2026AJ....171...51H

We report a narrowband technosignature search toward five Milky Way globular clusters-NGC 6171, NGC 6218, NGC 6254, NGC 6838, and IC 1276-using Five-hundred-meter Aperture Spherical radio Telescope (FAST)'s 19 beam L-band receiver (1.05-1.45 GHz). We adapted MultiBeam Point-source Scanning (MBPS) to extended targets by gating detections to generalized on-target windows (gOTWs), i.e., the time intervals when a beam's main lobe intersects a buffered cluster mask, and by enforcing the deterministic multibeam illumination sequence as a geometry test. Spectra at Δν ≈ 7.5 Hz resolution and Δt ≈ 10 s cadence were searched with turboSETI over $| \dot{\nu }| \leqslant 4\,{\rm{Hz}}\,{{\rm{s}}}^{-1}$ at S/N ≥ 10. From 2.75 × 10⁵ raw hits across both linear polarizations, none survived the gOTW gating, array-wide simultaneity veto, in-stripe ordering, and single-drift coherence checks, yielding a robust null result. With SEFD ≈ 1.5 Jy and an effective ∼60 s per illuminated crossing, our per-crossing flux density threshold is ${S}_{\min }\approx 0.50$ Jy, corresponding to ${{\rm{EIRP}}}_{\min }\approx (0.72\,\unicode{x02013}\,1.8)\times 1{0}^{16}$ W for cluster distances of 4-6.5 kpc; when multiple illuminated crossings occur, noncoherent stacking improves sensitivity by up to $\sqrt{N}$. To our knowledge, this is the first FAST technosignature survey dedicated to globular clusters and the first to use MBPS as the primary observing strategy. These limits disfavour bright, persistent, isotropic L-band beacons above the stated thresholds during our epochs and establish a scalable blueprint-geometry-aware gating and verification-for multiepoch MBPS campaigns that expand signal morphologies and combine passes to deepen constraints on transmitters in dense stellar systems.