A 5 cm single-discharge CO2 laser having high power output

A single-discharge self-sustained CO₂ laser has been constructed with a gap distance of 5 cm. The system has a very simple construction; it produces a very uniform discharge with an output power of 50 Joules per liter for a CO₂ : N₂ : He = 1 : 1 : 3 mixture. The efficiency can be as high as 19%.     

Fine frequency tuning of high power TEA CO2 lasers

A new technique is proposed to fine tune a TEA CO₂ laser within the bandwidth of a single ro-vibrational emission line. A tuning range of ±2 GHz off line center is obtained with an emission bandwidth of about 250 MHz and with a total energy output exceeding 1 joule at line center for the P20 (00°1–10°0) line. This technique can be used for single longitudinal mode operation and has the advantage of being directly scalable to higher power lasers.     

A 3 kW average power tunable TEA CO2 laser

A high average power line-tunable TEA CO₂ laser is described. Average output power up to 3 kW is achieved at repetition rate of 180 Hz. The maximum output power is almost equal among the four spectrum bands of CO₂ laser (the P and R branches of 00°1–10°0 and 00°1–02°0 transition bands). Several special technologies including rotating spark gap switching, PCB (printed circuit board) preionization and zeroth-order grating coupling are employed.     

Characteristics of a wire preionized nitrogen laser with helium as buffer gas

The operation of a small N₂ laser using wire preionization and He as a buffer gas is discussed. The preionization is found to increase the output power and energy by 50% while the addition of helium can increase fourfold the output power.     

Helium-free operations in mini-TEA CO2 lasers

Summary Large helium-free emissions are obtained in two mini-TEA CO₂ lasers, by using always a corona preionization without additives and with a maximum energy density of 900J/l in the discharge. In general, helium-free emissions are more stable, but the best condition in efficiency, energy and peak power is observed always with a small He content added to the laser mixture.

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Riassunto L'uso di una piú efficiente preionizzazione a corona ha permesso l'operazione di un laser a CO₂ senza elio a pressione atmosferica con elevate densità di energia nella scarica (900 J/l) e grande efficienza di conversione dell'energia elettrica in radiazione laser.

     

Short delay time UV preionized TEA CO2 laser operating with binary CO2/H2 and CO2/He gas mixtures

In order to obtain short tail-free output laser pulses from a TEA CO₂ laser, parametric study of the laser operation with CO₂/H₂ and CO₂/He binary gas mixtures containing high CO₂ concentrations was carried out. A small scale UV preionized short delay time TEA CO₂ laser was employed. In terms of the maximum extractable output pulse energy and power, the more conventional CO₂/He gas mixture was found to be inferior in comparison with the CO₂/H₂ mixture proposed here.     

Rapidly tuning miniature TEA CO2 laser – rotating mirror and grating mechanism

In this research, directed toward using differential absorption lidar (DIAL) for measuring concentrations of pollutant gases, a device for rapidly tuning a transversely excited atmospheric-pressure (TEA) CO₂ laser is presented. It is shown that it is possible to utilize a rotating six-sided scanning mirror and a fixed diffraction grating to rapidly switch wavelength over randomly selected lasing transitions in the 9–11 μm region of the spectrum. The scanning mirror and an optical encoder are driven by a hysteresis synchronous motor at a speed of 1500 rpm. A surface-wire-corona preionization was utilized in a cavity. The laser system is highly automated with microprocessor-controlled laser line selection. Single-branch emission at two wavelengths with time interval ⩽10 ms has been obtained from a single cavity TEA CO₂ laser. An accurate line selection has been demonstrated in over 40 transitions at a pulse repetition frequency of up to 100 Hz. The laser energy at first-order couple output was up to 20 mJ per pulse and the pulse width is about 60 ns in an active volume of 36 cm³.     

Preionization of TEA CO2 laser by sliding discharge

TEA CO₂ laser preionization by plasma sheet formed by discharge sliding over a dielectric surface is described. The preionization electron number density in order of 10⁹cm^–3 was measured in the CO₂ N₂ He=113 gas mixture. The plasma sheet was also tested as a main discharge electrode in TEA CO₂ laser.The authors would like to acknowledge with thanks the current interest and the help of P. Gavrilov and V. Krajíek in experiments.     

