Everhart–Thornley detector

Everhardt-Thornley detector

Everhart–Thornley detector

The Everhart–Thornley detector (ET detector) is a type of scintillation detector used in scanning electron microscopy (SEM) to collect secondary electrons and produce an image. It was invented by Thomas Everhart and Richard Thornley in the early 1960s.

Principle of Operation

The Everhart–Thornley detector operates by attracting secondary electrons emitted from the surface of a specimen when it is bombarded with a focused beam of primary electrons. These secondary electrons are then accelerated towards a scintillator by a positive bias applied to a collector grid or a Faraday cage. The scintillator emits photons when struck by the secondary electrons. These photons are then guided through a light pipe to a photomultiplier tube (PMT), where they are converted into an electrical signal. This signal is amplified and used to modulate the brightness of a display, creating an image of the specimen's surface.

Components

The main components of the Everhart–Thornley detector include:

• Scintillator: A material that emits light when struck by electrons.
• Photomultiplier tube (PMT): A device that converts light into an electrical signal and amplifies it.
• Collector grid/Faraday cage: A positively biased component that attracts secondary electrons.
• Light pipe: A medium that guides photons from the scintillator to the PMT.

Advantages

The Everhart–Thornley detector is highly efficient in collecting secondary electrons, which makes it ideal for producing high-resolution images of the surface topography of specimens. It also has a fast response time, which is beneficial for dynamic studies.

Applications

The ET detector is widely used in various fields, including:

• Materials science
• Biology
• Nanotechnology
• Forensic science

Related Pages

• Scanning electron microscope
• Secondary electron
• Scintillation detector
• Photomultiplier tube
• Thomas Everhart
• Richard Thornley

See Also

• Electron microscope
• Transmission electron microscopy
• Backscattered electron detector