Abstract
A low-cost handheld nuclear spectrometer that combines personal digital assistant (PDA) with recent breakthroughs in radiation measurement technology of energy spectrum analyzing on PC is being designed, built and tested. We design a portable radiation spectrometer with acquisition and spectrum analyzing system, PDA SPECTROMETER, which can be used in anywhere and any time. For some Customs, nuclear power plant inspectors, emergency response and science researches, they can be used to detect outdoors and identify nuclear material in a moment. They can also be used as a “smart” radiation alarm that can be told the difference between a nuclear material and a person with a recent radiological medical treatment by PDA. It can be used in any field measurement application requiring dose and count rate measurements, nuclide identification and activity measurements, and spectrum acquisition and analysis. These modes of operation are easily-selectable with one touch. The front-lighted, crisp color display and touching panel allow quick access to all modes. Switch from one mode to another with touching the button on the PDA screen. When not in use by the user, the instrument can be set constantly monitors the ambient radiation field and continuously detects with a central processing system on PDA in real time. This architecture as well as the data acquisition block has been optimized to accommodate high throughput pulse rates in Nuclear Spectroscopy applications. However, its generality allows for many other signal processing, control and communication applications to be easily implemented using this system. Due to the small size, high programming, friendly user interface and I/O capabilities of PDA, the proposed system can be used to acquire the radiation signals, display and analyze the spectrum. Besides, it can transmit these kinds of signal and important information through internet by Ethernet or mobile phone. PDA has sufficient memory to save the acquired data and allow for the configuration of setup parameters. Furthermore analyzing application, PDA can also connects to any host computer through standard USB, IrDA or RS-232 serial interfaces and being also prepared to interface a GPS unit . For the moment, we use PDA SPECTROMETER to connect with the Nuclear Instrument Module (NIM) and test it’s function and performance. The NIM includes a basic front-end pre-amplifier, a high voltage supply, a analog to digital converter. The growing of the radiation spectrum can be easily observed on site through PDA’s colorful graphic display, save the acquired data and allow for the configuration of setup parameters. NIM connects to PDA and transmits data through RS-232 serial interfaces circuit that we implement by CPLD(Complex Programmable Logic Design). Software application programs in the PDA and hardware design on the CPLD are presented. In order to verify the system function, two experiments were performed. The first experiment is to measure the spectrum of different isotopes and compare the errors of result between PC and PDA. The second experiment is to evaluate the data transmission rate caused different nuclear event activity through RS-232 serial interface. After experiments, we found the limitation of the performance of current PDA, it is hard to acquire, process and record signals simultaneously.