Study On Optimization Design Of Detection Efficiency Of Nose Swab Measurement System

In the case of nuclear radiological emergency, how to classify large scale of individuals those who may be polluted by radioactive nuclide in the accident scene quickly is very important to their lives. It is significant to social’s stability and national security to take advantage of medical resources effectively.The radioactive aerosols breathed by human body are firstly deposited in the human respiratory system. And it will be gradually transferred to other tissues or organs. The absorbed radionuclide will have a long negative effect to the human body, and finally may lead to tissue damage or cause cancer. Nuclides with a, such as241Am,239Pu,235U,238U,etc. Although the detect technology to internal pollution can be directly measured by using a low energy ray such as X or y in a suitable way of vitro measurement. This method has strict requirements for the environmental background and detection efficiency calibration. Currently, only a few laboratories can do these experiments, the analysis of biological samples usually have the performance of chemical specificity. And the process will take a long time (a couple of days to weeks). The results can’t be given soon, and therefore it is hard to obtain the same sample. How to detect the inhaled pollution of alpha radioactivity by a quick and accurate way is a difficult problem in medical rescue.Our research groups have surveyed the background over the world, supported by Ministry of science and technology in the aspect of major instrument special. Inner contamination of Alpha radioactive of nasal swab detect subsystem, we developed a set of equipment for Inner contamination of Alpha radioactive of nasal swab detect subsystem which based on Au-Si surface barrier detection. This system can estimate the internal dose of human body which was polluted in the case of nuclear radiological emergency.According to the classified standards of rescue scene medical diagnostic dose, individuals polluted by a inner contaminate can be classified, and the follow-up medical treatments will be guided. But how to improve the detection efficiency of nasal swab alpha pollution detection system, at present, although some scholars have done some experiment researches on the influence factors of distance and vacuum degree, they did not work deeply on other related factors which may influence detection efficiency in the whole system.This paper mainly focus on four factors that may affect the efficiency of detection such as pressure, field strength, detection geometry and air humidity, by the model of Geant4, the effects of single and multi-factor were obtained. Finally, by collecting analog data, establishing an equation model of PLSR, and getting the weight efficiency of these four factors, the Characteristic factor which may affect the performance of instrument was found out, and also obtained an optimal condition for detecting instrument, and an experience for the design of these similar systems were acquired.The main research contents and achievements of the thesis are as follows:1) Simulated the range of different pressures, a particle with different energies in room temperature.This program used Monte Carlo software Geant4to simulate the range of a particles under different pressures, different energy in room temperature and different pressure, and constructed a fitting formula which is absolutely proportional to energy E1.73, and inversely proportional to pressure P, and provided reference data for the following research works.2) Carried out the research on these impact factors systematicallyThis program did a study on simulations which are related to the detection efficiency of this system, by the simulation experiments, the influence factors of system detection efficiency were obtained.3) The influence characteristics study on detection efficiency with single factor and two factorsThis program researched the influence characteristics of single factor and two factors interacted to detection efficiency, and then adopted a reasonable mathematical fitting method, built up the characteristic equation among these four factors and detection efficiency.4) The creation of PLSR of detection efficiencyBased on the simulation studied by the former work, these factors influence were treated as several separated factor, and then a math model of PLSR was obtained, according to PLSR theory, we summarized the best explanatory variables. The results showed that the field intensity factors play a leading role in the regression equation as well as the pressure and distance.The main innovations of his paper are two points as following:1) We studied the four factors such as Measurement of the pressure in the cabin, the electric field intensity, detection geometry and air relative humidity which may effected detection efficiency of the instrument in a way of single factor and multi-factors, and then built up mathematical equation corresponding.2) This paper put forward a method of PLSR, and found out the contribution weight relationship among these four factors, and then obtained the optimal conditions for the detecting instrument.This paper is based on Monte Carlo theory and alpha particle transport theory, and by doing a lot of simulating experiments, we obtained a lot of valuable data, and then we put forward a method of PLSR to establish the relationship among influence factors and the detection efficiency. And then we obtained the optimal conditions for the detecting instrument and provided a more detailed parameter for radioactivity inner contaminated technique and also for the design and measurement field in our country.