α-decay study of 218Ac and 221Th in 40Ar+186W reaction

In this study,²¹⁸Ac and ²²¹Th nuclides were produced via the heavy-ion induced fusion evaporation reaction ⁴⁰Ar+¹⁸⁶W.Their decay properties were studied with the help of the gas-filled recoil spectrometer SHANS and a digital data acquisition system.The cross section ratio between ²²²Pa and ²¹⁸Ac was extracted experimentally,withmeasured value 0.69(9).Two new possible α decay branches to ²²¹Th are suggested.The valence neutron configurations for the daughter ²¹⁷Ra are discussed in terms of the hindrance factors.     

Simulation of the Lanzhou Penning Trap LPT

The LPT (Lanzhou Penning Trap) is under construction and its task is to perform direct mass measurement of fusion-evaporation residues and if possible for heavy isotopes. Detailed simulations have been done for a good understanding to the ion’s movement and mechanics in the trap. The optimization of the LPT is also performed based on the simulation. With a scale of 0.5 mm per grid used in the simulation and many other limitations a highest mass resolution has been achieved to be 1.9×10-5. An unexpected behaviour in the simulation related to magnetron motion has been found.     

Alpha Decay of the Neutron-deficient Isotopes 215,216U

The most neutron-deficient isotopes 215;216U were produced in the complete-fusion reaction 180W(40Ar, 4-5n)215,216U. Evaporation residues recoiled from the target were separated in-flight from the primary beam by the gas-filled recoil separator SHANS and subsequently identified on the basis of correlated -decay chains. Two -decaying states were identified in 216U, one for the ground state and the other for the isomeric state with 8+(h9=2f7=2) configuration. The -decay properties for 215;216U and the systematics of 8+ isomeric state in N =124,126 isotones were investigated.     

Fine structure ofαdecay in222Pa

With the help of the gas-filled recoil spectrometer SHANS and a digital data acquisition system,the fine structure of the α decay for²²²Pa was studied.The nuclides were produced through the 1p3n evaporation channel via the heavy-ion induced fusion evaporation reaction ⁴⁰Ar+¹⁸⁶W.Based on the ER-α1-α2-α3 andα-γcorrelation measurement,three new α decays were observed in addition to the three branches known previously.The one with the largestαdecay energy was regarded as the ground state to ground state transition.The newly measuredαdecay properties of ²²²Pa were examined in a framework of reduced width.     

超重核研究谱仪的RFQ冷却聚束器RFQ1L

介绍了超重核研究谱仪中RFQ冷却聚束器RFQ1L的结构和运用SIMION程序对离子的冷却、聚束、引出和撇气过程的模拟情况。 模拟显示: 通过仔细选择工作点就完全可以把经过充气反冲质量分离器分离后的低品质束流转化为斑点小、发射度小和能量单一的高品质束流， 为紧接其后的磁铁和激光高效率分析提供条件。The structure and the simulation results about the cooling，bunching，extraction and skimming of the RFQ cooler and buncher RFQ1L， which is an important part of the being built super heavy nuclide research spectrometer， have been introduced. It shows that， by careful choice of its working point， we can obtain an ion beam with small beam spot， small emittance and mono energy， which can satisfy the requirements of the successive analyses by dipole and laser with high efficiencies.     

LPT的RF分相偏置电路的研制

为了对兰州彭宁离子阱LPT内的离子运动进行偶极和四极共振激发,采用变压器原理,设计制作了两套分相器:一套工作频率为200 k Hz～4 MHz,适用于四极激发模式;另一套工作频率为1700～1750 Hz,适用于偶极激发模式。详细测试了它们在空载和负载情况下的幅频曲线与相频曲线。测试结果表明:RF分相偏置电路的输出幅度与相位均达到了设计要求。     

兰州彭宁阱核心电极的最优电压幅值计算

彭宁阱是用于直接测量原子核质量的精确设备。为了保证彭宁阱的测量精度,需在阱中心产生精准的四极静电场,而四极静电场是通过对彭宁阱的核心电极施加合适的电压产生的。采用公式推导法和最小二乘法两种方法计算得到了LPT核心电极需加电压幅值。对于公式推导法,电压值完全从理论出发,经公式推导后计算得到;最小二乘法的出发点是使取样偏差的平方和最小,且通过仿真模拟考虑了电极的实际几何形状。由这两种方法得到的非四极项系数C4 和C6,可用于估算因偏离理想四极电场所产生的实验误差。虽然这两种方法的出发点不同,但都可以在阱中心产生需要的四极电场。Penning trap mass spectrometry is one of the direct methods and maybe the most accurate tool for atomic mass measurements. The quadrupole electric eld produced in the trap should be very accurate in order to ensure the precision of measurements. The optimal amplitudes for the key electrodes of the Lanzhou Penning Trap(LPT) have been calculated by two methods|formula derivation and least-squares tting. For formula derivation method, the optimal values are based on the theory and deduced from the formulas. Least-squares tting method is to minimize the quadratic sum of sampling deviations, where the actual geometry of the electrodes has been considered by the simulation. The obtained C4 and C6 values can be used to estimate the experimental error produced by the deviation from the ideal quadrupole electric eld. The expected quadrupole electric led could be gotten by both methods.     

Simulation of the Lanzhou Penning Trap LPT

The LPT (Lanzhou Penning Trap) is under construction and its task is to perform direct mass measurement of fusion-evaporation residues and if possible for heavy isotopes. Detailed simulations have been done for a good understanding to the ion's movement and mechanics in the trap. The optimization of the LPT is also performed based on the simulation. With a scale of 0.5 mm per grid used in the simulation and many other limitations a highest mass resolution has been achieved to be 1.9×10^－5. An unexpected behaviour in the simulation related to magnetron motion has been found.     

高压击穿现象的实验研究和对RFQ冷却聚束器RFQ1L的模拟

RFQ冷却聚束器RFQ1L是正在研制的超重核研究谱仪的一个关键部分. 为了感性认识气体的高压击穿现象, 对电极间能够承受的电压进行了实验测试. 另外, 根据现有已知条件, 重新详细模拟了离子在RFQ1L中的冷却和存储情况, 为RFQ1L实际工作点的选择提供了很好的理论依据.     

Latest progress of the RFQ cooler and buncher RFQ1L

The RFQ cooler and buncher RFQ1L is a key device of the SHANS (Spectrometer for Heavy Atoms and Nuclear Structure). The status of the machining and assembly of the central part is introduced, and the structure of the whole RFQ1L system and the preliminary plan for the testing are discussed also.