Sub-surface nuclear tests monitoring through the CTBT xenon network

We present the first evaluation of the atmospheric xenon network to be inst alled as part of the International Monitoring System (IMS) in the frame of the Comprehensive Test Ban Treaty (CTBT). We show that this network should, by itself, provide a significant contribution to the total efficiency of t he IMS. For this evaluation, we introduce an inverse approach based upon th e time symmetry of the atmospheric transport of trace species. This approac h may find applications in a variety of environmental problems.