Patent Publication Number: US-2021161581-A1

Title: Devices, systems and methods for enhancing physiological effectiveness of medical cold plasma discharges

Description:
PRIORITY 
     This application claims priority to U.S. Provisional Patent Appl. No. 62/400,251, filed Sep. 27, 2016, entitled “DEVICES, SYSTEMS AND METHODS FOR ENHANCING PHYSIOLOGICAL EFFECTIVENESS OF MEDICAL COLD PLASMA DISCHARGES”, the contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     Field 
     The present disclosure relates generally to electrosurgery and electrosurgical systems and apparatuses, and more particularly, to devices, systems and methods for enhancing physiological effectiveness of medical cold plasma discharges. 
     Description of the Related Art 
     High frequency electrical energy has been widely used in surgery and is commonly referred to as electrosurgical energy. Tissue is cut and bodily fluids are coagulated using electrosurgical energy. 
     Electrosurgical instruments generally comprise “monopolar” devices or “bipolar” devices. Monopolar devices comprise an active electrode on the electrosurgical instrument with a return electrode attached to the patient. In monopolar electrosurgery, the electrosurgical energy flows through the active electrode on the instrument through the patient&#39;s body to the return electrode. Such monopolar devices are effective in surgical procedures where cutting and coagulation of tissue are required and where stray electrical currents do not pose a substantial risk to the patient. 
     Bipolar devices comprise an active electrode and a return electrode on the surgical instrument. In a bipolar electrosurgical device, electrosurgical energy flows through the active electrode to the tissue of a patient through a short distance through the tissue to the return electrode. The electrosurgical effects are substantially localized to a small area of tissue that is disposed between the two electrodes on the surgical instrument. Bipolar electrosurgical devices have been found to be useful with surgical procedures where stray electrical currents may pose a hazard to the patient or where other procedural concerns require close proximity of the active and return electrodes. Surgical operations involving bipolar electrosurgery often require methods and procedures that differ substantially from the methods and procedures involving monopolar electrosurgery. 
     Gas plasma is an ionized gas capable of conducting electrical energy. Plasmas are used in surgical devices to conduct electrosurgical energy to a patient. The plasma conducts the energy by providing a pathway of relatively low electrical resistance. The electrosurgical energy will follow through the plasma to cut, coagulate, desiccate, or fulgurate blood or tissue of the patient. There is no physical contact required between an electrode and the tissue treated. 
     Electrosurgical systems that do not incorporate a source of regulated gas can ionize the ambient air between the active electrode and the patient. The plasma that is thereby created will conduct the electrosurgical energy to the patient, although the plasma arc will typically appear more spatially dispersed compared with systems that have a regulated flow of ionizable gas. 
     Atmospheric pressure discharge cold plasma applicators have found use in a variety of applications including surface sterilization, hemostasis, and ablation of tumors. Often, a simple surgical knife is used to excise the tissue in question, followed by the use of a cold plasma applicator for cauterization, sterilization, and hemostasis. Cold plasma beam applicators have been developed for both open and endoscopic procedures. 
     SUMMARY 
     Devices, systems and methods for enhancing physiological effectiveness of medical cold plasma discharges are provided. 
     In one aspect of the present disclosure, an electrosurgical apparatus is provided including: An electrosurgical apparatus comprising: a first fluid flow housing including a proximal end, a distal end, a first gas port, and a hollow interior, the first gas port configured to provide a first gas to the hollow interior, such that, the first gas flows through the hollow interior and is provided to the distal end of the first fluid flow housing; a second fluid flow housing including a proximal end, a distal end, a second gas port, and a hollow interior, the second fluid flow housing coaxially disposed over the first fluid flow housing, the second gas port configured to provide a second gas to the hollow interior of the second fluid flow housing, such that, the second gas flows through the hollow interior and is provided to the distal end of the second fluid flow housing; and an electrode disposed through the hollow interior of the first fluid flow housing, the electrode including a distal tip and configured to receive electrosurgical energy from an electrosurgical generator, such that, when the first gas passes over the distal tip of the electrode and the electrode receives electrosurgical energy, the first gas is at least partially ionized to generate a plasma discharge beam, the plasma discharge beam exiting the distal end of the first fluid flow housing, wherein the distal end of the second fluid flow housing is configured to inject the second gas into the plasma discharge beam. 
     In another aspect, the electrosurgical apparatus further includes: wherein the distal end of the second fluid flow housing is configured to inject the second gas into the plasma discharge beam in a direction perpendicular to a direction of flow of the first gas. 
     In another aspect, the electrosurgical apparatus further includes: wherein the distal end of the second fluid flow housing includes a gas output that extends in the direction perpendicular to the direction of flow of the first gas. 
     In another aspect, the electrosurgical apparatus further includes: wherein the gas output is configured as a circular slot. 
     In another aspect, the electrosurgical apparatus further includes: wherein the distal end of the second fluid flow housing includes at least one inlet vane, the at least one inlet vane configured to provide a tangential flow to the second gas as the second gas is injected into the plasma discharge beam. 
     In another aspect, the electrosurgical apparatus further includes: wherein the distal end of the second fluid flow housing includes a tapered tip, the tapered tip configured to increase the exit velocity of the second gas. 
     In another aspect, the electrosurgical apparatus further includes: wherein the tapered tip is configured in a conical shape. 
     In another aspect, the electrosurgical apparatus further includes: a transformer assembly, the transformer assembly including a plurality of transformers coupled in series, the transformer assembly configured to receive an input pulse from the electrosurgical generator and output an output pulse, the input pulse having a first voltage and a first pulse width and the output pulse having a second voltage and a second pulse width, the second voltage being higher than the first voltage and the second pulse width being narrower than the first pulse width. 
     In another aspect, the electrosurgical apparatus further includes: wherein the first gas is an inert gas and the second gas is a non-inert gas. 
     In another aspect, the electrosurgical apparatus further includes: wherein the first gas is helium. 
     In another aspect, the electrosurgical apparatus further includes: wherein the second gas is at least one of oxygen and/or nitrogen. 
     In another aspect, the electrosurgical apparatus further includes: wherein the second gas is a combination of oxygen and nitrogen. 
     In another aspect of the present disclosure, an electrosurgical apparatus is provided including: a fluid flow housing including a proximal end, a distal end, a gas port, and a hollow interior, the gas port configured to provide a gas to the hollow interior, such that, the gas flows through the hollow interior and is provided to the distal end of the fluid flow housing; and a first electrode and a second electrode, each electrode disposed exterior to the fluid flow housing, the first electrode disposed toward the proximal end of the fluid flow housing and the second electrode disposed toward the distal end of the fluid flow housing, wherein the first electrode and the second electrode are energized to pre-ionize the gas provided to the distal end of the fluid flow housing. 
     In another aspect, the electrosurgical apparatus further includes: wherein the first and second electrodes are each configured as ring electrodes, such that, the first electrode completely surrounds a proximal portion of the fluid flow housing and the second electrode completely surrounds a distal portion of the fluid flow housing. 
