The SENSEI experiment sets new limits on the search for dark matter

What do digital cameras like the ones found in your phone have in common with the global search for dark matter? The answer is something called a Charged Coupled Device or CCD. The SENSEI experiment at SNOLAB uses a very sensitive type of CCD, called a skipper CCD, in its search for dark matter. 

The SENSEI experiment has been operating at SNOLAB since 2021 has recently published new results that set world-leading limits on the search for dark matter. Data was collected over seven months between 2022 and 2023 and results were published in the journal Physical Review Letters last month. SENSEI stands for, Sub-Electron-Noise Skipper-ccd Experimental Instrument and is located 2km underground at SNOLAB, Canada’s deep underground science laboratory. The experiment uses highly sensitive skipper CCDs to search for particles that have a mass below one GeV (gigaelectronvolt) – that’s less than the mass of a proton.

“SENSEI uses ultrasensitive silicon ‘skipper Charge Coupled Devices’ (skipper CCDs), which allow us to search for dark matter particles that scatter off an electron in the silicon,” said Dr. Kelly Stifter, a member of the SENSEI collaboration and a co-author of the paper. 

Such a scatter would release only a small number of electrons (approximately 1-10) from the silicon atoms in one of the pixels in the Skipper CCD. This sensitive of a measurement is possible by using Skipper CCDs – a technology that won members of the experiment a Breakthrough Prize in 2021.

To prepare for data collection at SNOLAB, the SENSEI collaboration focused on improving the sensitivity and reducing the impact of background events in the skipper CCDs. This effort has positioned the team to lead in the development of this new technology. Researchers in the SENSEI collaboration plan to increase the size of the experiment by adding more skipper CCDs to the experimental setup at SNOLAB. This will improve the sensitivity of the detector and could open the door to new discoveries. 

The search for dark matter is a coordinated global effort and discovering particles in a new dark sector would advance our understanding of matter and the universe.