HK1123668B - Plasma-generating device, plasma surgical device, use of a plasma-generating device and method of generating a plasma - Google Patents

Description

Plasma generating device, plasma surgical device, use of a plasma generating device and method for generating plasma

Priority

The present application claims priority from swedish patent application No.0501602-7, which swedish patent application No.0501602-7 was filed on 7/8/2005.

Technical Field

The invention relates to a plasma-generating device comprising an anode, a cathode and an elongated plasma channel extending substantially in a direction from said cathode to said anode. The plasma channel has a throttling portion arranged in said plasma chamber between said cathode and an outlet opening arranged in said anode. The invention also applies to a plasma surgical device and to the use of a plasma surgical device in surgery and to a method for generating plasma.

Background

A plasma generating apparatus relates to an apparatus for generating a gas plasma. The device can be used, for example, in surgery to stop bleeding, i.e. to coagulate biological tissue (coagulation).

Generally, the plasma generating device is long and narrow. The gas plasma is preferably exhausted at one end of the device and its temperature may cause coagulation of tissue affected by the gas plasma.

Due to recent advances in surgical techniques, a technique known as laparoscopic (keyhole) surgery is more often used. This means that there is a greater need for devices of smaller size to enable access without major surgery in surgical applications. The smaller size of the device also facilitates very precise manipulation of surgical instruments during surgical procedures.

WO2004/030551(Suslov) discloses a prior art plasma surgical device which will be particularly useful for reducing bleeding in living tissue by a gas plasma. The apparatus comprises a plasma-generating system having an anode, a cathode and a gas supply channel for supplying gas to the plasma-generating system. Furthermore, the plasma-generating system comprises at least one electrode, which is arranged between said cathode and anode. A housing of electrically conductive material connected to the anode encloses the plasma-generating system and forms a gas supply channel.

It is also desirable to provide a plasma-generating device as described above which is capable of not only coagulating bleeding in living tissue, but also cutting tissue.

For the device of WO2004/030551, a relatively high gas flow rate of the plasma generating gas is generally required in order to generate the plasma for cutting. In order to generate a plasma having a suitable temperature at this gas flow rate, it is generally necessary to provide a relatively high operating current to the device.

Currently, it is desirable to operate plasma generating devices at lower operating currents, because higher operating currents are often difficult to provide in certain environments, such as medical environments. Often, higher operating currents also result in a large number of wires, which can make operation awkward in precision work (e.g., in keyhole surgery).

Alternatively, the device of WO2004/030551 may be formed with a relatively long plasma channel in order to generate a plasma of suitable temperature at the required gas flow rate. However, a longer plasma channel may make the plasma-generating device larger and awkward to handle in certain applications, such as medical applications, in particular keyhole surgery applications.

In many applications, the plasma generated should also be relatively pure with few impurities. It is also desirable that the generated plasma discharged from the plasma-generating device has a certain pressure and gas volume flow, which for example are not detrimental to the patient to be treated.

As mentioned above, there is a need for an improved plasma-generating device, which may be used, for example, for cutting biological tissue. There is therefore a need for an improved plasma-generating device which is capable of generating a pure plasma at a lower operating current and a lower gas volume flow.

Disclosure of Invention

It is an object of the present invention to provide an improved plasma-generating device.

Another object is to provide a plasma surgical device and the use of such a plasma surgical device in the field of surgery.

Another object is to provide a method of generating plasma and the use of the plasma for cutting biological tissue.

According to one aspect of the invention, a plasma-generating device is provided, comprising an anode, a cathode and an elongate plasma channel extending substantially in a direction from said cathode to said anode, the plasma channel having a throttling portion arranged in said plasma channel between said cathode and an outlet opening arranged in said anode. Said throttling portion of the plasma-generating device divides said plasma channel into a high-pressure chamber, which is located on the side of the throttling portion closest to the cathode and has a first maximum cross-sectional surface transverse to the longitudinal direction of the plasma channel, and a low-pressure chamber, which opens into said anode and has a second maximum cross-sectional surface transverse to the longitudinal direction of the plasma channel, said throttling portion having a third cross-sectional surface transverse to the longitudinal direction of the plasma channel, which third cross-sectional surface is smaller than said first maximum cross-sectional surface and said second maximum cross-sectional surface, at least one intermediate electrode being arranged between said cathode and said throttling portion. Preferably, the intermediate electrode may be arranged inside the high pressure chamber or form part of the high pressure chamber.

This structure of the plasma-generating device enables the plasma arranged in the plasma channel to be heated to a high temperature at a relatively low operating current supplied to the plasma-generating device. In this context, the elevated temperature of the plasma means a temperature in excess of 11000 deg.C, preferably greater than 13000 deg.C. The plasma is preferably provided heated in a high pressure chamber to a temperature between 11000 ℃ and 20000 ℃. In an alternative embodiment, the plasma is heated to between 13000 ℃ and 18000 ℃. In another alternative embodiment, the plasma is heated to between 14000 ℃ and 16000 ℃. Also, lower operating current means current levels below 10 amps. The operating current supplied to the device is preferably between 4 and 8 amps. With these operating currents, the supplied voltage level is preferably between 50 and 150 volts.

Lower operating currents are often advantageous, for example, in surgical environments where it may be difficult to provide the supply requirements for higher current levels. Generally, higher operating current levels will result in awkward wiring, which may make it difficult to operate in operations requiring very high precision, such as in surgery, particularly in keyhole surgery. In certain environments and applications, higher operating currents may also present a safety hazard to the operator and/or patient.

The invention is based, for example, on the knowledge that a plasma, which is suitable, for example, for cutting actions in biological tissue, can be obtained by designing the plasma channel in a suitable manner. An advantage of the present invention is the use of a high pressure chamber and a throttle section that enable the plasma to be heated to a suitable temperature at a preferred operating current. By pressurizing the plasma upstream of the throttle section, the energy density of the plasma in the high pressure chamber can be increased. By increasing energy density is meant an increase in the amount of plasma energy per unit volume. Increasing the energy density of the plasma in the high-pressure chamber in turn enables the plasma to be heated to a higher temperature by means of an electric arc which extends between the cathode and the anode in the same direction as the plasma channel. It has also been found that increasing the pressure in the high pressure chamber is also suitable for operating the plasma-generating device at lower operating currents. Furthermore, increasing the pressure of the plasma in the high pressure chamber also makes it possible to operate the plasma generating device at a lower gas volume flow of the supplied plasma generating gas. For example, experiments have shown that a plasma boost in the high pressure chamber to about 6 bar will at least make it possible to increase the efficiency of the plasma-generating device by 30% compared to the prior art (in which the plasma channel is arranged without the high pressure chamber and without the throttling portion).

It has also been found that by pressurizing the plasma in the high pressure chamber, the power loss in the anode can be reduced compared to prior art plasma generating devices.

