| With the development of nuclear technology and radiation technology rapidly,the neutron technology of the civil passive nuclear machinery was extensively applied in various fields such as neutron log, log induced by neutron, neutron photography, neutron carcinogenesis, neutron activation analysis and so on, which bring us enormous benefits,at the same time, lead to radiation accidents with concern for casualties. When people are exposed by neutron, different forms of energy of the neutron are interacted with the element of body tissues, in this process, generates secondary electronics with a specific energy could induced ionization and excitation,which are even more serious than gamma ray, because it could make the body injured or cause bone marrow suppression, hemorrhage, contagion, weakened immune system and so on, which increase the risk of early death, so the consequences is too serious. This paper aims to integrate advanced nuclear detection, circuit design, acquisition of signal and information processing, research and develop a portable, high-precision blood neutron irradiation dose detector.Neutron detection is usually with the help of the charged particle generated with the interaction of neutron with target. Some nuclides turn into radio nuclides by neutron irradiation, we can calculate the dose of neutron by measurement the radioactivity of these radio nuclides. In the accident of nuclear or neutron irradiation, estimation of neutron irradiation dose is difficult, when people are irradiated by neutron, activation reaction take place, the products of the activation reaction are radioactive, through making the qualitative and quantitative measurement of the radioactive of the product can calculate the dose of neutron of the patient. At the present time, the primary method is measureing the activity of radionuclide 24Na, which is generated by 23Na capture of neutron, in the blood of the human body. The instrument according to the principles of gamma ray detection, making the qualitative and quantitative measurement of gamma ray which is generated by 24Na decays that in the blood of the patient who is irradiated by neutron, and then according to the activity of gamma ray to calculate the neutron dose of the patient. This instrument chooses NaI (Tl) detector, which contains preamplifier and high voltage module, is shielded in low-background measurement set. Hardware design take the embedded Single-Chip computer as the control platform, consisted of signal acquisition module and master processor module, signal acquisition module amplify the weak signal from preamplifier, through reshaping and filtering of the signal, and then catching and keeping of the pulse peak, input the signal to the host module, the high-speed ADC of the micro-controller convert analog the voltage pulse signal in to digital signal and then save it. The micro-controller can analyze the data to achieve the function of Multi-Channel Amplitude Analyzer. The result is displayed as spectral line on LCD or uploads to PC by USB. Software design can be divided into two types, signal acquisition module software and master processor module software. Signal acquisition module software is mainly for timing measurement, data acquisition in interrupt time, formation of spectral line, saving the data in local storage, data transmission to master processor module by serial port and so on. Master processor module software is mainly for interaction between man and machine, which contain menu, spectral line display, windows of parameter setting and master processor module controlling, which contain spectral line transmission by serial port,starting and stopping of the measurement, setting the measuring time and so on.Through the system's software and hardware design, On the whole the instrument has basically access to measure the activity of 24Na in the blood of the patient who is irradiated by neutron,and then calculate the neutron dose. In addition, it is small in size, light in weight, low background, low power consumption it also has good human-computer interface and high precision. |
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