     In another aspect, the electrosurgical apparatus further includes: a third electrode centrally disposed through the hollow interior of the fluid flow housing, the third electrode configured to receive electrosurgical energy from an electrosurgical generator to generate a plasma discharge beam when the gas passes over a distal tip of the third electrode. 
     In another aspect, the electrosurgical apparatus further includes: wherein the first and second electrodes are operated at different electrical phase relationships than the third electrode to maintain an ionizing potential between the first and second electrodes and the third electrode. 
     In another aspect, the electrosurgical apparatus further includes: a transformer assembly, the transformer assembly including a plurality of transformers coupled in series, the transformer assembly configured to receive an input pulse from the electrosurgical generator and output an output pulse, the input pulse having a first voltage and a first pulse width and the output pulse having a second voltage and a second pulse width, the second voltage being higher than the first voltage and the second pulse width being narrower than the first pulse width, the output pulse provided to the third electrode. 
     In another aspect of the present disclosure, an electrosurgical apparatus is provided including: a housing; an electrode; a transformer assembly including a plurality of transformers coupled in series, each transformer configured to receive an input pulse having a first voltage and a first pulse width and output an output pulse having a second voltage and second pulse width, the second voltage being greater than the first voltage and the second pulse width being narrower than the first pulse width, wherein the transformer assembly is configured to receive a first input pulse from an electrosurgical generator and output a first output pulse having a higher voltage and narrower pulse width than the first input pulse, the first output pulse provided from the transformer assembly to the electrode. 
     In another aspect, the electrosurgical apparatus further includes: wherein each of the plurality of transformers is a saturable core transformer. 
     In another aspect, the electrosurgical apparatus further includes: wherein the core of each saturable core transformer is ring-shaped. 
     The electrosurgical apparatus of claim  19 , wherein the core of each saturable core transformer is made of a ferrite material. 
     In another aspect of the present disclosure, an electrosurgical apparatus is provided including: a first fluid flow housing including a proximal end, a distal end, a gas port, and a hollow interior, the gas port configured to provide a first gas to the hollow interior, such that, the first gas flows through the hollow interior and is provided to the distal end of the first fluid flow housing, the hollow interior having a first diameter; a nozzle including a proximal end and a distal end, the proximal end of the nozzle coupled to the distal end of the first fluid flow housing, the nozzle further including a hollow interior and at least one secondary gas input disposed through an exterior portion of the nozzle and providing access to the hollow interior of the nozzle, the hollow interior including a throttle portion having a second diameter, the second diameter being smaller than the first diameter; and an electrode disposed through the hollow interior of the first fluid flow housing, the electrode including a distal tip and configured to receive electrosurgical energy from an electrosurgical generator, such that, when the first gas passes over the distal tip of the electrode and the electrode receives electrosurgical energy, the first gas is at least partially ionized to generate a plasma discharge beam, the plasma discharge beam exiting the distal end of the first fluid flow housing and extending through the hollow interior of the nozzle, such that, the plasma discharge beam exits the distal ends of the nozzle; wherein when the plasma discharge beam extends through the throttle portion of the nozzle, a pressure difference between the hollow interior of the nozzle and the exterior of the nozzle causes a second gas to be drawn into the hollow interior of the nozzle through the at least one secondary gas input and injected into the plasma discharge beam. 
     In another aspect, the electrosurgical apparatus further includes: wherein the at least one secondary gas input is configured to inject the second gas at the throttle portion. 
     In another aspect, the electrosurgical apparatus further includes: wherein the hollow interior of the nozzle further includes a converging portion and a diverging portion, the converging portion disposed adjacent to the throttle portion in a direction toward the proximal and of the nozzle, the diverging portion disposed adjacent to the throttle portion in a direction toward the distal end of the nozzle, wherein the converging portion is configured to gradually decrease a diameter of the hollow interior of the nozzle from the proximal end of the nozzle to the throttle portion, and wherein the diverging portion is configured to gradually increase the diameter of the hollow interior of the nozzle from the throttle portion to the distal end of the nozzle. 
     In another aspect, the electrosurgical apparatus further includes: wherein the at least one secondary gas input is configured to inject the second gas at the diverging portion. 
     In another aspect, the electrosurgical apparatus further includes: wherein the at least one secondary gas input is configured to inject the second gas in a direction perpendicular to the direction of flow of the first gas. 
     In another aspect, the electrosurgical apparatus further includes: wherein the second gas is ambient air exterior to the first fluid flow housing. 
     In another aspect, the electrosurgical apparatus further includes: a second fluid flow housing coaxially disposed around the first fluid flow housing, the second fluid flow housing including a second gas port and a hollow interior, the second gas port providing a second gas to the hollow interior of the second fluid flow housing, wherein when the plasma discharge beam extends through the throttle portion of the nozzle, a pressure difference between the hollow interior of the nozzle and hollow interior of the second fluid flow housing causes the second gas to be drawn into the hollow interior of the nozzle through the at least one secondary gas input and injected into the plasma discharge beam. 
     In another aspect, the electrosurgical apparatus further includes: wherein the first gas is an inert gas and the second gas is a non-inert gas. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the present disclosure will become more apparent in light of the following detailed description when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is an illustration of an exemplary monopolar electrosurgical system in accordance with an embodiment of the present disclosure; 
         FIG. 2  illustrates an exemplary plasma applicator in accordance with an embodiment of the present disclosure; 
         FIG. 3A  illustrates the plasma applicator shown in  FIG. 2  with tangential injectors in accordance with the present disclosure; 
         FIG. 3B  is a cross-section view of the plasma applicator shown in  FIG. 3A  taken along line A-A in accordance with another embodiment of the present disclosure; 
         FIG. 3C  is a cross-section view of a plasma applicator similar to the plasma applicator shown in  FIG. 3A , including inlet vanes, in accordance with another embodiment of the present disclosure; 
         FIG. 4  illustrates the plasma applicator shown in  FIG. 2  with a coaxial injector in accordance with another embodiment of the present disclosure; 
         FIG. 5A  illustrates a tube undergoing the Venturi effect in accordance with the present disclosure; 
         FIG. 5B  illustrates a Venturi burner in accordance with the present disclosure; 
         FIG. 6A  is a side view a plasma applicator including a De Laval nozzle in accordance with an embodiment of the present disclosure; 
         FIG. 6B  is a side cross-section view of the plasma applicator of  FIG. 6A ; 
         FIG. 6C  is a side cross-section view of a plasma applicator include a De Laval nozzle and a secondary fluid flow housing in accordance with another embodiment of the present disclosure; 
         FIG. 6D  illustrates an alternative De Laval nozzle in accordance with another embodiment of the present disclosure; 
         FIG. 7A  illustrates a local discharge applicator with two external electrodes in accordance with an embodiment of the present disclosure; 
         FIG. 7B  illustrates a local discharge applicator with one external electrode and one internal electrode in accordance with an embodiment of the present disclosure; 
         FIG. 8  illustrates a direct discharge applicator in accordance with an embodiment of the present disclosure; 
         FIG. 9A  illustrates a direct discharge applicator with a combined internal electrode with a single external electrode in accordance with an embodiment of the present disclosure; 
         FIG. 9B  illustrates a direct discharge applicator with a combined internal electrode with dual external electrodes in accordance with an embodiment of the present disclosure; 
         FIGS. 10A, 10B, and 10C  illustrate various phase combinations for use with multi-electrode plasma applicators in accordance with an embodiment of the present disclosure; 
         FIG. 11  illustrates an exemplary plasma apparatus in accordance with another embodiment of the present disclosure; 
         FIG. 12  illustrates a multi-stage approach to high voltage pulse generation in accordance with an embodiment of the present disclosure; and 
         FIG. 13  illustrates the plasma apparatus of  FIG. 11  with a transformer assembly including multiple serially coupled saturable core transformer in accordance with an embodiment of the present disclosure. 
