Efficient twin aperture magnets for the future circular $e^{+}/e^{\_}$ collider

We report preliminary designs for the arc dipoles and quadrupoles of the FCC-ee double-ring collider. After recalling cross sections and parameters of warm magnets used in previous large accelerators, we focus on twin aperture layouts, with a magnetic coupling between the gaps, which minimizes construction cost and reduces the electrical power required for operation. We also indicate how the designs presented may be further optimized so as to optimally address any further constraints related to beam physics, vacuum system, and electric power consumption.

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Figure 1

Cross section and 3D sketch of the LEP dipoles.

Figure 2

Cross section of the HERA electron ring dipoles.

Figure 3

Cross section of the SLC arc combined function dipoles.

Figure 4

Cross section of the MQW quadrupoles in the LHC.

Figure 5

Schematic layouts of twin dipoles arrangements: (a) two separate C magnets with independent powering circuits; (b) two C yokes, with a single shared excitation turn; (c) a single wide C dipole; (d) a wide O (or H, if needed) dipole; (e) an I layout. For (a) and (b), the separate magnets or yokes are not constrained to be side by side, and they can be mounted on a shared support structure.

Figure 6

First cross section of FCC-ee bending magnets with an I layout (field levels for 175 GeV).

Figure 7

First cross section of FCC-ee twin quadrupoles; the geometry is to scale with the twin dipole of Fig. 6 (field levels for 175 GeV).

Figure 8

Example of pole profile ($1/4$ of cross section shown) for a combined function magnet; in this case, the central slope is 4 deg, yielding a gradient of $86\mathrm{mT}/\mathrm{m}$ for a field of 60 mT. The colorbar follows the same scale of Fig. 6.