Method and apparatus for treating materials using electrodeless lamps

The output wavelengths of an electrodeless lamp are controlled by passing a fluid over the surface of the lamp to control its temperature. The stabilized temperature prevents thermal runaway of the lamp and stabilizes the output wavelengths of the lamp. When the fluid passing over the lamp is water, the lamp can be used for sanitary treatment of the water. Lamp radiation can be enhanced by shaping the electrodeless lamp to provide maximally effective photonic output.

BACKGROUND OF THE INVENTION

Electrodeless lamps can provide advantages over electrode lamps. The electrodeless lamps require no electrical connections, can be energized without direct mechanical contact to the lamps, and can be energized by the field action of remote radio frequency optical stimulation, or even magnetic fields. Instead of using electrical current passing through electrodes to excite an electrodeless lamp for producing light, in most cases radio frequency energy is induced through a quartz glass envelope to excite the gas in the lamp and cause it to emit photonic radiation. Primarily used in ultraviolet curing applications where power and speed are requirements, this lamp technology offers significant benefits in other applications as well.

Electrodeless lamps can be run at much higher power levels than electrode lamps allowing them to produce much greater amounts of ultraviolet light than their electrode counterparts. Electrodeless lamps exhibit long life spans on the order of 20,000 hours and, theoretically, can last much longer than that. They are very sturdy and withstand both mechanical and thermal shock and vibration very well.

Electrodeless lamps provide engineering flexibility. Lamp geometries are not fixed in size and shape, and can easily be adjusted to conform to the needs of difficult applications. Among these are applications such as treatment with ultraviolet light in polymer curing operations and in water treatment. Though in the past electrodeless lamps have not generally been used in water purification systems, they can be much better than electrode lamps for this purpose.

In some respects, industry is heavily invested and dependent on using electrode lamps. Because of this, electrodeless lamps have not been used as extensively as they would otherwise have been. The key reasons for this are technical. Electrodeless ultraviolet applications require more sophistication and finesse to engineer than do electrode models. Among the most difficult challenges in using electrodeless lamps is engineering a method for exciting and controlling the output of the lamps. In most cases radio frequency power and coupling systems are used to power the lamps. Lamp geometries, and fill mixes, which are the combination of elements that are excited by an energy source to make ultraviolet light, are engineered to couple with the lamps. In many applications the coupling is achieved, but control of the lamp becomes difficult due to dependence of the coupling on the temperature of the lamps, and the lamps are prone to thermal runaway.

Another problem is that, without special envelope material, in many applications electrodeless lamps produce large amounts of ozone. Ozone can be hazardous to man and machine and should be tightly managed.

Among these problems the chief reason that electrodeless lamps are not used more is that they are extremely difficult to manage and control. In radio frequency applications as an electrodeless lamp continues to operate, it couples more and more strongly with and draws more and more energy from the available radio frequency field, which in turn makes it increase its operating temperature. Subsequently, that causes it to couple more strongly, and it draws more of the available energy. Although this runaway results in more relative ultraviolet output, it also causes the peak wavelength output of the lamp to change because the peak wavelength output of the lamp is dependent on the operating temperature of the lamp. This causes the lamp to be less useful for some applications.

For example, lamps filled with a gas mixture comprising mercury gas and argon gas, the most common fill mix, have not been widely used for water purification because the germicidal bandwidth needed for water purification occurs at about 240 nm (nanometers or 10−9meters) to 265 nm wavelength. The problem is that emission of photons at this wavelength range occurs best when the lamp is kept in a temperature range of from about 90° F. (degrees Fahrenheit) to 110° F. Thermal runaway causes the lamp to undesirably exceed this temperature, causing the desired wavelengths to fall off, while other wavelengths, such as those used in some kinds of curing rise dramatically. The peak emission wavelength usually rises to about 360 nm. Such a wavelength is good for curing some kinds of polymer compositions but is not good for killing water borne bacteria. This lack of lamp output stability at the germicidal wavelengths has prevented this technology from being developed for various uses requiring specific output wavelengths. This is true for uses such as water purification, and a method for controlling the characteristic thermal runaway is needed.

BRIEF DESCRIPTION OF THE INVENTION

A method is provided for controlling the photonic output of an electrodeless lamp excited by an energy source outside the lamp. The method comprises passing a fluid over the surface of the electrodeless lamp and controlling the temperature of the fluid to regulate the operating temperature of the lamp. When the temperature of the electrodeless lamp is controlled, the photonic output of the lamp is maintained within a desired range of wavelengths that are dependent on the operating temperature of the lamp.