     
    
    
     It should be understood that the drawing(s) is for purposes of illustrating the concepts of the disclosure and is not necessarily the only possible configuration for illustrating the disclosure. 
     DETAILED DESCRIPTION 
     Preferred embodiments of the present disclosure will be described hereinbelow with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. In the drawings and in the description which follow, the term “proximal”, as is traditional, will refer to the end of the device, e.g., instrument, apparatus, applicator, handpiece, forceps, etc., which is closer to the user, while the term “distal” will refer to the end which is further from the user. Herein, the phrase “coupled” is defined to mean directly connected to or indirectly connected with through one or more intermediate components. Such intermediate components may include both hardware and software based components. 
     Atmospheric pressure cold plasma discharge beam jets are generally formed by one of two mechanisms. The first is referred to as a “local” discharge, where the primary plasma discharge is confined to the plasma applicator hand piece. The flowing carrier gas draws out an afterglow, which forms the visible beam emerging from the exit nozzle tip of the applicator hand piece. Such local discharge applicators typically have a ground ring around the outer periphery of the exit nozzle tip and complete the plasma discharge circuit within the hand piece. 
     The second type of cold plasma applicator has a centrally mounted electrode wire positioned down the axis of an insulating tube. An exemplary cold plasma applicator having a centrally mounted electrode wire is shown and described in commonly owned U.S. Pat. No. 7,316,682 to Konesky, the details of which will be described below in relation to  FIG. 1 . The wire may also be flattened into a cutting blade which, when retracted into the insulating tube, serves as an electrode. An exemplary cold plasma applicator having an electrode wire configured as a cutting blade is shown and described in commonly owned U.S. Pat. No. 9,060,765 to Rencher et al., the contents of which are incorporated by reference. Regardless of the applicator configuration, this electrode is held at high voltage and high frequency, typically from a few hundred to a few thousand volts, and several kilohertz to several megahertz, respectively. Inert carrier gas flowing through the tube, and over the wire, produces a luminous discharge path from the tip of this wire electrode to the target application site. The discharge path occurs directly from the exit tip of the applicator hand piece to the target application site, so is said to be a “direct” discharge applicator. 
       FIG. 1  shows an exemplary monopolar electrosurgical system generally indicated as  10  comprising an electrosurgical generator (ESU) generally indicated as  12  to generate power for the electrosurgical apparatus  10  and a cold plasma applicator or generator having a centrally mounted electrode wire generally indicated as  14  to generate and apply a plasma stream  16  to a surgical site or target area  18  on a patient  20  resting on a conductive plate or support surface  22 . The electrosurgical generator  12  includes a transformer generally indicated as  24  including a primary and secondary coupled to an electrical source (not shown) to provide high frequency electrical energy to the cold plasma applicator  14 . Typically, the electrosurgical generator  12  comprises an isolated floating potential not referenced to any potential. Thus, current flows between the active and return electrodes. If the output is not isolated, but referenced to “earth”, current can flow to areas with ground potential. If the contact surface of these areas and the patient is relatively small, an undesirable burning can occur. 
     The cold plasma applicator  14  comprises a handpiece or holder  26  having an electrode  28  at least partially disposed within a fluid flow housing  29  and coupled to the transformer  24  to receive the high frequency electrical energy therefrom to at least partially ionize noble gas fed to the fluid flow housing  29  of the handpiece or holder  26  to generate or create the plasma stream  16 . The high frequency electrical energy is fed from the secondary of the transformer  24  through an active conductor  30  to the electrode  28  (collectively active electrode) in the handpiece  26  to create the plasma stream  16  for application to the surgical site  18  on the patient  20 . Furthermore, a current limiting capacitor  25  is provided in series with the electrode  28  to limit the amount of current being delivery to the patient  20 . 
     The return path to the electrosurgical generator  12  is through the tissue and body fluid of the patient  20 , the conductor plate or support member  22  and a return conductor  32  (collectively return electrode) to the secondary of the transformer  24  to complete the isolated, floating potential circuit. 
     In another embodiment, the electrosurgical generator  12  comprises an isolated non-floating potential not referenced to any potential. The plasma current flow back to the electrosurgical generator  12  is through the tissue and body fluid and the patient  20 . From there, the return current circuit is completed through the combined external capacitance to the cold plasma applicator handpiece  26 , surgeon and through displacement current. The capacitance is determined, among other things, by the physical size of the patient  20 . Such an electrosurgical apparatus and generator are described in commonly owned U.S. Pat. No. 7,316,682 to Konesky, the contents of which are hereby incorporated by reference in its entirety. 
     It is to be appreciated that transformer  24  may be disposed in the cold plasma applicator handpiece  26 , as will be described in various embodiments below. In this configuration, other transformers may be provided in the generator  12  for providing a proper voltage and current to the transformer in the handpiece, e.g., a step-down transformer, a step-up transformer or any combination thereof. 
     Atmospheric pressure cold plasma discharges achieve a desired physiological action through a concert of effects. These includes electron and ion bombardment, and the associated charge transfers, localized thermal effects, high electric fields, generation of radical species, and ultra-violet emissions. The contribution of a given effect to the overall physiological effectiveness can be enhanced through a variety of approaches, including carrier gas composition and method of introduction, applicator electrode locations, and methods of high voltage high frequency generation. 
     Helium is often the carrier gas of choice due to its high thermal conductivity and self-limiting potential for avalanche multiplication of the plasma discharge beam current. Both of these properties work together to provide a highly localized effect with minimal collateral damage to surrounding tissue. The high thermal conductivity of helium acts to carry away excess heat from the application site which would otherwise have the potential to damage surrounding tissue. Since helium only has two electrons, the potential for avalanche multiplication is limited, resulting in reduced, stable plasma beam currents. Consequently, when this beam current is dissipated in tissue surrounding the application site, the resulting ohmic heating is also reduced, again, limiting collateral tissue damage. 
     However, there may be circumstances where deeper tissue heating is desirable. These include skin resurfacing and wrinkle removal, disinfection of bulk infectious agents including biofilms, and bulk cancer cell treatment. If the plasma energy is only applied on the target surface, steep temperature gradients would be required to produce deep tissue heating, causing excessive and potentially damaging surface temperatures. 
