FIELD OF THE INVENTION

The invention relates to a radiation generating system and to a method for treating a gas or a surface.

BACKGROUND OF THE INVENTION

Discharge lamps are known in the art. US 6,633,109, for instance, describes a dielectric barrier discharge-driven light source comprising a first and second dielectric barrier which enclose a gas, an inner electrode coupled to an outside portion of said first dielectric barrier, and an outer electrode coupled to an outside portion of said second dielectric barrier where said outer electrode is comprised of an electrically conductive fluid. The first and second dielectric barriers have a circular shape.

SUMMARY OF THE INVENTION

UV light has been used for disinfection for over 100 years. Wavelengths between about 190 nm and 300 nm may be strongly absorbed by nucleic acids, which may result in defects in an organism’s genome. This may be desired for killing bacteria and viruses, but may also have undesired side effects for humans. Therefore the selection of wavelength of radiation, intensity of radiation and duration of irradiation may be limited in environments where people may reside such as offices, public transport, cinema’s, restaurants, shops, etc., thus limiting the disinfection capacity. Especially in such environments, additional measures of disinfection may be advantageous to prevent the spread of bacteria and viruses such as influenza or novel (corona) viruses like COVID-19, SARS and MERS.

It appears desirable to produce systems, that provide alternative ways for air treatment, such as disinfection. Further, existing systems for disinfection may not easily be implemented in existing infrastructure, such as in existing buildings like offices, hospitality areas, etc. and/or may not easily be able to serve larger spaces. This may again increase the risk of contamination. Further, incorporation in HVAC systems may not lead to desirable effects and appears to be relatively complex. Further, existing systems may not be efficient, or may be relatively bulky, and may also not easily be incorporated in functional devices, such as e.g. luminaires. Other disinfection systems may use one or more anti-microbial and/or anti -viral means to disinfect a space or an object. Examples of such means may be chemical agents which may raise concerns. For instance, the chemical agents may also be harmful for people and pets.

In embodiments, the disinfecting light, may especially comprise ultraviolet (UV) radiation (and/or optionally violet radiation), i.e., the light may comprise a wavelength selected from the ultraviolet wavelength range (and/or optionally the violet wavelength range). However, other wavelengths are herein not excluded. The ultraviolet wavelength range is defined as light in a wavelength range from 100 to 380 nm and can be divided into different types of UV light / UV wavelength ranges (Table 1). Different UV wavelengths of radiation may have different properties and thus may have different compatibility with human presence and may have different effects when used for disinfection (Table 1). Table 1 : Properties of different types of UV wavelength light

Each UV type / wavelength range may have different benefits and/or drawbacks. Relevant aspects may be (relative) sterilization effectiveness, safety (regarding radiation), and ozone production (as result of its radiation). Depending on an application a specific type of UV light or a specific combination of UV light types may be selected and provides superior performance over other types of UV light. UV-A may be (relatively) safe and may kill bacteria, but may be less effective in killing viruses. UV-B may be (relatively) safe when a low dose (i.e. low exposure time and/or low intensity) is used, may kill bacteria, and may be moderately effective in killing viruses. UV-B may also have the additional benefit that it can be used effectively in the production of vitamin D in a skin of a person or animal. Near UV-C may be relatively unsafe, but may effectively kill bacteria and viruses. Far UV may also be effective in killing bacteria and viruses, but may be (relatively to other UV-C wavelength ranges) (rather) safe. Far-UV light may generate some ozone which may be harmful for human beings and animals. Extreme UV-C may also be effective in killing bacteria and viruses, but may be relatively unsafe. Extreme UV-C may generate ozone which may be undesired when exposed to human beings or animals. In some applications ozone may be desired and may contribute to disinfection, but then its shielding from humans and animals may be desired. Hence, in the table “+” for ozone production especially implies that ozone is produced which may be useful for disinfection applications, but may be harmful for humans / animals when they are exposed to it. Hence, in many applications this “+” may actually be undesired while in others, it may be desired.

The present invention focusses, amongst others, on KrCl excimer discharge lamps. Such lamps may especially emit at a wavelength of about 222 nm, which may, as indicated above, be relatively safe and be relatively efficient in reducing e.g. the virus load. The 222 nm peak may have a relatively narrow band width. In addition to the about 222 nm emission, there may be a second (weaker) KrCl* peak at around 235 nm which may have a broader bandwidth. Further, there may be emission at about 258 nm. Prior art solutions may have as disadvantage a relatively high emission of undesired wavelengths, such as at about 258 nm (chlorine molecular radiation), and/or a relatively low efficiency.

Hence, it is an aspect of the invention to provide an alternative radiation generating system, which preferably further at least partly obviates one or more of above- described drawbacks. The present invention may have as object to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

In a first aspect, the invention provides a radiation generating system comprising an excimer lamp. Especially, the excimer lamp comprises a discharge vessel and electrodes functionally coupled to the discharge vessel. Further, especially the discharge vessel contains a gas composition (“discharge vessel filling” or “filling”). In embodiments, a total gas pressure P of the gas composition may be selected from the range of 50-500 mbar. Yet further, in embodiments a CI2 gas partial pressure pCF of the gas composition may be selected from the range of 0.5-3 mbar. Yet further, in embodiments a Ne/Kr partial pressure ratio R- _Ne,Kr of the gas composition may be selected from the range of 0.5-20, such as especially selected from the range of 0.5-10, such as selected from the range of 0.5-5.

Further, in embodiments the gas composition may comprise a Kr partial pressure rk, selected from the range of at least 15 mbar, especially over 15 mbar. Further, in embodiments the gas composition may (also) comprise at least 33% Ne. In embodiments, the gas composition may comply with these conditions at about 20 °C. Therefore, in specific embodiments the invention provides a radiation generating system comprising an excimer lamp, wherein the excimer lamp comprises a discharge vessel, wherein the discharge vessel contains a gas composition, which gas composition may comply with the following conditions (at about 20 °C): (a) a total gas pressure P may be selected from the range of 50-500 mbar; (b) a CI2 gas partial pressure pcu may be selected from the range of 0.5-3 mbar; (c) a Ne/Kr partial pressure ratio R. _Ne,Kr may be selected from the range of 0.5-20, especially selected from the range of 0.5-5; (d) a Kr partial pressure pKr may be selected from the range of over 15 mbar; and (e) at least 33% Ne. The radiation generating system is configured to provide pulsed potential differences to the electrodes selected from the range of 3.5-7.5 kV, wherein the pulsed potential differences have a pulse width selected from the range of 0.25-5 ps, and wherein a pulse frequency is selected from the range of 0.5-200 kHz.

