空间高能质子辐照诱发介质材料放电特性实验研究

Experimental Study on Discharge Characteristic of Dielectric Material Induced by Space High-energy Proton Irradiation

  • 摘要: 介质材料中电子诱发的充放电现象已被广泛研究,然而,随着深空探测任务向月球、火星和木星的推进,航天器在这些空间环境中将暴露于高通量的高能质子辐射下,这使得理解质子引发的充放电机制变得尤为重要。本文研究了40 MeV质子辐照下聚酰亚胺(PI)介质材料的击穿现象,分别对不同厚度的PI薄膜的放电行为进行了研究。结果表明:对于厚度为21.5、15.5和13.6 mm的PI薄膜,当质子达到一定积分通量时会触发放电现象。而对于厚度为8.2 mm的PI薄膜,在实验条件下未观察到放电事件,说明材料存在一个最易触发放电的临界厚度范围,达到厚度范围的材料会诱发放电事件。

     

    Abstract: Spacecraft are usually exposed to complex radiation environments during in-orbit flight and are prone to the accumulation of large amounts of electrical charges on the surface and inside the materials. Continuous charge accumulation can induce severe electrostatic discharge events, which can cause damage to spacecraft systems and even jeopardize the success of the entire mission. The deep charge-discharge phenomenon inside dielectric materials is one of the important factors leading to operational failures of on-orbit spacecraft and even mission failures. Currently, the electron-induced dielectric charge-discharge phenomenon has been extensively studied. However, with the advancement of exploration in the Van Allen belts and deep space exploration missions to the Moon and Mars, galactic cosmic rays and solar proton events have gradually become the main radiation environments faced by spacecraft, and there is still a lack of research on the charging and discharging characteristics of proton-induced dielectric materials. In order to study the discharge characteristics of proton-induced dielectric materials, this study carried out a proton beam irradiation experiment with an energy of 40 MeV and an injection of 1010 cm−2·s−1 using the proton accelerator facility at the National Space Science Centre of the Chinese Academy of Sciences (NSSC). Polyimide (PI) dielectric samples of 80 mm×100 mm with different thicknesses were placed in a vacuum target chamber system facing a 100 mm diameter titanium window and shielded with aluminium around the sample. The experiments were carried out under a vacuum of 10−4 Pa at room temperature, with the grounding electrode tightly fitted to the back of the dielectric material and grounded by connecting a wire to a Rogowski coil. The discharge signal inside the dielectric material was collected by the Rogowski coil and recorded by an oscilloscope. The experimental results show that the PI films with thicknesses of 21.5, 15.5 and 13.6 mm, respectively, show significant discharges after a cumulative proton integrated flux of 1012 cm−2, whereas no discharges are observed for the PI film with a thickness of 8.2 mm under the same conditions. This result may be attributed to the accumulation of more protons inside the thicker PI material, which leads to the enhancement of the internal electric field and is more likely to trigger the discharge phenomenon. The above results provide an important experimental basis and theoretical reference for further exploration of the reliability of spacecraft dielectric materials under the complex radiation environment in deep space.

     

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