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Plasma processing apparatus

This application is based on application No. JP2006-351345 filed in Japan, the contents of which are hereby incorporated by reference.

1. Field of the Invention

The present invention relates to a plasma processing apparatus for inactivating toxins such as endotoxins and abnormal prions.

2. Description of the Background Art

Endotoxins are lipopolysaccharides which form the outer membrane of the cell wall of gram-negative bacteria. It is known that only a microscopic amount of endotoxins have heat buildup, and it is necessary to inactivate endotoxins sticking to medical tools in order to prevent medical accidents. As for methods for inactivating endotoxins, a gamma ray method, an electron beam method, an ethylene oxide gas method, a hydrogen peroxide gas plasma method, an autoclave method and a dry heat method have been examined (see, for example, Kazunari Hosofuchi et al., “Inactivation of Dry Endotoxins in Accordance with Various Sterilizing Methods,” Tokyo Metropolitan Industrial Technology Laboratory Research Report, Tokyo Metropolitan Industrial Technology Laboratory, 1999, No. 2, pp. 126 to 129).

In accordance with the conventional methods other than the dry heat method, however, the activity of endotoxins cannot be sufficiently lowered. In the case where typical processing conditions are adopted, for example, the activity of endotoxins can only be lowered to approximately ¼ in accordance with the gamma ray method, the electron beam method or the ethylene oxide gas method, to approximately 1/20 in accordance with the hydrogen peroxide gas plasma method, and to approximately 1/9 in accordance with the autoclave method. Meanwhile, though the activity of end toxins can be lowered to approximately 1/105 in accordance with the dry heat method, it is necessary to heat a treatment object to approximately 250° C., and therefore, there is a problem, such that the treatment object is damaged.

Here, this problem with inactivation is also present with toxins other than endotoxins such as abnormal prions, which are assumed to be toxins causing bovine spongiform encephalopathy.

FIG. 1 is a diagram showing dissociation energy of various gas molecules;

FIG. 2 is a schematic diagram illustrating discharge states and rough voltage waveforms of electric pulses;

FIG. 3 is a schematic diagram illustrating a general structure of endotoxin;

FIG. 4 is a perspective view of a reactor of a plasma processing apparatus in an embodiment;

FIG. 5 is a cross-sectional view of the reactor of the plasma processing apparatus in an embodiment;

FIG. 6 is a diagram illustrating wavelength dependence of reflectivity of various metal films;

FIG. 7 is a diagram showing an example of voltage waveform and current waveform of electric pulse;

FIG. 8 is a diagram showing a structure of an IES circuit;

FIG. 9 is a diagram showing an operation of the IES circuit;

FIG. 10 is an explanatory diagram illustrating operations of the plasma processing apparatus; and

FIG. 11 is a diagram showing drops of activity of endotoxins.