization of 90% and O2(1Δ) yield of 70% at the plenum pressure of 20 Torr.
Possibilities to extract methane from methane hydrate are discussed. COIL is a unique solution from technological and economical stand points. COIL system suitable for excavation are proposed.
Chemical oxygen-iodine laser (COIL) has a great potential for applications such as decommissioning and dismantlement (D&D) of nuclear reactor, rock destruction and removal and extraction of a natural resource (Methane hydrate) because of the unique characteristics such as power scalability, high optical beam quality and optical fiber beam. Five-kilowatt Chemical oxygen-iodine laser (COIL) test facility has been developed. The chemical efficiency of 27% has been demonstrated with a moderate beam quality for optical fiber coupling. Our research program contains conventional/ejector-COIL scheme, Jet-SOG/Mist-SOG optimization, fiber delivery and long-term operation.
Analysis of heat release into operative gas of Chemical Oxygen Iodine Laser (COIL) is discussed. Pooling reaction of oxygen molecules in the excited state, the iodine dissociation process and the interaction of them with water vapor release energy of in the excited state oxygen molecules as heat energy. As results of heat release in the plenum, a rise of the total pressure as a rise of the total temperature is observed, and in the supersonic region a rise of static pressure and a decrease of total pressure as a rise of total temperature are observed. By following our analysis technique regarding pressure data of three different nozzles, the evaluations such as energy loss in a duct from a Singlet delta Oxygen
Generator (SOG) and the number of dissipated oxygen molecules for the iodine dissociation can be estimated.
A cross flow jet SOG has been developed in Miki Pulley Co. Ltd. to supply O2(1D) for different types of COILs. Performance testing of the SOG has been conducted through a wide range of gas pressures (5~40 Torr), specific surface areas (4~7 cm-1), gas velocities (5~30 m/s), and gas temperatures to characterize and optimize the device. The inflow and out flow of the reactants and products, including O2(1D), Cl2, H2O were measured using optical and conventional techniques. The gas temperatures in the measurement duct were estimated from stagnation pressures, mass flow rates, and critical cross section at the gas chocking point in order to determine the partial pressures of the gas products at the measurement point. Calibration method of the O2(1D) measurement suggested by Zagidullin is basically employed with a slight correction of upper limit definition of O2(1D) yield associated with the pooling loss, which remains even at the minimum P t condition of our device. Assuming that the gas temperature after passing through the jets is equilibrium with that of the BHP jets (-18 degree Celsius) in our calibration condition, the upper limit yield can be derived from the increase in the gas temperature. The estimated value of the yield limit was 94 %. A wide range of output values (40-95 % of Cl2 utilization, 50-90 % of O2(1D) yield) was obtained and analyzed to characterize the device. As a result of optimization, a 27 % of chemical efficiency was obtained when Cl2 utilization was 95 %, O2(1D) was 90 %, O2 partial pressure was 6.7 Torr, and N2 dilution ratio was 2. Discussion on the validity of the gas temperature estimation method is provided by comparing the results to the heat release based on the pooling model.
Miki Pulley has pursued the development of a prototype COIL module for field and industrial applications since its transfer from Tokai University in 2000. The test module has already been constructed in our laboratory. The current status of the development is presented. The achieved chemical efficiency was 17.5% at the chlorine flow rate of 13.2mol/min. The corresponding laser power was 3.5kW.
KEYWORDS: Diffusers, Throat, Iodine, Chemical oxygen iodine lasers, Laser resonators, Chemical analysis, Chemical reactions, Molecules, Laser development, Chemical lasers
Optimization of iodine injection scheme was conducted in Miki Pulley Co., Ltd. using CFD approach. Variation of the mixing speed as a function of an I2 jet penetration depth, nozzle expansion ratio, and I2 injection point are analyzed. It was found that the inherent geometry of our nozzle and I2 injector affects the I2 mixing process. Influence of a backpressure to the cavity flow condition was also investigated in order to estimate the pressure recovery capability of our diffuser. The normal shock based diffuser efficiency for Mach=2.7 flow was 54.5%.
Laser medium parameters of multi-kW grid nozzle supersonic Chemical Oxygen Iodine Laser (COIL) were experimentally studied. Small-signal gain (SSG) diagnostics was done by a narrow line width tunable laser by scanning 1 GHz range around (2P1/2 ) - (2P3/2) spin-orbit transition line of atomic iodine. SSG was investigated as a function of Mach number and gas flow rates. Modeling of gain for different flow conditions was done as well. Multi-kW COIL device was recently developed in Miki Pulley Co., Ltd. (Japan) and has 37.5 cm length of active medium.
A new strategy for pulse oscillation of chemical oxygenÑiodine laser based on a combination of a porous pipe SOG with an instantaneous atomic iodine generation, has been developed to seek the potential of COIL as an amplifier of the nuclear fusion driver. This new scheme allows one to produce a large aperture high pressure laser medium, which is favorable to the laser amplifier, while maintaining a minimum degradation of stored energy by water vapor. The experimental apparatus consists of the porous pipe SOG, an iodine donor (CH3I) injector, a flash lamp for the iodine dissociation, and an optical resonator. Operational characteristics of the apparatus including dependence of output energy on an iodine concentration was studied. As the result, the maximum output energy of 800mJ was obtained. It was also found that the CH3I was dissociated through unidentified chemical reaction associated with the O2(1Æ).
