硅探测器的数字化脉冲形状甄别

介绍了利用硅探测器的脉冲形状甄别进行粒子鉴别的原理。详细叙述了基于数字化方法的脉冲形状甄别的实现。采样频率和位数是数字化方法的两个重要参数。对于硅探测器信号，采用100 MS/s，12 bit的Digitizer可以满足脉冲形状甄别法对时间分辨的要求。同时对该方法粒子鉴别的特征和能量阈值做了简要的分析和对比。粒子背面入射硅探测器的所得的阈值低于正面入射的情况。例如对于氖周围的同位素，背面入射情况的阈值约为100 MeV，为正面入射情况下鉴别阈值的二分之一，相当与ΔE-E方法中ΔE探测器厚度约为60 μm情况下的阈值。最后定性讨论了硅探测器的电阻率不均匀性和沟道效应对粒子鉴别性能的影响。In this paper Pulse Shape Discrimination(PSD) for silicon detector has been briefly introduced. The emerging digital method successfully applied to detector signal processing makes digital PSD method one of the most promising particle identification methods. Sampling frequency and the number of bits are two key parameters of digital method. For silicon detector signal, adopting 100 Ms/s, 12 bit Digitizer can satisfy the time resolution requirement of PSD method. The identification characteristic and energy threshold of this method have been discussed and compared with both front injection and rear injection cases. Energy threshold with rear injection usually is much lower than that with front injection. For example, around for Neon isotope energy threshold with rear injection is about 100 MeV which is only half of the threshold with front injection, also equivalent to thickness of about 60 μm silicon detector threshold in ΔE-E method. At the end the impact of silicon detector's resistivity nonuniformity and channel effect on the identification capacity of PSD method has been discussed in detail.     

β-delayed neutron decay of 21N

The β-delayed neutron and γ spectra of neutron-rich nucleus ²¹N using β-γ and β-n coincidence measurements were presented in this paper. Thirteen new neutron groups ranging from 0.28 MeV to 4.98 MeV and with a total branching ratio 88.7±4.2% were observed. One γ transition among the excited states of ²¹O, and four γ transitions among the excited states of ²⁰O were identified in the β decay chain of ²¹N. The ungated half-life of 83.8±2.1 ms was also determined for ²¹N.     

β缓发中子探测阵列的性能优化及测试

讲述了用于β缓发中子发射测量的中子探测阵列的性能优化过程及测试结果. 对中子探测器包装用的几种反射材料、光导和光电倍增管之间用的几种耦合材料行了系统的对比和研究. 为了优化电子学和实时监测整个探测阵列的工作状态, 引入了LED光纤刻度监测系统.     

25MeV／u^6He十^9Be破裂反应的α碎片发射

测量了在25MeV／u^6He轰击^9Be靶的破裂反应产生的α碎片双微分截面及角分布，并在Ser—ber模型的框架下计算了在破裂反应中衍射破裂与擦去过程的贡献，并对结果进行了讨论．结果表明基于包含衍射破裂和擦去过程的Serber模型可以对^6He的直接反应进行较好地描述，擦去过程的贡献远大于衍射破裂的贡献．相对于^6Li而言，^6He较大的去2n微分截面源于它的弱束缚特性。     

17N+197Au反应中碎片与中子的符合测量

在3?3?.4MeV/u ¹⁷N束轰击¹⁹⁷Au靶产生的反应中,利用放置于不同角度组合的17个中子探测器(4°—83°)和14个半导体望远镜(2.3°—9.0°)对反应产物碎片与中子进行了符合测量.经对所得实验角分布积分得到Z=3—6元素的同位素产额分布.在参加者-旁观者模型框架下,采用¹⁷N原子核内部的不同密度分布计算了同位素产额分布并与实验数据做比较.     

能量修正的Glauber模型对中能反应总截面的影响

叙述了对Glauber模型中的透射系数进行半经验的能量修正,并利用该修正模型计算了^12—14C,⁶Li,⁷Be,⁸B+¹²C和⁶Li,⁷Be,⁸B+⁹Be以及²⁰Ne+¹²C,¹²C+²⁷Al等系统的激发函数(能区范围10—1000MeV/u),经与实验值比较,能量修正的Glauber理论计算值能够很好地描述中能条件下的反应总截面实验测量值.     

20 Na的β+延发α粒子测量

利用兰州放射性次级束流线提供的^20Na束流,通过^20Na→^β^ ^20Ne*→^16O α过程,测量了^20Na的衰变半衰期T1／2及衰变α粒子能谱。结果表明,除了Ed≥2.688MeV的9条较高激发能级的衰变α粒子外,实验中还观察到衰变能量Ed为0.890和1.054MeV,1.991MeV,2.424和2.457MeV的^20Ne低激发能级的3条α谱线。     

Structure change of 156Yb at high-spin states

High-spin states of ¹⁵⁶Yb have been studied via the ¹⁴⁴Sm(¹⁶O,4n)¹⁵⁶Yb fusion-evaporation reaction at beam energy 102~MeV. The positive-parity yrast band and negative-parity cascade have been extended up to higher-spin states, respectively. The characteristics of the negative-parity sequence above the 25^－ state may related to the excitation from the nucleon in the Z=64, N=82 core. The E-GOS curve for the positive-parity yrast sequence in ¹⁵⁶Yb indicate that this nucleus may undergo an evolution from quasivibrational to quasirotational structure with increasing angular momentum. The Cranked Woods-Saxon-Strutinsky calculations by means of Total-Routhian-Surface (TRS) methods has been made to understand this structure change.     

23Al的β+延发质子测量

利用ＴＯＦ－ Ｅ和０°注入探测器的方法,鉴别并测量了２３Ａｌβ＋延发质子衰变能谱,通过精密脉冲发生器和计数器测得２３Ａｌ的半衰期 Ｔ１／２＝（４７６±４５）ｍｓ．实验中重现了能量为０．２１６,０．２７８,０．４３８,０．４７９ＭｅＶ的低能衰变质子．另外,还观察到了一个新的β＋延发衰变能级 Ｅｘ＝ ８．９１６ＭｅＶ,并给出了它们的相对强度．     

20Na的β+延发α粒子测量

利用兰州放射性次级束流线提供的²⁰Na束流,通过²⁰Naβ^{+ 20}Ne→¹⁶O+α过程,测量了²⁰Na的衰变半衰期T_1/2及衰变α粒子能谱.结果表明,除了E_d≥2.688MeV的9条较高激发能级的衰变α粒子外,实验中还观察到衰变能量E_d为0.890和1.054MeV,1.991MeV,2.424和2.457MeV的²⁰Ne低激发能级的3条α谱线.