Systematic investigations and improvements of the efficiency, purity and emittance of charge bred ion beams from an ECRIS charge state booster by plasma stabilization using two frequency heating.

通过使用两种频率加热进行等离子体稳定，对来自 ECRIS 电荷态增强器的电荷孕育离子束的效率、纯度和发射率进行系统研究和改进。

• 批准号: SAPPJ-2019-00046
• 负责人: Kester, Oliver
• 金额: $ 2.91万
• 依托单位: TRIUMF
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Project
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=718946
• 关键词: Systematic; investigations; improvements; efficiency; purity

The TRIUMF charge state booster (CSB), based on a 14.5 GHz PHOENIX ECR ion source, raises the charge state of ions from rare isotopes prior to injection into the post accelerator linac. Therewith it allows TRIUMF the post acceleration of isotopes from elements beyond mass 30 to the medium mass range and avoids the stripping of ions at very low kinetic energies, which is not efficient in terms of transmission. An inherent issue of the CSB is that an ECR Ion Source does not operate at Ultra High Vacuum (UHV) conditions and has a significant output of background ions. That's the reason why the level of impurities in such devices is generally high which is a drawback when dealing with very low radioactive ion intensity injection. Investigations of the 1+ to n+ conversion processes in the community demonstrated that the efficiency of the process and quality of the highly charged ion beam produced by the CSB can be significantly enhanced by optimizing the plasma conditions and the beam formation in the extraction region. The ECRIS is superior to an EBIS related to the production of intense beams of rare isotopes >10^8 per second, which is required for nuclear astrophysics experiments. However, the 1+to n+ conversion rate depends on the flexibility of the injection optics, the plasma conditions and the beam formation upon ion extraction, which need to be improved and are the objective of leading edge research in this area. The main objective of this proposal is to improve the TRIUMF CSB performance in terms of beam quality, charge breeding efficiency and beam purity, by introducing techniques which are matter of investigations in the community. The goal is to bring TRIUMF back into the international leadership in charge breeding with ECRIS devices and to deliver higher quality and new beams to the experiments at ISAC. As the injection- and the ionisation efficiency as well as the beam purity essentially depend on the plasma conditions, the two-frequency heating and the tuning of the microwave frequency, will be introduced. These techniques rely on the generation of plasma modes that allow higher plasma densities and optimum coupling of the rf-power as well as stable plasma conditions. The project described in this proposal intends to investigate systematically the charge breeding efficiency and the beam quality by - modifying the plasma conditions using two frequency heating and frequency tuning - beam emittance measurements and corresponding beam extraction calculations. In addition, the CSB will be used to generate intense beams from offline samples for the first time. The significant improvement of the CSB breeding efficiency, the beam properties and additional beam production capabilities will benefit the experimental program at ISAC in particular for accelerated beam experiments. The second aspect is the training of highly qualified personnel in the field of plasma ion sources in general and on ECRIS sources.

基于14.5 GHz PHOENIX ECR离子源的TRIUMF电荷态助推器（CSB）在注入加速器后直线加速器之前提高稀有同位素离子的电荷态。因此，它允许TRIUMF从质量超过30的元素到中等质量范围的同位素的后加速，并避免在非常低的动能下剥离离子，这在传输方面效率不高。CSB的一个固有问题是，ECR离子源不能在超高真空（UHV）条件下工作，并且具有显著的背景离子输出。这就是为什么这种设备中的杂质含量通常很高的原因，这在处理放射性离子强度非常低的注入时是一个缺点。对1+到n+转换过程的研究表明，通过优化等离子体条件和萃取区光束形成，可以显著提高CSB产生高电荷离子束的效率和质量。与EBIS相比，ECRIS在产生稀有同位素每秒10^8的强光束方面具有优势，这是核天体物理实验所需要的。然而，1+到n+的转化率取决于注入光学的灵活性、等离子体条件和离子提取时的光束形成，这些都需要改进，也是该领域前沿研究的目标。