# US 2009/0260972 A1 · Plasma Generator and Method of Generating Plasma Using the Same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2009/0260972 A1 - Document ID: US20090260972A1 - Status: Published application - Kind: A1 - Application number: 12/224,750 - Filed: 2007-02-17 - Published: 2009-10-22 - Earliest claimed: 2006-03-07 - Assignees: University of the Ryukyus - Inventors: Akira Yonesu - Web page: https://patentgrep.com/patent/US20090260972A1 ## CPC - H01J 37/32192: {Microwave generated discharge (H01J37/32357, H01J37/32366, H01J37/32394, H01J37/32403 take precedence)} - H05H 1/46: using applied electromagnetic fields, e.g. high frequency or microwave energy (H05H1/26 takes precedence) - H05H 1/463: {using antennas or applicators} - H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H) - H05H: PLASMA TECHNIQUE (apparatus or processes specially adapted for producing X-rays H05G2/00); PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS ## Abstract A plasma generator in which the variation of the impedance in the cavity before and after plasma is ignited is less and hardly affected by the shape of the cavity, and the ignitability of the plasma is improved and a method of generating plasma using the plasma generator are provided. The plasma generator comprises a nonconductive gas flow pipe (1) for introducing a gas (9) for generating plasma and discharging it into the atmosphere and a conductive antenna pipe (2) surrounding the gas flow pipe. A microwave (7) is applied to the antenna pipe to change the gas in the gas flow pipe into plasma. The plasma generator is characterized in that a slit (3) with a predetermined length is formed in the antenna pipe (2) along the axial direction of the gas flow pipe. Preferably, the plasma generator is characterized in that the length of the slit is an integral multiple of the half-wave length of the applied microwave. ## Claims ### Claim 1 A plasma generator, comprising a non-conductive gas flow pipe through which a gas for generating plasma is introduced and discharged in the air, and a conductive antenna pipe which surrounds the gas flow pipe, the plasma generator irradiating the antenna pipe with microwaves so that the gas in the gas flow pipe is converted to plasma, characterized in that a slit of a predetermined length is created in the antenna pipe in the direction of the axis of the gas flow pipe. ### Claim 2 (depends on 1) The plasma generator according to claim 1, characterized in that the slit has an opening on the side on which gas is discharged from the gas flow pipe. ### Claim 3 (depends on 1) The plasma generator according to claim 1, characterized in that the slit is created inside the antenna pipe. ### Claim 4 (depends on 1) The plasma generator according to claim 1, characterized in that the slit has a portion which protrudes into the slit. ### Claim 5 (depends on 1) The plasma generator according to claim 1, characterized in that the antenna pipe is bent toward the gas flow pipe at an end on the side where a gas is discharged from the gas flow pipe. ### Claim 6 (depends on 1) The plasma generator according to claim 1, characterized in that the length of the slit is set to a multiple of the half wavelength of microwaves for irradiation in integers. ### Claim 7 (depends on 1) The plasma generator according to claim 1, characterized in that at least two slits are provided around the gas flow pipe. ### Claim 8 (depends on 1) The plasma generator according to claim 1, characterized in that a number of gas flow pipes are provided, and each gas flow pipe has an antenna pipe. ### Claim 9 (depends on 1) The plasma generator according to claim 1, characterized in that the antenna pipe is provided within a waveguide through which microwaves propagate so as to penetrate through the waveguide. ### Claim 10 (depends on 1) A method for generating plasma using the plasma generator according to claim 1, characterized by comprising: a plasma igniting step of keeping the air pressure within the gas flow pipe lower than ambient pressure and igniting plasma through irradiation with microwaves; and an ambient pressure step of making the air pressure within the gas flow pipe the same as ambient pressure after the plasma igniting step. ### Claim 11 (depends on 1) A method for generating plasma using the plasma generator according to claim 1, characterized by comprising a plasma igniting step of supplying a first gas into the gas flow pipe and igniting plasma through irradiation with microwaves; and the step of supplying a second gas which is more difficult to convert to plasma than the first gas together with the first gas after the step of igniting plasma and converting the second gas to plasma. ### Claim 12 (depends on 1) The method for generating plasma according to claim 1, characterized by comprising a movement step of moving the gas flow pipe and the antenna pipe relative to each other after the ignition of plasma under ambient pressure so that an end portion of the gas flow pipe on the side where a gas is discharged is closer to an end portion of the antenna pipe on the slit side. ### Claim 13 (depends on 1) The method for generating plasma according to claim 1, characterized in that microwaves with which the antenna pipe is irradiated are pulse driven and the idle period of the pulse drive is within an average period during which plasma remains within the gas flow pipe.