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Figure 6: Fabricated spiral field Smith-Purcell generators and the measured results. (a) Photograph of the helical metagratings and the monocone transducer. (b) Measured radiated Ez field distribution and (d) phase distribution for the left-handed generator. (c) Measured radiated Ez field distribution and (e) phase distribution for the right-handed generator. The working frequency is 10 GHz.