^(12)C^(3+)离子束在HIRFL-CSRe上的初步电子冷却调试

The First Electron Cooling Commissioning of ^(12)C^(3+) Beam at HIRFL-CSRe

非全裸离子在储存环内冷却储存时主要通过碰撞离化和辐射电子俘获进行损失。兰州重离子加速器(HIRFL)实验环(CSRe)调束发现,能量为122 MeV/u的^(12)C^(3+)离子束注入到CSRe后的存储寿命仅为6.6s,且电子冷却效果不明显。本文结合CSRe真空条件计算了^(12)C^(3+)离子束的存储寿命及其电子冷却时间,确定了CSRe平均真空度为10-8 Pa量级是导致非全裸的^(12)C^(3+)离子束存储寿命减小的主要原因,而电子冷却作用及辐射电子俘获引起的^(12)C^(3+)离子束损失被^(12)C^(3+)离子束与残余气体碰撞离化损失所掩盖,即^(12)C^(3+)离子束在未被完全冷却前便由于存储寿命过短而近乎全部损失。这解释了CSRe初步电子冷却调试中^(12)C^(3+)离子束快速损失的主要原因。

The partly stripped ions get loss in storage ring when the charge state changes through collision ionization by residual gas and capturing electrons from electron beam. It was found in the first electron cooling commissioning of 12C^3＋ beam at HIRFL-CSRe that the lifetime of 122 MeV/u 12C^3＋ beam is only 6.6 s shorter than expected, and the electron cooling effect is unobvious. The lifetime of 12C^3＋ at CSRe and its electron cool- ing time were calculated in this paper. The result shows that the vacuum pressure at the order of 10 8 Pa causes severe 12C^3＋ beam loss at CSRe. The beam loss due to recombi- nation and cooling effect is unapparent in comparison with the one by collision ioniza- tion. The calculation explains the accidental fast beam loss in the first electron cooling commissioning of 12C^3＋ beam at CSRe.