Speaker
Description
A 550 GeV centre-of-mass Higgs factory is presented, the Linear Ghost Collider (LGC). Acceleration and deceleration is performed within an SRF linac where the bunches transported are net neutral, termed ghost bunches. Within these, one charge partner accelerates, and the other decelerates. In this way energy is recovered after collision, and all particles recycled. An accompanying plenary talk - Ghost Collider (GC) - introduces this concept. LGC comprises an improved configuration to GC that eliminates turn-around arcs. This enables a large reduction in energy lost to synchrotron radiation, and an increase in luminosity as bunches are degraded less, in comparison to GC. Lacking arcs, LGC can therefore be considered as a luminosity upgrade of a pre-built LC. The key innovation is that within a ghost bunch only the velocities of the charge partners must match, not their energies. Therefore, only one charge partner need be accelerated to collision energy. This allows the linac to be split into stages, with the other charge partners only accelerated to collision energy divided by the number of stages - these are termed drive bunches. Recirculation is only needed for drive, not colliding, bunches. As with GC, collisions are arranged between net neutral bunches, this strategy of charge compensation of beamsstrahlung with small disruption allows the energy recovery and re-use of spent colliding bunches. Two variants of LGC are presented: firstly, a pulsed version analogous to GC realisable with existing SRF technology and capable of $34.6\times 10^{34}$ cm$^{-2}$ s$^{-1}$ @ <100 MW electrical power for RF with disruption parameter 2.25; and secondly, a continuous-wave (CW) version based on expected parameters for thin-film $\textrm{Nb}_3\textrm{Sn}$ on copper SRF technology, capable of $348\times 10^{34}$ cm$^{-2}$ s$^{-1}$ @ 160 MW electrical power for RF with disruption parameter 1.48. We compare these values to established collider proposals, and scale to $380$~GeV and $250$~GeV centre-of-mass energies, showing their attractiveness over a large parameter range.