EP0389980B1 - High power radiation device - Google Patents

Abstract

In the high-power emitter for UV light, a quartz or glass tube (1) with electrodes (3, 4), arranged in pairs and spaced apart from one another in the circumferential direction forms (lacuna). The tube together with the electrodes is partially embedded in a cast mass (2) and forms a module (6). A multiplicity of these modules can be assembled into any desired emitter geometries. <IMAGE>

Description

The invention relates to a high-power radiator, in particular for ultraviolet light, according to the preamble of claim 1.

The invention relates to a state of the art, such as results from EP-A 254 111 or the older EP-A-385205.

The industrial use of photochemical processes depends heavily on the availability of suitable UV sources. The classic UV lamps deliver low to medium UV intensities at some discrete wavelengths, such as the mercury low-pressure lamps at 185 nm and especially at 254 nm. Really high UV powers can only be obtained from high-pressure lamps (Xe, Hg), which then but distribute their radiation over a larger wavelength range. The new excimer lasers have some new wavelengths for basic photochemical experiments are currently available. for cost reasons for an industrial process probably only suitable in exceptional cases.

In the EP patent application mentioned at the beginning or in the conference paper "New UV and VUV excimer emitters" by U. Kogelschatz and B. Eliasson, distributed at the 10th lecture conference of the Society of German Chemists, Photochemistry Group, in Würzburg (FRG) 18. -20. November 1987, a new excimer radiator is described. This new type of emitter is based on the fact that excimer radiation can also be generated in silent electrical discharges, a type of discharge that is used on a large scale in ozone generation. In the current filaments of this discharge, which exist only for a short time (<1 microsecond), noble gas atoms are excited by electron impact, which react further to excited molecular complexes (excimers). These excimers only live for a few 100 nanoseconds and release their binding energy in the form of UV radiation when they decay.

The structure of such an excimer radiator, up to the power supply, largely corresponds to that of a conventional ozone generator, with the essential difference that at least one of the electrodes and / or dielectric layers delimiting the discharge space is transparent to the radiation generated.

The high-performance radiators mentioned are characterized by high efficiency, economical structure and enable the creation of large area radiators, with the restriction that large-area flat radiators require a rather large technical effort. In contrast, when irradiating flat surfaces with omnidirectional emitters, a not inconsiderable proportion of the radiation is not used due to the shadow effect of the inner electrode.

Starting from the prior art, the invention has for its object to provide a high-performance radiator, in particular for UV or VUV radiation, which is characterized in particular by high efficiency, is economical to manufacture and enables the construction of very large area radiators.

To solve this problem in a high-power radiator of the type mentioned at the outset, it is provided according to the invention that the electrodes are designed as metal strips, metal wires or metal coatings which run in the longitudinal direction of the tube and are spaced apart from one another in the circumferential direction of the tube, one electrode with one pole and the other electrode with the other Pole of the AC power source are connected.

With radiator elements designed in this way, large-area radiators can be modularly constructed, in which any geometries can be composed of identical or similar discharge tubes, each of which is self-contained. The individual elements are electrically contacted on the side on the outside of the tubes, so that light emission is hardly impeded. The degree of utilization of the radiation generated can be improved by partial mirroring on the outside of the tubes.

The advantages of the invention are as follows:
Simple and inexpensive realization of the completed discharge volume possible. Similar basic elements (tubes) for all geometries, large areas can be easily realized with the appropriate number of tubes.
Good stability of the discharge volume when using relatively robust tubes with a small diameter.
Due to the generally large number of self-contained tubes, the failure of individual elements (e.g. due to contamination of the gas or the quartz surface, leaks) is less critical.

The entire arrangement can cover a wide range of wavelengths by using tubes with different gas fillings. You only have to take the (quartz) quality for the individual tubes that is just necessary or optimal for the transmission of the generated radiation. Depending on the desired wavelength spectrum, this can lead to considerable savings in material costs.

The light is coupled out of the tubes at a point that is hardly affected by the discharge. No transparent electrodes are necessary.

Fig.1

Ein erstes Ausführungsbeispiel eines Hochleistungsstrahlers mit einer Vielzahl nebeneinanderliegender kreisrunder Dielektriksrohre im Querschnitt;

Fig.2

eine vereinfachte Draufsicht auf den Strahler nach Fig.1, zur Verdeutlichung der elektrischen Anspeisung;

Fig. 3

eine Ausführungsform eines Flachstrahlers mit auf eine Kante gestellten Dielektrikumsrohren mit Rechteckprofil und gekühlten Elektroden;

Fig.4

eine Ausführungsform eines Flachstrahlers analog Fig.3 jedoch mit auf eine Flachseite gestellten Dielektrikumsrohren mit Rechteckprofil und Drahtelektroden.

