Status of CASPEr-gradient and latest spin-noise measurement results

Janos Adam, Samer Afach, Deniz Aybas, Hendrik Bekker, John W. Blanchard, Emmy Blumenthal, Dmitry Budker, Gary P. Centers, Martin Engler, Nataniel Leigh Figueroa,

Antoine Garcon, Peter W. Graham, Alexander V. Gramolin, Dorian Johnson, Derek F. Jackson Kimball, Annalies Kleyheeg, Matthew Lawson, Haosu Luo, Hamdi Mani,

Philip Mauskopf, Surjeet Rajendran, Marina Gil Sendra, Alexander O. Sushkov,  Anam Toaha, Tao Wang, Arne Wickenbrock, Teng Wu and Yuzhe Zhang

 

The cosmic axion spin precession experiment (CASPEr) is a nuclear magnetic resonance experiment to search for axion and axion-like particles which could make up the dark

matter present in the universe. The discovery of dark matter would be a breakthrough in particle physics, astrophysics and cosmology. Due to the pseudoscalar nature and light mass of axions they can be treated as a field that can exert a time-varying torque on nuclear spins either directly or through the generation of an oscillating nuclear electric dipole moment.

In CASPEr-grad, a sample of nuclear spins is placed in a magnetic field which is tunable to a wide range of Larmor frequencies. When the Larmor frequency approaches the Compton frequency of the axion, a magnetization will build up which we intend to detect using superconducting quantum interference device (SQUIDs). We are currently characterizing the performance of the setup and investigating nuclear spin-projection noise. Our aim is to determine the spin-noise spectra of different molecular species and we will show the current state of this part of the experiment.