Benjamin Knepper receives 2024 SPS Outstanding Undergraduate Research Award

August 26, 2024

Ben Knepper

UC Berkeley Undergraduate Student Benjamin Knepper


Rising undergraduate senior Benjamin Knepper has received a 2024 SPS Undergraduate Research Award for his project: Characterization and Enhancement of Dark Matter Detection Efficiency in BREAD.

Project abstract

Dark matter, constituting 85% of the mass content of the universe, remains to be experimentally observed. Particle dark matter candidates such as dark photons or axions can, however, convert into observable photons at conductive surfaces and under strong magnetic fields. This property motivates direct detection experiments to search for particle dark matter masses via their corresponding electromagnetic frequencies. The Broadband Reflector Experiment for Axion Detection (BREAD) acts like a telescope for dark matter, with an outer cylindrical barrel and inner coaxial parabolic reflector that focuses dark matter-converted photons onto a photosensor, in the frequency range of [0.01, 240] THz. The present work sought to characterize and enhance the detection efficiency in BREAD at the two extremes of this frequency range—both in InfraBREAD and GigaBREAD. InfraBREAD will search for infrared photons using a 1mm^2 single-photon counting quantum photosensor, but at this high-frequency scale photons are emitted incoherently which results in a problem: the focal spot becomes smeared across an area larger than the detector, which experimental misalignments can exacerbate. This first project performed ray-tracing simulations of novel optical configurations of lenses and reflectors to refocus the smeared signal even under millimeter-scale displacement shifts. One configuration with parabolic reflector optics improved the average detection efficiency by 10%, with a maximal 55% increase in one displaced region. GigaBREAD, by contrast, uses a horn antenna photosensor to search for gigahertz frequency photons, which are emitted coherently and form resonant standing waves between the inner reflector and detector. This second project measured the blackbody thermal radiation spectrum of the GigaBREAD apparatus to both calculate its system noise temperature background and confirm sensitivity to detecting gigahertz resonances for its first-ever data taking run. Subsequent radio-frequency measurements and signal processing analyses then led to the world-leading dark photon exclusion limit of 10^-12 in [10.7, 12.5] GHz.

Project leader: Stefan Knirck, Andrew Sonnenschein

Benjamin's bio

I am a rising senior at the University of California, Berkeley, majoring in physics along with philosophy and mathematics. During a gap year prior to transferring to Berkeley, I conducted full-time research at Fermilab and the University of Chicago Enrico Fermi Institute on the BREAD experiment, which searches for particle candidates of dark matter such as axions and dark photons. My research interests currently lie at the intersections of particle physics and quantum information science (QIS), particularly in the realm of quantum sensing. Dark matter remains one of the most elusive mysteries in contemporary physics, and one promising avenue for enhancing detection efficiency in experiments like BREAD will be from precision quantum measurements. I am excited to be involved in harnessing advancements in QIS from the so-called "second quantum revolution" to not only probe new physics beyond the Standard Model like dark matter, but also investigate the nature of quantum theory in its relation to other fundamental laws, and I am looking forward to continue exploring these topics in a PhD. SPS has been a vital component of my physics journey and transfer to Berkeley, as I have been able to get involved with three chapters across the country and engage with a national community of like-minded peers. I am now currently working at Lawrence Berkeley Lab on quantum metrology, and when not doing physics, I enjoy hiking, reading philosophy, and playing blues piano.

Society of Physics Students