With the present system, it may be possible to provide relatively efficiently KrCl excimer radiation at about 222 nm. Further, it appears to be possible to tune between a relatively high performance, wherein also relatively more radiation at other wavelengths, such as about 258 nm may be available (which may optionally be optically filtered out), as well as modes wherein the contribution of radiation at other wavelengths, such a as about 258 nm, may be relatively low. Basically, it appears that the lower the total pressure and the higher the Ne/Kr partial pressure ratio R.Ne,Kr, the higher the performance may be, and the higher the total pressure and the lower the Ne/Kr partial pressure ratio R.Ne,Kr, the lower the relative contribution of the about 258 nm radiation may be. In this way, a lamp design may be provided which may be tuned for specific applications (especially in dependence of the gas composition). The relatively high performance range may e.g. allow a solution in combination with an optical filter or application in situations where humans can be shielded from the radiation. The low about 258 nm radiation solution may be useful as no optical filter may be necessary; such optical filter may (also) reduce the intensity of the about 222 nm peak and may add significant costs to the system. Further an intermediate range may also be of interest, as in an intermediate range the performance may be relatively high, and the about 258 nm radiation may still be relatively low. Especially, the term “performance” may amongst others refer to efficiency and/or output.

As indicated above, the invention provides in embodiments a radiation generating system. The radiation generating system at least comprises an excimer lamp. The radiation generating system may also comprise (or may be functionally coupled to) a control system to control the excimer lamp, especially its operation. The control system may comprise an electrical ballast. Further embodiments in relation to controlling the excimer lamp are described below.

Especially, the excimer lamp is a dielectric barrier discharge (DBD) lamp. Dielectric barrier discharges are a mercury free source of UV radiation. The use of halogens like bromine and chlorine may enable the generation of UV in the range of about 200-230 nm. As indicated above, this radiation can inactivate harmful viruses by destroying their DNA/RNA, and/or inactivate other parts of the virus proteins. Their wavelength is substantially long enough to prevent the generation of substantial amounts of ozone and substantially short enough not the reach the living skin cells or the cornea of humans possibly present when the UV source is operational.

Dielectric barrier based radiation lamps are known in the art, and are for instance described in US2010/0164410; U. Kogelschatz, Dielectric-Barrier Discharges:

Their History, Discharge Physics, and Industrial Applications. Plasma Chemistry and Plasma Processing 23, 1-46, https://doi.Org/10.1023/A:1022470901385; WO 2006/006139; and R. Brandenburg, Dielectric barrier discharges: progress on plasma sources and on the understanding of regimes and single filaments, Plasma Sources Science and Technology,

Vol. 26, No. 5, 1-29, including corrigendum, which four disclosures are herein incorporated by reference.

Especially, dielectric-barrier discharge (DBD) is the electrical discharge between two electrodes separated by an insulating dielectric barrier. DBD devices can be made in many configurations, typically planar, using parallel plates separated by a dielectric or cylindrical, using coaxial plates with a dielectric tube between them. Other shapes may also be possible.

The basic principle of these lamps may be the generation and emission of radiation by means of a dielectric barrier discharge. Usually, at least one of the two electrodes of such a lamp is located outside the discharge volume. In embodiments, both electrodes of the lamp are located outside the discharge volume. The discharge volume comprises a discharge gas, wherein the energy supply may be accomplished by capacitive coupling through the wall(s) of the discharge vessel (discharge envelope) into the discharge volume, in order to initiate within this volume the gas discharge and the excitation and emission of radiation. Generally, such dielectric barrier discharge lamps may be used as an alternative to conventional mercury based discharge lamps in a wide area of applications, where a radiation of a certain wavelength has to be generated for a variety of purposes. Some applications are for example the generation of ultraviolet (UV) radiation with wavelengths of between about 170 nm and about 380 nm for industrial purposes such as waste water treatment, disinfection of gases and fluids, especially of drinking water, dichlorination or production of ultra-pure water, activation and cleaning of surfaces, curing of lacquers, inks or paints, ozone generation, or for liquid crystal display (LCD) backlighting or photocopiers and others. Furthermore, dielectric barrier discharge lamps are of increasing importance especially as a source for generating and/or emitting high intensity and high power ultraviolet (UV) radiation in a narrow and well defined spectral range with high efficiency and high radiation intensity. WO 2006/006139 (incorporated herein by reference), for instance, describes a dielectric barrier discharge lamp comprising a discharge gap being at least partly formed and/or surrounded by at least an inner wall and an outer wall, wherein at least one of the walls is a dielectric wall and at least one of the walls has an at least partly transparent part, a filling located inside the discharge gap, at least a first electrical contacting means for contacting the outer wall and a second electrical contacting means for contacting the inner wall, and at least one multifunctional means which is arranged adjacent to the discharge gap and which on the one hand serves as an improved and optimized ignition aid, especially for initial ignition or ignition after a long pause, and on the other hand serves at least as guiding means for easily arranging two walls towards each other, thereby forming an optimized discharge gap especially for coaxial dielectric barrier discharge lamps. In embodiments, the dielectric barrier discharge lamp may comprise a discharge volume which is delimited by a first and a second wall, wherein (during operation) both walls are exposed to different electrical potentials by means of a power supply for exciting a gas discharge within the discharge volume. In other embodiments, the dielectric barrier discharge lamp may comprise a discharge volume which is delimited by essentially a single wall, wherein (during operation) different parts of the wall are exposed to different electrical potentials by means of a power supply for exciting a gas discharge within the discharge volume. Hence, especially the (excimer) lamp is of the dielectric barrier discharge lamp type.

The excimer lamp comprises a discharge vessel. Especially, in embodiments the discharge lamp (more especially the discharge vessel) may have an (essentially) axial design. Therefore, in embodiments the discharge vessel may have a cylindrical design. The electrodes may be configured external of the cylinder (see further also below).

First, some embodiments in relation to the gas compositions are discussed.

The gas composition may comprise Ch, Ne and Kr. Other components may also be possible, but especially at least 90 %, even more especially at least 95% of the gas composition consists of Ch, Ne and Kr. Even more especially, 98% or more of the gas composition consists Ch, Ne and Kr. Other components that could be available may e.g. be one or more of Ar, Br2, N2, or ¾, such as one or more of Ar and N2. A composition consisting of essentially Ch, Ne and Kr appeared to provide the best results in terms of efficiency and desired emission. The combination of Kr and Ch may especially provide the desired radiation of about 222 nm.

The total gas pressure (herein also indicated with “P”) in the discharge vessel may be about 40-1000 mbar, such as about 50-650 mbar. Amongst others based on simulations, the total gas pressure may especially be selected from the range of at least about 50 mbar and/or at maximum about 500 mbar. Hence, especially the total gas pressure may be selected from the range of 50-500 mbar, such as at least 100 mbar. Here, the total gas pressure especially refers to the gas pressure in the discharge vessel at ambient temperature (and (thus) not in an operational mode), especially at about 24°C.

It appears desirable that with a total gas pressure in the range of about 40-1000 mbar, especially in the range of about 50-650 mbar, even more especially in the range of about 50-500 mbar, the gas composition may comprise at least about 0.5 mbar Ch (partial pressure). At higher total pressures (within the afore-mentioned ranges of the total pressure) the amount of chlorine (here referring to Ch) may be larger than at lower total pressures, and at lower total pressures the amount of chlorine may be lower than at higher total pressures. In general, the chlorine partial pressure is not higher than about 4 mbar, even more especially not higher than 3.5 mbar. Especially, the chlorine partial pressure may be at maximum about 3 mbar. Hence, especially in embodiments the Ch gas partial pressure pcu may be selected from the range of 0.5-3 mbar. Ch gas partial pressures pcu outside these ranges may lead to a reduction in output and efficiency. Especially, this partial pressure refers to ambient temperature (and (thus) not in an operational mode), especially at about 24°C. Partial pressures are herein also indicated with “p”.

