FR2884043A1 - RADIOFREQUENCY-POWERED LIGHT SOURCE FOR PROCESSING SUBSTANCES AND METHOD FOR USING SAME - Google Patents

Abstract

The light source (S) comprises at least one plasma enclosure (1) having a transparent wall (2) to the light (L) and containing a low pressure gas. The enclosure (1) is arranged annularly around a channel (3) for supplying the substance intended to be irradiated. The source (S) comprises a radiofrequency generator (9) creating, via at least one antenna (4), a radiofrequency wave in the enclosure (1). The source (S) comprises at least one permanent magnet (6) for creating a static magnetic field so as to cause inside the chamber (1) a cyclotron resonance of electrons. The source (S) comprises a microwave cavity constituted by an annular resonance cage (5) opaque to the radiofrequency wave and completely enveloping the plasma enclosure (1). The antenna (4) is entirely arranged inside the resonance cage (5). The light source (S) may comprise fast fixing means for connecting the light source (S) to a distribution point of a fluid network.

Description

2884043 1

  FIELD OF THE INVENTION The invention relates to a light source, powered by radiofrequency, for the treatment of substances by visible and ultraviolet light, comprising at least one embodiment of the invention. a plasma enclosure having a light-transparent wall and containing a low-pressure gas, the enclosure being annularly disposed around a supply channel of the substance to be irradiated, the source comprising a generator generating , via at least one antenna, a radiofrequency wave in the chamber, the source comprising a microwave cavity for the electromagnetic coupling between said gas and the radio frequency wave, the source comprising magnetic means making it possible to create a static magnetic field so as to cause inside the enclosure a cyclotronic resonance of ctrons.

  STATE OF THE ART Low pressure and high pressure lamps with electrodes present various problems. Indeed, the power can not be modulated, the life is very limited and the dimensions of the lamp must be increased to increase the light flow.

  JP7263160 discloses a light source having a microwave power supply and a cavity containing electrodeless tubes. The light source further comprises permanent magnets assembled to form a U, the tubes being arranged symmetrically with respect to the U-shaped permanent magnets. US3911318 discloses a method and apparatus for producing a UV and visible electromagnetic radiation of high power. The device is powered by a generator creating a microwave or radiofrequency field inside a silica plasma enclosure allowing the UV radiation to escape. The gas pressure in the chamber is sufficient to support the excitation of a plasma by microwave. The apparatus comprises Helmholz coils creating inside the enclosure a static magnetic field. The radio frequency is greater than or equal to the cyclotron resonance frequency of electrons.

  In a first embodiment of the apparatus of US3911318, the generator and two Helmholz coils are arranged with respect to the enclosure so as to allow light emission to the outside. A mesh screen serves as a waveguide to confine radiofrequency radiation, while light can be emitted to the outside of the device. The mesh screen may be formed on an inner face of a shield made of a light-transmitting material.

  US3911318 also discloses an apparatus for photochemical applications comprising a plasma annular enclosure. A substance intended to be irradiated passes inside the annular enclosure and is thus surrounded by the plasma emitting the ultraviolet radiation. The enclosure is disposed within a microwave chamber. The substance to be irradiated is fed through a tube entering and exiting into the microwave chamber by microwaveable input and output. In order to limit microwave leakage through these inlets and outlets, metal pipes surround the tube with the substance to be irradiated. However, even if the length of the pipes is significantly greater than their diameter, the microwave radiation leaks can exceed the acceptable limits in terms of the safety of people.

  The microwave power is injected into the microwave chamber at two ends of the chamber. The apparatus comprises four coils of Helmholz. The outer walls of the annular enclosure may comprise, on their outer surface, a coating reflecting the UV light. The coating may also be disposed on the inner surface of the microwave chamber. The apparatus for photochemical applications described in US3911318 is bulky and presents risks for people.

  On the other hand, there are other conventional high pressure light sources which have the disadvantage of heating the irradiated substances.

  OBJECT OF THE INVENTION The object of the invention is to overcome these disadvantages and, in particular, to provide a light source for the treatment of substances, in particular photochemical and / or photobiological, compact and secure. In addition, the object of the invention is to increase the energy efficiency of the light source and, especially for the sterilization of water, to increase the sterilization efficiency, while improving its compactness.

  According to the invention, this object is achieved by the fact that the microwave cavity is constituted by an annular resonance cage opaque to the radiofrequency wave and completely enveloping the plasma chamber, the antenna being entirely arranged inside. of the resonance cage, said magnetic means being constituted by at least one permanent magnet.