In the drawing, embodiments of the invention are shown schematically; in it shows

Fig. 1

A first embodiment of a high-power radiator with a plurality of circular dielectric tubes lying side by side in cross section;

Fig. 2

a simplified plan view of the radiator according to Figure 1, to illustrate the electrical feed;

Fig. 3

an embodiment of a flat radiator with placed on an edge dielectric tubes with a rectangular profile and cooled electrodes;

Fig. 4

an embodiment of a flat radiator analogous to FIG. 3, however, with dielectric tubes with a rectangular profile and wire electrodes placed on a flat side.

In Fig. 1 pipes 1 are made of dielectric material, in particular glass or quartz, about half each in a casting compound 2 made of insulating material, e.g. Silicone rubber, embedded. Each tube 1 is provided with two strip-shaped metallizations 3 and 4 running in the longitudinal direction of the tube and spaced apart from one another in the circumferential direction as electrodes. These consist e.g. made of soft aluminum and at the same time act as reflectors. The metallizations 3, 4 lie entirely within the casting compound 2. The electrical contact is made laterally on the outside of the tubes 1, e.g. by means of cast-in contact elements 5 (FIG. 2) which protrude beyond the tubes 1 in the longitudinal direction of the tube, the contact elements 5 of each electrode 3, 4 being located in each case on the opposite tube end.

Each module 6 consisting of a tube 1 with electrodes 3, 4 as well as contact elements and casting compound is arranged tightly packed on a carrier plate 7. The carrier plate can be cooled directly or indirectly by a coolant which can be passed through cooling bores 8. Another cooling option is the co-casting of cooling tubes 19 which touch the metallizations. As can be seen from the schematic plan view of FIG. 2, the individual radiators are fed from an alternating current source 9, the poles of which are alternately connected to the interconnected contact elements 5 on both pipe ends.

The tubes 1 are closed at both ends. The interior of the tubes, the discharge space 10, is filled with a gas / gas mixture which emits radiation under discharge conditions. The AC power source 9 basically corresponds to those used for feeding ozone generators. It typically delivers an adjustable AC voltage in the order of magnitude of several 100 volts to 20,000 volts at frequencies in the Range of technical alternating current up to a few 1000 kHz - depending on the electrode geometry, pressure in the discharge space and composition of the filling gas.

The filling gas is e.g. Mercury, noble gas, noble gas-metal vapor mixture, noble gas-halogen mixture, optionally using an additional further noble gas, preferably Ar, He, Ne, as a buffer gas.

Depending on the desired spectral composition of the radiation, a substance / substance mixture according to the following table can be used: Filling gas radiation helium 60-100 nm neon 80 - 90 nm argon 107 - 165 nm Argon + fluorine 180-200 nm Argon + chlorine 165-190 nm Argon + krypton + chlorine 165-190, 200-240 nm xenon 160-190 nm nitrogen 337 - 415 nm krypton 124, 140-160 nm Krypton + fluorine 240 - 255 nm Krypton + chlorine 200-240 nm mercury 185, 254, 320-370, 390-420 nm selenium 196, 204, 206 nm deuterium 150-250 nm Xenon + fluorine 340 - 360 nm, 400 - 550 nm Xenon + chlorine 300-320 nm

• Ein Edelgas (Ar, He, Kr, Ne, Xe) oder Hg mit einem Gas bzw. Dampf aus F₂, J₂, Br₂, Cl₂ oder eine Verbindung die in der Entladung ein oder mehrere Atome F, J, Br oder Cl abspaltet;
• ein Edelgas (Ar, He, Kr, Ne, Xe) oder Hg mit O₂ oder einer Verbindung, die in der Entladung ein oder mehrere 0-Atome abspaltet;
• ein Edelgas (Ar, He, Kr, Ne, Xe) mit Hg.

In addition, a whole series of other filling gases are possible:

• A noble gas (Ar, He, Kr, Ne, Xe) or Hg with a gas or vapor from F₂, J₂, Br₂, Cl₂ or a compound that splits off one or more atoms F, J, Br or Cl in the discharge;
• a noble gas (Ar, He, Kr, Ne, Xe) or Hg with O₂ or a compound that splits off one or more 0 atoms in the discharge;
• an inert gas (Ar, He, Kr, Ne, Xe) with Hg.