Further, it appears desirable that with a total gas pressure in the range of about 40-1000 mbar, especially in the range of about 50-650 mbar, even more especially in the range of about 50-500 mbar, the Kr partial pressure rk, may be selected from the range of over 10 mbar, even more especially at least about 15 mbar, such as at least about 16.5 mbar. A too low or too high Kr partial pressure may lead to performance issues. Hence, Kr gas partial pressures rk, outside these indicated ranges may lead to a reduction in output and/or efficiency. At higher total pressures within the herein indicated total pressure ranges, the amount (i.e. partial pressure) of Kr may be larger than at lower total pressures, and at lower total pressures within the herein indicated total pressure ranges the amount of Kr may be lower than at higher total pressures. In general, the Kr partial pressure is not higher than about 67% of the total pressure, such as not higher than about 64% of the total pressure. Especially, the Kr partial pressure may be at maximum about 50% of the total pressure. Especially, these partial pressures refer to ambient temperature (and (thus) not in an operational mode), especially at about 20°C.

Further, it may be useful to have a lower chlorine partial pressure at higher Kr partial pressures and a higher chlorine partial pressure at lower Kr partial pressure.

Further, it appears useful when there is a substantial presence of neon (also referred to as Ne) in the gas composition. Especially, the gas composition comprises at least 25, such as at least 30% neon. Even more especially, the gas composition comprises at least 33% neon in the composition.

Further, it appears that within specific Ne/Kr partial pressure ratios R. _Ne,Kr the relatively high performance and/or relatively low 258 nm intensity may be obtained, or that operation may be easier than outside the ratio range, such as in terms of voltage, frequency, startup, etc. A relatively high Ne/Kr partial pressure ratio R. _Ne,Kr may provide a relatively low about 258 nm contribution. However, at a too high partial pressure ratio R. _Ne,Kr performance (especially efficiency) may start to decrease. Hence, especially the partial pressure ratio R- _Ne.Kr is not larger than about 20, such as not larger than 10, like not larger than about 6, especially not larger than about 5. At too small partial pressure ratio R.Ne,Kr, however, also the performance may start to decrease. Hence, especially the partial pressure ratio R. _Ne,Kr may not be smaller than about 0.5. In specific embodiments for every total pressure selected in the herein indicated total pressure ranges, such as in the total pressure range of 50-500 mbar, R-Ne.Kr is at least 0.5. In specific embodiments the Ne/Kr partial pressure ratio R. _Ne,Kr may be selected from the range of 1-10, especially not larger than 6, like selected from the range of 1-5. Even more especially, the Ne/Kr partial pressure ratio R. _Ne,Kr may be selected from the range of 1.5-4.5, such as 1.5-4. With these Ne/Kr partial pressure ratios, simulations and tests were executed which gave relatively high efficiencies.

In yet other embodiments, however, the Ne/Kr partial pressure ratio may be over 5, such as in the range of 5-20, like up to about, such as selected from the range of 5-10.

Hence, in specific embodiments the discharge vessel may contain a gas composition, which gas composition may comply with the following conditions, especially at about 20 °C: (a) a total gas pressure P may be selected from the range of 50-500 mbar; (b) a CE gas partial pressure pen may be selected from the range of 0.5-3 mbar; (c) a Ne/Kr partial pressure ratio R. _Ne,Kr may be selected from the range of 0.5-20; (d) a Kr partial pressure pKr may be selected from the range of over 15 mbar; and (e) at least 33% Ne.

Here below, some further embodiments are described.

As can be derived from the above, especially R. _Ne,Kr is at least 0.5.

It appears that especially at lower total pressures and/or at higher Ne/Kr partial pressure ratios a relatively high performance can be achieved.

Hence, in specific embodiments the Ne/Kr partial pressure ratio R. _Ne,Kr may comply with the formula R _NC.KI -³(0.01 *P/mbar)- 1 , and wherein for total gas pressures P below 100 may apply that R. _Ne,Kr is at least 0.5. Even more especially, the Ne/Kr partial pressure ratio R. _Ne,Kr may comply with the formula R _NC.KI -³(0.0 18*P/mbar)-2 2, and for a total gas pressures P below 150 may apply that R. _Ne,Kr is at least 0.5. In yet further specific embodiments the Ne/Kr partial pressure ratio R. _Ne,Kr may comply with the formula R-Ne. _KI ³(0.0225 *P/mbar)-2 875, and for a total gas pressures P below 150 may apply that P- _Ne.Kr is at least 0.5. Yet further, in specific embodiments R _Nc.Ki ³(0.03*P/mbar)-4 0, and for a total gas pressures P below 150 may apply that R. _Ne,Kr is at least 0.5.

As indicated above, especially in embodiments the Ne/Kr partial pressure ratio R- _Ne,Kr may be at least 1, such as at least about 1.25, or even at least 1.5.

It appears that at relatively high total pressures and/or at Ne/Kr partial pressure ratio R- _Ne,Kr lower than about 5, even more especially lower than about 4, radiation can be provided with a relatively low 258 nm content (i.e. a relatively high ratio of the spectral power in the 222 nm +/- 10 nm range relative to the spectral power in the 258 nm +/- 10 nm range). Hence, in specific embodiments the Ne/Kr partial pressure ratio R. _Ne,Kr may comply with the formula R _Ne,Kr £(0.03*P/mbar)-4, and wherein for total gas pressures P below 150 may apply that R. _Ne,Kr is at least 0.5. Even more especially, the Ne/Kr partial pressure ratio R. _Ne,Kr may comply with the formula R _Ne,Kr £(0.018*P/mbar)-2.2, and for the total gas pressures P below 150 may apply that R _Ne,Kr is at least 0.5. Yet even more especially, the Ne/Kr partial pressure ratio R _Ne,Kr may comply with the formula R _Ne,Kr £(0.013*P/mbar)-1.45, and for total gas pressures P below 150 may apply that R _Ne,Kr is at least 0.5. Best results may be obtained when the Ne/Kr partial pressure ratio R _Ne,Kr may comply with the formula R _Ne,Kr £(0.01*P/mbar)-l, and for total gas pressures P below 100 may apply that R _Ne,Kr is at least 0.5. The smaller the values of a and the larger the values of b in the aforementioned formulas y=ax-b, the higher the ratio of the spectral power of the 222+/10 nm radiation relative to the 258+/-10 nm radiation.

Especially, for embodiments wherein the Ne/Kr partial pressure ratio R _Ne,Kr may comply with the formula R _Ne,Kr £(0.03*P/mbar)-4, even more especially for embodiments wherein R _Ne,Kr £(0.018*P/mbar)-2.2 applies, yet even more especially for embodiments wherein R _Ne,Kr £(0.013*P/mbar)-1.45 applies (such as wherein R _Ne,Kr £(0.01*P/mbar)-l may apply), the total pressure may be at least about 100 mbar, even more especially at least about 150 mbar.

