Dual-detector for simultaneous time and energy detection

The development of a dual-detector device for simultaneous measurement of energy and impact time is reported. In this device two superconducting tunnel junctions are coupled through a passive network. The first junction operates in the quasi-particle regime in order to measure the energy of the particle as a proportional detector. The second one operates in the Josephson regime as a fast discriminator for the impact time of the particle impinging on the first detector junction. In this way a very accurate time determination can be achieved limited only by the intrinsic detector response. This device can be of particular interest in time of flight mass spectrometry of macromolecules where time resolution i.e. mass resolution is an important issue. The feasibility of the detector is demonstrated through simultaneous time and energy measurements of 6 keV X-rays; time resolution is limited, in practice, only by the electronics used. A model of the detector is presented and numerical simulations show good correspondence with experimental data.