First Experimental Demonstration of Beam Storage by Three-Dimensional Spiral Injection Scheme for Ultra-Compact Storage Rings

Three-dimensional spiral injection enables beam storage in ultra-compact rings with nanosecond revolution periods. We report first storage of a $297\mathrm{k}\mathrm{e}\mathrm{V}\mathrm{/}c$ electron beam in a $22\mathrm{c}\mathrm{m}$ weak-focusing ring with a $4.7\mathrm{n}\mathrm{s}$ revolution period using a $140\mathrm{n}\mathrm{s}$ kicker pulse. A scintillating-fiber detector observes signals $>5\sigma$ above noise for $\ge 1\mu \mathrm{s}$, and varying the weak-focusing field potential shifts the stored-beam region, consistent with Monte Carlo predictions, validating beam storage. This proof-of-principle opens a path to ultra-compact storage rings for next-generation precision measurements.