The Linac Coherent Light Source Photo-Injector Overview and Some Design Details

The Linac Coherent Light Source (LCLS) is a SASE free electron laser using the last 1/3 of the SLAC two mile linac to produce 1.5 to 15 angstrom x-rays in a 100 meter long undulator for use in a variety of x-ray science experiments. In order to satisfy the demanding electron beam requirements, a new 135 MeV photo-injector will be built in an existing, off-axis vault at the 2/3 point of the main linac. The injector accelerator consists of a BNL/SLAC/UCLA 1.6 cell S-band gun followed by two 3meter long SLAC accelerator sections. The 6MeV beam from the gun is matched into the first accelerator section and accelerated to 135 MeV before injection onto the main linac axis with a 35 degree bend. Several modifications to the rf gun, linac and beamline as well as the inclusion of several diagnostics have been incorporated into the injector design to achieve the required 1.2 micron projected emittance at a charge of 1 nC. In addition, an inverse free electron laser, the laser heater, will be used to increase the uncorrelated energy spread to suppress coherent synchrotron radiation and longitudinal space charge instabilities in the main accelerator and bunch compressors. The configuration and function of the major injector components will be described. Contributed to the 9th European Particle Accelerator Conference, Lucerne, Switzerland, 7/5/2004—7/9/2004 * Work supported by Department of Energy contract DE–AC02–76SF00515. THE LINAC COHERENT LIGHT SOURCE PHOTO-INJECTOR OVERVIEW AND SOME DESIGN DETAILS* D.H. Dowell, R. Akre, L. Bentson, P. Bolton, R. Boyce, R. Carr, J.E. Clendenin, S.M. Gierman, S. Gilevich, D. Kotturi, W. Linebarger, Z. Li, C.G. Limborg-Deprey, M. Ortega, J.F. Schmerge, P. Smith, and L. Xiao Stanford Linear Accelerator Center, Menlo Park, CA USA Abstract The Linac Coherent Light Source (LCLS)[1] is a SASE free electron laser using the last 1/3 of the SLAC two mile linac to produce 1.5 to 15 angstrom x-rays in a 100 meterThe Linac Coherent Light Source (LCLS)[1] is a SASE free electron laser using the last 1/3 of the SLAC two mile linac to produce 1.5 to 15 angstrom x-rays in a 100 meter long undulator for use in a variety of x-ray science experiments. In order to satisfy the demanding electron beam requirements, a new 135 MeV photo-injector will be built in an existing, off-axis vault at the 2/3 point of the main linac. The injector accelerator consists of a BNL/SLAC/UCLA 1.6 cell S-band gun followed by two 3-meter long SLAC accelerator sections. The 6MeV beam from the gun is matched into the first accelerator section and accelerated to 135 MeV before injection onto the main linac axis with a 35 degree bend [2]. Several modifications to the rf gun, linac and beamline as well as the inclusion of several diagnostics have been incorporated into the injector design to achieve the required 1.2 micron projected emittance at a charge of 1 nC. In addition, an inverse free electron laser, the laser heater [3], will be used to increase the uncorrelated energy spread to suppress coherent synchrotron radiation and longitudinal space charge instabilities in the main accelerator and bunch compressors [4]. The configuration and function of the major injector components will be described. . INJECTOR REQUIREMENTS Lasing at x-ray wavelengths, the LCLS will require an injector capable of producing the excellent beam quality given in Table I. Simultaneously achieving the combination of the 1 nC charge, 1.2 micron rms emittance and 100 amperes peak current will be difficult, although it has be demonstrated in one experiment.[5] Another experiment has achieved 1.1 micron emittance at 1 nC, but at a much lower peak current.[6] Table I Injector Parameters