Laser-based methods are known to be more efficient than traditional approaches for a range of tasks that include dismantling obsolete nuclear reactors, maintaining railroad tracks in good working condition, stimulating chemical reactions, and separating isotopes. Among the attractions of lasers are fewer byproducts, increased reactor cutting speed, enhanced lifetime and capacity of the railway, and the ability to deal with toxic agents without igniting them. Moreover, laser techniques are more effective than other methods in processing radioactive waste. Realizing these capabilities takes a high-power laser with superior optical quality. Acceptable cost and efficiency are additional requirements. High-power CO2 lasers are commercially available; however, they are expensive and inefficient, and suffer from deteriorating optical quality as power increases. Alternatives include so-called chemical oxygen-iodine lasers (COILs) and CO lasers. But the COIL, too, is expensive, and there is as yet no industrial prototype. And although NUPEC Corporation, in Tokyo, Japan, has impressively demonstrated a 20kW CO laser for cutting large arrays of steel pipes and plates,1 the system lacks an optical cable of transferring CO radiation. Furthermore, the laser requires cryogenic components, which adds to its cost. We propose a CO laser2 that dispenses with the need for an optical cable by installing the laser head on the manipulator. Our concept is based on the discharge of stable homogeneous radio frequency (RF) in a supersonic stream and the demonstration of laser generation in a small-scale experimental installation.3 We also devised a computational model for scaling the CO laser with RF discharge. Supersonic expansion makes it possible to obtain the required cryogenic temperatures, and the RF discharge enables us to get optimal parameters for vibrational excitation of CO molecules without an electronic gun. The reduced ratio of the electric field to gas density (E/N) in a column of gas is stated in the literature.4, 5 With our model, we can calculate the power parameters of the CO laser and optimize them to obtain high values of output power and efficiency. The cost of the laser is kept low through use of standard elements, for example, compressor, RF generator, and power station. Owing to the high density of the gas in front of the supersonic nozzle of the laser head and behind the supersonic diffuser, the closed contour serves as a pipeline that enables flexible positioning of the laser head, for example, on the manipulator. Consequently, no optical cable is needed to transfer laser radiation. A standard compressor can be used because values such as pressure and Mach number can be maintained in a stream that makes it possible to restore pressure upon an input in the compressor up to 1atm. Themodel consists of calculations of RF discharge parameters, vibrational kinetic equations, and dynamic gas equations that describe a supersonic stream in the RF discharge zone. We have considered low-current RF discharge with electron photoemission from the electrode surface and injection of electrons from electrode sheaths in a positive column. A low-current RF discharge is realized when the ratio of the time required for the ions to drift through the sheath and reach the electrode to the period of the RF field is much larger than unity.6, 7 Thus, the electrode sheaths have no time to break up and exist simultaneously at both electrodes. Plausible applications for the CO laser include dismantling obsolete nuclear reactors and hardening of the surfaces of railway rails. Our next step will be to test the laser in applications involving toxic agents, in processing radioactive waste by extracting ruthenium, and separating isotopes of heavy hydrogen and uranium. These applications can be extended substantially only once the laser is commercially available.
5Vibrational excitation of CO molecules by infrared free electron laser
Vibrational excitation of CO molecules by infrared free electron laser
1Plasma spectroscopy in rapid manufacturing: Copper, titanium, aluminum, steel
The suitability of a new Rapid Machining tool for prototyping components out of a variety of metal powders was investigated. A high power laser is aimed at a substrate and material powder is supplied to the interaction zone. By translating the substrate in XYZ direction 3D geometries were created.A high power CO2 laser was used as energy source, the material powders under investigation were Copper, Ti-6Al-4V, Aluminum, and Stainless Steel SS304 (particle size 100 μm). Helium was used as shield gas. The incident CO2 laser beam power was varied between 300 W and 400 W, with the laser beam intensity distributed in a donut mode of 600 μm diameter.Metal vapor/plasma plume spectra were recorded using a Photonic Multi-Channel Analyzer, covering the spectrum from 300 nm to 800 nm. Plume temperatures for all materials were calculated to be in the range from 5900 K to 6200 K which is well below ionization temperature (8000 K). The metal vapor/plasma plume is classified as a weakly ionized plasma.The suitability of a new Rapid Machining tool for prototyping components out of a variety of metal powders was investigated. A high power laser is aimed at a substrate and material powder is supplied to the interaction zone. By translating the substrate in XYZ direction 3D geometries were created.A high power CO2 laser was used as energy source, the material powders under investigation were Copper, Ti-6Al-4V, Aluminum, and Stainless Steel SS304 (particle size 100 μm). Helium was used as shield gas. The incident CO2 laser beam power was varied between 300 W and 400 W, with the laser beam intensity distributed in a donut mode of 600 μm diameter.Metal vapor/plasma plume spectra were recorded using a Photonic Multi-Channel Analyzer, covering the spectrum from 300 nm to 800 nm. Plume temperatures for all materials were calculated to be in the range from 5900 K to 6200 K which is well below ionization temperature (8000 K). The metal vapor/plasma plume is classified as a weakly ionized plasma.
