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The plasma window (not to be confused with a ''plasma shield'') is a technology that fills a volume of space with plasma confined by a magnetic field. With current technology, this volume is quite small and the plasma is generated as a flat plane inside a cylindrical space. Plasma is any gas that has had some of its atoms or molecules ionized and is generally held to be a separate phase of matter. This is most commonly achieved by heating the gas to extremely high temperatures, although other methods also exist. Plasma becomes increasingly viscous (thick) at higher temperatures, to the point where other matter has trouble passing through. A plasma window's viscosity allows it to separate gas at standard atmospheric pressure from a total vacuum, in fact it is reported that it can withstand a pressure difference of up to nine atmospheres.〔(【引用サイトリンク】title=Hot mettle )〕 At the same time, the plasma window will allow radiation such as lasers and electron beams to pass. This property is the key to the plasma window's usefulness — the technology of the plasma window permits for radiation that can only be generated in a vacuum to be applied to objects in an atmosphere. One of the major applications of this technology is electron beam welding, where it has made EBW practical outside of a hard vacuum. == History == The Plasma Window was invented at Brookhaven National Laboratory by Ady Hershcovitch and patented in 1995.〔(【引用サイトリンク】title= United States Patent: 5578831:Hershcovitch (November 26, 1996) Method and apparatus for charged particle propagation )〕 Further inventions using this principle include the Plasma Valve in 1996.〔(【引用サイトリンク】title= United States Patent: 6528948:Hershcovitch (March 4, 2003) Plasma valve )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Plasma window」の詳細全文を読む スポンサード リンク
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