Especially, in embodiments the total pressure may thus in embodiments be selected from the range of 50-500 mbar, with R _Ne,Kr especially over this entire range being at least about 0.5.

It appears that for CE partial pressures in the range of about 0.5-2.5 mbar, especially in the range of about 1-2.5 mbar, such as 1-2.5 mbar, such as 1-2 mbar, and for partial pressure ranges of krypton (also referred to as Kr) selected from the range of 20-110 mbar, the more desirable total pressures (especially in view of efficiency) may be selected from the range of 100-500 mbar, more especially from the range of 150-450 mbar, even more especially in the range of 200-400 mbar. At such (partial) pressures, the efficiency may be highest. Even better results may be obtained when the krypton partial pressure may be selected from the range of 30-100 mbar, like 40-90 mbar.

To reduce the about 258 nm contribution, it appears useful to increase the total pressure, such as to at least about 200 mbar, especially above about 300 mbar. At krypton partial pressures above about 40 mbar, especially above about 50 mbar, a further increase of the total pressure appears not to decrease substantially further the about 258 nm contribution. This may especially apply for Ch partial pressures in the range of about 0.5-2.5 mbar, especially in the range of about 1-2.5 mbar, such as 1-2 mbar.

It appears desirable to choose the Ch partial pressures in the range of about 0.5-3 mbar, especially in the range of about 1-2.5 mbar in combination with a Kr partial pressure selected from the range of 20-120 mbar, especially at least about 35 mbar. Good results may be obtained when the Ch partial pressures is chosen in the range of about 1-2.5 mbar, especially in the range of about 1.5-2.2 mbar in combination with a Kr partial pressure selected from the range of 25-120 mbar, especially at least about 40 mbar.

Further, it appears that for Ch partial pressures in the range of about 0.5-3.0 mbar, especially in the range of about 1.0-2.5 mbar, it appears desirable (especially in view of efficiency) to select one or more of (i) a Ne/Kr partial pressure ratio over 0.5, especially at least 1.0, even more especially at least about 1.5, yet even more especially at least about 2, and (ii) a total pressure of at least about 200 mbar, even more especially at least about 250 mbar, like even more especially at least about 400 mbar. At such (partial) pressures and/or Ne/Kr partial pressure ratios, the efficiency may be highest. Best results may be obtained when the partial pressure may be 200-450 mbar, especially selected from the range of 250- 450 mbar, such as selected from the range of 250-400 mbar and with Ne/Kr partial pressure ratios of at least 1.5.

To reduce the about 258 nm contribution, it appears (also) useful to select one or more of (i) a Ne/Kr partial pressure ratio not larger than 2, such as not larger than 1.5, like selected from the range of about 0.5-1, and (ii) a total pressure of at least about 100 mbar, even more especially at least about 200 mbar, such as at least about 300 mbar. Especially when selecting a total pressure of at least about 250 mbar, such as at least about 300 mbar, the choice of the Ne/Kr partial pressure ratio may about be any of a range of about 0.5-9 while still having a relatively low about 258 nm contribution, though the lower the Ne/Kr partial pressure ratio, the lower the about 258 nm contribution may be.

Based in the simulations, amongst others good results were obtained with 1< R-Ne.Kr £5, especially wherein 1.5< R.Ne _,Kr <4.5.

Further, in specific embodiments, good simulation results were obtained within the range of a total gas pressure above about 150 mbar and below about 350 mbar.

Especially, an interesting range appears to be 1.5< R. _Ne,Kr <2.5. Further, as such, or especially in combination with the afore-mentioned Ne/Kr partial pressure ratio, good results were obtained with the Kr partial pressure rk may be selected from the range of up to 130 mbar Kr, such as up to about 110 mbar. Above such Kr partial pressure values output and efficiency may decrease. Further, it appears useful when the Kr partial pressure may be selected from the range of about 20-110 mbar and the Ch partial pressure may be selected from the range of 0.5-2.5 mbar. Hence, in specific embodiments 1< R. _Ne,Kr <5, especially wherein 1.5< R. _Ne,Kr <2.5, the Kr partial pressure rk, may be selected from the range of about 20-110 mbar, especially from the range of 30-100 mbar, and the Ch partial pressure may be selected from the range of 0.5-2.5 mbar, especially selected from the range of 1-2.5 mbar, such as 1-2 mbar.

Further, in specific embodiments, good simulation results were obtained within the range of a total gas pressure above about 100 mbar, such as above about 150 mbar, and below about 300 mbar, such as below about 250 mbar. Hence, in specific embodiments 100<P<300 mbar, such as especially 100<P<250 mbar, like in embodiments 150<P<250 mbar. Further, as such, or especially in combination with the afore-mentioned total gas pressure range, good (simulation) results were obtained when the Ch gas partial pressure pen is equal to or above about 1 mbar and equal to or below about 2.5 mbar. Hence, in embodiments the Ch gas partial pressure pen may be selected from the range of 1-2.5 mbar.

Yet further, in specific embodiments, good simulation results were obtained within the range of a total gas pressure equal to or above about 200 mbar and equal to or below about 350 mbar. Further, as such, or especially in combination with the afore mentioned total gas pressure range, good (simulation) results were obtained when the Ne/Kr partial pressure ratio R. _Ne,Kr is at least about 2.2 and at maximum about 4.5. Hence, in specific embodiments 200<P<350 mbar, and 1< R. _Ne,Kr <5 may apply. The area described by this range may have a relatively high performance (especially efficiency), a relatively low contribution of about 258 nm radiation, and may have desirable total pressures.

At higher total pressures, the Ne/Kr partial pressure ratio may also be higher. At lower total pressures, a higher Ne/Kr partial pressure ratio may lead to a too low Kr partial pressure. Hence, when the total pressure is at least about 300 mbar, more especially at least about 350 mbar, like at least about 400 mbar, the Ne/Kr partial pressure ratio may in embodiments be at least 3, such as at least 4, like selected from the range of 3-10, such as selected from the range of 4-10. Hence, in embodiments the Ne/Kr partial pressure ratio may be at least 3, even more especially at least 4, such as at least 5, when the total pressure is at least about 250 mbar, more especially 300 mbar, yet more especially at least about 350 mbar, like at least about 400 mbar. For instance, in embodiments the Ne/Kr partial pressure ratio is at least 4, such as at least 5, when the total pressure is at least about 350 mbar, like at least about 400 mbar. In specific embodiments, the Ne/Kr partial pressure ratio R. _Ne,Kr may comply with the formula R _Ne,Kr £(0.095*P/mbar)-9, the total gas pressure P may be at least 250 mbar, more especially at least about 300 mbar, and R. _Ne,Kr is at least 0.5, more especially at least 3, such as at least 4. Even more especially, in specific embodiments, the Ne/Kr partial pressure ratio R- _Ne,Kr complies with the formula R _Ne,Kr £(0.095*P/mbar)-9, but the pressure is selected such that Ne/Kr partial pressure ratio R _Ne,Kr is at least 3, more especially at least 4, and especially the total gas pressure P may be at least 300 mbar.

