Development of an electron-attachment-type negative fullerene ion source
Development of an electron-attachment-type negative fullerene ion source
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电子附着型负富勒烯离子源的开发
DOI：
10.1063/1.5053318
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Y. Saitoh
中科院分区：
文献类型：
--
作者：
K. Yamada;A. Chiba;Y. Hirano;Y. Saitoh
从离子源增强负富勒烯（C60）离子束电流是研究和开发利用MeV能量C60离子束与串联加速器是必不可少的。一般采用铯溅射型离子源产生负C60离子束。负C60离子束的平均电流约为50pa，由于溅射阴极中的C60分子受到铯离子[1]的冲击而断裂，电流在一个小时或更短的时间内下降到1/100。因此，我们正在开发一种电子附着型C60负离子源来替代铯溅射型离子源。C60具有2.65 eV的高电子亲和力，当电子能在0.2 ~ 12 eV范围内时，其电子附着截面较大。在这种方法中，升华后的C60通过捕获低能电子而被负电离。研制了一种新型离子源，它由离子产生室、样品汽化炉和灯丝作为供电子源组成。离子源的负离子生成试验在配备分析磁铁的离线试验台进行。结果表明，在3 keV的束流能量下，可以提取出600 nA的c60束流。除了灯丝发出的热电子外，C60电离发出的低能电子可能也是负C60离子产生的原因，因为正C60离子同时产生。通过逐步提高烘箱温度和灯丝电流，可使电流保持恒定10小时以上。离子源的细节和负C60离子生成测试的结果将在会议上报告。
Intensification of negative fullerene (C60) ion beam current from an ion source is indispensable for research and developments using a MeV energy C60 ion beam with a tandem accelerator. Generally, a cesium sputtering type ion source has been used to generate a negative C60 ion beam. An average current of the negative C60 ion beam is about 50 pA, and the current goes down to 1/100 within an hour or less because the C60 molecules in a sputter cathode were broken by the impact of cesium ion [1]. Therefore, we are developing an electron attachment type C60 negative ion source alternative to the cesium sputtering type ion source. A C60 has a high electron affinity of 2.65 eV, and the electron attachment cross section is high when the electron energy ranges from 0.2 to 12 eV. In this method, the sublimed C60 is negatively ionized by capturing a low energy electron. A new ion source which is composed of an ion generation chamber, a sample vaporization oven, and a filament as an electron supplying source has been made. The negative ion generation test with the ion source is performed in off-line test stand equipped with an analyzing magnet. As a result, the C60-beam current of 600 nA is able to extract at the beam energy of 3 keV. In addition to the thermal electrons emitted from the filament, low energy electrons emitted by ionization of C60 might be contributing to the generation of negative C60 ions, because the positive C60 ions are generated at the same time. The current can be kept constant more than 10 hours by gradually increasing the oven temperature and the filament current. Details of the ion source and the results of negative C60 ion generation test will be reported at the conference.