A compact source for high brightness x-ray generation is disclosed. The higher brightness is achieved through electron beam bombardment of multiple regions aligned with each other to achieve a linear accumulation of x-rays. This may be achieved by aligning discrete x-ray sub-sources, or through the use of x-ray targets that comprise microstructures of x-ray generating materials fabricated in close thermal contact with a substrate with high thermal conductivity. This allows heat to be more efficiently drawn out of the x-ray generating material, and in turn allows bombardment of the x-ray generating material with higher electron density and/or higher energy electrons, leading to greater x-ray brightness.Some embodiments of the invention comprise x-ray optical elements placed between sub-sources of x-rays. These x-ray optical elements may form images of one or more x-ray sub-sources in alignment with other x-ray sub-sources, and may enhance the linear accumulation that can be achieved.