本文關鍵詞： 中能重離子核反應 重構的初始碎片多重性 對稱能系數(shù) 密度 溫度　出處：《中國科學院研究生院(近代物理研究所)》2016年博士論文　論文類型：學位論文

【摘要】：核物質狀態(tài)方程是目前國際核物理研究的熱點之一。其中非對稱核物質狀態(tài)方程,特別是對稱能的研究更是備受青睞。本論文首次從實驗上對40MeV/nucleon的64Zn+112Sn反應中初始碎片的多重性進行了重構,并結合反對稱分子動力學模型(AMD),利用重構的初始碎片多重性研究了反應中發(fā)射源的性質。同時提出了提取反應中發(fā)射源溫度、密度和對稱能系數(shù)的一新方法。實驗上利用動力學聚焦原理來確定與探測到的次級中等質量碎片相關聯(lián)的輕碎片多重性。利用這些數(shù)據(jù),采用蒙特卡羅方法對反應中初始碎片的激發(fā)能和同位素多重性進行重構。重構的初始碎片激發(fā)能在1到4 MeV/nucleon之間時,對于給定的電荷數(shù)Z,激發(fā)能隨碎片質量數(shù)A的增大有明顯的下降趨勢,并且與AMD以及統(tǒng)計多重碎裂模型(SMM)計算所得的激發(fā)能有較大不同。而重構的初始碎片的同位素多重性分布與AMD計算所得的初始碎片的同位素多重性分布符合很好。利用重構的初始碎片多重性,本論文研究了碎片質量的指數(shù)律分布以及反應中發(fā)射源的性質。重構的初始碎片質量數(shù)A≥15的同位素質量分布很好的滿足指數(shù)律A-2.3分布,而較輕的碎片則明顯低于該指數(shù)律分布。根據(jù)修正的Fisher模型,提取了反應中庫侖能系數(shù)與溫度的比值ac/T和對稱能系數(shù)與溫度的比值asym/T隨碎片質量數(shù)A的變化關系。同時比較了所提取的asym/T的值和AMD采用不同密度相關對稱能的Gogny相互作用計算所得的初始碎片中提取的asym/T的值。AMD計算中提取的asym/T的值與系統(tǒng)在碎片產生時的特定密度下對稱能的值有明顯的相關性。根據(jù)這一相關性,我們確定了反應中發(fā)射源的密度為ρ/ρ0=0.63±0.03。利用該密度,提取了反應中發(fā)射源的對稱能系數(shù)和溫度分別為asym=24.7±3.4 MeV和T=4.9±0.2 MeV。利用該自洽法我們研究了三個不同反應系統(tǒng)的發(fā)射源溫度、密度,并且將發(fā)射源的密度與反應系統(tǒng)在演化中所達到的最大密度進行比較,得出在AMD中,中等質量碎片是產生于溫度T~6 MeV、密度ρ/ρ0=0.67的統(tǒng)計平衡的凍結體積。這些研究對我們了解核物質狀態(tài)方程有重要參考意義。
[Abstract]:The equation of state of nuclear matter is one of the hotspots in the international nuclear physics research at present. Especially, the study of symmetry energy is very popular. In this thesis, the multiplicity of initial fragments in the 40MeV / nucleon 64Zn112Sn reaction was reconstructed for the first time. Combining with the antisymmetric molecular dynamics model, the properties of the emission source in the reaction were studied by using the multiplicity of the reconstructed initial fragments, and the temperature of the emission source in the extraction reaction was proposed. A new method of density and symmetric energy coefficients-determination of the multiplicity of light debris associated with detected secondary intermediate-mass debris experimentally using the kinetic focusing principle. Monte-Carlo method is used to reconstruct the excitation energy and isotopic multiplicity of the initial fragments in the reaction. The reconstructed initial fragment excitation energy is between 1 MeV/nucleon and 4 MeV/nucleon. For a given charge number Z, the excitation energy tends to decrease with the increase of fragment mass number A. The calculated excitation energies of the reconstructed fragments are quite different from those calculated by AMD and the statistical multiple fragmentation model. The isotopic multiplicity distribution of the reconstructed initial fragments is in good agreement with the isotopic multiplicity distribution of the initial fragments calculated by AMD. Taking advantage of the multiplicity of initial fragments of reconstruction, In this paper, we study the exponential law distribution of debris mass and the properties of emission source in the reaction. The reconstructed isotopic mass distribution of the initial fragment mass number A 鈮，

本文編號：1550449