A new figure of merit for planar SQUID gradiometers and magnetometers

There has recently been significant progress in the sensitivity of SQUID planar gradiometers and magnetometers. Usually, their performance is expressed in terms of the associated field noise spectrum together with a description of the geometry of the device. This is not a straightforward combination and poses a difficult task if one wants to assess the overall performance of the device and to compare different designs. To address these issues, we propose a new figure of merit based on spatial frequency features of the gradiometer. It consists of obtaining its spatial frequency response and extracting from it relevant parameters such as magnitude and bandwidth. An assessment of different gradiometer designs is made.