【摘要】：在熱中子活化中,活化能譜的探測(cè)和能譜分析非常重要。但是統(tǒng)計(jì)漲落和本底會(huì)對(duì)中子活化的γ能譜分析造成影響。所以,減少統(tǒng)計(jì)漲落和本底的影響有利于提高中子活化能譜分析的準(zhǔn)確性。能譜探測(cè)方法的不同會(huì)對(duì)獲取的能譜造成很大的影響,采用合適的探測(cè)技術(shù)有利于獲取自己需要的活化能譜。目前符合測(cè)量法在核物理實(shí)驗(yàn)中已經(jīng)成為多參數(shù)測(cè)量的重要實(shí)驗(yàn)方法。熱中子活化會(huì)產(chǎn)生放射性核素,放射性核素衰變產(chǎn)生的γ射線存在時(shí)間上的關(guān)聯(lián)關(guān)系,是實(shí)現(xiàn)符合測(cè)量的重要前提。本文的工作就是利用符合測(cè)量技術(shù)對(duì)熱中子活化能譜進(jìn)行全能峰篩選。首先利用熱中子轟擊材料產(chǎn)生放射性核素,然后利用探測(cè)器對(duì)活化能譜進(jìn)行探測(cè)。具體的工作內(nèi)容有:(1)利用Geant4軟件對(duì)衰變核素產(chǎn)生的特征γ射線進(jìn)行記錄,將獲得的特征射線的能量和強(qiáng)度與NNDC和PGAA數(shù)據(jù)庫(kù)進(jìn)行對(duì)比;(2)利用NaI(Tl)探測(cè)器對(duì)中子活化能譜進(jìn)行探測(cè),并運(yùn)用傅里葉變換法對(duì)中子活化能譜進(jìn)行處理;(3)利用γ-γ單峰級(jí)聯(lián)符合法對(duì)中子活化能譜進(jìn)行全能峰篩選,通過(guò)單特征峰篩選出級(jí)聯(lián)的射線,從而實(shí)現(xiàn)能譜簡(jiǎn)化,凸顯核素特征峰。(4)γ-γ雙峰求和符合選擇簡(jiǎn)化能譜,通過(guò)將級(jí)聯(lián)射線求和的能量作為門(mén)信號(hào)進(jìn)行特征峰選擇,達(dá)到去除本底,凸顯全能峰的目的。符合測(cè)量技術(shù)能夠很好的將能譜簡(jiǎn)化,降低統(tǒng)計(jì)漲落和本底計(jì)數(shù)的影響,凸顯全能峰,有利于提高中子活化能譜分析的準(zhǔn)確性。
[Abstract]:The detection and analysis of activation energy spectrum are very important in thermal neutron activation. However, statistical fluctuations and background will have an effect on the neutron activated 緯-ray spectrum analysis. Therefore, reducing the effect of statistical fluctuations and background is helpful to improve the accuracy of neutron activation energy spectrum analysis. The difference of energy spectrum detection method will have a great influence on the energy spectrum obtained, and it is advantageous to obtain the activation energy spectrum by adopting the appropriate detection technology. At present, coincidence measurement has become an important experimental method in nuclear physics experiments. Radionuclides can be produced by thermal neutron activation, and the correlation of the existence time of 緯 -rays produced by radionuclides decay is an important prerequisite for the realization of coincidence measurement. The work of this paper is to screen the thermal neutron activation energy spectrum by coincidence measurement. First, radionuclides are produced by bombarding materials with thermal neutrons, and then the activation energy spectra are detected by detectors. The specific contents of the work are as follows: (1) the characteristic 緯 rays produced by decay nuclides are recorded by Geant4 software, and the energy and intensity of the obtained characteristic rays are compared with those of NNDC and PGAA databases; (2) the neutron activation energy spectrum is detected by NaI (Tl) detector. The neutron activation energy spectrum is processed by Fourier transform method. (3) the 緯-緯 single peak concatenated coincidence method is used to screen the universal peak of the neutron activation energy spectrum, and the single characteristic peak is used to screen out the cascaded rays, so as to simplify the energy spectrum. (4) the summation of 緯-緯 double peaks coincides with the selection of simplified energy spectrum. By using the energy of cascade ray summation as the gate signal, the characteristic peak is selected to remove the background and highlight the omnipotent peak. The coincidence measurement technique can simplify the energy spectrum, reduce the influence of statistical fluctuation and background counting, highlight the omnipotent peak, and improve the accuracy of neutron activation energy spectrum analysis.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：O571.5

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本文編號(hào)：2202202