It is also desirable to exhaust the plasma at a lower pressure than the pressure in the high pressure chamber. For example, the increased pressure in the high pressure chamber may be detrimental to the patient in a surgical procedure, such as is performed by the plasma generating device of the present invention. It has been found, however, that a low pressure chamber arranged downstream of the throttle section reduces the increased pressure of the plasma in the high pressure chamber as it passes from the high pressure chamber to the low pressure chamber, as the plasma passes through the throttle section. When passing the flow portion, a part of the increased pressure of the plasma in the high pressure chamber will be converted into kinetic energy, and therefore the flow velocity of the plasma is accelerated in the low pressure chamber compared to the flow velocity in the high pressure chamber.

Another advantage of the plasma-generating device according to the invention is that the plasma discharged through the outlet of the plasma channel has a higher kinetic energy than the plasma in the high-pressure chamber. A plasma jet with this property can utilize the generated plasma, for example, to cut living biological tissue. The kinetic energy is preferably such as to enable the plasma jet to penetrate the object affected by the plasma jet, thereby producing a cut.

It has also been found that it is preferable to supply a lower gas volume flow to the plasma generating device in surgical applications, since a higher gas volume flow may be detrimental to the patient being treated by the generated plasma. It has been found that by means of the low gas volume flow of the plasma-generating gas supplied to the plasma-generating device, there is a risk of one or more arcs forming between the cathode and the high-pressure chamber, known as cascading arcs.

It has also been found that the risk of such a cascade arc occurring increases as the cross-section of the plasma channel decreases. The cascading arcs can negatively impact the function of the plasma device, and the high-pressure chamber can be damaged and/or degraded by the action of the arcs. And also the risk of contamination of the plasma with substances released from the high-pressure chamber, when the plasma generated in the plasma-generating device is used for surgical purposesWhich may be disadvantageous for example to the patient. Experiments have shown that when the gas volume flow is less than 1.5l/min and when the cross-section of the plasma channel is less than 1mm²The above problems may occur.

The invention is therefore also based on the knowledge that it has been found to be preferable to arrange at least one intermediate electrode in the high-voltage chamber in order to reduce the risk of the generation of such a cascade arc. It is therefore an advantage of the plasma-generating device according to the invention that the at least one intermediate electrode enables the cross-section of the high-pressure chamber to be arranged such that an arc of a suitable temperature can be obtained at the above-mentioned applied operating current level, and thus a suitable temperature of the supplied plasma. It has also been found that arranging the intermediate electrode in a high pressure chamber advantageously reduces the risk of contamination of the plasma. The intermediate electrode arranged in the high pressure chamber also helps to heat the generated plasma in a more efficient manner. In this context, an intermediate electrode means one or more electrodes arranged between a cathode and an anode. It will also be appreciated that in operation of the plasma-generating device, a voltage is applied to each intermediate electrode.

Thus, by combining the smaller cross section of the high pressure chamber and the at least one intermediate electrode arranged upstream of the restriction, the present invention provides a plasma generating device which can be used for generating plasma with a lower accidental contamination level and other advantageous properties for surgical operations, for example for cutting biological tissue. It should be understood, however, that the plasma-generating device may be used for other surgical applications as well. For example, it may be possible to generate a plasma that can be used, for example, for the vaporization or coagulation of biological tissue, by, for example, varying the operating current and/or the gas flow. Also, combinations of these applications are contemplated and in many cases they are advantageous in many fields of application.

It has also been found that the plasma-generating device provided according to the present invention is capable of controlling the change in the relationship between the thermal energy and the kinetic energy of the generated plasma in a suitable manner. It has been found that it is preferable to be able to use plasmas with different relationships between thermal and kinetic energy when treating different types of targets, such as soft and hard biological tissue. It has also been found that it is preferable to be able to vary the relationship between thermal energy and kinetic energy in accordance with the density of blood in the biological tissue to be treated. For example, it has been found that in some cases it is preferable to use a plasma with greater thermal energy when the density of blood in the tissue is higher, and a plasma with less thermal energy when the density of blood in the tissue is lower. The relationship between the thermal and kinetic energy of the generated plasma may be controlled, for example, by the level of pressure developed in the high pressure chamber, in which case the higher pressure in the high pressure chamber may cause the plasma to increase kinetic energy as it is discharged from the plasma generating device. Thus, such a change of the relation between the thermal energy and the kinetic energy of the generated plasma will for example enable the combination of cutting and coagulation in surgical applications to be adjusted in a suitable manner for treating different types of biological tissue.

Preferably, the high voltage chamber is formed mainly by the at least one intermediate electrode. By having the high pressure chamber entirely or partly constituted by said at least one intermediate electrode, the high pressure chamber obtained will effectively heat the passing plasma. Another advantage that may be obtained by arranging the intermediate electrode as part of the high voltage chamber is that the high voltage chamber can be arranged with a suitable length without the formation of a so-called cascade arc between the cathode and the inner circumferential surface of the high voltage chamber. An arc formed between the cathode and the inner peripheral surface of the high pressure chamber may damage and/or degrade the high pressure chamber, as described above.

In one embodiment of the plasma-generating device, the high pressure chamber preferably comprises a multi-electrode channel portion comprising two or more intermediate electrodes. By arranging the high pressure chamber as a multi-electrode channel portion, the high pressure chamber may have an increased length to enable heating of the supplied plasma to about the arc temperature. It has been found that the smaller the cross-section of the high pressure chamber, the longer the channel is required to heat the plasma to about the arc temperature. In tests that have been carried out, a plurality of intermediate electrodes are used to suppress the extension of the electrodes in the longitudinal direction of the plasma channel. It has been found that the use of a plurality of intermediate electrodes enables the voltage applied across each intermediate electrode to be reduced.

It has also been found that when increasing the boost of the plasma in the high pressure chamber, it is preferable to arrange a large number of intermediate electrodes between the throttle section and the cathode. Furthermore, it has been found that by using a large number of intermediate electrodes when increasing the plasma boost in the high pressure chamber, each intermediate electrode can be kept at substantially the same voltage level, which reduces the risk of generating a so-called cascade arc when boosting the plasma in the high pressure chamber.

When using high pressure chambers having a large length, it has been found that there is a risk that an arc cannot form between the cathode and the anode when the electrodes are too long. In contrast, shorter arcs may be formed between the cathode and the intermediate electrode and/or between the intermediate electrodes adjacent to each other. Therefore, it is preferable to arrange a plurality of intermediate electrodes in the high voltage chamber so as to reduce the voltage applied to each intermediate electrode. Therefore, it is preferred to use multiple intermediate electrodes when arranging a longer high pressure chamber, especially when the high pressure chamber has a smaller cross-sectional surface. In experiments it has been found to be preferable to provide a voltage of less than 22 volts to each intermediate electrode. From the preferred operating current levels described above, it was found that the voltage level across the electrodes was preferably between 15 and 22 volts/mm.

In one embodiment, the high voltage chamber is arranged as a multi-electrode channel portion comprising three or more intermediate electrodes.

