Helium retention in krypton ion pre-irradiated nanochannel W film

Abstract

Nanochannel tungsten (W) film is a promising candidate as an alternative to bulk W for use in fusion applications. In previous work it has been shown to have good radiation resistance under helium (He) irradiation. To further understand the influence of the irradiationinduced displacement cascade damage on helium retention behaviour in a fusion environment, in this work, nanochannel W film and bulk W were preirradiated by 800 keV Kr 2+ ions to the fluence of 2.6 × 10 15 ions cm −2 and subsequently irradiated by 40 keV He + ions to the fluence of 5 × 10 17 ions cm −2 . The Kr 2+ ion preirradiation greatly increases helium retention in the form of small clusters and retards the formation of large clusters. It can effectively inhibit surface helium blistering under high temperature annealing. Compared with bulk W, no cracks were found in the nanochannel W film postirradiated by He + ions at high fluence. The release of helium from the nanochannel W film is more than one order of magnitude higher than that of bulk W whether they are irradiated by single He + ions or sequentially irradiated by Kr 2+ and He + ions. Moreover, swelling of the bulk W is more serious than that of the nanochannel film. Therefore, nanochannel W film has a higher radiation tolerance performance in the synergistic irradiation.

Review on helium behaviors in nanochannel tungsten film

“…However, different phenomena were shown on the synergistic irradiated bulk W. No blister appeared on the bulk W surfaces when the subsequently irradiated He fluence was 3 × 10 17 ions•cm −2 . With continuously increasing of the He fluence to 5 × 10 17 ions•cm −2 , the size and density of blisters formed on the bulk W decreased significantly compared with those of individual He + ions irradiated bulk W at the same fluence [39]. These results show that the pre-irradiated Kr 2+ ions can effecitvely inhibit the formation of surface blistering.…”

“…Ion beam irradiation with many advantages such as flexible irradiation conditions is considered as an effective method to simulate the neutron irradiation, although there are some differences with the neutron irradiation [38]. Using the high-energy heavy ions irradiation (800 keV krypton (Kr 2+ )) to simulate the displacement cascade damage induced by the neutron irradiation, the displacement damage influence on the He retention in nanochannel W film was further studied [39].…”

Different Radiation Tolerances of Ultrafine-Grained Zirconia–Magnesia Composite Ceramics with Different Grain Sizes

“…From the above analysis, it can be seen that the shift tendency of each peak under different damage conditions was different, which means that its ability to resist He + ion irradiation was different. Referring to Figure 3, it can be considered that the left-shift of the diffraction peak was produced due to the lattice swelling induced by He bubbles, while the subsequent right-shift of the peaks in SGs was mainly due to the stress relaxation induced by crack formation, as shown in the TEM image [26,27]. For the LGs, although the cracks formed under high He concentration, this did not affect the continued swelling of the monoclinic grains (peak {111} m ), which may have been due to the large grain size preventing the release of He in time.…”

Recent progress of radiation response in nanostructured tungsten for nuclear application

“…Under the irradiation of high temperature and high beam He plasma at more than 5000 s, only tungsten in the range of 72 nm from top surface is transformed into fuzz structure in nanochannel thin films, while the surface of irradiated bulk tungsten alloy would be seriously eroded. The result indicated the effectively relieve thermal stress and maintain resistance to the He nucleation and "fuzz" formation behavior of nanochannel structure under high-temperature irradiation [115,116]. The previous work [112] has shown that {100} surface in tungsten might own better resistance to morphology change due to the larger binding energy.…”