Simulate gamma spectra?

Dear fluka experts,
   Thanks again for your last help. Now I could simply simulate the TEPC
microdosimetric spectra in monoenergy gamma or neutron field. But I
still encountered some problems in the simulation result.
   when I simulated the spectra in gamma source, I found out that
spectra shape was not so continuous in low linear energy edge as that in
high linear edge. Firstly, I thought the reason may be the poor
statistic; so, I increased the primary particle number. And then, I saw
that the high edge shape was better but not for the low edge shape. I
have attached the graph, please check it and help me find the reason,
thank you!
   And also I pasted the neutron source spectra in that graph file. when
I simulated the spectra in monoenergy neutron source, I found that there
were two discrete peaks and the shape wasn't similar with your 0.5MeV
spectra. Could you check it,please? And, I also attached the input
files.
Best Regards,
                               sincerely,
                               Zhang Weihua