How a Scintillation Counter Works

1  What is a scintillator?

A scintillator is a material that absorbs high‑energy radiation (X‑rays, electrons, γ‑rays or ions). It re‑emits part of that energy as visible light. Different phosphors are tuned to different forms of radiation:

• X‑ray scintillators – gadolinium oxysulphide (Gadox) coatings respond to diagnostic‑energy and hard X‑rays and glow green‑yellow at ~545 nm.
• Phosphor‑screen scintillators – a phosphor layer (often Gadox or P43) that converts incident electrons or X‑rays into visible photons for cameras, SEMs or non‑destructive testing.
• EBSD phosphor screens – ultra‑thin coatings optimised for the low‑energy electrons used in electron‑backscatter diffraction.

2  From flash of light to digital read‑out: the counter chain

• Emission – Radiation strikes the scintillator and a burst of photons is released within a few nanoseconds.
• Optical coupling – The light is guided (via optical grease, a fibre‑optic plate or direct deposition) to a photosensor such as a photomultiplier tube (PMT), a silicon photomultiplier (SiPM) or a low‑noise photodiode.
• Photo‑conversion – Inside a PMT the photons hit a photocathode – typically a cesium–antimony (Cs–Sb) alloy – ejecting electrons via the photo‑electric effect. Roughly 300 eV of photon energy is needed to free each photo‑electron.
• Gain stage – Those electrons cascade through dynodes, multiplying up to 10⁶ times, so even a tiny flash becomes a clear electrical pulse.
• Pulse processing – The pre‑amp and counter measure pulse height (proportional to light intensity) and tally events per second, giving both radiation dose and energy information.

Because the detection chain is proportional, an X‑ray that deposits twice as much energy in the phosphor will (ideally) generate a pulse twice as large – critical for spectroscopy and medical imaging.

3  Why material choice and build quality matter

• Light output and decay time – Our Gadox:Tb screens deliver high brightness with a decay time of ~1 ms, ideal for static imaging, while Gadox:Pr offers faster decay for high‑frame‑rate systems.
• Substrate options – We can coat glass, fibre‑optic plates, stainless‑steel, copper, aluminium, silicon and even the cathode of vacuum tubes, matching your optical pathway and thermal budget.
• Clean‑room manufacture. All screens are produced in our Class 10 000 (ISO 7) cleanroom. This ensures uniform grain structure, minimal contamination and traceable ISO 9001:2015 quality.

4  Common applications

• Medical & dental imaging – low‑dose digital radiography, CT and mammography.
• Security screening – airport scanners and postal X‑ray cabinets.
• Scientific research – synchrotron beamlines, neutron detectors and university labs.
• Industrial inspection – weld radiography, composites NDT and PCB analysis.
• Electron microscopy – EBSD pattern capture and e‑beam detection in SEM/TEM.

5  Specifying the right screen

If you need help choosing pixel size, emission peak, thickness or substrate, our engineers are on hand. We can provide prototype samples, large production runs and bespoke one‑off screens – with regular progress updates and full confidentiality under NDA where required.

Ready to talk scintillators?

Call us on +44 (0) 1424 850 004 or email info@analyticalcomponents.uk to discuss your project. Whether you require a single phosphor screen or a batch of custom X‑ray scintillators, Analytical Components has the expertise and facilities to deliver on time and to specification.