Sketch of a symmetrical magnetic loop. The limits of the looptop sources are the cross sections of the loop with area A_LT shown in gray. The length L_LT and width W_LT of the looptop X-ray source are used to determine the size of the looptop source, which is approximated to a cylinder of diameter W_LT. Blue arrows represent the electron rate for electrons leaving the looptop source of cross-section A_LT.