| Summary: | Abstract: Accurate measurements of the cosmic ray electron energy spectrum in the energy region 50 GeV to greater than 1 TeV may reveal structure caused by the annihilation of exotic dark matter parti-cles and/or individual cosmic ray sources. Here we describe a new long duration balloon (LDB) ex-periment, ECAL, optimized to directly measure cosmic ray electrons up to several TeV. ECAL in-cludes a double layer silicon matrix, a scintillating optical fiber track imager, a neutron detector and a fully active calorimeter to identify more than 90 % of the incident electrons with an energy resolution of about 1.7 % while misidentifying only 1 in 200,000 protons and 0.8 % of secondary gamma rays as electrons. Two ECAL flights in Antarctica are planned for a total exposure of 50 days with the first flight anticipated for December 2009. The ECAL Science Objectives Particle acceleration associated with supernova remnant (SNR) shocks appears to be the best (but not the only) explanation for how galactic cosmic rays (GCR) below a few PeV achieve their high energies. Evidence that parti-
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