Atmospheric-pressure He plasma jet: effect of dielectric tube diameter
Date
2016-09-12
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Abstract
Atmosfäärirõhul töötav plasmajuga tekitatakse dielektriktorust väljuvas inertgaasi joas, rakendades plasma süütamiseks elektroodidele vahelduvpinge. Helisagedusliku vahelduvpinge kasutamisel koosneb plasmajuga ionisatsioonilainetest, mis levivad kiirusega kuni 103 km/s ja mille kestus on lühem kui 1 µs. Plasmajoal põhinevate seadmete intensiivsete uuringute peamiseks motivaatoriks on nende seadmete võimalikud rakendused biomeditsiinis lähtuvalt sellise plasma madalast temperatuurist ning kõrgest keemilisest aktiivsusest. Biomeditsiinis on plasmajuga rakendatud steriliseerimiseks, haavade raviks ning vähiraviks.
Meditsiinilised rakendused nõuavad plasma parameetrite, nagu näiteks elektronide tihedus, elektronide temperatuur ja gaasi temperatuur, täpset kontrolli. On teada, et ionisatsioonilainete kiirust ja olulisemaid plasma karakteristikuid on võimalik kontrollida katseparameetritega, milleks on rakendatav pinge, gaasivoo kiirus ja ka elektroodide konfiguratsioon. Täiendava võimaluse plasma parameetrite kontrollimiseks annab dielektriktoru diameetri muutmine, kuid seniajani puudusid sellel teemal süstemaatilised uuringud.
Käesolevas doktoritöös uuritigi dielektriktoru diameetri mõju helisagedustel töötava He plasmajoa parameetritele. Eksperimentides kasutati kvartstorusid, mille diameeter muutus vahemikus 80 kuni 500 µm ning alternatiivina ka ütriumiga stabiliseeritud ZrO2 mikrotorusid.
Uurimistöö käigus selgus, et mikrotoru diameetril vähendamisel on järgnev mõju:
• plasma süttimis ja kustumispinge kasvab
• elektronide tihedus ja heeliumi ergastustemperatuur kasvavad ning gaasi temperatuur väheneb
• ionisatsioonilainete kiirus kasvab
Kokkuvõtvalt näidati, et dielektrikutoru diameetri muutmine võimaldab kontrollida mitmeid olulisi plasma parameetreid ja kasutatud plasmaseadme konfiguratsiooni korral omab diameeter võrreldes teiste katseparameetritega määravat rolli.
Atmospheric pressure plasma jet working in noble gas flow is a promising plasma source that has been actively investigated during the past decade. A plasma jet ignited by high voltages in the kHz frequency range appears continuous to the eye but actually consists of discrete highly luminous travelling plasma fronts which have also been referred to as “plasma bullets” or “ionization waves” propagating with velocities up to 103 km/s. The motivation behind the intensive research of plasma jets is the “cold” nature of these devices which enables a vast variety of applications where the gas temperature has to remain close to room temperature. Most important applications for plasma jets are in the field of biomedicine. The application of plasma jets in medicine requires precise control over plasma parameters. It has been shown that the propagation velocity of the ionization wave and several plasma parameters are influenced by externally controllable parameters such as the voltage, gas type and the electrode configuration of the plasma jet device. The dielectric tube diameter might offer an alternative approach to control the key plasma parameters. However, the possible effect of the dielectric tube has received little attention. In the PhD thesis the effect of dielectric tube in a He APPJ in the kHz frequency range was studied. Quartz tubes with inner diameters between 80 to 500 µm were used in the experiments. As an alternative Yttria stabilized ZrO2 microtubes were also tested. It was determined that reducing the microtube diameter has the following effects: • Plasma ignition and sustaining voltage increases • Several plasma parameters are affected: electron density and He excitation temperature increase while gas temperature decreases • The ionization wave velocity increases As a conclusion, it was demonstrated that several key parameters can be altered by changing the dielectric tube diameter which can thus prove an alternative method for controlling the plasma parameters.
Atmospheric pressure plasma jet working in noble gas flow is a promising plasma source that has been actively investigated during the past decade. A plasma jet ignited by high voltages in the kHz frequency range appears continuous to the eye but actually consists of discrete highly luminous travelling plasma fronts which have also been referred to as “plasma bullets” or “ionization waves” propagating with velocities up to 103 km/s. The motivation behind the intensive research of plasma jets is the “cold” nature of these devices which enables a vast variety of applications where the gas temperature has to remain close to room temperature. Most important applications for plasma jets are in the field of biomedicine. The application of plasma jets in medicine requires precise control over plasma parameters. It has been shown that the propagation velocity of the ionization wave and several plasma parameters are influenced by externally controllable parameters such as the voltage, gas type and the electrode configuration of the plasma jet device. The dielectric tube diameter might offer an alternative approach to control the key plasma parameters. However, the possible effect of the dielectric tube has received little attention. In the PhD thesis the effect of dielectric tube in a He APPJ in the kHz frequency range was studied. Quartz tubes with inner diameters between 80 to 500 µm were used in the experiments. As an alternative Yttria stabilized ZrO2 microtubes were also tested. It was determined that reducing the microtube diameter has the following effects: • Plasma ignition and sustaining voltage increases • Several plasma parameters are affected: electron density and He excitation temperature increase while gas temperature decreases • The ionization wave velocity increases As a conclusion, it was demonstrated that several key parameters can be altered by changing the dielectric tube diameter which can thus prove an alternative method for controlling the plasma parameters.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
plasma tekitamine, creation of plasma