CALICE Si/W electromagnetic calorimeter prototype, first testbeam results

A highly granular electromagnetic calorimeter prototype based on tungsten absorber and sampling units equipped with silicon pads as sensitive devices for signal collection is under construction. The full prototype will have in total 30 layers and be read out by about 10000 Si cells of 1 cm^2. A first module consisting of 14 layers and depth of 7.2 radiation lengths at normal incidence, having in total 3024 channels of 1 cm^2, was tested recently with electron beam. We describe the prototype and discuss some preliminary testbeam results.