Femtosecond electron bunch lengths in the SLAC FFTB beamline

We describe a new proposal to generate bunches as short as 35 fsec rms with the existing SLAC linac and damping ring. The bunch is compressed in three stages, starting with the existing ring-to-linac compressor. A second stage of compression is added in the form of a simple magnetic chicane installed at the 9-GeV location in the linac. The short bunch after the chicane generates a strong wakefield in the linac which provides a large correlated energy spread allowing a third compression stage in the existing Final Focus Test Beam (FFTB) beamline. Peak currents as high as 30 kA are possible and when passed through a new undulator in the FFTB, can generate hard x-rays of very high peak brightness and pulse duration of 80 fsec FWHM. The short bunch is ideal for plasma and wakefield studies as well as providing abundant R&D for verifying micro-bunch behavior in the future Linac Coherent Light Source (LCLS).