Abstract: A passive mm-wave imager comprises an optical immersion lens arrangement which is illuminated by front end optics and an array of detectors (12a) to (12d) located in the focal plane of the immersion lens arrangement. The detectors comprise antennae coupled high temperature superconductor weak links, in particular C-axis cross-over or step microbridges.

Abstract: A passive mm-wave imager comprises an optical immersion lens arrangement which is illuminated by front end optics and an array of direct detectors (12a) to (12d) located in the focal plane of the immersion lens arrangement. The detectors comprise antennae coupled high temperature superconductor weak links, in particular C-axis cross-over or step microbridges.

Abstract: A method of tuning a microwave or RF circuit is given which comprises the steps of taking a microwave or RF circuit (20) located in a casing (57), said casing comprising a housing portion (32) and a window portion (50), said window portion (50) being substantially conducting at microwave/RF frequencies, and comprising at least one area that is substantially transparent at optical frequencies and, directing a laser beam (66) onto said microwave or RF circuit through said window portion (50) so as to alter the material properties of selected areas of said microwave or RF circuit (20). This permits microwave and RF circuits, including microwave filters, to be tuned without the need for tuning screws.

Abstract: A gradiometer for measuring properties of a magnetic field and in particular, for measuring magnetic field gradient components, comprising at least two magnetic sensors wherein at least two of the magnetic sensors are arranged to sense the magnetic field component in substantially the same direction. The magnetic sensors may be super conducting quantum interference device (SQUID) magnetometers, Hall probes, flux gates or magneto-resistive magnetometers. The gradiometer also includes a computer processor loaded with an adaptive signal-processing algorithm, for performing adaptive signal balancing of the magnetometer outputs. In a preferred embodiment the gradiometer may comprise at least eight magnetometers in a three-dimensional arrangement, and a set of three orthogonal global feedback coils, one for each direction x, y, z, such that the five independent magnetic field gradient components may be measured. The gradiometer may also be used to measure second or higher order magnetic field gradient components.