Fluxon-fluxon collision testing by a dissipative spot

Fluxon collisions have recently been successfully imaged by a focused electron beam [A. Laub et al., Phys. Rev. Lett. 75, 1372 (1995)]. This report presents numerical and analytical calculations of the effect of a beam-induced dissipative spot on a fluxon-fluxon collision in a long Josephson junction. In contrast to the fluxon-antifluxon collision, the energy loss for the colliding fluxons of the same polarity is minimal at the collision point. Good accord between analytical and numerical results is found. Presented calculations are relevant for interpretation of the low temperature scanning electron microscopy experiments on fluxon imaging in long Josephson junctions.