21st Patras Workshop on Axions, WIMPs and WISPs

Magnetically Transduced Gravitational wave Inertial detector (MAGI) for the Search for High Frequency Gravitational Waves and Axions

Not scheduled

20m

University of Western Australia

Student/ECR Presentation

Speaker

Sonali Parashar

Description

The Magnetically Transduced Gravitational-Wave Inertial Detector (MAGI) is a broadband experiment that uses a large static magnetic-field gradient generated within a superconducting magnet. The inertial pickup element operates in the free-mass regime [1], and its motion is measured inductively using a superconducting pickup loop coupled to either a superconducting quantum interference device (SQUID) or a travelling-wave parametric amplifier (TWPA). MAGI is designed to search for both high-frequency gravitational waves and axion dark matter over an approximate frequency range of $1$-$500~\mathrm{MHz}$. The detector may be configured for these complementary searches by positioning the pickup coil either in the region of maximum magnetic-field gradient, which optimises its response to gravitational-wave-induced inertial motion, or in position of maximum magnetic-field, which is favourable for detecting axion-induced electromagnetic signals. The detector sensitivity depends on the pickup-loop area and geometry, magnetic-field gradient, transformer coupling, SQUID or TWPA noise, mechanical back-action, fabrication imperfections, and thermal and suspension noise. For a magnetic-field gradient of $\partial B/\partial z=1~\mathrm{T\,cm^{-1}}$, a pickup-coil radius of $3~\mathrm{cm}$, a SQUID inductance of $1~\mathrm{nH}$, a mutual inductance of $10~\mathrm{nH}$, and an inertial pickup-coil mass of $1~\mathrm{g}$, the estimated standard quantum-limited strain sensitivity is approximately $\sqrt{S_h^{\mathrm{SQL}}}=10^{-21}/\sqrt{\mathrm{Hz}}$. With currently available SQUID-based readout, the projected strain sensitivity is approximately $\sqrt{S_h}=10^{-19}/\sqrt{\mathrm{Hz}}$ at millikelvin temperatures. For axion dark-matter searches, MAGI targets masses near $0.1~\mu\mathrm{eV}$, with the full frequency range corresponding approximately to axion masses from $4~\mathrm{neV}$ to $2~\mu\mathrm{eV}$. The long-term objective is to reach an axion-photon coupling sensitivity of order $g_{a\gamma\gamma}\sim10^{-18}$-$10^{-19}~\mathrm{GeV}^{-1}$, comparable to the sensitivity targeted by broadband experiments such as DMRadio and SLIC [2-4].

[1] V. Domcke, S. A. Ellis, and N. L. Rodd, Physical Review Letters 134, 231401 (2025).

[2] N. Crisosto, P. Sikivie, N. Sullivan, D. Tanner, J. Yang, and G. Rybka, Physical Review Letters 124, 241101 (2020).

[3] B. T. McAllister, A. Quiskamp, C. A. O’Hare, P. Altin, E. N. Ivanov, M. Goryachev, and M. E. Tobar, Annalender Physik 536, 2200622 (2024).

[4] V. Ankel, C. Bartram, J. Begin, C. Bell, S. Chaudhuri, H.M. Cho, J. Corbin, W. Craddock, S. Cuadra, A. Droster, et al., arXiv preprint arXiv:2604.16602 (2026).