A method to improve plasma discharge efficiency by attaching one or more booster chambers to the main discharge chamber is disclosed here. The booster chamber functions as a plasma discharge amplification device for the main discharge chamber. It improves plasma density significantly, especially at pressure below 50 mTorr. Compared with traditional inductively coupled plasma (ICP) source, the strength of the plasma source enhanced with booster chamber has been improved several folds at low pressure conditions. Booster chamber can also be used as a convenient high speed plasma etching and deposition processing chamber for small samples. A method to gauge plasma strength by measuring plasma emission intensity has also been disclosed in this application.