An 8 GeV Linac as the Booster Replacement in the Fermilab Power Upgrade: a Snowmass 2021 White Paper

Following the PIP-II 800 MeV Linac, Fermilab will need an accelerator that extends from that linac to the MI injection energy of ~8 GeV, completing the modernization of the Fermilab high-intensity accelerator complex. This will maximize the beam available for neutrino production for the long baseline DUNE experiment to greater than 2.5 MW and enable a next generation of intensity frontier experiments. In this white paper, we propose an 8 GeV Linac for that purpose. The Linac consists of an extension of the PIP-II Linac to 2.4 GeV using PIP-II 650 MHz SRF cryomodules, followed by a 2.4-->8.0 GeV Linac composed of 1300 MHz SRF cryomodules, based upon the LCLS-II cryomodules developed at Fermilab. The 8 GeV Linac will incorporate recent improvements in SRF technology. The research needed to implement this Linac is described.Comment: contribution to Snowmass 202

Pack light on the move: Exploitation and exploration in a dynamic environment

This paper revisits a recent study by Posen and Levinthal (Man Sci 58:587–601, 2012) on the exploration/exploitation tradeoff for a multi- armed bandit problem, where the reward probabilities undergo random shocks. We show that their analysis suffers two shortcomings: it assumes that learning is based on stale evidence, and it overlooks the steady state. We let the learning rule endogenously discard stale evidence, and we perform the long run analyses. The comparative study demonstrates that some of their conclusions must be qualified

Key directions for research and development of superconducting radio frequency cavities

Radio frequency superconductivity is a cornerstone technology for many future HEP particle accelerators and experiments from colliders to proton drivers for neutrino facilities to searches for dark matter. While the performance of superconducting RF (SRF) cavities has improved significantly over the last decades, and the SRF technology has enabled new applications, the proposed HEP facilities and experiments pose new challenges. To address these challenges, the field continues to generate new ideas and there seems to be a vast room for improvements. In this paper we discuss the key research directions that are aligned with and address the future HEP needs.Comment: contribution to Snowmass 202