首次使用核反应法鉴别JUNA深地加速器A/q=2的束流种类

Identi?cation of the A/q=2 Beam Species from the JUNA Deep Underground Accelerator by Nuclear Reaction Method for the First Time

JUNA团队计划利用CJPL所提供的极低本底条件和400 kV高压平台上2.45 GHz ECR离子源产生的毫安量级束流首次在天体物理能区对关键核反应进行直接测量。实验需要10 emA的质子束流和He^+束流以及2 emA的He^2+束流。使用2.45 GHz离子源产生毫安量级的He^2+束流是离子源制造的难点。由于离子源分析磁铁分辨能力有限,无法区分He^2+和H^+2离子,本文首次使用核反应法对离子源产生的A/q=2的束流进行了鉴别,结果显示,JUNA项目2.45 GHz ECR离子源无法产生毫安量级的He^2+束流。该研究成果为JUNA项目离子源的设计提供了重要的参考依据。JUNA团队另外研制了一台微波频率为14.5 GHz的ECR离子源并成功产生2 emA的He^2+束流来满足实验需求。

The Jinping Underground laboratory for Nuclear Astrophysics(JUNA)group is planing to take the advantage of the ultra-low background of China Jinping Underground Laboartory(CJPL)and a high current accelerator based on an 2.45 GHz ECR ion source to study some key reactions of the nuclear astrophysics at their stellar energies for the first time.The experiments in JUNA project need proton,He+and He^2+beams with intensities of 10,10 and 2 emA,respectively.The most challenging part of the design and fabrication of ECR ion source is the production of the He^2+beam with intensities at the level of milliamperes.The traditional particle identification method based on magnetic rigidity is difficult to distinguish the He^2+and H^+ions because of their similar mass-to-charge ratios.Therefore,a novel method using nuclear reactions has been developed in this work for the identification of A/q=2 beam species from the ion source.The result shows that the 2.45 GHz ECR ion source can't produce the He^2+beam with a intensity of milliampere.Based on this result,a 14.5 GHz ECR ion source has been developed which has produced 2 emA He^2+beam successfully.