Read more51Review of radio frequency conditioning discharges with magnetic fields in superconducting fusion reactors
Wall conditioning techniques based on radio frequency (RF) discharges in fusion devices with permanent magnetic field were developed a few years ago. The first experiments of RF plasma discharges in the ion cyclotron frequency range called ion cyclotron conditioning were performed in Tore Supra and Textor and later also in HT-7 and W7-AS. A high conditioning efficiency in terms of hydrogen removal and surface cleaning has been demonstrated. The other alternative, RF conditioning discharges in the electron cyclotron range of frequencies and called electron cyclotron conditioning, has also been studied in the recent past. Besides surface hydrogen removal and surface cleaning, RF discharges have also been applied to thin film deposition. We report in this paper the main results obtained with several fusion devices on RF conditioning discharges and present conclusions for future devices such as ITER.
Read more1Application of a high-power CO laser in aluminum welding
A multi-kW CO laser system with nearly diffraction limited beam quality has been developed. The performance data are presented. Experiments in laser welding of the aluminum alloy AlMgSil (6082) has been carried out using the CO laser and a commercial industrial carbon- dioxide laser. The welding performance of both laser systems has been compared with results of Nd-YAG laser welding from literature. It has been shown that the penetration depths with the CO laser are higher compared with the results of carbon-dioxide and Nd-YAG laser at the same power level. This is on the one hand a consequence of the better beam quality of the CO laser compared to the Nd-YAG laser and on the other hand the shorter 5 to 5.6 micrometer wavelength compared to the carbon-dioxide laser resulting in a reduced beam-plasma interaction. Owing to the shorter wavelength of the CO laser the absorption of the radiation by laser induced plasma -- one major problem in deep penetration welding with lasers -- is drastically reduced. The aluminum weld seams obtained with the CO laser are very homogeneous and regular at the surface in contrast to the weld seams obtained with the carbon-dioxide laser. The process parameters in CO laser aluminum welding can be changed in a wide range. This is not possible using the carbon-dioxide laser because of the low threshold intensity for a shielding plasma.
Read more1New nozzle for high power CO2 laser welding with Argon as shielding gas
It is known that Helium is the most efficient shielding gas for the high power CO2 laser welding process. The high ionization potential of helium limits the ionization propagation from the metallic plasma plume to the shielding gas. Helium avoids the formation of parasitic plasma in the shielding gas which could absorb the incident laser beam. This phenomenon is known as Bremsstrahlung Inverse absorption. With high CO2 laser power, it is not possible to use argon as shielding gas. The formation of this parasitic plasma depends on the laser features as the power, the power density, the focused spot diameter and the focal length. Indeed, the focal length affects the opening of the focused laser beam and the power density above the metallic plasma plume resulting from the welding process. The higher the power density above the metallic plasma plume is, the easier the parasitic plasma formation in the shielding gas will be.this paper, we present a solution to weld with a high power CO2 laser beam and 100% Argon or other free Helium gases. The solution is suitable up to 12kW CO2 and a 100% Argon flow rates of 35l/min. The results obtained with Argon shielding gas have the same quality of the traditional ones obtained with Helium.It is known that Helium is the most efficient shielding gas for the high power CO2 laser welding process. The high ionization potential of helium limits the ionization propagation from the metallic plasma plume to the shielding gas. Helium avoids the formation of parasitic plasma in the shielding gas which could absorb the incident laser beam. This phenomenon is known as Bremsstrahlung Inverse absorption. With high CO2 laser power, it is not possible to use argon as shielding gas. The formation of this parasitic plasma depends on the laser features as the power, the power density, the focused spot diameter and the focal length. Indeed, the focal length affects the opening of the focused laser beam and the power density above the metallic plasma plume resulting from the welding process. The higher the power density above the metallic plasma plume is, the easier the parasitic plasma formation in the shielding gas will be.this paper, we present a solution to weld with a high power CO2 laser beam and 100% Arg...
