The development of a detection device for simultaneous measurement of energy and impact time, to be used in time-of-flight mass spectrometry, is reported. In this device, two superconducting tunnel junctions are coupled through a passive network. The first junction operates in the quasiparticle regime in order to measure the energy of a molecule impact and to act as a proportional detector. The second one operates in the Josephson regime in order to act as a fast discriminator for the impact time of a molecule impinging on the detector junction. In this way, a very accurate time determination can be achieved limited only by the intrinsic detector response, thus improving the spectrometer mass resolution. To demonstrate the feasibility of this detection scheme in mass spectrometry, calibration measurements have been carried out using a 55Fe x-ray source to simulate the molecule impact. The experimental results successfully demonstrated simultaneous detection of energy and arrival time in coincidence with photon impacts, with a time resolution limited, in practice, only by the electronics used. © 2003 American Institute of Physics.