激光离子源的首次在线实验结果

Results of the First On-line Experiment of the Laser Ion Source

介绍了在线同位素分离器使用激光离子源的重要性、激光离子源原理和相关激光技术 ,以及热毛细管激光离子源和靶室的结构 .在首次在线实验中使用 50MeV u1 8O + natTa→1 67Yb(T1 2 =1 7.5m)反应道 ,实现了加速器、分离器和激光系统的联合运行 .通过测量分离后产物的γ谱 ,确定了分离后的 1 67Yb的产额 ,并与从产生截面、束流强度、收集时间和靶厚度计算得到的产生率相比 ,得到总分离效率约为 0 .2 % .通过有激光与无激光条件下测量的γ谱中 1 67Yb与 1 67Lu相应峰下面积比值K得到元素选择性η为 3 .2 .发现了新的 1 67Yb的长寿命高自旋的同质异能态 ,分析了提高效率的途径 .

The importance of using a laser ion source in the on line isotope separator, the principle of laser ion source, laser technique and the structure of hot capillary laser ion source and target chamber are introduced. A high repetition frequncy copper vapor laser and three dye lasers were used. The capillary is made of Nb with inside diameter of 1.7mm and effective length of 3cm. It was heated by 50\_100A direct current and temperature of 1800\_2700K can be achieved. The nuclear reaction channel used in the first on line experiment is 50MeV/u 18 O+ nat Ta→ 167 Yb( T 1/2 = 17.5min). A joint operation of accelerator, on line isotope separator and laser system has been realized. A total separation efficiency of 0.2% is obtained by comparison of the measured yield of 167 Yb with the calculated yield of 167 Yb by using production cross section, beam intensity, collection time and the thickness of target. A element selectivity of 3.2 is deduced from the ratio of the corresponding peak areas of 167 Yb and 167 Lu in the γ spectra of laser on and laser off. A new high spin isomer with long half life of 167 Yb was found. The methods that may be used to improve the efficiency of laser ion source are discussed.