Hi guys, I have some questions about this detector. So i have a project about this detector, i made some experiments, made some graphs, answering to some questions, but one questions is struggling me. How can we avoid to calculate the solid angle, i mean in what situations??? In my lab documents i have this formula: omega`/4*pi=1/2(1-1/(sqrt(1+b^2/4D^2)) where D is the distance from detector and radioactive source, b is the diametre of circular window of the detector. However, i used a radioactive source with bigger diametre than b so i must mutiple that formula with 8D^2/d^2(1-1/(sqrt(1+d^2/4D^2)) where d is the diametre of the source So omega/4*pi=omega`*4pi/the above formula^. So, this is my answer: When the distance is almost 0, 8D^2/d^2(1-1/(sqrt(1+d^2/4D^2)) becomes 0, so the omega angle is 0. Its my answer good??? Are there more answers ??? Sorry for my english, but its not my first language. Thanks for any help!