阅读说明：本技术 一种低温范围的裸露电极型大气压等离子体发生器系统 (Exposed electrode type atmospheric pressure plasma generator system in low temperature range ) 是由 李和平 李静 陈坚 方川 于 2020-06-05 设计创作，主要内容包括：一种低温范围的裸露电极型大气压等离子体发生器系统属于大气压射频等离子体技术领域,其特征在于包括电源、气源、发生器、等离子体气体温度调节器,输出等离子体调节接头以及处理器,其中,发生器具有同轴型电极,内电极纵剖面呈“U”字形,冷却气体进入凹槽后通过沿径向开在内电极内的多层冷却通道后进入等离子体空间,以补充等离子体输出流量,所述调节接头用于调节输出等离子体纵向高度及输出角度,处理器把输出等离子体分为[-200℃,0℃],(0℃,50℃]两档分档处理,对输出等离子体气体温度和流量两个参量按优先级控制,据此确定非最优参量的修正期望值。本发明具有发生器结构简单、输出等离子体可调节及调节对象针对性、选择性强的优点。(The invention relates to a low-temperature range exposed electrode type atmospheric pressure plasma generator, which belongs to the technical field of atmospheric pressure radio frequency plasma, and is characterized by comprising a power supply, a gas source, a generator, a plasma gas temperature regulator, an output plasma regulating joint and a processor, wherein the generator is provided with a coaxial electrode, the longitudinal section of an inner electrode is U-shaped, cooling gas enters a groove and then enters a plasma space through a plurality of layers of cooling channels which are radially opened in the inner electrode to supplement the output flow of the plasma, the regulating joint is used for regulating the longitudinal height and the output angle of the output plasma, the processor divides the output plasma into [ -200 ℃ and 0 ℃) and (0 ℃ and 50 ℃) for grading treatment, controls the temperature and the flow of the output plasma gas according to priority, and accordingly determines the correction expected value of a non-optimal parameter The output plasma can be adjusted, and the pertinence and the selectivity of an adjusting object are strong.)

1. A naked electrode type atmospheric pressure plasma generator system with low temperature range is characterized in that the temperature of output plasma gas is within-200 ℃ and 50 ℃, and comprises a power supply (1), a gas source (2), a plasma generator (3), an output plasma adjusting joint (4), a joint for short, a plasma gas temperature regulator (5) and a processor (6), wherein the plasma gas temperature regulator

The power supply (1) is a radio frequency power supply with the frequency of 13.56MHz and the maximum output power of 1kW,

the gas source (2) is a helium tank filled with helium gas with the temperature of-268.8 ℃, and is provided with a working medium gas output end and an electrode cooling gas output end,

the plasma generator (3) is a coaxial bare electrode generator, and comprises an inner electrode (31), an outer electrode (32) and a shell (33), wherein

The inner electrode (31) is cylindrical, the longitudinal section of the inner electrode is U-shaped, the inner electrode comprises an electrode cooling gas input channel (311), a power supply connector (312), an inner electrode cooling channel (313) and a plasma space (314), wherein the electrode cooling gas input channel (311) and the power supply connector (312) respectively penetrate through the bottom of the U-shaped section along the left side and the right side in the longitudinal direction, the inner electrode cooling channel (313) penetrates through the cylindrical surface of the inner electrode along the radial direction of the inner electrode (31) layer by layer from top to bottom along the side surface of the inner electrode, and the cross section of the inner electrode is annularly distributed,

the outer electrode (32) is a cylinder which is penetrated through up and down, coaxially and annularly sleeved outside the inner electrode (31), an annular three-dimensional space in the middle, namely a plasma space (314), electrode cooling gas entering the electrode cooling gas input channel (311), the electrode cooling gas which passes through the inner electrode cooling channel (313), the inner electrode (31) is integrally cooled and then is introduced into the plasma space (314) to be mixed with the gas,

the shell (33) is in a shape of 'T', is made of insulating materials, is coaxially adhered to the cylindrical peripheral surface of the outer electrode (32), a working medium gas input channel (331) is arranged on the outer side surface of the shell (33), the working medium gas is introduced into the plasma space (314) after penetrating the shell (33) and the outer electrode (32) layer by layer,

the output plasma regulating joint (4) comprises an inner cover (41) and an outer cover (42) which are both made of heat-insulating materials, wherein

