Object detection with an alkali-metal spin maser

We present magnetic induction tomography measurements performed with a radio-frequency atomic magnetometer operating in the spin maser mode. We discuss different regimes of spin maser operation that are defined by the gain within the system's feedback, i.e., below threshold, unsaturated, and saturated gain. Two configurations are explored: first, where an rf field continuously drives the spin maser operation and the object's presence changes the gain in the system's feedback loop, and the second, where the spin maser operation is triggered and sustained directly by the object response. The advantages and disadvantages of each configuration are discussed in the context of object detection.