Surface Sterilization with High Energy Ions

Summary form only given. There is a commercial need for the sterilization of food containers in the bottling and packaging industry, and other plastic surfaces that will destroy bacterial spores and other microbes on a short time scale and without chemical agents. We have demonstrated that high-energy (e.g. 50 KeV) ions, extracted from a low-density hydrogen plasma using an ion implantation approach, impart sufficient spore damage to prevent germination. Recently, we have carried out additional studies on variations of a number of parameters, such as the total ion dose, voltage variations, pulse width, ion species and background pressure. The experiments are conducted in a 1 meter long, 8 inch diameter chamber under a modest vacuum. An R.F. plasma is established using a 7 watt, 25 MHz source. The spores are placed on 1-inch diameter solid brass spheres by a biological testing service. The spheres are inserted into the chamber prior to initiation of the plasma, then pulsed with a high voltage pulser to a nominally 50000 volt negative bias, thereby attracting the positive plasma ions to the surface of the brass spheres. Typically, 4000 individual negative pulses are applied over an 8 second period and then the sample is removed and analyzed. The results indicate that spore destruction occurs over a wide range of parameters and is indicative of the potential to destroy spores in one second or less