     One method of increasing deliverable beam currents while maintaining the stable, self-limiting nature of a pure helium carrier gas is to utilize a mixture of inert gases. The additional gas atoms would have a much higher capacity for multiple electron loss (i.e., become more highly ionized) and so have a much higher current carrying capacity on a per-atom basis. Examples of these added gases include argon, krypton and xenon. Argon, with  18  electrons, would require significant ionization energy to remove more than just a few outer electrons, while krypton and xenon, with  36  and  54  electrons respectively, are much more easily multiply-ionized. 
     Note that with relatively small admixtures of these heavy inert gases (e.g., a few percent by volume), the average plasma beam gas temperature would not increase significantly, so the surface temperature of the application site would be essentially the same as if pure helium was being used. Another motivation for using only small percentages of admixed heavy inert gases is their high cost relative to helium. 
     In certain uses of cold plasma discharges, the production of radical species play an important role in the physiological effect, particularly in disinfection, sterilization, and cancer treatment applications. Radical species such as reactive oxygen species (ROS), reactive nitrogen species (RNS) and reactive oxy-nitrogen species (RONS) are typically generated by the interaction of atmospheric oxygen and nitrogen with the cold plasma discharge beam. Their production rate is limited, among other causes, by the diffusion rate of atmospheric components into the plasma beam. 
     The production rate of these radical species, and their associated physiological effectiveness, can be significantly improved by adding small amounts of oxygen, nitrogen, or a combination of the two to the inert carrier gas, typically on the order of a few volume percent. 
     However, in applicator topologies where an internal electrode is directly exposed to the ionized carrier gas, the presence of these non-inert ionized gases may result in significantly accelerated erosion if the electrode surface. This is especially true in the presence of ionized oxygen. 
     To prevent this, oxygen or nitrogen, or potentially other non-inert gases, can be added to the plasma beam down stream of the internal electrode.  FIG. 2  illustrates a coaxial configuration where the non-inert gas is added externally and coaxially to the plasma beam, while remaining down stream of the internal electrode. Referring to  FIG. 2 , applicator  114  is shown in accordance with the present disclosure. Applicator  114  includes a proximal end  147  and a distal end  146 . Applicator  144  includes a fluid flow housing  129  for providing an inert gas to a distal end  101  of fluid flow housing  129 . The fluid flow housing  129  receives the inert gas via an inert gas port  140 . Gas port  140  may be disposed toward proximal end  104  of fluid flow housing  129 . The inert gas may be provided from a gas source coupled to inert gas port  140 . The inert gas provided via inert gas port  140  flows through hollow interior of fluid flow housing  129  and out of the distal end  101  of fluid flow housing  129 . 
     Internal electrode  128  is disposed centrally in the fluid flow housing  129 . Internal electrode  128  may be coupled to an electrosurgical generator disposed exterior to applicator  114 . Internal electrode  128  is configured to receive electrosurgical energy (e.g., with high voltage and at high frequency) from the electrosurgical generator. Internal electrode  129  includes a distal tip  103 , where distal end  101  of fluid flow housing  129  extends passed distal tip  103  of internal electrode  128 . 
     A non-inert fluid flow housing  142  is coaxially disposed around the fluid flow housing  129  and is coupled to a non-inert gas source via non-inert gas port  144 . Gas port  144  may be disposed toward proximal end  105  of fluid flow housing  142 . Fluid flow housing  142  includes a hollow interior configured to carry non-inert gas provided via non-inert gas port  144  to the distal end  102  of fluid flow housing  142 . It is to be appreciated that the hollow interior of fluid flow housing  142  is configured to contain the non-inert gas provided by non-inert gas port  144 , such that, the non-inert gas does not enter the hollow interior of fluid flow housing  129 . 
     A plasma discharge beam is generated when an inert gas flows through the hollow interior of fluid flow housing  129  and passes over the distal tip  103  of the electrode  128 , when the electrode  128  is supplied with high voltage at a high frequency from an electrosurgical generator. The plasma discharge beam exits the distal end  101  of fluid flow housing  129 . The non-inert gas is then injected into the plasma discharge beam  116  by providing the non-inert gas to the distal end  146  of the applicator  114  via the non-inert gas fluid flow housing  142 . As shown in  FIG. 2 , the distal end  102  of fluid flow housing  142  extends passed the distal end  101  of fluid flow housing  129 . In this way, the non-inert gas is only injected after the plasma discharge beam  116  has already been generated and is exiting the distal end  101  of fluid flow housing  129 . 
     The distal end  102  of fluid flow housing  129  is configured to inject non-inert gas into the plasma discharge beam  116 . As will be described below, the distal ends  101 , 102  of housings  129 ,  142  may be modified in accordance with the present disclosure to enhance the injecting and mixing of the non-inert gas with the plasma discharge beam  116 . 
     Introduction of these additional non-inert gases into the plasma discharge beam  129  can be further improved by injecting the non-inert gas(es) at an angle relative to the direction of flow of the carrier gas. For example, to  FIGS. 3A and 3B  an applicator  114  is shown in accordance with present disclosure. The design of the applicator  114  enhances the mixing of the added non-inert gases with the plasma beam  116  and its associated inert carrier gas flow. As shown in  FIG. 3A , inert gas (e.g., helium) is provided via gas port  140  to the hollow interior of fluid flow housing  129 . The inert gas flow in a direction C (shown in  FIG. 3A ) within the hollow interior of fluid flow housing  129 . Non-inert gas is provided via gas port  144  into the hollow interior of fluid flow housing  142 . The non-inert gas flows in a direction B (shown in  FIG. 3A ). In this embodiment, the distal end  102  of fluid flow housing  142  is configured to inject the non-inert gas at a right angle to the flow of the inert gas. In one embodiment, the non-inert gas fluid flow housing  142  is configured with a gas output  148  at the distal end  102  that extends perpendicularly to the direction of the flow of the inert gas (i.e., perpendicularly to direction C) in a direction toward the shared center of fluid flow housings  129 ,  142 . As shown in  FIG. 3B , in some embodiments, gas ouput  148  is configured as a circular slot that injects non-inert gas radially toward the shared center of fluid flow housings  129 ,  142  from all directions. 
     In some embodiments, one or more tilted inlet valves may be disposed within the circular slot of gas input  148  to introduce a tangential flow (i.e., a swirling or curling) of the non-inert gas as the non-inert gas is injected into the plasma discharge beam  116 . For example, referring to  FIG. 3C , one or more inlet vanes  149  are shown disposed in the circular slot of gas input  148 , such that, inlet vanes  149  are downstream of electrode  128 . Inlet vanes  149  are tilted or slanted (as shown in  FIG. 3C ) to create a tangential flow (i.e., a swirling or curling) of the non-inert gas with respect to the shared center of housings  129 ,  142  as the non-inert gas is injected into the plasma discharge beam  116  to further enhance injection and mixing. It is to be appreciated that although four inlet vanes  149  are shown in  FIG. 3C , in other embodiments, applicator  114  may include any number of inlet vanes  149  (i.e., more or less than four inlet vanes). 
