Compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source

Abstract

A compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source includes an outer coaxial line, and an inner coaxial line arranged inside the outer coaxial line. The outer coaxial line includes a tube body. A metal tube is arranged in the tube body. A short-circuit plunger is arranged at the bottom of the metal tube. The inner coaxial line includes a needle electrode, and the needle electrode is arranged in the metal tube. A first gas inlet is arranged on the tube body, and the first gas inlet is connected between the tube body and the metal tube. A second gas inlet is arranged at the bottom of the metal tube, and the second gas inlet is connected between the metal tube and the needle electrode. The tube body is further provided with a microwave input port, and the microwave input port is connected to the metal tube.

Claims

1. A compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source, comprising an outer coaxial line and an inner coaxial line; wherein the inner coaxial line is arranged inside the outer coaxial line, and a top of the inner coaxial line is flush with a top of the outer coaxial line; the outer coaxial line comprises a tube body; a metal tube is arranged in the tube body; a short-circuit plunger is movably arranged at a bottom of the metal tube; the inner coaxial line comprises a needle electrode; the needle electrode is arranged in the metal tube, and a top of the needle electrode protrudes out of the metal tube; a first gas inlet is arranged on the tube body, and the first gas inlet is connected between the tube body and the metal tube; a second gas inlet is arranged at the bottom of the metal tube, and the second gas inlet is connected between the metal tube and the needle electrode; the tube body is provided with a microwave input port, and the microwave input port is connected to the metal tube.

2. The compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source of claim 1, wherein, the needle electrode comprises an upper metal cylinder and a lower metal cylinder; the lower metal cylinder is in electrical contact with the metal tube, and a surface of the lower metal cylinder is provided with a groove, wherein an air flow passes through the groove.

3. The compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source of claim 2, wherein, a length of the upper metal cylinder is an integral multiple of ¼ of a wavelength at an operating frequency of the compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source.

4. The compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source of claim 2, wherein, three V-shaped notches are uniformly provided on the surface of the lower metal cylinder.

5. The compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source of claim 1, wherein, the top of the outer coaxial line is open.

6. The compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source of claim 1, wherein, the needle electrode is 2 mm higher than the metal tube.

7. The compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source of claim 1, wherein, each of the outer coaxial line and the inner coaxial line constitutes a coaxial transmission line with a characteristic impedance of 10-100 ohms.

8. The compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source of claim 1, wherein, at least one gas selected from the group consisting of nitrogen, argon, oxygen, helium, hydrogen, carbon dioxide and methane is introduced into the first gas inlet and the second gas inlet of the compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source.

9. The compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source of claim 1, wherein, the tube body is made of brass.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of the present invention;

(2) FIG. 2 is a right view of the present invention;

(3) FIG. 3 is a schematic diagram of the present invention lying flatly; and

(4) FIG. 4 is a schematic diagram of the metal tube.

(5) In the figures: 1, tube body; 2, microwave input port; 3, short-circuit plunger; 4, plasma jet; 5, needle electrode; 6, first gas inlet; 7, metal tube; 8, second gas inlet.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(6) The specific embodiment of the present invention is described in detail hereinafter with reference to the drawings.

(7) In an embodiment of the present invention, as shown in FIGS. 1-4, a compound double coaxial line atmospheric pressure low-temperature microwave plasma jet source includes an outer coaxial line and an inner coaxial line. The inner coaxial line is arranged inside the outer coaxial line. The top of the inner coaxial line is flush with the top of the outer coaxial line. The outer coaxial line includes the tube body 1. The tube body 1 is made of brass and has an inner diameter of 10 mm. The metal tube 7 is arranged in the tube body 1. The metal tube 7 has an outer diameter of 3.5 mm and an inner diameter of 2.5 mm. The short-circuit plunger 3 is movably arranged at the bottom of the metal tube 7. The inner coaxial line includes the needle electrode 5. The needle electrode 5 is arranged in the metal tube 7, and the top of the needle electrode 5 protrudes out of the metal tube 7 for 2 mm. The top of the outer coaxial line is open. The first gas inlet 6 is arranged on the tube body 1. The first gas inlet 6 is connected between the tube body 1 and the metal tube 7. The second gas inlet 8 is arranged at the bottom of the metal tube 7. The second gas inlet 8 is connected between the metal tube 7 and the needle electrode 5. The tube body 1 is further provided with the microwave input port 2. The microwave input port 2 is provided with a bayonet nut connector (BNC) input terminal, and the inner core of the microwave input terminal is connected to the metal tube 7 to feed microwave.

(8) The needle electrode 5 includes an upper metal cylinder and a lower metal cylinder. The upper metal cylinder is a solid copper cylinder with a diameter of 1 mm and a length of 30.6 mm which is ¼ of a wavelength of the 2.45 GHz microwave. The lower metal cylinder is a solid copper cylinder with a diameter of 2.5 mm and a length of 20 mm. The lower metal cylinder is in electrical contact with the metal tube 7. Three V-shaped notches are uniformly provided on the surface of the lower metal cylinder. Each of the outer coaxial line and the inner coaxial line constitutes a coaxial transmission line with a characteristic impedance of 10-100 ohms.

(9) The present invention adopts the structure of a compound double coaxial line. One air flow passes between the inner conductor and the outer conductor of the outer coaxial line, and another air flow passes between the inner conductor and the outer conductor of the inner coaxial line. The microwave is fed into the microwave input port 2 and is then coupled into the smaller inner coaxial line at the open port of the outer coaxial line. After the microwave is reflected in the inner coaxial line, a strong electric field is generated at the top of the inner conductor of the inner coaxial line and finally excites the plasma discharge. The plasma is restricted by the two air flows to finally form the atmospheric pressure microwave plasma jet 4 with stable and controllable shape, discharge state and temperature.

(10) The specific embodiment of the present invention is described in detail with reference to the drawings, but cannot be construed as a limitation to the scope of protection of the present invention. Within the scope described in the claims, all modifications and variations made by those skilled in the art without creative efforts shall fall within the scope of protection of the present invention.