Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Plasma generating
Patent
1998-08-14
1999-09-07
Bettendorf, Justin P.
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Plasma generating
356316, 21912148, H05H 130, H05H 132
Patent
active
059491930
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a procedure and to a device for forming a plasma.
Elementary analyses of gas or aerosol samples are currently performed by subjecting a sample gas flow to a high temperature using external energy. Generally the sample gas is mixed with a gas that easily transforms into plasma, e.g. argon, helium or nitrogen, which may also be a component of the gas mixture under analysis. When the sample gas becomes sufficiently hot, the electrons in the in atoms of the elements become excited, and the wavelength of the light quantum or photon produced when the electrons are de-excited is characteristic of each element and its electron ring. By examining the light quanta, it is possible to determine the elements and their amounts contained in the sample.
As is known, the external energy can be produced using various systems. Previously known is an induction heater, which uses magnetic flux to transfer energy into the gas to be heated. A problem with the use of magnetic flux is how to "ignite" the gas, i.e. how to achieve a sufficient degree or ionization to induce the plasma state of the gas. A small gas quantity cannot receive a sufficient amount of energy from the magnetic flux, and this leads to the need for large apparatus using a high volume of gas flow. On the other hand, if small amounts of gas are used, the magnetic field has to be generated using a very high frequency, typically a frequency of several gigahertz. Conventionally, this problem is solved by using a spark between two electrodes to "ignite" the gas. The spark is created in the area where plasma is to be developed and it is extinguished after a plasma flame has been set up. This is not an automatic system, because if the plasma decays in consequence of an external disturbance, such as a power failure, gas supply failure or the like, it has to be ignited again with a spark.
Another prior-art method is to use only a high-voltage spark to produce a plasma. In this case, a gas is ionized using an electric spark until a breakdown occurs and the gas is converted into plasma. However, the spark is not extinguished after a plasma has been generated, but the spark is used to transfer the energy required by the plasma to the gas. As the required high power is transferred by means of a spark, the spark discharge is very unstable and difficult to control, causing serious; disturbances in the analysis of sample gases.
SUMMARY OF THE INVENTION
The object of the percent invention is to eliminate the drawbacks mentioned above.
A specific object of the present invention is to produce a procedure and a device for forming a plasma which allow a stable and controlled plasma to be generated with flue gas samplets for the purpose of determining the percentages of elements present in the flue gas samples.
Another object of the present invention is to produce a plasma forming device that works on a continuous principle, i.e. when the plasma reverts into gas, the device acts automatically so that the gas is again converted into plasma.
A further object of the present invention is to produce a procedure and a device which enable a plasma to be generated and maintained with a power demand significantly lower than in prior-art devices.
As for the features characteristic of the invention, reference is made to the claims.
In the procedure of the invention for forming a plasma, a magnetic field is set up in a plasma forming space, a spark discharge is produced in the plasma forming space and a gas flow is passed into the plasma forming space against the magnetic field. Preferably the gas flow is applied in a direction perpendicular to the magnetic field, permitting the most effective transfer of electric energy from the magnetic field to the gas. According to the invention, plasma is generated in the plasma forming; space by means of the spark discharge and maintained by means of the magnetic field and spark discharge, in practice, however, the situation is such that when the power of the magnetic field is sufficient, th
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Impedance Laser Spectroscopy in a Small RF-Excited Neon Discharge, Froake et al. Mikrochimica Acta, Springer-Vertag 113, pp. 349-355 (1994).
Optogalvanic Spectroscopy with rf Discharge, Optics Communication, vol. 38, No. 5,6, pp. 364-368, Sep. 1, 1981, Suzuki.
Characterization of Near-Infrared Atomic Emission from a Radio-Frequency Plasma for Selective Detection in Capillary Gas Chromatography, R. J. Skelton, Jr. et al., Applied Spectroscopy, vol. 44, No. 5, 1990, pp. 853-857.
Asikainen Matti
Roine Johannes
Bettendorf Justin P.
Valtion teknillinen tutkimuskeskus
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