Abstract:
Methods and systems are provided for enhancing the ultraviolet output of a water disinfection apparatus by: (i) maintaining the source of the U V radiation at a stable operating temperature and (ii) facilitating an efficient transfer of microwave energy to the source of the UV radiation.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention is in (he field of water disinfection apparatus, in which water to be disinfected or sterilized flows past an ultraviolet (UV) light source. 
       BACKGROUND 
       [0002]    The electric power applied to energize mercury lamps in water treatment systems is convened into heat and ultraviolet: (UV or germicidal UV light. The heat generated impacts the performance of the water treatment system by reducing die UV output. Current water treatment systems use a system of importing ambient air through a filter; the air passes the lamps and forces excess hot air through air vents. Since the temperature of ambient air may change over a large range/the UV output of the water treatment systems may be affected significantly. 
         [0003]    Current water treatment systems employ microwave energy to excite the source of UV radiation. One problem with such systems is that it is difficult to efficiently provide sufficient excitation energy to the UV source and it is also difficult to effectively transfer that energy to the water to be treated. It is therefore, difficult to arrange apparatus for high throughput industrial water treatment purposes. 
       SUMMARY 
       [0004]    One or more embodiments of the present invention may be used to enhance UV water disinfection by controlling the temperature of the UV light source and adjusting for impedance mismatch of a microwave generator assembly feeding the UV light source. 
         [0005]    The UV light source may comprise an ultraviolet lamp module which is at least partially submerged within flowing water to be treated. In one embodiment, the ultraviolet lamp module is vertically oriented in a channel, which., in uses defines the flow of water to be treated. However, the ultraviolet lamp module may, in other embodiments, be oriented in other planes and/or disposed in a chamber. The ultraviolet lamp module further comprises a plurality of lamps arranged in a staggered manner. In moving fluids, energy may be dissipated due to friction and turbulence. This dissipation of energy is called head loss. By staggering the lamps, head loss may be reduced, and mixing of the ultraviolet radiation with the water to be disinfected may be improved. Each of the ultraviolet lamps may further comprise one or more ultraviolet lamp bulbs (also referred herein as ultraviolet bulbs); one or more microwave generator assemblies, each microwave generator assembly comprising a microwave generator; a circular waveguide enclosing the one or more ultraviolet lamp bulbs, and an outer quartz tube enclosing the circular waveguide and ultraviolet lamp bulbs. 
         [0006]    Each microwave generator assembly further comprises a power supply, a magnetron, a cooling system utilizing water or air, a transition to a rectangular waveguide, where the rectangular waveguide functions as a transmission line for the microwave, protective means such as thermal cutouts, and a housing enclosing the components. The microwave generator assembly may be disposed above the outer quartz tubes. 
         [0007]    The circular waveguide is microwave-opaque and has a shape, and size that wholly surrounds the one or more ultraviolet lamp bulbs so as to substantially contain the microwaves within the waveguide. The circular waveguide is made of an electrically conductive mesh having perforations smaller than the size of microwave wavelengths to substantially reduce microwave leakage. 
         [0008]    The microwave generator provides microwave energy to excite the ultraviolet bulb. The ultraviolet bulbs emit ultraviolet radiation, at or near the germicidal wavelength of 253.7 nm, which radiates out through the ultraviolet lamp unit to irradiate, and thereby disinfect, the water in the channel. 
         [0009]    Embodiments of the present invention generally comprise a temperature control system and means for adjusting a microwave impedance mismatch. 
         [0010]    Embodiments of the temperature control system generally comprise a recirculating fan, an air supply plenum, a heat exchange unit submerged in the body of water being disinfected, a collector plenum, a hot air collector plenum, and a programmable control unit. 
         [0011]    A desired operating temperature of the ultraviolet lamp bulbs is used as the input for a programmable control unit of the temperature control system. 
         [0012]    The recirculating fan forces air through the heat exchanger via the air supply plenum. The air supply plenum may be adapted to store a fixed volume of air. As the air flows through the heat exchange unit, it is cooled by the flowing water in contact with the tubes of the heat exchange unit. The cooled air feeds into the collector plenum and is subsequently distributed to the outer quartz tubes enclosing the ultraviolet lamp bulbs. The air cools the ultraviolet lamp bulbs as it flows through the quartz tubes. Upon exiting the quartz tubes, the air temperature is measured and this information is transmitted to the programmable control unit. The programmable control unit stores and analyzes this information, and based on the analysis, determines the deviation of the measured temperature from the desired temperature, and makes adjustments to a rate and/or volume of air flowing through the heat exchange unit. The analysis and determination of the deviation may be automated. 