An inner cover (41) with a reversed U-shaped longitudinal section, the lower end of which is externally connected with the annular outer side surface of the inner electrode (31), the outer side surface of the upper end of which is connected by screw threads,

the longitudinal section of the outer cover (42) is in an inverted U shape, the side surface of the outer cover is provided with a plasma outlet (421) and is connected to an output plasma pipeline provided with an output plasma digital thermometer (63) and an output plasma flowmeter (83), the outer side surface of the outer cover (42) is internally connected to the annular inner side surface of the outer electrode (32) at the outlet of the plasma space (314) and is connected by threads, the outer cover (42) is rotated to adjust the steering angle of the plasma outlet (421) and adjust the outlet height of the plasma at the same time, the adjusting height of the outer cover (42) must keep the smoothness of the plasma outlet (421) and is limited by the length of the threads,

the plasma gas temperature regulator (5) is formed by connecting a heating power supply (51) and a resistance wire heating coil (52) in series, the resistance wire heating coil (52) is coaxially sleeved on a working medium gas input pipeline, the temperature rise range is (0 ℃,50 ℃), the plasma gas temperature regulator (5) automatically or manually regulates the coil current according to a control signal of a computer, and then regulates the plasma gas temperature by controlling the intermediate variable of the working medium gas temperature,

the starting point of the working medium gas input pipeline is at the working medium gas output end of the gas source (2), the end point of the working medium gas input pipeline is at the input port of the working medium gas input channel (331) arranged on the side surface of the shell (33), and the working medium gas input pipeline is sequentially provided with the following components in the working medium gas input direction: a working medium gas switch electromagnetic valve (71), a plasma gas temperature regulator (5), a working medium gas flow regulating electromagnetic valve (72), a working medium gas flowmeter (81), a working medium gas digital thermometer (61),

the starting point of the electrode cooling gas input pipeline is at the electrode cooling gas output end of the gas source (2), the end point of the electrode cooling gas input pipeline is at the inlet end of an electrode cooling gas input channel (311) on the bottom surface of the shell (33), and the electrode cooling gas input pipeline is sequentially provided with the following components along the electrode cooling gas input direction: an electrode cooling gas switching solenoid valve (73), an electrode cooling gas flow rate adjusting solenoid valve (74), an electrode cooling gas flow meter (82), an electrode cooling gas digital thermometer (62),

the processor (6) outputs the atmospheric pressure plasma according to the following steps in sequence:

step (6.1), initialization:

setting: when the control is divided into two steps, the expected value of the temperature of the plasma gas is as follows: [ -200 ℃,0 ℃ (0 ℃,50 ℃), tolerance, priority level,

output plasma flow desired value, allowable error, priority level,

the initial position of the thread when the outer cover (42) descends,

step (6.2), judging the priority level of the temperature and flow rate of the output plasma gas as the control object:

if: and the gas temperature control is prioritized, step (6.3) is executed,

if: and the flow control is prior, step (6.4) is executed,

and (6.3) preferably controlling the temperature of the plasma gas, namely the temperature for short, within an allowable error range, and meanwhile correcting the flow of the plasma gas, namely the flow:

step (6.3.1), if the desired temperature is in the range of [ -200 ℃,0 ℃ ]:

step (6.3.1.1), opening an electrode cooling gas switch electromagnetic valve, cooling gas switch valve (73) for short, an electrode cooling gas flow regulating electromagnetic valve, cooling gas regulating valve (74) for short, cooling the inner electrode (31) from room temperature to a desired temperature value, wherein the electrode cooling gas is the cooling gas which is input into the plasma space (314) and used for cooling the inner electrode,

