共查询到20条相似文献,搜索用时 15 毫秒
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在北京正负电子对撞机的J/ψ和Ds能区,选择了辐射巴巴事例,并以此来研究北京谱仪的桶部簇射计数器能量响应特性.在消除了由于电子和辐射光子在桶部簇射计数器中沉积能量区域重叠的影响后,正确地得到了桶部簇射计数器在电子和光子动量小于2GeV以下的能量响应,表明在所研究能区,桶部簇射计数器的能量响应线性很好.对桶部簇射计数器微小的非线性进行修正后,重建的π0不变质量谱得到改善. 相似文献
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北京谱仪Ⅱ经过1995年升级后,其TOF系统对Bhabha事例的电子时间分辨率是180ps[1],相对北京谱仪Ⅰ的330ps有了很大的改进.随着硬件性能的提高,其相应的软件系统(包括刻度,重建),特别是蒙特卡罗模拟,也必须作相应的改进.本文利用北京谱仪Ⅱ已获取的5000万J/ψ数据,对飞行时间计数器的时间分辨率进行认真的研究,通过比较现有的模拟数据和真实数据的结果,对飞行时间计数器的模拟进行改进,最后给出改进后的模拟数据和真实数据的比较结果,两者符合得很好. 相似文献
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在日本KEK的12GeV质子同步加速器上, 用动量为0.2GeV/c至2.0GeV/c的电子和π介子束流对BES桶部簇射计数器模型进行了测试, 本文报告数据分析的初步结果. 测试了四种混合气体下模型的性能, 测试结果表明, 用自猝灭流光管作为取样型电磁簇射计数器的取样方式, 在BEPC对撞机的能量范围内是可行的. 文章同时还报告了基于取样保持电路和BADC的120路在线数据获取系统在连续两个月束流测试中的性能. 相似文献
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简单介绍了重离子治癌的原理, 叙述了一种用于重离子治癌的大面积平行板雪崩计数器, 它主要由入射窗、 x位置栅极、 中心阳极、 y位置栅极和出射窗组成. 使用C3F8气体, 气压700 Pa, 阳极电压为700 V, 两阴极接地, 电子学成形时间常数为2 μs, 测试得到的位置分辨修正后为0.54 mm(FWHM). 通过与国内外同类装置比较, 认为这一分辨已经满足了重离子治癌装置的要求. he principle of the heavy ion therapy is introduced in this article. In order to precisely determine the irradiation profiles and positions of scanned heavy ion beams, we developed a large area parallel plate avalanche counter(PPAC). The detector consists of one anode, two cathodes and two windows with 250 mm×250 mm active area . It was measured at an anode voltage of 700 V and with flowing C3F8 gas at the pressure of 700 Pa. A position resolution of 0.54 mm by correction was obtained with an α source. As compared with the similar devices, we consider the position resolution of the PPAC can satisfy the requirement of the facility of heavy ion therapy. 相似文献
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原子团簇的激发温度可由反应产物(出射电子或碎片)的初始平动能这一可观测量间接获得,为了提高原子团簇激发温度的测量精度,设计并搭建了一套具有高动能分辨的离子速度成像谱仪。本谱仪的高动能分辨性能首先借助Simion8.0软件优化静电透镜和分子束限束装置的几何结构来实现,然后通过理论模拟证明本套谱仪具有预期好的动能分辨能力。设备搭建完成后,研究了C60分子束在纳秒激光场中发生的延迟电离过程,获得了C60+离子随延迟时间增加而逐渐变窄的二维时间切片图像。分析表明,激光脉冲产生的多个C60+离子间的库仑耦合作用将会扩展二维切片图像的横向分布,提取库仑耦合作用对C60+离子初始平动能的影响,并通过分析C60+离子间的库仑耦合随延迟时间增加而逐渐变弱的定量依赖关系,证实了本套谱仪具有了设计预期的高动能分辨能力。这一工作为下一步基于离子速度成像技术细致研究分子热力学的相关课题提供技术参考。Excitation temperature of fragmenting atomic clusters can been extracted from the initial kinetic energies of ionic products. To improve the accuracy of the temperature measurements, we have designed an ionic velocity map imaging spectrometer with high kinetic energy resolution. Firstly, based on the simulations using Simion8.0 software, the high resolution is obtained by adjusting the structure of the electrostatic lenses and collimation of molecular beam. According to theoretical analysis, it is proved that the spectrometer has a well defined kinetic energy resolution. Then, we have studied the delay ionization processes of C60 induced by nanosecond laser. A series of narrowed two-dimensional time-sliced velocity images of the C60+ with increasing the delayed time were recorded. Analysis revealed that Coulomb force between C60+ clusters in same laser shots will broadening the transverse distribution of 2D image. Considering the influence of Coulomb force on initial kinetic energy of C60+ clusters, the high resolution has been proved by analysing the negative relationship between Coulomb force and delayed time. It indicates that the establishment of the spectrometer builds up a good basis for next experiments on the studies for molecular thermodynamics in atomic clusters. 相似文献