First antineutrino energy spectrum from $^{235}$U fissions with the STEREO detector at ILL

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This article reports the measurement of the $^{235}$U-induced antineutrino spectrum shape by the STEREO experiment.

• 43'000 antineutrinos have been detected at about 10 m from the highly enriched core of the ILL reactor during 118 full days equivalent at nominal power.
• The measured inverse beta decay spectrum is unfolded to provide a pure $^{235}$U spectrum in antineutrino energy.
• A careful study of the unfolding procedure, including a cross-validation by an independent framework, has shown that no major biases are introduced by the method.