A method of obtaining PINEM images includes providing femtosecond optical pulse, generating electron pulses, and directing the electron pulses towards a sample. A core well and an IO well are created in a semiconductor substrate and separated by an isolation structure. Strands adjacent to the thick strands are thin strands, and space allows flow of active material to sides of the thick strands. The gamma sectors are provided with a third frequency assignment that includes the first frequency band and a fourth frequency band. The first rib is positioned inside the outer perimeter edge.