Q_β measurements with a newly developed total absorption detector.

1.我们研制了一种新的探测器，即全吸收探测器，它由两个完全相同的BGO闪烁探测器组成，它们面对面地放置，用于测定远不稳定核的β衰变能量（Q_β），测量精度为0.3MeV。它不仅能有效地探测后向散射电子，而且能探测γ射线，还能探测高能电子产生的韧致辐射光子。由于它具有较高的全能量探测效率，因此可以在没有衰变谱信息的情况下确定Q_β。这意味着该探测器将成为新同位素等弱活度物质Q_β测定的有力工具.该<235>探测器安装在京都大学研究堆（KUR-ISOL）的在线质量分离器上，用于测量热中子引起的~ 1U裂变产物中的短寿命不稳定核。首先，我们测量了几个Q_β较好的丰中子核，作为探测器的在线能量刻度。我们得到了一些重要的结果， ...更多信息 这种探测器不需要衰变谱信息，就能确定Q_β，传统的分析方法，即平方根图，与塑料闪烁探测器一样有效。到目前为止，所获得的结果的准确性被评估为0.1-0.2兆电子伏。在此基础上，我们首次成功地测定了^ Ce的Q_β<151>为5.27（20）MeV。此外，我们还首次成功地测量了^&lt;153，154&gt;Pr和^ Pm的Q_β<157>。考虑到质量分离器的产额，100个粒子/s的产额足以确定Q_β。在JAERI-ISOL装置上成功地寻找到的一些新的同位素，如~（116，167）Tb，可望通过用大量的硼化橡胶片和镉片屏蔽探测器来降低本底辐射，从而测定其Q_β.总之，我们成功地研制了一种用于Q_β测量的新型全吸收探测器，并利用在线质量分离器在0.3MeV的预期精度范围内推导了丰中子同位素的Q_β。少

1. We have developed a new detector, namely, a total absorption detector, for β-decay energy (Q_β) determination of nuclei far off stability with the accuracy of 0.3 MeV.It consists of two identical BGO scntillation detectors, which are located in face to face. It can detect not only back-scattering electrons but also γ-ray efficiently, moreover, bremsstrahlung photons caused by high-energy electrons. Owing to its high full-energy-detection efficiency, Q_β can be determined without decay scheme information. It means this detector will become a powerful tool for Q_β determination for weak activity like new isotopes.2. For measurement short-lived unstable nuclei from fission products of ^<235>U with thermal neutron, this detector was set in an on-line mass-separator installed at Kyoto University research reactor (KUR-ISOL). At first, some neutron-rich nuclei whose have well-determined Q_β were measured as an on-line energy calibration of the detector. We obtained some important results t … More hat this detector could be certainly determined Q_β without decay scheme information and conventional analyzing method, that is a square root plot, was effective similar to the plastic scintillation detector. So far, the accuracy of the obtained results was evaluated to be 0.1-0.2 MeV.3. On the basis of this result, we successfully determined the Q_β of ^<151>Ce to be 5.27 (20) MeV for the first time. In addition, we succeeded in measurements of Q_β of ^<153,154>Pr and ^<157>Pm for the first time. Taking into account the yield from the mass-separator, the yield of 100 particles/s is enough to determine Q_β. Some new isotopes e.g. ^<116,167>Tb, we succeeded in search at JAERI-ISOL facility, are expected to determine their Q_β by reducing background radiation by shielding the detector with much amount of borated rubber sheets and Cd sheets.4. In conclusion, we succeeded in development a newly total absorption detector for Q_β determination and deduced some Q_βs of neutron-rich isotopes using an in-line mass-separator within the expected accuracy of 0.3 MeV. Less