On the low electron density of an atmospheric pressure radio frequency plasma

A low temperature atmospheric pressure radio frequency plasma with planar electrodes structure is studied in terms of electron density for the use in biomedical applications. In the experiment, plasma can be ignited at power of 10 W and sustained in homogeneous α mode from 10W to 30W. Gas temperature is estimated based on determination of the rotational temperature of OH radicals. OH (A2Σ+→X2Π, 0-0) band from 306-312nm is detected and compared with simulated spectrum, giving the gas temperature as low as 375 ±25K under the input power of 30W, helium flow rate of 2 SLM. Line profile analysis is adopted to characterize the Stark broadening for Hβ line, further to obtain the electron density. Since we meet a situation of low electron densit y plasma, profiles with and without consideration of fine structure components are simulated, giving the estimated electron density around 8.3×1019m-3and 8.7×1019 m-3, respectively.