Dependent upon amongst the total pressure and the Ne/Kr partial pressure ratio, the contribution to the emitted radiation from the discharge vessel of about 258 nm may be relatively low, or even non-substantial, or even relatively high. In the latter embodiments, the performance may e.g. be relatively high, though it may be desirable to apply the system only under conditions where humans are not exposed to the radiation or to (optically) filter out the about 258 nm radiation. Hence, in embodiments an optical filter may be applied that is transmissive for about 222 nm radiation and less transmissive for about 258 nm radiation than for the about 222 nm radiation. In this way, the ratio of about 222 nm radiation to about 258 nm radiation may be increased. Hence, in embodiments the system may further comprising an optical filter having a higher transmission for a first wavelength selected from the range of 222+/-10 nm than for a second wavelength selected from the range of 258+/-10 nm. Especially, the optical filter may be configured downstream of the discharge vessel. Further, in specific embodiments, the optical filter may have an at least 1.5 times, even more especially an at least two times, higher transmission for a first wavelength selected from the range of 222+/-10 nm than for a second wavelength selected from the range of 258+/-10 nm.

The terms “upstream” and “downstream” relate to an arrangement of items or features relative to the propagation of the light from a light generating means (here the especially the light source), wherein relative to a first position within a beam of light from the light generating means, a second position in the beam of light closer to the light generating means is “upstream”, and a third position within the beam of light further away from the light generating means is “downstream”.

The optical filter may comprise one or more of optical bandpass filters, dichroic filters, prisms, gratings, diffractive filters, etc. In such embodiments, essentially no radiation from the gas composition may leave the system without being transmitted by the filter. Note that herein the term “transmitted” may also refer to “reflected” or “reflected in a predetermined direction”. Hence, “transmitted” in this context may refer to the filter function which may lead to a reduced intensity of the undesired radiation (downstream of the optical filter), especially of the about 258 nm radiation, whether or not via transmission, reflection, diffraction, etc.

The discharge vessel may generate during operation (discharge vessel) radiation. Hence, the system light (system radiation) may essentially consist of (discharge vessel) radiation or of optically filtered radiation (discharge vessel). The optical filter may increase a 222 nm/258 nm intensity ratio. Hence, effectively the system (or lamp or luminaire) may provide at least part of the radiation generated by the discharge lamp during operation thereof.

In specific embodiments, the optical filter may be applied in combination with a discharge vessel with a gas composition complying with a specific Ne/Kr partial pressure ratio, such as in the range of about at least about 0.5 and at maximum about 2.5, and a specific total pressure of at minimum about 150 mbar and at maximum about 250 mbar. Hence, in specific embodiments of the radiation generating system, the Ne/Kr partial pressure ratio R-Ne,Kr may comply with one or more of (i) R _NC.KI -³(0.0 1 *P/mbar)-l, and (ii) 1.5< R.Ne,Kr <2.5; 100<P<300 mbar may apply, and the system may further comprise the optical filter as also described above.

In specific embodiments, the Ne/Kr partial pressure ratio R. _Ne,Kr complies with the formula R _Ne,Kr £(0.03*P/mbar)-4 and the Ne/Kr partial pressure ratio R. _Ne,Kr complies with the formula R _NC.KI -³(0.0 1 *P/mbar)-l

As indicated above, in embodiments the discharge vessel may have a cylindrical design.

Further, in embodiments the discharge vessel may at least partly be defined by a discharge vessel wall. Such discharge vessel wall may especially comprise quartz. Alternatively or additionally, the discharge vessel wall may comprise e.g. CaF2, MgF2, or AI2O3 (sapphire, TGA, or PCA). For example, A1203 may be comprised as an inner protective coating of the quartz glass wall of the discharge vessel, for example to counteract reaction of C12 with the quartz glass. The electrodes may enclose the discharge vessel over at least about 120°, such as at least about 150°. Especially, the electrodes may enclose the discharge vessel over at least 180°, even more especially at least 270°, like in embodiments over 360°. In embodiments, the electrodes (at least partly enclosing the discharge vessel) may be thin plate-like electrodes (e.g. in embodiments up to about a few pms thickness). In other embodiments, the electrodes (at least partly enclosing the discharge vessel) may be mesh-like electrodes. The distance between the electrodes may be selected from the range of about 4-10 mm, such as about 5-10 mm. The (cylindrical) discharge vessel may in embodiments have a length (LI) selected from the range of at least about 10 mm, such as especially at least about 15 mm, like in embodiments 15-80 mm, like e.g. in the range of about 15-50 mm. However, larger than about 80 mm may also be possible. In embodiments, the discharge vessel may have an inner diameter D1 selected from the range of 4-10 mm. Further, the discharge vessel may have a wall thickness dl selected from the range of 0.4-2.0 mm, like at least about 0.7 mm, such as up to about 1.5 mm, like 0.5-1.5 mm, such s 0.7-1.2 mm. Especially, in embodiments the discharge vessel may have an outer diameter selected from the range of about 4.5-12 mm, such as e.g. selected from the range of about 4-8 mm.

Hence, especially in embodiments the discharge vessel may have an inner diameter (Dl) selected from the range of 4-10 mm, the discharge vessel may have a vessel wall having a wall thickness (dl) selected from the range of 0.4-2.0 mm, wherein the electrodes may be configured external of the discharge vessel, and wherein the electrodes have an inter electrode distance 11 selected from the range of 4-10 mm.

Note that the discharge vessel is not necessarily cylindrical. Other shapes, like having an ellipse cross-section, may also be possible.

As indicated above, in embodiments the discharge vessel may have a substantially cylindrical design. In embodiments, the electrodes may also have a substantially cylindrical design, enclosing the discharge vessel over at least 180°, even more especially at least 270°, like in embodiments over 360°.

The electrodes may have a width (W2), defined parallel to a length axis of the discharge vessel, which is individually selected for the two electrodes from the range of 2- 45% of the length of the discharge vessel. Even more especially, each electrode may have a width selected from the range of 10-30% of the electrode length. The dimensions of the electrodes may especially be selected such that the electrodes have an inter electrode distance 11 selected from the range of 4-10 mm. One of the electrodes may be earthed. As indicated above, in embodiments the electrodes may comprise mesh electrodes. With mesh electrodes, less light may be blocked.

Further, it appears that the operation conditions may especially provide a desirable performance and/or low 258 nm (relative) intensity. Thereto the radiation generating system may be configured to provide in an operational mode pulsed potential differences to the electrodes, wherein the potential difference is selected from the range of 3.5-7.5 kV, especially selected from the range of 4-6.5 kV, such as in embodiments selected from the range of 4.5-5 kV. Further, in an operational mode the pulse frequency is selected from the range 0.5-200 kHz, like at least 1 kHz, such as especially at least 2 kHz, such as selected from the range of 7.5-150 kHz, like especially selected from the range of about 10- 100 kHz. Especially, in this way during at least part of the time the operational mode is executed, the discharge vessel emits radiation (“discharge vessel radiation”) having a wavelength selected from the range of 222+/-10 nm.

