Development Of New Portable Contamination Monitor For Alpha And Beta Measurement

At the place where radioactive materials are used,the staff needs to determine whether the working environment is contaminated by radioactive materials.The portable contamination monitor for alpha and beta measurement is such an instrument that is specially used to detect the contamination of the worktop,floor,human body surface,clothing surface,etc.The surface emissivity response,repeatability,relative inherent error,stability and other parameters of domestic portable contamination monitors for alpha and beta measurement have a certain gap with foreign instruments,but foreign contamination monitors rarely combine GNSS,USB,wireless charging technology.After a comprehensive analysis of the design principles,advantages and disadvantages of the existing portable contamination monitors at home and abroad,this paper designs a new portable contamination monitor for alpha and beta measurement with high detection efficiency and high stability.The overall design of the instrument is divided into hardware and software.The hardware part mainly includes four parts: detectors module,pulse signal processing module,MCU and its external devices module,and power management module.The main detector of the instrument consists of a plastic scintillator coated with Zn S(Ag)and a photomultiplier tube,which can convert the received ? and ? rays into electrical pulse signals of different forms and output.The external detector can be a gamma detector,which can convert gamma rays into electrical pulse signals.The pulse signal processing module mainly includes an inverting integral filter circuit,a hysteresis comparison circuit and a monostable trigger circuit to realize the inversion,amplification,discrimination and shaping of the detector output signal,and then input the signal to the embedded MCU for further process.The embedded MCU selects the low-power STM32L496RET6,which externally expands the functions of SD card,serial screen,buttons,buzzer to complete data processing,data storage,humancomputer interaction,and threshold alarm.Through the USB interface,the firmware code can be written and communicated with the computer host computer.The paper also expands the Bluetooth module and GNSS module,which can realize wireless communication and obtain accurate time and position.The power management module is composed of a 3A charging circuit module,a power monitoring module,a DC-DC level conversion module and a high-voltage power supply module.The software part includes two parts: embedded software and host computer software.The embedded software is developed on the IAR platform using C language.The Free RTOS real-time operating system is transplanted to implement multi-task scheduling.The Fat FS file management system is used for file management.The host computer software is developed on the Visual Stdio platform using C # language to realize functions such as data collection and file saving.The new portable contamination monitors for alpha and beta measurement developed by this subject has been preliminarily tested,and the surface emissivity response,repeatability and relative inherent error are better than the national standard data requirements.