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Introduction

The barrel calorimeter (BCAL) is a crucial Hall D detector subsystem. This device will be responsible for the detection, identification and total energy measurement of all neutral (photons, neutrons) and charged (protons, pions) particles within its volume. These demands place stringent constraints on its performance characteristics.

Specifically, the BCAL must provide the best possible energy and timing resolutions, low threshold of detection, and the ability to completely contain the electromagnetic showers, resulting from the conversion of photons into electrons and positrons. The dynamic energy range for photons over the complete list of induced reactions in the liquid hydrogen target spreads from as low as 20 MeV to as high as 1 GeV, as a result photons tend to emerge at much larger angles than heavier particles. Since the total energy of all the final state particles must be determined, sufficient energy from electromagnetic showers produced must be contained within the barrel calorimeter to allow the correct reconstruction of the photon's energy. To achieve this, the barrel calorimeter must be designed in such a way so that it covers its entire allocated solid angle confined by $14^o \le \theta
\le 138^o$ and $0^o \le \phi \le 360^o$. As well, a high Z material (e.g., lead sheets) and sufficient thickness in radiation length ($\ge
15X_o$) are demanded so as to provide the means for containing the electromagnetic showers from escaping from the rear of the BCAL. These requirements are coupled to the minimum inner radius of the BCAL, which will allow for the placement of the interior subsystems (chambers, start/vertex counter and target), in setting the radial dimensions of the BCAL (0.65 m - 0.90 m). It's longitudinal dimension is largely dictated by the length of the solenoid magnet, resulting in a length of 4.5 m.

The basic design of the calorimeter follows closely that of the KLOE calorimeter [4]. The design envisions a matrix consisting of lead sheets of 0.2 to 0.5 mm thick and 1 mm diameter scintillating fibers. The lead sheets will be ``grooved'' and the fibers will be glued in these grooves, parallel to the central axis of the Hall D detector. The scintillation photons will travel down the scintilating fiber, to Winston-cone light guides and eventually to photomultiplier tubes attached at the ends of them, thus producing an electrical signal. Consequently the inherent properties of scintillating fibers play a crucial role. The criteria which must be evaluated include:

To this end, fibers from two different manufacturers and of two different types were procured by the SPARRO Group at the University of Regina, to be tested in connection to their light attenuation and timing resolution. Specifically, the tested fibers were Kuraray SCSF-81 single-clad [5], Pol.Hi.Tech.0046 single- and multi-clad [6]. All fibers were 1 mm in diameter and were procured in the summer of 2000. In addition, in the summer of 2001, a second bundle of single-clad Kuraray fibers was procured.


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Next: Notes on Timing Resolution Up: Overall Previous: Abstract
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2001-10-29