People often ask “Does the electron microscope have radiation?”
Answering that the electron microscope has radiation will scare the customer, but saying “our electron microscope has no radiation” is not professional and honest enough.
This article makes a simple popularization of electron microscope radiation. I hope everyone has a more rational understanding of radiation.
Regarding the radiation safety issues of electron microscopes, it can be said that they are minimal.
Minimal ionizing radiation
Ionizing radiation exists in every corner of our daily life. Each person will be exposed to at least 2.4mSv (natural background radiation) radiation every year. According to the figure, it can be estimated that the dose when flying in an airplane is about 6uSv/h. (Note: 1mSv=1000uSv)
Instantaneous 1Sv can cause disease, and more doses can cause death. Everyone safely receives very small doses of natural background radiation every day. Generally speaking, if the same dose is absorbed in a shorter period of time, it will cause more harm; however, long-term cumulative doses will bring more profound effects, such as the risk of cancer.
X-ray radiation, if any, is produced only by backscattered electrons striking the sample.
Electron microscopes work by irradiating a sample with a beam of high-energy electrons and collecting signals to produce an image, during which a large number of X-rays are produced. Therefore, the electron microscope must have radiation.
Electron microscopes are well shielded, including viewing ports with lead-impregnated glass so that any X-rays generated inside the chamber do not penetrate the outside of the device.
In addition, the radiation dose is inversely proportional to the square of the distance, and the dose will drop significantly at a slightly further distance.
Radiation surveys when installing an electron microscope
1. Radiation surveys for X-ray leaks are required when electron microscopes are installed: Whenever the microscope is modified or accessories/accessories are added/removed, this can compromise radiation shielding.
2. Radiation investigations should be conducted under “worst case” conditions, if possible, such as:
- Highest accelerating voltage and beam current
- low magnification
- Beams crossed on the sample
- All apertures removed
3. The radiation level at a distance of 5 cm from the equipment should be lower than 0.5mR (measured by radiation safety (EH&S)). Essentially, all electron microscopes will have radiation readings that are indistinguishable from normal background radiation.