As the core equipment of radiation protection, the detection principle of personal dose alarm is mainly based on two technical paths: GM counter tube and semiconductor detector, which capture and quantify radiation signals through different physical mechanisms.
GM counter tube technology was the mainstream solution for early personal dose alarm devices. Its core structure is an ionization chamber composed of a central metal anode and a tube wall cathode, filled with inert gas (such as argon) and quenching gas (such as bromine vapor) inside. When radiation particles (such as beta and gamma rays) enter the tube, they ionize gas molecules to produce electron ion pairs. Under the action of a high-voltage electric field, electrons accelerate and collide with other gas molecules, triggering avalanche discharge and forming detectable electrical pulse signals. Quenching gas terminates discharge by absorbing excess energy, ensuring that only a single pulse is generated for each radiation event. The advantages of GM tubes are simple structure, low cost, and a detection efficiency of nearly 100% for beta rays. However, their sensitivity to gamma rays is low (about 10%), and there is a "dead time" effect (the interval between two pulses takes tens of microseconds), which may result in missed measurements at high dose rates.
Semiconductor detector technology represents the development direction of modern personal dose alarm devices. It uses silicon or germanium as the detection medium, and when the radiation particles enter the sensitive area, they will be excited to produce electron hole pairs. Under the action of an external electric field, charge carriers drift to the electrode, forming an electrical signal proportional to the energy of the radiation. The energy resolution of semiconductor detectors is much higher than that of GM tubes, and they can distinguish rays of different energies (such as low-energy X-rays and high-energy gamma rays) without dead time limitations, making them suitable for high dose rate environments. In addition, it is compact in size and has strong electromagnetic interference resistance. Some models also integrate Bluetooth and GPS modules, supporting real-time data transmission and remote monitoring. However, semiconductor detectors have strict manufacturing process requirements and need to operate at low temperatures (such as liquid nitrogen temperature) to suppress thermal noise, resulting in high costs.
In practical applications, personal dose alarm devices often use a combination of GM tubes and semiconductor detectors to balance sensitivity and cost. For example, in nuclear power plant inspection scenarios, GM tubes are used for rapid screening of radiation hotspots, while semiconductor detectors are used for precise measurement of accumulated dose to ensure the safety of personnel.