step (6.3.1.2), manually turning on the power supply (1), sequentially turning on a working medium gas switch solenoid valve (71 for short) and a working medium gas flow regulating solenoid valve (72 for short), inputting the working medium gas flow regulating solenoid valves into the plasma space (314), greatly increasing the flow of the working medium gas to make the flow of the output plasma reach a desired flow value,

step (6.3.1.3), measuring the temperature of the output plasma gas, judging whether the temperature is in the allowable range of the expected gas temperature, if so, ending the program, if the temperature of the plasma gas exceeds the upper limit of the expected gas temperature, reducing the input flow of the working medium gas until the allowable error requirement of the temperature of the output plasma expected gas is met,

a step (6.3.1.4) of taking the actually measured plasma flow at this time as the corrected expected value,

step (6.3.2), the expected temperature value is within (0 ℃,50 ℃),

a step (6.3.2.1) of determining whether the desired temperature value is greater than room temperature,

if the expected temperature value is larger than the room temperature, the plasma gas temperature regulator (5) is opened, the temperature of the working medium gas input into the plasma space (314) is raised to the expected temperature value, so that the temperature of the output plasma gas reaches the allowable range of the expected temperature,

after the step (6.3.2.2) of using the measured output plasma flow rate as the corrected flow rate, the routine is terminated,

if the desired temperature value is less than room temperature, the input electrode cooling gas is introduced into the inner electrode (31) to reduce the output plasma to the desired gas temperature range,

a step (6.3.2.3) of using the measured output plasma flow as a corrected flow value, the routine is terminated,

and (6.4) if the flow control is prior, executing the following steps:

judging the corresponding expected value temperature gear:

step (6.4.1), if the desired temperature value is in the range of [ -200 ℃,0 ℃ ], performing the following steps:

step (6.4.1.1), inputting electrode cooling gas to cool the inner electrode (31) from room temperature to a desired temperature value,

step (6.4.1.2), increasing the flow of the working medium gas input into the plasma space (314) to make the flow of the output plasma reach the desired value,

and (6.4.1.3) taking the actually measured plasma gas temperature as the corrected expected temperature value, terminating the program,

step (6.4.2), if the expected temperature value is in the range of (0 ℃,50 ℃), executing the following steps:

it is determined whether the desired temperature is greater than room temperature,

if the desired temperature value is equal to room temperature, setting the plasma flow rate within an allowable range,

if the expected temperature value is larger than the room temperature, the following steps are executed

Step (6.4.2.1), increasing the input flow of the working medium gas to make the output plasma flow reach the expected value, and taking the actual output plasma gas temperature as the corrected expected value temperature;

if the expected temperature value is less than the room temperature, the following steps are executed

Step (6.4.2.2), the input flow of electrode cooling gas is increased to reduce the temperature of the inner electrode (31) to the lower limit of the expected temperature,

and (6.4.2.3) inputting working medium gas to enable the output plasma flow to reach an expected value, taking the actually measured output plasma gas temperature as a corrected expected temperature value, and ending the program.

2. The low temperature range, bare electrode atmospheric pressure plasma generator system of claim 1 wherein the three digital thermometers are three temperature taps of a multi-channel thermometer measuring the range of [ -200 ℃,200 ℃ ], the temperature signal output of which is connected to a corresponding input of the processor.

Technical Field

A naked electrode type atmospheric pressure plasma generator in a low temperature range belongs to the technical field of atmospheric pressure radio frequency plasma.

