Presentation Information
[PPS12-P10]Toward titanium isotopic analysis of presolar SiC using the laser post-ionization SNMS
*Kei Sato1, Kentaro Terada1, Kohei Fukuda1, Shigeru Uzita1, Hiromu Shinozaki1, Michisato Toyoda1 (1.The University of Osaka)
Keywords:
presolar grain,isotope anomaly,meteorite,SNMS
Primitive meteorites contain micrometer-scale grains that exhibit large isotopic anomalies compared with the average Solar System composition. These grains are referred to as presolar grains, and their isotopic ratios reflect nucleosynthetic processes in stellar progenitors of the Solar System. Information on these processes can be obtained through isotopic analyses of trace elements, and the results are compared with predictions from nuclear physics and stellar evolution models.
The University of Osaka has developed the laser post-ionization Secondary Neutral Mass Spectrometer (SNMS). In this instrument, a Ga ion beam with a minimum beam diameter of 4 nm is used to irradiate the sample, thereby sputtering neutral particles. By post-ionizing these neutral particles with a high-intensity femtosecond laser at a power density of 1014-1015 W/cm2, the ion yield was increased by more than 10000 (Terada et al., 2017). For mass separation, a multi-turn time-of-flight mass spectrometer(MULTUM) is employed, and by controlling the number of cycles, a high mass resolving power of several tens of thousands can be achieved.
In this study, we aimed to analyze Ti in presolar SiC and worked to optimize the instrument. Analysis of a standard sample showed that, at 81-85 turns, a mass resolving power (FWHM) of approximately 17,000 was achieved, allowing the identification of the five stable isotopes of Ti. Preliminary results show that the present configuration yields an instrumental mass fractionation (IMF) of 220-250‰/AMU. The detection limit for Ti was estimated to be on the order of a few ppm, indicating that Ti concentrations of 40 ppm or higher, as reported by Gyngard et al. (2018), are within the detectable range. Future work will focus on improving the mass resolving power and evaluating the characteristics of IMF to further optimize the measurement conditions, to achieve direct determination of Ti isotope ratios in presolar SiC.
The University of Osaka has developed the laser post-ionization Secondary Neutral Mass Spectrometer (SNMS). In this instrument, a Ga ion beam with a minimum beam diameter of 4 nm is used to irradiate the sample, thereby sputtering neutral particles. By post-ionizing these neutral particles with a high-intensity femtosecond laser at a power density of 1014-1015 W/cm2, the ion yield was increased by more than 10000 (Terada et al., 2017). For mass separation, a multi-turn time-of-flight mass spectrometer(MULTUM) is employed, and by controlling the number of cycles, a high mass resolving power of several tens of thousands can be achieved.
In this study, we aimed to analyze Ti in presolar SiC and worked to optimize the instrument. Analysis of a standard sample showed that, at 81-85 turns, a mass resolving power (FWHM) of approximately 17,000 was achieved, allowing the identification of the five stable isotopes of Ti. Preliminary results show that the present configuration yields an instrumental mass fractionation (IMF) of 220-250‰/AMU. The detection limit for Ti was estimated to be on the order of a few ppm, indicating that Ti concentrations of 40 ppm or higher, as reported by Gyngard et al. (2018), are within the detectable range. Future work will focus on improving the mass resolving power and evaluating the characteristics of IMF to further optimize the measurement conditions, to achieve direct determination of Ti isotope ratios in presolar SiC.