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PS2 parameters used for the e-cloud simulations (M. Benedikt, Y. Papaphilippou)

PS2 parameters used for the e-cloud simulations (M. Benedikt, Y. Papaphilippou). Sample results of electron cloud build-up close to the build up threshold for LHC25, LHC50 and Fixed Target beams at injection and before extraction.

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PS2 parameters used for the e-cloud simulations (M. Benedikt, Y. Papaphilippou)

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  1. PS2 parameters used for the e-cloud simulations (M. Benedikt, Y. Papaphilippou)

  2. Sample results of electron cloud build-up close to the build up threshold for LHC25, LHC50 and Fixed Target beams at injection and before extraction The electron cloud build up has been calculated over two turns of the beam inside the PS2. For comparison of the different cases we will refer to the values reached by the electron cloud when the build up process reaches saturation.

  3. Results of electron cloud build-up as a function of the maximum SEY for LHC25, LHC50 and Fixed Target beams at injection and before extraction What is plotted here are the average values of the electron cloud line density at saturation for different values of maximum SEY input in the simulation

  4. The build up threshold is maximum SEY=1.2 for almost all beams, except • LHC50@injection (and to some extent FT@injection, but takes longer to saturate) have a significant e-cloud with 1.2 (their threshold is 1.1) • LHC50@extraction has a threshold of 1.5 and produces in general a lower density electron cloud. • The saturation values of the electron cloud (in the range of 1-10 x 109 e-/m for the different types of beams) correspond to densities of 1.5-15 x 1011 e-/m3,which could be detrimental for the beam stability (from experience in other machines, we could expect the threshold to lie in this range). This can be checked with HEADTAIL simulations. • Maximum SEYs below 1.2 and even below 1.1 can be achieved with the C coating currently being investigated by the SPSU Working Team. Measurements inside the SPS with LHC25 beams have shown that the SEY of this coating is below that of activated NEG (supposedly 1.1) and it does not exhibit signs of deterioration with time under vacuum. Lab measurements had predicted the SEY value, and also showed that the degradation due to air venting during several weeks/months is very limited.

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