NASA technologists have developed a novel, superconducting transition edge sensor (TES). Such TES devices are thermometers that are widely used for particle detection, e.g. X-rays, infrared photons, atoms, molecules, etc. Energy resolution is chiefly important in superconducting transition edge sensors to function as imaging spectrometers. For optimal energy resolution, it is necessary to control the superconducting transition temperature for the device.
The new design presented here provides immediate improvement to the design and fabrication procedure of existing TES fabrication processing, producing devices that can meet optimal superconducting transition temperature values and improve yield. Additionally, this new method provides the ability to make sensors of much smaller size and with improved fabrication simplicity, reliability, and reproducibility. The novel design also allows for the use of simple materials not previously usable as TESs.
NASA technologists have developed several devices using this TES design. For example, innovators at NASA’s Goddard Space Flight Center have implemented an integrated system that defines the frequency response for dual-polarized microwave sensors used in observation of the cosmic microwave background (CMB) to probe the evolution of the early universe. Precision measurement of the polarization of the CMB enables a direct test for cosmic inflation. Cosmological observations have hinted that early in its history, the universe experienced a brief period of rapid expansion called inflation that is believed to be responsible for the flatness of the universe and the origin of structure. If inflation occurred, it would have produced a gravitational wave background that is evidenced by a small but distinct polarized signature on the cosmic microwave background.
The detector for CMB polarization measurements uses large-format arrays of background-limited detectors in the form of feedhorn-coupled, TES-based sensors. Each linear orthogonal polarization from the feedhorn is coupled to a superconducting microstrip line via a symmetric planar orthomode transducer (OMT). The symmetric OMT design allows for highly symmetric beams with low cross-polarization over a wide bandwidth. In addition, this architecture enables a single microstrip filter to define the passband for each polarization.