A study of chemical oxygen-iodine laser (COIL) for the use of decommissioning and dismantlement of nuclear facilities is conducted. A scaled-down model was developed as a prototype. Laser duct and optical cavity were designed so that it can be operated in both supersonic mode and high-pressure subsonic mode for the comparative study. A 1.34kW output with chemical efficiency of 24.6% was obtained in the supersonic mode. In the high-pressure subsonic mode, output power was 1 .12kW with chemical efficiency of 20.6%. A subsonic operation at 12Torr was demonstrated for the first time. A preliminary experiment of thick steel cutting was demonstrated by the developed system. The obtained data was in good agreement with published data.
High-pressure subsonic mode operation of chemical oxygen- iodine laser (COIL) is studied. In this mode, the singlet oxygen generated by the liquid-jet singlet oxygen generator (SOG) is directly utilized in the optical cavity without supersonic expansion. Drastic reduction of the required vacuum pump capacity, and iodine consumption was obtained. We have demonstrated a 25.0 percent of chemical efficiency with a small-scale device. The scale-up version of the COIL is developed and initial tests are conducted. The device is so designed that it will operate for 2 hours at 1kW laser output. Due to the inadequate heat exchanger of basic hydrogen peroxide (BHP), performance of the system was not yet satisfactory. However, a 30-minute continuous operation o the counter-flow type jet SOG with recirculation of BHP was demonstrated for the first time.
Development of Chemical Oxygen-Iodine Laser (COIL) in Tokai University is described. From FY1996, we have conducted a three-year research project sponsored by NEDO (New Energy and industrial technology Development Organization), and it was finished in March 1999. As a result, high-efficiency operation (23.4%) of COIL with nitrogen as a buffer gas was demonstrated. Reduction of the vacuum pump size by the high- pressure subsonic mode operation with turbo blower was demonstrated. Specific energy reached to 3.5 J/liter. Output power stabilization/modulation technique by the external magnetic field was developed. Twisted Aerosol Singlet Oxygen Generator (TA-SOG) was tested and its performance was compared to liquid-jet SOG. TA-SOG was operated at the internal gas velocity of 85 m/s. Novel unstable resonator was developed with the aid of newly developed FFT code. We are now conducting a one-year project whose goal is a development of a 1 kW-class system capable of one-hour stable operation. Finally, three operation modes of future industrial COIL are proposed.
Output power enhancement of Chemical Oxygen-Iodine Laser (COIL) by pre-dissociation of molecular iodine using a microwave discharge was demonstrated. Two types of approach, transonic operation with grid nozzle and supersonic mixing with ramp nozzle array were tested. In the transonic operation case, a gas velocity at the laser cavity was estimated to be 167 m/s, and I2 dissociation rate was found to be 50%. As a result, 9% of output power enhancement with the microwave pre-dissociation was obtained. In the supersonic injection case, we have initially obtained very poor output power. When we changed the gas flow rates, cavity flow returned to subsonic and we have obtained 284 W output power with 16% of chemical efficiency. No output power enhancement with microwave adoption was observed for ramp nozzle array. It was due to the insufficient dissociation of iodine due to the high stagnation pressure of secondary flow.
Rock excavation experiment with a 10kW-class CO2 laser was demonstrated as a basic study for field application of high power lasers. Sample rocks used in this experiment as a workpiece were tuff breccia and granite. Effect of assist gases on the excavation rate was surveyed. Oxygen, nitrogen, and air were examined and found not to be useful. It was because the gas flow could not blow the molten rocks off, but only helps to cool in case the hole races certain depth. Excavation rate on both rocks for a various output powers was measured to determine thermal constants inherent to each rock. It was found that the excavation rate resulted in slower, as the hole becomes deeper, because of the deterioration in evacuation efficiency of the molten rock. Thermal parameters of the both rocks were derived from the experimental results. Using simplified thermal balance model, it was estimated that a 50 kW-class mobile laser system has a potential to outperform the conventional mechanical excavation technique.
Conceptual designs of a chemical oxygen-iodine laser (COIL) facility for decommissioning and dismantlement (DD) of nuclear facility is proposed. The requisite output power and beam quality was determined base don our preliminary experiments of nonmetal material processing. Assuming the laser power of 30kW, it is derived that the beam quality of M2 equals 36 required to cut a biological shield wall of a nuclear power plant at a cutting speed of 10mm/min. Then the requisite specification of an optical fiber to deliver the laser is calculated. It turned to be quite extreme, core diameter of 1.7mm and NA equals 0.018. The mass flow and heat balance of proposed facility is calculated based on our recent COIL studies. With the high-pressure subsonic mode, the vacuum pump size is minimized compared to the supersonic operation. Finally, the size of the facility is estimated assuming tow-hour continuous operation. It is revealed that such a system can be packed in five railway containers.
KEYWORDS: Magnetism, Chemical oxygen iodine lasers, Chemical lasers, Zeeman effect, Beam controllers, Laser stabilization, Control systems, Signal detection, Servomechanisms, Power supplies
Laser power control of chemical oxygen-iodine laser based on the servomechanism was demonstrated with a Zeeman effect. Response of the feedback system in frequency domain was analyzed and compared to the experimental results. With this feedback system, fluctuation of the laser power was successfully reduced to plus or minus 0.4% in the presence of a disturbance.
Brief history and present status of the industrial COIL (Chemical Oxygen-Iodine Laser) studies in Japan are introduced. Up-to-date experimental results obtained by Tokai University group, including high-power subsonic operation, power stabilization, and theoretical works are presented.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.