Design of beam optics for the future circular collider e+e− collider rings

Abstract

A beam optics scheme has been designed for the Future Circular Collider-e + e − (FCC-ee). The main characteristics of the design are: beam energy 45 to 175 GeV, 100 km circumference with two interaction points (IPs) per ring, horizontal crossing angle of 30 mrad at the IP and the crab-waist scheme [1] with local chromaticity correction. The crab-waist scheme is implemented within the local chromaticity correction system without additional sextupoles, by reducing the strength of one of the two sextupoles for vertical chromatic correction at each side of the IP. So-called "tapering" of the magnets is applied, which scales all fields of the magnets according to the local beam energy to compensate for the effect of synchrotron radiation (SR) loss along the ring. An asymmetric layout near the interaction region reduces the critical energy of SR photons on the incoming side of the IP to values below 100 keV, while matching the geometry to the beam line of the FCC proton collider (FCC-hh) [2] as closely as possible. Sufficient transverse/longitudinal dynamic aperture (DA) has been obtained, including major dynamical effects, to assure an adequate beam lifetime in the presence of beamstrahlung and top-up injection. In particular, a momentum acceptance larger than ±2% has been obtained, which is better than the momentum acceptance of typical collider rings by about a factor of 2. The effects of the detector solenoids including their compensation elements are taken into account as well as synchrotron radiation in all magnets.The optics presented in this paper is a step toward a full conceptual design for the collider. A number of issues have been identified for further study.

High-energy high-luminosity e+e− collider using energy-recovery linacs

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In this paper we present alternative approach for Future Circular electron-positron Collider. Current 100 km circumference design with the top CM energy of 365 GeV (182.5 GeV beam energy) is based on two storage rings to circulate colliding beams [1][2]. One of the ring-ring design shortcomings is enormous power consumption needed to compensate for 100 MW of the beam energy losses for synchrotron radiation.

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“…Furthermore, our approach would allow to extend CM energy to 500 GeV (or above), which is sufficient for double-Higgs production.Introduction. The current ring-ring design of the Future Circular electron-positron Collider (FCC ee) (see [1][2][3]6] and references therein) aims to achieve the top CM energy of 365 GeV with a luminosity of 1.5-3x10 34 cm -2 s -1 using 100 MW of RF power compensating for the synchrotron radiation of the electron and position beams, which likely would result in a wall-plug AC power of 200MW. At lower energies, with the same level of RF power, the FCC ee luminosity would grow approximately as E -3.6 .…”

“…The relation between the required RF power to compensate for the beam energy losses from synchrotron radiation in an accelerator is (1) where are synchrotron radiation (SR) beam energy losses by electrons and positrons (e is the charge of positron) and are the electron and positron beam currents. The collider luminosity is then given by P SR = V SRe− I e− + V SRe+ I e+ eV SRe− ,eV SRe+ I e− , I e+ (2) where are the β-functions at the collision point, are the horizontal and vertical geometric RMS emittances, is the bunch collision energy and ~1 is so-called hour-glass effect. With a fixed RF power and equal SR losses , the maximum luminosity is attained with equal beam currents .…”

“…Furthermore, it could extend the FCC ee energy reach to the double-Higgs production energy of 500 GeV or, if needed, slightly higher. Figure 1 shows a comparison of our luminosity estimations for a ERL- 1 Beam parameter for the ring-ring FCC ee design, subject to a variety of constrains, are indeed very well optimized -see [1][2][3] for details. 2 In addition, if desired, such collider can collide polarized electron and position beams with high degree of polarization…”

Beam dynamics studies at DAΦNE: from ideas to experimental results

“…Considering high efficiency of the scheme for increasing collision luminosity and its relative simplicity for implementation several new collider projects have been proposed and are under development at present. These are the SuperKEKB Bfactory already under commissioning in Japan [12], the SuperC-Tau factory proposed in Novosibirsk and entered in the short list of Russian mega-science projects [13], the new 100-km electron-positron Future Circular Collider (FCC-ee) under design study at CERN [14], the Higgs Factory CEPC in China [15] and some others. In this paper we give a brief overview of some most relevant advanced accelerator physics studies performed at DAΦNE…”