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Metal Vapour Lasers

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Research and Development of a New Family of High-efficiency Metal Vapor Lasers Pumped by Runaway Electron Beams Generated in a Gas Discharge

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics

Status
3 Approved without Funding

Registration date
21.01.1997

Leading Institute
TsKB of High Energy Lasers "Granat", Russia, Moscow

Collaborators

  • St Andrews University / School of Physics and Astronomy, UK, St Andrews

Project summary

The objectives of the project

The project has to do with research of laser physics basic problems.

The objective of this project is to elaborate of experimental and theoretical foundations of creation of new type of high efficiency discharge lasers. These lasers are pumped by runaway kilovolt (up to a few tens kilovolts) electron beams generating directly in the active medium with the aid of special configuration discharges. Theoretical research and first experimental results of the metal vapor lasers (MVL) pumped by gas discharge of such a type predict significant increase (by 1..2 orders) in the efficiency and specific power of the existing (MVL) and the production of laser action over new lines at atoms, molecules, and ions in ultraviolet, visible and infrared ranges of spectrum. The specific characteristics of such lasers in visible range can reach 1 kW per meter of length of an active zone with physical efficiency 5..6 % [1..3]. As the first step of new laser family creation within the framework of this project the elaboration of MVL infrared range of spectrum is to be carried out.

Technical approach and anticipated results

Metal vapor lasers and, particularly, a copper vapor laser, the most powerful and effective of them, have already a more than 30-year history, and are characterized by a high level of a laser design. The average power of the Cu-laser exceeds 1 Ш. К lot of computer programs have been developed which describe adequately various parameters of lasers. Experimental and theoretical results show that the level of laser output per length (in respect to length of an active zone) of Сu-lasers is close to the ultimate value of 100 W/m [4]. So, essential progress in specific characteristics of the metal vapor lasers can be reached only with the use of principally new method of the active medium excitation, for example, the pumping by electron beams.

It would be ideal design for laser pumped by electron beam (EB) if EB was produced in active volume directly, i.e. at gas density within an accelerating interval corresponding to working pressure of laser mixture. This is possible under conditions of electrons transference in a "runaway" mode, which takes place in the area with rather high reduced intensity of the field, E/P >> 100 V/m. Pa. Runaway electron beams are produced either in very small discharge gaps with grid anode for beam letting out ("open" discharge [5]) or in systems with strong inhomogeneous distribution of electric field in discharge gap (with multypoint cathode, with grid cathode etc.). The greatest efficiency of energy transformation of discharge in EB energy is reached in a so-called "open" discharge configuration, where it reaches (80 - 90 %), and electrons get the energy of 1 - 10 keV [1, 5].

Mathematical simulation discovers [1, 2] that pumping of lasers by kilovolt electron beams increases pumping efficiency considerably in comparison with traditional gas discharge excitation. It takes place due to the part of high energetic electrons in plasma formed by EB is considerable larger than in gas discharge plasma. This let us the bases to hope for production of laser action over new lines at atoms, molecules, and ions and spectral range of effectively function lasers extending to the short wave region. In the present project research and development of PBS- and ECU- vapor lasers (average power up to 10 W with efficiency more than 1 %, working temperature 900-1000° C) pumped by runaway electrons of kilovolt energies are to be carried out. The radioactive spectrum of these lasers (more than 10 various lines) lies within the range 0,7..7 mem (0.723, 1.72, 1.575, 1.587, 1.616, 1.661, 1.689, 1.761, 2.618, 2.660, 4.329, 5.076, 5.291, 6.780 mem). These lasers can find wide application in the systems of ecological control, laser medicine and surgery, communication, as brightness amplifiers for observation faint intensity cosmos objects, in laser chemistry and isotope separation. The powerful lasers can be used in processing of various materials including semiconducting, delicate crystals and diamonds. Investigations of the indicated lasers will be the base for creation of new effective visible and ultraviolet lasers with higher working temperature.

Within the framework of the project the following works will be carried out:


1) The mechanism and conditions for the effective formation of runaway electron beams in special configurations of a gas discharge will be investigated. In the experimental part of the project the main attention will be paid to the research of beam generation efficiency in various discharge configurations and the beam plasma radiation role in the cathode secondary processes, and the stability of the discharge burning throughout a large area. On the basis of the data to be obtained there will be developed an adequate two-dimensional non-stationary physic-mathematical model of the open discharge describing the generation of runaway electron beams.
2) The design of Pb- and Eu-vapor lasers pumped by runaway electrons with average power up to 10 W at the efficiency more than 1 % will be developed. The lasers will be started and their complex researches will be carried out.
3) Complex physicomathematical models of specified lasers including the runaway electron beams formation, beam spatial energy degradation in the active zone, laser kinetics and radiation generation, will be developed.
4) The comparison of calculation and experimental results will be carried out, and the potentialities of lasers pumped by gas discharge, generating the runaway electron beams will be determined.

Execution of the proposed project will be the first significant step to creation of a new generation of effective gas discharge lasers.

The creation of metal vapor lasers pumped by runaway electron beams is new promising direction in laser physics and techniques. Our theoretical researches predicting the considerable progress in MVL characters were printed in 1995 and 1996 years only. As far as we know there are not groups anywhere working at this field now.

Our project is founded on results of experimental works of the end of 80th years of P.A.Bokhan group, theoretical works of our groups, our 20-years experience of research and development of powerful (> 100 W) transverse-discharge Сu-laser, and our experimental test of reception runaway electron beam in open discharge with total current l0kA (duration and pulse repetition rate is 20 ns and 3,5 kHz, cathode square 1200 cm2). The positive feature of the project is combination of experimental researches with fundamental theoretical elaborations.

Potential role of foreign collaborators:

The potential role of foreign collaborators is supposed to be the following:


- participation in completion and extension of the research program, so their own interests may be taken into account;
- they receive from us information about experimental and theoretical results, including current research reports, participate in direct/correspondence discussion of results, and acquaint themselves with our experimental arrangement;
- joint work and joint publications,
- joint commercial utilization of the project results.

References


1. S.V.Arlantsev, В.L.Borovich, V.V.Buchanov, E.I.Molodykh, N.I.Yurchenko, "On the prospects of using runaway electron beams generated in an open discharge for the pumping of metal-vapor lasers", Journal of Russian Laser Research, New York, 1995, v. 16, N 2, p. 99-119.
2. S.V.Arlantsev, В.L.Borovich, V.V.Buchanov, N. I.Yurchenko. "Mn-vapor lasers with pumping by a kilovolt electrons beam. Numerical simulation, comparison with experiments, potential opportunities ", Kvantovaya Electronika (Russian Journal), 1996, v.23, N 11.
3. P.A.Bokhan, E.I.Molodykh. "Output limiting mechanisms and the prospects for metal vapor lasers with average output power above 1 kW/m". Pulsed Metal Vapor Lasers, NATO ASI Series, Kluer academic publishers, 1996, p. 137-148.
4. В.L.Brooch, N. I.Yurchenko. "Physics of transverse-discharge copper vapor lasers." Pulsed Metal Vapor Lasers, NATO ASI Series, Kluer academic publishers, 1996, p. 73-78.
5. P.A.Bokhan, A.R.Sorokin. "Electron beam forming at an "open" discharge: mechanism, properties and his utilization for pumping of middle pressure gas lasers", Journal of technical physics (Russian Journal), 1985, v.55, N 1, p. 88-95.


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