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About PMTs | Photomultiplier tubes (PMTs)

What is a photomultiplier tube?

Supports small-quantity and multi-type production

The basic structure of a photomultiplier tube is simple and can be manufactured by hand so that even a single product can be tailored according to the request. Since the shape, size, spectral response range or namely detection wavelength range and other characteristics can be customized, photomultiplier tubes are widely used in many applications including industry, medicine, and academic research where high sensitivity photodetectors are required.

A wide range of product lineup

We offer a wide range of product lineup with different detection wavelength ranges by combining various types of photocathodes, window materials, and glass bulb shapes.

What is a photomultiplier tube? Part2

What materials are used for light input windows?


  • Borosilicate glass
  • Quartz glass UV-transmitting glass
  • MgF2 crystal, etc.

The light input window material determines the short wavelength limit in the photomultiplier tube’s spectral response range.

Why use a vacuum?

Reason (1)

Photomultiplier tubes detect light by making use of the external photoelectric effect or namely the phenomenon in which electrons are released into the vacuum when light strikes a metal or semiconductor in a vacuum.

Reason (2)

High performance photocathodes with a good crystalline quality can be fabricated in a vacuum, and are capable of converting single photons into electrons.

Reason (3)

In a vacuum, only the signals are amplified so low-level light can be detected with high sensitivity.

What is a photocathode?

A thin photosensitive film formed on the inner side (vacuum) of the light input window. It converts light entering through the light input window into photoelectrons.

Types of photocathode

  • Bialkali photocathode for visible light region
  • Multialkali photocathode with sensitivity extending to near infrared region
  • Alkali-halide photocathode for UV light detection
  • GaAs, InGaAs (group III-V compound semiconductors) with sensitivity from UV to near infrared region

What is an electron multiplier?

An electron multiplier consists of multiple electrodes called dynodes. Photoelectrons released from the photocathode are accelerated by the voltage applied to the focusing electrodes to impinge on the secondary emissive surface of the first dynode where secondary electrons are generated. This process is repeated in all dynodes of the electron multiplier to in this way amplify the signal more than one million times.

There are various types of electron multipliers with different time response, output linearity, compactness, and ruggedness, and these are selectable according to the application purpose.


  • Substrate: Nickel metal, stainless steel, etc.
  • Secondary electron emissive material: Alkali-antimonide, beryllium oxide, etc.

Working to achieve even higher performance

We have been working to enhance the photomultiplier tube sensitivity to capture even lower level light, as well as to improve other characteristics to ensure even higher accuracy detection. Our efforts to achieve even higher photomultiplier tube performance are a never ending struggle to meet customer needs.

20-inch diameter photomultiplier tubes for scientific research



Facility name Kamiokande
(From 1983 to 1996)
(From 1996 to present)
(In planning stage)
Type No. R1449 R3600 R12860
Collection efficiency 40 % to 50 % 70 % 90 %
Electron transit time spread 8.0 ns 5.5 ns 2.4 ns

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