A Diamond Nitrogen-Vacancy Compass Referenced to the Transit Heading

A compass built from nitrogen-vacancy centres in diamond reads magnetic heading optically, with no moving parts and no magnetic material of its own. This paper computes the heading performance of a 1 cubic millimetre diamond sensor operated in the Earth's field. With a resonance linewidth of 1 MHz, a photon count rate of one million per second and a contrast of 0.18, the field noise is 198.41 nT per root hertz, which against a 45 microtesla Earth field corresponds to a heading uncertainty of 0.253 degrees per root hertz of averaging. The design pairs the diamond readout with a transit-law heading reference so that slow bias drifts can be corrected against a geometric standard. Figures are computed from the stated assumptions; the compass has not been built.