Positron annihilation lifetime spectrometer based on silicon photomultiplier (SiPM)

Abstract

The invention discloses a positron annihilation lifetime spectrometer based on a silicon photomultiplier (SiPM), and the lifetime spectrometer comprises a SiPM detector module, an analog signal processing module, a timing and discrimination circuit module, a digital acquisition circuit module, a matching unit and a low voltage power supply module, wherein the SiPM detector receives gamma photons and generates scintillation light, which is converted into a photoelectric signal by the SiPM; the photoelectric signal is processed into a pulse signal through further amplification, noise reduction and the like by the analog signal processing module; the pulse signal is timed and discriminated by the timing and discrimination circuit module to obtain position information, energy information and time information of the gamma photons; the information is acquired by the digital acquisition circuit module and filtered by the matching unit to a meeting event; and all the modules are powered by thelow voltage power supply module. The positron annihilation lifetime spectrometer can improve measurement accuracy, reduce measurement time, greatly reduce cost, reduce power supply requirements and simplify the spectrometer structure.

Description

technical field [0001] The invention relates to the technical field of a positron annihilation lifetime spectrometer, in particular to a positron annihilation lifetime spectrometer based on a silicon photomultiplier (SiPM). Background technique [0002] Positron annihilation spectroscopy is widely used in solid-state physics and materials science research. After the positron enters the material sample, it will lose energy through various forms. There are defects such as vacancies and dislocations in the sample. Electrons around the defect are annihilated. The lifetime of a positron can reflect the electron concentration at its annihilation site. Positron annihilation lifetime spectroscopy is also one of several methods that can detect single-atom-scale defects. [0003] With advances in semiconductor technology, silicon photomultipliers now offer an attractive alternative to PMTs. A silicon photomultiplier (SiPM) is an optoelectronic sensing device that solves the proble...

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Problems solved by technology

[0006] Conventional positron lifetime spectrometers usually use plastic scintillators or barium fluoride crystals or bluestone bromide crystals coupled with photomultiplier tubes to form scintillation detectors as the start and stop detectors of lifetime spectrometers, but such detectors have certain limitations. shortcoming

Although the plastic scintillator emits light quickly and has a small decay constant, its detection efficiency for gamma photons is low

Barium fluoride scintillator has short decay time and high density, but still has luminescent components with long decay time, and it is easy to accumulate in the case of high count rate; bromide crystal is easy to deliquescence, which has a negative effect on the temperature and humidity of the environment. requirements, not suitable for long-term use

[0007] The high voltage of the photomultiplier tube required for the scintillation detector in the lifetime spectrometer ranges from several thousand volts. Although the response time is fast, the single photon detection ability is weak, and superior time resolution cannot be achieved.

Secondly, the external environment will also affect the performance of PMT

Changes in temperature and humidity, as well as the presence or absence of vibration all affect the operation of the PMT; in addition, the external magnetic field will have a great impact on the PMT, and a few Gaussian magnetic fields can greatly reduce the gain

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