A water purification system for making potable water is provided comprising an electrodeless lamp excited by an energy source outside the lamp. A layer of water that is to be treated is allowed to flow over the surface of the lamp to expose the water to the output radiation of the lamp. Temperature control of the lamp is accomplished using the flowing water to maintain the temperature of the lamp. By controlling the temperature of the electrodeless lamp the wavelength of the lamp output can be held to germicidal wavelengths to germicidally treat the water flowing over the lamp.

An electrodeless lamp for treating fluids with radiation from the lamp is constructed. The lamp has a first end and a second end and is comprised of an inner tube and an outer tube. The inner tube and the outer tube are joined at the first end and at the second end to form an annular envelope with a continuous outer surface for containing a gas excitable from outside the envelope. The envelope so formed provides an axial channel for passing a fluid through the inner tube exposing the fluid to radiation from the lamp. The lamp also permits fluid to be passed over the outer tube exposing the fluid to radiation from the lamp.

A water purification apparatus for actinically treating water for potability is provided. It comprises a tubular manifold having a closed end and an open end and an electrodeless lamp having an annular shape with a central channel for passing water through the channel. The lamp is mounted inside the manifold to allow water to pass over the outside of the lamp and through the channel of the lamp. On the open end of the manifold a header is attached. The header has a water inlet, a water outlet, and a seal at the end of the lamp adjacent the header to prevent water passing through the channel from mixing with water passing over the outside of the lamp. The apparatus allows water to flow through the manifold such that it passes through both a space between the outside of the lamp and the inside of the manifold and through the channel of the lamp. An energizing source external to the lamp excites the lamp to radiate ultraviolet light.

DETAILED DESCRIPTION OF THE INVENTION

A method for controlling the peak output wavelengths of electrodeless lamps and maintaining them at desired wavelengths indefinitely is described. The method extends across the spectrum of electrodeless lamp output wavelengths.

A significant discovery for water purification, the invention also permits uses of electrodeless lamps in curing and hazardous material remediation applications where they previously were not viable. For example, many polymer systems are engineered to cure with light centered at a wavelength of about 254 nm (nanometers) and spanning a wavelength of from about 240 nm to about 265 nm, which is also the best germicidal frequency for treating water. In many industrial applications ordinary electrode lamps are used for the ultraviolet curing source because they are more easily controlled than are electrodeless lamps and do not runaway thermally as do electrodeless lamps. Using the invention an electrodeless lamp can now reach and maintain the 254 nm wavelength range without runaway. Because of the additional power possible with electrodeless lamps over electrode lamps, curing operations can be sped up by as much as a factor of 4.

An additional benefit is that the invention provides a method for controlling and even preventing the production of ozone by an electrodeless lamp. This eliminates ozone control by such procedures as doping the quartz comprising the envelope that forms the lamp. Controlling ozone generation can also eliminate ventilation requirements. However, in certain applications it is desirable to create ozone for treating water or for other processing purposes.

Electrodeless lamps are usually, but not always, comprised of a quartz envelope filled with a gaseous fluid. Often mixes of gasses are used in the envelope. Commonly, mercury gas is used and is mixed with argon gas and sometimes small amounts of other gases. In operation the gases are usually radiationally excited, often by a nearby radio frequency field, which can be created by various methods such as by a magnetron often similar to that used in a microwave oven. The excited gas in the envelope, experiencing elevated electronic states, emits photonic energy at specific wavelengths as it tries to return to its unexcited state. The specific frequencies emitted are generally dependent on the particular gas or gas mixture used in the envelope, the level of excitation, and the temperature.

In the case of electrodeless lamps when operated in open air, the radio frequency field often couples with the gas in the lamp, and as the temperature rises due to the absorption of radio frequency energy by the gas, the gas reaches a continuously more easily excited state causing the temperature of the lamp to rise in an uncontrollable manner. It is difficult to control this runaway temperature by controlling the energy output of the exciting field since the field couples more and more strongly to the gas with temperature and in a nonlinear fashion. Various methods have been tried to control the thermal characteristics of electrodeless lamps such as rotating the bulb or blowing air on it. These methods work where light output is the only requirement from the lamp, but they do not work well where a specific range of wavelengths is desired that is variable according to temperature.

