  We study the radiation effects of the Low Gain Avalanche Detector (LGAD)
sensors developed by the Institute of High Energy Physics (IHEP) and the Novel
Device Laboratory (NDL) of Beijing Normal University in China. These new
sensors have been irradiated at the China Institute of Atomic Energy (CIAE)
using 100 MeV proton beam with five different fluences from 7$\times10^{14}$
$n_{eq}/cm^2$ up to 4.5$\times10^{15}$ $n_{eq}/cm^2$. The result shows the
effective doping concentration in the gain layer decreases with the increase of
irradiation fluence, as expected by the acceptor removal mechanism. By
comparing data and model gives the acceptor removal coefficient $c_{A}$ =
$(6.07\pm0.70)\times10^{-16}~cm^2$, which indicates the NDL sensor has fairly
good radiation resistance.
