Coulomb Excitation with Fluorine-1 8 Isomeric Secondary Beam

为了精确测定极低能量下的天体物理核反应速率，对恒星演化的研究具有重要意义，在九州大学串联加速器实验室（KUTL）建造了一台高分辨率的反冲质量分离器（RMS）。利用能量和动量的差异，RMS能够以高信噪比从主光束中分离出反应产物。利用KUTL RMS系统可以产生不稳定核的二次束。本研究以二次光束诱导反应实现光谱学为目标，研究了二次光束的产生方法。该方法采用了加速器重弹丸与轻靶核相结合的反运动学融合蒸发反应。利用逆运动学，将反应产物反冲到一个有限的正立体角区域内，使其具有足够的二次反应的运动学能量。由于加速器和RMS的限制，氟-18二次光束很难产生，因此我们重点开发了由氟-19光束和氦-4靶产生的钠-22二次光束。经证实，在目前的系统下，有可能产生强度超过10000 cps的钠-22二次光束，而不会产生来自主光束的任何重大污染。我们还开发了用于二次光束实验的带电粒子检测/监测系统。探测器由塑料闪烁体组成，用于定位敏感的光倍增管。该系统具有较高的抗辐照耐久性和适合于TOP测量的快速定时特性。利用二次光束的库仑激发实验来实现光谱学将得到进一步的发展。

In order to precisely determine the astro-physical nuclear reaction rate at very low energy, which is important for the study of stellar evolutions, a high-resolution recoil mass separator (RMS) has been constructed at the Kyushu university tandem accelerator laboratory (KUTL). By using the differences in the energy and momentum, the RMS is capable of separating with high S/N ratio the reaction products from the primary beams. It is possible to produce the secondary beams of unstable nuclei by using this KUTL RMS system.In the present study, aiming the realization of the spectroscopy with secondary beam induced reactions, we developed the method for production of the secondary beams. The method employs the fusion evaporation reactions of inverse kinematics where heavy projectile from the accelerator and the light target nucleus are combined. By using the inverse kinematics, the reaction products are recoiled into a limited region of forward solid angle with a kinematic energies enough for the secondary reactions.Since the fluorine-18 secondary beam was turned out to be very difficult to produce, due to the limitations in the accelerators and the RMS, we then focused on the development of the sodium-22 secondary beam which is produced by fluorine-19 beam and helium-4 target. It was confirmed that with the present system it is possible to produce the sodium-22 secondary beam at an intensity of more than 10000 cps without any significant contamination originating from the primary beam.We also developed the charged particle detection/monitor system for the secondary beam experiments. The detectors are made of plastic scintillators coupled to position sensitive photo multiplier tubes. The system has the high endurance against irradiation and the fast timing characteristics suitable for the TOP measurements. Further development will be made to realize the spectroscopy by Coulomb excitation experiments with secondary beams.