Overall design

HERD is composed of five scientific instruments. The primary instrument in the innermost is a deep 3-D imaging calorimeter (CALO) with an innovative design that insures better e/p separation for particles and one order of magnitude larger geometrical factor by accepting particles impinging on its top face but also on the four lateral faces. Each sensitive face of CALO is instrumented from inside out with a FIber Tracker (FIT), a Plastic Scintillation Detector (PSD) and a Silicon Charge Detector (SCD) to precisely identify charges of cosmic rays. A Transition Radiation Detector (TRD) is located on one lateral side for the energy calibration of TeV neuclei. The total mass of HERD payload is about 4 tons.