Development of a magnetometer system to monitor stray magnetic fields near PROSPECT detector

PROSPECT is a reactor antineutrino experiment located in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). PROSPECT's primary goals are to probe short-baseline oscillations and perform a precise measurement of the U-235 reactor antineutrino spectrum. The detector consists of 154 segmented cells filled with $^6$Li-doped liquid scintillator. Each segment holds two PMTs, one on each end of the cell. The PMTs can be exposed to stray magnetic fields from superconducting magnets operating on the experiment hall one floor below the detector. The monitoring of the magnetic fields is an important part of our background characterization as the magnetic fields can directly influence the energy measurement. This study presents the characterization and monitoring of stray magnetic fields using a compact, low cost system of triple axis magnetometers near the PROSPECT detector. Applications of magnetic field monitoring system in other areas of physics will also be discussed.