Lemer Pax and SNOLAB: Act II before the underground installation

In late December 2019, Lemer Pax delivered an ultra-low background noise shielding structure to the Canadien Super CDMS (Super Cryogenic Dark Matter Search) Snolab project. The scientific focus of this project revolves around astroparticle physics, particularly neutrinos and dark matter. Now, in a continuation of this transatlantic partnership, Lemer Pax is providing a new 10-ton shielding structure.

Crafted from ultra-pure, multilayer materials—comprising stainless steel, very low-activity lead, and copper—the shielding was produced and assembled under stringent environmental and particle conditions. These measures serve to minimize the risks of contamination and external pollution.

This shielding structure is designed to protect two high-purity, broad-energy Germanium (BEGe) detectors from gamma rays. Similar to its predecessor, the shielding structure will be installed underground, two kilometres deep within a mine in Sudbury, Ontario.

The gamma rays to be stopped originate primarily from the natural radiation emitted by the rock and concrete surrounding the mine walls. However, because the detectors are installed deep within the earth, the impact of high energy cosmic ray particles is negligible. Consequently, the detectors boast high sensitivity due to extremely low environmental background noise.

Aside from protecting against coincident gamma ray events, this shield, crafted from ultra-pure materials, will enable researchers to detect any accidental release of radioactivity from a nuclear power plant. This is made possible through the samples provided by Health Canada, as part of the country’s commitment to the Comprehensive Nuclear-Test-Ban Treaty. Furthermore, the project includes additional studies on wildlife to accurately quantify the long-term accumulation of radioactivity in organisms.

This marks the second collaboration between Lemer Pax and the SNOLAB scientific program. In 2019, Lemer Pax delivered a low-background noise shielding structure, composed of 100 tonnes of ultra-pure materials. It featured neutron shielding in polyethylene, gamma shielding using over 4200 lead bricks, and an aluminium radon barrier, all mounted on a seismic platform to prevent damage from seismic events.

The project presented a significant challenge at the time for Lemer Pax, prompting the company to build a large 120m² cleanroom (class 1000 – FED STD 209 E or ISO 7), according to ISO 14644-1 controlled environments. This investment was essential to meet the stringent cleanliness requirements of the North American client, as dictated by the Snolab’s class 2000 standards.

In this impressive project, Lemer Pax once again meticulously adhered to stringent specifications, meeting deadlines and demonstrating the required high-level engineering and logistics expertise. They implemented cleanliness and packaging protocols, including three heat-sealed plastic layers for road and maritime transportation, ensuring the cleanliness of each component of the shielding until its final placement.