     Improved mixing of the non-inert gases can also be affected by tapering and reducing the exit diameter of the distal end  102  of external coaxial tube  142 . For example, referring to  FIG. 4 . As shown in  FIG. 4 , the external coaxial tube (i.e., the non-inert fluid flow housing  142 ) can be configured with a tapered tip  150  at the distal end  102 . The tapered tip may form a conical shape, where the opening of the tapered tip has a smaller diameter than the diameter of the non-inert fluid flow housing  142 . In another embodiment, tapered tip  150  may be configured as a seperate conical end piece that is attached and added to the distal end  102  of the non-inert fluid flow housing  142  to achieve the same effect. In either case, tapered tip  150  is configured to increase the exit velocity of the non-inert gas flow and improve turbulent mixing at the boundary of the coaxial gas flows. Furthermore, the tapered tip  150  is configured to inject the non-inert gas into the plasma discharge beam  116  at an angle, which also improves the mixing of the non-inert gas with the plasma discharge beam  116 . 
     Enhanced mixing and injection of the non-inert gas into a plasma discharge beam may also be achieved by including a De Laval nozzle distal to the electrode tip of a plasma applicator. The De Laval nozzle is configured to take advantage of the Venturi effect to enhance the mixing and injection of the non-inert gas into the plasma discharge beam. 
     The Venturi effect states that when a constant volume flow of a fluid passes through a constricted area, the velocity of the fluid will increase and the static pressure of the fluid will decrease. 
     Referring to  FIG. 5A  a Venturi tube  800  is shown in accordance with the present disclosure. In tube  800 , the fluid flows from end  801  to end  802  at a constant volume flow rate. Tube  800  includes a converging portion  803 , a throat or throttle portion  804 , and a diverging portion  805 . To maintain constant volume flow rate, the fluid flowing through tube  800  must be moved at the same rate, despite the constricted space in the throttle portion  804  of tube  800 . Therefore, the velocity of the fluid is increased. The velocity change will create a pressure change according to Bernoulli&#39;s principle, which states that within a specified flow field, a decrease in pressure occurs when there is an increase in velocity. 
     One application of Venturi tubes, such as tube  800 , is mixing of liquids and/or gases. This is possible because the lower pressure inside the tube  800  creates a pressure difference between the device and its surrounding environment. As gas flows through the interior of tube  800  from end  801  to end  802 , substances outside of the Venturi tube  800  (e.g., ambient air) are sucked into the low-pressure area (i.e., throttle portion  804 ), and gas and/or liquid components become mixed together within the tube  800 . 
     Venturi burners are an example of a device that employs the Venturi effect. Referring to  FIG. 5B , a Venturi burner  850  is shown. Venturi burner  850  include ends  851 ,  852 , converging portion,  853 , throttle portion  854 . Throttle portion  854  includes one or more apertures  855 , and diverging portion  856 . The lower pressure inside the burner  850  creates a pressure difference between the interior of burner  850  and its surrounding environment. As gas and/or liquid flows from end  851  of burner  850  to end  852  of burner  850 , substances outside of the burner  850 , such as ambient air, are sucked into the throttle portion  854  via aperture  856 , and the gas and/or liquid components from outside of the burner  850  become mixed with the gas and/or liquid flowing through the interior of the burner  850 . 
     Referring to  FIG. 6A , a side view of an applicator  714  is shown in accordance with an embodiment the present disclosure. Referring to  FIG. 6B , a side-cross-section view of the applicator  714  is shown in accordance with the present disclosure. Applicator  714  includes a fluid flow housing  729  and a De Laval nozzle  750 . Housing  729  includes a distal end  701 , a proximal end  704 , an interior  740 , and an electrode  728 , where electrode  728  is centrally disposed within interior  740 . Nozzle  750  includes an interior  770 , and non-inert gas inputs  764 , where inputs  764  provide access to the interior  770  of nozzle  750 . Interior  770  of nozzle  750  includes a converting portion  756 , a throttle portion  758 , and a diverging portion  760 . Distal end  701  of housing  729  is coupled to proximal end  754  of nozzle  750 . Housing  729 , nozzle  750 , and electrode  728  are coaxial. It is to be appreciated that in some embodiments housing  729  and nozzle  750  may be a component. In other embodiments, housing  729  and nozzle  750  may be separate components, where nozzle  750  is configured to be an add-on component that may be coupled to housing  729 . 
     It is to be appreciated that the cross-sectional area of both converging portion  756  and diverging portion  760  are larger than throttle portion  758 . In some embodiments, the cross-sectional area of portion  756  is smaller than the cross-sectional area of portion  760 . 
     In either case, the interior  740  of housing  729  includes a first diameter (d 1 , shown in  FIG. 6B ) remaining constant from the proximal end  704  to the distal end  701  of housing  729 . Progressing from the proximal end  754  of nozzle  750 , along a direction C (i.e., the direction of carrier gas flow), converging portion  756  converges toward the center of applicator  714 , such that, the diameter of interior  770  is gradually reduced along direction C throughout converging portion  756 . Throttle portion  758  includes a second diameter (d 1 , shown in  FIG. 6B ), where the second diameter is smaller than the first diameter. The geometry of the interior  770  of nozzle  750  is configured such that the second diameter is the smallest diameter at any point in the interior of applicator  714 . Continuing along direction C, diverging portion  760  diverges away from the center of applicator  714 , such that, the diameter of interior  770  is gradually increases along direction C throughout diverging portion  760  until a third diameter (d 3 , shown in  FIG. 6B ) is achieved at the distal end  751  of nozzle  750 . It is to be appreciated that in some embodiments, the first diameter may be substantially the same as the third diameter, while in other embodiments, the third diameter may be larger than the first diameter. 
     In operation, inert gas (e.g., Helium) is provided via gas input  741  and flows through interior  740  of housing  729  along direction C. A plasma discharge beam is generated when an inert gas passes over the distal tip  703  of the electrode  728 , when the electrode  728  is supplied with high voltage at a high frequency from an electrosurgical generator. The plasma discharge beam exits the distal ends  701  of fluid flow housing  729  and distal end  751  of nozzle  750 . 
     As the plasma discharge and inert gas flow through portions  756 ,  758 , and  760  of interior  770 , a pressure difference is created between the interior  770  of nozzle  750  and the exterior of applicator  714 , such that the pressure at throttle portion  758 , is lower than the pressure exterior to applicator  714 . The lower pressure of the throttle portion  758  causes non-inert gas from the exterior of applicator  114  to be sucked or drawn into the throttle portion  758  of interior  770  via gas inputs  764  (due to the Venturi effect described above). The non-inert gas drawn into the throttle portion  758  of interior  770  is then injected into the plasma discharge beam of applicator  714  and mixed to generate reactive species. 
     It is to be appreciated that in some embodiments, the non-inert gas that is drawn in through gas inputs  764  is the ambient air outside of applicator  714 . In this embodiment, no additional gas supply is needed to inject non-inert gas into interior  770 . 
     In other embodiments, a secondary gas supply may be coupled to gas inputs  764  to provide a non-inert to the interior  770  of nozzle  750 . For example, a second fluid flow housing may be coaxially disposed over fluid flow housing  729 , where non-inert gas is provided the interior of the second fluid flow housing and into the gas inputs  764  to be injected into interior  770 . An embodiment of applicator  729  including a second fluid flow housing is shown in  FIG. 6C . 
