High-resolution imaging by superconducting delay-line detector using 30ps operating readout circuit

A current-biased kinetic inductance detector CB-KID was proposed to observe an image of hot spots produced local stimuli on the orthogonal XY meanderlines. Under pulsed neutrons, the CB-KID system has two functions, i.e., not only as a delay-line neutron transmission imager (Role-I) but also as a time-of-flight-spectroscopy instrument (Role-II). When CB-KID operated with a time-to-digital convertor (TDC) of 1-ns temporal resolution with the Kalliope-I readout system, an unsolved issue was that we cannot specify a hot-spot position at a precision of a meander pitch 1.5 μm. A signal velocity inside the detector is very fast as ∼20% of the light velocity enough to allow signal propagation over a longer distance more than several pitches during 1 ns. We developed a new Kalliope-II circuit equipping with a high-resolution TDC (HR-TDC) and a front-end main circuit for continuous readout data acquisition (DAQ) system (AMANEQ) working at a 30-ps temporal resolution. Not only a timestamp t rise at the threshold but also a time-over-threshold (ToT) τ acquired at 30 ps temporal resolution enable us to conduct a delay-time (δ) correction of timestamps t rise of events to yield a transmission image with high contrast. The pixel size of the Kalliope-II imager reached down to 1.5 μm×1.5 μm. It is apparent that the CB-KID sensor works to detect various sorts of stimuli. Unlike other superconducting detectors, CB-KID realized an untrodden 100,000,000-pixel camera over the 15 mm×15 mm area.