Plasma afterglow circulation apparatus for decontamination of spacecraft equipment

Abstract

A newly developed apparatus using cold atmospheric plasma (CAP) is presented, providing a useful alternative decontamination method for spacecraft equipment. The designed setup uses the plasma afterglow generated by a surface micro-discharge (SMD) technology and works with a circulating gas flow of ambient air at room temperature. Additionally, the apparatus allows the control of gas flow, plasma power and humidity, and offers O3 monitoring and a variable treatment volume. Within this study we examined the apparatus' performance by evaluation of the inactivation efficacy of bacterial endospores Bacillus atrophaeus in different treatment volumes of 0.54 l, 1.8 l and 2.6 l. The experiments with Bacillus atrophaeus showed at least a 4.4 log reduction after the treatment times of 10, 20 and 30 min in the respective treatment chambers with a volume of 0.54 l, 1.8 l and 2.6 l. These results demonstrate that high sporicidal effects can be achieved with the newly developed apparatus, and that longer treatment times are needed for larger treatment volumes due to different filling rates of reactive components in different treatment volumes. Conclusively, these investigations illustrate the scalability of the designed apparatus up to 2.6 l for the afterglow treatment of samples with flat surfaces. The composition of the plasma afterglow was analysed by Fourier Transformation Infrared (FTIR) and UV absorption spectroscopy. The spectroscopic analyses identify O3, N2O, and HNO3 as predominant products of the CAP apparatus.