In an embodiment of the plasma-generating device, the second maximum cross-sectional surface is equal to or less than 0.65mm². In one embodiment, the second maximum cross-sectional surface may be arranged such that the cross-section is at 0.05mm²And 0.44mm²In the meantime. In an alternative embodiment of the plasma-generating device, the cross-section may be arranged at 0.13mm²And 0.28mm²The surface between. By arranging the channel portion of the low-pressure chamber with such a cross-sectional surface, it is possible to generate by means of a plasmaThe outlet of the plasma channel of the generating device discharges a high-energy concentrated plasma jet. In applications for cutting biological tissue, a high energy concentrated plasma jet is particularly advantageous. The smaller cross-sectional surface of the generated plasma jet is also advantageous for processes requiring very high precision. Furthermore, a low-pressure chamber with such a cross-section enables the plasma to be accelerated and to obtain an increased kinetic energy and a reduced pressure, which is suitable, for example, when the plasma is used for surgical purposes.

The third cross-sectional surface of the throttle section is preferably at 0.008mm²And 0.12mm²Within the range of (a). In an alternative embodiment, the third cross-sectional surface of the throttle portion may be at 0.030mm²And 0.070mm²In the meantime. By arranging the throttle section with such a cross section, it has been found that an increased plasma pressure in the high-pressure chamber can be generated in a suitable manner. Furthermore, the pressurization of the plasma in the high pressure chamber affects its energy density, as described above. Thus, increasing the pressure of the plasma in the high pressure chamber through the restriction will facilitate proper heating of the plasma at the proper gas volume flow and operating current levels.

It has been found that a further advantage of the selected cross-section of the throttling portion is that the pressure in the high pressure chamber can be increased to a suitable level when the plasma flowing through the throttling portion is accelerated to a supersonic velocity (a value equal to or greater than mach number 1). It has been found that the critical pressure level required in the high pressure chamber in order to obtain a supersonic plasma in the low pressure chamber depends inter alia on the cross-sectional size and the geometric design of the throttle section. It has also been found that the critical pressure for obtaining a supersonic velocity is also affected by the type of plasma-generating gas used and the temperature of the plasma. It will be appreciated that the throttle portion always has a smaller diameter than the cross-section of the first and second largest cross-sectional surfaces in the high pressure chamber and the low pressure chamber, respectively.

Preferably, the first maximum cross-sectional surface of the high pressure chamber is at 0.03mm²And 0.65mm²Within the range of (a). Such maximum cross-section is suitable forThe plasma is heated to a suitable temperature with a suitable gas volume flow and operating current level.

It has been found that the temperature of the arc formed between the cathode and the anode depends in particular on the cross-sectional dimensions of the high-pressure chamber. The smaller cross-section of the high-pressure chamber will result in an increased energy density of the arc formed between the cathode and the anode. The temperature of the arc along the central axis of the plasma chamber is therefore proportional to the relationship between the discharge current and the cross-section of the plasma channel.

In an alternative embodiment, the high pressure chamber has a cross-section of 0.05mm²And 0.33mm²In the meantime. In an alternative embodiment, the high pressure chamber has a cross-section of 0.07mm²And 0.20mm²In the meantime.

The throttle section may preferably be arranged in the intermediate electrode. By this arrangement, the risk of the generation of a so-called cascade arc between the cathode and the throttle section is reduced. Similarly, the risk of a cascade arc between the throttling portion and the intermediate electrode which may be adjacent to it is also reduced.

Preferably, the low pressure chamber comprises at least one intermediate electrode. This means that the risk of the generation of a so-called cascade arc between the cathode and the low-pressure chamber is reduced. One or more intermediate electrodes in the low-pressure chamber also means that the risk of cascading arcs between possibly adjacent intermediate electrodes is reduced.

In a preferred manner, intermediate electrodes in the throttling portion and the low-pressure chamber can contribute to the formation of an arc between the cathode and the anode in a suitable manner. Furthermore, for some applications it may be preferred to arrange the throttle section between two intermediate electrodes. In an alternative embodiment of the plasma-generating device, the throttle section may be arranged between at least two intermediate electrodes forming part of the high-pressure chamber and at least two intermediate electrodes forming part of the low-pressure chamber.

It has been found to be preferable to design the plasma-generating device such that the major part of the plasma channel extending between the cathode and the anode is formed by the intermediate electrode. Such a channel is also suitable when the heating of the plasma can be performed along substantially the entire length of the plasma channel.

In an embodiment of the plasma-generating device, the plasma-generating device comprises at least two intermediate electrodes, preferably at least three intermediate electrodes. In an alternative embodiment the plasma-generating device comprises 2 to 10 intermediate electrodes, between 3 and 10 intermediate electrodes according to another alternative embodiment. By using such a plurality of intermediate electrodes, a plasma channel can be obtained having a suitable length for heating the plasma at a suitable gas flow rate level and operating current level. Furthermore, the intermediate electrodes are preferably separated from each other by insulator means. The intermediate electrode is preferably made of copper or a copper-containing alloy.

In one embodiment, the first maximum cross-sectional surface, the second maximum cross-sectional surface and the third cross-sectional surface are circular cross-sections transverse to the longitudinal direction of the plasma channel. By forming the plasma channel with a circular cross-section, for example, manufacturing will be easy and cost-effective.

In an alternative embodiment of the plasma-generating device, the cathode has a cathode tip tapering towards the anode, a part of the cathode tip extending over a part of the length of the plasma chamber connected to said high-pressure chamber. The plasma chamber has a fourth cross-sectional surface transverse to the longitudinal direction of the plasma channel, which fourth cross-sectional surface at the end of the cathode tip directed towards the anode is larger than the first largest cross-sectional surface. By providing the plasma generating device with such a plasma chamber, the plasma generating device can be made to have a reduced outer size. In a preferred manner, a suitable space around the cathode, in particular the tip of the cathode closest to the anode, can be provided by using a plasma chamber. The space surrounding the cathode tip suitably reduces the risk that the high temperature of the cathode during operation will damage and/or degrade the device material adjacent to the cathode. In particular, the use of a plasma chamber facilitates continuous operation over a long period of time.

A further advantage obtained by arranging the plasma chamber is that an arc to be generated between the cathode and the anode can be safely obtained, since the plasma chamber allows the cathode tip to be arranged in the vicinity of the plasma channel opening closest to the cathode without damaging and/or degrading the surrounding material due to the high temperature of the cathode. When the cathode tip is positioned too far from the opening of the plasma channel, an arc is often generated between the cathode and the surrounding structure in an unsuitable manner, which may cause incorrect operation of the device and in some cases also damage to the device.

According to a second aspect of the present invention, there is provided a plasma surgical device comprising the plasma generating device described above. Plasma surgical devices of the above-mentioned type can suitably be used for destroying or coagulating biological tissue, in particular for cutting. Moreover, such a plasma surgical device can be advantageously used in cardiac or brain surgery. Alternatively, such a plasma surgical device can be advantageously used for liver, spleen or kidney surgery.

