What is a Photomultiplier tube (PMT)?

Photomultiplier tubes (PMTs) are among the most sensitive of all light sensors and are used to detect faint light. Tubes without a multiplication function are called phototubes (PT). The structure of a photomultiplier tube is as follows: First, light (photons) enters through an incident window and strikes a photocathode (cathode), generating photoelectrons. The photoelectrons are attracted by the high voltage applied to the cathode, electron multiplier (dynode), and anode. The photoelectrons are then accelerated and multiplied as they travel through the vacuum state. Most photomultiplier tubes have 9 to 12 dynodes and amplify to the 5th to 8th power of 10, and finally output as a current. Photomultiplier tubes are characterized by their ability to achieve extremely high current amplification rates. There are two types of photomultiplier tubes: head-on type with a photosensitive area at the tip and side-on type with a photosensitive area at the side. There are numerous types of photocathodes with different photosensitive surface sizes and wavelength sensitivities.

Construction of a photomultiplier tube - Photomultiplier Tubes (PMT)
Construction of a photomultiplier tube

Photomultiplier tube applications

Photomultiplier tubes are used as secondary electron detectors in scanning electron microscopes (SEM). Secondary electrons generated from the sample are converted to light by the detector's scintillator and acquired as a signal by the PMT. The amount of secondary electrons becomes the amount of current, which is the intensity of the image. PMT is also used in Nox and Sox meters, which measure gas concentrations by irradiating sulfur oxides and nitrogen oxides with ultraviolet light and capturing the faint light emitted by the oxides in their excited states. In blood tests, PMT is used for fluorescence analysis, which analyzes the weak luminescence generated by reagent reactions. Kamiokande, which detects neutrinos, has become very famous, having won the Nobel Prize. If a scintillator, a material that converts radiation into light, is placed in front of the photomultiplier tube, it can be used for radiation detection and is called a survey meter. Radiation detection devices using photomultiplier tubes are used in gamma-ray detectors, gate monitors, and monitoring posts. In the past, they were used in CT scanners, but recently semiconductor sensors have been used.

High voltage power supply for photomultiplier tubes

The photomultiplier tube is characterized by its ability to achieve an extremely high current amplification ratio, but this also means that "electrical noise and voltage blurring that occurs when voltage is applied are multiplied in the same way. Even if photoelectrons are multiplied, if they are buried in noise that is also multiplied, detection becomes difficult and meaningless.

Most photomultiplier tubes operate at voltages ranging from 500 V to 2000 V. This also means that even the slightest fluctuation in the applied voltage is multiplied from the 5th power of 10 to the 8th power of 10 in the photomultiplier tube and appears as output. Therefore, in order to accurately detect weak light, a "low-noise" and "highly stable" high-voltage power supply that can fully demonstrate the true value of the photomultiplier tube is essential, in addition to the performance of the photomultiplier tube itself.

Matsusada Precision recommends power supplies for photomultiplier tubes

Matsusada Precision offers a diverse lineup of more than 1000 models of high-voltage power supplies. In particular, we have thoroughly brushed up "low noise" and "high stability" and perfected the "high voltage power supply dedicated for photomultiplier tubes" as the optimum high voltage power supply for photomultiplier tubes. There are various types of high-voltage power supplies for photomultiplier tubes, including bench-top types, types that are built into equipment, ultra-compact types for mounting on printed circuit boards, and models that combine a high-voltage power supply, bleeder circuit, and socket in a single unit. Customers can choose from these extensive models for the power supply best suited to their requirements.
As an example, we introduce the integrated type of high-voltage power supply, bleeder circuit, and socket.

We offer a variety of high-voltage power supplies for photomultiplier tubes.

PMT Socket power supply

Since it is an integrated type, you can use it simply by inserting a compatible PMT.
Socket assembly type with high voltage power supply and voltage divider circuit for driving photomultiplier tubes. The highly stable and low-noise operation of the photomultiplier tube is achieved by simply plugging in an appropriate photomultiplier tube and supplying a voltage of ±15 to ±24 Vdc.

PCB mounte type (on-board)

Often used when photomultiplier tubes are used as detectors in analyzers and inspection instruments.
Since the power supply is to be built into the equipment, the design of heat dissipation, as well as the temperature coefficient of the power supply, is an important factor in the selection process. Some models of Matsusada Precision have achieved very good temperature coefficients of 20 ppm/°C typical.

Chassis mounte type (module)

Often used when photomultiplier tubes are used as detectors in analyzers and inspection instruments.
Since the power supply is to be built into the equipment, the design of heat dissipation, as well as the temperature coefficient of the power supply, is an important factor in the selection process. Some models of Matsusada Precision have achieved very good temperature coefficients of 20 ppm/°C typical.

Benchtop type/Rackmount type

Amazingly high performance is achieved, including a model that achieves ultra-low ripple of only 5mv (2.5ppm, 2kV output type)!
Remote functions and various interfaces (some optional) further expand the range of usage.

Related Technical Article

Matsusada's collection of Photomultiplier tube (PMT) precise High Voltage modules!!

Related words:
  • electron microscope
  • neutrino
  • gamma-ray
  • CT scanner
  • radiation
  • Nox meter
  • Sox meter
  • fluorescence analysis
  • reagent
  • positioning PMT