  Magnetic fields are ubiquitous in our Universe, but remain poorly understood
in many branches of astrophysics. A key tool for inferring astrophysical
magnetic field properties is dust emission polarimetry. The James Clerk Maxwell
Telescope (JCMT) is planning a new 850$\mu$m camera consisting of an array of
7272 paired Microwave Kinetic Inductance Detectors (MKIDs), which will
inherently acquire linear polarization information. The camera will allow
wide-area polarization mapping of dust emission at
14$^{\prime\prime}$-resolution, allowing magnetic field properties to be
studied in a wide range of environments, including all stages of the star
formation process, Asymptotic Giant Branch stellar envelopes and planetary
nebula, external galaxies including starburst galaxies and analogues for the
Milky Way, and the environments of active galactic nuclei (AGN). Time domain
studies of AGN and protostellar polarization variability will also become
practicable. Studies of the polarization properties of the interstellar medium
will also allow detailed investigation of dust grain properties and physics.
These investigations would benefit from a potential future upgrade adding
450$\mu$m capability to the camera, which would allow inference of spectral
indices for polarized dust emission in a range of environments. The enhanced
mapping speed and polarization capabilities of the new camera will transform
the JCMT into a true submillimetre polarization survey instrument, offering the
potential to revolutionize our understanding of magnetic fields in the cold
Universe.