According to a third aspect of the invention, a method of generating a plasma is provided. The method comprises supplying a plasma generating gas to the plasma generating device at a gas volume flow rate of 0.05l/min to 1.00l/min at an operating current of 4 to 10 amperes. Such plasma-generating gases preferably include inert gases such as argon, neon, xenon, helium, and the like. The method of generating plasma in this way can be used in particular for cutting biological tissue.

In an alternative embodiment, the supply flow of the plasma-generating gas can be between 0.10l/min and 0.80 l/min. In an alternative embodiment, the supply flow of the plasma-generating gas can be between 0.15l/min and 0.50 l/min.

According to a fourth aspect of the present invention there is provided a method of generating a plasma from a plasma-generating device comprising an anode, a cathode and a plasma channel extending substantially in a direction from the cathode to the anode, the method comprising: providing a plasma flowing from the cathode to the anode; increasing the energy density of the plasma by pressurizing the plasma in a high pressure chamber located upstream of a throttle section arranged in the plasma channel; heating the plasma by using at least one intermediate electrode arranged upstream of the throttling portion; and depressurizing and accelerating the plasma by passing the plasma through the throttling portion and discharging the plasma through the outlet opening of the plasma channel.

By this method, a substantially contamination free plasma can be generated and the plasma can be heated to a suitable temperature and with suitable kinetic energy at suitable operating current and gas flow levels, as described above.

The pressurisation of the plasma in the high pressure chamber preferably comprises generating a pressure between 3 and 8 bar, preferably 5-6 bar. Such a pressure level is preferably such that the plasma has an energy density that enables heating to a suitable temperature at a suitable operating current level. It has also been found that such pressure levels enable the plasma in the vicinity of the throttle portion to accelerate to supersonic speeds.

The plasma is preferably depressurized to a pressure level of less than 2 bar, optionally 0.25-1 bar, and optionally 0.5-1 bar, above the atmospheric pressure outside the outlet opening of the plasma channel. By reducing the pressure of the plasma discharged from the outlet opening of the plasma channel to this level, the risk of the pressure of the plasma harming the patient being treated surgically by means of the generated plasma jet will be reduced.

By increasing the pressure of the plasma in the high pressure chamber, the plasma flowing through the plasma channel can be accelerated to a supersonic velocity near the throttle section having a value equal to or greater than mach 1. The pressure required to achieve a velocity in excess of mach 1 depends inter alia on the pressure of the plasma and the type of plasma-generating gas supplied. Furthermore, the required pressure in the high pressure chamber depends on the cross sectional surface and the geometric design of the throttle section. Preferably, the plasma is accelerated to a flow velocity of 1-3 times supersonic velocity, which is a flow velocity between mach 1 and mach 3.

Preferably, the plasma is heated to a temperature between 11000 ℃ and 20000 ℃, preferably 13000 ℃ to 18000 ℃, in particular 14000 ℃ to 16000 ℃. Such a temperature level is suitable, for example, for enabling the generated plasma to be used for cutting biological tissue.

In order to generate and provide plasma, the plasma-generating gas may be suitably supplied to the plasma-generating device. It has been found that it is preferred to provide such a plasma-generating gas at a flow rate of between 0.05l/min and 1.00l/min, preferably 0.10-0.80l/min, especially 0.15-0.50 l/min. With such a level of flow of the plasma generating gas it was found that the generated plasma can be heated to a suitable temperature at a suitable operating current level. The above-mentioned flow levels are also suitable for making the plasma for surgical use, since it reduces the risk of injury to the patient.

When discharging the plasma through the outlet opening of the plasma channel, it is preferred that the plasma is discharged as a plasma jet having a cross-section of less than 0.65mm²Preferably at 0.05mm²And 0.44mm²In particular 0.13-0.28mm². Furthermore, the plasma-generating device is preferably supplied with an operating current of between 4 and 10 amperes, preferably 4-8 amperes.

According to another aspect of the present invention, the above-described method of generating plasma may be used in a method of cutting biological tissue.

Drawings

The invention will now be described in more detail with reference to the accompanying drawings, which show by way of example a presently preferred embodiment of the invention.

FIG. 1a is a cross-sectional view of an embodiment of a plasma generating device of the present invention;

FIG. 1b is an enlarged view of a portion of the embodiment of FIG. 1 a;

FIG. 1c is an enlarged partial view of a throttle section arranged in the plasma channel of the plasma-generating device of FIG. 1 a;

FIG. 2 shows an alternative embodiment of a plasma-generating device;

FIG. 3 shows another alternative embodiment of a plasma-generating device;

FIG. 4 shows, by way of example, a diagram of suitable power levels for affecting biological tissue in different ways; and

fig. 5 shows a diagram of the relationship between the temperature of the plasma jet and the gas volume flow rate at which the plasma-generating gas is supplied to the plasma-generating device at different operating power levels.

Detailed Description

Fig. 1a shows a cross-sectional view of an embodiment of a plasma-generating device 1 according to the invention. The section in fig. 1a passes through the center of the plasma-generating device 1 in the longitudinal direction. The apparatus comprises an elongate end sleeve 3, the end sleeve 3 housing a plasma generating system for generating a plasma which is discharged at the end of the end sleeve 3. The generated plasma may be used, for example, to stop bleeding in tissue, vaporize tissue, cut tissue, and the like.

The plasma-generating device 1 of fig. 1a comprises a cathode 5, an anode 7 and a plurality of electrodes 9, 9', 9 ", which are arranged between the anode and the cathode, herein referred to as intermediate electrodes. The intermediate electrode 9, 9', 9 "is annular and forms part of a plasma channel 11, which plasma channel 11 extends from a position in front of the cathode 5 and towards the anode 7 and through the anode 7. The inlet end of the plasma channel 11 is positioned close to the cathode 5, the plasma channel 11 extending through the anode 7, its outlet opening being arranged at the anode 7. In the plasma channel 11 the plasma will be heated and eventually flow out through the plasma channel opening in the anode 7. The intermediate electrodes 9, 9 ', 9 "are insulated and separated from each other by means of annular insulator means 13, 13', 13". The shape of the intermediate electrode 9, 9', 9 "and the size of the plasma channel 11 can be adjusted to suit the desired purpose. The number of intermediate electrodes 9, 9', 9 "may also be varied in an alternative manner. The embodiment shown in fig. 1a is provided with three intermediate electrodes 9, 9', 9 ".

In the embodiment shown in fig. 1a, the cathode 5 is formed as an elongated cylindrical element. Preferably, the cathode 5 is made of tungsten, optionally with additives such as lanthanum. Such additives may be used, for example, to reduce the temperature generated at the end 15 of the cathode 5.

Furthermore, the end 15 of the cathode 5 directed towards the anode 7 has a tapered end portion. The tapered portion 15 is suitably formed at the tip at the end of the cathode as shown in fig. 1 a. The cathode tip 15 is preferably conical in shape. The cathode tip 15 may also be part of a cone or may alternatively be shaped in a geometry tapering towards the anode 7.

The other end of the cathode 5, which is directed away from the anode 7, is connected to an electrical conductor, which is to be connected to a power supply. The conductor is preferably surrounded by an insulator (the conductor is not shown in fig. 1 a).

