The "What's After Fermi" workshop at GSFC, June 2014.
As of August 2014 a number of us at SLAC have started to discuss the Next Gamma Telescope concepts (Elliott Bloom, Andrea Caliandro, Rob Cameron, Eric Charles). The discussions have been based on the LArGO concept that was presented at the "Whats After Fermi" workshop at GSFC (see above link). Andrea has made two documents available to us: Goddard presentation, Proposal to the ERC. These documents outline ideas for a gamma ray telescope based on Lq Argon.