Ultra Fast Self-Compton Cooling

We investigate the synchrotron self-Compton process in a planar shell taking the shock structure into account. We find that the energy density of the seed photons could deviate from the one-zone estimate by order of unity depending on the shock velocity and the electron cooling time. We also find that as the electron cooling becomes faster, the seed photons are increased more, so that the inverse Compton cooling becomes more efficient. This ``ultra'' fast cooling may work in such as gamma-ray bursts, blazars and microquasars.