<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=us-ascii"> <STYLE> BLOCKQUOTE { MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; MARGIN-LEFT: 2em } OL { MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px } UL { MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px } P { MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px } BODY { FONT-SIZE: 10.5pt; COLOR: #000000; LINE-HEIGHT: 1.5; FONT-FAMILY: Tahoma } </STYLE> <META content="MSHTML 6.00.6000.21348" name=GENERATOR></HEAD> <BODY style="MARGIN: 10px"> <DIV>Hi Gate users, <DIV> </DIV> <DIV>I want to confirm whether I can separate one whole crystal into two pieces in simulation but get the same result. The black is detector. One is a whole crystal with L length, and the other is two L/2 length crystals have the boundary in red.</DIV> <DIV> </DIV> <DIV>There is no definition of the boundary or surface for the boundary in red in my geometry. Based on the user-guide for optical simulation, photons may just get though the boundary without reflection, just like the whole crystal. Am I right?</DIV> <DIV> </DIV> <DIV>I got the two results. One got 3389 photons in 10132 singles, and the other got 3390 photons in 10199 singles. (Other photons were killed on the surface of the reflector in green). I am not sure the reason of the little difference. The red boundary, or just random initialization?</DIV></DIV> <DIV> </DIV> <DIV>Anyone has ideas? Thanks</DIV> <DIV><IMG src="cid:_Foxmail.0@82AB461C-454D-43C0-9758-FCB307A7AFA2"></DIV> <HR style="WIDTH: 210px; HEIGHT: 1px" align=left color=#b5c4df SIZE=1> <DIV><SPAN>Han</SPAN></DIV></BODY></HTML>