         [0013]    In one embodiment, the programmable control unit may adjust the recirculating fan speed to reduce the determined deviation. In another embodiment, the programmable control unit reduces the determined deviation by throttling the air inlets of the tubes of the heal exchanger by using a motor-driven mechanical damper. 
         [0014]    One or more embodiments of the means for adjusting the microwave impedance mismatch generally comprise impedance matching devices such as a matching block or a matching ring or both. 
         [0015]    Microwave energy travels from the microwave generator into a rectangular waveguide, to the ultraviolet bulbs, via a circular waveguide. This transition from rectangular to circular waveguides creates an impedance mismatch, which reduces the efficiency of the microwave energy transfer. To adjust for this impedance mismatch, an embodiment of the present invention may comprise a matching block. The matching block is generally disposed at a plane intersecting the direction of travel of the microwave energy as it transitions from the rectangular waveguide to the circular waveguide. 
         [0016]    Another microwave impedance mismatch occurs between a first portion and a second portion of the circular waveguide, due to the transition of the microwave energy from traveling through the completely hollow portion of the circular waveguide immediately after exiting the microwave generator to traveling through the portion of the circular waveguide containing the ultraviolet lamp bulb. This impedance mismatch creates a disruption that negatively impacts the efficiency of the microwave energy transfer to the ultraviolet lamp bulb. To adjust for the impedance mismatch, a matching ring is utilized. The matching ring may influence the microwave field in such a way as to reduce the disruption caused by the impedance mismatch. 
         [0017]    In yet another embodiment, the present invention may comprise both a matching block and a matching ring to adjust for the two impedance mismatches described above. 
         [0018]    Embodiments of the temperature control system and the means for controlling microwave impedance mismatch described herein may be used to achieve optimal UV water disinfection by controlling certain aspects of its involved processes. 
         [0019]    These and other embodiments of the invention are described in detail with reference to the following drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIGS. 1   a  and  1   b  show perspective views of water disinfection apparatus according to certain embodiments of the present invention. 
           [0021]      FIGS. 2   a  and  2   b  show perspective views of a throttle mechanism according one embodiment of the present invention. 
           [0022]      FIG. 3   a  is a perspective view of a means for adjusting a microwave impedance mismatch having a matching block according to one embodiment of the present invention. 
           [0023]      FIG. 3   b  is a perspective view of a matching block according to one embodiment of the present invention. 
           [0024]      FIG. 4   a  is a perspective view of a means for adjusting a microwave impedance mismatch having a matching ring according to one embodiment of the present invention. 
           [0025]      FIG. 4   b  shows a top view and a section view of a matching ring according to one embodiment of the present invention. 
           [0026]      FIG. 5  is a perspective view of a means for adjusting a microwave impedance mismatch having a matching block and a matching ring according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]      FIG. 1   a  depicts an exemplary water disinfection apparatus  100  comprising a closed-loop temperature control system  102  and an ultraviolet lamp module  103 . The temperature control system  102  comprises a recirculating fan  104 , an air supply plenum  108 , a plurality of heat exchange tubes  112 , an air collector plenum  116 , a hot air collector plenum  110 , at least one temperature sensor  124 , and a programmable control unit  128 . The ultraviolet lamp module  103  comprises a plurality of lamps, each lamp having one or more ultraviolet lamp bulbs  140 ; one or more microwave generators  152 , the microwave generators  152  feeding a rectangular waveguide  142 ; a circular waveguide  144  enclosing the one or more ultraviolet lamp bulbs  140 ; and an outer quartz tube enclosing the circular waveguide  144  and ultraviolet lamp bulbs  140 . The ultraviolet lamp module  103  preferably comprises between 2 to 8 lamps. 
         [0028]    The recirculating fan  104  may be attached to the supply plenum  108 . The recirculating fan  104  forces air from the supply plenum  108  into the plurality of heat exchange tubes  112 . The plurality of heat exchange tubes  112  may be arranged in a linear array substantially perpendicular to a linear array of quartz tubes  120 . In some embodiments, the heat exchange tubes  112  may comprise two sets of linear arrays substantially parallel to each other and perpendicular to the linear array of quartz tubes  120 . In this embodiment, the two linear arrays of heat exchange tubes  112  are disposed at opposite ends of the linear array of quartz tubes  120 . In one embodiment, only one of the two linear arrays of heat exchange tubes  112  is a component of the temperature control system  102 . The linear array of heat exchange tubes  112  that is not a component of the temperature control system  102  may regulate the temperature of another aspect of the water disinfection apparatus  100 . For example, the linear array of the heat exchange tubes  112  that is not a component of the temperature control system  102  may be used to cool the micro wave generators. 
