Superconducting quantum detectors

Abstract:

In this paper we present a novel design of an antenna coupled TES direct detector for high performance applications. In particular, the design of the detector has been optimised to be suitable for the measurement of the weak B-mode signal in the CMB polarization. An important feature of this design is that it employs corrugated horn antennas for coupling the astronomical signal to the detector. This allows us to feed the telescope with a well collimated beam with low sidelobes and cross polarization. The paper contains simulations demonstrating the suitability of individual electromagnetic components to be used in the instrument.

Abstract:

The Quantum Theory of Mixing developed by Tucker provides a solid framework for understanding the behaviour of SIS mixers, and subsequent developments allow the simulation of complete mixer circuits. These methods operate, however, under the assumption of small signal levels, and so neglect the non-linear behaviour of the signal path. The non-linearity of the mixer's response to applied signals is of vital importance to the calibration of SIS receiver systems. We have previously reported(1) a procedure for calculating the full quantum behaviour of tunnel junction circuits under multiple high-level signals, allowing the accurate prediction of the saturation characteristics of SIS mixers. In this paper, we apply our procedure to both an idealized SIS mixer and one of our previously tested 700 GHz finline mixers. We find that the small signal behaviour predicted by our procedure agrees well with other simulation methods, and that the saturation properties of both of these mixers differ from that predicted by previous estimates of saturation behaviour.

Abstract:

A theoretical technique was developed for simulating the quantum-mechanical multitone behavior of superconducting tunnel junction circuits. The procedure was based on a full quantum-mechanical description of photon-assisted tunneling. It was expected to be used to model saturation in submillimeter-wave SIS mixers. SIS mixers were used extensively in submillimeter-wave astronomy.

Abstract:

The feasibility of making single-chip, superconducting detectors for submillimetre-wave astronomical inteferometry is demonstrated. An experimental device based on back-to-back corrugated horns, and back-to-back finline transitions, was fabricated. The detector was illuminated at 350 GHz, using a coherent laboratory source, and 0.6° fringes were measured.