【作者】 张登高；

【导师】 李加兴；

【作者基本信息】 西南大学 ， 理论物理， 2010， 硕士

【摘要】 在RIBLL所有的离子鉴别探测器中,飞行时间探测器对于鉴别和分离RIB起着至关重要的作用。因此,很有必要对飞行时间探测器的性能进行研究,以便找出提高探测器性能的合理方案。本文的主要内容就是对RIBLL中飞行时间探测器的性能进行模拟研究。在本工作中,我们利用GEANT4这一蒙特卡洛模拟软件,首先构造了和实验一致的飞行时间探测器装置,定义了粒子源和相应的物理过程。在物理过程中,入射粒子与闪烁体之间主要是低能电磁相互作用过程,还涉及到光子吸收过程、边界过程和光子的传输过程。其次,对该探测器的性能做了比较深入细致的模拟研究。研究结果表明,光子总的收集效率与粒子在闪烁体上的入射位置有关；时间分辨与入射粒子的入射位置、种类、能量以及铝反射层的反射率有关。选用了入射束斑均相同的不同的重离子作离子源,并分别进行了模拟实验,得到了各自的时间分辨。粒子的入射位置在闪烁体的中心位置附近时,光子总的收集效率较好；入射点在中心稍微靠下的位置时探测器的时间分辨最好；铝反射面的反射系数较低时,经过一次反射到达光阴极的光子数目较多,但经二次反射到达光阴极的光子数目较少,时间分辨较好；入射粒子的能量对时间分辨的影响比较大,随着能量的增大时间分辨逐渐变差。最后,通过进一步地分析和讨论,并结合本模拟实验的研究结果对飞行时间探测器提出了一些建议和改进方案。更多还原

【Abstract】 Time of flight detector plays an essential role for the identification and isolation of radioactive ion beam in all the particle identification detectors in RIBLL. Hence, it is necessary to study the TOF detector performance so as to find a reasonable solution to improve it. In this paper, the performance of TOF in RIBLL was simulated and then studied.Firstly, we constructed TOF detector consistently with experimental set up using Monte Carlo Kit GEANT4, defined the ion source and all the corresponding physical process. Of all the physical process, low energy electromagnetic processes is the main interaction between incident particle and scintillator, while photon absorption process,boundary process and photon transmission are also involved.Secondly, the detector performance is studied intensively. The results show that total photon collection efficiency is associated with the particle incident location on scintillator, time resolution is related to the kinds of incident particle, incident position, energy and reflectivity of Aluminum reflector. Different heavy ions were selected with same size of beam spots, and simulated, then time resolutions was achieved respectively. The total photon collection efficiency is best when incident particle location is of the center of scintillator. When the incident point is a litter lower to the center, the time resolution is best. If Aluminum reflectance is smaller, the number of photons with only one reflection arriving at the photocathode will be larger, the number of photons with 2 reflections will be smaller, which causes a better time resolution. The energy of the incident particle influence the time resolution greatly. The time resolution became worse following the increase of incident energy.Finally, combining the results of the simulation and further analysis, discussion, we put forward some suggestions and improvements to the TOF detector.更多还原