Time-stamping system for nuclear physics experiments at RIKEN RIBF

A time-stamping system for nuclear physics experiments has been introduced at the RIKEN Radioactive Isotope Beam Factory. Individual trigger signals can be applied for separate data acquisition (DAQ) systems. After the measurements are complete, separately taken data are merged based on the time-stamp information. In a typical experiment, coincidence trigger signals are formed from multiple detectors to take desired events only. The time-stamping system allows the use of minimum bias triggers. Since coincidence conditions are given by software, a variety of physics events can be flexibly identified. The live time for a DAQ system is important when attempting to determine reaction cross-sections. However, the combined live time for separate DAQ systems is not clearly known because it depends not only on the DAQ dead time but also on the coincidence conditions. Using the proposed time-stamping system, all trigger timings can be acquired, so that the combined live time can be easily determined. The combined live time is also estimated using Monte Carlo simulations, and the results are compared with the directly measured values in order to assess the accuracy of the simulation.