Background

The atmospheric pressure low temperature plasma jet generator is a new atmospheric pressure low temperature plasma discharge technology which is started in recent years, utilizes the action of air flow and electric field to make the plasma produced in the discharge area be jetted out from the jet pipe or orifice, and make directional flow towards the working area in the external gas environment without solid boundary constraint to form plasma jet, so that it can be extensively used in the fields of biomedicine, material surface treatment, food fresh-keeping, disinfection and sterilization, waste water treatment, etc. The low-temperature plasma jet sources commonly used at present mainly comprise two types, namely a dielectric barrier discharge type generator driven by a kilohertz power supply and an exposed electrode type generator driven by a radio frequency power supply. The exposed electrode type generator adopts metal electrodes, the working medium gas is driven by an external power supply to discharge to generate plasma, the dielectric barrier discharge generator needs to place insulating materials such as ceramics, quartz and the like on the surface of one or two metal electrodes, and the working medium gas can also be driven by the external power supply to discharge to generate plasma. Compared with the prior art, the bare electrode type generator has simple structure, needs a cooling system to cool the electrode, and is easy to generate uniform glow discharge plasma; while the breakdown voltage of the dielectric barrier discharge generator and the voltage required for maintaining the discharge are both high, but since it can conveniently generate plasma jet with gas temperature in the room temperature range, for example, 20-40 ℃, it is more widely used in the research of promoting wound healing, stomatology, etc. [ IEEE trans. plasma sci.2019, 474848-4860; sci. rep.2015, 513849; australas.phys.eng.sci.med.2018, 41905-917 ].

With the rapid development of atmospheric pressure low temperature plasma in the biomedical field in recent years, the demand for designing a plasma generator capable of generating plasma with adjustable gas temperature and wide temperature coverage (covering the range from subzero temperature to room temperature) is gradually emerging, so as to be suitable for processing diversified temperature-sensitive biological materials in practical application. In the existing research of atmospheric pressure low temperature plasma generating sources based on biological application, the average gas temperature change of generated plasma tends to concentrate on the room temperature range or higher, for example, the average gas temperature range of atmospheric pressure cold plasma for disinfection and sterilization is 20-28 ℃ [ J.Phys.D.Appl.Phys.2012, 45165205 ], the average gas temperature of plasma jet for mutation breeding is below 40 ℃ [ J.Appl.Microbio.2009108851-858 ], so research on plasma sources capable of generating average gas temperature range from subzero temperature to room temperature is needed. In addition to the requirements on gas temperature, the atmospheric pressure cold plasma generation system applied to the biological field also needs to have the following characteristics: working in an open environment, facilitating contact with biological materials and control of processing conditions; the generation system is easy to build and simple to operate; the generated plasma jet has a large enough sectional area to act on biological materials, generally the magnitude of millimeter and above; the plasma jet is soft and uniform and has no filiform discharge.

Disclosure of Invention

The invention aims to provide a generator system with controllable plasma gas temperature and flow, in particular to a bare electrode type plasma generator system in a low-temperature range of [ -200 ℃,50 ℃).

1. The invention is characterized in that the temperature of the output plasma gas is within-200 ℃ and 50 ℃, and the plasma gas comprises a power supply 1, a gas source 2, a plasma generator 3, an output plasma regulating joint 4, a joint for short, a plasma gas temperature regulator 5 and a processor 6, wherein the plasma gas temperature regulator

The power supply 1 is a radio frequency power supply with the frequency of 13.56MHz and the maximum output power of 1kW,

the gas source 2 is a helium tank filled with helium gas with the temperature of-268.8 ℃, and is provided with a working medium gas output end and an electrode cooling gas output end,

the plasma generator 3, which is a coaxial type bare electrode generator, includes an inner electrode 31, an outer electrode 32 and a housing 33, wherein

