We present an Inverse Free Electron Laser accelerator proposed for construction at the UCLA Neptune Laboratory. This experiment will use a 1 TW CO2 laser to accelerate through two strongly tapered undulators an electron beam from 16 MeV up to 5 MeV. The scheme proposed is the diffraction dominated IFEL interaction. The Raleigh range of the laser beam is about 2 cm, much shorter than the interaction length (the undulator length is 50 cm). In this regime adiabatic capture is possible in the first part of the undulator. In the focus region, we propose a solution to the problem of the dephasing between electrons and photons due to the 386 10th Advanced Accelerator Concepts Workshop /home/httpd/docserver/releases/20080613005430/public/paper/file/229/musumeci_2002_0506.pdf musumeci_2002_0506.pdf 3 229 3 2002 AIP Conference Proceedings, no. 647 506 2007-07-27T23:53:38-07:00 278-285 2002