The GREAT triggerless total data readout method

Recoil decay tagging (RDT) is a very powerful method for the spectroscopy o f exotic nuclei. RDT is a delayed coincidence technique between detectors u sually at the target position and at the focal plane of a spectrometer. Suc h measurements are often limited by dead time. This paper describes a novel triggerless data acquisition method, which is being developed for the gamm a recoil electron alpha tagging (GREAT) spectrometer, that overcomes this l imitation by virtually eliminating dead time. Our solution is a total data readout (TDR) method where all channels run in dependently and,are associated in software to reconstruct events. The TDR m ethod allows all the data from both target position and focal plane to be c ollected with practically no dead-time losses. Each data word is associated with a timestamp, generated from a global 100-MHz clock. Events are then r econstructed in real time in the event builder using temporal and spatial a ssociations defined by the physics of the experiment.