# Calculation of residual dose close to irradiated target

Dear Experts,
my simulation setup is as following:
A brass cylinder is irradiated 5 times. each fraction lasts 2 minutes with 1.9E+8 protons per second (energy = 80MeV) with a break of 1 day minus 2 minutes in between.
I want to score the residual dose in a water sphere (r=1.2cm) approx. 6cm behind the cylinder, 10min after each fraction and an hour after the last one.
The results I get seem much too high.
Michael
eye_collimator.flair (7.2 KB)

Dear @michael.deutsch,

Could you elaborate a little bit on what do you get and what were you expecting? This way may be easier to spot the problem.

In the meanwhile (and just in case), make sure that you are applying the correct normalization. You are requesting residual equivalent dose for few cooling times, which means that your results are expressed per unit time instead than per primary weight (take a look to note 7 on the RADDECAY entry of the manual: RADDECAY | FLUKA). In addition to this, you are using a Region-type USRBIN, which means that your results are not normalized per volume, instead you are getting an integral quantity (see note 13 in the USRBIN entry of the manual: USRBIN | FLUKA). Therefore I expect the results from FLUKA to be in pSv \cdot cm ^3 / s so you would need to divide them by the volume of your sphere to get pSv/s.

Kind regards,
Francisco

Dear @fogallar,
the normalization was wrong. I somehow messed up with the units (multiplying by particle rate, dividing by volume… ).
Thanks a lot!