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光电倍增管

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光电倍增管(PMT)。
光电倍增管(PMT)。
光电倍增管内部的二次发射极(dynode)。
光电倍增管内部的二次发射极(dynode)。

光电倍增管Photomultiplier,简称PMT),是一种对紫外光可见光和近红外光极其敏感的特殊真空管。它能使进入的微弱光信号增强至原本的108倍,使光信号能被测量。

工作原理

光电倍增管示意图
光电倍增管示意图

光电倍增管是由玻璃封装的真空装置,其内包含光电阴极 (photocathode),几个二次发射极 (dynode)和一个阳极 (Anode)。入射光子撞击光电阴极,产生光电效应,产生的光电子被聚焦到二次发射极。其后的工作原理如同电子倍增管,电子被加速到二次发射极产生多个二次电子,通常每个二次发射极的电位差在 100 到 200 伏特。二次电子流像瀑布一般,经过一连串的二次发射极使得电子倍增,最后到达阳极。一般光电倍增管的二次发射极是分离式的,而电子倍增管的二次发射极是连续式的。

应用

光电倍增管集高增益,低干扰,对高频信号有高灵敏度的优点,因此被广泛应用于高能物理天文等领域的研究工作,与及流体流速计算、医学影像和连续镜头的剪辑。雪崩光电二极管(Avalanche photodiodes,简称APDs)为光电倍增管的替代品。然而,后者仍在大部分的应用情况下被采用。

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光电倍增管
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