The enhanced data acquisition system for the 4 pi detector CHIMERA

CHIMERA is a second generation 4 pi detector for high resolution light part icle and fragment measurements in the field of intermediate energy nuclear reactions. An enhanced data acquisition, control and trigger system has bee n developed to manage the almost 5000 electronic channels of the detector. The data acquisition system is based on a Fast Data Link (FDL) connection b etween 9U VME crates. The FDL is a highly programmable VME device. It perfo rms data readout and transfer to a destination VME CPU, the FIC8243, runnin g the real time OS9 operating system. Data read and transfer is performed b y a fast protocol (Sparse Data Scan) whose performances have been improved introducing the Chained Block Transfer mode (CBLT) technique. Data collecte d by the CPU are broadcast to analysis work-stations for on-line data analy sis and storage. All commands from and to the VME CPU are sent by socket-ba sed network protocols. Complete remote control of the electronic front-end is obtained by a system of client-server applications. A first level event selection and control during readout is made by a trigger system based on a new VME 9U board (MUSE), fully integrated with the FDL readout system.