  The GEM-based neutron detector has flourished in the past decade. However
almost all the GEM-based neutron detectors work in the flow-gas mode, and the
long-term performances of the detectors may be unstable due to the dynamic
changes of atmospheric pressure and ambient temperature. In this paper, a
sealed ceramic GEM-based neutron detector was developed at China Spallation
Neutron Source (CSNS) and its sensitive area was 100 mm * 100 mm. The
characterizations of the detector were presented and discussed, which included
the plateau curve, the neutron beam profile, the neutron wavelength spectrum,
the spatial resolution (FWHM: 2.77 mm), the two-dimensional (2D) imaging
ability, the neutron detection efficiency and the counting rate instability
(Relative Standard Deviation (RSD): 0.7%). The results show that the detector
has good performances in sealed mode, and it can be used for the measurement of
the direct neutron beam at CSNS.
