Abstract: This paper introduces the design scheme of a spectrum-based nuclear logging tool, aiming to develop a portable logging tool suitable for uranium exploration and meet the needs of logging production. The instrument uses a CdZnTe semiconductor nuclear radiation detector and a high-end 32-bit embedded ARM processor S3C2410A as the core of the instrument system control. An embedded Linux operating system is ported to this hardware platform, and MiniGUI-based logging tool monitoring terminal software is developed. The instrument features real-time performance, small size, low power consumption, high sensitivity, low cost, and portability. Keywords: Embedded system; Linux; MiniGUI; Nuclear logging instrument; Cadmium zinc telluride semiconductor detector[b][align=center]Energy Spectrum Nuclear logging Instrument based on Embedded System SHEN Hong-zhong, TANG Bin (School of Information Engineering, East China Institute of Technology, Fuzhou 344000, China)[/align][/b] Abstract: This paper introduces a design project of energy spectrum nuclear logging instrument, the purpose of Such instrument was to provide a portable device suitable to the prospecting and exploration of uranium deposit. This instrument uses CdZnTe detector as nuclear radiation detector and S3C2410A, a 32-bit high performance embedded ARM processor, as micro processor unit. Based on this hardware platform, embedded Linux system is ported. The monitoring system of nuclear logging instrument is developed by using MiniGUI. The instruments carry the characteristic of small size, low power, high sensitivity, low cost, and outstanding portability. Key Words: embedded system; Linux; MiniGUI; nuclear logging instrument; CdZnTe detector 1 Introduction Civilian non-power nuclear technology is a high-tech field encouraged by the state. Among them, nuclear logging technology is one of the cutting-edge logging technologies that has developed rapidly with the advancement of modern science and technology and its application in geological and mineral exploration fields such as oil, coal, and uranium. Currently, there are relatively few domestically produced instruments suitable for nuclear logging in uranium mines. The main ones include the HFC-1 gamma-ray spectrometer logging instrument developed by Chengdu University of Technology and the HD-4002 integrated logging instrument developed by the Beijing Research Institute of Nuclear Geology. Most of these instruments use a laptop computer as the control core of the logging instrument system. In order to better adapt to the complex environment of field measurement work and facilitate field portability, this paper will use an embedded system based on a 32-bit ARM processor as the control core of the logging instrument system, and develop corresponding software and hardware based on this. 2 Theoretical Basis of Gamma-ray Spectrometer Nuclear Logging Instrument As is well known, a certain amount of radioactive elements exist in the rocks and soil of the Earth's crust, which can spontaneously emit radioactive rays. In nature, these radioactive rays mainly originate from naturally occurring radioactive elements such as the uranium-238 series, thorium-232 series, and potassium-40 series. These radioactive elements have distinct gamma-ray characteristic peaks; for example, the characteristic peaks of uranium, thorium, and potassium are 1.76 MeV, 2.62 MeV, and 1.47 MeV, respectively. Therefore, the radioactive element composition at the measurement point can be determined based on the measured energy spectrum data, i.e., qualitative analysis of radioactive elements can be performed. Furthermore, the content of a radioactive element is directly proportional to its gamma-ray intensity. Therefore, by calculating the gamma-ray intensity of a radioactive element, the corresponding radioactive element content can be obtained. Quantitative interpretation methods for radioactive elements mainly include the average content method, the traditional stripping method, and the point-by-point stripping deconvolution interpretation method. Energy spectrum-based nuclear logging is a non-destructive testing method that determines the composition and content of certain elements in a formation by studying the distribution characteristics of naturally generated or artificially excited radioactive ray spectra along the well axis. A gamma-ray energy spectrum logging tool is an instrument used to measure gamma-ray energy spectra in the field to analyze the properties and content of radioactive elements such as uranium, thorium, and potassium. 