As shown inFIG. 1, a better method for controlling the photonic output of an electrodeless lamp assembly100excited by an outside energy source103is to pass water or some other temperature stabilizing fluid102over the surface of the lamp104causing the temperature of the lamp101to be limited by the fluid102. Stabilizing the temperature of the lamp101by passing the fluid102over its surface104allows more flexibility in managing power input to the lamp from the energizing field103. The stabilization allows greater amounts of energy from the field103to be applied to the lamp101without causing thermal runaway, and the energizing source can be used in combination with the flowing fluid102to control the performance of the lamp101.

Water makes a suitable fluid102for such a purpose because it is a simple matter to control the lamp101temperature by adjusting the temperature and flow rate of the water as it is exposed to the lamp surface104. When the temperature of the water is adequately controlled, the lamp101can be made to operate at a specific output range of wavelengths. For example, with an electrodeless lamp101filled with a gas105mix comprising argon and mercury, and regulated to hold at about90F (degrees Fahrenheit) to about110F during excitation, the lamp101peak output will be centered on about 253.7 nm (nanometers) wavelength and will maintain this ultraviolet wavelength peak so long as the temperature of the lamp101is held steady. As it turns out, the wavelength range centered on about 253.7 nm is particularly effective in the germicidal treatment of water, and radiation centered on wavelengths surrounding 253.7 nm are known as the germicidal wavelengths. This particular wavelength is also particularly effective in the curing of certain polymer compounds.

In one embodiment a difficulty with this approach, when radio frequency energy is used, is the problem of passing the radio frequency energy through the fluid102, water in this embodiment, to the gas105since the lamp surface104is covered with water and the water tends to reduce the energy delivered to the lamp101. To improve energy delivery to the gas105, the depth of the water passing over the lamp101is controlled. It is noted that increasing the power output of the outside energy source103, in this embodiment a magnetron, can allow the use of greater depths of water according to the power requirements needed to start and run a particular lamp101.

In another embodiment it is possible to better regulate the energy coupling between the gas105and the energy source103since the water flowing over the lamp101acts as a buffering load on the, in this embodiment, radio frequency energy and makes the gas105response to changes in the excitation energy provided to the lamp101less sensitive to changes in radio frequency energy output. The flowing fluid102can absorb some of the energy from the radio frequency field effectively damping the radio frequency energy as it couples with the gas105in the electrodeless lamp101. In this sense the flowing fluid102buffers the load on the radio frequency field. Since in some applications variations in output from an excitation source are possible only in discrete steps, the flowing fluid102can be used to help with control of the excitation energy reaching the gas105in the lamp101.

In another embodiment it is possible to control the temperature of the fluid102using the lamp101and the external excitation source103, also referred to as the energizing source103, individually or in combination. In this embodiment a radio frequency source can be used. When fluid102is not flowing past the lamp101, it is not always desirable to energize the lamp101for various reasons including, but not limited to, energy conservation. A problem can arise in restarting the lamp101.

When the temperature of the fluid102surrounding the lamp101falls below the needed operating temperature of the lamp101, the gas105in the lamp101is warmed to some minimum ignition temperature before the lamp101can be lit. Further, if the system providing the temperature regulating fluid102is cold, it can take time to bring the whole system100up to operating temperature and ignite the lamp101. In this context the word ignition refers only to achieving conditions for and lighting the lamp and not to any kind of combustion, since the lamp operates based on the excitation and de-excitation of the gases contained therein.

In systems100where the output of the lamp101is immediately needed at some specific temperature related wavelength, the warm-up time can be a problem. For example, in one embodiment where the fluid102flowing past the lamp needs to be treated by the lamp101output, the lamp101should be on as soon as the fluid flow starts, or the initial fluid102flowing past the lamp101will not receive the needed treatment.

To solve this problem, if the fluid102surrounding the lamp101is kept at the needed ignition temperature for the lamp101, even though the fluid102flow stream external to the lamp system100is at a low temperature, the lamp101can be instantaneously lit because it is at operating temperature. One feature of electrodeless lamps101is that although they need to be at operating temperature for ignition, they will remain in a lit state even though the temperature of the surrounding fluid102drops temporarily. Further, they are slow to respond in terms of wavelength output change when they encounter temporary drops in flowing fluid102temperatures.

Because of the above, rapid ignition capability can be achieved in electrodeless lamps101by regulating the fluid temperature surrounding the lamp101to the needed operating temperature, which depends on the gas105used in the lamp101and the wavelength output desired from the lamp101.

