Machine detector interface studies: Layout and synchrotron radiation estimate in the future circular collider interaction region

The interaction region layout for the $e^{+}{e}^{-}$ future circular collider FCC-ee is presented together with a preliminary estimate of synchrotron radiation that affects this region. We describe in this paper the main guidelines of this design and the estimate of synchrotron radiation coming from the last bending magnets and from the final focus quadrupoles, with the software tools developed for this purpose. The design follows the asymmetric optics layout as far as incoming bend radiation is concerned with the maximum foreseen beam energy of 175 GeV and we present a feasible initial layout with an indication of tolerable synchrotron radiation.

This article appears in the following collection:

Figure 1

View of the FCC-ee IR layout $\pm 10\mathrm{m}$ from IP. The QC1 and QC2 final focus quadrupoles are drawn in yellow and pink; the a,b,c,d locations are defined. Between QC1 and QC2 there are SR masks (blue and red).

Figure 2

Closer view of the FCC-ee IR layout $\pm 3\mathrm{m}$ from IP. In front of QC1 (in violet) is the possible location to the luminometer.

Figure 3

Plot of the photon energy spectra for the radiation coming from the quadrupoles and the upstream bend magnet and incident on the central chamber for a 10 mm radius pipe. The histogram starts at 1 MeV. The yellow histogram is all that is left of the 100 keV critical energy radiation fan coming from the bend magnet. As one can see, the quadrupole radiation spectrum is significantly harder with some photons all the way out to 80 MeV for each beam bunch crossing.

Figure 4

SR from last bend upstream the IR from $-155$ to $-100\mathrm{m}$. Apertures are shown as circular with radius of 20 mm in the quads and 50 mm in the bends. The number of photons per crossing radiated by this bend towards the IP is $3.8\times {10}^{11}$ and the total energy is $1.2\times {10}^7\mathrm{GeV}$.

Figure 5

SR from bending magnets at about 600 m upstream the IR.

Figure 6

Photon total cross section as a function of energy in lead showing the contribution of different processes. Green line is at 10 keV, red line is at 100 keV. Reference [9].

Figure 7

Tantalum shielding is shown in red around the IR beam pipe from 0.5 m to 1.5 m from the IP.