  According to a particular embodiment of the invention, the light source comprises fast fixing means for connecting the light source to a distribution point of a fluid network.

  The radiofrequency generator can be placed at a distance from the resonance chamber and connected to the resonance chamber via a coaxial cable o of radiofrequency transmission.

  According to a development of the invention, the light source comprises a plurality of speakers arranged around the supply channel.

  According to a preferred embodiment, the resonance chamber and the enclosure are formed by a single sealed container that is opaque to the radiofrequency wave, the receptacle having a wall transparent to the light arranged opposite the supply channel and the walls. reflecting and opaque to the light.

  According to another development of the invention, the light source comprises means for controlling the radiofrequency power and / or the pressure of the gas and / or the temperature of the source at a target light intensity.

  In addition, the light source may comprise means for modulating the power of the radiofrequency wave in the enclosure.

  The invention also aims at a method of using at least one light source, having a predetermined light spectrum and intensity, the spectrum being controlled by the maximum power of the radiofrequency wave in the chamber and the Intensity is controlled by the average temporal power of the radio frequency wave in the enclosure.

Brief description of the drawings

  Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention given by way of non-limiting example and represented in the accompanying drawings, in which: FIGS. 1 and 2 show in section, respectively along the axis BB and along the axis AA, a particular embodiment of the light source according to the invention.

  Figures 3 and 4 show in section, respectively along the axis B-B and along the axis A-A, another particular embodiment of the light source 20 according to the invention.

  Figures 5 and 6 show in section, respectively along the axis B-B and along the axis A-A, a third particular embodiment of the light source according to the invention.

  Figure 7 illustrates, in side view, the use of a particular embodiment of the light source according to the invention.

  Figures 8 and 9 illustrate, in section, two variants of Figure 1.

  Figures 10 and 11 illustrate, in section, two variants of Figure 2.

  FIG. 12 schematically illustrates a particular embodiment of a system comprising three light sources according to the invention.

  FIG. 13 represents, as a function of time, three particular embodiments of the radiofrequency power supplying the light source according to the invention.

  Description of particular embodiments

  FIGS. 1 and 2 show a radiofrequency-fed source S for the treatment of substances by visible and ultraviolet light L. The light source S may, for example, serve as a purifier, a chemical reactor, for the production of ozone and for the disinfection or sterilization of water or air. The term radio frequency applies to electromagnetic waves having a frequency below 3000 GHz and, in particular, to microwaves.

  The light source S comprises a plasma chamber 1 containing any low-pressure gas, typically between 10-4 and 10mbar, and having a transparent wall 2 to the light L. The chamber 1 is arranged annularly around a channel 3 for supplying the substance intended to be irradiated. The source S comprises a radiofrequency generator 9 connected to an antenna 4 and creating, via the antenna 4, a radiofrequency wave in the enclosure 1. The source S has a microwave cavity for the electromagnetic coupling between said gas and the radio frequency wave. The microwave cavity is constituted by an annular resonance cage 5 opaque to the radiofrequency wave. The cage 5 completely envelops the plasma chamber 1. The cage 5 constitutes a shielding of the radio frequency.

  The enclosure 1 and the cage 5 may, for example, each have a toroidal shape, the torus of the enclosure 1 being completely enveloped by the torus of the cage 5.

  The antenna 4 is fully disposed within the resonance cage 5. Thus, the supply channel 3 and the environment of the light source S are completely shielded by the cage 5 against the radio frequency wave. In FIGS. 1 and 2, the feed channel 3 is, for example, constituted by a tube inserted into the central recess of the annular resonance cage 5.

  In Figures 1 and 2, the source comprises four permanent magnets 6 for creating a static magnetic field, so as to cause inside the chamber 1 a cyclotron resonance of electrons.

  The shielding of the supply channel 3 against the radiofrequency wave makes it possible to protect the user from the luminous source S, the persons close to the source S and the environment of the source S in a general manner. In addition, the shielding makes it possible to avoid the interaction of the substance intended to be irradiated with the radiofrequency wave. In particular, the interaction of the radiofrequency wave with a liquid such as water, for example, is to be avoided in order to avoid the losses of the radiofrequency wave and to optimize the efficiency of the radiofrequency wave inside the radio frequency wave. the resonance cage 5. Indeed, the water strongly absorbs the microwaves, which increases the temperature of the water. Thus, the interaction of the radiofrequency wave with the water can have a second annoying effect, especially when the purpose of the UV treatment is the sterilization of the water. Indeed, the heating of the water favors the contamination of the water. This negative effect is then also eliminated by the shielded source S according to the invention.