Therefore, in embodiments the radiation generating system may further comprise electrodes functionally coupled to the discharge vessel, wherein in an operational mode, the radiation generating system is configured to provide pulsed potential differences to the electrodes, wherein the potential difference may be selected from the range of 4.5-5 kV, with a pulse frequency selected from the range of 0.5-200 kHz, like 10-100 kHz, and wherein during at least part of the time the operational mode is executed, the discharge vessel emits radiation having a wavelength selected from the range of 222+/-10 nm, such as 222+/- 3 nm. As indicated above, the functional coupling of the electrodes may include an at least partial enclose of the discharge vessel. Further, the electrodes may be in physical contact with the discharge vessel. The pulsed potential differences have a pulse width selected from the range of 0.25-5 ps, in specific embodiment selected from the range of 0.7-1.5 ps.

The discharge vessel may be comprised by a lamp (or a luminaire). In embodiments the system may essentially consist of the lamp. In other embodiments, the system may comprise a luminaire comprising the DBD lamp. In yet other embodiments, the system may comprise a plurality of the DBD lamps. For instance, the DBD lamps may be configured in a grid.

The system may comprise a control system or may be functionally coupled to a control system. The control system may especially be configured to control the (excimer) lamp. For instance, the control system may control the excimer lamp in dependence of a sensor signal, a time scheme (or timer), or a user input (signal).

The term “controlling” and similar terms especially refer at least to determining the behavior or supervising the running of an element. Hence, herein “controlling” and similar terms may e.g. refer to imposing behavior to the element (determining the behavior or supervising the running of an element), etc., such as e.g. measuring, displaying, actuating, opening, shifting, changing temperature, etc.. Beyond that, the term “controlling” and similar terms may additionally include monitoring. Hence, the term “controlling” and similar terms may include imposing behavior on an element and also imposing behavior on an element and monitoring the element. The controlling of the element can be done with a control system, which may also be indicated as “controller”. The control system and the element may thus at least temporarily, or permanently, functionally be coupled. The element may comprise the control system. In embodiments, the control system and element may not be physically coupled. Control can be done via wired and/or wireless control. The term “control system” may also refer to a plurality of different control systems, which especially are functionally coupled, and of which e.g. one control system may be a master control system and one or more others may be slave control systems. A control system may comprise or may be functionally coupled to a user interface.

The control system may also be configured to receive and execute instructions form a remote control. In embodiments, the control system may be controlled via an App on a device, such as a portable device, like a Smartphone or I-phone, a tablet, etc.. The device is thus not necessarily coupled to the lighting system, but may be (temporarily) functionally coupled to the lighting system.

Hence, in embodiments the control system may (also) be configured to be controlled by an App on a remote device. In such embodiments the control system of the lighting system may be a slave control system or control in a slave mode. For instance, the lighting system may be identifiable with a code, especially a unique code for the respective lighting system. The control system of the lighting system may be configured to be controlled by an external control system which has access to the lighting system on the basis of knowledge (input by a user interface of with an optical sensor (e.g. QR code reader) of the (unique) code. The lighting system may also comprise means for communicating with other systems or devices, such as on the basis of Bluetooth, WIFI, LiFi, ZigBee, BLE or WiMAX, or another wireless technology.

The system, or apparatus, or device may execute an action in a “mode” or “operation mode” or “mode of operation” or “operational mode”. Likewise, in a method an action or stage, or step may be executed in a “mode” or “operation mode” or “mode of operation” or “operational mode”. This does not exclude that the system, or apparatus, or device may also be adapted for providing another controlling mode, or a plurality of other controlling modes. Likewise, this may not exclude that before executing the mode and/or after executing the mode one or more other modes may be executed.

However, in embodiments a control system may be available, that is adapted to provide at least the controlling mode. Would other modes be available, the choice of such modes may especially be executed via a user interface, though other options, like executing a mode in dependence of a sensor signal or a (time) scheme, may also be possible. The operation mode may in embodiments also refer to a system, or apparatus, or device, that can only operate in a single operation mode (i.e. “on”, without further tunability).

Hence, in embodiments, the control system may control in dependence of one or more of an input signal of a user interface, a sensor signal (of a sensor), and a timer. The term “timer” may refer to a clock and/or a predetermined time scheme.

The control system may e.g. control the intensity of the radiation of the excimer lamp via e.g. pulse-width modulation. For instance, in embodiments by reducing or increasing the pulse frequency, the intensity of the discharge vessel radiation may be reduced or increased, respectively.

As can be derived from the above, the (radiation generating) system may comprise a sensor or may be functionally coupled to a sensor. Especially, the sensor may be functionally coupled to a control system. Hence, the system, more especially the excimer lamp, may be operated in dependence of a sensor signal of a sensor.

In embodiments, the sensor may comprise one or more sensors selected from the group comprising: a movement sensor, a presence sensor, a distance sensor, an ion sensor, a gas sensor, a volatile organic compound sensor, a pathogen sensor, an airflow sensor, a sound sensor, and a communication receiver. The ion sensor may comprise a positive ion sensor. Additionally or alternatively, the ion sensor may comprise a negative ion sensor. The pathogen sensor may comprise a sensor for one or more of bacteria, viruses, and spores. Alternatively or additionally, the sensor may comprise a temperature sensor. Further, alternatively or additionally, the sensor may comprise a humidity sensor.

As can be derived from the above, in embodiments the (radiation generating) system may comprise a grid of a plurality of lamps or luminaires. Such grid may be installed in a roof or ceiling. In embodiments, the individual DBD lamps or luminaires may be functionally connected to the control system. In embodiments, the individual DBD lamps or luminaires in the grid may comprise a sensor, especially one or more of a radiation sensor and an air flow sensor. In embodiments, a first DBD lamp or luminaire may adjust its settings based on the one or more sensor signals of one or more second DBD lamps or luminaires. In embodiments, the individual DBD lamps or luminaires, especially the control systems thereof, may communicate with one another. The individual DBD lamps or luminaires may comprise means for communicating with other units, systems or devices, such as on the basis of Bluetooth, WIFI, LiFi, ZigBee, BLE or WiMAX, or another wireless technology. In specific embodiments, settings of a first DBD lamp or luminaire of the grid may depend on the settings of a second DBD lamp or luminaire of the grid., wherein the settings may comprise one or more of device radiation intensity, location, etc.

In embodiments, the system may be comprised in a single DBD lamp or luminaire.

In yet a further aspect, the invention also provides a (DBD) lamp or a luminaire comprising the light generating system as defined herein. The luminaire may further comprise a housing, optical elements, louvres, etc. The lamp or luminaire may further comprise a housing enclosing the light generating system. The lamp or luminaire may comprise a light window in the housing or a housing opening, through which the system light may escape from the housing. In embodiments, the window may comprise an optical filter, e.g. to reduce the 258 nm contribution.