Fluid based temperature control can allow power input to the lamp101from the energizing field103to be more easily regulated without causing thermal runaway permitting lamp101output to be controlled by the combination of power input to the lamp101from the energizing field103and temperature control by the fluid102surrounding the lamp101.

In the embodiment where the lamp gas105is primarily comprised of argon and mercury, and the fluid102surrounding the lamp101is water with a desired lamp101output centered on about 253.7 nm, maintaining the water surrounding the lamp101at a temperature of from about 85° F. to about 100° F. provides rapid ignition of the lamp101with the desired output wavelengths.

In another embodiment the lamp101and system100can be turned off and allowed to come to ambient temperature. When this occurs, treatment of the fluid102surrounding the lamp101can only be accomplished if the fluid102flow is stopped and blocked from passing the lamp101while the lamp101is off; the energizing source103warms the fluid102and the lamp101up to ignition temperature; the lamp101is lit; and fluid102flow is then established.

From another aspect one of the negatives of using electrodeless lamps101is that they produce ozone from the interaction of the outside surface of the lamp101with the atmosphere. When water is used as the fluid102, the water flowing over the surface of the lamp101inhibits the reaction of the lamp surface104with the oxygen in the atmosphere substantially eliminating the lamp101as a significant source of ozone and removing any ozone created by the interaction with the water as the water flows past the lamp surface104. Commonly, when the lamp surface104is comprised of quartz as is often the case, specialized treatment of the quartz envelope surrounding the lamp101is required to limit ozone production. The flowing water can eliminate this requirement.

In another embodimentFIG. 2shows how a system200can be used to provide treatment of the fluid202flowing over the lamp201with the photonic radiation produced by the lamp201. In the case where the fluid202is water, the system is useful in creating potable drinking water.FIG. 2shows a treatment system200that can be used for treating fluids wherein a fluid inlet204provides fluid202for treatment, the fluid202is exposed to the radiation from the lamp201, which is excited by the energy source203. As it passes through the system200, the fluid is exposed to the lamp201radiation and the treated fluid exits the system through outlet205.

FIG. 3Ashows another embodiment comprising an electrodeless lamp system300employing a photo-transparent shell306containing a fluid305and a lamp304surrounded by an energizing field307. The photo-transparent shell306could be transparent to a broad range of wavelengths or could be constructed or tuned to filter specific wavelengths of light produced by the lamp304. The field307is provided by an external energizing source such as a magnetron. The system300has a fluid inlet302and a fluid outlet303that permits fluid to pass through the system300. Irradiation of a target308outside the lamp304and flowing fluid305is accomplished by controlling the depth of the fluid305to allow the electrodeless lamp304output to substantially pass through the fluid305and photonically interact with an external target308. A reflective energy shield301is used to direct the energy of the system300toward a target308. The cross section view309designated inFIG. 3Bis taken through the middle of the apparatus300ofFIG. 3Aas indicated depicting how the photonic output of the lamp304passes through the fluid305and the energizing field307to illuminate the target308.

In this case the flowing fluid305stabilizes the output of the lamp304and provides a stable and precise source for ultraviolet radiation. Such sources are particularly useful in treating targets308that are sensitive to particular photon energies. One example is in the curing of polymeric compounds which are often only sensitive to a particular photon energy associated with the activation of chemical processes that occur in these materials.

FIG. 4AandFIG. 4Bportray another embodiment showing how a system400can be built to conform to the shape of a target408for irradiating it with ultraviolet radiation.FIG. 4Ais a cross section side view of the system400in which the electrodeless lamp401is deformed to focus its output radiation. InFIG. 4Athe jacket402around the flowing fluid403contains the entire lamp401. However, the lamp401is not exposed on every side to the excitation energy field404provided by an outside excitation source. Fluid still flows around the lamp401from inlet405to outlet406for regulating the temperature of the lamp401, and the exposure of the lamp401to the exciting field404is sufficient to ignite the lamp401and keep it lit while the flowing fluid403regulates its temperature. The advantage of the arrangement shown400,409inFIG. 4AandFIG. 4Bis that except for the thin temperature controlling layer provided by the flowing fluid403, the lamp401can be exposed directly to the target408and can be conformed to fit the target408. The cross end view409ofFIG. 4Btaken as indicated inFIG. 4Ashows this.

