  An array of sixteen laser-pumped scalar Cs magnetometers was part of the
neutron electric dipole moment (nEDM) experiment taking data at the Paul
Scherrer Institute in 2015 and 2016. It was deployed to measure the gradients
of the experiment's magnetic field and to monitor their temporal evolution. The
originality of the array lies in its compact design, in which a single
near-infrared diode laser drives all magnetometers that are located in a
high-vacuum chamber, with a selection of the sensors mounted on a high-voltage
electrode. We describe details of the Cs sensors' construction and modes of
operation, emphasizing the accuracy and sensitivity of the magnetic field
readout. We present two applications of the magnetometer array directly
beneficial to the nEDM experiment: (i) the implementation of a strategy to
correct for the drift of the vertical magnetic field gradient and (ii) a
procedure to homogenize the magnetic field. The first reduces the uncertainty
of the new nEDM result. The second enables transverse neutron spin relaxation
times exceeding 1500 s, improving the statistical sensitivity of the nEDM
experiment by about 35% and effectively increasing the rate of nEDM data taking
by a factor of 1.8.

Atomic Physics;High Energy Physics - Experiment;Nuclear Experiment