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The secrets of semiconductor detectors: How do they measure radiation so accurately?
In today's rapidly changing technological context, semiconductor detectors play an important role in the field of radiation measurement with their excellent performance. These devices are based on semiconductor materials (usually silicon or germanium) and are able to detect and measure the effects of incident charged particles, or photons. These detectors are widely used in radiation protection, gamma-ray and X-ray spectroscopy, and as particle detectors, where they have demonstrated their irreplaceable value.
The essence of semiconductor detectors lies in the detection of free charge carriers, which relies on carriers excited by radiation.
Detection Mechanism
In a semiconductor detector, when ionizing radiation enters the detector, it excites free electrons and electron holes within the detection material. The number of these free carriers is proportional to the energy of the radiation. This means that the number of electron-hole pairs induced per radiation event can be used to measure the energy of the radiation being tested.
Under the influence of the electric field, electrons and holes move to the electrodes respectively, thereby generating measurable pulses in the external circuit. This process is described by the Shockley-Ramo theorem. Compared with the gas detector, the energy required by the semiconductor detector to generate the electronics-cavity is relatively low, making the statistical variation of the pulse amplitude less and which improves the energy resolution. In addition, due to the fast speed of electrons, the time resolution is also excellent.
Detector Types
Silicon detector
Most silicon particle detectors transform them into dilateral bodies by doping narrow silicon strips, and then reverse bias. When the charged particles pass through these strips, they will cause small ionization currents, which can be detected and measured. This design makes the silicon detector configure tens of thousands of detectors around the collision point of the particle accelerator to accurately depict the operating path of the particles.
Diamond Detector
Diamond detectors share many similarities with silicon detectors but are expected to offer significant advantages in terms of high radiation hardness and very low drift current. They are also suitable for neutron detection. At present, the manufacturing cost of diamond detectors is high and the production is difficult.
Germanium detector
于 The detector is mainly used for gamma spectrometer and X -ray spectrum in nuclear physics. Its sensitive layer thickness can reach a few centimeters, so that they can be used as a complete absorption detector for gamma rays. Germanium detectors need to be kept at liquid nitrogen temperature to achieve good spectral working efficiency. This is because at higher temperatures, electrons can easily cross the energy band gap, introducing too much electrical noise, which also limits its application.
Cadmium Telluride and Zinc Cadmium Telluride Detectors
Cadmium cadmium (CDTE) and zinc 碲 cadmium cadmium (CZT) detectors have been developed for X -ray and gamma ray spectrum. The high density of these materials can effectively block X -rays and gamma rays higher than 20 KEV that cannot be detected by traditional silicon -based sensors. Because these two materials have a broadband gap, they can be operated under the condition that they are close to room temperature, which makes them have greater flexibility in applications.
Integrated Systems
Semiconductor detectors are often integrated into larger systems for various radiation measurement applications. For example, gamma spectrometers using high-purity germanium detectors are often required to measure trace amounts of gamma radionuclides in a low-background environment. As technology has advanced, transparent automated sampling systems have been developed to automatically move samples within a closed lead shield.
ConclusionAs semiconductor detectors are increasingly used in radiation measurement, their continuous technological innovation and improvement will further promote the development of nuclear physics and radiation protection. How will these high-tech detectors change our understanding of radiation in future applications?
