Re-entrant ionization chambers (ICs) are essential to radionuclide metrology and nuclear medicine for maintaining standards and measuring half-lives. The requirements of top-level metrology demand that systems must be precise and stable to 0.1 % over many years, and linear from 10⁻¹⁴ A to 10⁻⁸ A. Thus, laboratories depend on bespoke current measurement systems and often rely on sealed sources to generate reference currents. To maintain and improve present capabilities, metrologists need to overcome two looming challenges: ageing electronics and decreasing availability of sealed sources. Possible solutions using Ultrastable Low-Noise Current Amplifiers (ULCAs), resistive-feedback electrometers, and (quantum) single-electron pumps are reviewed. Broader discussions of IC design and methodology are discussed. ULCAs show promise and resistive-feedback systems which take advantage of standard resistor calibrations offer an alternative.

折返电离室（IC）对于放射性核素计量学和核医学对于维持标准和测量半衰期至关重要。顶级计量要求要求系统必须在多年内精确且稳定至0.1％，并且线性范围为10 ^-14 A至10 ^-8答：因此，实验室依赖于定制的电流测量系统，并且经常依赖于密封源来生成参考电流。为了维持和提高现有能力，计量学家需要克服两个迫在眉睫的挑战：电子设备老化和密封源可用性下降。回顾了使用超稳定低噪声电流放大器（ULCA），电阻反馈静电计和（量子）单电子泵的可能解决方案。讨论了有关IC设计和方法的更广泛讨论。ULCA显示了希望，利用标准电阻器校准的电阻反馈系统提供了替代方案。