Self-supporting thin tin targets fabricated by ultra-high vacuum evaporation for heavy-ion induced reactions. (February 2020) - Sood, Arshiya
Abstract: Self-supporting thin films of 116, 118 Sn isotopes have been fabricated using ultra-high vacuum (UHV) facility at the Inter-University Accelerator Centre (IUAC), New Delhi. Owing to the requirements for fusion and quasi-elastic backscattering studies, several self-supporting thin target films with areal density ~ 250–600 μg/cm 2 were fabricated. Attempts were also made to prepare thin films by cold rolling technique, and an areal density of ~ 1.8 mg/cm 2 could be achieved after several rolling cycles. Various advanced characterization techniques viz., Rutherford Backscattering Spectrometry (RBS), Energy Dispersive X-ray Spectroscopy (EDS), Fourier Transform Infrared (FTIR) Spectroscopy and Field Emission Scanning Electron Microscopy (FE-SEM) were employed to (i) ascertain levels of trace- and heavy-impurities, if present, in the fabricated target films, (ii) determine exact thickness of the films, and (iii) study morphological changes, if any, in the films after irradiation with high energy ion beam fluence of ~ 10 15 ions/cm 2 . The characterization results manifested that negligible amount of impurities was present in the films, and they were quite stable under energetic ion-beam irradiations. The fabricated films were successfully used as targets in online nuclear physics experiments to measure quasi-elastic backscattering cross-sections in 7 Li induced reactions. Highlights: 116, 118 Sn self-supporting thin films of areal density ≈250-600 μg/cm 2 have been fabricated using ultra-high vacuum evaporation. Cold rolling technique was also attempted. An enriched metal sheet of ≈240 mg/cm 2 was rolled down to a minimum of ≈1.8 mg/cm 2 . RBS, EDS, FTIR and SEM characterizations were performed to determine thickness and purity of thin films. No heavy- and/or trace – impurities were found in the fabricated thin films even after weeks of preparation, and irradiation. Prepared thin films have been successfully used as targets in quasi-elastic backscattering experiments with 7Li beam.