         [0029]    In one embodiment, the linear array of heat exchange tubes  112  used in the temperature control system  102  comprises  16  heat exchange tubes  112 . In another aspect, the heat exchange tubes  112  are made of stainless steel grade  316 . However, the number of heat exchange tubes and the material used to manufacture them may vary in other embodiments. The recirculating fan  104  forces air through the air inlets  132  of the plurality of heat exchange tubes  112  via the supply plenum  108 . 
         [0030]    The forced air travels through the heat exchange tubes  112 , which are at least partially submerged in flowing water  136 . The air may flow in either longitudinal direction of the heat exchange tubes  112 . Contact between the outer surfaces of the heat exchange tubes  112  and the flowing water  136  causes heat transfer as the temperature of the air inside the heat exchange lubes  112  and the temperature of the flowing water  136  approach thermal equilibrium. Here, the air entering the heat exchange tubes  112  generally has a higher temperature than that of the flowing water  136  in contact with the outer surfaces of the heat exchange tubes  112 . Thus, heat from the air is transferred to the flowing water  136  as the air passes through the heat exchange tubes  112 , and the air is cooled. 
         [0031]    The cooled air exits the heat exchange tubes  112  and feeds into the collector plenum  116 . The collector plenum  116  is a reservoir attached to the bottom of at least one quartz tube  120 . The collector plenum  116  acts to distribute the air received from the heat exchange tubes  112  into the at least one quartz tube  120 . 
         [0032]    As the air passes through the quartz tubes  120 , heat is transferred from the ultraviolet lamp bulbs  140  to the air, thereby cooling the ultraviolet lamp bulbs  140 . 
         [0033]    The water disinfection apparatus  100  may comprise a plurality of cylindrical quartz tubes  120 , each defining an elongate axis, arranged in a side-by-side array. Each quartz tube  120  may be made of an ultraviolet transparent quartz glass, and acts as a housing for an ultraviolet lamp bulb  140  and a circular waveguide  144 . The waveguide  144  is an electrically conductive mesh cylinder that surrounds the ultraviolet lamp bulb  140 . The upper end  148  of the quartz tube  120  is disposed at a transition from a rectangular waveguide  142 , fed by the microwave generator  152 , to a circular waveguide  144 . Microwave energy from the microwave generator  152  is directed to the ultraviolet lamp bulb  140 , guided via the circular waveguide  144 . The ultraviolet lamp bulb  140 , excited by the microwave energy, emits ultraviolet radiation, which radiates out through the quartz tube  120  to irradiate, and hence disinfect, the water  136  flowing past. 
         [0034]    The air is exhausted proximate the upper end  148  of the quartz tube  120  through air outlet  156  and feeds into the hot air collector plenum  110 , which directs the hot air back to the recirculating fan  104 . A temperature sensor  124  disposed upstream of the recirculating fan  104  inlet(s) measures the temperature of the air exiting the air outlet  156 . In one embodiment, a 3 wire RTD may be used as the temperature sensor to obtain a measurement. 
         [0035]    The measurement obtained by the temperature sensor  124  is die feedback signal of the temperature control system  102 , and is fed to the programmable control unit  128 . The programmable control unit  128  determines the difference between the input signal, which is the desired “setpoint” temperature of the quartz tube  120 , and the feedback signal, the difference being the error. The programmable control unit  128  reduces the error to bring the output of the temperature control system  102  to the setpoint temperature. By this means, a constant ultraviolet lamp bulb  140  temperature can be maintained. 
         [0036]    The system described is a sealed, fixed-volume, closed-circuit system. Thus, air is recycled through the water disinfection apparatus  100 . Because the water disinfection apparatus  100  does not introduce new air from the atmosphere to replenish the system, no air fillers are necessary. As the hot air exits the air outlet  156 , it enters the hot air collector plenum  110 , from where it is directed to the recirculating fan  104  inlet(s) and forced by the recirculating fan  104  through the air supply plenum  108  into the heat exchange tubes  112 , thereby beginning a new cycle. 
