Re: [fluka-discuss]: Using info. from USRBIN
Dear Mina,
> So in principle, I should be able to add up all the values in the data file
> from the 1-D projection, multiply the total by (0.013) and get the total
> energy deposition in the upstream window (or close to it - cylindrical
> binning would have been a better choice). The slice widths in X and Y are
> both 1 cm. I get 203 Watts! So I am not converging to the total energy
> deposition I see via the simple SCORE card (58.34 Watts).
> Am I doing something wrong?
yes, your calculation is not consistent with what yourself wrote upward in
your message and turns out to be wrong by a factor of 13. Either you
multiply the *average* energy density (sum over bins ---> divided by
number of bins) by the *total* volume (0.013 cm3) or - which obviously is
in fact the same thing - you integrate by adding up the energy densities
and multiplying by the *single bin volume* (0.001 cm3).
So you have now the opposite problem: you get an underestimation of the
energy deposition in the window, that might be easily explained by the
fact that you integrate over a transverse area of 1cm2 whereas your window
has a surface almost 6 times larger (according to the radius you
reported).
As reassuring principle for any - always useful - crosscheking, SCORE
values are certainly identical to the ones obtained by a suitable USRBIN
mesh.
Ciao
Francesco
**************************************************
Francesco Cerutti
CERN-EN/STI
CH-1211 Geneva 23
Switzerland
tel. ++41 22 7678962
fax ++41 22 7668854
On Wed, 14 May 2014, Mina Nozar wrote:
> Hello everyone,
>
> I have an inconsistency which I have not been able to resolve.
> I score deposited energy distribution using USRBIN and plot the 2-D or the
> 1-D projections and extract the corresponding data files.
>
> If I plot the 2-D projection, deposited energy is averaged in the third
> dimension (over the chosen slice, if any), so to get the total deposited
> energy in some region, I would need to multiply the value in a given bin by
> the slice width and the widths of the bin for that value, correct?
>
> And if I plot the 1-D projection, deposited energy is averaged in the other
> two dimensions (over the slices I have chosen), so to get the total deposited
> energy in some region, I would need to multiply the value in a given bin by
> the width of the bin and widths of the slices in the other two dimensions.
>
> I am looking at the power deposition in the entrance and exit windows (0.013
> cm or 130 microns, so very thin) of a Rb target. The windows are discs with
> a radius of 1.35 cm. The beam is 110.5 MeV protons.
>
>
> I look at the 1D projection of the deposited energy as a function of depth
> or Z (i.e. longitudinal direction or direction of the beam). I choose a 1 cm
> slice in X and Y. I am attaching the figure (STF-PD_TopView_Z_lin.jpg).
> Results are based on 200 M primaries. The red lines are drawn at the entrance
> and exit windows and the Rb target sits in B/N. Bin width is 1 mm. I can
> see the Bragg peak in the water but do not understand the 'saw-thooth or
> step-like behaviour' of the energy deposition inside the target region. I
> see the same behavior if I look at the proton fluence as a function of proton
> energy inside the target (can send out that figure if anyone is interested).
>
> Suppose I wanted to find the total deposited energy in the upstream window.
> So I take the value at the first red line (entrance window), i.e. 1034.5
> Watts/cm^3 and multiply it by (1cm x 1cm x 0.1 cm) = 103.45 Watts.
>
> But when I look at the output files for total deposited energy in different
> volumes, I see: 58.34 Watts in the upstream window. The reason I am off here
> by almost a factor of two has to do with the coarse USBRIN binning, i.e. 1mm
> in the Z direction (while the window thickness is 0.13 mm) so I am looking at
> a larger volume than the volume of the window.
>
> I defined another usrbin card with finer binning along Z (0.001 cm bin size)
> in the upstream window region. X and Y slices are still 1 cm wide each. I
> set the max. step size to 0.01 cm. I plot the 1D projection as a function of
> Z. I have attached the figure (STF-PD_usW_Z.jpg).
>
> So in principle, I should be able to add up all the values in the data file
> from the 1-D projection, multiply the total by (0.013) and get the total
> energy deposition in the upstream window (or close to it - cylindrical
> binning would have been a better choice). The slice widths in X and Y are
> both 1 cm. I get 203 Watts! So I am not converging to the total energy
> deposition I see via the simple SCORE card (58.34 Watts).
>
> Am I doing something wrong?
>
> I am also attaching a side-view of the geometry showing target region. From
> left to right, you'll see the beam pipe, the beam pipe exit window, air gap,
> water jacket entrance window, water, target entrance window (too thin to
> see), target, target exit window (too thin to see), Target container box,
> Graphite.
>
>
> Thanks and best wishes,
> Mina
>
>
>
>
Received on Wed May 14 2014 - 10:48:14 CEST
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