     Referring to  FIG. 6C , a side cross-sectional view of applicator  714  is shown with a second fluid flow housing  792  coaxially disposed over first fluid flow housing  729 . Fluid flow housing  729  includes a proximal end  793 , a distal end  794 , and a non-inert gas input  790 . Non-inert gas port or input  790  is coupled to a non-inert gas source and configured to provide non-inert gas into the interior  795  of fluid flow housing  792 . In operation, as the inert carrier gas flows in a distal direction C through interior  740  of housing  729  and through interior  770  of nozzle  750 . A plasma discharge beam is generated when an inert gas passes over the distal tip  703  of the electrode  728 , when the electrode  728  is supplied with high voltage at a high frequency from an electrosurgical generator. 
     As the plasma discharge beam and inert gas flow through portions  756 ,  758 , and  760  of interior  770 , a pressure difference is created between the interior  770  of nozzle  750  and the interior  795  of fluid flow housing  792 , such that the pressure at throttle portion  758 , is lower than the pressure in interior  795 . The lower pressure of the throttle portion  758  causes non-inert gas in the interior  795  of housing  792  to be sucked or drawn into the throttle portion  758  of interior  770  via gas inputs  764  (due to the Venturi effect described above), as indicated by arrow E in  FIG. 6C . The non-inert gas drawn into the throttle portion  758  of interior  770  is then injected into the plasma discharge beam of applicator  714  and mixed to generate reactive species. 
     It is to be appreciated that although only four non-inert gas inputs  764  are shown in  FIG. 6A , in other embodiments, more or less gas inputs  764  may be disposed around nozzle  750  at predetermined intervals as desired. Furthermore, in some embodiments, gas inputs  764  may include titled vanes (similar to vanes  149 ) to introduce a tangential flow (i.e., a curl or swirl) into the non-inert gas relative to the plasma discharge and inert gas flowing along direction C. It is also to be appreciated that gas input  764  may be configured to inject non-inert gas into interior  770  at various angles. For example, in  FIG. 6B , gas inputs  764  are configured to be aligned perpendicularly to direction C, such that non-inert gas is injected into interior  770  in a direction perpendicular to direction C. However, in other embodiments, gas inputs  764  may be configured to be aligned at other angle relative to direction C (e.g., 45 degrees, 30 degrees, etc.), such that, non-inert gas is injected into interior  770  at any desirable angle to promote the mixing of inert and non-inert gases. 
     It is to be appreciated that, since the throttle portion  758  is disposed distal to the electrode tip  703 , there is no risk of electrode erosion from injection of the non-inert gas into interior  770 . The pressure in the converging portion  756  is always higher than the pressure in the throttle portion  758 , therefore, the electrode  728  is protected from upstream (i.e., proximal) migration of the non-inert gas injected into interior  770 . 
     Although, in the embodiment of nozzle  750  shown in  FIG. 6B , gas inputs  764  are configured to inject non-inert gas into the throttle portion  758 , in other embodiments of the present disclosure, gas inputs  764  may be disposed downstream (distally) of throttle portion  758  in diverging portion  760 . For example, referring to  FIG. 6D , gas inputs  764  are shown disposed downstream of throttle portion  758 . It is to be appreciated that the placement of gas inputs  764 , must be chosen such that the gas inputs  764  are placed in a portion of interior  770  that has a sufficient low pressure relative to the exterior of applicator  714  to enable the Venturi effect to occur when inert gas flows along direction C through the interior of applicator  714 . Since the pressure in interior  770  is the lowest at throttle portion  756 , when gas inputs  764  are placed in diverging portion  760 , better pressure differentials between the interior  770  and the exterior of applicator  714  are achieved as gas inputs  764  are placed in a portion of diverging portion  760  that is closer to throttle portion  758 . 
     It is to be appreciated that, in some embodiments, walls of the fluid flow housings  729 ,  792 , and the nozzle  750  are made of a non-conducting material. 
     It is to be appreciated that, in some embodiments, the nozzle  750 , described above, is generally cylindrical in shape and includes a generally cylindrical hollow interior. 
     It is to be appreciated that nozzle  750  may be implemented into any of the applicators described above. 
     Cold plasma applicator topologies can be broadly grouped into local discharge types and direct discharge types. In the local discharge topologies, an external electrode is placed around the applicator nozzle tip, i.e., the distal end of the fluid flow housing. For example, referring to  FIG. 7A , a local discharge applicator  214  with two external electrodes is illustrated. A first external electrode  211  is disposed around the distal end  246  of the fluid flow housing  229 . A second external electrode  213  may be placed further upstream of the first external electrode  211 . Alternately, as shown in  FIG. 7B , the second electrode  228  may be an internal electrode. The primary plasma discharge occurs between these electrodes (i.e., intense plasma region  250 ) and is said to be “local” to the applicator. An afterglow plasma (i.e., long-lived reactive species region  252 ) exits the applicator nozzle, and in general, carries little or no current between the applicator and the target surface  218 . The target surface  218  may be either electrically conductive or nonconductive. 
     By contrast, a direct discharge applicator topology only has a single internal electrode, as shown in  FIG. 8 . A primary direct discharge path is created between the internal electrode  328  and the conductive target surface  318 . If this target surface  318  is grounded, the plasma beam carries a conduction current. If the target surface  318  is electrically isolated, the plasma beam carries a displacement current, alternately charging and discharging the target surface as though it were one plate of a capacitor. 
     Since a direct plasma discharge applicator topology establishes a continuous current carrying path between the applicator and the target site, the distance over which this plasma discharge may interact with surrounding gases is substantially greater than in the local discharge topology. Consequently, the rate at which radical species are generated is greater in the direct discharge topology as compared to the local discharge, all other variables being equal. 
     However, since the direct discharge plasma path is initiated from the tip of the applicator&#39;s internal electrode, the plasma beam diameter is generally small, on the order of one to a few millimeters. While this is beneficial for applications where high precision positioning and control are important, other applications would benefit from a wider beam, such as disinfection, sterilization, and cancer treatment, among others. A wider beam would also provide greater surface area to interact with surrounding gases, thereby further enhancing radical species production rates. 
     Combining topological components of both local and direct discharge permits a pre-ionization of the carrier gas stream before it approaches the tip of the internal electrode, as shown and in  FIGS. 9A and 9B . Referring to  FIG. 9A , applicator  414  includes a fluid flow housing  429  with a centrally disposed internal electrode  428 . When an inert gas is introduced to the fluid flow housing  429  via input  440  and the electrode  428  is energized (e.g., via an electrosurgical generator or other power source), a plasma discharge beam results at the distal end  446  of the applicator  414 . Upper external electrode  413  is disposed at a proximal end  431  of the fluid flow housing  429 . It is to be appreciated that electrode  413  may be a ring electrode that completely surrounds the exterior of the appropriate portion of the fluid flow housing  429 . By positioning the upper external electrode  413  at the proximal end  431  of the housing  429  before the distal tip  433  of electrode  428 , a pre-ionization of the carrier gas stream is achieved. In this manner, when the pre-ionized carrier gas reached the tip  433 , the resulting beam discharge plasma beam is wider. 