In this embodiment the arched nature of the lamp401along its long axis allows the lamp to conform to the target408shape shown. The apparatus400,409can be incased in a reflective energy shield407which contains the energizing field404and reflects it internally to the lamp401, and the shaped nature of the lamp401permits three dimensional treatment of the target408.

InFIG. 4Ba gap is shown between the target408shape and the inner side of the fluid flow channel for reasons of clarity. In use this gap can be eliminated and the jacket402comprising the outside of the temperature regulating fluid403channel can be placed in contact with the target408. Such an arrangement can lead to added robustness of an operating system400,409adding to mechanical stability while enhancing the level of radiation delivered to the target408and providing a three dimensional nature to the treatment of the target408.

The purification of water can be accomplished by passing water over an electrodeless lamp as discussed above. However, to provide adequately treated water certain minimum amounts of ultraviolet energy have to be delivered to the water. Further, the energy has to be delivered in a manner that will insure that the radiation can interact with the polluting bacteria.

Ultraviolet wavelength treatment methods sometimes are defeated by the phenomenon of shadowing. Shadowing occurs when intervening matter gets between the ultraviolet source and targeted matter interfering with the photons reaching the targeted matter. When fluids are being treated, this problem can be addressed by various methods such as introducing turbulence into the fluid flow stream. However, the following embodiment has been found to be effective in delivering the needed radiation permitting the treatment of solid objects as well as fluids. While the embodiment can be used to treat fluids, it can also be used to treat other items such as medical instruments, food, or other articles with electrodeless lamp produced radiation. The embodiment permits 360 degree radiation exposure over an extended length to a target region.

To provide the needed ultraviolet dose deliveryFIG. 5Ashows a cross section of an electrodeless lamp501system500formed in the shape of an elongated annular ring with the lamp surface510continuous and enclosing an excitable gas.

FIG. 5Bis a cross section view509of the apparatus500as seen through the indicated plane looking down the length of the tube to the left showing the inlet505at the far end of the apparatus.

The system is fitted with an inlet505and an outlet506, is enclosed in a reflective energy shield507, features an excitation energy field504provided by an external excitation energy source, not shown, and is contained by the reflective energy shield507.

The lamp envelope510enclosing the lamp's gas is comprised of an inner tube511and an outer tube512joined at the ends to form the annular ring. Usually, the tubes511,512forming the annular shaped electrodeless lamp501are round, though they need not be and in some embodiments are not. The interior of the lamp501, between the tubes511,512of the envelope510, is filled with a radiation producing gas and is excited by an external energy field504which is produced by an external energy source.

The shape of the electrodeless lamp501provides an axial channel508. The system500is configured to allow a temperature stabilizing fluid to flow over the lamp surface passing a fluid503, such as water, through the space between the inner photo-transparent shell502and the inner tube511and also through the space between the outer tube512and the outer photo-transparent shell502. The fluid stabilizes the operation of the lamp preventing thermal runaway and allowing selection of output wavelengths from the lamp501by controlling the temperature of the lamp. In this configuration the lamp can deliver enhanced doses of radiation. As material is moved through the channel508it is bombarded with the radiation from a full 360° and further benefits from axial scattering effects as the discharging gas in the lamp radiates through the inner portion of shell502delivering a shadow defeating dose of radiation. As discussed above, the flowing fluid503is maintained at a temperature and flow rate that insures that the lamp501is kept at the temperature needed to maintain its peak radiation output in the desired range.

The physical size of the channel508can be changed to accommodate varying needs for dosing the material that is passed through the channel508, and the material treated by the apparatus can comprise solid objects or fluids.

In one embodiment the shape of the lamp501can be flattened along the axial channel508so that the depth or thickness of the channel508is decreased and the effective energy density of radiation delivered to the material passing down the channel508is increased. The rest of the apparatus is modified to accommodate the lamp shape when this is done.

Though ultraviolet wavelengths are the ones generally desired for actinic water processing using electrodeless lamps, other gas mixtures than ultraviolet producing gas mixtures and their associated wavelengths can be used for other processing purposes. As discussed above, when the radiation desired is ultraviolet radiation, the ultraviolet producing gas mixture is often comprised of mercury and argon and is held at a specific temperature to produce peak output from the lamp at germicidal wavelengths.

