Problem mrc SNF 2011-11-08 01:48:58: MRC plasma not stable

[zguo at snf.stanford.edu]

1) Base pressure around 1.4~1.5 mtorr, was able to reach 
2) running oxygen 15sccm, ignite the plasma at around 15mtorr, when lower the pressure at around 8~10mtorr, the plasma extinguishes many times.
MRC was stable for the same recipe before.