The plasma chamber 17 is connected to the inlet end of the plasma channel 11 and has a cross-sectional surface transversely to the longitudinal direction of the plasma channel 11 which exceeds the cross-sectional surface of the plasma channel 11 at the inlet end. The plasma chamber 17 shown in figure 1a has a circular cross-section transverse to the longitudinal direction of the plasma channel 11 and has a length L in the longitudinal direction of the plasma channel 11_chThe length corresponding approximately to the diameter D of the plasma chamber 17_ch. The plasma chamber 17 and the plasma channel 11 are arranged substantially concentrically with respect to one another. The cathode 5 projects into the plasmaAt least the length L of the plasma chamber 17 within the chamber 17_chAnd the cathode 5 is arranged substantially concentrically with the plasma chamber 17. The plasma chamber 17 comprises a recess integrated in the first intermediate electrode 9, which first intermediate electrode 9 is positioned closest to the cathode 5.

Fig. 1a also shows an insulator element 19, which insulator element 19 extends along a part of the cathode 5 and surrounds it. The insulator element 19 is preferably formed as an elongated cylindrical sleeve and the cathode 5 is partly located in a circular hole extending through the tubular insulator element 19. The cathode 5 is arranged substantially in the centre of the through hole of the insulator element 19. Also, the inner diameter of the insulator element 19 is slightly larger than the outer diameter of the cathode 5, so that a certain distance is formed between the outer circumferential surface of the cathode 5 and the inner surface of the circular hole of the insulator element 19.

Preferably, the insulator element 19 is made of a heat resistant material, such as a ceramic material, a heat resistant plastic material or the like. The insulator element 19 will protect the adjoining parts of the plasma-generating device 1 from high temperatures which may occur, for example, around the cathode 5, in particular around the cathode tip 15.

The insulator element 19 and the cathode 5 are arranged relative to each other such that the end 15 of the cathode 5 directed towards the anode 7 projects beyond an end surface 21 of the insulator element 19, which end surface 21 is directed towards the anode 7. In the embodiment shown in fig. 1a, about half of the tapered tip 15 of the cathode 5 protrudes beyond the end surface 21 of the insulator element 19.

A gas supply portion (not shown in fig. 1) is connected to the plasma generation portion. The gas supplied to the plasma generating device 1 is preferably a gas including the same type of gas as the gas used as the plasma generating gas of the prior art apparatus, for example, an inert gas such as argon, neon, xenon, helium, or the like. The plasma-generating gas can flow through the gas supply portion and into the space arranged between the cathode 5 and the insulator element 19. Thus, the plasma-generating gas flows along the cathode 5 inside the insulator element 19 towards the anode 7. When the plasma-generating gas passes the end of the insulator element 19, which is located closest to the anode 7, the gas enters the plasma chamber 17.

The plasma-generating device 1 further comprises one or more coolant channels 23 extending into the elongated end sleeve 3. The coolant channel 23 is preferably partly formed in one piece with the housing (not shown) of the connecting end sleeve 3. The end sleeve 3 and the housing may be connected to each other by means of a threaded joint, for example, but other connection methods, such as welding, brazing, etc., are also conceivable. Furthermore, the end sleeve preferably has an outer dimension of less than 10mm, preferably less than 5 mm. At least the housing part at the end sleeve preferably has an outer shape and dimensions substantially corresponding to the outer shape and dimensions of the end sleeve. In the embodiment of the plasma-generating device shown in fig. 1a, the end sleeve has a circular cross-section transverse to the longitudinal direction of the plasma channel 11.

In one embodiment the plasma-generating device 1 comprises two additional channels 23, one constituting an inlet channel and the other constituting an outlet channel, for a coolant. The inlet channel and the outlet channel communicate with each other in order to enable the coolant to pass through the end sleeve 3 of the plasma-generating device 1. It is also possible to provide the plasma-generating device 1 with more than two cooling channels for supplying or discharging a cooling agent. Preferably, water is used as the coolant, although other types of fluids are also contemplated. The cooling channels are arranged so that the coolant is supplied to the end sleeve 3 and flows between the intermediate electrode 9, 9', 9 "and the inner wall of the end sleeve 3. The interior of the end sleeve 3 constitutes the area where the at least two additional channels are connected to each other.

The intermediate electrode 9, 9', 9 "is arranged inside the end sleeve 3 of the plasma-generating device 1 and is positioned substantially concentrically with the end sleeve 3. The outer diameter of the intermediate electrode 9, 9', 9 "forms a space between the outer surface of the intermediate electrode and the inner wall of the end sleeve 3 with respect to the inner diameter of the sleeve 3. In this space, the coolant fed from the additional channel 23 can flow between the intermediate electrode 9, 9', 9 "and the end sleeve 3.

The additional channels 23 may have different numbers and different cross sections. It is also possible to have all or some of the additional channels 23 for other purposes. For example, three additional channels 23 can be arranged, wherein, for example, two are used for supplying and discharging coolant, one is used for sucking liquid from the surgical field, etc.

In the embodiment shown in fig. 1a, the three intermediate electrodes 9, 9 ', 9 "are separated by insulator means 13, 13', 13" arranged between the cathode 5 and the anode 7. It is however to be understood that the number of electrodes 9, 9', 9 "may be chosen for any suitable purpose. The mutually adjacent intermediate electrodes and the insulator means arranged therebetween are preferably press-fitted to each other.

The electrode 9 "furthest away from the cathode 5 is in contact with an annular insulator means 13", which annular insulator means 13 "is arranged against the anode 7.

The anode 7 is connected to the elongate end sleeve 3. In the embodiment shown in fig. 1a, the anode 7 and the end sleeve 3 are formed integrally with each other. In an alternative embodiment, the anode 7 may be formed as a separate element, which is connected to the end sleeve 3 by means of a threaded connection between the anode 7 and the end sleeve 3, by means of welding, by means of brazing. The connection between the anode 7 and the end sleeve 3 is preferred so that an electrical contact between them will be provided.

The plasma-generating device 1 shown in fig. 1a has a plasma channel 11, which plasma channel 11 has a high-pressure chamber 25, a throttle section 27 and a low-pressure chamber 29. The throttle portion 27 is located between the high pressure chamber 25 and the low pressure chamber 29. In this context, the high-pressure chamber 25 means the part of the plasma channel 11 which is located upstream of the throttling portion 27 in the direction of flow of the plasma from the cathode 5 to the anode 7. By low-pressure chamber 29 is meant the part of the plasma channel 11 located downstream of the throttle section 27.

The throttle section 27 shown in figure 1a constitutes the smallest cross-section of the plasma channel 11. The cross section of the throttling portion 27 is therefore smaller than the largest cross section of the high-pressure chamber 25 and the largest cross section of the low-pressure chamber 29 (transversely to the longitudinal direction of the plasma channel). As shown in fig. 1a and 1c, it is preferred that the throttling portion is a supersonic or laval nozzle.