In yet another embodiment stabilizing by liquids passing over the lamp solves another problem characteristic of electrodeless lamps. The presence of the fluid inhibits the exposure of the lamp envelope to free oxygen in the open atmosphere and limits the production of ozone from the lamp surface sweeping away any ozone that is created from the presence of free oxygen in the fluid. In this way the fluid passed over the surface of the lamp is used to control ozone production at the surface of the electrodeless lamp.

In another embodimentFIGS. 6A,6B and6C show how axial flow down an annular shaped electrodeless lamp can be made into a treatment apparatus600for stabilizing electrodeless lamp operation to provide desired wavelengths from the lamp and at the same time provide effective fluid treatment with minimal shadowing. For radiation transmission purposes various materials can be used to form the sides of electrodeless lamps depending on the radiation transmission needs. As mentioned above, where water is being purified using electrodeless lamps and the gas in the lamp comprises mercury and argon, the lamps are usually made of quartz. As shown inFIG. 6A, a lamp600comprised of quartz can be fabricated by using an inner tube601and an outer tube602joining them together to form a gas filled envelope603to provide the axial channel604.

FIG. 6Bshows a cross section605through the indicated plane and looking down the length of the apparatus600, andFIG. 6Cis a perspective view606of the apparatus.

In use a temperature stabilizing fluid can be passed over the surfaces of the envelope to control the temperature of the lamp603created by joining the end of the outer tube602with the inner tube601to form the lamp603. In this embodiment the fluid passed over the lamp is treated with the radiation from the lamp at the same time that it is stabilizing the temperature of the lamp. For example, the apparatus can be the core of a water treatment system.

While the lamp geometry allows for greatly increased surface area for production of desirable photonic wavelengths. It is desirable to maintain the thickness or distance between the inner tube601and the outer tube602at less than about 13 mm (0.51 inch). This reduces self-absorption of desirable photons which occurs when the photons interfere with each other inside the envelope.

If more output energy or photons are needed, one can increase the diameter of the inner and outer lamp walls to further increase surface area for photonic output, while still maintaining an about 13 mm (0.51 inch) annular envelope thickness. Increasing the thickness of the annular envelope does not proportionally increase photonic output levels.

In another embodiment as shown inFIG. 7, the thickness of the sides of the annular envelope can be varied.FIG. 7is a section of an annular envelope700shown in section cut along the axis of the envelope. In the drawing the outer tube701appears folded to vary the thickness of the annular envelope700along the length of the lamp thus controlling the plasma flow and energy distribution throughout the lamp. Combinations of lamp length and annular region thickness along the length of the lamp can be used to optimize the lamp's performance with regard to radio frequency power source frequency and desired photonic output and intensity. Additionally, varying the annular region thickness, as shown inFIG. 7, provides additional surface area, further promoting the production of photons at desirable wavelengths and substantially limiting self-absorption.

To maximize the efficiency of output as discussed above it is best to maintain the distance between the inner and outer tube at less than about 13 mm (0.51 inch). However, the pinching effect of the thinner regions703along the envelope700cause intense ultraviolet output associated with the thinner regions703. There are numerous occasions when such intense localized output can be advantageous.

In one example the distance between the pinched regions703can be reduced so that there are many pinched regions703close together along the length of the tube providing relatively intense ultraviolet output. An envelope700made in this way can be useful in polymer curing operations or when the purpose of the tube is to maximize ozone output.

If only the regions of intense ultraviolet output703are desired, one can make the thickness of the envelope between the pinches704arbitrarily large. This has the effect of increasing the relative output of the pinched regions703by keeping energy in the envelope700where it is thick704because of self absorption in those regions while making that energy available to the thinner regions703for relatively efficient photon emission.

To make the discussion simplerFIG. 7has shown only the outer tube folded. However, either or both of the tubes701,702could be folded to make pinched regions and produce enhanced emission from them.

In yet another embodiment a conductive wire or wires can be inserted within the annular envelope of the lamp disposed along the length of the lamp. For example, a filamentary piece of tungsten wire could be used. A current can be induced in the wire as energy is delivered to the wire by the radio frequency energy power source. The wire carries this energy along its length for distribution to the plasma field. The wire also provides thermal energy to provide sufficient heating of the fill to keep it in a gaseous state. This is particularly useful when operating the lamp in cool or cold environments where sufficient power to start the lamp is otherwise unavailable. The length of the wire can be varied to tune it to the specific radio power frequency needed for optimizing current inducement in the wire.

