|Message: Normalization of an isotropic flux in space||Not Logged In (login)|
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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/pos/radius 50.0 m ---> R
/gps/pos/centre 0.0 0.0 0.0 mm
/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
- 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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