  The light source S also makes it possible to treat heated substances, for example water having a temperature greater than 40 C, which is not possible with conventional low-pressure light sources, which only operate at low temperatures. . Thanks to the cyclotron resonance principle of electrons, the light source allows an instantaneous ignition, for example during a millisecond. This is particularly crucial for continuous use such as, for example, for on-demand water sterilization, where the source must, in principle, be turned on only when a tap is open. Indeed, conventional light sources o low pressure must be lit continuously because of the significant ignition time and life limitations induced by the re-ignitions.

  As shown in FIGS. 3 and 4, the permanent magnets 6 can also be disposed inside the enclosure 1. In FIGS. 3 and 4, the feed channel 3 is, for example, constituted by a tube integral with the central recess of the annular resonance cage 5.

  As shown in FIGS. 5 and 6, the permanent magnets 6 can also be arranged outside the resonance cage 5. Moreover, only one permanent magnet 6 that is sufficiently strong can be used.

  Unlike Helmholz coils, the permanent magnet (s) 6 can easily be placed inside the enclosure 1 or at least inside the resonance cage 5. Unlike the permanent magnet 6, the Helmholz coils could not be placed inside the resonance cage because of the incompatibility of the coils and the radio frequency wave. However, the minimum dimensions of the resonance cage 5 are determined by the resonance frequency. For example, for a resonance frequency of 2.45 GHz, the resonance cage 5 should have minimum dimensions of between 6 cm and 10 cm. The use of a permanent magnet 6, which can be integrated inside the cage 5, then makes it possible to reduce the dimensions of the whole of the light source S to the dimensions of the resonance cage 5, whereas the Helmholz coils would be added to the dimensions of the resonance cage. In addition, Helmholz coils require additional electrical connections. This improves the compactness of the luminous source S, which is particularly necessary for the case of a portable light source or for integrating the source S into other devices, such as medical devices, for example a seat of dentist.

  In the particular embodiment shown in Figure 7, the light source is used for the sterilization of water. For this use, the source comprises a fast fixing device 7 for connecting the light source S to a distribution point 8 of a fluid network. The quick fastening device 7 may be a screwing or detent device and is preferably a flexible seal adaptable to any valve. In FIG. 7, the radiofrequency generator 9 of the light source S is disposed at a distance from the resonance cage 5 and connected to the resonance cage 5 via a coaxial radiofrequency transmission cable 10. The light source S according to the invention makes it possible in particular to irradiate the last drop leaving the tap, that is to say the source S. The light source shown in Figure 8 is also intended for use for sterilization water, for example in a shower mode. In FIG. 8, the luminous source S comprises a set of two walls 11a and 11b enabling the shielding of any light L towards the outside of the source S. The two walls 11a and 11b comprise orifices 12a and 12b offset from each other, so that the light L through the orifices (12b) of one of the walls (11b) is blocked by the other of the walls (11a).

  While the central walls 2a of the chamber 1, arranged opposite the supply channel 3, must be transparent to the light L, the outer walls 2b can be opaque. The resonance cage 5 comprises central walls 13a arranged facing the supply channel 3, transparent to the light L, as shown in FIG. 8. However, the outer walls 13b of the cage 5 may be opaque. If the outer walls 2b of the enclosure 1 and the outer walls 13b of the cage 5 are transparent to the light L, the light source must comprise additional walls, shields or any shielding ensuring that no light L is s' escapes to the outside of the bright S source, in order to protect people. Preferably, a coating reflecting the visible and UV light is disposed on the inner surface of the outer walls 2b of the enclosure 1, to reflect the light to the channel 3 supply.

  In FIG. 9, the resonance cage 5 and the enclosure 1 are formed by a single sealed container 14 that is opaque to the radiofrequency wave. The container 14 has a light-transparent wall 15 arranged facing the supply channel 3 and the light-reflecting and light-opaque outer walls 16. The container 14 is, for example, rendered opaque to the radiofrequency wave by a conductive mesh deposited on the walls of the container 14.

  As also shown in Figure 9, the channel 3 for supplying the light source is constituted by a tube 17 removable and transparent to light. Instead of performing, for example, a descaling of a supply channel 3 which is integral with the source S, the tube 17 can simply be replaced by a clean tube. Descaling can also be carried out conventionally by a brush.

