Coherent light generators – Particular active media – Gas
Patent
1990-05-14
1992-05-12
Epps, Georgia Y.
Coherent light generators
Particular active media
Gas
372 55, 372 61, H01S 322
Patent
active
051134063
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a very high temperature heating device. Its field of application covers numerous industrial activities requiring temperatures which can reach 2500.degree. C. It is more particularly applicable to maintaining at high temperature the metal in a metal vapour laser or for the degassing of certain materials.
DISCUSSION OF THE RELATED ART
In practice, it is very difficult to obtain high temperatures (above 1000.degree. C.). The main known devices use the Joule effect, induction or heating by electric impulsive or d.c. discharges.
The example of maintaining at high temperature a metal with a view to its vaporization in a metal vapour laser illustrates particularly well the problem caused by high temperature heating. An enclosure contains balls of the metal to be vaporized in the atmosphere of a buffer gas. In order to prepare its vaporization, the balls are raised to a temperature close to 1000.degree. C.
Certain known devices use a heating jacket for enveloping the enclosure containing the metal balls. This jacket is traversed by a current and therefore gives off heat through the Joule effect. It is connected to a d.c. power supply supplying very low voltages of approximately 20V.
Apart from the fact that these devices require a sophisticated d.c. supply, the heating jacket is fragile and has a limited life.
In order to heat the metal prior to its vaporization, other known devices directly use impulsive electric discharges permitting the laser effect. These impulsive discharges are obtained from a thyratron trigger system connected to a d.c. power supply.
This heating by electric pulses can be replaced by d.c. electric discharge heating. The said discharge also requires a d.c. supply able to supply voltages of about 10,000V. This supply must make it possible to maintain an electric discharge in the buffer gas at a stable mean value, whilst the impedance of the plasma formed by the buffer gas varies. In addition, half the power supplied by the power supply is lost in the ballast resistors needed for the satisfactory operation of the device.
It is clear that no matter which known means is used for heating the metal in a metal vapour laser, d.c. power supplies are necessary.
Heating by impulsive discharges calls on an element already incorporated in to the laser, namely the thyratron trigger system. However, this system is fragile and only operates for a limited number of hours. It is therefore prejudicial to use it for purposes other than for obtaining the laser effect. This device is not suitable for heating and for maintaining the metal at the appropriate temperature.
All the known devices for the heating of the metal in a copper vapour laser consequently suffer from maintanance problems and certain elements of the d.c. supplies and the thyratron must be frequently replaced. It is expensive to use them in equipment operating on an industrial site for heating purposes.
Another type of problem is caused by high temperature heating for degassing a material. In a known manner use is made of furnaces operating by the Joule effect. The elements to be degassed are incorporated in to an intermediate enclosure under vacuum. Heating is indirect, the heat propagating from the outside towards the inside of the enclosure. This configuration is not favourable, much energy being wasted before reaching the desired temperature.
Induction furnaces constitute a second type of known device permitting degassing. However, in this case, the degassing of the inductors occurring at high temperature pollutes the materials to be treated. It is clear that high temperature heating is a difficult operation and in particular causes problems varying depending upon the individual situation.
SUMMARY OF THE INVENTION
The object of the invention is to supply a very high temperature heating device without requiring a high voltage d.c supply and which can easily be adapted to different environments.
More specifically, the invention relates to a heating device comprising a refractory, ins
REFERENCES:
patent: 4956845 (1990-09-01), Otto et al.
Journal of Physics E/Scientific Insturments, vol. 21, No. 4, Apr. 1988, IOP Publishing Ltd. J. K. Mittal et al.: "Design and Performance of a 20 Watt Copper Vapour Laser", pp. 388-392.
Applied Physics B/Photophysics & Laser Chemistry, vol. B44, No. 1, Sep. 1987, Springer-Verlag, Z. G. Huang et al.: "A Gold-Vapor Laser Using Ne-H.sub.2 as Buffer Gas", pp. 57-59.
Soviet Journal of Quantum Electronics, vol. 7, No. 12, Dec. 1978, American Institute of Physics, H. Kneipp et al.: "Discharge-heated Copper Vapor Laser", pp. 1454-1455.
Commissariat a l''Energie Atomique
Epps Georgia Y.
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