The calorimeter for experiments at the future ILC must be realized as a dense and hermetic sampling calorimeter with very high granularity to allow the separation of the various particles in a jet and to use the best suited detector component to measure their four-momentum. The goal is to reach a jet energy resolution of 30%/sqrt(E). The success of this approach will originate more from the higher segmentation (both lateral and longitudinal) than from the stochastic and constant term in the energy resolution.

Over the past years, the CALICE collaboration has developed, built and tested prototype detectors for all main calorimetric systems forseen at the ILC. In summer 2006, a full chain of subdetectors has been successfully assembled and operated at the CERN hadron test beam area consisting of a Si-W electromagnetic calorimeter (Ecal), a scintilator-steel hadron calorimeter with analog SiPM readout (AHcal) and a tailcatcher/muon tracker based on the same technology (TCMT). The Ecal is instrumented with 30 layers of 1cm x 1cm cells, the AHcal with 23 layers of 3cm x 3cm scintillator tiles in the core, and the TCMT with 16 layers of 5cm x 100cm scintillator strips. All three detectors with almost 12,000 channels are read out by the same data acquisition.

This test beam effort has two main purposes: the establishment of the detector technologies in a large scale application and the collection of hadronic shower data with unprecedented granularity. The results of these measurements will have impact on the validation of hadronic shower simulation as well as the development of clustering and particle flow algorithms. They can be a first experimental proof-of-principle for the particle flow approach and serve as guidance for the final design of the calorimetric system of an ILC detector.