A primary collimator for a multiple inverse fan beam x-ray diffraction imaging (MIFB XDI) system. The MIFB XDI system includes a multi-focus x-ray source (MFXS) defining a plurality of focus points arranged along a length of the MFXS. Each focus point is sequentially activated to emit an x-ray fan beam including a plurality of primary beams each directed to a corresponding convergence point. The primary collimator includes a first diaphragm configured to be positioned with respect to the MFXS. The first diaphragm defines a plurality of first channels through a thickness of the first diaphragm. Each first channel is aligned with a corresponding focus point and configured to transmit the x-ray fan beam. A second diaphragm is positioned with respect to the first diaphragm and defines a plurality of second channels through a thickness of the second diaphragm. Each second channel is axially aligned with a corresponding first channel.