The LLRF System for the S-Band RF Plants of the FERMI Linac

• Published in: IEEE transactions on nuclear science Vol. 63; no. 2; pp. 861 - 868
• Main Authors: Fabris, A., Byrd, J., D'Auria, G., Doolittle, L., Gelmetti, F., Huang, G., Jones, J., Milloch, M., Predonzani, M., Ratti, A., Rohlev, T., Salom, A., Serrano, C., Stettler, M.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.04.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acceleration; Closed loop systems; feedback; field-programmable gate arrays (FPGAs); Linear particle accelerator; Mixers; Nonlinear distortion; Phase distortion; Radio frequency; radio frequency (RF)
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2015.2501649

Specifications on electron beam quality for the operation of a linac-based free-electron laser (FEL), as FERMI in Trieste (Italy), impose stringent requirements on the stability of the electromagnetic fields of the accelerating sections. These specifications can be met only with state-of-the-art low-level RF (LLRF) systems based on advanced digital technologies. Design considerations, construction, and performance results of the FERMI digital LLRF are presented in this paper. The stability requirements derived by simulations are better than 0.1% in amplitude and 0.1 ° S-band in phase. The system installed in the FERMI Linac S-band RF plants has met these specifications and is in operation on a 24-h basis as a user facility. Capabilities of the system allow planning for new developments that are also described here.