RU2560931C1 - Gas-discharge radiation source - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: gas-discharge radiation source with barrier discharge excitation includes a dielectric cylindrical flask with a gaseous medium, on the outer surface of which there are cylindrical electrodes which form a discharge gap in the flask, behind which, along an optical axis, there is a diaphragm with the next exit window for outputting radiation, located at a distance sufficient for concentrating radiation on the optical axis. Such an arrangement of components simplifies the design of the flask and enables to avoid the use of expensive materials when making the diaphragm.

EFFECT: easier ignition and longer service life of the working window and the device overall.

2 cl, 1 dwg

Description

The invention relates to gas-discharge radiation sources, in particular to barrier discharge lamps, and can be used in devices for optical and analytical studies where ultraviolet and vacuum ultraviolet radiation are necessary, for example, when calibrating spectral equipment, for photoionization of gaseous media.

Sources for photoionization of gaseous media and spectral equipment are well known [1, 2]. Their efficiency and reliability are determined by a number of factors: the stability of the discharge ignition; bulb cooling mode; the life of the working mixture; composition and pressure of the working mixture; the design of the flask and electrodes. Such sources are filled with hydrogen or deuterium, inert gases or mixtures of inert gases and halogens and are excited by glow, arc and high-frequency discharges.

Hydrogen and deuterium radiation sources are known (for example, a VMF-25, DNM-15, DNM-N-20, DNM-100 lamp) emitting in the ultraviolet (UV) and vacuum ultraviolet (VUV) spectral ranges, consisting of a bulb, an electrode system and an output radiation window made of a material transparent to the working radiation wavelengths. To protect the window from damage by discharge, the window is placed at a distance from the discharge gap, sufficient to prevent the flow of charged particles. This allows you to increase the life of the device.

A common drawback of all these devices is the continuous deterioration of the transparency of the output windows under the influence of VUV radiation. As a result, the radiation intensity of the lamps in the region of 200-300 nm is continuously decreasing.

A known radiation source [3], in which to combat this effect, it is proposed to introduce mercury into the gas medium of the lamp, but this complicates the technology of preparing the device for soldering. Another drawback: when the gas medium is excited by arc and glow discharges, the contact of the electrodes with the working mixture leads to a gradual degradation of the medium and in some cases (this depends on the medium and pressure) to a change in the spectral composition of the radiation. In addition, these lamps are well suited for illumination with wide apertures, but are inconvenient if you want to transmit UV radiation through the light guide from the exit window.

There are devices in which, to ensure miniaturization while increasing the stability and intensity of radiation, as well as efficiently transferring plasma radiation into the fiber, several refractory inserts with constriction are inserted into the discharge region [4], which act as diaphragms. The insert increases the radiation intensity in a narrow channel formed by the diaphragms. As a result, the radiation concentrated on the axis is efficiently supplied to the fiber.

The closest to the invention in terms of technical nature and the technical result achieved is a radiation source [5], which includes a cylindrical flask with a gaseous medium formed by a diaphragm, dielectric ends transparent at the working wavelength, two electrodes placed externally at the ends. At the same time, holes were made along the axis of the end electrodes for outputting radiation. The diaphragm can be made of refractory material and serves to concentrate radiation on the axis of the bulb. When a pulse voltage is applied to the electrodes with frequencies from 100 kHz to 500 MHz, a barrier discharge is ignited in the bulb. Since the electrodes are separated from the working medium, this ensures the best purity of the spectra and the service life of the mixture. This source also provides efficient transmission of radiation from a narrow discharge channel to the fiber.

The disadvantages of the source include: 1) the comparative complexity in its manufacture (since the bulb is not cast, it requires sophisticated technology for gluing it with dielectric ends and electrodes); 2) the need to use expensive materials for the diaphragm (aluminum nitride, thorium oxide, diamond, tungsten); 3) the narrowing of the discharge channel leads to an increase in the values of the ignition voltage and combustion of the discharge, which reduces the efficiency of the conversion of energy from the power source to radiation in comparison with devices without a diaphragm; 4) heating the diaphragm increases the risk of depressurization of the flask, which imposes additional cooling requirements.

The objective of the invention is to simplify the design and increase the efficiency of the device while providing a narrow aperture of the output radiation for transmission to the fiber.

This problem is achieved by the fact that in a gas-discharge source of radiation, which includes a cylindrical dielectric flask with a gas medium, on the outer surface of which there are electrodes, a diaphragm and an exit dielectric window at the end, transparent at the working wavelengths, according to the technical solution, the electrodes are cylindrical, forming there is a discharge gap in the bulb, behind which a diaphragm is placed along the optical axis, followed by an exit window for outputting radiation located at a distance sufficient I'm concentrating the radiation on the optical axis.

