Abstract

Modern high luminosity e^+e^− factories, like Belle II at SuperKEKB or planned Super Charm-Tau factory require fast calorimeters to cope with severe background conditions. The prototype of the fast electromagnetic calorimeter based on pure CsI scintillation crystals, wavelength shifters with the novel nanostructured organosilicon luminophores, and avalanche photodiodes Hamamatsu S8664-55 is discussed. The results of the tests of the basic element of the calorimeter are reported.

Highlights

  • The ultrahigh luminosity e+ e− factories, like Belle II at SuperKEKB [1, 2], which already started its operation, and planned Super Charm-Tau factory [3] suffer from severe beam background

  • To measure the APD excess noise factor F(λ) the equivalent noise charge (ENC) in the electronic readout chain was studied for the APD with and without light-emitting diodes (LED) illumination, see Fig. 1

  • (we evaluate ENC in the units of electron charge |e|)

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Summary

Introduction

The ultrahigh luminosity e+ e− factories, like Belle II at SuperKEKB [1, 2], which already started its operation, and planned Super Charm-Tau factory [3] suffer from severe beam background. The counter based on the pure CsI (CsI(pure)) crystal (of 6×6×30 cm[3] size), wavelength shifting (WLS) PMMA plate with the nanostructured organosilicon luminophores (NOL-9) [8, 9], four avalanche photodiodes Hamamatsu APD S8664-55 coupled to the edge sides of the WLS plate, and four-channel charge sensitive preamplifier CAEN A1422B045F3 was studied and the acceptable performance of the counter was demonstrated [5–7]. The specific light output (sLO) of the counter was evaluated to be sLO = (100 ± 10) photoelectrons/MeV, and the equivalent noise energy (ENE). The step towards the construction of the calorimeter prototype was to develop the standard counter: optimize the size and shape of the WLS plate, choose the scheme to couple 4 APDs to the WLS plate, develop four-channel custom-made charge sensitive preamplifier, optimize mechanics of the shielding box. In this paper we discuss several issues on the construction of the standard counter

Spectral variation of the APD gain and excess noise factor
GW Instek
2Iphoto τ
Optimization of the WLS plate
Construction of the first counter
Conclusion
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