       FIG. 9B  illustrates a further embodiment of pre-ionization of the carrier gas stream before it approaches the tip of an internal electrode of an applicator. Here, applicator  460  includes a fluid flow housing  429  with a centrally disposed internal electrode  428 . When an inert gas is introduced to the fluid flow housing  429  via input  440  and the electrode  428  is energized, a plasma discharge beam results and exits at the distal end  446  of the applicator  414 . Upper external electrode  413  is disposed at a proximal end  431  of the fluid flow housing  429 . Lower external electrode  411  is disposed at a distal end  446  of the fluid flow housing  429 . It is to be appreciated that electrodes  411 ,  413  may be ring electrodes that completely surround the appropriate exterior portions of the fluid flow housing  429 . By positioning the upper external electrode  413  at the proximal end  431  of the housing  429  before the distal tip  433  of electrode  428 , a pre-ionization of the carrier gas stream is achieved. The lower electrode  411  further contributes to the overall pre-ionization. Note that both upper and lower external electrodes,  413  and  411  respectively, must be operated at a different electrical phase relationship than that of the high voltage high frequency power being applied to the internal electrode  428  to maintain an ionizing potential between them. In this manner, when the pre-ionized carrier gas reached the tip  433 , the resulting beam discharge plasma beam is wider. 
     It is to be appreciated that several of the embodiments described above include multi-electrode configurations (i.e., including one or more exterior electrodes and an interior electrode). Referring to  FIG. 10 , several phase combinations are possible to satisfy the requirement of maintaining an ionizing potential between the electrodes of the applicators provided above. 
       FIG. 10A  includes a phase combination I, where one or more electrodes include a waveform (i) and one or more electrodes are held at ground waveform (ii). For example, for applicators including both external and internal electrodes, such as in  FIGS. 7A, 7B, 9A, and 9B , the external electrodes may be held at waveform (i) and the internal electrode may be held at waveform (ii). Alternatively, the internal electrode may be held at waveform (i), while the external electrode is held at waveform (ii). 
       FIG. 10B  includes an alternative phase: phase combination II. In phase combination II, waveforms (i) and (ii) are out of phase (e.g., by 180 degrees). As applied to the applicators of  FIGS. 7A, 7B, 9A, and 9B , the external electrodes may be held at waveform (i) and the internal electrode may be held at waveform (ii). Alternatively, the internal electrode may be held at waveform (i), while the external electrode is held at waveform (ii). 
       FIG. 10C  includes yet another alternative phase combination: phase combination III. Phase combination III is applicable to applicators includes three electrodes, where waveforms (i), (ii), and (iii) are each out of phase (e.g., 90 degrees) relative to each other, and each waveform is applied to a separate electrode. For example, applicator  460  of  FIG. 9B , includes electrodes  411 ,  413 , and  428 . Using phase combination III with applicator  460  of  FIG. 9B , a different waveform of waveforms (i)-(iii) of phase combination III may be applied to each of electrodes  411 ,  413 ,  428 . For example, in one embodiment, waveform (i) is applied to internal electrode  428  and waveforms (ii) and (iii) are applied to external electrodes  413  and  411  respectively. 
     It is to be appreciated that the waveforms shown in  FIG. 10C  are merely one combination of several possible combinations of waveforms that may be applied to applicators includes multiple electrodes. Any arbitrary waveform combination can be used so long as the instantaneous voltage difference between internal and external electrodes is sufficient to ionize the gas between them. 
     As mentioned previously, there are many applications where a highly localized effect is desirable to minimize collateral damage to surrounding tissue, and so it is also desirable to minimize electrical current flow away from the application site. Since electrical power is the product of voltage multiplied by current, decreasing the current implies a compensating increase in voltage to maintain a given applied power level. However, increasing the applicator plasma voltage carries with it a number of increasing difficulties. 
     There are two methods of providing high voltage high frequency power to the applicator electrode in the direct discharge configuration. One is to have a final stage high voltage transformer located in the applicator hand piece itself. For example, referring to  FIG. 11 , an electrosurgical apparatus  500  in accordance with another embodiment of the present disclosure is illustrated. Generally, the apparatus  500  includes a housing  502  having a proximal end  503  and a distal end  505  and a tube  504  having an open distal end  506  and a proximal end  508  coupled to the distal end  505  of the housing  502 , thereby forming a handpiece. The housing  502  includes a plurality of buttons  507 , e.g., buttons  514 ,  515  and  519 , and a first slider  516  and second slider  521 . Activation of the first slider  516  will expose a blade or electrode  518  at the open distal end  506  of the tube  504 . Activation of the second slider  521  sets the apparatus into different modes. Activation of the individual buttons  514 ,  515 ,  519  will apply electrosurgical energy to the blade  518  to affect different electrosurgical modes and, in certain embodiments, enable gas flow through an internal flow tube (not shown). For example, in one embodiment, when the electrode  518  is retracted into the tube  504 , a plasma discharge is generated when an inert gas in flowing through the internal flow tube and high voltage at high frequency is applied to the electrode  518 . 
     Additionally, a transformer assembly  520  is provided on the proximal end  503  of the housing  502  for coupling a source of radio frequency (RF) energy to the apparatus  500  via cable  560  and connector  562 . The cable  560  includes a plurality of conductors for providing electrosurgical energy to the apparatus  500  and for communication signals to and from the apparatus  500  and an RF source, e.g., an electrosurgical generator  523 . 
     The high voltage output of a transformer in the transformer assembly  520  is connected to the direct discharge electrode  518  through a current limiting device, typically a high voltage capacitor or resistor. Such an applicator as shown in  FIG. 11  can be unwieldy due to the increased weight of the high voltage transformer, in addition to the higher construction costs. 
     An alternate method is to have the final stage high voltage output transformer located in the generator box, e.g., electrosurgical generator  523 , resulting in a much lighter weight, more dexterous applicator. The difficulties here are the need for a higher voltage rating for the cable connecting the applicator to the generator box, increased radiated emissions from that cable, and the need for an ionization initiating pulse with a high crest factor (ratio of peak to RMS voltage). Since the output transformer is driving the load of the cable in addition to the actual application load, there may be an undesirable increase in applied current to compensate for a decrease in voltage in providing a given power level. 
     An ideal situation would be to produce the final output high voltage generation in the applicator hand piece without the previous penalties of increased weight, cost and loss of dexterity. Rather than employing a single high voltage output transformer in the transformer assembly of the applicator hand piece, a series of small light weight saturable core transformers may be employed. In one embodiment, a series of saturable core transformers are disposed in, for example, the transformer assembly  520 . 
