Whitepaper submitted to Snowmass21: Advanced accelerator linear collider demonstration facility at intermediate energy

Abstract

It is widely accepted that the next lepton collider beyond a Higgs factory would require center-of-mass energy of the order of up to 15 TeV. Since, given reasonable space and cost restrictions, conventional accelerator technology reaches its limits near this energy, high-gradient advanced acceleration concepts are attractive. Advanced and novel accelerators (ANAs) are leading candidates due to their ability to produce acceleration gradients on the order of 1-100 GV/m, leading to compact acceleration structures. Over the last 10-15 years significant progress has been achieved in accelerating electron beams by ANAs. For example, the demonstration of several-GeV electron beams from laser-powered capillary discharge waveguides, as well as the proof-of-principle coupling of two accelerating structures powered by different laser pulses, has increased interest in ANAs as a viable technology to be considered for a compact, TeV-class, lepton linear collider.However, intermediate facilities are required to test the technology and demonstrate key subsystems. A 20-100 GeV center-of-mass energy ANA-based lepton collider can be a possible candidate for an intermediate facility. Apart from being a test beam facility for accelerator and detector studies, this collider will provide opportunities to study muon and proton beam acceleration, investigate charged particle interactions with extreme electromagnetic fields (relevant for beam delivery system designs and to study the physics at the interaction point), as well as precision Quantum Chromodynamics and Beyond the Standard Model physics measurements. Possible applications of this collider include the studies of γγ and e-ion collider designs.The advanced accelerator and HEP communities propose the following recommendations to the Snowmass conveners:1. The research continue on the science case for the intermediate facility in the framework of the General Accelerator R&D (GARD) program.

Laser polarization control of ionization-injected electron beams and x-ray radiation in laser wakefield accelerators

“…These improvements are required in view, e.g. of the necessary staging of plasma accelerators [14,17,21,27] to reach electron energies in excess of a TeV and sufficient luminosity for high-energy physics collider experiments [28,29]. Precise control of the electron properties is naturally difficult due to the transient nature of the plasma in which the LWFA process takes place.…”