         [0037]    In one embodiment of the temperature control system  102 , the programmable control unit  128 , upon determining an error, adjusts the speed of the recirculating fen  104  to affect the rate at which air is forced through the heat exchange tubes  112 . In one embodiment, the programmable control unit  128  comprises a three-term process controller that may be used to control the recirculating fan speed electronically with a variable speed motor driver interface. A low recirculating fan speed corresponds with a low rate at which air passes through the heat exchange tubes  112 . The longer the air takes to flow through the heat exchange tubes  112 , the more time it may have to transfer heat to the cooler, flowing water  136  in contact with the outer surfaces of the heat exchange tubes  112 . 
         [0038]      FIG. 1   b  depicts another embodiment of the temperature control system  102  having a first set of heat exchange tubes  112  for maintaining a stable ultraviolet lamp bulb  140  temperature as previously described in relation to  FIG. 1   a  and a second set of heat exchange tubes  168  in a sealed, closed-circuit system for cooling the microwave generators  152 . A second recirculating fan  160  forces air through the second set of heat exchange tubes  168  via a second supply plenum  164 . As the air flows through the second set of heat exchange lubes  168 , heat is dissipated from the air to the flowing water in contact with the outer surfaces of the second set of heat exchange tubes  168 , thereby cooling the air. The cool air exits the second set of heat exchange tubes  168  and enters a cool air return plenum  172 , which transports the cool air to a hood  180  containing the microwave generators  152 . The microwave generators  152  dissipate heal lo the cool air, thereby cooling the microwave generators  152  and heating the air. The hot air is returned to the second recirculating fan  160 , thereby beginning a new cycle. 
         [0039]    In another embodiment of the temperature control system  102 , the rate at which air in the heat exchange tubes  112  loses heat to the flowing water  136  is affected by throttling the air inlets  132  of the heat exchange tubes  112 , as shown by  FIGS. 2   a  and  2   b.  The programmable control unit  128 , adjusting for error, determined as previously described, controls a throttle mechanism  200 , comprising a motor  204  that drives a mechanical damper  208  over and across the air inlets  132  of the heat exchange tubes  112 . The mechanical damper  208  may be a plate having a width and a length sufficient to effectively obstruct air from flowing into the air inlets  132  of heat exchange tubes  112 . In one aspect, the mechanical damper  208  is made of stainless steel. In other aspects, the mechanical  208  may be made of, for example, aluminum, ultra-high-molecular-weight polyethylene (UHMW), or any other material suitable to restrict the air flow from the recirculating fan  104  to the air inlets  132  of the heat exchange tubes  112 . In some embodiments, the face of the mechanical damper  208  restricting the air flow may have dimensions of 60×550 mm. 
         [0040]    The motor  204  drives the mechanical damper  208  to progressively cover the air inlets  132  of the heat exchange rubes  112 , thereby reducing the number of heat exchange tubes  112  through which air may flow. Thus, similar to varying the recirculating fan speed, the temperature control system  102  may throttle the air inlets  132  of the heat exchange tubes  112  to regulate the heat transfer occurring within the heat exchange tubes  112  and effectively maintain a constant temperature of the ultraviolet lamp bulbs  140  within the quartz tubes  120 . 
         [0041]    On the first power-up of the temperature control system  102 , the mechanical damper  208  is disposed at an arbitrary position proximate the air inlets  132  of the heat exchange tubes  112 . The programmable control unit  128  may generate a signal that drives the mechanical damper  208  over the air inlets  132  of the heat exchange tubes  112 , progressively covering them and restricting air flow through the heat exchange tubes  112 , until the setpoint temperature is reached. Once the setpoint temperature is reached, the position of the mechanical damper  208  will be continuously controlled by the programmable control unit  128  to maintain the setpoint temperature. If power to the temperature control system  102  is interrupted the position of the mechanical damper  208  will be retained until power is resumed. 
         [0042]    Temperature sensors (not shown) may be disposed proximate the air inlets  132  of the heat exchange tubes  112  rather than at the air outlets  156  of the quartz tubes  120 . Thus, the temperature control system  102  receives a feedback, signal of a temperature measurement before the air flows through the heat exchange tubes  112 . 
         [0043]    In yet another embodiment, the temperature control system  102  is an open-loop control system, wherein the programmable control unit  128  does not receive a feedback signal corresponding with a temperature measurement, and thus does not make adjustments to account for deviations from the desired temperature. 