  In FIG. 10, the light source S comprises a plurality of independent speakers 1, in particular six in FIG. 10, represented in section (1 a, 1 b, 1c, 1d, 1 e and 1f). The enclosures 1 are arranged around the supply channel 3. The enclosures 1 preferably have a cylindrical tubular shape and are arranged along the supply channel 3. Each enclosure 1 is associated with a permanent magnet 6 creating a magnetic field in the corresponding enclosure 1. The antenna 4 creates a radiofrequency electromagnetic wave in the resonance cage 5 and, thus, in the six sealed enclosures 1. The wall forming the supply channel 3 in FIG. 10 must be opaque to the radiofrequency wave.

  In the particular embodiment shown in FIG. 11, the enclosure 1 has a shape of a hollow cylinder, of annular section, and the light source S comprises a plurality of permanent magnets 6 and a plurality of antennas 4, arranged alternately at the periphery of the enclosure 1. In FIG. 11, eight permanent magnets 6 are disposed at the periphery of the enclosure 1, inside the resonance cage 5, so that the zones cyclotron resonance of the electrons are distributed substantially uniformly in the hollow cylinder of the chamber 1.

  In FIG. 12, the light source comprises a control unit 18 making it possible to control the radiofrequency power at a desired light intensity. Thus, the radiofrequency power is set to the desired light intensity. For this, the light intensity is measured, for example by means of a sensor or a light detector disposed in the channel 3, and the radiofrequency power is increased when the intensity measured is less than the intensity. setpoint and decreased in the opposite case. The radiofrequency power is then adjusted according to the intensity measured. It is also possible to control the pressure of the gas, and / or the temperature of the source S, to the set light intensity and to adjust the gas pressure in order to adjust the light intensity. The temperature is preferably adjusted by cooling the source S, for example by means of a fan or a water cooling circuit.

  Thus, when the light intensity decreases gradually during the use of the light source, the intensity can be systematically corrected by increasing the radiofrequency power or the gas pressure. Thus, aging effects of the source S can be compensated.

  In Figure 12 is shown a system of four light sources S1, S2, S3 and S4 arranged in series. It is thus possible to irradiate the substance passing through the supply channels 3 with different lights, that is to say having different spectra and / or intensities.

  The control unit 18 also makes it possible to modulate the power P of the radiofrequency wave injected into the enclosure 1, for example in the form of pulses of any shape and frequency. These pulses are, preferably, rectangular as shown in FIG. 13. The three curves P1, P2 and P3 correspond to the same average power Pmn and, thus, to the same average light intensity. Indeed, according to the curve P1 a predetermined continuous power is injected into the chamber 1. The continuous power (P1) is equal to the average power Pmn. The average power Pmn injected is preferably between 10 and 1000W. The curve P2 represents rectangular pulses having a maximum power Pmax2, for example with a frequency of 50 Hz, and having a duty cycle such that the average power Pmn injected into the chamber 1 is the same as that of the curve P1. Curve P3 has a frequency that is twice as low as that of curve P2 (in the example 50 Hz) and a maximum power P max of rectangular pulses twice as high as that of curve P2. Thus, the average power Pmn curves P2 and P3 is effectively equal. However, since the maximum powers of the curves P1, P2 and P3 are different, the curves P1, P2 and P3 correspond to different light spectra.

  Thus, according to a method of using at least one light source S according to the invention, having a predetermined light spectrum and intensity, the spectrum is controlled by the maximum power of the radiofrequency wave in the chamber 1 and the intensity is controlled by the average temporal power of the radiofrequency wave in the chamber 1. When several light sources are used as in the system shown in FIG. 12, the spectra and intensities of the different light sources S1, S2, S3 and S4 can be controlled via the maximum power of the average temporal power of the radiofrequency wave injected into the speakers 1 corresponding to the light sources S1, S2, S3 and S4.

  The light source provides radiation in the visible spectrum and in the UV spectrum, corresponding to emission lines of the atoms and ions of the gas. The 254 nm line of the un-ionized mercury atom can be obtained with low maximum powers. A 254nm light exhibits photo-biological effects, in particular a germicidal effect. When the radiofrequency power injected is increased, it is also possible to obtain the emission lines of the ionized atoms having wavelengths of less than 200 nm, for example the lines of the ionized mercury once, having wavelengths of 164.9 nm. and 194.2nm. A light with these wavelengths has photochemical effects and makes it possible, for example, to generate hydroxyl free radicals by irradiation with a brightness of the order of 120 mJ / cm 2 for a single given wavelength.

