A method for minimizing microwave leakage into processing chamber of a microwave plasma system is provided. The method includes securing plasma traps to a plasma tube assembly, which is a cylindrical structure positioned upstream from the processing chamber and has a plasma-sustaining region. The plasma traps are electrically conductive disks surrounding the cylindrical structure and are positioned upstream from the processing chamber. The plasma traps include at least two electrically conductive disks. Each electrically conductive disk includes corrugated outer surfaces with plurality of corrugated peaks. The corrugated outer surface of the first electrically conductive disk is facing a corrugated outer surface of the second electrically conductive disk in a space-apart relationship to form an interstitial region between the electrically conductive disks. Both electrically conductive disk and the interstitial region form one of a set of upstream plasma traps and a set of downstream plasma traps relative to the plasma-sustaining region.