engleski

Opportunities for ion track studies at small and medium size accelerator facilities

Ion tracks can be produced by swift heavy ions only if the density of the deposited energy exceeds a certain, material dependent critical value. Otherwise, the deposited energy simply dissipates away without altering the material. Therefore, thresholds for ion track formation are a prominent feature investigated in many swift heavy ion irradiation studies. The values of the thresholds can vary a lot between different materials, and for thorough ion track studies, very high-energy swift heavy ions have to be used. In the present contribution, we present several examples how the accelerator facility at the Ruđer Bošković Institute in Zagreb has been used for ion track studies. These examples will illustrate two strategies making small and medium accelerator facilities well suited for this line of research. First, the threshold for ion track formation depends on the electronic stopping power that is a highly nonlinear function of the total kinetic energy of the swift heavy ion. Therefore, investigations of the ion track formation close to the threshold can be outsourced to smaller accelerator facilities, thus saving considerably on beamtimes at large facilities. Additionally, thresholds can be lowered in several ways, for example, by applying grazing incidence ion irradiation [1, 2]. Also, defects introduced into the material via low energy irradiation can reduce the threshold for ion track formation [2]. Other thermally driven processes like assembly and modification of quantum dot lattices can require only moderate stopping powers [3]. Second, ion beam analysis of materials is in widespread use at the small and medium sized accelerator facilities. Some of these techniques are sensitive to the amount of defects in the material, like RBS/c and ionoluminiscence. Other techniques, like high resolution PIXE can provide information about early stages of ion track formation. Here we present several examples how these techniques can be used advantageously for in situ ion track studies [4]. We also present first in situ RBS/c results obtained from our dual-beam end station.

ion track ; swift heavy ion ; RBS/c ; HR-PIXE ; ToF-ERDA

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