The next-generation (Stage 4) ground-based cosmic microwave background (CMB) experiment, CMB-S4, will consist of a dedicated telescope equipped with highly sensitive superconducting cameras operating at the South Pole, the high Chilean Atacama plateau, or possibly northern hemisphere sites. The camera for CMB-S4 will contain approximately an order of magnitude more detectors – each with greater sensitivity – than the current experiment.

CMB-S4 will be designed to cross critical thresholds in testing inflation, determining the number and relative masses of the neutrinos, constraining possible new light relic particles, providing precise constraints on the nature of dark energy, and testing general relativity on large scales.