Nahee Park
University of Chicago
TeV electron measurements with the CREST experiment
High energy cosmic rays have long been thought to be produced by shock acceleration in supernova remnants. Indirect evidence of this for regarding the electron component of cosmic rays has come via measurements of non-thermal x-ray and TeV gamma-ray emission in supernova remnants. Direct measurements of high energy electrons at Earth require large detection areas and efficient background discrimination because the flux spectrum of electrons is steeper than that of heavier components such as protons. This is caused by radiative energy losses during propagation in the Galaxy. Additionally, because of these energy loss processes, the TeV electron flux is expected to reflect the distribution and abundance of nearby (vs remote) accelerating sources.
The Cosmic Ray Electron Synchrotron Telescope (CREST) is a balloon-borne experiment designed to measure the spectrum of multi-TeV electrons by the detection of the x-ray synchrotron photons generated as the electrons traverse the magnetic field of the Earth. The instrument is composed of 1024 BaF2 crystals array viewed by PMTs and scintillating veto counters surrounding the crystal array. Since the instrument needs to intersect only a portion of the kilometers-long trail of photons generated by the high energy electron, the method yields a larger effective area than the physical size of the detector. The propagation of electrons in the atmosphere and the detector response have been studied with the simulation models to estimate the effective geometry factor and the efficiency of the instrument. CREST had a successful engineering flight in Fort Sumner in 2009. The experiment is aiming for a flight in Antarctica as a long duration balloon payload during the 2010-11 season. An overview of the detector design, simulation study and fabrication status will be presented.