|Message: Re: GPS negative z-direction||Not Logged In (login)|
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On Thu, 29 Sep 2011 00:51:24 GMT, matthew wrote:
> I am trying to transport a 2-D beam of thermal neutrons through my geometry, but for some reason all the neutrons move away from my detector instead of toward it. > > The code is as follows: > /gps/verbose 0 > /gps/particle neutron > /gps/direction 0 0 1 > # > # the incident surface is in the y-z plane > /gps/pos/type Beam > /gps/pos/shape Circle > /gps/pos/radius 2.54 cm > /gps/pos/centre 0.0 0.0 0.0 m > # > # set the focusing point, default is (0, 0, 0) > /gps/ang/type beam2d > # Set the energy distribution > /gps/energy 0.025 eV > > I thought I could just change the third line of code to > > /gps/direction 0 0 -1 > > but that did not fix the problem. I'm obviously misunderstanding something. What am I doing wrong? >The command "/gps/ang/type beam2d" overwrites "/gps/direction" and redefines the angular distribution. To change the direction of the beam, you have to use the commands "/gps/ang/rot1" and "/gps/ang/rot2". The GPS users manual provides you more details:
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