• J. Wu, R. Akre, A. Brachmann, P. Chu, F.-J. Decker, Y.T. Ding, D. Dowell, S.A. Edstrom, P. Emma, D. Fairley, J.C. Frisch, A. Gilevich, G.R. Hays, P. Hering, Z. Huang, R.H. Iverson, H. Loos, A. Miahnahri, H.-D. Nuhn, D.F. Ratner, J.L. Turner, J.J. Welch, W.E. White, D. Xiang
  SLAC, Menlo Park, California
• E. Meier
  ASCo, Clayton, Victoria

Funding: Work supported by Department of Energy contract DE-AC02-76SF00515. This work was performed in support of the LCLS project at SLAC

The Linac Coherent Light Source is an x-ray Free-Electron Laser (FEL) project being commissioned at SLAC. The very bright electron beam required for the FEL is subjected to various sources of jitter along the accelerator. The peak current, centroid energy, and trajectory of the electron bunch are controlled precisely at the highest repetition rate possible with feedback systems. We report commissioning experience for these systems. In particular, there is high frequency content in the electron bunch current spectrum, and we report its impact on the systems. Due to the coupling of the betatron motion and the dispersion component of the electron trajectory, a fast in-line model* is incorporated. For the longitudinal feedback, we report the performance of two different configurations: one with RF system as direct actuators, which are nonlinear, and the other with artificially formed linear energy and energy-chirp actuators. Since the electron bunch is compressed to a final peak current of 2 to 3 kA, coherent synchrotron radiation and other wakefields are included for precise control of the electron bunch parameters. Machine performance is compared to start-to-end simulations.

*P. Chu et al., these PAC09 proceedings

• P. Chu, R.H. Iverson, P. Krejcik, G.R. White, M. Woodley, J. Wu
  SLAC, Menlo Park, California
• Q. Gan
  IHEP Beijing, Beijing

Funding: Work supported in part by the DOE Contract DE-AC02-76SF00515. This work was performed in support of the LCLS project at SLAC.

XAL, a high-level application framework originally developed by Spallation Neutron Source (SNS), has been adapted by the Linac Coherent Light Source (LCLS) project. The work includes proper relational database schema modification to better suit XAL configuration data requirement, addition of new device types for LCLS online modeling purpose, longitudinal coordinate system change to better represent the LCLS electron beam rather than proton or ion beam in the original SNS XAL design, intensively benchmark with MAD and present SLC modeling system for the online model, and various new features to the XAL framework. Storing online model data in a relational database and providing universal access methods for other applications is also described here.

• G.R. White, A. Chan, P. Chu, E. Grunhaus, P. Krejcik, K. Luchini, M. Woodley
  SLAC, Menlo Park, California

Funding: Department of Energy contract DE-ACO3-76SF00515

We describe an integrated relational database for beamline element configuration and online accelerator modelling for LCLS. It is hosted in Oracle, from which online controls software, optimization applications and feedback, use a programming interface to acquire the element data and model. Database population is by an automated process starting with a MAD deck, which is processed in Matlab to derive text files that describe the beamline elements whose data are uploaded using Oracle Loader, and the resulting Oracle APEX applications and reports are used for survey, cabling, metrology and other facilities. An automated facility for online model generation creates an XAL online model beamline description file using a database query; the resulting model is then tracked, and results can be loaded back into the database. As such, both the design or extant machine model, of the present and all previous model runs are available, and linked to the relevant element configuration. We present the process flow from the MAD design to the database, the database schema, the database applications, the process of generating a machine model, and some scientific software which uses the database.