Microchannel plates are solid state detectors that have parallel arrays of tiny single channel electron multipliers all combined together in a parallel array. Channel densities are around 1-10 million channels/cm2 as shown in Figure 1.
Figure 1. Microchannel plate made up of microscopic electron multiplier channels
These devices can be used for detection of ions, UV photons, electrons and soft and hard X-rays. Suring operation, an input event striking the focal plane will cause a flood of electrons causing an amplification factor of up to 100,000. Cascading of a second or third array can cause an amplification factor of 100,000,000 with less than 1 count/sec/cm2 additional noise.
Various Designs of Microchannel Plates
Microchannel plates were developed initially to be used in image intensifier tubes for night vision applications.
Presently, the round 18 mm format is the most common but it is possible to produce MCPs in a broad range of shapes and sizes from 2 to 160 mm.
Fabrication of microchannel plates is possible and also formed in large wafers.
After fabrication, they can be formed into complicated shapes by laser cutting, diamond milling or laser ablation. It is possible to shape microchannel plates to match focal planes and also optimize the detection efficiency.
It is also possible to fabricate microchannel plates with center holes that enable through plate sample interrogation.
This feature is suitable for scanning electron microscope (SEM), focused ion beam and linear reflectron time of flight mass spectrometry.
Figure 2. Schematics of TOF mass spectrometry and SEM/FIB analysis techniques
Narrow arrays are suitable for magnetic sector mass spectrometers.
Microchannel plates designed in arc sections and are suitable to be used as a detector in an ion or electron energy analyzer.
Annular ring shaped micro channel plates can be used as a detector in a hemispherical energy analyzer system.
It is not necessary that microchannel plates are flat. They may be spherical as shown in Figure 4 or they may be cylindrical to match the instrument’s focal plane. This finds applications in vacuum ultraviolet spectrometers where the radius of curvature can be matched to the Roland Circle as shown in Figure 3.
Figure 3. Curved microchannel plates
Micro Pore Optics
Sophisticated microchannel devices called micro pore optics were developed comprising millions of square channels arranged in a properly defined order.
The surfaces present in the square channels have an almost perfect flatness and minimal roughness. X-ray and UV photons collimated due to total internal reflection at grazing incidence angle inside the micro pore channels.
It is now possible to fabricate microchannel plates in sizes ranging from 2 to 160 mm. Laser cutting, laser ablation and diamond milling has enabled the fabrication of complicated shapes.
Microchannel plate geometries including annular rings, center holes, trapezoidal formats and rectangular arc segments have been produced. Trapezoidal segments can be used to create large area mosaic detectors. Microchannel plate geometries are restricted only by the imagination of the instrument designer.
PHOTONIS is a leader in the innovation and manufacture of ion, electron and photon detection and amplification components that are the critical enabling technology within many analytical instruments.. PHOTONIS is a market leader in image intensifiers, digital low-light cameras, mass spectrometer detectors, nuclear safety, power tubes and custom detection components for physics and space research instruments. Our products are manufactured in several facilities globally, including PHOTONIS France, PHOTONIS Netherlands and our three facilities that comprise PHOTONIS USA.
Our products are award-winning for their innovation and quality. PHOTONIS products can be found on most space telescopes, in many high-energy physics research laboratories, and in night vision goggles around the globe where highly sensitive low light amplification is required. We are also key suppliers to the nuclear industry with our gamma and neutron detectors, and to defense industries globally with digital and portable solutions.
This information has been sourced, reviewed and adapted from materials provided by PHOTONIS Technologies S.A.S.
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