PEBS-1 permanent magnet spectrometer
Mechanical drawing of the PEBS-1 detector.
PEBS-1 consists of a permanent magnet, a scintillating fiber tracker, a transition radiation detector (TRD) and an electromagnetic calorimeter (ECAL). Scintillator panels above and below the tracker act as a time-of-flight system (TOF) and are used for triggering purposes. The magnetic spectrometer has a geometrical acceptance of 1000 cm2sr, while the lower detector combination of TRD and ECAL which is used for the high energy combined electron positron spectrum measurement has an acceptance of 7500 cm2sr which is seven times larger than the ATIC-2 acceptance. The geometric acceptance of the detector is limited by the weight and power constraints imposed by the balloon. The most important contributions to the overall weight are the magnet weight and the weight of the calorimeter with 250 kg and 650 kg respectively. The power consumption is dominated by the 80 W needed for the tracker which has roughly 19,000 individual readout channels.