The inner electrode 31 is cylindrical, the longitudinal section of the inner electrode is U-shaped, the inner electrode comprises an electrode cooling gas input channel 311, a power supply connector 312, an inner electrode cooling channel 313 and a plasma space 314, wherein the electrode cooling gas input channel 311 and the power supply connector 312 respectively penetrate through the bottom of the U-shaped section along the left side and the right side in the longitudinal direction, the inner electrode cooling channel 313 penetrates through the cylindrical surface of the inner electrode 31 along the radial direction of the inner electrode 31 layer by layer from top to bottom along the side surface of the inner electrode 31, and the cross section of the inner electrode cooling channel 313 is annularly distributed,

the outer electrode 32 is a cylinder which is penetrated through from top to bottom, coaxially and annularly sleeved outside the inner electrode 31, the middle annular three-dimensional space is a plasma space 314, electrode cooling gas entering the electrode cooling gas input channel 311 passes through the inner electrode cooling channel 313, the inner electrode 31 is integrally cooled and then is introduced into the plasma space 314 to be mixed with the gas,

the shell 33 is in a shape of 'T', is made of insulating materials, is coaxially adhered on the cylindrical peripheral surface of the outer electrode 32, is provided with a working medium gas input channel 331 on the outer side surface of the shell 33, penetrates the shell 33 and the outer electrode 32 layer by layer and then leads the working medium gas into the plasma space 314,

the output plasma regulating joint 4 comprises an inner cover 41 and an outer cover 42 which are made of heat-insulating materials, wherein

The inner cover 41 has an inverted U-shaped longitudinal section, the lower end is externally connected to the annular outer side surface of the inner electrode 31, the outer side surface of the upper end is connected by screw threads,

the outer cover 42 is connected with an output plasma pipeline provided with an output plasma digital thermometer 63 and an output plasma flowmeter 83, the outer side surface of the outer cover 42 is internally connected with the annular inner side surface of the outer electrode 32 at the outlet of the plasma space 314 and is connected by screw threads, the outer cover 42 is rotated to adjust the steering angle of the plasma outlet 421, simultaneously, the outlet height of the plasma is adjusted accordingly, the adjustment height of the outer cover 42 must keep the smoothness of the plasma outlet 421 and is limited by the screw thread length,

the plasma gas temperature regulator 5 is formed by connecting a heating power supply 51 and a resistance wire heating coil 52 in series, the resistance wire heating coil 52 is coaxially sleeved on a working medium gas input pipeline, the temperature rise range is (0, 50 ℃), the plasma gas temperature regulator 5 automatically or manually regulates the coil current according to a control signal of a computer, and then regulates the plasma gas temperature by controlling the intermediate variable of the working medium gas temperature,

the starting point of the working medium gas input pipeline is at the working medium gas output end of the gas source 2, the end point is at the input port of the working medium gas input channel 331 arranged at the side surface of the shell 33, and the working medium gas input pipeline is sequentially provided with: a working medium gas switch electromagnetic valve 71, a plasma gas temperature regulator 5, a working medium gas flow regulating electromagnetic valve 72, a working medium gas flowmeter 81, a working medium gas digital thermometer 61,

the starting point of the electrode cooling gas input pipe is at the electrode cooling gas output end of the gas source 2, the end point is at the inlet end of the electrode cooling gas input channel 311 on the bottom surface of the housing 33, and the electrode cooling gas input pipe is sequentially provided with: the electrode cooling gas switching solenoid valve 73, the electrode cooling gas flow rate adjusting solenoid valve 74, the electrode cooling gas flow meter 82, the electrode cooling gas digital thermometer 62,

the processor 6 outputs the atmospheric pressure plasma sequentially according to the following steps:

step (6.1), initialization:

setting: when the control is divided into two steps, the expected value of the temperature of the plasma gas is as follows: [ -200 ℃,0 ℃ (0 ℃,50 ℃), tolerance, priority level,

output plasma flow desired value, allowable error, priority level,

the initial position of the threads as the outer shroud 42 descends,

step (6.2), judging the priority level of the temperature and flow rate of the output plasma gas as the control object:

