The study of rare fundamental physics phenomena, such as double-beta decay, rare nuclear decays and dark matter, requires very low levels of background radiation in order to observe a signal. To achieve the required background levels, experiments are located deep underground as these facilities provide significant rock overburden and commensurate reduction in the cosmic ray flux and cosmic ray-spallation induced products. An overview of the sources of these backgrounds will be presented. Taking advantage of the deep underground laboratory spaces, there have been a growing number of underground measurements in other fields, including environmental monitoring, benchmarking of other physical techniques, Life Science studies in low background environments, and material selection. The exceptional sensitivity and high resolution of high-purity germanium detectors allows for very sensitive measurements using gamma-ray spectrometry. Their use has been increasing as they allow for non-destructive measurements of experiment components, which can be directly used if they meet specified background requirements. This paper will discuss the current most sensitive ultra-low background germanium detectors in operation and explain how to achieve the best level of background reduction to attain the best sensitivities. In addition, an overview of several complementary low background measurement methods will be discussed. A proposed program to cross calibrate germanium detectors at several laboratories will be described and a searchable database used to store radioactivity measurements of experimental materials will be introduced.

对罕见的基本物理现象（例如双β衰变，罕见的核衰变和暗物质）的研究需要非常低的背景辐射水平才能观察到信号。为了达到所需的背景水平，将实验设在地下深处，因为这些设施可显着覆盖岩石，并相应减少宇宙射线通量和宇宙射线飞散引起的产物。将概述这些背景的来源。利用深层的地下实验室空间，其他领域的地下测量越来越多，包括环境监测，其他物理技术的基准测试，低背景环境中的生命科学研究以及材料选择。高纯度锗探测器的出色灵敏度和高分辨率允许使用伽马射线光谱仪进行非常灵敏的测量。由于它们允许对实验组件进行无损测量，因此它们的使用在不断增加，如果它们满足指定的背景要求，则可以直接使用。本文将讨论当前运行中的最灵敏的超低本底锗探测器，并说明如何实现最佳的背景还原水平以获得最佳的灵敏性。此外，将讨论几种互补的低背景测量方法的概述。将描述在多个实验室交叉校准锗探测器的拟议程序，并将介绍用于存储实验材料放射性测量值的可搜索数据库。