Further progress in the development of electron cyclotron resonance (ECR) ion sources (ECRISs) requires deeper understanding of the underlying physics. One of the topics that remains obscure, though being crucial for the performance of the ECRIS, is the electron energy distribution (EED). A well-developed technique of measuring the EED of electrons escaping axially from the magnetically confined plasma of an ECRIS was used for the study of the EED in an unstable mode of plasma confinement, i.e., in the presence of kinetic instabilities. The experimental data were recorded for pulsed and CW discharges with a room-temperature 14 GHz ECRIS at the JYFL accelerator laboratory. The measurements were focused on observing differences between the EED escaping from stable and unstable plasmas. It was found that nonlinear phenomena alter the EED noticeably. The electron losses are enhanced in both unstable regimes, with two-frequency heating suppressing the instabilities. It has been shown earlier that two-frequency heating boosts the ECRIS performance presumably owing to the suppression of instabilities. We report the observed changes in EED introduced by the secondary frequency in different regimes, including an off-resonance condition, where the secondary frequency is lower than the minimum frequency satisfying the resonance condition for cold electrons at the magnetic field minimum. Finally, we suggest an experimental method of qualitative evaluation of the energy distribution of electrons confined in the magnetic trap using a method of measuring energy distribution of lost electrons during the plasma decay in pulsed operation of the ion source.

中文翻译：

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从最小 B 场损失的电子能量分布的测量——不稳定性和双频加热的影响

电子回旋共振 (ECR) 离子源 (ECRIS) 的进一步发展需要对基础物理学有更深入的了解。尽管对 ECRIS 的性能至关重要，但仍然模糊不清的主题之一是电子能量分布 (EED)。一种成熟的测量从 ECRIS 的磁约束等离子体轴向逸出的电子的 EED 技术用于研究处于不稳定等离子体约束模式（即存在动力学不稳定性）的 EED。在 JYFL 加速器实验室使用室温 14 GHz ECRIS 记录脉冲和连续波放电的实验数据。测量的重点是观察从稳定和不稳定等离子体中逸出的 EED 之间的差异。发现非线性现象显着改变了EED。在两种不稳定状态下，电子损失都会增加，双频加热抑制了不稳定性。早先已经表明，可能由于抑制了不稳定性，双频加热提高了 ECRIS 性能。我们报告了观察到的由不同状态的次级频率引入的 EED 变化，包括非共振条件，其中次级频率低于满足磁场最小值冷电子共振条件的最小频率。最后，我们提出了一种定性评估限制在磁阱中的电子能量分布的实验方法，该方法使用测量离子源脉冲操作中等离子体衰变过程中丢失电子的能量分布的方法。