Data acquisition system for MEGHA

A multi-channel data acquisition system has been commissioned for the Charissa “MEGHA” detector array. It is designed to read multiparameter events where there are many potential channels (320) but where only a fraction of these are active in any typical event. Custom-built pre- and main amplifiers process the amplitude (energy) signal from each detector and the system records both amplitude and time of arrival for each signal within an event. The signal amplitude is converted to time using the standard Wilkinson technique and then combined with its time of arrival into a single time trace. These traces are converted by multi-hit TDCs, which only convert the active channels and thus reduce the processing load. Additional custom-built CAMAC modules organise the TDC output into a suitable form for storage and transmission to a network of processor terminals over standard ethernet. This paper presents a description of the data acquisition system from preamplifier through to final storage in a VME-based system and subsequent distribution to a network of Sun terminals over ethernet. The system performance is illustrated with results from heavy-ion elastic scattering recorded with position sensitive strip detectors.