The throttle section 27 is such that the pressure in the high pressure chamber 25 will increase relative to the pressure in the low pressure chamber 29. When the plasma flows through the throttling part 27, the flow rate of the plasma is accelerated, and the pressure of the plasma is lowered. The plasma discharged through the opening of the plasma channel 11 in the anode 7 therefore has a higher kinetic energy and a lower pressure than the plasma in the high-pressure chamber 25. According to the plasma-generating device shown in fig. 1a, the cross-sectional surface of the opening of the plasma channel 11 in the anode 7 is the same as the largest cross-sectional surface of the low-pressure chamber 29.

In the embodiment shown in fig. 1a, the plasma channel 11 is preferably formed such that the plasma channel 11 gradually decreases towards the smallest cross-section of the throttle section and then gradually increases again in cross-section. Such a shape of the plasma channel 11 in the vicinity of the throttle section 27 reduces, for example, turbulence in the plasma. This is advantageous because otherwise turbulence may reduce the flow rate of the plasma.

In the enlarged detail shown in fig. 1c, the plasma channel 11 has a converging channel section upstream of the smallest cross-sectional surface of the throttle section 27, seen in the flow direction of the plasma. Furthermore, the plasma channel 11 has a diverging channel section downstream of the throttling section 27. In the embodiment shown in figure 1c the diverging portion of the plasma channel 11 has a shorter length in the longitudinal direction of the plasma channel 11 than the converging portion.

For the design of the plasma channel 11 in the vicinity of the throttle section 27, it has been found that in the embodiment of the plasma-generating device shown in figure 1c it is possible to accelerate the plasma in the throttle section 27 to a supersonic velocity with a value equal to or greater than mach number 1.

The plasma channel 11 shown in figure 1a is of circular cross-section. Preferably, the maximum diameter of the high pressure chamber is between 0.20mm and 0.90mm, preferably 0.25-0.65mm, especially 0.30-0.50 mm. Furthermore, it is preferred that the maximum diameter of the low pressure chamber is between 0.20mm and 0.90mm, preferably 0.25-0.75mm, in particular 0.40-0.60 mm. Preferably, the minimum diameter of the throttling portion is between 0.10mm and 0.40mm, preferably 0.20-0.30 mm.

The exemplary embodiment of the plasma-generating device 1 shown in fig. 1a has a high-pressure chamber 25 with a diameter of 0.4 mm. In the embodiment shown in fig. 1a, the diameter of the low pressure chamber 29 is 0.50mm and the diameter of the restriction 27 is 0.27 mm.

In the embodiment of the plasma-generating device shown in fig. 1a, the throttle section 27 is located substantially in the centre of the length of the plasma channel in the longitudinal direction. It has been found, however, that the relation between the kinetic energy and the thermal energy of the plasma can vary depending on the position of the throttling portion 27 in the plasma channel 11.

Fig. 2 is a cross-sectional view of an alternative embodiment of the plasma-generating device 101. In the embodiment shown in fig. 2, the throttle section 127 is located in the anode 107 near the outlet opening of the plasma channel 111. By arranging the throttling portion 127 far downstream in the longitudinal direction of the plasma channel 111, e.g. in the anode 107 or in the vicinity of the anode 107, the plasma obtained at the opening of the plasma channel 111 has a higher kinetic energy than the plasma-generating device 1 shown in fig. 1 a. It has been found that certain types of tissue (e.g., soft tissue such as liver tissue) can be more easily cut by plasmas having higher kinetic energy. For example, it was found preferable to generate a plasma comprising about half the thermal energy and half the kinetic energy for the cutting.

Furthermore, the alternative embodiment of the plasma-generating device 101 in fig. 2 comprises 7 intermediate electrodes 109. It should be appreciated, however, that the embodiment of the plasma-generating device 101 in fig. 2 may alternatively be arranged with more or less than 7 intermediate electrodes 109.

Fig. 3 shows another alternative embodiment of a plasma-generating device 201. In an alternative embodiment shown in fig. 3, the throttle section 227 is arranged in the first intermediate electrode 209 closest to the cathode 205. By arranging the throttling portion 227 considerably upstream along the length of the plasma channel 211, the obtained plasma will have a lower kinetic energy when discharged through the outlet opening of the plasma channel 211 than in the embodiment of fig. 1a and 2. It has been found that, for example, certain hard tissues (e.g., bone) can be more easily cut by plasmas having higher thermal and lower kinetic energies. For example, it has been found preferable to generate a plasma comprising about 80-90% thermal energy and 10-20% kinetic energy for the cutting.

Furthermore, an alternative embodiment of the plasma-generating device 201 of fig. 2 comprises 5 intermediate electrodes 209. It should be appreciated, however, that the embodiment of the plasma-generating device 201 in fig. 2 may alternatively be arranged with more or less than 5 intermediate electrodes 209.

It should be noted that the throttling portion 27, 127, 227 may be arranged at a selected position in the plasma channel 11, 111, 211 depending on the appropriate characteristics of the generated plasma. Moreover, it should be appreciated that the embodiments shown in FIGS. 2-3 may be arranged in a similar manner to the embodiments in FIGS. 1a-1c, except for the differences described above.

Figure 4 shows an example of suitable power levels to obtain different effects on biological tissue. Fig. 4 shows how these power levels relate to different diameters of the plasma jet discharged through the plasma channel 1, 111, 211 of the plasma-generating device 1, 101, 201 described above. In order to obtain different effects on living tissue (e.g. coagulation, vaporisation and cutting), a suitable power level is shown in fig. 4. These different types of effects can be obtained at different power levels depending on the diameter of the plasma jet. In order to reduce the required operating current, it has been found to be preferable to reduce the diameter of the plasma channel 11, 111, 211 of the plasma-generating device and thus the diameter of the plasma jet generated by the device, as shown in fig. 4.

Fig. 5 shows the relationship between the temperature of the plasma jet and the volume flow rate of the gas (for example, argon gas) for generating the plasma supplied to the plasma generating apparatus 1, 101, 201. In order to obtain a suitable effect (e.g. condensation, vaporisation or cutting), it was found to be preferable to use a specific supplied gas volume flow at different power levels, as shown in fig. 5. In order to generate a plasma with a suitable temperature at a suitable power level, it has been found preferable to provide a plasma generating gas with a lower gas volume flow, as described herein above. In order to reduce the required operating current, it is preferable to reduce the gas volume flow rate of the plasma-generating gas supplied to the plasma generation devices 1, 101, and 201. A higher gas volume flow may also be disadvantageous, for example, for the patient being treated, and therefore the gas volume flow should be kept low.

Thus, the plasma-generating device 1, 101, 201 in the embodiment shown in fig. 1a-3 can generate plasma having these characteristics. It has also been found advantageous to provide a plasma-generating device 1, 101, 201 that can be used to cut e.g. living biological tissue at a suitable operating current and gas volume flow.