NOx generation in laser-produced plasma in air as a function of dissipated energy

An experimental study on the production of NO_x as a function of dissipated energy in laser-produced plasma in air is presented. A plasma was produced by focusing a (60–180) mJ, 5 ns, 532 nm pulse from a Q-switched Nd:YAG laser. The results show that for laser energy in the range of 13–99 mJ the laser plasma generates 6.7×10¹⁶ NO_x molecules per joule and 4.6×10¹⁶ NO molecules per joule. An order of magnitude estimate of the NO and NO_x production per unit volume of heated gas based on a simple model show that the NO_x and NO production efficiency in air are about 3×10²² and 2×10²² molecules J⁻¹ m⁻³.     

Characterization of a Br(2P1/2)–CO2(1001-1000) transfer laser driven by photolysis of iodine monobromide

2 laser operating on the 10⁰1-10⁰0 transition at λ=4.3 μm and pumped by E –V energy transfer from Br(²P_1/2) has been demonstrated. The dynamics and performance of this device were characterized by observing the time-resolved stimulated emission and the steady-state spontaneous side fluorescence after photolysis of IBr or Br₂ by a frequency-doubled Nd:YAG laser or Ar⁺ laser, respectively. Although the E –V excitation kinetics are favorable, rapid vibrational relaxation limits laser action to CO₂ pressures of less than 1 Torr. Numerical modeling of laser pulse shapes and the dependence on IBr and CO₂ pressure and photolysis energy establish a relatively high gain of 0.33%/cm, a CO₂-pressure-dependent optical loss of 0.04–0.06%/cm, and an efficiency of 2×10^-5 4.3-μm-laser photons per incident photolysis photon. The CO₂ fluorescence after photolysis of a fixed Br₂/CO₂ gas mixture decreases as a function of photolysis time by about 30%/h, indicating the photolytic production of an important quencher. Received: 23 June 1997/Revised version: 23 September 1997     

High pressure X-ray preionized TEMA-CO2 laser

The construction of a high-pressure (up to 20 atm) transversely excited CO₂ laser using transverse X-ray preionization is described. High pressure operation was found to be greatly improved in comparison to UV-preionized systems. Homogeneous discharges have been achieved in the pressure range 5–20 atm, yielding a specific laser output in the order of 35 J/l.     

The “SKATE” CO2 Gigawatt Laser for a Laser-Plasma Generator of Ions and Nuclei

A set-up of the CO₂ SKATE and its output characteristics are described. The system is based on a self-sustained gas discharge module with x-ray preionization that ensures reliability and stable repetition rate operation at 1 Hz for a long time. Measurement of the initial electron density in the discharge volume produced by an x-ray gun is presented for different gases and their mixtures, which is of independent interest for some applications of x-ray preionization. Data on measurements of the low-intensity signal gain and laser parameters for a free-running generator configuration are presented as well as long-term operation characteristics. This laser system has been used as a CO₂ generator with gigawatt peak intensity and high spatial–temporal characteristics. In particular, the laser can be used as a driver for a source of multicharged ions in contrast to the laboratory prototypes previously investigated.     

Parametric study of a UV preionized CO2 laser

Small signal gain measurements of a uv preionized TEA CO₂ laser system are described. It is shown that the relative timing of preionization with respect to the main discharge determines the amount of electrical energy that can be deposited in the gas prior to arc formation.     

Miniature high-repetition-rate TEA CO2 laser with surface-wire-corona preionization

In this article, an experimental study of a miniature, sealed-off, high-repetition-rate transversely excited atmospheric-pressure (TEA) CO₂ laser with a kind of surface-wire-corona preionization (SWCP) is described. We have utilized an SWCP consisting of SiO₂ dielectric tube and a fine wire strained and attached to the dielectric surface. A BN ceramic material, which has an extremely low coefficient of thermal expansion of about 5 × 10⁻⁷/°C was employed as a supporter of the resonator. A measurement on emission spectra of SWCP has been reported. By applying SWCP to the TEA CO₂ laser, efficient laser operation at an overall efficiency of 9.8% with an output energy of 150 mJ has been achieved from a small discharge volume of 25 cm³ with an active length of 230 mm. At the pulse repetition frequency of 60 Hz, the TEM₀₀ mode of laser beam with pulse width of 60 ns was obtained.     

High power,high efficiency optically pumped NH3 lasers

A simple and efficient NH₃ laser was tuned over more than 70 vibrational band transitions between 10.08 and 14.14 m. The active medium was a dilute mixture of ammonia in argon and was optically pumped by the 9R(30) transition of a pulsed TEA-CO₂ laser. Output energies greater than 1 J per pulse were observed on several of the strongest lines. In a non-selective cavity an energy conversion efficiency of greater than 35% was obtained with a maximum output energy of 4.6J. Optically pumped NH₃ is shown to be a flexible and efficient system for the downconversion of CO₂ radiation.     

