CMS electromagnetic calorimeter low voltage system for the front end electronics

The CMS electromagnetic calorimeter front-end electronics requires about 50000 amps of current. The custom designed chips with 0.25-micron technology run at 2.5 V. The delivery of this current / power to the front-end cards by copper buses creates a situation where we have ground potential differences along the distribution buses. This may affect the noise performance of the scintillation light detection by APDs. Substantial power is wasted in the delivery system then consumed by front-end electronics boards. The electronics works in high radiation environment and in 4T magnetic field.