HIGS2: The Next Generation Compton γ-ray Source

This document provides a prospectus of research opportunities created by an intensity upgrade to the High Intensity Gamma-ray Source (HIGS) at the Triangle Universities Nuclear Laboratory (TUNL). The current maximum gamma-ray intensity on target at the HIGS is more than 108 γ/s in the energy range between 9 and 12 MeV. An increase of total intensity of about two orders of magnitude will be achieved using a high average-power Fabry-Perot resonator driven by an external laser. This next generation Compton γ-ray source, the HIGS2, with fast helicity reversal capability and low beam-energy spread, will open opportunities for experiments in hadronic parity violation, nuclear astrophysics and nuclear structure, and will make possible long-baseline searches for dark-matter particles. The upgrade is based on well established technologies, and will interrupt operation of the HIGS for less than one year for implementation. This document outlines the research opportunities and describes the HIGS2 facility.