  The g2p/GEp experiments used a solid NH3 polarized target, where the
polarization of the target is sensitive to temperature and radiation. The beam
current was limited to 5-100 nA during the experiment to avoid too much
depolarization of target (The typical Hall A running condition for beam current
is 1 uA to 100 uA). The measured charge was further used to get the accurate
physics cross sections. New BCM (Beam Current Monitor) receivers and a DAQ
system were used to measure the beam current at such a low current range. A
tungsten calorimeter was used to calibrate the BCMs. This technical note
summarizes the calibration procedure and the performance of the BCMs.
