Speaker
Description
Axions and axion-like particles (ALPs) are well-motivated dark matter candidates which are collectively referred to as ALPs. The Cosmic Axion Spin Precession Experiments (CASPEr) [1] is an international research program searching for ALPs using nuclear magnetic resonance (NMR) techniques. CASPEr-gradient low-field in Mainz probes the hypothetical coupling of the gradient of the ALP field to nuclear spins [2] for Compton frequencies between $1\,\mathrm{kHz}$ and $4.2\,\mathrm{MHz}$ using a tunable superconducting magnet and a detection system based on superconducting quantum interference devices (SQUIDs). To probe higher frequencies in the range $70$ to $600\,\mathrm{MHz}$ CASPEr-gradient high-field was recently installed and is currently operating in Mainz. The setups and recent experimental efforts of CASPEr-gradient are presented including a demonstration measurement with thermally-polarized sample to search for ALPs at a Compton frequency of $1.3\,\mathrm{MHz}$.
[1] D. F. J. Kimball et al. ``Overview of the Cosmic Axion Spin Precession Experiment (CASPEr)''. In: Microwave Cavities and Detectors for Axion Research. Cham: Springer International Publishing, 2020, pp. 105-121. ISBN: 978-3-030-43761-9
[2] Graham, Peter W., and Surjeet Rajendran. ``New observables for direct detection of axion dark matter.'' Physical Review D 88.3 (2013): 035023. DOI: 10.1103/PhysRevD.88.035023.
