PLASMA IRRADIATION APPARATUS AND PLASMA IRRADIATION METHOD

1 . A plasma irradiation apparatus comprising:

a gas guide channel defining therein a flow path for flow of a discharge gas, with an outlet port formed at an end of the flow path;

a discharge section having a first electrode, a second electrode and a dielectric layer interposed between the first electrode and the second electrode and being operable to generate plasma discharge in the gas guide channel;

a gas supply channel defining therein a path for supply of the discharge gas to the gas guide channel, the gas supply channel being disposed at a location closer to the gas guide channel than a gas control section which executes flow rate control of the discharge gas, and

a check valve arranged in the gas guide channel or the gas supply channel to allow the discharge gas to flow in a first direction toward the outlet port and prevent the discharge gas from flowing in a second direction reverse to the first direction, wherein

the plasma irradiation apparatus is adapted for mounting on a distal device which is movable relative to a target substance.

2 . A plasma irradiation apparatus comprising:

a gas guide channel defining therein a flow path for flow of a discharge gas, with an outlet port formed at an end of the flow path;

a discharge section having a first electrode, a second electrode and a dielectric layer interposed between the first electrode and the second electrode and being operable to generate plasma discharge in the gas guide channel; and

a gas supply channel defining therein a path for supply of the discharge gas to the gas guide channel,

a valve arranged in the gas guide channel or the gas supply channel to control a flow rate of the discharge gas according to an opening degree of the valve;

a discharge control section that controls the discharge section to perform the plasma discharge; and

a valve control section that controls opening and closing of the valve, wherein

the plasma irradiation apparatus is adapted for mounting on a distal device which is movable relative to a target substance, and

the valve control section is configured to:

keep the valve opened during at least a discharge period in which the discharge control section allows the discharge section to perform the plasma discharge; and

open the valve during a predetermined preparation period, in which the discharge control section prohibits the discharge section from performing the plasma discharge, before the discharge period.

3 . The plasma irradiation apparatus according to claim 2 ,

wherein the valve control section is configured to open the valve at a larger opening degree during at least a partial period in the preparation period than that during the discharge period.

4 . The plasma irradiation apparatus according to claim 2 ,

wherein the valve control section is configured to continuously or intermittently open the valve at a smaller opening degree during a rest period from an end of the discharge period to a start of a next discharge period than that during the discharge period.

5 . The plasma irradiation apparatus according to claim 2 , further comprising a concentration detection section that detects a concentration of the discharge gas or specific gas in air in a pathway portion of the gas guide channel or the gas supply channel located closer to the outlet port than the valve.

6 . The plasma irradiation apparatus according to claim 5 ,

wherein the concentration detection section detects the concentration of the discharge gas in the pathway portion, and

wherein the discharge control section is configured to:

allow the discharge section to perform the plasma discharge when the concentration of the discharge gas detected by the concentration detection section is higher than or equal to a threshold value; and

when the concentration of the discharge gas detected by the concentration detection section is lower than the threshold value, prohibit the discharge section from performing the plasma discharge.

7 . The plasma irradiation apparatus according to claim 5 ,

wherein the concentration detection section detects the concentration of the specific gas; and

wherein the discharge control section is configured to increase a maximum voltage between the first and second electrodes with increase in the concentration of the specific gas detected by the concentration detection section.

8 . A plasma irradiation method using a plasma irradiation apparatus, the plasma irradiation apparatus comprising: a gas guide channel defining therein a flow path for flow of a discharge gas, with an outlet port formed at an end of the flow path; a discharge section having a first electrode, a second electrode and a dielectric layer interposed between the first electrode and the second electrode and being operable to generate plasma discharge in the gas guide channel; and a gas supply channel defining therein a path for supply of the discharge gas to the gas guide channel, the plasma irradiation method comprising the steps of:

mounting the plasma irradiation apparatus to a distal device which is movable relative to a target substance;

arranging a valve in the gas guide channel or the gas supply channel;

operating a discharge control section to control the plasma discharge of the discharge section; and

operating a valve control section to: keep the valve opened during at least a discharge period in which the discharge control section allows the discharge section to perform the plasma discharge; and open the valve during a predetermined preparation period, in which the discharge control section prohibits the discharge section from performing the plasma discharge, before the discharge period.

9 . The plasma irradiation apparatus according to claim 8 ,

wherein the valve control section is operated to open the valve at a larger opening degree during at least a partial period in the preparation period than that during the discharge period.

10 . The plasma irradiation apparatus according to claim 8 ,

wherein the valve control section is operated to continuously or intermittently open the valve at a smaller opening degree during a rest period from an end of the discharge period to a start of a next discharge period than that during the discharge period.

11 . The plasma irradiation apparatus according to claim 8 ,

wherein the plasma irradiation apparatus comprises a concentration detection section that detects a concentration of the discharge gas in a pathway portion of the gas guide channel or the gas supply channel located closer to the outlet port than the valve, and

wherein the discharge control section is operated to: allow the discharge section to perform the plasma discharge when the concentration of the discharge gas detected by the concentration detection section is higher than or equal to a threshold value; and prohibit the discharge section from performing the plasma discharge when the concentration of the discharge gas detected by the concentration detection section is lower than the threshold value.

12 . The plasma irradiation apparatus according to claim 8 ,

wherein the plasma irradiation apparatus comprises a concentration detection section that detects a concentration of specific gas in air in a pathway portion of the gas guide channel or the gas supply channel located closer to the outlet port than the valve, and

wherein the discharge control section is operated to increase a maximum voltage between the first and second electrodes with increase in the concentration of the specific gas detected by the concentration detection section.