OBAVIJEST
TONI DUNATOV
održat će znanstveni kolokvij (doktorski seminar) iz Nuklearne fizike pod naslovom
Unwanted effects in ion irradiation of fusion materials
With the lack of an experimental fusion neutron source, ion irradiation can be used to emulate the neutron radiation effects on candidate fusion materials. Though there is significant difference between the fundamental physics valuable results can still be obtained if care is taken during the experiment. We have studied two potential issues when carrying out such experiments: carbon contamination and ion beam scanning effects.
Carbon contamination is the phenomenon of carbon incorporation into the surface of the sample during an experiment. When irradiating reactive alloys such as steels this can significantly alter the chemical composition and therefore the studied microstructure of the material. We applied several contamination mitigation techniques and profiled the carbon composition of samples by SIMS, NRA and TOF-ERDA. It was found that the source of the effect is the residual vacuum of the chamber and that it can be reduced to negligible quantities.
Ion beam scanning is often used during irradiations to homogenize the beam dose over the irradiation area. On a microscopic level this has the effect of pulsing of the dose, with a sharp increase in dose rate, followed by a long anneal time. Differences in the sample microstructure are observed between the constant and scanned beam modes. Conducting a TEM study with several scanning frequencies and beam shapes we find differences in the microstructure. The hypothesis that high-frequency scanning approaches the constant beam case is not true when scanning a narrow beam spot and in fact, strange void formation is found in this case. The results are explained by a simple model based on dose rate theory which finds that short beam-on periods are in the non-equilibrium state. The samples irradiated with a wider scanned beam are closer to the constant beam case and it is therefore concluded that the “beam wobbling” suggestion from the literature is more effective for emulation of neutron radiation.
Seminar će se održati u srijedu 13. studenog 2024. godine u 13:00 sati u predavaonici F-201 na Fizičkom odsjeku Prirodoslovno-matematičkog fakulteta.
Pozivaju se studenti doktorskog studija Fizike, smjer Nuklearna fizika da prisustvuju seminaru, ako nisu spriječeni.
Voditelj smjera
Prof. dr. sc. Damir Bosnar, v. r.
Pristupačnost
