Electron Energy Distribution Functions and Vibrational Excitation Rates in Co2 Laser Mixtures

Meng

Journal of the Chinese Institute of Engineers

et al. 1989

A uniform volumetric discharge was obtained by means of an auxiliary UV preionization in a home-made TEA CO 2 laser. The maximum output pulse energy of this laser system was about 12J per pulse with a pulse duration of 80 ns. The ratio of electric field to neutral particle density (E/N) in this laser was 7.6×10 -16 V cm 2 . The peak power and pulse shape of the laser were studied. The time delay between the predischarge and the maindischarge during the stable operation of this laser system has also been studied. It was observed that the laser was operating with uniform glow discharges when the time delayed between the predischarge and the maindischarge was in the range of 1.0 µs to 6.0 µs. The spark array used as a preionizer for producing the UV radiation in this system is new, simple, durable, and can be easily fabricated.

Section: Discussionmentioning

confidence: 98%

A study of uv preionization pulsed tea CO₂ laser

Meng

Journal of the Chinese Institute of Engineers

et al. 1989

“…Powers as high as 540 W have been measured with typical efficien6ies ranging from 10 to 18 percent. Calculations of electron kinetic processes have been made for similar gas mixtures and discharge conditions [19]. Over the range of pressure encountered, the ratio of E/P remained fairly constant at about 8.8 V/cm -torr.…”

Section: )mentioning

confidence: 99%

Magnetic stabilization of the plasma column in flowing molecular lasers

Buczek¹,

Freiberg²,

Chenausky³

et al. 1971

Proc. IEEE

A technique of magnetically stabilizing the position of the plasma column and the resulting inversion region in lower pressure flowing molecular lasers is described.A transverse magnetic field, mutually perpendicular to the discharge axial electric field and the gas flow velocity, is employed to maintain the electrical discharge column parallel with the optic axis. The magnetic stabilization of the discharge is analyzed in terms of the Lorantz forces and the resulting ambipolar drifts of the plasma. A comparison with magnetically stabilized arcs is presented. Supporting experimental data obtained for pure gases and typical laser gas mixtures are given. The operating characteristics of the cross-field CO, laser which employs a premixed gas flow channeled transvarse to the stabilized discharge t o provide convective gas cooling are discussed. The experimental results of a parametric study on the dependence of gain and power output upon gas flow velocities, magnetic field, gas mixtures, and pressure are presented. The operation of the first premixed CW electrically initiated chemical laser has been achieved using cross-field magnetic discharge stabilization. Preliminary operating characteristics of this chemical laser for the 3-p rotational-vibrational transitions in HF and the 4-p transitions in DF are presented.

“…The fraction of the electron energy transferred to different degrees of freedom of the molecules when they collide depends on the value of E/N, where E is the electric field strength in a discharge. According to [21,22], even in the case of energy distribution of electrons that is optimal for exciting the ν 3 mode, there occurs simultaneous excitation of the ν 1 and ν 2 modes, and also the gas temperature is increased. We think that excitation of the lower laser level 10 0 0 occurs mainly by electron shock, whereas excitation of the upper laser level 00 0 1 is effected by both direct electron shock and transition of the vibrational energy from the excited N 2 molecules.…”

Section: Introductionmentioning

confidence: 98%

Vibrational kinetics of the active media of CW CO2 lasers

Невдах

Ganjali

2005

J Appl Spectrosc

The vibrational kinetics of CW CO 2 lasers has been analyzed within the framework of a temperature model. The necessity of taking into account the coupling of the vibrational modes of the CO 2 molecule in determining the occupation numbers and the store of vibrational energy in individual modes is shown. Expressions that connect vibrational temperatures with the rates of excitation and relaxation of the lower vibrational levels of modes have been obtained. The ratios between the vibrational temperatures on selective excitation of the 00 o 1 level and on excitation of CO 2 molecules in an electric discharge as well as the character of the dependences of vibrational temperatures on the pumping-energy value are discussed. Introduction.The most widespread mathematical model used for calculating the energy and spectral characteristics of continuous wave and pulsed (with pulse duration longer than 10 −6 sec) CO 2 lasers is a temperature model. Physically, the model is based on the "hierarchy" of relaxation times that is typical of the CO 2 molecule under the conditions of an active medium:are the times of rotational-translational, vibrational-vibrational intramode, vibrational-translational, and vibrational-vibrational intramode relaxation, respectively (see, e.g., [1][2][3][4]). Within the framework of the temperature model, the vibrational modes ν 1 , ν 2 , and ν 3 of the CO 2 molecules and ν 4 of the N 2 molecules are considered as simple harmonic oscillators. The distributions of populations over the vibrational levels of each of these modes are described by the Boltzmann distributions with vibrational temperatures T i (i = 1, 2, 3, 4). Knowing the vibrational temperatures, it is possible to determine the population of any vibrational level of the CO 2 and N 2 molecules and also the stores of vibrational energy in their modes. The main drawback of this approach is that the vibrational modes of the CO 2 molecule are considered as independent modes, whereas the vibrational temperatures of these modes are regarded as independent parameters.In the present work, within the framework of the temperature model we analyze the vibrational kinetics of continuously pumped CO 2 lasers taking into account the fact that because of the coupling of the vibrational modes of the CO 2 molecule the vibrational temperatures are not independent parameters.Occupation Numbers of the Vibrational Modes of the CO 2 Molecule. In the temperature model the vibrational temperatures of the CO 2 and N 2 molecules are determined [1-4] from the conditions