  Thus, by switching from a power modulation such as that represented by curve P2, in FIG. 13, to a power modulation such as that represented by curve P3, in FIG. 13, it is possible to switch from a dominated spectrum by the line at 254 nm to a spectrum also showing strong emission at wavelengths below 200 nm. The choice of gas and the pressure and / or the temperature in the chamber 1 makes it possible to adapt the spectrum of the source S to its use, in particular to the desired ultraviolet regime.

  On the other hand, an ultraviolet light of 195 nm makes it possible, in known manner, to generate ozone, while 254 nm ultraviolet light makes it possible to eliminate ozone. Thus, it is possible to envisage a fluidic system, for example an ozone-disinfected water circuit, comprising a first light source S1 for generating ozone and a second light source S2 disposed downstream of the first source S2, to remove ozone, so that the ozone does not come out of the system. Only the part of the circuit arranged between the two sources S1 and S2 then comprises ozone, without presenting a danger for the user.

Claims (15)

claims   1. Light source (S), powered by radiofrequency, for visible and ultraviolet light (L) treatment of substances, comprising at least one plasma enclosure (1) having a wall (2, 2a) transparent to light (L) and containing a low-pressure gas, the enclosure (1) being arranged annularly around a channel (3) for supplying the substance intended to be irradiated, the source (S) comprising a radiofrequency generator (9) creating, by means of at least one antenna (4), a radiofrequency wave in the enclosure (1), the source (S) having a microwave cavity for the electromagnetic coupling between said gas and the wave radiofrequency, the source (S) having magnetic means for creating a static magnetic field so as to cause inside the chamber (1) a cyclotron resonance of electrons, source characterized in that the cavity micro- wave is constituted by a cage (5) of r an annular signal opaque to the radiofrequency wave and completely enveloping the plasma enclosure (1), the antenna (4) being entirely arranged inside the resonance cage (5), said magnetic means being constituted by at least a permanent magnet (6).   2. Light source according to claim 1, characterized in that it comprises quick fixing means (7) for connecting the light source (S) to a distribution point (8) of a fluid network.   3. Light source according to claim 2, characterized in that the quick fastening means (7) comprise a flexible seal adaptable to any valve.   4. Light source according to any one of claims 1 to 3, characterized in that the radiofrequency generator (9) is arranged at a distance from the resonance cage (5) and connected to the resonance cage (5) by the intermediate of a coaxial cable (10) of radiofrequency transmission.   5. Light source according to any one of claims 1 to 4, characterized in that it comprises a plurality of enclosures (la, lb, 1c, 1d, 1 e and 1f) arranged around the channel (3) of feed.   6. Light source according to claim 5, characterized in that the enclosures (la, lb, 1c, 1d, 1 e and 1f) have a tubular shape and are arranged along the channel (3) of supply.   7. Light source according to any one of claims 1 to 6, characterized in that it comprises a plurality of permanent magnets (6) and a plurality of antennas (4) disposed at the periphery of the enclosure ( 1).   8. Light source according to any one of claims 1 to 6, characterized in that the permanent magnet (6) is disposed within the enclosure (1).   9. Light source according to any one of claims 1 to 4, characterized in that the cage (5) of resonance and the chamber (1) are formed by a single container (14) sealed and opaque to the radio frequency wave , the container (14) having a wall (15) transparent to the light (L) arranged facing the channel (3) supply and the outer walls (16) reflective and opaque to the light (L).   10. Light source according to any one of claims 1 to 9, characterized in that it comprises shielding means (2b, 11, 12, 16) of any light to the outside of the source (S).   11. Light source according to any one of claims 1 to 10, characterized in that the channel (3) of supply is constituted by a removable tube (17) transparent to the light (L).   12. Light source according to any one of claims 1 to 11, characterized in that it comprises servo-control means (18), at a desired light intensity, the radiofrequency power and / or the pressure of the gas. and / or the temperature of the source (S).   13. Light source according to any one of claims 1 to 12, characterized in that it comprises means (18) for modulating the power (P) of the radiofrequency wave in the enclosure (1).   14. Light source according to claim 13, characterized in that the modulation means (18) of the power generate pulses.   A method of using at least one light source according to any of claims 13 and 14, having a predetermined light spectrum and intensity, characterized in that the spectrum is controlled by the maximum power (Pmax) of the radio frequency wave in the chamber (1) and the intensity is controlled by the mean power (Pmn) of the temporal wave of the radiofrequency wave in the chamber (1).