Construction of a polarized positron generator at low energy

从β衰变发出的正电子是纵向极化的，螺旋度为v/c，其中v和c分别是正电子和光的速度。此外，如果使用放射性同位素，很难获得具有一定能量和足够积分的正电子束。我们在这个项目中取得的成果是：1.我们发展了通过核反应产生极化正电子的新方法，其中18MeV的入射质子由紧凑的回旋加速器产生。建立了利用塞曼效应测量正电子极化的可靠方法。我们完成了模拟正电子在电场、磁场和材料中的去极化的蒙特卡罗模拟器。这些成果已经在国际会议和研讨会上发表了演讲。在这项研究的知识基础上，我们可以建造独特的设施，提供高质量的偏振正电子束，即TOPPS(东京都大学偏振正电子束系统)，使我们能够进行各种关于基本粒子物理、固体物理和生物物理的实验研究。

Positrons emitted from beta-decay is longitudinally polarized and have a helicity of v / c where v and c are the velocity of the positron and light respectively. Furthermore if one utilizes a radio-isotope, one can hardly obtain positron beams with definite energy and sufficient intesitiy.What we have achieved in this project is :1. We developed the new method to produced polarized positrons by means of the nuclear reaction ^<27>Al (p, n) ^<27> Si where incident protons of 18 Me Vare produced by a compact cycrotron.2. We established the reliable method to measure positron polarizations by utilizing the Zeeman effect.3. We completed the Monte Carlo simulator which can describe positron depolarizations in electric and magnetic fields as well as in materials. These achivements have been lectured in the international conferences and symposiums.On the basis of knowledges obtained in this research, we could construct the unique facility to provide high quality polarized positron beams i. e. TOPPS (TOkyo metropolitan university Polarized Positron beam System) which will enable us to perform various experimental studies concerning elementary particle physics, solid states physics and biological physics.