Author: Sauerland, D.
Paper Title Page
WEPFI007 Amplitude, Phase and Temperature Stabilization of the ELSA RF System 2717
 
  • D. Sauerland, W. Hillert, A. Roth, M. Schedler
    ELSA, Bonn, Germany
  • D. Teytelman
    Dimtel, San Jose, USA
  
  In the stretcher ring of the ac­cel­er­a­tor fa­cil­ity ELSA elec­trons are ac­cel­er­ated to a max­i­mum en­ergy of 3.2 GeV ap­ply­ing a fast en­ergy ramp of up to 6 GeV/s. In order to be able to offer higher ex­ter­nal beam cur­rents one has to in­crease the cur­rent of the in­ter­nal beam in ELSA ac­cord­ingly. The beam cur­rent is lim­ited due to ex­ci­ta­tion of multi bunch in­sta­bil­i­ties which are mainly caused by higher order modes of the two PETRA cav­i­ties used for par­ti­cle ac­cel­er­a­tion in the stretcher ring. To con­trol the res­o­nance fre­quency of these modes, a vari­able by­pass of the cav­i­ties' cool­ing sys­tem has been in­stalled which al­lows a sta­bi­liza­tion of their tem­per­a­ture. With this mod­i­fi­ca­tion, it is pos­si­ble to vary the tem­per­a­ture of the cav­i­ties be­tween 26 °C and 65 °C and thus to shift the higher order modes by hun­dreds of kHz in fre­quency. Ad­di­tion­ally, first op­er­a­tional stud­ies with a pro­to­type of a FPGA based LLRF sys­tem (Dim­tel) have been per­formed which in fu­ture will be used to sta­bi­lize the am­pli­tude and phase of the ac­cel­er­at­ing RF fields of the cav­i­ties.