RIBLL上的β^+缓发粒子发射的在束测量

In-beam Measurement of β^+ Delay Particle Decay on RIBLL

报道了在新建成的放射性次级束流线上完成的2 0 Na的 β+缓发α粒子发射2 0 Na—→β+ 2 0 Ne →16 O +α的在束测量 .通过飞行时间和能损符合的方法实现2 0 Na次级束流的在束鉴别与调制 .在束和停束两个获取时段分别完成对次级束流和β+缓发粒子的记录 .利用脉冲发生器和记数器实现2 0 Na缓发粒子衰变半衰期的测量 .实验测量到2 0 Ne几个低能共振能级的衰变能量分别为 2 69,3 0 9,4 74 ,5 54MeV ,相对强度分别为 1 0 0 ,4 1 5,1 1 0 ,1 5 2 0 .测量到2 0 Na的β+缓发α衰变的半衰期为 (4 59± 7)ms,与现有的核数据基本上吻合 .

The in beam measurement of β + delay α decay of 20 Na on the Radioactive Ion Beam Line in Lanzhou(RIBLL) is reported. The radioactive ion 20 Na was identified in beam by means of TOF -Δ E method. The implantation depth of the secondary beam in the detectors was optimized by a group of degraders with different thickness. The procedure of data acquisition was divided into two stages, i.e., in beam and off beam stage, to record the RIB and the β + delay α particles respectively. Four resonant energy levels, 2 69, 3 09, 4 74, and 5 54MeV of 20 Ne, have been observed with their relative amplitudes of 100, 4 15, 1 10 and 15 2, respectively. The half life of 20 Na—→ β + 20 Ne *→ 16 O+α decay is preliminarily determined to be 459ms by using a time scaler combined with a pulse generator. The results are in good agreement with the ones of other group.