Suitable geometrical relations between the components comprised in the plasma-generating device 1, 101, 201 will be described below with reference to fig. 1a-1 b. It should be noted that the dimensions described below constitute only an exemplary embodiment of the plasma-generating device 1, 101, 201 and can vary according to the field of application and the desired characteristics. It should be understood that the examples described in fig. 1a-b can also be used in the embodiments of fig. 2-3.

Inner diameter d of the insulator element 19_iIs only slightly larger than the outer diameter d of the cathode 5_c. In one embodiment, the difference in cross-section between the cathode 5 and the insulator element 19 in the common cross-section is preferably equal to or greater than the cross-section of the inlet of the plasma channel 11 near the cathode 5.

In the embodiment shown in fig. 1b, the outer diameter d of the cathode 5_cAbout 0.50mm, the inner diameter d of the insulator element 19_iIs about 0.80 mm.

In one embodiment, the cathode 5 is arranged such that a partial length of the cathode tip 15 projects beyond the boundary surface 21 of the insulator element 19. In fig. 1b, the tip 15 of the cathode 5 is positionedThus, the length L of the tip 15_cProjects beyond the boundary surface 21 of the insulator element 19. In the embodiment shown in FIG. 1b, the protrusion l_cApproximately corresponding to the diameter d of the cathode 5_c。

Total length L of cathode tip 15_cPreferably larger than the diameter d of the cathode 5 at the base of the cathode tip 15_c1.5 times of the total weight of the powder. Preferably, the total length L of the cathode tip 15_cIs the diameter d of the cathode 5 at the base of the cathode tip 15_c1.5-3 times of the total weight of the composition. In the embodiment shown in FIG. 1b, the length L of the cathode tip 15_cCorresponding to the diameter d of the cathode 5 at the base of the cathode tip 15_cAbout 2 times higher.

In one embodiment, the diameter d of the cathode 5_cAt the base of the cathode tip 15, about 0.3-0.6 mm. In the embodiment shown in fig. 1b, the diameter d of the cathode 5_cAt the base of the cathode tip 15 is about 0.50 mm. Preferably, the cathode has substantially the same diameter d between the base of the cathode tip 15 and the end of the cathode 5 opposite the cathode tip 15_c. However, it will be appreciated that the diameter d may vary along the length of the cathode 5_c。

In one embodiment, the diameter D of the plasma chamber 17_chCorresponding to the diameter d of the cathode 5 at the base of the cathode tip 15_cAbout 2-2.5 times. In the embodiment shown in fig. 1b, the diameter D of the plasma chamber 17_chCorresponding to the diameter d of the cathode 5_cAbout 2 times higher.

The length L of the plasma chamber 17 in the longitudinal direction of the plasma-generating device 1_chCorresponding to the diameter d of the cathode 5 at the base of the cathode tip 15_cAbout 2-2.5 times. In the embodiment shown in fig. 1b, the length L of the plasma chamber 17_chApproximately corresponding to the diameter D of the plasma chamber 17_ch。

In one embodiment, the length L of the tip 15 of the cathode 5 in the plasma chamber 17_chExtend over, or over, said halfLength. In an alternative embodiment, the length L of the tip 15 of the cathode 5 in the plasma chamber 17_ch1/2 to 2/3. In the embodiment shown in fig. 1b, the cathode tip 15 is at least over the length L of the plasma chamber 17_chExtend over half of it.

In the embodiment shown in fig. 1b, the cathode 5 projecting into the plasma chamber 17 is positioned at a distance from the end of the plasma chamber 17 closest to the anode 7 corresponding approximately to the diameter d of the cathode 5 at the base_c。

In the embodiment shown in fig. 1b, the plasma chamber 17 is in fluid communication with the high pressure chamber 25 of the plasma channel 11. The high pressure chamber 25 is preferably of diameter d_chAbout 0.2-0.5 mm. In the embodiment shown in fig. 1b, the diameter d of the high-pressure chamber 25_chIs about 0.40 mm. It should be noted, however, that the diameter d of the high-pressure chamber 25_chMay be varied in different ways along the length of the high pressure chamber 25 to provide different desired characteristics.

Between the plasma chamber 17 and the high-pressure chamber 25, a transition 31 is arranged, which transition 31 forms the diameter D of the plasma chamber 17_chAnd diameter d of high pressure chamber 25_chIn the direction from the cathode 5 to the anode 7. The transition portion 31 may be designed in a number of alternative ways. In the embodiment shown in fig. 1b, the transition portion 31 is designed as a beveled edge formed at the inner diameter D of the plasma chamber 17_chAnd the inner diameter d of the high-pressure chamber 25_chTo transition between them. It should be noted, however, that the plasma chamber 17 and the high pressure chamber 25 may be arranged in direct contact with each other without a transition portion 31 arranged therebetween. The use of the transition section 31 shown in fig. 1b advantageously enables heat to be extracted in order to cool the plasma chamber 17 and the structures in the vicinity of the high-pressure chamber 25.

Preferably, the plasma-generating device 1 may be provided as part of a disposable instrument. For example, the entire apparatus having the plasma generating apparatus 1, the housing, the tube, the connection terminal, and the like may be sold as a disposable instrument. Alternatively, only the plasma-generating device may be disposable and connected to the multi-use device.

Other embodiments and variations are also contemplated as being within the scope of the present invention. For example, the number and shape of the electrodes 9 ', 9 ", 99'" may vary depending on the type of plasma-generating gas used and the characteristics of the plasma desired to be generated.

In use, a plasma-generating gas (e.g. argon) is supplied through the gas supply to the space between the cathode 5 and the insulator element 19, as described above. The supplied plasma-generating gas passes through the plasma chamber 17 and the plasma channel 11 in order to be discharged through the opening of the plasma channel 11 in the anode 7. When the gas supply is established, the voltage system is opened, which starts the discharge process in the plasma channel 11 and forms an arc between the cathode 5 and the anode 7. Before establishing the arc, coolant is preferably supplied to the plasma-generating device 1 through the coolant channel 23, as described above. When the arc is established, a gas plasma is generated in the plasma chamber 17 and during heating passes through the plasma channel 11 and leads to the opening in the anode 7.

Suitable operating currents for the plasma-generating device 1, 101, 201 of fig. 1-3 are 4-10 amperes, preferably 4-8 amperes. The operating voltage of the plasma-generating device 1, 101, 201 depends inter alia on the number of intermediate electrodes and the length of the intermediate electrodes. The relatively small diameter of the plasma channel enables a relatively low energy consumption and a relatively low operating current when using the plasma-generating device 1, 101, 201.

When an arc is formed between the cathode 5 and the anode 7, the temperature T is mainly centered along the central axis of the plasma channel and related to the discharge current I and the diameter d of the plasma channel_chThe relation between them is proportional (T ═ K < I >/d_ch). In order to provide a higher temperature plasma (e.g. 11000 ℃ to 20000 ℃) at a relatively low current, at the outlet of the plasma channel in the anode 7, the cross-section of the plasma channel(and hence the cross-section of the arc heating the gas) is smaller. By means of the smaller cross-section arc, the electric field strength in the plasma channel has a higher value.

