Study On The Ion Source Of Hydrogen And Helium Coaxial Ion Implanter

Long-term safe operation of nuclear power plant heavily relies on the nuclear material performance. The particularity of nuclear materials is embodied in radiation effects and radiation accelerated effects. Transmutation products (primarily hydrogen and helium) in reactor material and displacement caused by neutron damage often according to certain proportion produced at the same time, so the synergy of hydrogen, helium and displacement damage cannot be observed in single ion beam irradiation. To simulate neutron irradiation more accurately, triple ions beams (H, He and heavy ions) are needed to bombard the target as a major cause to displacement damage. Transmission electron microscope (TEM) coupled with ion accelerators, which links with ion beam sources, allows in-situ structural and chemical observation of materials during irradiation under high displacement damage rates. The facility which is being built in Xiamen University will be the first three-ion-beams apparatus and transmission electron microscopy online facilities in the world, and will play an important role in nuclear materials research and development. The planned facility in Xiamen University consist of a400kV ion implanter, a50kV low energy hydrogen-helium coaxial ion implanter, a300keV high resolution transmission electron microscopy and a3MV tandem accelerator. Through the use of these devices, three ion beams can be directed to a sample in TEM simultaneously for the in-situ observation of collective effects of displacement damage and the inclusion of hydrogen and helium.Ion source for low energy hydrogen and helium coaxial implanter is an important part of this facility. Penning ion source was used as such ion source because of stability at low pressure, long life-time, simple structure and power supply system compared with other ion sources such as high-frequency ion source, Freeman ion source and radio-frequency ion source. In this research, we applied different voltages to two anodes of the penning ion source to study performance parameters and the mass spectrum of ion beam. By studying the relationship between the parameters and performance of the ion source, we found that a strong magnetic field can reduce breakdown voltage of the ion source and the intensity of the ion beam increases with rising gas pressure. Meanwhile, the intensity of the ion beam decreases when anode voltage increases while the intensity of the ion beam has a significant increment due to gas pressure. The ion beam angle first decreases then remained stable with increasing anode voltage. The total H2+content of the ion beam is from84%to91%. And the content decreases with increasing discharge voltage, and increases slightly with increasing gas pressure. We also applied two different voltages to the two anodes in the main structure of the ion source. There was no significant change of discharge characteristics of ion source. And the content of H2+did not show obvious increase with changing discharge voltage compared with that of applying the same voltage to the two anodes. Based on experimental results, stable ion beam with high intensity and good quality can be generated using anode voltage between600V and750V and gas flow rate between0.043ml/min and0.20ml/min. The intensity of generated ion beam varies from20μA to100μA.