In the silent discharge that forms, the electron energy distribution can be optimally adjusted by the thickness of the dielectrics and their properties, pressure and / or temperature in the discharge space.

When an alternating voltage is applied between the electrodes 3 and 4, a large number of discharge channels 11 (partial discharges) form in the discharge space 10. These interact with the atoms / molecules of the filling gas, which ultimately leads to UV or VUV radiation.

Instead of dielectric tubes 1 with a circular cross section, glass or quartz tubes with other geometries, for example tubes with a rectangular profile, can also be used. FIG. 3 illustrates a variant with tubes 12 with a square cross section placed on one edge and embedded in casting compound 2 up to the adjacent edge.
In a departure from the embodiment according to FIG. 1, the electrodes 13, 14 are not designed as strip-like metallizations, but rather as sheet-metal strips, which are also cast into the casting compound 2. Of course, this measure can also be taken in the arrangement according to FIG. 1. In addition, cooling pipes 15, 16 are fastened to the sides of the sheet metal strips 13, 14 facing away from the pipes 12, through which a coolant can be carried. If a non-conductive coolant is used, pipes 15, 16 made of metal can also take over the function of the electrodes 13, 14, and separate sheet metal strips 13, 14 are then unnecessary. In this way, the cooling of the radiator modules via the support plate 7, on which the modules 6 are fastened in close proximity to one another, can - but does not have to - be omitted.
A further cooling option, which can also be used in addition, consists in providing cooling channels running in the pipe length direction, for example by co-casting pipes 15a.

In FIG. 4, dielectric tubes 17 made of glass or quartz with a rectangular profile are embedded upright in the casting compound 2. In this variant, a further possibility of the formation of the electrodes is illustrated, namely, wires 18 which are closely coexistent and which are cast into the casting compound 2 and run in the longitudinal direction of the tube. Analogously to FIG. 3, thin metal tubes 19 can be used instead of wires, through which a non-conductive cooling liquid can be passed as illustrated in the right module of Fig.4.

In the embodiments according to FIGS. 3 and 4, the modules 6 are electrically connected to one another and are connected to the alternating current source 9 analogously to FIG. 2.

It goes without saying that in addition to dielectric tubes with a round or rectangular cross-section, those with other cross-sectional shapes, e.g. hexagonal, can be used. The support plate 7 can also be curved in one direction, e.g. Circular arc shape, or the modules are arranged on the inner or outer surface of a tube.

In order to generate UV or VUV light, which covers a broad wavelength spectrum, the tubes of the individual modules 6 can be filled with different gas fillings / gas pressure.

Claims (8)

1. A high-power radiation device, in particular for ultraviolet light, with a discharge chamber(10) which is filled with a filling gas emitting radiation under discharge conditions, the walls of which are formed by a dielectric tube (1; 12; 17) permeable to radiation, which is provided on its surface facing away from the discharge chamber with first and second electrodes (3,4; 13,14; 18), and with an alternating current source (9) to supply the discharge, characterised in that the electrodes are constructed as metal strips (13,14), metal wires (18) or metal coatings (3,4) running in the longitudial direction of the tube and spaced apart from each other in the circumferential direction of the tube, in which one electrode is connected with one pole, and the other electrode is connected with the other pole of the alternating current source (9).
2. A high-power radiation device according to Claim 1, characterised in that the dielectric tube (1; 12; 17) is partially embedded into an electrically insulating casting material (2).
3. A high-power radiation device according to Claim 2, characterised in that in the case of electrodes in strip form (13,14) or in wire form (18), these are placed into the casting material (2) or are cast into it.
4. A high-power radiation device according to Claims 2 or 3, characterised in that cooling channels (15,15a) are embedded in the casting material (2).
5. A high-power radiation device according to Claims 1 to 3, characterised in that cooling devices (15,16;19) are associated with the electrodes (3,4;13,14;18), which are in direct thermal contact with the electrodes.
6. A high-power radiation device according to Claim 4, characterised in that in the case of electrodes in strip form (13,14) the cooling device is constructed as cooling pipes (15,16) connected with the electrode.
7. A high-power radiation device according to Claim 1,2 or 4, characterised in that the electrodes are constructed as cooling channels (15,16;19).
8. A high-power radiation device according to one of Claims 1 to 7, characterised in that a common base plate (7), which is able to be cooled either directly or indirectly, is associated with several radiation devices (6).

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