AMS measurements of ⁴¹Ca and ⁵⁵Fe at VERA - two radionuclides of astrophysical interest

The potential for measuring the radionuclides ⁴¹Ca and ⁵⁵Fe was investigated with the 3 MV tandem accelerator at VERA. Interestingly, up to now, no applications have been published for ⁵⁵Fe using the technique of AMS. This is in strong contrast to ⁴¹Ca, which is routinely measured by medium and large tandem accelerators in various applications. Using CaF₂ samples the quantification of ⁴¹Ca down to levels of a few 10^-13 for the isotope ratio ⁴¹Ca/Ca has become possible with the use of the ΔTOF technique. Both nuclides, ⁴¹Ca and ⁵⁵Fe were found to be of interest in nuclear astrophysics. A first application of ⁴¹Ca detection at VERA is the measurement of the ⁴⁰Ca(n, γ)⁴¹Ca cross section at stellar temperatures. Similarly, of astrophysical interest is the production of ⁵⁵Fe via neutron capture on ⁵⁴Fe. To this end, different Ca and Fe blank and standard samples were investigated with the goal to establish an AMS method for ⁴¹Ca and ⁵⁵Fe measurements. Indeed, low background levels for both radionuclides, ⁴¹Ca and ⁵⁵Fe, were observed in these studies. The full separation power of VERA results in a very low detection limit, while still providing a high overall transmission.