Development of the Johns Hopkins Xylophone Bar Magnetometer

Abstract : A novel xylophone resonating bar magnetometer, invented by APL's Research and Technology Development Center, is being developed in collaboration with the Space Department into a compact, high-sensitivity, wide dynamic range sensor suitable for space physics applications. The magnetometer's principles of operation are presented and are demonstrated in experimental situations. The sensor uses the Lorentz force and the xylophone bar's mechanical resonance to yield subnanotesla sensitivity. This resonance technique offers large mechanical gains at the expense of bandwidth (typically a few hertz). However, the device can be used as a mixer to detect alternating magnetic fields. This capability is demonstrated at low frequencies (a few hertz) and at radio frequencies (a few megahertz). The sensor incorporates no magnetic materials and, therefore, can be used to detect small fields while rejecting large out-of-band signals. The resonator's temperature sensitivity is mitigated using feedback. The device is in an early engineering prototype stage. Eventually, using micro-machining and chip-on-board techniques, it is expected to be implemented as a "magnetometer on a chip."