Custom-made power for ATLAS

A small team of engineers and technicians has recently finished the design of power supplies specially tailored to working in the demanding environment of the ATLAS Tile Calorimeter. Mass production of the units has now begun.

Power supplies are an important component of any particle detector. In ATLAS, as in the other experiments at the Large Hadron Collider, it is not easy to use standard, 'off the shelf' power supplies; they must survive radiation, tolerate magnetic fields, and satisfy limited space and water-cooling constraints.

For the ATLAS Tile Calorimeter, these constraints all proved challenging for the engineers designing the power supplies. The aim was to produce a universal power module in terms of input/output voltage, delivered power and cooling, for general use in a radiation environment. The result is a distributed low-voltage power supply (LVPS) system designed to survive a total integrated radiation dose of 40 krads and magnetic fields higher than 0.2 tesla, and delivering over 100 kW of electric power to the calorimeter. The system consists of many components but the main units are 256 boxes - the LV BOX - deployed around the Tile Calorimeter close to its data acquisition electronics.

The LV BOX is based on a 'brick' - the key element of the LVPS system. The custom-made bricks are basically isolated switching DC-DC converters with a maximum output power of 150 W, which have been designed to be radiation and magnetic field tolerant. They also have a further advantage, as Ivan Hruska, the electronic design engineer who has led the project since 2001, explains: 'They are much lower in price than commercially available radiation-tolerant modules.' This cost saving has been possible only due to the massive use of carefully selected and radiation tested commercial off-the-shelf (COTS) components.

Following on from the design phase, the production phase consists of assembling about 2500 bricks and other components into 300 LV BOXes and performing the final tests. Custom-made testers enable automated checks of the functionality of the bricks and LV BOXes to be done before they are installed in the ATLAS cavern. The very first production LV BOXes have already been used in the Tile Calorimeter cosmic-ray test reported recently in the Bulletin (see Bulletin No. 30-31/2005).

The Tile Calorimeter LVPS system also contains converters generating the input voltage for the bricks in the LV BOXes. These converters were developed in collaboration with the TESLA company from the Czech Republic and the Institute of Physics of Prague. All the components of the system include control units driven by a CAN fieldbus network from the ATLAS counting room.

The design team would like to thank all the people who supported and helped with the project. The team for development consisted of Ivan Hruska, Francisca Calheiros and Bohuslav Palan, The team also benefited from temporary work of two technicians from Prague, Jiri Palacky and Zdenek Kotek, who helped with prototyping and cabling design.

For additional information see http://cern.ch/lv-power-supply