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Nuclear and Elementary Beam Monitoring

The acceptance of the VMEbus standard as a common hardware platform for the electron and proton accelerators motivated a modular approach in electronics design, where the acquisition and digitization of monitor signals is done in customized front-end electronics. Digital data processing, analysis and transfer to the control system as well as data distribution for feedback applications is accomplished by a 6U VMEbus board as a common digital processing and communication platform. Its core consists of twoVirtex-II Pro FPGAs (with two PowerPCs each) and RAM. The FPGAs can acquire and process measurement data from the VMEbus P0/P2 connectors or from two application-dependent PMC mezzanine modules. Two 2 GBaud fiber optics transceivers may also be used to acquire or distribute measurement data.

Applications include digital beam position monitoring and current monitors for proton beams, data processing for a muon decay experiment, and general beam diagnostics as well as global feedback control at SLS accelerators and beamlines. In the application for the cyclotron ring the challenge for the electronics is that the beam may be in continuous operation for several months. The cyclotron ring is using magnets weighing about 2000 metric tons. The VMEbus systemhas to work without errors during that period. The control algorithm would dump (stop) the high-energy beam in case of error, wasting an enormous amount of time, effort and money if this would happen. Therefore the redundant VMEbus boards are made to conform to the board level live insertion standard for hot swap operations.

Photo courtesy of Paul Scherrer Institute, Switzerland, www.psi.ch