if: and the gas temperature control is prioritized, step (6.3) is executed,

if: and the flow control is prior, step (6.4) is executed,

and (6.3) preferably controlling the temperature of the plasma gas, namely the temperature for short, within an allowable error range, and meanwhile correcting the flow of the plasma gas, namely the flow:

step (6.3.1), if the desired temperature is in the range of [ -200 ℃,0 ℃ ]:

step (6.3.1.1), opening electrode cooling gas switch solenoid valve, cooling gas switch valve 73 for short, electrode cooling gas flow regulating solenoid valve, cooling gas regulating valve 74 for short, cooling inner electrode 31 from room temperature to desired temperature value, the electrode cooling gas is the cooling gas for cooling inner electrode inputted into plasma space 314,

step (6.3.1.2), manually turning on the power supply 1, sequentially turning on the working medium gas switch solenoid valve, for short, the working medium gas switch valve 71, and the working medium gas flow regulating solenoid valve, for short, the working medium gas regulating valve 72, inputting into the plasma space 314, and greatly increasing the working medium gas flow to make the output plasma flow reach the desired flow value,

step (6.3.1.3), measuring the temperature of the output plasma gas, judging whether the temperature is in the allowable range of the expected gas temperature, if so, ending the program, if the temperature of the plasma gas exceeds the upper limit of the expected gas temperature, reducing the input flow of the working medium gas until the allowable error requirement of the temperature of the output plasma expected gas is met,

a step (6.3.1.4) of taking the actually measured plasma flow at this time as the corrected expected value,

step (6.3.2), the expected temperature value is within (0 ℃,50 ℃),

a step (6.3.2.1) of determining whether the desired temperature value is greater than room temperature,

if the expected temperature value is larger than the room temperature, the plasma gas temperature regulator 5 is opened, the temperature of the working medium gas input into the plasma space 314 is raised to the expected temperature value, so that the temperature of the output plasma gas reaches the allowable range of the expected temperature,

after the step (6.3.2.2) of using the measured output plasma flow rate as the corrected flow rate, the routine is terminated,

if the desired temperature value is less than room temperature, the input electrode cooling gas is introduced into the inner electrode 31 to reduce the output plasma to the desired gas temperature range,

a step (6.3.2.3) of using the measured output plasma flow as a corrected flow value, the routine is terminated,

and (6.4) if the flow control is prior, executing the following steps:

judging the corresponding expected value temperature gear:

step (6.4.1), if the desired temperature value is in the range of [ -200 ℃,0 ℃ ], performing the following steps:

step (6.4.1.1), inputting electrode cooling gas to cool the inner electrode 31 from room temperature to a desired temperature value,

step (6.4.1.2), increasing the flow of the working medium gas input into the plasma space 314, so that the flow of the output plasma reaches the desired value,

and (6.4.1.3) taking the actually measured plasma gas temperature as the corrected expected temperature value, terminating the program,

step (6.4.2), if the expected temperature value is in the range of (0 ℃,50 ℃), executing the following steps:

it is determined whether the desired temperature is greater than room temperature,

if the desired temperature value is equal to room temperature, setting the plasma flow rate within an allowable range,

if the expected temperature value is larger than the room temperature, the following steps are executed

Step (6.4.2.1), increasing the input flow of the working medium gas to make the output plasma flow reach the expected value, and taking the actual output plasma gas temperature as the corrected expected value temperature;

if the expected temperature value is less than the room temperature, the following steps are executed

Step (6.4.2.2), the input flow of electrode cooling gas is increased to reduce the temperature of the inner electrode (31) to the lower limit of the expected temperature,

and (6.4.2.3) inputting working medium gas to enable the output plasma flow to reach an expected value, taking the actually measured output plasma gas temperature as a corrected expected temperature value, and ending the program.

The invention has the advantages of strong controllable selectivity of the controlled object, large controllable range of the output plasma under low temperature, flexible flow control selectivity, simple structure of the generator and high utilization rate of electrode cooling gas.