     By saturating the core of each of the series of transformers where the secondary of the previous stage (i.e., transformer) is directly connected to the primary of the next stage, the generation of high frequency harmonics results. These harmonics add to produce a narrower pulse width of increased amplitude. A succession of stages each sequentially narrows the pulse and raises the amplitude until the final required output voltage is achieved. The degree of core saturation in each transformer stage is minimized, at the potential increase in the number of stages, to reduce parasitic power losses in the overall conversion of pulse width to pulse amplitude. Core saturation leads to the generation of waste heat, which must be effectively dissipated, and reduces overall efficiency. The more heavily saturated a core becomes, the more waste heat is generated, but the degree of pulse compressing higher harmonics is also increased. A design optimization tradeoff is made between degree of core saturation, overall conversion efficiency, and the number of stages required to produce the desired output voltage. 
       FIG. 12  illustrates the voltage pulses after each corresponding transformer or output stage. An input pulse  602  is transmitted to a first stage transformer  604 . The transformed pulse  606  is illustrated as having a shorter pulse width and larger amplitude relative to pulse  602 . The transformed pulse  606  is then transformed in the 2 nd  stage transformer  608  resulting in pulse  610 , which has a relative shorter pulse width and larger amplitude relative to pulse  606 . The transformed pulse  610  is then transformed to the Nth stage transformer  612  resulting in output pulse  614 , which has a relative shorter pulse width and larger amplitude relative to pulse  610 . It is to be appreciated that the number of transformers may be variable. In one embodiment, the number of transformers may be dependent on a desired pulse width and amplitude of the final output pulse that is subsequently transmitted to the electrode, e.g., electrode  518 . For example, if a given stage has a pulse compression ratio of 4 (output pulse width is ¼ the input pulse width) then the amplitude will increase approximately 4 times. Two successive stages will increase the amplitude 16 times, and three stages will increase it 64 times. A 100 volt peak pulse at the input to a series of three stages will become a 6.4 kV peak output pulse. 
     Referring to  FIG. 13 , electrosurgical apparatus  500  is shown with transformer assembly  520  including a plurality of saturable core transformers coupled serially. As shown in  FIG. 13 , each transformer includes a ring-shaped core, where a primary winding is wrapped around a first side or portion of the ring-shaped core and a secondary winding is wrapped around a second side or portion of the ring-shaped core. It is to be appreciated that each ring-shaped core is made of a ferrite material, for example, comprising manganese and/or zinc. Exemplary ring-shaped core materials that may be used for the cores of each transformer of transformer assembly  520 , include, but are not limited to, Magnetics Corp. Type 3B7, Magnetics Corp. Type N-29, and METGLAS® Magnetic Alloy 2714. It is to be appreciated that the primary winding and secondary winding of each transformer may include a predetermined number of turns. For example, in one embodiment, the primary and secondary of each transformer of assembly  520  includes 10 turns. 
     As shown in  FIG. 13 , transformer assembly  520  includes a plurality of saturable core ring transforms  604 ,  608 ,  612 . Electrosurgical generator  523  is coupled to the primary  604 A of a first transformer  604  via cable  560 . The secondary  604 B of transformer  604  is coupled to the primary  608 A of a second transformer  608  and the secondary  608 B of the second transformer  608  is coupled to the primary of a subsequent transformer. This manner of serial coupling between each saturable core transformer in assembly  520  continues until the primary  612 A of the last transformer  612  in assembly  520  is coupled to. The secondary  612 B of the last transformer  612  is coupled to electrode  518  and to ground. 
     It is to be appreciated that, although only three transformers  604 ,  608 ,  612  are shown in  FIG. 13  as being included in assembly  520 , any number of transformers may be included in assembly  520  to achieve the desired peak voltage. In one embodiment, four transformers are included in assembly  520 , however, in other embodiments more or less transformers may be included. Furthermore, it is to be appreciated that, in some embodiments, each transformer included in assembly  520  is substantially identical (i.e., the same component), while in other embodiments, the value and/or properties of each transformer in assembly  520  may be different to optimize the functioning of transformer assembly  520 . 
     In one embodiment, each stage or transformer in assembly  520  is arranged in a substantially linear fashion (i.e., in a straight line). This linear arrangement provides physical high voltage isolation between each stage or transformer. 
     In operation, electrosurgical energy, in the form of a pulse train, is provided to the input of transformer assembly  520  and received by the primary  604 A of the 1st stage or transformer  604 . The width of each pulse received by the 1st stage or transformer  604  is narrowed, while the amplitude of the pulse is increased, as described above. The output of the 1st stage is provided via the secondary  604 B of the 1st stage  604  to the primary  608 A of the 2 nd  stage  608 , where the 2 nd  stage  608  is also configured to narrow the width and increase the amplitude of the received pulse. The output of the 2 nd  stage  608  is then provided via the secondary  608 B of the 2 nd  stage  608  to the primary of the next stage in transformer assembly  520 . This process is repeated by each stage in transformer assembly  520 , until the last stage  612  outputs a final pulse via the secondary  612 B of the last stage  612 , which is outputted via the output of transformer assembly  520  to electrode  518 . 
     It is to be appreciated that the transformer assembly  520  shown in  FIGS. 11, 12, and 13  may be included and incorporated into any of applicators  114 ,  214 ,  314 ,  414 ,  460 ,  714 , and/or  500  described above. It is to be appreciated that the pulse compression technique employed in transformer assembly  520 , may be implemented with applicators including both internal and external electrodes. Where two phase combinations are required, i.e., as provided for by  FIGS. 10A and 10B , for example, with applicators including two electrodes, a first end of the secondary of the last transformer  612  in assembly  520  is coupled to the first electrode of the applicator and a second end of the secondary of the last transformer  612  is coupled to the second electrode of the applicator. Where two or more phase combinations are required, i.e., as provided for by  FIGS. 10A-C , the timing of the various pulses must satisfy the requirement that sufficient voltage exists between the electrodes of the applicator to ionize the gas between them, and a separate transformer assembly may be needed for each phase. For example, where two or more phase combinations are required (i.e., where two or more electrodes are included in the applicator), a second and/or third group of serially coupled transformers may be included in assembly  520  to be coupled to a second and/or third electrode of the applicator. 
     It is to be appreciated that, in some embodiments, the fluid flow housings of each of the applicators described above are generally cylindrical in shape and include a generally cylindrical hollow interior. 
     It is to be appreciated that the various features shown and described are interchangeable, that is a feature shown in one embodiment may be incorporated into another embodiment. 
     While the disclosure has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims. 
     Furthermore, although the foregoing text sets forth a detailed description of numerous embodiments, it should be understood that the legal scope of the invention is defined by the words of the claims set forth at the end of this patent. The detailed description is to be construed as exemplary only and does not describe every possible embodiment, as describing every possible embodiment would be impractical, if not impossible. One could implement numerous alternate embodiments, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims. 
     It should also be understood that, unless a term is expressly defined in this patent using the sentence “As used herein, the term ‘______’ is hereby defined to mean . . . ” or a similar sentence, there is no intent to limit the meaning of that term, either expressly or by implication, beyond its plain or ordinary meaning, and such term should not be interpreted to be limited in scope based on any statement made in any section of this patent (other than the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term be limited, by implication or otherwise, to that single meaning. Finally, unless a claim element is defined by reciting the word “means” and a function without the recital of any structure, it is not intended that the scope of any claim element be interpreted based on the application of 35 U.S.C. § 112, sixth paragraph.