  The Low-Energy X-ray Polarization Detector (LPD) is one of the payloads in
the POLAR-2 experiment, designed as an external payload for the China Space
Station (CSS) deployment in early 2024. LPD is specifically designed to observe
the polarization of Gamma-Ray Bursts (GRBs) prompt emission in the energy range
of 2-10 keV, with a wide field of view (FoV) of 90 degrees in preliminary
design. This observation is achieved using an array of X-ray photoelectric
polarimeters based on gas pixel detectors. Due to the wide FoV configuration,
the in-orbit background count rate in the soft X-ray range is high, while GRBs
themselves also exhibit a high flux in this energy band. In order to assess the
contribution of various background components to the total count rate, we
conducted detailed simulations using the GEANT4 C++ package. Our simulations
encompassed the main interactions within the instrument materials and provided
insights into various background components within the wide FoV scheme. The
simulation results reveal that among the background components, the primary
contributors are the cosmic X-ray background (CXB) and bright X-ray sources.
The total background count rate of LPD, after applying the charged particle
background rejection algorithm, is approximately 0.55 counts/cm^2/s on average,
and it varies with the detector's orbit and pointing direction. Furthermore, we
performed comprehensive simulations and comparative analyses of the CXB and
X-ray bright sources under different FoVs and detector pointings. These
analyses provide valuable insights into the background characteristic for soft
X-ray polarimeter with wide FoV.
