Speaker
Description
The primary disadvantage of linear $e^+e^-$ colliders is their inherent energy inefficiency: after a single collision, the bunches are directed into a beam dump. Although the use of superconducting energy recovery linacs (ERL) was proposed half a century ago to address this issue, by 1980 it was realized that this concept could not be implemented because of parasitic collisions between accelerating and decelerating beams within the linac. The resulting requirement of having only one bunch in a long linac leads to a low collision frequency, yielding a luminosity significantly lower than that of single-pass colliders (such as ILC or CLIC).
In 2021, the author proposed a twin superconducting collider concept, where accelerating and decelerating beams travel in parallel linacs coupled via RF fields. This configuration enables full energy exchange while avoiding beam-beam interactions within the accelerating structures. Consequently, the advantages of superconducting ERLs are fully realized. The luminosity is primarily limited by the power required for heat removal due to RF cavity losses (quality factor) and higher-order mode (HOM) losses in the accelerating structures, as well as by beam-beam effects.
Two schemes are considered:
1. An $e^+e^−$(or $e^−e^−$) collider with continuous or pulsed (duty cycle) bunch operation. In this scheme, bunches are accelerated, collided, decelerated to ~5 GeV, and then recirculated through turnaround arcs, compressors, decompressors, and damping wigglers for reinjection.
2. An $e^−e^−$ collider with single-pass use of low-emittance electrons, which offers a simplified technical design and allows for higher luminosity per collision.
At a total power consumption of 150–300 MW and center-of-mass energies of 2E$_0$=250–500 GeV, the attainable luminosity reaches (1−2)10$^{36}$ cm$^{-2}$s$^{-1}$ for the first scheme and (3−7)10$^{36}$ cm$^{-2}$s$^{-1}$ for the second. These values are two orders of magnitude higher than those of the ILC and an order of magnitude higher than FCC-ee (at 2E$_0$=250 GeV, where 500 GeV operation is unfeasible for ring colliders). Given its capability for operation at 500 GeV, which is essential for Higgs self-coupling measurements, and its ultra-high luminosity, the ERLC is undoubtedly the superior candidate for a Higgs factory.
