The Radioactive Source Calibration System of the PROSPECT Reactor Antineutrino Detector

The Precision Reactor Oscillation and Spectrum ( PROSPECT) Experiment is a reactor neutrino experiment designedto search for eV-scale sterile neutrinosand measure the spectrum of electron antineutrinos from a highly-enriched $^{235}$U nuclear reactor. The PROSPECTdetector consists of an 11 by 14 array of optical segments in $^{6}$Li-loaded liquid scintillator at the High Flux Isotope Reactorin Oak Ridge National Laboratory. Antineutrino events are identified via inverse beta decayand read out by photomultipliertubes located at the ends of each segment. The detector response is characterized using a radioactive sourcecalibration system. This paper describes the design, operation, and performance of the PROSPECTsource calibration system.