Colloquium
Department of Physics, NCU
Experimental efforts on axion search via haloscope in Taiwan
Prof. Yung-Fu Chen
Department of Physics, NCU
Date 2021.03.16 (Tue)
Place S4-625
Time 14:00-16:00
Abstract: Axion particle is hypothesized for solving CP symmetry preserving problem in the strong interaction, and also considered as a promising candidate for dark matter halo. However, owing to its feeble interaction to SM particles and its indecisive mass, the existence of axion is yet not confirmed experimentally. Nevertheless, via a two-photon coupling process, axions in a static magnetic field are predicted to convert to equal-energy photons, which may be accumulated in a cavity with matched resonant frequency and subsequently be detected. To date it is the only detection scheme sensitive to QCD prediction limit in the astrophysically/cosmologically preferred axion mass range of 1–1000 μeV, corresponding to converted photons in the rf band. The sensitivity of this haloscope-type search is related to detection volume, rf cavity quality, static magnetic-field strength, measurement noise, and measurement time. Therefore, the challenges of this narrow-band search scheme involve tunable high-quality rf cavity design, low-noise rf amplifier and readout development, high magnetic-field and cryogenic engineering, search scheme optimization, control- and measurement-system integration, and massive data analysis. Several groups with different expertise in Taiwan team up for haloscope-type axion search in 4-10 GHz microwave band. Importantly, the development of quantum-limited microwave amplifier and readout is also highly relevant to superconducting quantum technology. In this talk, I will present the main idea and the key components for such experimental search in this range, as well as our progresses so far. Finally, I will give an optimistic search schedule based on the expected developments of the required search components.