Read more6COIL 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.
Read more10Synthesis and characterization of PLZT thin films obtained by pulsed laser deposition
Thin films of Pb1-xLax(Zr0.65Ti0.35)1-x/4O3 with x=0.09 (PLZT 9/65/35) have been grown by pulsed laser deposition (PLD) and by PLD assisted by radio frequency (RF) discharge in oxygen which increases the plasma reactivity and reduces the oxygen vacancies in films and at the film-bottom electrode interface. Significant compositional, structural and dielectric differences have been found among samples grown in the same deposition conditions excepting for RF power. Films grown by RF-assisted PLD have less pyrochlore and are more oriented. For these films dielectric permittivity vs. temperature variation was typical of relaxor ferroelectrics and the temperature of the dielectric maximum was close to that obtained in bulk, but the permittivity value was much lower. This was attributed mainly to the influence of a low permittivity interface layer and to the detrimental effect of pyrochlore phase, still present in small quantities even in the films obtained by RF-PLD. The dielectric behavior of films grown without RF discharge was very different: no dielectric anomaly was observed, only a step increase above 180 °C. Moreover much higher dielectric loss was measured for these films.
Read more5Comparing Study on Formation of Large Discharge Currents in Atmospheric Pulse-Modulated Radio Frequency Discharges
In recent years, pulse-modulation is introduced in atmospheric radio frequency (RF) discharges to further control the discharge operation. In this article, a comparing study is performed by a 1-D fluid model to investigate the formation of large discharge currents (LDCs) in the first RF cycle during the power-on phase in an atmospheric pulse-modulated RF discharge controlled by dielectric barriers. The current–voltage characteristics and helium metastable (He*) distributions show the enhancement of a pulsed voltage on the ignition of RF discharge, which agrees well with the experimental observation. On the other hand, in a dielectric barrier discharge driven by a sinusoidal voltage of 500 MHz, double LDCs are observed in the positive and negative half-cycles, respectively, and the large pulse rise rate of applied voltage essentially influences the distribution of charged particles in the first cycle during the power-on phase. In this study, according to computational data the reverse electric field near the anode contributes greatly to the generation of LDCs in both types of discharge, and the appropriate discharge conditions are suggested to optimize the pulse-modulated RF discharges in applications.
Read more2High Power CO Lasers And Their Application Potential
Comparing the state of development of high power gas lasers for civil applications, it can be seen that the CO2 laser is a well established tool; the CO laser, however, essentially remained a laboratory device. Hence, the question arises whether there will be an advantage to develop high power CO lasers for industrial applications, too. After a brief recapitulation of the typical CO-related properties, to help answering this question, the application potential of the CO laser, will be discussed. There are several wavelength-related advantages of the CO laser like increased absorption depth in glasses and crystals increased focal power density, and reduced plasma shielding. Furthermore, transmissive optical materials have considerably improved values for absorption and damage threshold, and finally power transmission through optical fibers is much more realistic in the near future for the 5 μm spectral range. In contrast to the variety of promising applications is the number of experimentally verified ones. This is due to the fact that only a few lasers are existing in the power range and in the developmental stage to be used for applications. In experiments CO lasers demonstrated advantages in the field of cutting and drilling metals and uranium isotope separation. Lasers in the high power range are developed in Japan, in the Soviet Union and in Germany. The types of lasers investigated in these countries differ from each other by the methods of gas cooling and excitation. Comparisons between Co- and CO2 lasers show that the system efficiencies of CO lasers are slightly higher by a factor of 1.3; the operation costs of CO lasers are reduced by the same factor. Investment and operation costs can be reduced considerably if for the planned application a high focal power density is used. Furthermore, the volumes of CO and CO2 lasers are comparable at present and in the future.
Read more3An experimental study of the plasma parameters of a hybrid low-pressure RF discharge
This paper presents an experimental study of the plasma parameters of a hybrid radio-frequency (RF) discharge, which is a new modification of an RF discharge. The discharge is maintained by both vortex and potential RF electrical fields. To generate a hybrid RF discharge, an RF power input unit is used in the form of a parallel-connected inductor and capacitor coatings. A blocking capacitor is included in the capacitive channel of the discharge. The paper presents data from the study of the influence of power coupled to the plasma, argon pressure, and blocking capacitance on the plasma parameters, i.e., the electron energy distribution, temperature, and density and plasma potential. The role of the capacitive channel in the variations in properties and the characteristics of the discharge are considered.
