Abstract
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.
Highlights
The study of radioactive backgrounds has been ongoing for several decades, it began in the 1950’s with the search for little-known backgrounds in materials surrounding particle accelerators to determine if those materials were activated from the accelerator itself
To accomplish this large task, a program to find cleaner materials to build the counters themselves will be required. This includes, for example, finding the raw materials such as copper and lead with even lower internal backgrounds as these will be required to better shield the current suite of experiments. One such proposed low background facility is being developed at SNOLAB which will includes its own supply of radon-reduced air to allow detector development in the underground lab
In addition it is being proposed to build a general purpose shielding
Summary
The study of radioactive backgrounds has been ongoing for several decades, it began in the 1950’s with the search for little-known backgrounds in materials surrounding particle accelerators to determine if those materials were activated from the accelerator itself. Counting facilities were developed to measure the materials and to search for lesser known backgrounds This involved building dedicated facilities with the appropriate construction materials to shield the counters from local backgrounds. The initial counting facilities were usually developed by the individual experiments as their needs arose These counters were developed into permanent facilities and improved to increase sensitivity The search for low background materials continues with a particular emphasis on the search to find materials which have low concentrations of the radioactive chain elements, 238U, 232Th, and 40K, often well below mBq kg− 1 These concentrations are below what is generally accessible by standard chemical and analytical techniques, assay methods are often performed through radiation counting or through very sensitive non radiometric techniques like mass spectrometry.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