         [0044]    Referring now to  FIG. 3   a,  a means for adjusting microwave impedance mismatch  300  comprises a matching block  304 . The ultraviolet light source comprises an elongate quartz tube  120  enclosing at least one ultraviolet lamp bulb  140  and defining an elongate lamp axis  308 ; and a microwave, generator  152  for exciting the at least one ultraviolet lamp bulb  140 . 
         [0045]    The microwave generator  152  provides microwave energy to excite the ultraviolet lamp bulb  140 . Suitably, the microwave generator  152  comprises a magnetron or other suitable microwave producing device. 
         [0046]    Microwave energy travels from the microwave generator  152  into a rectangular TE 10  waveguide mode  142 . The waves then transition into an operating TE 11  circular waveguide mode  144  toward the ultraviolet lamp bulb  140 . Such a transition from a rectangular TE 10  waveguide mode  142  to a circular TE 11  waveguide mode  144  creates a microwave impedance mismatch, negatively impacting the efficiency of microwave energy transfer, and thus, negatively impacting the overall efficiency of the water disinfection apparatus  100 . 
         [0047]    The matching block  304  may be a rectangular-shaped plate, as illustrated in  FIG. 3   b , and acts as a matching device allowing a direct and immediate cross section change from rectangular TE 10   142  to circular TE 11   144  waveguide modes. The matching block  304  is disposed at the end of the rectangular TE 10  waveguide  312  and its length is approximately or less than a quarter of the mode wavelength. In one embodiment, there is one matching block  304  for every microwave generator  152 . In other embodiments, more than one matching block  304  per microwave generator  152  may be used. 
         [0048]    In one aspect of the present invention, the matching block  304  is made of aluminum. However, in other embodiments, the matching block  304  may be made of another type of metal or carbon. 
         [0049]    The longitudinal ends  320  of the matching block  304  may be attached to the sides of the rectangular waveguide  316  having the major ‘a’ dimension, as illustrated in  FIG. 3   a.  The matching block  304  may be disposed at a short distance away from a side of the rectangular waveguide  316  having the ‘b’ dimension, as illustrated in  FIG. 3   a.  In one embodiment, the matching block is disposed at a distance of less than ‘a’/2 away from the ‘b’ side. The matching block  304  is typically shorter than a quarter mode wavelength. In a standard WG340 (43×86 mm) waveguide in the 2450 MHz ISM band, the quarter mode wavelength is approximately 43 mm. In one embodiment, the matching block  304  is square shaped. 
         [0050]    The matching block  304  may be affixed to the end of the rectangular TE 10  waveguide  312  by either capacitive or direct contact. In one embodiment, the matching block  304  may be affixed to the end of the rectangular TE 10  waveguide  312  by using a special high temperature, aluminum tape, which is then a capacitive contact with such a small gap that the microwave impedance is in practice a short-circuit. In another embodiment, the matching block  304  may be welded to the end of the rectangular TE 10  waveguide  312 . 
         [0051]    A method of determining an appropriate position of the matching block  304  involves a person skilled in the art first using microwave modeling software to determine the microwave impedance mismatch of the rectangular TE 10  waveguide  142  to circular TE 11  waveguide  144  transition without a matching block  304 . A matching block  304  having a longitudinal length of approximately a quarter TE 10  mode wavelength (43 mm) is then introduced to the end of the rectangular TE 10  waveguide  312  at a distance of approximately 2 to 3 mm from a side having a ‘b’ dimension. The microwave modeling software is then run again in order to determine the microwave impedance mismatch of the rectangular TE 10  waveguide  142  to circular TE 11  waveguide  144  transition with the matching block  304 . The first impedance mismatch of the transition without the matching block  304  is compared to the second impedance mismatch of the transition with the matching block  304  to deduce whether or not the impedance mismatch is improving. The matching block  304  is iteratively repositioned at various distances away from the ‘b’ side. After each repositioning, the modeling software is used to determine whether the impedance mismatch is improved, in this manner, an optimal position for the matching block  304  is determined. 
         [0052]      FIG. 4   a  illustrates another embodiment of a means for adjusting microwave impedance mismatching  400  comprising a matching ring  404 . The ultraviolet light source comprises an elongate quartz tube  120  enclosing at least one ultraviolet lamp bulb  140  and defining an elongate lamp axis  308 ; and a microwave generator  152  for exciting the at least one ultraviolet lamp bulb  140 . 
