  AC-Coupled LGAD (AC-LGAD) is a new 4D detector developed based on the Low
Gain Avalanche Diode (LGAD) technology, which can accurately measure the time
and spatial information of particles. The Institute of High Energy Physics
(IHEP) designed a large-size AC-LGAD with a pitch of 2000~\SI{}{\micro\metre}
and AC pad of 1000~\SI{}{\micro\metre}, and explored the effect of N+ layer
dose on the spatial resolution and time resolution. The spatial resolution
varied from 36~\SI{}{\micro\metre} to 16~\SI{}{\micro\metre} depending on N+
dose for a charge corresponding to about 12 minimum ionizing particles. The
jitter component of the time resolution does not change significantly with
different N+ doses, and it is about 15-17 ps measured by laser. The AC-LGAD
with a low N+ dose has a large attenuation factor and better spatial resolution
in the central region between pads. In these specific conditions, large signal
attenuation factor and low noise level are beneficial to improve the spatial
resolution of the AC-LGAD sensor.