The different embodiments of the plasma-generating device of fig. 1a-3 can be used not only for cutting living biological tissue, but also for coagulation and/or vaporization. By simply moving the hand, the operator can appropriately switch the plasma generating device between condensation, vaporization, and condensation.

Claims (41)

1. A plasma generating apparatus comprising:

an anode;

a cathode; and

a plasma channel extending longitudinally between said cathode and said anode and through said anode and having an outlet opening at the end furthest from said cathode, a portion of said plasma channel being formed by one or more intermediate electrodes electrically insulated from each other and said anode;

the plasma channel has a throttling portion, which divides the plasma channel into:

(1) a high pressure chamber having a first maximum cross-sectional surface transverse to the longitudinal direction of the plasma channel, said high pressure chamber being located on the side of the throttling portion closest to the cathode; and

(2) a low pressure chamber having a second largest cross-sectional surface transverse to the longitudinal direction of the plasma channel, said low pressure chamber being located on the side of the throttling portion furthest from the cathode;

said throttling portion having a third cross-sectional surface transverse to the longitudinal direction of the plasma channel, which third cross-sectional surface is smaller than said first maximum cross-sectional surface and said second maximum cross-sectional surface; the throttling portion is located remotely downstream in the longitudinal direction of the plasma channel, in or near the anode.

2. The plasma generating apparatus according to claim 1, wherein: the throttling portion is a laval nozzle.

3. The plasma generating apparatus according to claim 1, wherein: the throttling portion is a supersonic nozzle.

4. The plasma generating apparatus according to claim 1, wherein: the high voltage chamber is substantially formed by the at least one intermediate electrode.

5. The plasma generating apparatus according to claim 1, wherein: the high voltage chamber is formed by two or more intermediate electrodes.

6. The plasma generating apparatus according to claim 1, wherein: the high voltage chamber is formed by three or more intermediate electrodes.

7. The method of claim 1A plasma generating apparatus, wherein: the second maximum cross-sectional surface is less than or equal to 0.65mm²。

8. The plasma generating apparatus according to claim 1, wherein: the third cross-sectional surface is at 0.008mm²And 0.12mm²In the meantime.

9. The plasma generating apparatus according to claim 1, wherein: the first maximum cross-sectional surface is at 0.03mm²And 0.65mm²In the meantime.

10. The plasma generating apparatus according to claim 1, wherein: the throttle portion is formed by the intermediate electrode.

11. The plasma generating apparatus according to claim 1, wherein: the low pressure chamber is formed by at least one intermediate electrode.

12. The plasma generating apparatus according to claim 1, wherein: the throttle portion is arranged between the two intermediate electrodes in the longitudinal direction.

13. The plasma generating apparatus according to claim 1, wherein: the throttle portion is arranged longitudinally between at least two intermediate electrodes forming part of the high pressure chamber and at least two intermediate electrodes forming part of the low pressure chamber.

14. The plasma generating apparatus according to claim 1, wherein: the portion of the plasma channel formed by one or more intermediate electrodes is formed by two or more intermediate electrodes.

15. The plasma generating apparatus of claim 14, wherein: the portion of the plasma channel formed by one or more intermediate electrodes is formed by 3-10 intermediate electrodes.

16. The plasma generating apparatus according to claim 1, wherein: the first maximum cross-sectional surface, the second maximum cross-sectional surface, and the third cross-sectional surface are circular.

17. The plasma generating apparatus of claim 1, further comprising: a plasma chamber connected to the high pressure chamber,

wherein the cathode has a tip, the tip being the portion of the cathode closest to the anode and tapering towards the anode, a portion of the cathode tip extending over a portion of the length of the plasma chamber;

wherein the plasma chamber has a fourth cross-sectional surface transverse to the longitudinal direction of the plasma channel, said fourth cross-sectional surface at the end of the cathode tip closest to the anode being larger than said first maximum cross-sectional surface.

18. A plasma surgical device comprising the plasma generating device of claim 1.

19. A method of generating a plasma, comprising: supplying a plasma-generating gas stream to the plasma-generating device of claim 1 at a rate of 0.05l/min to 1.00l/min at an operating current of 4-10 amps.

20. The method of claim 19, wherein: the plasma-generating gas is an inert gas.

21. The method of claim 19, wherein: the plasma generating gas is argon.

22. A method of generating a plasma using a plasma-generating device comprising an anode, a cathode and a plasma channel extending longitudinally between and through said cathode and having an outlet opening at an end furthest from said cathode, a portion of said plasma channel being formed by one or more intermediate electrodes electrically insulated from each other and said anode, said plasma channel having a throttling portion dividing said plasma channel into a high pressure chamber located on a side of the throttling portion closest to the cathode and a low pressure chamber located on a side of the throttling portion furthest from the cathode, the method comprising:

providing a plasma into a high pressure chamber;

pressurizing the plasma in the high pressure chamber;

heating the plasma by one or more intermediate electrodes;

passing the plasma through the throttling portion after pressurizing the plasma; and

the plasma is then discharged through the outlet opening of the plasma channel.

23. The method of claim 22, wherein: increasing the energy density of the plasma comprises pressurizing the plasma in the high pressure chamber to a pressure between 3 and 8 bar.

24. The method of claim 23, wherein: the pressure is between 5 and 6 bar.

25. The method of claim 22, wherein: the depressurizing of the plasma comprises reducing the pressure of the plasma to a pressure less than 2 bar above the atmospheric pressure outside the outlet opening of the plasma device.

26. The method of claim 25, wherein: the overpressure is 0.25-1 bar.

27. The method of claim 26, wherein: the overpressure is 0.5-1 bar.

28. The method of claim 22, wherein: the step of accelerating the plasma includes accelerating the plasma to a velocity equal to or greater than mach number 1 near the throttle portion.

29. The method of claim 28, wherein: the velocity is 1-3 times supersonic.

30. The method of claim 22, wherein: the heating of the plasma comprises heating the plasma to a temperature between 11000 ℃ and 20000 ℃.

31. The method of claim 30, wherein: the temperature was 13000-18000 ℃.

32. The method of claim 31, wherein: the temperature was 14000-.

33. The method of claim 22, further comprising: a plasma generating gas is provided.

34. The method of claim 33, wherein: the flow rate of the plasma-generating gas is between 0.05l/min and 1.0 l/min.

35. The method of claim 34, wherein: the flow rate is between 0.1l/min and 0.80 l/min.

36. The method of claim 35, wherein: the flow rate is between 0.15l/min and 0.50 l/min.

37. The method of claim 22, further comprising: discharging the plasma as a plasma jet having a cross-section of less than 0.65mm²。

38. The method of claim 37, wherein: the cross section is 0.07mm²And 0.50mm²In the meantime.

39. The method of claim 38, wherein: the cross section is 0.13mm²And 0.30mm²In the meantime.

40. The method of claim 22, further comprising: an operating current of between 4 and 10 amps is supplied to the plasma-generating device.

41. The method of claim 40, wherein: the operating current is 4-8 amperes.