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Copper Electroplating for Background Suppression in the NEWS-G Experiment

Journal Article · · Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
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  1. Queen's University (Ontario)
  2. University Grenoble Alpes
  3. BATTELLE (PACIFIC NW LAB)
  4. Department of Physics, Engineering Physics & Astronomy, Queen's University, Kingston, Ontaria, Canad
  5. Department of Physics, Engineering Physics & Astronomy, Queen's University, Kingston, Ontario, Canad
  6. Chemistry & Chemical Engineering Department, Royal Miliatary College of Canada, Kingston, Ontario, C
  7. Universite Grenoble-Alpes, Modane, France
  8. University of Alberta
  9. Centre d'Etudes de Saclay, Gif-Sur-Yvette, France
  10. Universite Paris-Saclay, Gif-sur-Yvette, France
  11. SNOLAB, Lively, Ontario, Canada
  12. Queen's University, Kingston, Ontario, Canada
  13. Universite Grenoble-Alpes, Grenoble, France
  14. Royal Military College of Canada, Kingston, Ontario
  15. University of Birmingham
  16. SNOLAB
  17. Ecole des Mines de Nantes
  18. CEA
  19. Universite Paris-Saclay, Gif-sur-yvette, France
  20. Aristotle University of Thessaloniki
  21. Queen's Univeristy, Kingston, Ontario, Canada
  22. University of Tokyo
+ Show Author Affiliations
New Experiments with Spheres-Gas (NEWS-G) is a dark matter direct detection experiment that will operate at SNOLAB (Canada). Similar to other rare-event searches, the materials used in the detector construction are subject to stringent radiopurity requirements. The detector features a 140-cm diameter proportional counter comprised of two hemispheres made from commercially sourced 99.99% pure copper. Such copper is widely used in rare-event searches because it is readily available, there are no long-lived Cu radioisotopes, and levels of non-Cu radiocontaminants are generally low. However, measurements performed with a dedicated 210Po alpha counting method using an XIA detector confirmed a problematic concentration of 210Pb in bulk of the copper. To shield the proportional counter's active volume, a low-background electroforming method was adapted to the hemispherical shape to grow a 500-µm thick layer of ultra-radiopure copper to the detector's inner surface. In this paper the process is described, which was prototyped at Pacific Northwest National Laboratory (PNNL), USA, and then conducted at full scale in the Laboratoire Souterrain de Modane in France. The radiopurity of the electroplated copper was assessed through inductively coupled plasma mass spectrometry (ICP-MS). Measurements of samples from the first (second) hemisphere give 68% condence upper limits of <0.58 µBq/kg (<0.24 µBq/kg) and <0.26 µBq/kg (<0.11 µBq/kg) on the 232Th and 238U contamination levels, respectively. These results are comparable to previously reported measurements of electroformed copper produced for other rare-event searches, which were also found to have low concentration of 210Pb consistent with the background goals of the NEWS-G experiment.
Research Organization:
Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Organization:
USDOE
DOE Contract Number:
AC05-76RL01830
OSTI ID:
1734645
Report Number(s):
PNNL-SA-154978
Journal Information:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment, Journal Name: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment Vol. 988
Country of Publication:
United States
Language:
English

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