Characteristics of surface sterilization using electron cyclotron resonance plasma

The characteristics of surface sterilization using electron cyclotron resonance (ECR) plasma were investigated. High-energy electrons and oxygen radicals were observed in the ECR zone using electric probe and optical emission spectroscopic methods. A biological indicator (BI), Geobacillus stearothermophilus, containing 1 x 10(6) spores was sterilized in 120 s by exposure to oxygen discharges while maintaining a temperature of approximately 55 degrees C at the BI installation position. Oxygen radicals and high-energy electrons were found to be the sterilizing species in the ECR region. It was demonstrated that the ECR plasma could be produced in narrow tubes with an inner diameter of 5mm. Moreover, sterilization tests confirmed that the spores present inside the narrow tube were successfully inactivated by ECR plasma irradiation. (C) 2016 The Japan Society of Applied Physics