Injection-Detection Experiments in All Aluminum 1-D Imaging Spectrometers Based on Superconducting Tunnel Junctions

We report on a class of low temperature radiation detectors based on superconducting tunnel junctions (STJs) in which the incoming radiation is absorbed in a long superconducting strip while the readout operation occurs at the two ends of the strip, where two STJs are laterally positioned. These Distributed Read-Out Imaging Devices, or DROIDs, provide spectroscopy, 1-D imaging, single-photon sensitivity, and high quantum efficiency, all in one device. Typically these devices are realized by using Tantalum for the absorber strip and Aluminum for the two STJs. In this way the quasi-particles are created in the Tantalum and subsequently trapped in the Aluminum. As illustrated here, it is possible to fabricate a DROID using a single superconducting material. This choice gives up the trapping effect but has the advantage of eliminating the interface between different superconducting materials. Such a device combines the best quality STJs, large diffusion and lifetime values, with low energy gap for improved energy and position resolution. We report on measurements of current injection done on prototype devices, which demonstrates that STJs can serve as quasi-particle sinks and facilitate charge division in DROIDs. For sufficiently high tunneling rates, DROIDs based on a single material may be able to obtain performances comparable to DROIDs based on two materials.