Drawings

The figures used in the description so far are as follows,

a power supply 1, a gas source 2, a plasma generator 3, including

An inner electrode 31, an outer electrode 32, a shell 33, an electrode cooling gas input passage 311, a power supply connector 312, an inner electrode cooling passage 313, a plasma space 314, a working medium gas input passage 331,

the output plasma regulating joint 4 comprises an inner cover 41, an outer cover 42, a plasma outlet 421,

the plasma gas temperature regulator 5 comprises a heating power supply 51 and a resistance wire heating coil 52,

the processor 6 comprises a working medium gas digital thermometer 61, an electrode cooling gas digital thermometer 62, an output plasma digital thermometer 63,

working medium gas switching solenoid valve 71, working medium gas flow regulating solenoid valve 72, electrode cooling gas switching solenoid valve 73, electrode cooling gas flow regulating solenoid valve 74, working medium gas flowmeter 81, electrode cooling gas flowmeter 82, and output plasma flowmeter 83.

FIG. 1 is a schematic diagram of a plasma generator.

Fig. 2 shows a block diagram of a generator system.

FIG. 3 is a processor control flow diagram.

The specific implementation mode is as follows:

the plasma generator of the invention is provided with an electrode cooling gas channel, so that the input electrode cooling gas gradually enters the plasma space through the electrode cooling gas input channel (311) arranged in the inner electrode 31 and a plurality of radial electrode cooling gas channels excavated layer by layer along the height direction of the inner electrode 31, thereby cooling the inner electrode 31, improving the use efficiency of the electrode cooling gas and protecting the environment.

The invention forms the outer cavity of the plasma generator by the shell 33 which is made of the heat-insulating material which is bonded on the peripheral surface of the outer electrode 32 and holds the outer electrode 32 in a supporting manner, thereby simplifying the structure, reducing the volume of the plasma generator and saving the material.

The output plasma adjusting joint 4 which can not only hold the plasma at the outlet but also adjust the height and the output angle of the output plasma is additionally arranged between the plasma outlet 421 end and the plasma output channel, so that the invention has higher practicability.

The invention starts from service requirements, and adopts control ideas of priority control, grading control, moderate control and energy-saving control, wherein:

the service requirement is that from practical point of view, two parameters of plasma gas temperature and flow are taken as control objects, and from a desired value, an operation error range and a temperature interval of output plasma [ -200 ℃,50 ℃), the longitudinal position of the output plasma is adjusted, and the adjustment of an output angle is taken as a specific control target.

The priority control is that the priority level between two control objects is determined from the demand of the service target of the control object, the gas temperature is taken as the priority control object in general, and the flow rate is taken as the priority control object in special demand, and the specific control strategy is as follows: in any case, it is necessary to start the principle of adjusting the gas temperature/flow rate in advance according to the gas temperature/flow rate priority in a set temperature environment.

The step control means that the temperature range is divided into two steps of [ -200 ℃,0 ℃ and (0 ℃,50 ℃) and is subjected to step processing so as to reduce the adjustment range of the adjustment object as much as possible, for example, the desired temperature is between 0 ℃ and room temperature, and the desired temperature is increased from the desired value to the room temperature, which saves time and energy compared with the heating of the electrode cooling gas to the room temperature.

The appropriate control means that, when the priority control target first reaches the allowable error range, the actual measured sub-optimal target value is used as the corrected expected value, and no fine adjustment or large adjustment is performed for the sub-optimal target value.

Energy-saving control and step control can save energy, electrode cooling gas is input into a plasma space to supplement working medium gas after cooling an inner electrode 31, and one gas source 2 is adopted to output the working medium gas and the electrode cooling gas respectively, so that the aim of saving energy can be achieved compared with the case that two different gas sources are adopted respectively.

Therefore, the invention has the advantages of large low-temperature range of output plasma, strong practicability, simple electrode structure and easy popularization.