26 KB196 KB23 KB200020242011Mozetič, Miranletnik:45številka:5str. 457-462ISSN:1580-2949COBISSID:881322URN:URN:NBN:SI:doc-XW9KMEJLenInštitut za kovinske materiale in tehnologijeMateriali in tehnologijeDebyeva dolžinagostota plazmeLangmuirjeva sondatemperatura elektronovvodikova plazmaCharacterization of extremely weakly ionized hydrogen plasma with a double Langmuir probe| Karakterizacija šibko ionizirane vodikove plazme z dvojno Langmuirjevo sondo|Basic parameters of hydrogen plasma created in a large discharge chamber were determined using a double Langmuir probe. Plasma was created in a Pyrex cylinder with the diameter of 25 cm and the height of 80 cm by an antenna connected to a RF generator operating at the frequency of 27.12 MHz and the power of about 200 W. The antenna was a copper coil of 4 turns. The discharge chamber was pumped with an oil diffusion pump with the nominal pumping speed of 600 L/s backed by a two slage rotary pump with the pumping speed of 4.4 x 10sup{-3} msup3 ssup{-1}. The ultimate pressure of about 2 x 10sup{-3} Pa was obtained in the vacuum system after pumping for few hours. A dobule Langmuir probe was galvanic separated from the mains and placed into the centre of the discharge chamber. The probe was made from 2 tungsten rods with a diameter of 1.2 mm and separated for 2 cm. The length of un-insulated part of the rods was 17.5 mm. Plasma parameters were measured at different pressures between 0.4 and 7.2 Pa. The electron temperature reached the maximumof about kTsube = 3.5 eV at the pressure of 1 Pa. The plasma density was slowly decreasing with increasing pressure and was of the order of 10sup{15} msup{-3}, and the Debve length was rather constant at about 2 x 10sup{-4} m. The results were explaned by characteristics of an electrode less RF discharge in the E modeZ Langmuirjevo sondo smo določali parametre vodikove plazme, ustvarjene v velikem plazemskem reaktorju. Ta je bil narejen iz cilindrične cevi iz stekla pyrex premera 25 cm in višine 80 cm. Plazmo smo vzbujali z anteno, povezano z RF-generatorjem s frekvenco 27,12 MHz in močjo 200 W. Antena je bila narejena iz bakrene tuljave s 4 ovoji. Razelektritveno komoro smo črpali z difuzijsko črpalko z nazivno črpalno hitrostjo 600 L/s in povezano z dvostopenjsko rotacijsko predčrpalko s črpalno hitrostjo 4,4 x 10na{-3} mna3 sna{-1}. Po nekajurnem črpanju smo dosegli končni tlak 2 x 10na{-3} Pa. Dvojna Langmuirjeva sonda je bila galvansko ločena od omrežja in vstavljena v sredino razelektritvene komore. Sonda je bila narejena iz dveh volframovih palic premera 1,2 mm, ki sta bili med seboj oddaljeni 2 cm. Dolžina neizoliranega dela palic je bila 17,5 mm. Parametre plazme smo merili pri tlakih med 0,4 Pa in 7,2 Pa. Temperatura elektronov je dosegla maksimum okoli kTspodaje = 3,5 eV pri tlaku 1 Pa. Gostota plazme je počasi padala z naraščajočim tlakom in je bila reda 10na{15} mna{-3}. Debyeva dolžina je bila dokaj konstantna okoli 2 x 10na{-4} m. Rezultate smo razložili z značilnostmi brezelektrodne RF-razelektritve v E-načinuTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije