FRAC: Fringing-RF-field-activated dc-to-pulse converter for low-energy ion beams.
FRAC: Fringing-RF-field-activated dc-to-pulse converter for low-energy ion beams.
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FRAC：用于低能离子束的边缘射频场激活直流脉冲转换器。
DOI：
10.1063/1.5023609
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
K. Yamada
中科院分区：
文献类型：
--
作者：
M. Wakasugi;M. Togasaki;T. Ohnishi;K. Kurita;R. Toba;M. Watanabe;K. Yamada
我们开发了一种新型直流脉冲转换器，称为 FRAC（边缘射频场激活直流脉冲转换器），用于从离子源静电加速低能离子束。 FRAC 基于射频四极 (RFQ) 线性阱技术，原则上在超高真空条件下工作。 RFQ 棒边缘区域周围扭曲的射频场中产生的交变纵向电场使连续注入 FRAC 的离子减速。这些离子在 FRAC 中积累了相当长的时间。当进入离子的能量超过注入势垒电势小于几个电子伏并且能量扩散非常小时，这种边缘效应最为显着。 FRAC 操作期间堆积的离子以高强度脉冲束的形式喷出。我们研究了 FRAC 的性能以及一些为提高直流脉冲转换效率而开发的 FRAC 操作方法的能力。 FRAC 工作频率为 10 赫兹和 1 赫兹时，实现的最大转换效率分别为 22% 和 5.6%。实际上，在注入直流束强度为 4.6 nA 且工作频率为 1 Hz 时，持续时间为 500 μs 的输出束脉冲中包含的离子数量为 1.6 × 109 个离子/脉冲。
We developed a new type of dc-to-pulse converter, called FRAC (Fringing-RF-field-Activated dc-to-pulse Converter) for low-energy ion beams electrostatically accelerated from an ion source. FRAC is based on a radio-frequency quadrupole (RFQ) linear trap technique and works in principle under ultrahigh vacuum conditions. Ions continuously injected into FRAC are decelerated by an alternating longitudinal electric field produced in a distorted radio frequency field around the edge region of RFQ rods. These ions accumulate in FRAC for a significantly long time. This edge effect appears most notably when the energy of incoming ions exceeds the injection barrier potential by less than a few eV and the energy spread is quite small. The ions stacked during the FRAC operation period are ejected as a high intensity pulsed beam. We investigated the performance of FRAC and the capability of some FRAC operation methods developed to enhance the dc-to-pulse conversion efficiency. The maximum conversion efficiencies achieved were 22% and 5.6% at FRAC operation frequencies of 10 and 1 Hz, respectively. The number of ions contained in an output beam pulse with a duration of 500 μs was in practice 1.6 × 109 ions/pulse at an injected dc beam intensity of 4.6 nA and an operation frequency of 1 Hz.