${}^{225}\mathrm{Ac}$ is a valuable medical radionuclide for targeted $\alpha$ therapy, but ${}^{227}\mathrm{Ac}$ is an undesirable byproduct of an accelerator-based synthesis method under investigation. Sufficient detector sensitivity is critical for quantifying the trace impurity of ${}^{227}\mathrm{Ac}$, with the ${}^{227}\mathrm{Ac}$/${}^{225}\mathrm{Ac}$ activity ratio predicted to be approximately 0.15% by end-of-bombardment (EOB). Superconducting transition edge sensor (TES) microcalorimeters offer high resolution energy spectroscopy using the normal-to-superconducting phase transition to measure small changes in temperature. By embedding ${}^{225}\mathrm{Ac}$ production samples in a gold foil thermally coupled to a TES microcalorimeter we can measure the decay energies of the radionuclides embedded with high resolution and 100% detection efficiency. This technique, known as decay energy spectroscopy (DES), collapses several peaks from $\alpha$ decays into single Q-value peaks. In practice there are more complex factors in the interpretation of data using DES, which we will discuss herein. Using this technique we measured the EOB ${}^{227}\mathrm{Ac}$ impurity to be (0.142 ± 0.005)% for a single production sample. This demonstration has shown that DES is a useful tool for quantitative measurements of complicated spectra.

${}^{225}\mathrm{交流电}$ 是一种有价值的医用放射性核素，用于靶向 $\alpha$ 治疗，但 ${}^{227}\mathrm{交流电}$是正在研究的基于加速器的合成方法的不良副产品。足够的检测器灵敏度对于量化微量杂质至关重要${}^{227}\mathrm{交流电}$，与 ${}^{227}\mathrm{交流电}$/${}^{225}\mathrm{交流电}$到轰击结束 (EOB) 时，活动率预计约为 0.15%。超导过渡边缘传感器 (TES) 微量热仪提供高分辨率能量谱，使用法向到超导相变来测量温度的微小变化。通过嵌入${}^{225}\mathrm{交流电}$在与 TES 微量热计热耦合的金箔中生产样品，我们可以测量嵌入的放射性核素的衰变能量，具有高分辨率和 100% 检测效率。这种被称为衰变能谱 (DES) 的技术将几个峰从$\alpha$衰减为单个 Q 值峰值。在实践中，在使用 DES 解释数据时有更复杂的因素，我们将在本文中讨论。使用这种技术，我们测量了 EOB${}^{227}\mathrm{交流电}$单个生产样品的杂质为 (0.142 ± 0.005)%。该演示表明，DES 是一种用于复杂光谱定量测量的有用工具。