Dump system concepts for the Future Circular Collider

The Future Circular Collider (FCC-hh) beam dump system must provide a safe and reliable extraction and dilution of the stored beam onto a dump absorber. Energy deposition studies show that damage limits of presently used absorber materials will already be reached for single bunches at 50 TeV. A fast field rise of the extraction kicker is required in order to sufficiently separate swept single bunches on the extraction protection absorbers in case of an asynchronous beam dump. In line with this demand is the proposal of a highly segmented extraction kicker system which allows for accepting a single kicker switch erratic and thus, significantly reduces the probability of an asynchronous beam dump. Superconducting septa are foreseen to limit the overall system length and power consumption. Two extraction system concepts are presented and evaluated regarding overall system length, energy deposition on absorbers, hardware requirements, radiation issues, and layout flexibility.

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Figure 1

Layout of the FCC collider. Courtesy D. Schulte.

Figure 2

Sketch of the dump concept. Arrows are indicating quadrupoles, MKD and MSD denote the extraction kicker and septum magnets, TCDS and TCDQ the protection absorbers for the septum and the quadrupoles, respectively.

Figure 3

Layout and optics of the dump concept. The dipole at the left end of the long central drift is the extraction kicker, followed by the extraction septum.

Figure 4

Maximum energy deposition density (top) and temperature (bottom) versus $\sqrt{{\beta }_x{\beta }_y}$, induced by a single LHC, HL-LHC and FCC proton bunch in a CfC absorber with a density of $1.4\mathrm{g}/{\mathrm{cm}}^3$. The energy densities were obtained with FLUKA simulations, assuming that beams are round (${\beta }_x={\beta }_y$). The physical beam size ($\sigma ={\sigma }_{x,y}$) is displayed next to the data points. The FCC bunch parameters are specified in Table 1. The LHC and HL-LHC beam parameters are detailed in the text.

Figure 5

Energy deposition density maps, calculated with FLUKA, for a 7 TeV bunch (top half) and a 50 TeV bunch (bottom half) in a CfC absorber with a density of $1.4\mathrm{g}/{\mathrm{cm}}^3$. The beam size ($\sigma$) is assumed to be $100\mu \mathrm{m}$ in the upper figure, and $400\mu \mathrm{m}$ in the lower figure. The beam direction is from the left to the right. The $z$-variable indicates the absorber depth and the $r$-variable the radial distance from the beam axis. All maps are expressed as a fraction of the maximum energy deposition density.

Figure 6

Maximum temperature in a CfC absorber ($1.4\mathrm{g}/{\mathrm{cm}}^3$) as a function of the number of FCC bunches swept across the absorber front face. The temperatures were calculated in adiabatic limit, using FLUKA energy deposition results. The transverse bunch size ($\sigma$) was assumed to be $200\mu \mathrm{m}$, which corresponds to $\sqrt{{\beta }_x{\beta }_y}\approx 1\mathrm{km}$. The different curves assume a different transverse bunch separation in the sweep direction.

Figure 7

Layout of the dump concept. Arrows are indicating quadrupoles, MKD and MSD denote the extraction kicker and septum magnets, TCDS and TCDQ the protection absorbers for the septum and the quadrupoles, respectively.

Figure 8

Layout and optics of the alternative dump concept. The dipoles in the middle represent the septa, the elements to the outside of the straight the extraction kickers.

Figure 9

Sketch of a dump tunnel separated from the arc.

Figure 10

Sketch of a dump tunnel downstream the collimation system.