Charge-Reversal-Based Extraction of Muonic Ions

Abstract: Negative muon capture in matter is accompanied by Auger electron emission and the formation of positively charged muonic ions. This charge reversal provides a possibility for electromagnetic extraction of the products of muon capture. Here we propose a charge-reversal-based extraction scheme for muonic ions, in which negative muons are moderated and confined in a dilute gas environment before conversion, and the resulting muonic ions are subsequently accelerated and extracted by electrostatic fields. The feasibility of the concept is investigated through order-of-magnitude estimates of the competing processes, including muon moderation, muonic-ion formation, charge exchange, and acceleration in the gas medium. A magnetic--electrostatic conditioning scheme is proposed to reduce the spatial and momentum spreads of practical low-energy muon beams while maintaining sufficient directed motion for transport into the capture region. The analysis indicates that muonic-ion formation and extraction within the muon lifetime are not excluded by fundamental timescale constraints, although the quantitative efficiency remains uncertain because several relevant low-energy stopping, scattering, capture, and charge-state processes are poorly constrained experimentally.