  A high-efficiency fast neutron detector prototype based on a triple Gas
Electron Multiplier (GEM) detector, which coupled with a novel multi-layered
High-Density PolyEthylene (HDPE) as a neutron-to-proton converter for improving
the neutron detection efficiency, is introduced and tested with the Am-Be
neutron source in Institute of Modern Physics (IMP) at Lanzhou in present work.
Firstly, the developed triple GEM detector is tested by measuring its effective
gain and energy resolution with $^{55}$Fe X-ray source to ensure that it has a
good performance. The effective gain and obtained energy resolution is
5.0$\times$10$^{4}$ and around of 19.2\%, respectively. And secondly, the novel
multi-layered HDPE converter is coupled with the cathode of the triple GEM
detector make it a high-effective fast neutron detector. And its effective
neutron response is four times higher than that of the traditional
single-layered conversion technique when the converter layer number is 38.
