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Production of low energy spin-polarized radioactive nuclear beam using superfluid helium

利用超流氦产生低能自旋极化放射性核束

基本信息

批准号：
13640286
负责人：
SHIMIZU Suguru
金额：
$ 2.24万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640286/
关键词：
Superfluid helium spin polarization K meson beam 不安定原子核

项目摘要

This study is aiming at developing a superfluid helium target for radioactive nuclear beam and meson beam. We have realized that approximately 30% of implanted particles remain as an ion state in the helium. We have planed to extract these ions from the helium target and generate low-energy polarized nuclear beam by introducing a spin polarizer with a polarized electron transfer reaction. In order to transport unstable nuclei into the polarizer with high efficiency it is necessary to monitor their positions. We have measured the decay position by reconstructing the beta-ray trajectory. Moreover, we installed a range-stack type detector with 6 plastic layers to measure end-point energy of beta decays. Scintillation photons produced in each layer were transferred through optical fiber embedded in the counter, which enable us not to interfere with other detector elements. By making coincidence this end-point detector and gamma detector, it can be extracted much more detailed information for the nuclear spectroscopy. Also, we are planing to use superfluid helium as a stopping target for K beam. This is why energy loss of secondary particles by the target material is drastically reduced comparing with standard solid target. The feasibility study was performed by tuning of the K beam line and by measuring momentum spectra of the secondary particles. As a consequence, superfluid helium is applicable fox the stopping target at J-PARC under the condition of low momentum dispersion of K beam at the target position.

本研究旨在研制一种用于放射性核束和介子束的超流氦靶材。我们已经意识到，大约30%的注入粒子仍然以离子状态存在于氦中。我们已经计划通过引入带有极化电子转移反应的自旋偏振器来从氦靶中提取这些离子并产生低能极化核束。为了将不稳定的原子核高效地输送到偏振器中，有必要对它们的位置进行监测。我们通过重建β射线的轨迹测量了衰变位置。此外，我们还安装了一个有6个塑料层的射程堆叠式探测器来测量β衰变的端点能量。每一层产生的闪烁光子都通过嵌入在计数器中的光纤传输，这使得我们不会干扰其他探测器元件。通过将这种端点探测器和伽马探测器进行重合，可以为核能谱提取更详细的信息。此外，我们还计划使用超流氦作为K束的停止靶。这就是为什么与标准固体靶相比，靶材料对二次粒子的能量损失大大减少。可行性研究是通过调整K束线和测量次级粒子的动量谱来进行的。结果表明，在K束在靶位置的动量色散较低的情况下，超流氦适用于J-PARC停止靶。