Longitudinal and transverse compression of stopped positive muons in helium gas

What changed

The muCool team demonstrated separate longitudinal and transverse compression stages for positive muons stopped in helium gas. Bao and colleagues used electric fields to concentrate the stopping distribution along a magnetic field. Antognini and colleagues later used a cryogenic density gradient and crossed fields to obtain transverse convergence. Decay-positron time spectra, control conditions and collision simulations supported both demonstrations. The inferred final sizes and compression times were obtained through those models rather than direct complete beam tomography.

Scientific scope

The muCool team demonstrated separate longitudinal and transverse compression stages for positive muons stopped in helium gas. Bao and colleagues used electric fields to concentrate the stopping distribution along a magnetic field. Antognini and colleagues later used a cryogenic density gradient and crossed fields to obtain transverse convergence. Decay-positron time spectra, control conditions and collision simulations supported both demonstrations. The inferred final sizes and compression times were obtained through those models rather than direct complete beam tomography. The two experiments tested separate stages under different gas and injection conditions. Their proposed combined ten-order phase-space improvement required subsequent integration, extraction and reacceleration. Small final dimensions, efficiencies and momentum spreads include simulation assumptions, decay losses, detector acceptance and fitted alignment or impurity effects. This family does not establish a completed six-dimensional cooling and acceleration chain or directly measured universal compression factors.

Evidence

The linked original works support the scoped statement and contribution attribution. WRS has not independently replayed experiments or reconstructed a full mathematical proof. The two experiments tested separate stages under different gas and injection conditions. Their proposed combined ten-order phase-space improvement required subsequent integration, extraction and reacceleration. Small final dimensions, efficiencies and momentum spreads include simulation assumptions, decay losses, detector acceptance and fitted alignment or impurity effects. This family does not establish a completed six-dimensional cooling and acceleration chain or directly measured universal compression factors.

Contributors

• The named authors in the research record · SCIENCE: These are the listed authors of the cited contribution sources. Paper authorship does not quantify individual effort. An incomplete list is explicitly marked; same names are not automatically merged.

• Muon cooling: longitudinal compression (arXiv1402.2418v1)
• Demonstration of Muon-Beam Transverse Phase-Space Compression (arXiv2003.11986v2)

Provisional WRS assessment, edition 2026-10-28.1. Independent expert calibration is pending. This grade does not certify correctness or assign ownership.

Full scientific record · Browse contribution grades · Request a correction