Generation and Investigation of radium muonic atoms in thin solid hydrogen films

在这项研究中，我们提出了在固体氢膜中注入Re同位素以形成具有不稳定核的µ子原子，并进行Muonic X射线光谱来确定转移速率、同位素位移和核电荷半径。这种方法的创新之处在于，由于只需要很小的原子核浓度(ppm级)就可以进行Muon X射线能谱实验，所以这种方法的创新之处在于，它是基于Muon向固体氢中的高Z核的转移反应机制，从而有效地产生Muon原子。该项目的目标是开发一种新的离子源，可以产生长寿命的放射性镭同位素离子，以便将其植入固体氢膜并产生具有放射性原子核的缪子原子。这种新的离子源需要设计成可以与现有的实验装置(μA^*)一起使用，用于在安装在RIKEN-RAL Muon设备上的固体氢膜中注入离子进行Muton原子光谱。这项为期3年的…项目的主要成果更多的是建造一种新的表面电离离子源，目的是在未来使用放射性同位素。选择了表面电离型离子源，因为它能够高效地从碱金属和碱土金属中产生离子，这不仅是产生镭同位素离子的理想选择，而且还可以产生许多其他稳定的离子束，用于优化和调谐。在镭的情况下，由于没有稳定的同位素，之所以选择钡元素，是因为它属于同一族，具有相似的电离能。因此，通过掺入稳定的钡同位素作为标记物，可以先用稳定的原子核有效地调整和优化实验条件，然后再很容易地切换到不稳定的原子核来进行镭离子的实验。这种新的表面电离离子源去年在京都大学研究反应堆研究所进行了测试。成功地电离了钡离子，产生了几个μA的钡束。还检查了离子源的稳定性，在运行几个小时后没有观察到明显的束流劣化。2006年1月，它被运往英国卢瑟福·阿普尔顿实验室，并安装在里肯-拉尔港4区的μA^*实验装置上。安装工作进展顺利，目前已基本完成。使用新离子源的第一次实验计划在今年秋天的某个时候进行。将产生钡束，并将其注入固体氢膜中，以进行µ子X射线光谱分析实验。第一批实验结果将在以后的出版物中公布。然而，在该系统中使用任何镭放射性同位素之前，将需要对现有的μA^*设备进行几次修改和改进，以安全地处理放射性材料。特别是，泵送系统需要升级，并安装排气烟囱。离子源周围还需要局部辐射屏蔽。较少

In this research, we proposed to implant radium isotopes in solid hydrogen films to form muonic atoms with unstable nuclei, and conduct muonic X-ray spectroscopy to determine transfer rates, isotope shifts and nuclear charge radii. The originality of this method was based on the muon transfer reaction mechanism to higher Z nuclei in solid hydrogen to efficiently produce muonic atoms, since only a very small concentration of nuclei (ppm level) is required to perform muonic X-ray spectroscopy experiments. The goal of this project was to develop a new ion source that can produce long-lived radioactive radium isotope ions, in order to be implanted in solid hydrogen films and produce muonic atoms with radioactive nuclei. This new ion source needed to be designed so that it can be used with the existing experimental apparatus (μA^*) for muonic atom spectroscopy with implanted ions in solid hydrogen films installed at the RIKEN-RAL Muon Facility. The main achievement of this 3 years project w … More as the construction of a new surface ionization ion source with the aim of using in the future radioactive isotopes. A surface ionization type ion source was selected because it is capable of producing ions from alkali and alkaline-earth metals with high efficiency, which is ideal to produce radium isotope ions, but also to produce many other stable ion beams for optimization and tuning purposes. In the case of radium, since there are no stable isotopes, the element barium is selected because it is in the same group and has similar ionization energy. Therefore, by mixing stable barium isotope as a marker, it is possible to first adjust and optimize efficiently the experimental conditions using stable nucleus, and then switch easily to unstable nucleus to perform the experiment with radium ions. This new surface ionization ion source was tested last year at KURRI (Research Reactor Institute, Kyoto University). Barium ions were successfully ionized and barium beams of several μA were produced. The stability of the ion source was also examined, and no significant beam deterioration was observed after several hours of operation. In January 2006, it was shipped to the Rutherford Appleton Laboratory in the UK, and installed on the μA^* experimental apparatus at RIKEN-RAL port 4 area. The installation went smoothly, and is now almost completed. The first experiment using the new ion source is scheduled sometime this autumn. Barium beams will be produced and implanted in solid hydrogen films to conduct muonic X-ray spectroscopy experiments. The first experimental results will be reported in a later publication. However, before any radium radioactive isotopes can be used in this system, several modifications and improvements to the existing μA^* apparatus will be required to handle radioactive materials safely. In particular, the pumping system will need to be upgraded and an exhaust stack installed. Local radiation shielding will also be needed around the ion source. Less