Superconducting quantum detectors

Abstract:

Astronomical interest in millimetre and submillimetre wavelengths (f = 300 GHz to 1 THz) has fuelled the development of low noise high sensitivity detectors for these wavelengths. HARP (Heterodyne Array Receiver Project) will be a 16 element focal plane imaging array of heterodyne detectors for the 850 micron (325 - 375 GHz) band. Each element will consist of a mixer employing an SIS (superconductor - insulator - superconductor) tunnel junction as the non linear device. When attached to the James Clerk Maxwell Telescope in Hawaii the array will offer greatly improved mapping speeds of extended objects complementing existing bolometer detectors and planned millimetre wave aperture synthesis telescopes. This presentation will examine aspects of the SIS device physics, quasi-optics, and electromagnetic design for the HARP imaging array. Original results from computer modelling and experiments on a prototype mixer will be presented.

Abstract:

The water content in multilayers made from poly(styrenesulfonate) and poly(diallyldimethylammonium chloride) was determined using infrared spectroscopy and thermal gravimetric analysis. Under ambient conditions the polyelectrolyte multilayer contains 10-20 wt % water, which is removed by heating under dry conditions to 100 °C. FTIR comparison of multilayers with solution-precipitated polyelectrolyte complexes of the same polymers revealed that both the composition and sulfonate group environment were identical.

Abstract:

The authors report the successful operation of an antipodal finline quasi-particle SIS mixer at 230GHz. The mixer is fed by a waveguide diagonal horn and uses planar circuit technology and integrated tuning. The mixer is testd over the frequency range 213-265GHz and a receiver noise temperature of ≃60K DSB over the whole of this range is obtained. This work has shown that superconducting finline mixers have low noise and are easy to manufacture, and are therefore suitable for large-format imaging arrays.

Abstract:

We have developed an antenna for high-performance submillimetre-wave imaging arrays. The antenna comprises a corrugated horn with an off-axis paraboloidal reflector at its aperture. The corrugated horn is machined directly into two halves of a split aluminium block. This approach avoids electroforming and is compatible with E-plane circuit technology. The resulting antenna is light weight and is ideal for space applications. For compatibility with submillimetre-wave optics, the the behaviour has been calculated by using Gaussian-Hermite modes, and the integrity of the theory has been verified by modelling the behaviour of a 17GHz antenna. The manufacturing procedure has been investigated by machining and testing a horn-reflector antenna for 450-500GHz. Our next step is to extend the technique to 1THz.