Non-invasive VHF monitoring of low-temperature atmospheric pressure plasma
Data(s) |
01/05/2010
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Resumo |
A real-time VHF swept frequency (20–300 MHz) reflectometry measurement for radio-frequency capacitive-coupled atmospheric pressure plasmas is described. The measurement is scalar, non-invasive and deployed on the main power line of the plasma chamber. The purpose of this VHF signal injection is to remotely interrogate in real-time the frequency reflection properties of plasma. The information obtained is used for remote monitoring of high-value atmospheric plasma processing. Measurements are performed under varying gas feed (helium mixed with 0–2% oxygen) and power conditions (0–40 W) on two contrasting reactors. The first is a classical parallel-plate chamber driven at 16 MHz with well-defined electrical grounding but limited optical access and the second is a cross-field plasma jet driven at 13.56 MHz with open optical access but with poor electrical shielding of the driven electrode. The electrical measurements are modelled using a lumped element electrical circuit to provide an estimate of power dissipated in the plasma as a function of gas and applied power. The performances of both reactors are evaluated against each other. The scalar measurements reveal that 0.1% oxygen admixture in helium plasma can be detected. The equivalent electrical model indicates that the current density between the parallel-plate reactor is of the order of 8–20 mA cm-2 . This value is in accord with 0.03 A cm-2 values reported by Park et al (2001 J. Appl. Phys. 89 20–8). The current density of the cross-field plasma jet electrodes is found to be 20 times higher. When the cross-field plasma jet unshielded electrode area is factored into the current density estimation, the resultant current density agrees with the parallel-plate reactor. This indicates that the unshielded reactor radiates electromagnetic energy into free space and so acts as a plasma antenna. |
Identificador |
http://dx.doi.org/10.1088/0963-0252/19/3/034008 http://www.scopus.com/inward/record.url?scp=77952990222&partnerID=8YFLogxK |
Idioma(s) |
eng |
Direitos |
info:eu-repo/semantics/restrictedAccess |
Fonte |
Law , V J , Daniels , S , Walsh , J L , Kong , M G , Graham , L M & Gans , T G 2010 , ' Non-invasive VHF monitoring of low-temperature atmospheric pressure plasma ' Plasma Sources Science and Technology , vol 19 (3) , no. 3 , 034008 , pp. 034008-034008-8 . DOI: 10.1088/0963-0252/19/3/034008 |
Palavras-Chave | #/dk/atira/pure/subjectarea/asjc/3100/3104 #Condensed Matter Physics |
Tipo |
article |