焦電結晶上での二元X線発生機構

　タンタル酸リチウム単結晶の加熱/ 冷却に伴うX 線発生現象について，真空度および昇温温度を制御した実験を行い，その発生機構について検討した．X 線発生は既往の報告より三桁高い真空度10-4 Pa でも起こり，X線発生終了までの全積分強度は1 Paまで一定であった．タンタル酸リチウム単結晶の焦電性を利用したX線発生は，結晶表面近傍で起こる放電に伴って残留ガスより生じる高密度の荷電粒子の衝突を起源とする数分以内で終了する現象と，もともと残留ガス中に存在する荷電粒子を起源として10分以上継続するものとの二元機構であると結論された．焦電結晶の昇温する速度を一定にすることでX線発生強度が一定となる時間を延長することができた．

X-ray emission behavior from a LiTaO3 pyroelectric single crystal during heating and cooling procedure was investigated by controlling the degree of vacuum in the range of 10-4 through 20 Pa, and the heating procedure. X-ray emission was confirmed at the vacuum degree of 10-4 Pa, which was higher than those for previous reports by three orders of magnitude. The total emission intensity was almost constant in the vacuum range among 10-4 Pa and 1 Pa. X-ray emission with the use of pyroelectricity was caused by individual two processes: One is accompanied by electric discharge around z-plane of LiTaO3 single crystal within a few minutes, and is sensitive to the degree of vacuum; the other is caused by collision of floating charged particles onto the plane. X-ray emission related to the floating particles continues more than 10 minutes and is less sensitive to the vacuum. The emission intensity could be kept constant for 10 min by controlling heating rate of LiTaO3.

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