[gate-users] GPS confine command

D.J. van der Laan d.j.vanderlaan at tnw.tudelft.nl
Tue Sep 27 15:50:35 CEST 2005


> Greetings
> I am trying to understand the essence of the GPS command confine command.
> Suppose I use confine=vol_p where my vol is a half cylinder and my source
> is a box source ( hypothetically) What happpens with the points that are
> not in the intersection of the source (box) and vol (half cylinder ) ?
> Will there  be any emmisions from those points ? Here my box source
> encloses the halfcylinder.

When using the confine command, the primary generator first selects a
random  point in the source (in this case the rectangle). It then checks
if this point is within the confinement (the cylinder). If this is not 
the case another point is selected etc. If it is within the confinement 
a primary is generated on this point.

Emmission therefore only occur from the intersection of both volumes.

> Please I would like someone with more insight into these to comment. I am
> saying so cos I can't find gps commands that can be used for creating
> sources shaped like half cylinders .

You can use a confinement to define a half-cylinder source. You could, 
for example, choose a complete cylinder as your source, and confine it 
to the half-cylinder phantom. However, it is better if you choose you 
source volume as close a possible to the volume of the confinement. 
Otherwise, the loop - generate position, check if position is inside 
confinement, if not generate new position - can slow down your simulation.

Hope it helps.



> Cheers
> Theo
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D.J. van der Laan
Delft University of Technology
Mekelweg 15, room 2.00.020
2629 JB Delft
The Netherlands

E: d.j.vanderlaan at tnw.tudelft.nl
T: +31 15 2783776
F: +31 15 2789011

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