新核素65Se半衰期的首次实验测定

根据⁴⁰Ca(²⁸Si,3n)反应中观测到的⁶⁵Seβ延迟质子衰变实验数据,拟合计算粒子望远镜对运动放射源的绝对探测效率,精确测定了⁶⁵Se的半衰期为9.6ms,其β延迟质子能量为3.70±0.08MeV,由此修订了⁶⁵Se的部分衰变纲图.     

对69Krβ延迟质子衰变的观察

通过对³²S+Ca反应中衰变质子谱的观测,发现了一组新的质子谱线,其能量为(4.07±0.05)MeV,对应的衰期为(32±10)ms,经反应道分析及与理论预言比较,确定该质子活性来源于⁴⁰Ca(³²S,3n)反应产生的⁶⁹Kr的β延迟质子衰变,它相应于由⁶⁹Br中的T=3/2同位旋相似态到⁶⁸Se基态的质子跃迁.基于测量结果与库仑位移能计算,得到⁶⁹Kr的质量剩余为(－32.15±0.30)MeV,并提出了⁶⁹Kr的部分衰变纲图.     

对质子滴线核19Na的β延迟质子衰变的首次观察

由²⁰Ne(P,2n)¹⁹Na反应,对质子滴线核¹⁹Na进行了研究,实验在中国科学院高能物理研究所质子直线加速器上进行,首次观察到了¹⁹Na的β延迟质子衰变,测定其质子能量为1.10±0.08MeV,半衰期为47±20ms,它相应于¹⁹Na基态到¹⁹Ne的7.62MeV、T=3/2同位旋相似态的超允许β跃迁和由此态到¹⁸F基态的级联质子衰变.     

A simulation study of a dual-plate in-room PET system for dose verification in carbon ion therapy

During carbon ion therapy, lots of positron emitters such as 11C, 15O, 11C are generated in irradiated tissues by nuclear reactions, and can be used to track the carbon beam in the tissue by a positron emission tomography （PET） scanner. In this study, an dual-plate in-room PET scanner has been designed and evaluated based on the GATE simulation platform to monitor patient dose in carbon ion therapy. The dual-plate PET is designed to avoid interference with the carbon beamline and with patient positioning. Its performance was compared with that of four-head and full-ring PET scanners. The dual-plate, four-head and full-ring PET scanners consisted of 30, 60, 60 detector modules, respectively, with a 36 cm distance measurements. Each detector module consisted of a between directly opposite detector modules for dose deposition 24~24 array of 2 mm×2 mm×18 mm LYSO pixels coupled to a Hamamatsu H8500 PMT. To estimate the production yield of positron emitters, a 10 cm×15 cm×15 cm cuboid PMMA phantom was irradiated with 172, 200, 250 MeV/u 12C beams. 3D images of the activity distribution measured by the three types of scanner are produced by an iterative reconstruction algorithm. By comparing the longitudinal profile of positron emitters along the carbon beam path, it is indicated that use of the dual-plate PET scanner is feasible for monitoring the dose distribution in carbon ion therapy.     

RFQ1L系统压升率的理论与实验研究

简单阐述了RFQ冷却聚束器对缓冲气体的要求, 从理论和实验两方面详细研究了RFQ1L系统的压升率。 研究表明, RFQ1L系统压升率的主要来源是真空室内材料表面的出气, 整个系统的压升率实测为（0.04±0.02） Pa/h。     

Optimal design of a 7 T highly homogeneous superconducting magnet for a Penning trap

A Penning trap system called Lanzhou Penning Trap（LPT） is now being developed for precise mass measurements at the Institute of Modern Physics（IMP）.One of the key components is a 7 T actively shielded superconducting magnet with a clear warm bore of 156 mm.The required field homogeneity is 3 × 10-7 over two 1 cubic centimeter volumes lying 220 mm apart along the magnet axis.We introduce a two-step method which combines linear programming and a nonlinear optimization algorithm for designing the multi-section superconducting magnet.This method is fast and flexible for handling arbitrary shaped homogeneous volumes and coils.With the help of this method an optimal design for the LPT superconducting magnet has been obtained.