Timing, Trigger and Control Systems for LHC Detectors

\\ \\At the LHC, precise bunch-crossing clock and machine orbit signals must be broadcast over distances of several km from the Prevessin Control Room to the four experiment areas and other destinations. At the LHC experiments themselves, quite extensive distribution systems are also required for the transmission of timing, trigger and control (TTC) signals to large numbers of front-end electronics controllers from a single location in the vicinity of the central trigger processor. The systems must control the detector synchronization and deliver the necessary fast signals and messages that are phased with the LHC clock, orbit or bunch structure. These include the bunch-crossing clock, level-1 trigger decisions, bunch and event numbers, as well as test signals and broadcast commands. A common solution to this TTC system requirement is expected to result in important economies of scale and permit a rationalization of the development, operational and support efforts required. LHC Common Project RD12 is developing a multi-function optoelectronic TTC system which can meet the requirements of central signal broadcasting and local distribution at the different subdetectors of the experiments. A laser transmitter, modulator, encoder, VMEbus interface and machine interface are being developed as well as a subminiature radiation-hard optical fibre connector, active device mount and photodetector/preamplifier. A radiation-hard timing receiver ASIC is being designed which will generate the full range of decoded signals for electronics controllers from a single in put and a PMC receiver module is being developed to facilitate initial applications. The system incorporates programmable coarse and fine deskew facilities to compensate for different particle flight times and detector, electronics, propagation and test generator delays. It can also transmit asynchronous slow controls and data such as individually-addressed channel enables and calibration parameters to several thousand destinations.