New environmentally attractive separation technology for flue gas mixture

ABSTRACT

Separation of gaseous mixtures produced from any process plant can be a major issue for the industry. In comparison to other separation techniques available, hydrate formation can be an appropriate choice in terms of fuel efficiency and degree of separation. In this work, a three-stage process was designed to capture CO₂ from a hypothetical flue gas mixture (comprising 15?mol% CO_2?+?85?mol% N₂). For the hydrate based CO₂ capture process, a detailed analysis was carried out covering the material and energy balance, energy integration and economic analysis. The results show that, at steady state, 91% of the CO₂ in the flue gas can be recovered, resulting into two streams: Stream-A (94?mol% CO₂?+?6?mol% N₂) and Stream-B (1.5?mol% CO₂?+?98.5?mol% N₂). Per 100?mol of the flue gas feed, 3.9?MW of energy is required to achieve such degree of separation. This amount was reduced to 2.4?MW after energy integration was applied to the process. Overall, the process can help in reducing CO₂ emission via flue gas because of the huge difference in the carbon foot print of its energy requirement (500?g CO₂ per kWh) and the amount of CO₂ captured by the process (2190?g CO₂ per kWh).     

Initiation of a volume discharge in an elevated-pressure gaseous mixture of CO2 lasers

Initiation of a volume discharge in the gaseous mixture of CO₂ lasers at above-atmospheric pressures for a discharge gap 5 cm long is considered. It is shown that preionization by soft X rays allows initiation of the volume discharge when ratio E/p (p = 5 atm) is below a static breakdown value.     

Graphite gasification in high-temperature gas flows containing H<Subscript>2</Subscript>O and CO<Subscript>2</Subscript>

The rates of graphite gasification in interaction with high-temperature gas flows were compared. Carbon dioxide and a mixture of water vapor and argon taken in a 1:1 molar ratio were used as reagents. The reactor was a tube furnace; its temperature was varied from 1250 to 1400 K. The rates of graphite gasification in CO₂ and water vapor-argon mixture flows were approximately equal at 1250–1300 K, whereas, at 1350–1400 K, the water vapor-argon mixture exhibited higher reactivity than CO₂. The data obtained were approximated by Arrhenius dependences; the activation energy was found to be 153 kJ/mol for CO₂ and 248 kJ/mol for H₂O-Ar.     

AC-chopper application for CW CO2 laser

A microprocessor-based algorithm was developed to control the power supply to a CO₂ laser using an AC-chopper method. This system was connected directly to a CO₂ laser tube without the need for a dc-dc converter or the storage capacitance of a multilevel circuit. The typical CO₂ laser power supply system had a full-bridge series resonant inverter or voltage multiplier. AC-to-AC converter schemes using zero voltage switching (ZVS) can be used efficiently and economically for low and medium power applications.This paper reports the performance characteristics of a symmetrical AC-chopper technology that can maintain the quality of the ac output of a CO₂ laser tube, regardless of the amount of switching loss. The laser was operated to an output power, maximum system efficiency total gas mixture of 37.2 W, 92%, and CO₂:N₂:He=1:9:15, respectively. The laser system, AC-chopper power supply and its operation were examined.     

Dynamics and correlated performance of a photo-triggered discharge-pumped HF laser using SF6 with hydrogen or ethane

3 , has been performed in Ne/SF₆/H₂ and Ne/SF₆/C₂H₆ mixtures. Parameters involved have been the storage line capacitance and the circuit inductance, the capacitors charging voltage, the RH-molecule type and partial pressure, and the X-ray dose for the preionization. High laser performance has been achieved with C₂H₆: an output energy up to 3 J corresponding to a specific energy of 9.6 J/l at an efficiency of 4.7%, which strengthens the advantage of the photo-triggering technique to energize high-power HF lasers. However the optimum performance achieved with H₂, 5.75 J/l and 3.5%, are lower. It is shown, through a time-resolved study of the electrical discharge and spatial dynamics correlated to laser power and energy measurements, that discharge instabilities are responsible for the poor laser performance of the mixture with H₂. These instabilities, which lead to arc development, are characteristics of the discharge in Ne/SF₆. It is demonstrated for the first time that addition of a heavy hydrocarbon, such as C₂H₆, to that mixture induces the discharge stabilization so that the laser emission arises in a homogeneous active medium. This effect allows us to achieve better laser performance than with H₂. Received: 17 March 1998/Revised version: 13 July 1998