[Gate-users] Hollow sphere (shell) in water phantom: is it empty or filled with water?

[Marc Chamberland]

Hi Gate Users!

If I have a water phantom and I add a daughter phantom made out of  
gold in the shape of a hollow sphere (basically, a shell; I define  
rmax and rmin for the sphere) and place this shell in the centre of  
the water phantom, is the inside of the sphere filled with water? Or  
is it empty (vaccuum)? Is there a way to know what the material INSIDE  
the sphere/shell is?

I have a second question, but I could probably figure it out by  
myself. However, if someone feels like answering, it would be great:  
if I confine a source to a hollow sphere, does the source need to be  
within the walls of the sphere, or can it be placed in the centre  
(hollow part) of the sphere?

I would greatly appreciate it if someone could answer my first  
question. Thank you very much in advance!

Marc