Fabrication of isotopic and natural carbon foils by thermal cracking method and some issues

Isotopic and natural carbon foils made by thermal cracking method are used for various purposes in nuclear physics experiments. An apparatus equipped with an oil free vacuum pumping system has been constructed to produce such foils on a resistively heated metallic Ta filament by the thermal cracking method. Properties of the foils such as accessible thickness and area, uniformity, purity and yield in the foil preparation were investigated. We also investigated the following issue during the foil production; when the Ta filament temperature was decreased after the cracking process, the cracked layer sometimes broke into pieces from the filament. Eventually, we could successfully fabricate enriched isotopic ¹²C foils and natural carbon foils with thicknesses from 0.2 to 5 mg/cm² and with a dimension of 20 × 20 mm² or even larger. (author)