# Dose and distance

Dear Fluka users

I am interested in investigating dose dependence on the distance so I need to score the dose at the increasing distance from the source. However, I am not sure how I should this except scoring in different regions.

Ma y I ask how is the dose score in the increasing distance away from the source?

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Dear @Motlatsi_Vincent,

I think a standard USRBIN scoring would be the easiest to use in your case.

Cheers,
David

I have run the test simulation to investigate the dose dependence on the distance. However, I am not sure if I have done it the correct way. I need to confirm all that I did so I attach my input file and plot for assistance. Please also check my normalization, I have normalized the result to uSv/hr.TestSimulation(Co-60).flair (2.5 KB)

I will appreciate any assistance

Thank you

Dear @Motlatsi_Vincent,

your input file looks correct to me. However there are some issues with the plotting.

1. The 1D Projection along the Z axis will give you the average value in the X-Y plane for a given Z value. You need to limit the X and Y close to the Z axis to give the local value. Alternatively you could use the 1D Max option, which will give you the maximum value in the X-Y plane for a given Z value.

2. The unit conversion between pSv/s and uSv/h is incorrect. The correct normalization factor is: 3600*1e-6 or 3600/1e6. Of course this has to be multiplied with the activity of the source as well.

Cheers,
David

Thank you for your response. That was very constructive. I got one more question though.

Considering that my plotting is 1D Projection along z-axis, in the input, I have set Z_{min} and Z_{max}.
Am I correct to say that I get the plot of the average value of H*(10) in the X-Y plane for the Z value ranging from Z_{min} to Z_{max} ? I just want to understand the first sentence on issue no1.

If my understanding is correct, I can therefore estimate H*(10) at the point Z by setting Z_{min} and Z_{max} very very close to my point of interest Z.

Not really.
For a 1D Projection along the z-axis, you need to set the x and y intervals defining the transverse area over which your quantity shall be averaged (otherwise, it will be averaged over the whole xy scoring area, and will get lower). The plot will extend over the whole z interval you input in the USRBIN card (in principle with no need for limiting it at plotting level), with the resolution you asked for by means of the requested number of z bins. In this sense, you cannot look â€śvery very closeâ€ť to your point of interest, because the resolution is determined beforehand by the z bin width (for each z bin, you get a value averaged over the latter, not referring to a single point).
If you select instead the 1D Max option, you will see, for each z bin, the max value of your quantity in the xy plane.
Keep in mind that the scored quantity is always its average over the dx dy dz volume. In practice, a suitably small volume can give a reasonable approximation of a point value.

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A post was split to a new topic: Dose equivalent rate vs shielding thickness