Elements of photomultiplier technology, when integrated differently, are the basis of night vision affinity photo manual pdf. Research that analyzes light scattering, such as the study of polymers in solution often use a laser and a PMT to collect the scattered light data.
1: Schematic of a photomultiplier tube coupled to a scintillator. This arrangement is for detection of gamma rays.
2: Typical photomultiplier voltage divider circuit using negative high voltage. Incident photons strike the photocathode material, which is usually a thin vapor-deposited conducting layer on the inside of the entry window of the device.
Electrons are ejected from the surface as a consequence of the photoelectric effect. These electrons are directed by the focusing electrode toward the electron multiplier, where electrons are multiplied by the process of secondary emission. The electron multiplier consists of a number of electrodes called dynodes. 100 Volts, than the preceding one.
A primary electron leaves the photocathode with the energy of the incoming photon, or about 3 eV for “blue” photons, minus the work function of the photocathode. A small group of primary electrons is created by the arrival of a group of initial photons. 1, the number of primary electrons in the initial group is proportional to the energy of the incident high energy gamma ray. The primary electrons move toward the first dynode because they are accelerated by the electric field.
100 eV kinetic energy imparted by the potential difference. Upon striking the first dynode, more low energy electrons are emitted, and these electrons are in turn accelerated toward the second dynode.
The geometry of the dynode chain is such that a cascade occurs with an exponentially-increasing number of electrons being produced at each stage. This last stage is called the anode. The necessary distribution of voltage along the series of dynodes is created by a voltage divider chain, as illustrated in Fig. In the example, the photocathode is held at a negative high voltage of order 1000V, while the anode is very close to ground potential.