Experimental evidence has been found for a filtering effect on the soft electron component in electromagnetic showers when combinations of low-Z and high-Z materials are used as absorbers. The ...filtering effect can be fully exploited to reduce the electromagnetic calorimeter response, making it possible to achieve the compensation condition in a Si/Fe+Pb calorimeter with an effective interaction length almost equal to that of Fe. The action of Fe on Pb, by modifying the critical energy during the electromagnetic shower development, leads to a yield of soft electrons (and very few photons) that are stopped in subsequent absorber layers and/or absorbed by the G10 plates. Recent measurements performed with an enlarged Si/Fe+Pb calorimeter support the idea; the authors have shown that an electromagnetic energy smaller than the hadronic energy is possible once particular FePb configurations are used.< >
The first prototype of a Si/U hadronic calorimeter was designed and developed. It consists of silicon mosaics, located next to uranium plates 10-mm thick and 50*50 cm/sup 2/ in area. The total ...calorimeter depth is six interaction lengths. Measurements performed with the Si/U calorimeter at the CERN PS (at 2, 4 and 6 GeV) support the view that the signal equalization, which provides the condition e/h=1, can be obtained with a silicon readout by tuning the calorimeter response to the electromagnetic component of the hadronic shower. This can be achieved by inserting, in front and/or back of the silicon detector, low-Z absorber (G10 plates). The fiberglass absorbs soft electrons, thus reducing the total energy sensed. The low-Z absorber is used to reduce the response of the electromagnetic component in a hadronic shower, while the pure hadronic component is expected to be only slightly affected.< >
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