Message: Normalization of an isotropic flux in space  Not Logged In (login) 
Dear all,
I am simulating the interaction of a space telescope with the cosmic ray environment and, after a long discussion with my colleagues, I am a bit confused on the normalization process that translates the number of counts in my detector in unity of counts/cm^2 sec. So I really appreciate if somebody could help me to clarify this topic! I show here what is my normalization way. I have an isotropic proton flux F: F = prot /cm^2 sec sr I run the protons from a sphere of radius R within an half cone angle q to increase the statistics. My spacecraft is placed within the emission angle, that is the spacecraft is placed within the sphere of radius r, with r = tan(q) x R The GPS macro is: /gps/particle proton /gps/pos/type Surface /gps/pos/shape Sphere /gps/pos/radius 50.0 m > R /gps/pos/centre 0.0 0.0 0.0 mm /gps/ang/type iso /gps/ang/mintheta 0 rad /gps/ang/maxtheta 0.01 rad > q while the spectral shape is made via /gps/hist . At the end of the run, I detect a number of counts C on the focal plane. If N is the number of emitted protons, we call the fraction of detected/emitted particles Eff: Eff = C/N In order to trasform the number C to a rate P in counts/sec, I apply this formula: P = Eff x F x (4 x PI) x PI x r^2 counts/sec Then I divide the count rate P by the detecting area Adet, and the final flux B is given by: B = P/Adet counts/cm^2 sec The same normalization can be achieved using the simulation time: D = F x A_sphere x omega prot/sec where:  A_sphere = 4 x PI x R^2 (the source sphere)  omega = 2 x PI x (1  cos(q)) (solide angle of the emission cone) Then we calculate the simulated time: Time = N/D (sec) The flux B on the focal plane is given by: B = C/(Time x Adet) counts/cm^2 sec My normalization way is based on what shown by Sullivan (1971). Now my question is: is this the right way? Thank you all for the help! Best regards, Valentina

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