Design of carbon ion stripper of a tandem accelerator for AMS radiocarbon dating

The tandem accelerator project at the Nuclear Science and Technology Research Institute (NSTRI) aims to design and construction a 1.7 MV accelerator for AMS applications. Alongside the design and construction of the high voltage power supply for the intended accelerator, the accelerating tube including the low-energy section, the stripper section, and the high-energy section is also being developed. This paper focuses specifically on the design of the stripper section for a carbon ion beam. In the design of this section, by excluding interactions involving charge states of (q, q–2) and (q, q + 2), a total of 14 interactions between charge states (q, q + 1) and (q, q–1) have been considered. After deriving the interaction cross-sections at the desired energy, the optimal geometry was introduced, and the charge exchange efficiency was calculated for different gas throughputs. At a gas throughput of 9 Standard Cubic Centimeter per Minute (SCCM), an equilibrium thickness of 2.3 × 10¹⁶ cm⁻² was achieved, which ensures charge exchange equilibrium for the formation of various carbon charge states within the designed geometry. Results indicate that for charge states + 1, +2, and + 3, the ¹⁴C/¹²C stripping ratios are 1.22, 1.01, and 0.89, while the corresponding ratios for ¹⁴C/¹³C are 1.52, 1.09, and 0.76. These variations highlight the importance of considering isotopic mass effect on stripping efficiency in AMS-based radiocarbon dating.