• D. Wang, G. D'Auria, P. Delgiusto, A. Fabris, M.M. Milloch, A. Rohlev, C. Serpico
  ELETTRA, Basovizza

Funding: The work was supported in part by the Italian Ministry of University and Research under grant FIRB-RBAP045JF2

The former linac sections used in the injector system of the Elettra Laboratory storage ring will be upgraded for use on the FERMI@elettra project, a free-electron laser user facility operating down to 3 nm. These seven accelerating sections are 3π/4 mode backward-travelling wave (BTW) constant-impedance structures, powered by 45 MW TH2132A klystrons couple to what was called a PEN – power enhancement network, or more commonly referred to as a SLED system. Due to breakdown problems inside the sections, that was the result of high peak fields generated during conventional SLED operation, the sections experienced difficulties in reaching the design gradients. To lower the peak field and make the compressed pulse “flatter”, phase-modulation of the SLED drive power option is investigated. This paper presents the results of this investigations and includes a detailed mathematically analysis.

• C. Serpico, G. D'Auria, P. Delgiusto
  ELETTRA, Basovizza

Funding: "The work was supported in part by the Italian Ministry of University and Research under grant FIRB-RBAP045JF2 or grant FIRB-RBAP06AWK3 or grants FIRB-RBAP045JF2 and FIRB-RBAP06AWK3"

FERMI@Elettra is a FEL user facility under construction at Sincrotrone Trieste, Italy. It will use the existing normal conducting S-band Linac and seven accelerating sections received from CERN after the LIL decommissioning. Two additional new sections are also foreseen. The Linac repetition rate will be 10 Hz during the initial stage of operation, but it will be ramped up from 10 Hz to 50 Hz. Due to the higher RF power dissipation, the temperature distribution on the copper structure will reach higher values. RF heating will imply a thermal deformation of the accelerating cavities, both in the transversal and in the longitudinal direction. Since FERMI@Elettra has stringent requirements on phase stability, the length of the section must be kept as constant as possible. In this paper the thermo-mechanic behaviour of the accelerating sections is investigated and the results of the simulations are presented. Furthermore an algorithm has been developed to control the longitudinal deformation of the sections.