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From: Francesco Cerutti <Francesco.Cerutti_at_cern.ch>

Date: Wed, 14 May 2014 09:24:56 +0200

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

Date: Wed, 14 May 2014 09:24:56 +0200

Dear Mina,

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:

Received on Wed May 14 2014 - 10:48:14 CEST

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