Development of beta-ray full absorption detector for measurement of decay energy of unstable nuclei far off stability.

我们研制了一种新的探测器，即和探测器，用于测定远离稳定核的β射线衰变能量。它由两个相同的HPGe探测器组成，它们面对面地放置。它可以有效地探测电子，这些电子与每个探测器反向散射，并测量两个探测器的能量和。总之，这个想法对于β射线测量非常有效。高能模拟为探测器的设计提供了一个新的视角。如果把大得多的晶体放在没有Be窗口的紧密几何结构中，对于稀有同位素（如新同位素）来说是非常强大的。我们订购了特殊的Ge探测器（ORTEC的LEPS），其具有36 mm × <phi>13 mm × 13 t晶体和薄Be窗口（50 μ m × 13 t）。Be窗口与晶体表面之间的距离为7 mm。用Ge探测器测量了单能电子/正电子的响应函数。利用京都大学反应堆研究所（KURRI）的β射线谱仪，利用30 MeV电子直线加速器产生的高能光子，产生了准单能电子/正电子，电子的放射性活度为~（13）<90>Sr/Y和<38><68><34m>~（13）Cl，正电子的放射性活度为~（13）Ge/Ga和~（13）Cl（KUR-LINAC）利用高达9 MeV。获得的响应函数被评估为三个分量，即，全能量吸收，散射和韧致辐射。用625 keV的^ Cs转换电子实验确定了和探测器的响应函数<137>，并在高能区用EGS 4程序进行了模拟.用<32><42><38><beta>热中子辐照KUR，产生了~（40）P、~（40）K和~（40）Cl的放射性（Q_（1.7-4.9MeV）），用和探测器测量了它们的放射性。两个Ge探测器尽可能靠近放置。晶体之间的距离为17 mm。与β射线单谱相比，在^ K下的典型效率为20%<42>。这些结果与模拟一致。

We have developed a new detector, namely, a sum-detector, for beta-ray decay energy determination of nuclei far off stability. It consists of two identical HPGe detectors, which are located in face to face. It can detect electrons efficiently, which back-scatter with each detector and measure the energy sum of two detectors. In conclusion, this idea is much effective for beta-ray measurements. Simulation in high energy gave a perspective for detector design. If putting much larger crystals in close geometry without Be windows is much powerful for rare isotopes like new isotopes.We proceeded this project as follows.1. We ordered special Ge detectors (LEPS by ORTEC) which have 36mm^<phi>xl3mm^t crystals and thin Be window (50 mum^t) . The distance between the Be window and the crystal surface is 7 mm.2. Response functions for monoenergetic electrons/positrons were measured with the Ge detectors. Using a beta-ray spectrometer in Kyoto University Reactor Research Institute (KURRI) , quasi-monoenergetic electrons/positrons were produced with radioactivities (^<90>Sr/Y and ^<38>Cl for electrons and ^<68>Ge/Ga and ^<34m>Cl for positrons) to 4 MeV Pair production by high energy photons produced by 30MeV electron linear accelerator (KUR-LINAC) was utilized up to 9 MeV.The obtained response functions were evaluated as three components, namely, full energy absorption, scattering and bremsstrahlung, respectively. The response functions of the sum-detector were determined with 625 keV conversion electrons of ^<137>Cs experimentally and simulated using a code (EGS4) in higher energy region.3. The radioactivities of ^<32>P ^<42>K and ^<38>Cl (Q_<beta> : 1.7-4.9MeV) were produced with thermal neutron irradiation in KUR and measured with the sum-detector. Two Ge detector were put as close as possible. The distance between crystals was 17 mm. In comparison with a beta-ray singles spectrum, typical efficiency was 20% in ^<42>K.These results are consistent with the simulation.