Study of the Damage Potential of the FCC-ee Beams

The beam characteristics of the Future Circular Collider electron-positron (FCC-ee) beam differ vastly from those of the Large Hadron Collider (LHC) beam and the High Luminosity LHC (HL-LHC) beam, presenting new challenges for assessing beam impact and damage potential. The FCC-ee consist of electrons with significantly lower energies than the protons in the LHC and HL-LHC beams. In the Z~mode, the total stored beam energy will be 17.5 MJ, while the same values for the LHC and HL-LHC beams are 362 MJ and 681 MJ, respectively. The FCC-ee beams will also operate with a highly asymmetric emittance ($\epsilon_x > \epsilon_y$), while the LHC and HL-LHC beams can be approximated as round. This report presents the stored beam energy and analytical estimations for the energy density of the FCC-ee beams, considering a range of beam sizes, and compares them with the LHC and HL-LHC beams. Then, energy deposition of the generic scenario of a direct beam impact on a graphite target with nominal material density is simulated using FLUKA. Results show that the peak energy depositions for the FCC-ee beams with Z~mode parameters are comparable to those of the LHC and HL-LHC beams. However, the shape of the energy deposition shower is more peaked and localized close to the beam impact point. In the last step, the hydrodynamic response of the material due to the impact of a round beam with a corresponding peak energy deposition is analyzed. After the impact of five bunches, it is observed a maximum energy deposition and temperature rise comparable to those due to the impact of the HL-LHC beam with a beam size of $\sigma$ = 0.5 mm. However, the local target density depletes more rapidly.