S. Pensotti

Evidence for the compensation condition in Si/U hadronic calorimetry by the local hardening effect

Abstract In a hadronic calorimeter with silicon readout, a combination of thin plates oflow- Z andhigh- Z materials used as absorbers enables the reduction of the calorimeter response to the electromagnetic component of the incoming hadronic showers (the “local hardening effect”). As a result, a ratio varying from e/π> 1 toe/π>is obtained as a function of thelow- Z material thickness, demonstrating the possibility of achieving the compensation condition(e/π= 1)by exploiting the local hardening effect.

Study of current-voltage characteristics of irradiated silicon detectors

Abstract Current-voltage (I-V) characteristics of non-irradiated and irradiated p+-n-n+ detectors, with neutron fluences (φ) up to 1014 n/cm2 were measured and the obtained data were analyzed. The If-Vf characteristics confirmed the existence of a critic fluence boundary (φb > 5 × 1011 n/cm2), similar to those found by other types of measurement (DLTS, C-V). We found that at φb the rectification ratio is reduced drastically, but a large reverse voltage can, nevertheless, be applied. The series resistivity (ϱ) calculated from the If-Vf characteristics, for both non-irradiated (NI) and irradiated detectors, shows that for NI detectors the resistivity is of the order of that of the silicon bulk (1200 Ωcm). The resistivity (ϱ) for irradiated devices increases (with increasing values of φ, of up to 1014 n/cm2), up to ∼4 × 10 3 Ω cm . As a result of the increase of ϱ with φ, the p+-n-n+ becomes a p+-v-n+ device. This study explains the rather good charge collection efficiency in spite of str affected physical properties.

Systematic investigation of the electromagnetic filtering effect as a tool for achieving the compensation condition in silicon hadron calorimetry

Abstract In a calorimeter with silicon readout, the use of a combination of low- Z (Fe) and high- Z (Pb) materials as absorbers allows the transformation of the electron energy distribution of the incident showers in two media with different critical energies via the filtering effect. As a result, the visible electromagnetic energy and consequently the value of the e/mip ratio can be substantially reduced as a function of the thickness of the high- Z (Pb) material present in the absorber. Measurements of this effect for a set of Si/Fe+Pb calorimeter configurations are presented and discussed. The filtering effect makes possible the achievement of the compensation condition.

Compensating silicon calorimetry for the next generation of hadronic colliders

Abstract The compensation condition (e/ π = 1) is discussed. It mainly determines the performances of the silicon calorimeters to be used at the next generation of hadronic colliders (LHC, UNK, SSC).

Systematic investigation of the local hardening effect and lateral electromagnetic shower development

Abstract In silicon sampling calorimeters, a local hardening effect occurs when inserting a small thickness of low-Z material next to the thin active layer. This effects, which modifies appreciably the electromagnetic response, allows the control of the relative responses to hadronic and electromagnetic showers. A thorough study of lateral shower profiles has been undertaken to improve the precision of the measurement of the absolute electromagnetic response. The main features of the local hardening effect as a function of the thickness of low-Z material are explained by a 1/E distribution of ionizing particles inside the shower, while those of the lateral profile are explained by an exponential radial distribution.

Investigation of the local hardening effect produced by various low-Z materials in a Si/(Fe, Pb) electromagnetic calorimeter

The condition for obtaining a calorimetric response linear with energy for hadronic showers and an energy resolution that improves as the incident energy increases is the equalization of the electromagnetic (e) and the hadronic (π) signal responses. This equalization is obtained by exploiting a local hardening effect realized through the insertion of low-Z thin plates between the low-Z absorbers and the active material in a hadronic calorimeter with silicon readout. This effect, which allows the reduction of the calorimeter response to the electromagnetic component of the incoming hadronic showers, has been investigated for different low-Z materials. The relevance of some aspects of this study to the radiation hardness of the calorimeters is also addressed.

Test system for an optical readout chain of a silicon microstrip detector

Abstract A test system, for an optical readout chain of a double-sided silicon microstrip detector, is presented. The system can be used for a quick but complete test of the working performance of the optical readout chain, and for finding exactly the faulty part of the readout chain, in case that an error is detected. It was designed, developed, and built for a silicon microvertex detector used at the LEP collider. A description, of both the hardwave and software of the system, is given. Finally, experimental results, of laboratory tests, are shown.

The study of compensation in silicon hadron calorimetry

In a hadron sampling calorimeter with silicon readout, a combination of plates of low-Z and high-Z materials used as absorbers enables the reduction of the calorimeter response to the electromagnetic component of the incoming hadronic showers. This reduction can be produced independently by two effects: a local hardening effect realized by inserting low-Z absorbers (G10 plates) next to the silicon readout detectors, and a filtering effect obtained by using a combination of low-Z (Fe) and high-Z (Pb) material as absorbers. As a result, in both cases, a ratio varying from e/π > 1 to e/π < 1 is obtained as a function of the low-Z material thickness, demonstrating the possibility of achieving the compensation condition (e/π = 1).

Electromagnetic filtering effect in silicon calorimetry

Abstract In a calorimeter with silicon readout, the use of a combination of low-Z (Fe) and high-Z (Pb) materials as absorbers enables the transformation of the electron energy distribution of the incident showers in two media with different critical energies via the filtering effect. As a result, the electromagnetic energy value can be substantially reduced as a function of the thickness of high-Z (Pb) material present in the absorber. Measurements of this effect for a set of Si/{Fe + Pb} calorimeter configurations are presented and discussed. A direct consequence of the filtering effect is to enable the achievement of the compensation condition.

Evidence for compensation in a Si hadron calorimeter

The authors present results of measurements performed at the CERN Proton Synchrotron with a hadron Si/(Fe,Pb) calorimeter. In the hadron sampling calorimeter with silicon readout, a combination of plates of low-Z (Fe) and high-Z (Pb) materials used as absorbers enables the reduction of the calorimeter response to the electromagnetic component of the incoming hadronic showers. As a result, a ratio, varying from e/ pi >1 to e/ pi >