Development of seven-dimensional detector system for low-energy light heavy-ions and its application to research on nuclear data of astrophysical interest

为九州大学串列加速器实验室的反冲质量分离器研制了一种新的焦平面探测器系统，它能同时获得能量小于1 MeV/u的轻重离子在焦平面上的二维倾斜角和位置、能量、质量数和原子序数的信息。该系统由一个固态探测器（SSD）和两个二维位置敏感微通道板（MCP）组成，用于探测固态探测器前面的薄金属箔上的离子感生电子，最初计划采用大有效面积的固态探测器来实现飞行时间的长飞行距离测量。然而，使用来自串列加速器的束的具有大的有效面积的SSD的性能测试已经揭示了即使在原子序数小于10的范围内脉冲高度赤字对测量的粒子的原子序数的显著依赖性，这对于具有相对小的有效面积的SSD还没有观察到。这些发现迫使我们改变探测系统的设计，将有效面积小的SSD放置在焦平面上。我们采用了一种利用下游箔片电子发射产额的粒子识别方法。使用来自串列加速器的14 C束测试商业箔的均匀性<12>，并且发现Mylar箔具有小于3%的不均匀性。在考虑能量离散的情况下，利用该分离器和探测器系统对0.2和0.5 MeV/u ^ O的原子序数分辨率<16>分别为0.2和0.1。整个系统的性能测试正在进行中，利用分离器和探测器系统测定恒星能量下^4He（^<12>C，^<16>O）γ反应速率的试验即将开始。

A new focal plane detector system for a recoil mass separator at Kyushu University tandem accelerator laboratory, designed to be capable of obtaining information of light heavy-ions with energies of less than 1 MeV/u on two-dimensional inclined angles and positions on the focal plane, energy, mass number and atomic number simultaneously, has been developed. The system consists of a solid state detector (SSD) and two two-dimensional position sensitive microchannel plates (MCPs) to detect ion-induced electrons from thin foils located in front of the SSD.The SSD with large active area was in beginning planned to be adopted to realize long flight pass for the measurement of time-of-flight. However, the performance test of the SSD with large active area using beams from the tandem accelerator has revealed significant dependence of pulse height deficit on the atomic number of the measured particles even in the range of atomic numbers less than 10, which has not been observed for the SSDs with relatively small active area. These findings imposed change of the design of the detection system to place the SSD with small active area at focal plane.We adopted a particle identification method using the emission yield of electrons from the downstream foil. Homogeneity of commercial foils was tested using a ^<12>C beam from the tandem accelerator and found that the Mylar foil has inhomogeneity of less than 3%. With this foil, the atomic number resolution has been estimated for 0.2 and 0.5 MeV/u ^<16>O to be 0.2 and 0.1, respectively, taking the energy straggling into account.The performance test of the whole system is now in progress and a trial to determine the ^4He(^<12>C,^<16>O)γ reaction rate at stellar energies using the separator and the detector system is about to start.