In yet a further aspect, the invention also provides a method for treating a gas or a surface, the method comprising providing the radiation (especially having a wavelength selected from the range of about 222 +/-5 nm) as defined herein to the gas or the surface with the radiation generating system as defined herein. To this end, the discharge lamp may be applied. Hence, effectively the system (or lamp or luminaire) may provide at least part of the radiation generated by the discharge lamp during operation thereof. This radiation may thus especially have intensity at about 222 nm. With this radiation, the gas or the surface may be treated, like disinfecting. This radiation may also have intensity at about 258 nm, dependent upon e.g. the gas composition (see also above) and the application of an optical filter.

In embodiments, the method may comprise exposing air to the radiation from the system. Hence, in specific embodiments, the method for treating air may comprise exposing air the radiation from the system. In this way, the method may provide one or more of disinfection of pathogens, removal of particles and dust, and removal of odors. Especially, the treatment of the air may comprise disinfection of (the) air. In embodiments, the method may comprise exposing a surface to the radiation from the system. The surface may be selected from a desk, a floor, a wall, a kitchen counter, a door handle, a tap, a handrail, a control panel, etc. The embodiments described above in relation to the system of the present invention, may also apply for the method of the invention. The radiation may be provided in a space, e.g. in the method for treating a gas or a surface (available in the space). The term “space” may for instance relate to a (part of) hospitality area, such as a restaurant, a hotel, a clinic, or a hospital, etc.. The term “space” may also relate to (a part of) an office, a department store, a warehouse, a cinema, a church, a theatre, a library, etc. However, the term “space” also relate to (a part of) a working space in a vehicle, such as a cabin of a truck, a cabin of an air plane, a cabin of a vessel (ship), a cabin of a car, a cabin of a crane, a cabin of an engineering vehicle like a tractor, etc.. The term “space” may also relate to (a part of) a working space, such as an office, a (production) plant, a power plant (like a nuclear power plant, a gas power plant, a coal power plant, etc.), etc. For instance, the term “space” may also relate to a control room, a security room, etc. Especially, the term “space” may herein refer to an indoor space. In yet other embodiments, the term “space” may also relate to a toilet room or bathroom. In yet other embodiments, the term “space” may also relate to an elevator. In embodiments, the term “space” may also refer to a conference room, a school room, an indoor hallway, an indoor corridor, an indoor space in an elderly home, an indoor space in a nursing home, etc. In embodiments, the term “space” may refer to an indoor sport space, like a gym, a gymnastics hall, in indoor ball sport space, a ballet room, a swimming pool, a changing room, etc. In embodiments, the term “space” may refer to an (indoor) bar, an (indoor) disco, etc. The method may be executed in dependence of a sensor signal of a sensor (see further also above).

The terms “light” and “radiation” are herein interchangeably used, unless clear from the context that the term “light” only refers to visible light. The terms “light” and “radiation” may thus refer to UV radiation, visible light, and IR radiation. In specific embodiments, especially for lighting applications, the terms “light” and “radiation” refer to (at least) visible light.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Fig. 1 schematically depicts some embodiments;

Fig. 2 schematically depict some aspects (of embodiments);

Fig. 3 schematically depicts an embodiment of an application;

Figs. 4a-4b show some data. The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Fig. 1 schematically depicts two embodiments of a radiation generating system 1000 comprising an excimer lamp 100. The excimer lamp 100 comprises a discharge vessel 400. The discharge vessel 400 contains a gas composition 405. In this schematically depicted embodiment, the excimer lamp 100 is of the dielectric barrier discharge lamp type. Especially, the discharge vessel 400 has a cylindrical design.

The radiation generating system 1000 further comprises electrodes 110,120 functionally coupled to the discharge vessel 400.

Hence, the dielectric barrier discharge lamp may comprise a discharge volume which is delimited by essentially a single wall, here discharge vessel wall 403, wherein (during operation) different parts of the vessel wall 403 may be exposed to different electrical potentials by means of a power supply for exciting a gas discharge within the discharge volume. The volume enclosed by the vessel wall 403 is indicated with reference 407. Note that different shapes of the discharge vessel 400 may also possible. Herein, a cylindrical shape is schematically depicted. However, the invention is not necessarily limited to discharge vessels 400 having a cylindrical (cross-sectional) shape.

Especially, in embodiments in an operational mode, the radiation generating system 1000 may be configured to provide pulsed potential differences to the electrodes 110,120. The potential difference may be selected from the range of 4.5-5 kV. The pulse frequency may be selected from the range of 10-100 kHz. During at least part of the time the operational mode is executed, the discharge vessel 400 emits radiation 101 comprising a wavelength selected from the range of 222+/-10 nm. In embodiments, the pulsed potential differences have a pulse width selected from the range of 0.7-1.5 ps.

The discharge vessel 400 may have a length LI, e.g. selected from the range of 15-80 mm, like e.g. in the range of about 15-50 mm. Reference A indicates a discharge vessel axis or length axis. The length LI is especially defined parallel to the is axis. The discharge vessel wall 403 may essentially be configured cylindrical around this axis (though other shapes of the discharge vessel 400) may also be possible.

Fig. 1 effectively also schematically depicts embodiments of a dielectric barrier discharge lamp or a luminaire, which are indicated with reference 1200.

During operation, the excimer lamp 100 (or DBD lamp) may generate excimer lamp radiation 101 (DBD lamp radiation). At least part of the excimer lamp light 101 may escape via a window 1205. This may be the window 1205 of a housing 1202 of a DBD lamp or luminaire 1200. In this way, system light 1001 is provided. As Fig. 1 also depicts a DBD lamp or a luminaire, the light may also be indicated as DBD lamp light or luminaire light, indicated with reference 1201. Essentially only via the window 1205, excimer lamp light 101 may escape from the system 1000 or luminaire 1200 to the external of the system 1000 or luminaire 1200, respectively.

Embodiment I shows the use of an optical filter 1210. Hence, the radiation generating system 1000 may further comprise an optical filter 1210 having an at least two times higher transmission for a first wavelength selected from the range of 222+/-10 nm than for a second wavelength selected from the range of 258+/-10 nm. As schematically depicted, the optical filter 1210 is configured downstream of the discharge vessel 400. Hence, here the window 1205 may comprise the optical filter 1210. By way of example, Embodiment II has no optical filter, and the window 1205 is essentially an opening (in the housing 1202).

Hence, the lamp or luminaire 1200 may provide radiation 1201 which may essentially be the system light 1001. The system light 1001 may comprise the (discharge vessel) radiation 101 (see embodiment II) or optically filtered (discharge vessel) radiation 101 (see embodiment I). Hence, in an operational mode the system light 1001 or the light 1201 may comprise radiation having at least intensity at wavelength of about 222 nm.

Fig. 2 schematically depicts in more detail an embodiment of the discharge vessel 400. The discharge vessel 400 may have an inner diameter D1 selected from the range of 4-10 mm. The discharge vessel 400 has a vessel wall 403 having a wall thickness dl, e.g. selected from the range of 0.4-2.0 mm. The electrodes 110,120 may be configured external of the discharge vessel 400. The electrodes 110,120 have an inter electrode distance 11, which may be selected from the range of 4-10 mm.