3. Overall Design of the Nuclear Logging Tool The gamma-ray energy spectrum logging tool must meet the requirements of small size, stable performance, powerful functions, high sensitivity, and ease of portability in the field. To address these requirements, the following design scheme is proposed for the gamma-ray energy spectrum logging tool: 3.1 Data Acquisition Hardware System Design Scheme The data acquisition hardware system mainly consists of a downhole probe, an automatic winch, and a gamma-ray energy spectrum acquisition circuit. The downhole probe mainly includes a nuclear radiation detector, a preamplifier, a probe casing, and a power supply. Currently, domestic and international nuclear radiation detectors mainly include scintillator detectors (such as NaI(T1) inorganic crystal scintillators) and semiconductor detectors (such as high-purity germanium HPGe semiconductor detectors and cadmium zinc telluride (CdZnTe) semiconductor detectors). Room-temperature cadmium zinc telluride (CZT) semiconductor nuclear radiation detectors are a new type of advanced detector developed after scintillator detectors. Room-temperature semiconductor nuclear radiation detectors are considered an ideal detector, possessing the high energy resolution of low-temperature semiconductor detectors and the high detection efficiency of scintillator crystal detectors, while also being small, lightweight, and portable. Therefore, CZT semiconductor nuclear radiation detectors were chosen as the detector for energy spectrum-based nuclear logging tools. The probe casing is made of stainless steel with excellent waterproof sealing to ensure normal operation under the high temperature and pressure conditions of logging. An automatic winch controls the movement of the downhole probe, enabling point-by-point or continuous measurement during logging, and transmits the depth value of the downhole probe to the embedded system control core. The energy spectrum acquisition circuit linearly amplifies, adjusts, and removes noise from the electrical pulse signal output by the CZT detector. It divides the range of the measured pulse signal into multiple pulse amplitude intervals, then counts the number of pulses in each interval to form a count distribution curve for each pulse amplitude. The energy spectrum acquisition circuit mainly consists of a linear amplifier, a peak detection circuit, a peak hold circuit, and a trigger ARM920T processor S3C2410A built-in A/D converter. Its circuit structure is shown in Figure 1. [b]3.2 Application of Embedded Systems in Energy Spectrum Nuclear Logging Tools 3.2.1 Embedded Hardware System[/b] The control core of the energy spectrum nuclear logging tool system, the ARM920T processor S3C2410A, is a high-end 32-bit low-power RISC microprocessor with a maximum operating frequency of 203MHz, independent 16KB instruction cache, and 16KB data cache. The storage system uses a combination of 2MB NOR Flash, 128MB NAND FLASH, and 64MB SDRAM as program execution and data storage space. Various corresponding peripheral interfaces are designed, mainly including an LCD interface, SPI keyboard interface, USB interface, Ethernet interface, RS232 interface, and multichannel analyzer MCA interface. A 5.4-inch true-color LCD display is used. Since the S3C2410A integrates an LCD controller, it can easily control various types of LCD displays. 3.2.2 Embedded Software System A bootloader program is written on the nuclear logging tool hardware platform to initialize the target board hardware, provide the operating system with information about the hardware resources on the board, and further load and boot the embedded Linux operating system. Because U-Boot has wide versatility, it was chosen to port U-Boot to this hardware platform. The porting of the Flash driver and SDRAM driver is crucial for the successful porting of U-Boot. Embedded Linux supports multiple architectures, has powerful network functionality, supports multiple file systems, and has rich peripheral drivers. In addition, Linux has a complete toolchain, making it easy for users to build their own embedded system development environment and cross-platform runtime environment. The Linux operating system kernel is customized and ported on the corresponding hardware platform, and the Linux-based YAFFS embedded file system is also ported. The root file system adopts the YAFFS file system, which features high speed and low memory consumption. It comes with its own NAND chip driver. YAFFS is a journal-structured embedded file system specifically designed for NAND flash memory and is suitable for high-capacity storage devices. 3.2.3 Design of the Monitoring Terminal Based on MiniGUI MiniGUI is a lightweight graphical user interface support system for real-time embedded systems, widely used in handheld information terminals, set-top boxes, industrial control systems and industrial instruments, portable multimedia players, query terminals, and other products and fields. The monitoring terminal of the spectral logging tool is developed based on the MiniGUI graphical interface library, realizing functions such as spectral data acquisition, spectral curve display, data file management, and spectral data analysis. The basic structure of the monitoring terminal of the spectral logging tool is shown in Figure 2. 3. Conclusion This paper focuses on the development trends of nuclear logging tools both domestically and internationally. Combining the characteristics of portable instruments in field operations and the development characteristics of embedded systems, it uses the high-end ARM920T processor S3C2410A as its core. An embedded Linux operating system, YAFFS file system, and MiniGUI graphical interface development library were ported to it. Bootloader system boot code was written, device drivers were written, and logging tool monitoring terminal software based on the Linux operating system and MiniGUI was developed. 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