         [0053]    The distance between the magnetron&#39;s antenna (not shown) and the ultraviolet lamp bulb  140  is performance-sensitive as the microwave field is typically disrupted when it reaches the ultraviolet lamp bulb  140 . The disruption is caused by an impedance mismatch between two portions, a first portion  408  and a second portion  412 , of the circular TE 11  waveguide  144  previously described in relation to  FIG. 1   a.  The first portion  408  of the circular TE 11  waveguide  144  is defined as the portion through which the microwave energy travels before reaching the ultraviolet lamp bulb  140 . The second portion  412  of the circular TE 11  waveguide  144  is defined as the subsequent portion containing the ultraviolet light bulb  140 . This disruption reflects microwave energy back to the microwave generator  152 , reducing the efficiency of microwave energy transfer, and thus, reducing the overall efficiency of the water disinfection apparatus  100 . 
         [0054]    The matching ring  404  may be an annular-shaped matching reactance element, as illustrated in  FIG. 4   b,  disposed inside the elongate lamp tube  120  and may be incorporated into the top of the lamp cassette  416 , the axis of the matching ring  404  coincident with the elongate lamp axis  308 . 
         [0055]    In one embodiment, the matching ring  404  may be made of pure aluminum. In another embodiment, the matching ring  404  may be made of nickel-plated brass. Other embodiments of the matching ring  404 , however, may be made of any other material of low resistivity suitable for improving the impedance mismatch described above, without resulting in significant self-heating by the microwave currents in it. 
         [0056]    The distance of the matching ring  404  from the ultraviolet lamp bulb  140  and the dimensions of the matching ring  404  are two parameters that may influence the microwave field in such a way as to reduce disruption. These parameters are determined on a load-by-load basis. Different types of ultraviolet lamp bulbs  140  may require different values for these parameters. The matching ring  404  may be disposed less than a quarter free space wavelength above the top of the crown of the ultraviolet lamp bulb  140 . In one embodiment, the matching ring  404  may be disposed approximately 6 mm above the top of the crown of the ultraviolet lamp bulb  140 . The inner diameter of the matching ring  404  may range from approximately 20 mm to 40 mm. In a preferred embodiment, the matching ring  404  may have an inner diameter of 28 mm and a square cross section having dimensions of 1.5×1.5 mm. In yet another embodiment, the matching ring  404  has a round cross section. The distance of the matching ring  404  from the ultraviolet lamp bulb  140  and the dimensions of the matching ring  404  may vary in other embodiments. 
         [0057]    A method of determining an appropriate, position of the matching ring  404  involves a person skilled in the art first using microwave modeling software to determine the microwave impedance mismatch of the transition between the first portion  408  and the second portion  412  of the circular TE 11  waveguide  144  without a matching ring  404 . A matching ring  404  is introduced into the circular TE 11  waveguide  144  above and proximate to the ultraviolet lamp bulb  140 . The microwave modeling software is then run again in order to determine the microwave impedance mismatch with the inclusion of the matching ring  404 . The first impedance mismatch of the transition without the matching ring  404  is compared to the second impedance mismatch of the transition with the matching ring  404  to deduce whether or not the impedance mismatch is improving. The matching ring  404  is iteratively repositioned at various distances away from the ultraviolet lamp bulb  140 . After each repositioning, the modeling software is used to determine whether the impedance mismatch is improved. In this manner, actual experiments with microwave power in a test set-up are conducted for verification and possible fine adjustments allow For the determination of an optimal position for the matching ring  404 . 
         [0058]    In yet another embodiment, the present invention may comprise both a matching block  304  and a matching ring  404 , as illustrated in  FIG. 5 , to adjust for the two impedance mismatches described above. 
         [0059]    In particular embodiments, the temperature control system and the means for adjusting the impedance mismatch may be combined. The means for adjusting the impedance mismatch may comprise a matching block or a matching ring or both. 
         [0060]    The use of the word “exemplary” in this disclosure is intended to mean that the embodiment or element so described serves as an example, instance, or illustration, and is not necessarily to be construed as preferred or advantageous over other embodiments or elements. The description of the various exemplary embodiments provided above is illustrative in nature and is not intended to limit the invention, its application, or uses. Thus, variations that do not depart from the gist of the invention are, intended to be within the scope of the embodiments of the present invention. Such variations are not to be regarded as a departure from the spirit and scope of the present invention. 
         [0061]    While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that, follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.