Radiation Detection and Measurement

Ionization Counters

电离计数器

Radiation detection can be accomplished by stretching a wire inside a gas-filled cylinder and raising the wire to a high positive voltage. The total charge produced by the passage of an ionizing particle through the active volume can be collected and measured. Different names are used for the devices based on the amount of voltage applied to the center electrode and the consequent nature of the ionizing events. If the voltage is high enough for the primary electron-ion pair to reach the electrodes but not high enough for secondary ionization, the device is called an ionization chamber. The collected charge is proportional to the number of ionizing events, and such devices are typically used as radiation dosimeters. At a higher voltage, the number of ionizations associated with a particle detection rises steeply because of secondary ionizations, and the device is often called a proportional counter. A single event can cause a voltage pulse proportional to the energy loss of the primary particle. At a still higher voltage, an avalanche pulse is produced by a single event in the devices called Geiger counters.

辐射检测可以通过在气体充满的圆柱体内拉一根导线，并将该导线提升到高正电压来实现。由离子化粒子通过活性体积所产生的总电荷可以被收集并测量。根据施加在中心电极上的电压量以及由此产生的离子化事件性质，设备有不同的名称。如果电压足够高，使初级电子-离子对能够到达电极，但不足以引起二次离子化，则该设备称为电离室。所收集的电荷与离子化事件的数量成正比，此类设备通常用作辐射剂量计。在更高电压下，由于二次离子化，与粒子探测相关的离子化数量急剧增加，此类设备通常称为正比计数器。单个事件可以引起一个与初级粒子能量损失成正比的电压脉冲。在更高的电压下，Geiger计数器中单个事件会产生雪崩脉冲。

Scintillation Counters

闪烁计数器

Radiation detection can be accomplished by the use of a scintillator: a substance which emits light when struck by an ionizing particle. The scintillation detectors used in the Geiger-Marsden experiment were simple phosphor screens which emitted a flash of light when struck by an alpha particle. Modern scintillation counters may use single crystals of NaI doped with thallium. Electrons from the ionizing event are trapped into an excited state of the thallium activation center and emit a photon when they decay to the ground state. Photomultiplier tubes are used to intensify the signal from the scintillations. The decay times are on the order of 200 ns and the magnitude of the output pulse from the photomultiplier is proportional to the energy loss of the primary particle.

辐射探测可以通过使用闪烁体来实现：一种在被电离粒子击中时会发出光的物质。用于盖革-马士顿实验的闪烁探测器是简单的磷光屏，当被α粒子击中时会发出一束光。现代闪烁计数器可能使用掺铊的NaI单晶体。电离事件产生的电子被捕获到铊激活中心的激发态，并在衰变到基态时发射一个光子。光电倍增管用于增强闪烁信号。衰减时间约为200纳秒，光电倍增管输出脉冲的幅度与初级粒子的能量损失成正比。

Some organic scintillators consist of a mixture of polystyrene and tetraphenyl butadine. They have the advantage of faster decay time (about 1 ns) and can be molded into experimentally useful configurations.

一些有机闪烁体由聚苯乙烯和四苯基丁二烯的混合物组成。它们的优点是衰减时间（约1 ns）更快，可以制成实验上实用的形状。

Particle Track Devices

粒子轨迹设备

Radiation detection can take the form of devices which visualize the track of the ionizing particle. Cloud chambers can show the track of a passing particle which can be photographed. D. A. Glaser's invention of the bubble chamber in 1952 largely replaced the cloud chamber. Placed in an intense magnetic field, the curvature of the tracks of the primary particles and their products give information about their charge and momentum.

辐射探测可以以可视化电离粒子轨迹的装置形式出现。云室可以显示经过的粒子轨迹，并可被拍照。1952年D. A. Glaser发明的泡室 largely 替代了云室。当置于强磁场中时，初级粒子及其产物轨迹的弯曲程度可提供关于其电荷和动量的信息。

Spark chambers can also visualize the tracks of particles and has the advantage that the paths can be recorded electronically.

火花室也能可视化粒子的轨迹，并且其优点在于轨迹可以被电子记录。