Photomultiplier tube

Photomultiplier tube: PhotoMultiplier Tube, abbreviated as PMT, is a photodetector with extremely high sensitivity and fast response speed. The scanning device is actually an electron tube, and the photosensitive material is mainly an oxide of metal ruthenium which is doped with oxides of other active metals (for example, lanthanoid metals) to improve the sensitivity and correct spectra. Curve, photocathode ray tubes made of this material, can emit electrons under the irradiation of light, we can call it photoelectron, it is accelerated through the grid to impact the anode, the final formation of the current.

In all kinds of photosensitive devices, the photomultiplier tube is the best performance, and it is far ahead of other photosensitive devices in terms of sensitivity, noise figure, and dynamic range. What's more commendable is that its output signal is quite large. Maintaining a highly linear output, the output signal can be directly obtained with very accurate color reproduction without any modification.

At the same time, the photomultiplier tube has the highest production cost in various photosensitive devices, and since only one pixel can be scanned at a time, the scanning speed is very slow, and scanning a graph often takes several tens of minutes. Therefore, photomultipliers are now used only on the most professional drum (big drum) scanners. The price of such scanners is very high, ranging from a few hundred thousand yuan to as much as a million yuan. Unattainable noble products are not suitable for general family use.