Read more1Combined electron cyclotron resonance and radio frequency discharges in the TOMAS facility
The experiments carried out in hydrogen at the TOMAS facility show the possibility of controlling plasma parameters such as temperature and electron density in a combined electron cyclotron resonance and radio frequency (ECR+RF) discharge. A maximum plasma density of up to ≈6 × 1016 m−3 and electron temperature of up to 35 eV are observed in the combined ECR+RF discharge. The propagation of RF waves in hydrogen plasma under a weak magnetic field is analyzed. Depending on RF frequency and experimental conditions, such as radial distribution of plasma density and magnetic field, there can be several cases: only the slow wave can propagate, simultaneously slow and fast waves can propagate, or only the fast wave can propagate. The injection of additional RF power into the ECR discharge allows us to change the flux of neutral particles and their distribution function. Even the injection of small RF power of ≈ 0.26 kW relative to microwave power of ≈ 1.7 kW leads to an increase in the hydrogen flux by a factor of ∼2.5. At RF power PRF ≈ 1.57 kW, the H0 flux increases by a factor of ∼9.3. The ability to control the fluxes and energies of particles leaving the plasma volume is important to approach the conditions necessary to study plasma–surface interactions in wall conditioning and fusion edge plasmas.
Read more17Continuous wave near-infrared atomic Xe laser excited by a radio frequency discharge in a slab geometry
Near-infrared atomic Xe laser lines have been generated from an Ar:He:Xe laser gas mixture excited by a radio frequency (rf) discharge in a slab geometry. A maximum continuous wave (cw) output power of 1.5 W (270 W/l) was obtained at an rf frequency of 125 MHz from a gas mixture containing Ar:He:Xe (50:49:1) at a total gas pressure of 90 Torr.
Read more1Characterization of plasma parameters and neutral particles in microwave and radio frequency discharges in the Toroidal Magnetized System.
A characterization of plasma parameters and neutral particle energies and fluxes has been performed for radio frequency and microwave discharges in the Toroidal Magnetized System (TOMAS). A movable triple Langmuir probe was used to study the electron densities and temperatures, and a time-of-flight neutral particle analyzer was used to measure the energy and fluxes of neutral particles, as a function of the total injected power and the antenna frequency used to generate the plasma. The experimental results can provide information on the behavior of neutral particles at low energies in wall conditioning plasmas.
Read more4High-power COIL and YAG laser welding
We have constructed a laser welding system, which enabled high-power laser welding by combining three laser beams of 1 mm wavelength. Its wavelength enables optical silica fibers transmission and the flexible system. The heart of this system consists of a 4 kW and a 6 kW Nd:YAG lasers and a 10 kW Chemical Oxygen-Iodine Laser (COIL). The average power of the combined beam is up to over 20 kW. The effects of various welding parameters were investigated, such as the laser power, pulse modulation, and so on. The 10 kW COIL has a very good beam quality which is 64 mm.mrad. The beam spot diameter is 0.48 mm at the focal point. On the contrary the beam quality of Nd:YAG laser is worse, but it has the function of pulse modulation which the COIL dose not have. As a result of the welding test with the 6 kW Nd:YAG laser, it was clarified that the pulse wave (PW) has good efficiency of deeper penetration at low welding speed. When the combined beam with CW COIL and PW Nd:YAG laser was used, 20 mm penetration on the stainless steel could be achieved at a welding speed of 1 m/min.
Read more34Heuristic method for evaluating COIL performance
A heuristic methodology is described that was developed to evaluate the chemical efficiency of high-power chemical oxygen iodine laser (COIL) devices and its application to the specific evaluation of the U.S. Air Force Phillips Laboratory's RotoCOIL laser. A heuristic equation that forms the basis of this methodology and describes the COIL energy flow, energy losses, and power extraction using measured data, code results, and empirical relations is presented. Using this equation and bounding values for some of its terms, it is shown that for the RotoCOIL performance data the experimentally measured average O 2 ( 1 Δ) yield of 0.40 is nearly 38% below that which would be consistent with the measured extraction power. By relating terms of the heuristic equation to performance of individual components of the COIL system, it is concluded that nearly 50% of the efficiency loss for the RotoCOIL laser derives from oxygen generator and delivery losses, whereas 15% is from nozzle inefficiencies and 11% from resonator losses.
Read more
Copyright 2026 Cactus Communications. All rights reserved.