Reference Dl indicates the internal diameter or inner diameter, and reference D2 indicates the external or outer diameter of the discharge vessel 400. References W2 indicate the widths of the electrodes 110,120, which may be the same or which may be different. Reference A indicates a discharge vessel axis or length axis.

In embodiments, the gas composition 405 may comply with the following conditions (at about 20 °C): (a) a total gas pressure P may be selected from the range of 50- 500 mbar; (b) a CE gas partial pressure pc12 may be selected from the range of 0.5-3 mbar; (c) a Ne/Kr partial pressure ratio R _Ne,Kr may be selected from the range of 0.5-20; (d) a Kr partial pressure rkt selected from the range of over 15 mbar; and (e) at least 33% Ne.

In embodiments, the Ne/Kr partial pressure ratio R _Ne,Kr may be selected from the range of 0.5-10, such as 0.5-5, like especially 1-5. Especially, in embodiments the Ne/Kr partial pressure ratio R _Ne,Kr may be selected from the range of 1.5-4. However, higher ratios may also be possible. In embodiments, the Ne/Kr partial pressure ratio R _Ne,Kr complies with the formula R _NC.KI -³(0.01 *P/mbar)- l , and for total gas pressures P below 100 mbar applies that R _Ne,Kr is at least 0.5. In embodiments, the Ne/Kr partial pressure ratio R _Ne,Kr complies with the formula R _NC.KI -³(0.0 18*P/mbar)-2 2, and for total gas pressures P below 150 mbar applies that R _Ne,Kr is at least 0.5. In specific embodiments, the Ne/Kr partial pressure ratio R _Ne,Kr complies with the formula R _NC. k _i ³(0.0225 *P/mbar)-2 875, and for total gas pressures P below 150 mbar applies that R _Ne,Kr is at least 0.5.

In embodiments, the Ne/Kr partial pressure ratio R _Ne,Kr complies with the formula R _Ne,Kr £(0.03*P/mbar)-4, and for total gas pressures P below 150 mbar applies that R _Ne,Kr is at least 0.5. In embodiments, the Ne/Kr partial pressure ratio R _Ne,Kr complies with the formula R _Ne,Kr £(0.018*P/mbar)-2.2, and for total gas pressures P below 150 mbar applies that R _Ne,Kr is at least 0.5. In specific embodiments, the Ne/Kr partial pressure ratio R _Ne,Kr complies with the formula R _Ne,Kr £(0.013*P/mbar)-1.45, and for total gas pressures P below 150 mbar applies that R _Ne,Kr is at least 0.5. Especially, in embodiments the Ne/Kr partial pressure ratio R _Ne,Kr complies with the formula R _Ne,Kr £(0.01*P/mbar)-l, and for total gas pressures P below 100 mbar applies that R _Ne,Kr is at least 0.5.

In specific embodiments, 1< R _Ne,Kr <5, especially wherein 1.5< R _Ne,Kr <2.5; wherein the Kr partial pressure rk, may be selected from the range of about 20-110 mbar, especially from the range of 30-100 mbar, and the CE partial pressure may be selected from the range of 0.5-2.5 mbar. Further, in specific embodiments 100<P<300 mbar, such as in embodiments 100<P<300 mbar. Yet further, in specific embodiments the CI2 gas partial pressure pcu may be selected from the range of 1-2.5 mbar.

In embodiments, the Ne/Kr partial pressure ratio R _Ne,Kr complies with one or more of (i) R _NC.KI -³(0.01 *P/mbar)- l , and (ii) 1.5< R _Ne,Kr <2.5; 100<P<250 mbar; and further the system 1000 may comprise the optical filter 1210 (see also above).

Referring to also Fig. 3, the invention also provides in embodiments a method for treating a gas or a surface, the method comprising providing the radiation 101 to the gas or the surface with the radiation generating system 1000. Fig. 3 schematically depicts an embodiment of a lamp or luminaire 1200 comprising the dielectric barrier based radiation generating system 1000 as defined herein. The lamp or luminaire 1200 is configured to emit radiation 1201. The radiation 1201 may in specific embodiments comprise dielectric barrier discharge lamp radiation 101. In such embodiments, the lamp or luminaire 1200 may be used for disinfection. In other embodiments, the radiation 1201 may comprise luminescent material light. Especially, in such embodiments the lamp or luminaire 1200 may be used for lighting. Especially, however, the radiation 1201 may essentially comprise the (optically filtered) discharge lamp radiation 101. The position and shape of the lamp or luminaire 1200 is only schematically. Other shapes and/or positions, like in a grid in the ceiling, a device for standing on the floor or on a table, a handheld device, etc. may also be possible. Though not shown in detail in Fig. 3, in specific embodiments the dielectric barrier based radiation generating system 1000 has a design selected from an axial design, a coaxial design, or a plate-like design. Reference 325 refers to a sensor, such as e.g. a movement sensor or a presence sensor (see also above for embodiments of possible sensors). The control system 300 may control the dielectric barrier based radiation generating system 1000 (or the lamp or luminaire) for instance as function of the sensor signal of the sensor

325. Reference 1300 refers to a space. The dielectric barrier based radiation generating system 1000 may provide system light 1001 to the space. As indicated above, the system light 1001 may essentially consist of (discharge vessel) radiation 101 or of optically filtered radiation (discharge vessel) 101.

Examples of compositions

Here below, a non-limiting number of a few possible gas compositions (examples) are provided:

¹ values in third row (example 3) are used as reference Further examples are provided in below table, displayed in a slightly different way: b same reference example as preceding table

Some examples from these tables are shown in Fig. 4a. The formulas are also indicated in the text. Amongst others, three parts may be distinguished, of which for the middle part may apply that the Ne/Kr partial pressure ratio R. _Ne,Kr complies with the formula R _Ne,Kr £(0.03*P/mbar)-4 and the Ne/Kr partial pressure ratio R. _Ne,Kr complies with the formula R _Ne,Ki ³(0.01*P/mbar)-l. In that part, the performance may be relatively high, and the 258 nm may still be relatively low. Left from the part, the performance may even be better, but the 258 nm contribution may be higher. Right (below) that part, the performance may be a bit lower, but the 258 nm contribution may be relatively lower or essentially absent and no optical filter may be necessary for certain applications. The reference I is used to indicate a region where performance may be relatively high, and reference II is used to indicate a region where the relative contribution of 258 nm is relatively low. In essentially all examples, the Kr partial pressure was above 15 mbar, in general above about 20 mbar.

In Fig. 4b embodiments of possible upper and lower ranges of chlorine pressure in relation to Kr pressure are depicted. Best results may be obtained between about 1-2.5 mbar CL. Further, best results are obtained in the range between the upper and the lower curve.

The term “plurality” refers to two or more.

The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%.

The term “comprise” also includes embodiments wherein the term “comprises” means “consists of’.

The term “and/or” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term "comprising" may in an embodiment refer to "consisting of but may in another embodiment also refer to "containing at least the defined species and optionally one or more other species".

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system claim, enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. In yet a further aspect, the invention (thus) provides a software product, which, when running on a computer is capable of bringing about (one or more embodiments of) the method as described herein.

The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.