Power supply system for the ATLAS experiment: Design specifications, implementation, test and first results

The planned upgrade of instrumentation sensitivity in the ATLAS experiment of the Large Hadron Collider (LHC), at CERN, calls for a new type of power distribution architecture. Moreover, power supplies require DC-DC power converters able to work in very hostile environment and maintaining high level of Reliability, Availability, Maintainability and Safety (denoted as RAMS requirements) during the experimental activity. Two main issues need to be discussed: first, electronic devices and equipment must operate in very high background of both charged and neutral particles and high static magnetic field and, second, the increase of the radiation background and the requirements of new front-end electronics are indeed incompatible with the current capability of the actual distribution system. The APOLLO R&D; collaboration, funded by the Italian Istituto Nazionale di Fisica Nucleare (INFN), aims to study dedicated topologies of both distribution system and DC-DC power converters and to design, build and test demonstrators, developing the needed technology for the industrialization phase. The collaboration has designed a 3kW, 280V-12V converter (MC) based on the Switch in Line architecture (SIL), a DC to DC phase-shifted converter characterized by a disposition in line of the MOSFETs with good soft switching performances, and in the last year many steps have been taken to enhance the power dissipation and the reliability and to improve the general features of the designed converter. In particular a new water heat sink was designed on the basis of TFD simulation accounting for the layout of the specific converter. Experimental activities in order to characterize both thermal and electrical features of the MC confirm the correctness of the adopted design criteria.