Measurements of compression and emittance growth after the first LCLS bunch compressor chicane

The Linac Coherent Light Source (LCLS) is a SASE X-ray free-electron laser project presently under construction at SLAC [1]. The injector section from RF photocathode gun through first bunch compressor chicane was installed during the fall of 2006. The first bunch compressor is located at 250 MeV and nominally compresses a 1-nC electron bunch from an rms length of about 1 mm to 0.2 mm. Transverse phase space and bunch length diagnostics are located immediately after the chicane. We present preliminary measurements and simulations of the longitudinal and transverse phase space after the chicane in various beam conditions, including extreme compression with micron-scale current spikes.