The Lanzhou Heavy Ion Accelerator Cooling Storage Ring(HIRFL-CSR)is an ideal device for studying the decay of highly charged and short-lived isomers.In the lifetime measurement experiment of the short-lived highly charged ion 94mRu44+,we directly observed the decay of 94Ru from 8+isomer to the ground state,and identified 49 decay events in the ob-servation time window of(20 μs,180 μs).In order to identify more decay events,a new method based on amplitude of fre-quency spectrum was studied in this paper.Based on the simulation results,this new method can effectively identify decay events within(15 μs,185 μs).By applying the new identification method to the experimental data processing,54 decay events were identified within(15 μs,185 μs).Based on these 54 decay events,the lifetime of 94mRu44+in the laboratory frame was calculated to be 194(121)μs.The new lifetime result is within the error range of the previous result 218(148)μs.

为进一步明确月球表面湮灭辐射的主要来源和影响机理,构建了轨道γ能谱仪中湮灭辐射特征峰定量分析模型,采用GEANT4模拟不同能量质子轰击月岩诱发γ射线微分能谱,并以"嫦娥一号"高能粒子探测器(Chang'e-1 High-energy Particle Detector,CE1-HPD)数据作为输入项,计算了宇宙射线中4～400 MeV质子在月表5种典型岩石中诱发湮灭辐射的特征峰信息.在对"嫦娥一号"γ能谱仪(Chang'e-1 Gamma-ray Spectrometer,CE1-GRS)获取的0.511 MeV特征峰进行本底扣除和天然放射性核素影响剥离后,与4～400 MeV质子诱发湮灭辐射结果进行比较.研究结果表明:级联簇射产生湮灭辐射的概率与入射质子能量呈正相关,在4～400 MeV能量范围内,典型月岩的成分差异对诱发湮灭辐射的影响不明显.虽然该能量段质子的注量率较高,但由于其能量较低,无法有效地通过级联簇射形成正电子,最终导致湮灭辐射贡献率较低,仅为(1.97±0.66)×10-4.

该文以Unity3D为主要开发平台,在红沿河、海阳、昌江等中国大陆地区16个在运(建)核电厂区信息(行政区域、人口密度、路网建设等)的真实背景下,设计核事故后放射性核素(137Cs、131I、133Xe)在大气、近海迁移过程的可视化系统,将真实的厂址信息、气象条件、放射源项等与虚拟的核事故等级和核应急疏散相结合,对核事故后放射性物质环境迁移、公众所受大气浸没照射剂量评价等进行全景式呈现,使学生身临其境地参与放射性烟羽追踪、核事故应急撤离、大气浸没剂量评价等工程实践过程.

根据几种常用放射性核素的寿命计算方法,通过模拟数据研究了直接拟合法、对数时间法、极大似然法、观测时间受限时的极大似然法等四种寿命计算方法的适用范围。当观测时间不受限时,研究了在不同计数下寿命计算方法的适用范围。当观测时间受限时,研究了在不同观测时间窗口下寿命计算方法的适用范围。模拟中选用全剥离离子 94m Ru 44+ 作为目标核素,得到了不同计数及不同观测时间窗口下的寿命及其误差,并给出了四种方法的适用范围。 94m Ru 44+ 寿命的模拟结果与在兰州等时性质量谱仪上获得的实验结果在一倍标准偏差范围内一致,从而进一步验证了寿命计算方法的适用范围及模拟数据的可靠性。该模拟结果可为寿命测量实验设计提供理论依据和参考。

Isochronous mass spectrometry has been applied to 112Sn projectile fragments at the HIRFL-CSR facility in Lanzhou. To produce short-lived nuclei of interest, we used projectile fragmentation of 112Sn35+ primary beams in a ～10 mm thick 9Be production target. The fragments were selected and analyzed by RIBLL2 and injected into the experimental storage ring(CSRe) every 25 s. To measure revolution times of stored ions,we used a Time-Of-Flight detector installed in CSRe. A new particle identification method was developed to distinguish ions on the measured revolution time spectrum for each injection. Based on this method, the shifts of the revolution time due to instable dipole magnet fields can be corrected and the ground and isomeric states of 101In have been well-resolved. The measured excitation energy is consistent with the theoretical value in the error range of 112 keV. The lifetime of the isomeric states of 101In is more than 200 μs.

在OBE核心理念导向下,开展核环境学基础课程教学改革,改变传统的灌输式教学,实现研究性教学,更好地培养学生的独立思考、实践、探索能力和创新精神.在授课过程中更多地采取探索性、综合性的案例分析与实践设计项目,引入包括:"辐射环境监测(评价)报告分析""核动力系统运行辐射监测实践"和"辐射屏蔽设计"等环节,紧密联系工程实践要求,丰富教学内容和手段.完善多元化的成绩评定体系,促进毕业指标更好达成,推动核工程与核技术专业"国家级卓越工程师"课程教学方案的深化改革.

The decay of the fully stripped ion 94mRu44+ in the order of one hundred microseconds has been studied for the first time by using the Isochronous Mass Spectrometry (IMS) at the HIRFL-CSR facility in Lanzhou.94mRu44+ waS produced via projectile fragmentation of a 112Sn primary beam bombarding on a 9Be production target.After the in-flight separation with RIBLL2,the ions were injected into the experimental ring (CSRe) and then stored there.The revolution times of the stored ions were measured by a Time-of-Flight (TOF) detector.Due to the mass change of a 94mRu44+ ion caused by its de-excitation to the ground state,hence the revolution time change,the decay process of 94mRu44+ could be directly observed in the CSRe.The sensitive window for detection of the decay events and the measurement precision of the decay time have been determined in this work.At the same time,we measured the mass of short-lived 94mRu44+ with the half-life about one hundred microseconds,which is the shortest among nuclides that have been studied by using storage-ring mass-spectrometry.

Recent results and progress of mass measurements of neutron-rich nuclei utilizing Isochronous Mass Spectrometry (IMS) based on the HIRFL-CSR complex at Lanzhou are reported. The nuclei of interest were produced through projectile fragmentation of primary 86Kr ions at a realistic energy of 460.65 MeV/u. After in-flight separation by the fragment separator RIBLL2, the fragments were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of their revolution times. The re-determined masses were compared and evaluated with other mass measurements, and the impact of these evaluated masses on the shell evolution study is discussed.