In an exemplary embodiment a 20″ lamp, similar to the lamp ofFIG. 6, can use a tungsten wire of about 0.020″ diameter (for mechanical strength) and a length of about 9.9″ when powered by radio frequency energy at about 2.5 GHz. However, the length of the wire can be varied by multiples of 31.43 mm +/−3.175 mm (1.2375 inches +/−0.125 inches) for power sources generating radio frequency energy at about 2.5 GHz. In other words the length of the wire filament for a 2.5 GHz power source can be as short as 1.2375 inches and as long as a multiple of 1.2375 inches depending on the overall length of the lamp's envelope.

In another embodiment the lamp is energized by a magnetic field. The presence of the wire in the lamp permits an external magnetic field to be much more effectively coupled to the lamp for energy delivery to the gas fill of the lamp than a magnetic field can be coupled to the fill of the lamp without such a wire. For this reason, the presence of the wire permits relatively efficient delivery of magnetic field energy to the lamp exciting the fill within the lamp.

FIG. 8shows another embodiment using an apparatus similar to that provided inFIG. 6. InFIG. 8the assemblage800is used to provide a water purification apparatus800for actinically treating water for potability. A tube shaped manifold or processing chamber801open only on one end is used. Inside the manifold801is placed an electrodeless lamp802that can be, but need not be, centered in the manifold801. The electrodeless lamp802has the annular shape discussed above with a central channel803for passing water through the lamp802. Head space804is allowed at the closed end of the manifold801allowing water to flow around the end of the electrodeless lamp802.

A header805is attached to the open end of the manifold801. The header805has a water inlet806, a water outlet807and a seal808at the end of the lamp802adjacent the header805to prevent water passing through the channel803from mixing with water passing over the outside of the lamp802.

The apparatus800allows water to pass through the manifold801such that it passes through both a space809between the outside of the lamp802and the inside of the manifold801and through the channel803of the lamp to receive an effective dose of lamp802radiation and to keep the lamp802at the desired operating temperature to provide germicidally effective radiation.

In another embodiment as shown inFIG. 9, an external energizing source905is used for energizing an electrodeless lamp903. The apparatus900ofFIG. 9shows a lamp903inserted in a microwave tuned cavity901which is used for exciting the lamp903since it is inside a manifold902. It should be noted that the excitation energy source905does not have to completely enclose the lamp for the lamp to provide desired ultraviolet radiation. A small portion of the lamp903, when exposed to the exciting energy source, can be effective in lighting or driving the whole lamp903and providing ultraviolet radiation from the entire lamp surface.

In operation the water flows into the inlet908of the header assembly914, through either the channel907or the side space904, depending on inlet908and outlet909arrangement, through the head space910and back out through either the channel907or the side space904depending on inlet908and outlet909arrangement. As presented inFIG. 9the water flows in the inlet908, through the side space904, then through the channel907and out the outlet909. As indicated above, the flow direction could be reversed. The temperature and flow rate of the water are adjusted externally to maintain the desired peak in electrodeless lamp903radiation.

The thickness of the side space904is chosen to insure that any needed actinic treatment by the lamp emission in the side space is effective. However in many but not all instances, the high intensity treatment of the water flowing through the channel907is sufficient to purify water flowing through the apparatus900.

The apparatus900described can also be used for treating fluids other than water and for purposes other than water purification. For example, a flowing reactionable polymer stream can be partially reacted by choosing and maintaining the appropriate output wavelength from the electrodeless lamp903. Such treatment could be used to regulate the viscosity of the flowing polymer stream.

It is found that the most effective thicknesses for the side space904when using commonly available magnetrons similar to those used in ordinary microwave ovens are up to about 6.35 mm (0.25 inch). Higher power radio frequency sources allow a thicker side space904for effective fluid treatment according to the output capabilities of the electrodeless lamp903and the requirements of the shadowing situation.

In some embodiments it is desirable to use multiple electrodeless lamps in combination. It should be noted that electrodeless lamps can be grouped and can be driven by other lamps in contact with or close by each other. In this case the excitation source for the electrodeless lamps can be other electrodeless lamps with initial excitation arising from various energy providing sources.

Those skilled in the art will realize that this invention is capable of embodiments different from those shown and described. It will be appreciated that the detail of the structure of this apparatus and methodology can be changed in various ways without departing from the scope of this invention. Accordingly, the drawings and detailed description of the preferred embodiments are to be regarded as including such equivalents as do not depart from the scope of the invention.