Low Background Counting Facility

At SNOLAB, we have developed a radon emanation counting system to study the radon (²²²Rn) emanation rate of different materials used in the construction of low-background and rare event search detectors. This system consists of low-radioactivity acrylic emanation chamber, a radon transfer board, and a low-background scintillation (ZnS) Lucas cell.

   The radon transfer board includes a trapping mechanism for the effective
  transfer of radon from the sample in the emanation chamber into the
  detection device. The sample is wiped with lint-free wipes using ultra-pure
  water in order to remove the surface dust. The Sample is then placed in the
  emanation chamber, flushed with boil-off nitrogen, evacuated, and allowed to
  out-gas in the chamber for a period of approxuimately two weeks. The
  trapping mechanism utilizes a primary U-shaped trap and a stainless steel
  coiled secondary trap in series.


This newly developed Rn board system has two primary traps: bronze wool and chromosorb. These trapping materials have high effective surface area, hence obtaining a much higher efficiency. The 1/8-inch secondary trap has a SS wire inserted to further reduce the volume and hence improve radon transfer efficiency.

  The primary trap is cooled with liquid nitrogen and the radon from the   emanation chamber is swept into the primary trap. The primary trap is
  then heated and the secondary trap is cooled with liquid nitrogen.

  The radon is then transferred from the primary trap to the secondary trap via
  cryo-pumping. Finally, the secondary trap is heated and radon is swept into
  the Lucas cell by volume sharing. The Lucas cell is then counted for alphas
  using a Photomultiplier tube (PMT) to obtain the ²²²Rn emanation rate
  of the material in question.


Please visit the Assay Request Form page to request for Radon emanation counting services.

SNOLAB currently operates low background facilities in the SNOLAB surface laboratories and in the deep underground laboratory at the 6800 ft level (6000 m.w.e.) of the Creighton Mine, which is located near Sudbury, Ontario, Canada.