Superconducting quantum detectors

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.

Abstract:

We present a closed-form expression for the the input impedance of a microstrip probe in a rectangular waveguide. The probe extends only part way across the waveguide and is therefore compatible with RF components that require an open circuit at low frequencies. Our analysis is based on the spectral-domain method and is able to take into account the orientation of the antenna with respect to the direction of propagation. We have examined the validity of our model by carrying out extensive impedance measurements at 5GHz. In those cases where the probe did not extend more than half way across the waveguide, excellent agreement was obtained. We show that the bandwidth of a probe that stretches only part way cross the waveguide is very much greater than the bandwidth of a probe that stretches all of the way across the waveguide and that is earthed at both ends. Moreover, the input resistance is lower and more suited to submillimetre-wave detectors such as SIS tunnel junctions. Our expression suggests that it should be possible to develop low-impedance, wideband probes for nearly double-height waveguide, and this implies that the upper frequency limit to which probes and waveguides can be manufactured can be extended well into the THz frequency range. A related, and often neglected consideration, is that the ohmic loss associated with an oversized waveguide is very much smaller than the ohmic loss associated with a reduced-height waveguide. © 1996 Plenum Publishing Corporation.

Abstract:

We compare two techniques for calculating the loss of millimetre wave and submillimetre wave microstrip transmission line. The first method is based on conformal transformations and the second method is based on spectral domain analysis. The calculation of loss, through the spectral domain technique, is made possible by removing the current singularities from the path of integration and defining an effective width, based on loss. We use our technique to predict the behaviour of miniature submillimetre wave superconducting microstrip transmission line.