Evolution of vacancy-type defects has been investigated in undamaged and copper ion pre-damaged tungsten exposed to low-energy and high-flux helium plasma (60 eV, 1 × 10²² He/m²s). The results measured by Doppler broadening positron annihilation spectroscopy (DB-PAS) indicate that helium-vacancy complexes generate due to intense self-trapping in the undamaged tungsten after helium plasma exposure. In contrast, the occupation of pre-existing vacancies and vacancy clusters, caused by the presence helium atoms, plays a dominant role in the pre-damaged tungsten, but the density of vacancy-type defects in the pre-damaged case is still higher than that in the undamaged case. This means that the dominating process of helium-vacancy complexes formation in tungsten changes from self-trapping to vacancy-trapping in the case of high vacancy density. Meanwhile, the elastic recoil detection analysis (ERDA) and transmission electron microscopy (TEM) results reveal that these pre-existing defects can increase helium retention and helium nano-bubble size. However, it is surprising that in the case of pre-damaged sample, the density/volume of vacancy-type defects also decreased even outside of the helium distribution depth. We attribute this phenomenon to the interstitial dislocation loops punched by helium clusters preferentially diffusing into the pre-damage regions of tungsten far beyond the helium distribution depth, resulting in the significant recombination with vacancies or vacancy clusters. This intrinsic mechanism is further verified by TEM observations and molecular dynamics (MD) simulations.

在暴露于低能量和高通量氦等离子体（60 eV，1×10 ²² He / m ^2）的未损坏和铜离子预损坏的钨中，研究了空位型缺陷的演变s）。多普勒加宽正电子an没光谱法（DB-PAS）测得的结果表明，氦气等离子体暴露后，由于未损坏的钨中强烈的自捕获，产生了氦空位络合物。相反，由氦原子的存在引起的先前存在的空位和空位簇的占据在预损坏的钨中起主要作用，但在预损坏的情况下空位型缺陷的密度仍高于在未损坏的情况下。这意味着在高空位密度的情况下，钨中氦空位络合物形成的主要过程从自捕获变为空位捕获。与此同时，弹性反冲检测分析（ERDA）和透射电子显微镜（TEM）结果表明，这些预先存在的缺陷会增加氦气的截留率和氦气纳米气泡的尺寸。然而，令人惊讶的是，在预损坏的样品中，空位型缺陷的密度/体积甚至在氦分布深度之外也降低了。我们将此现象归因于由氦团簇冲破的间隙错位环优先扩散到钨的破坏前区域，远远超过了氦的分布深度，从而导致与空位或空位团簇的显着重组。TEM观察和分子动力学（MD）模拟进一步验证了这种内在机理。空位型缺陷的密度/体积甚至在氦分布深度之外也降低了。我们将此现象归因于由氦团簇冲破的间隙错位环优先扩散到钨的破坏前区域，远远超过了氦的分布深度，从而导致与空位或空位团簇的显着重组。TEM观察和分子动力学（MD）模拟进一步验证了这种内在机理。空位型缺陷的密度/体积甚至在氦分布深度之外也降低了。我们将此现象归因于由氦团簇冲破的间隙错位环优先扩散到钨的破坏前区域，远远超过了氦的分布深度，从而导致与空位或空位团簇的显着重组。TEM观察和分子动力学（MD）模拟进一步验证了这种内在机理。