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Betavoltaic devices, also known as betavoltaic cells, are generators of electric current, in effect a form of battery, which use energy from a radioactive source emitting beta particles (electrons). A common source used is the hydrogen isotope, tritium. Unlike most nuclear power sources, which use nuclear radiation to generate heat, which then is used to generate electricity (thermoelectric and thermionic sources), betavoltaics use a non-thermal conversion process; converting the electron-hole pairs produced by the ionization trail of beta particles traversing a semiconductor.〔(A 25-Year Battery: Long-lived nuclear batteries powered by hydrogen isotopes are in testing for military applications ), Katherine Bourzac, Technology Review, MIT, 17 Nov 2009.〕 Betavoltaic power sources (and the related technology of alphavoltaic power sources〔NASA Glenn Research Center, (Alpha- and Beta-voltaics ) (accessed Oct. 4, 2011)〕) are particularly well-suited to low-power electrical applications where long life of the energy source is needed, such as implantable medical devices or military and space applications.〔 == History == Betavoltaics were invented over years ago. Early pacemakers used betavoltaics based on promethium, but were phased out as cheaper lithium-ion batteries were developed.〔 Early semiconducting materials weren't efficient at converting electrons from beta decay into usable current, so higher energy, more expensive—and potentially hazardous—isotopes were used. The more efficient semiconducting materials used today can be paired with relatively benign isotopes such as tritium, which produce less radiation.〔 The Betacel was considered the first successfully commercialized betavoltaic battery. 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「Betavoltaic device」の詳細全文を読む スポンサード リンク
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