In addition, the diaphragm can be made not only in the form of a ring, but the function of the diaphragm can be performed by local indentation of the side wall of the bulb to the size of the diaphragm or by narrowing the bulb and moving it into the tube.

The indicated arrangement of elements: 1) simplifies the design of the flask, since the flask is made as a whole, without gluing; 2) allows you to abandon the use of expensive materials in the manufacture of the diaphragm; 3) due to the refusal to narrow the discharge channel, it simplifies ignition, reduces the burning voltage, and this, in turn, increases the efficiency of energy conversion from the power source to radiation, allows working at lower frequencies, not in the MHz range, i.e. simplifies the requirements for protection against interference from a radiation source; 4) provides protection of the exit window from both charged particles and VUV radiation from the near-wall regions, which does not make a useful contribution to the formation of the narrow aperture necessary for the radiation source to join with the optical fiber, which together increases the service life of the working window and the device as a whole .

In FIG. 1 (a, b, c) is a schematic representation of the claimed radiation source. The device consists of a cylindrical flask 1 filled with a working medium made of dielectric material, cylindrical electrodes 2 and 3 forming a discharge gap 4. The diaphragm 5 is located outside the discharge gap 4 and the electrodes. The exit window 6 is located behind the diaphragm. The diaphragm can be made in the form of a ring insert (Fig. 1a), or local indentation of the side wall of the flask to the size of the diaphragm (Fig. 1b), or in the form of a narrowing of the flask and its transition into a tube with a diameter of the diaphragm (Fig. 1c).

The device operates as follows. When the source is turned on and a pulse voltage is applied to the electrodes 2 and 3 in the discharge gap 4, a barrier discharge is ignited. The radiation is output to the output window 6. The diaphragm 5 simultaneously reduces the aperture of the output radiation, which facilitates its output to the external fiber, and protects the output window 6 from the flows of charged particles from the discharge and VUV radiation from the wall regions (especially in the region of electrode 3). Unlike the prototype, the device is much simpler constructively. Since the diaphragm is outside the discharge gap, ignition is simplified, the burning voltage is reduced, and this, in turn, increases the efficiency of energy conversion from the power source to radiation. The proposed arrangement of the electrodes allows to increase the area of the dielectric wall, which is being charged from the impulse voltage applied to the electrodes. This, firstly, leads to the fact that it is possible to provide the necessary energy input into the medium at lower repetition frequencies of voltage pulses, without using the MHz band. This means that it simplifies the requirements for protection from interference caused by the radiation source. Secondly, it is possible to increase the pressure of the working medium and increase the radiation intensity.

Thus, the radiation source is simpler than the known devices in design, provides an aperture of the output radiation that is convenient for transmitting radiation to an external fiber, increases the efficiency of energy conversion from the power source to radiation, and allows to increase the working medium life.

It is advisable to use the proposed source for working media in the emission spectrum of which there is VUV radiation.

Information sources

1. Seidel A.N., Schreider E.Ya. Vacuum spectroscopy and its application. The main edition of the physical and mathematical literature of the Nauka publishing house, 1976. 432 p.

2. Light sources for optical and analytical instrumentation // Heraeus Noblelight GmbH. HNG B181E / 01.10.wsp.

3. Shishatskaya L.P., Lisitsyn V.M. Hydrogen spectral lamp // Patent SU 469166. Published on 04/30/1975. Bulletin No. 16.

4. Herter B. Electrode-less discharge lamp // Patent application US 2002/0017876. Published on January 10, 2001. 4. Smolka E., Dietz K.-J., Schilling F., Schnabl A., Yerter B.

5. Low-pressure discharge lamp containing a partition therein // Patent US 5814951. Published December 19, 1996.

Claims (2)

1. A gas-discharge source of radiation with excitation by a barrier discharge, which includes a cylindrical dielectric flask with a gas medium, on the outer surface of which there are electrodes, a diaphragm and an exit dielectric window at the end, transparent at operating wavelengths, characterized in that the electrodes are cylindrical, forming there is a discharge gap in the flask, behind which a diaphragm is placed along the optical axis, followed by an exit window for outputting radiation, located at a distance sufficient for concentration radiation on the optical axis. 2. A gas-discharge radiation source according to claim 1, characterized in that the diaphragm is made in the form of either a local indentation of the side wall of the flask or a transition of the flask into the tube.