Re: [fluka-discuss]: heavy ion dose scoring

From: Sunil C <csunil11_at_gmail.com>
Date: Thu, 4 Dec 2014 10:46:34 +0530

Dear Roxana

Your input is good, except I notice that you have an irradiation profile
card which does not help just by itself. If you are interested in scoring a
time profile result (such as induced activity or residual dose rates ), you
must use raddecay, dcyscore and dcytimes and associate your scoring cards
with the dcytimes cards.But I presume this is not what you want since you
are looking for the prompt neutron dose (for shielding purposes, I gather)
and your irradiation profile card was meant to obtain the neutron dose rate
for a given beam current since you mention the beam loss number in it.

I suggest removing the irradiation profile card, run simulations and obtain
the dose results in pSv/primary. You can then convert it for your loss
scenario. This also has an advantage that, if the beam loss scenarios are
changed (a distinct possibility in the nascent stage of accelerator
radiation shielding calculations), this number (or dose rate per unit beam
current) alone is sufficient to calculate the new dose rates,shielded or
not, as the dose rates scale linearly with the beam loss (beam current).
Thus, obtain psv/ion, multiply it by the primaries per second (2.5e7
ions/s in your case) and multiply by 3600 (s/h) to get pSv/h.Factor in the
1e-3 and you have microSv/h for your beam loss number.

With flair, you can modify the usrbin results by multiplying with the
(above) factor so that you obtain plots with units in microsv/h (instead of
pSv/primary), and it should look like the one you had attached in one of
your mails. Here, I attach a plot obtained with your input with 5e4
primaries, in units of pSv/p (with some juggling in the range of values
plotted) but without the irradiation profile card. The pattern is evidently
similar to the other plot.

I can also see that your stainless steel composition looks a tad
incomplete. For the purpose of neutron production, it should be OK to use
just a few element composition (and you have listed the major ones) but in
case you also would like to calculate the induced activity or residual dose
rate at a later stage, it is better to use a composition that is accurate
upto the trace levels. Stainless steel can be a nasty object from the
induced activity point of view.

FLUKA very well reproduces the neutron and photon doses from heavy ion
interactions at the energy domain you are working. I have compared such
results with experimental results and found it to be excellent.

Hope it helps!

Cheers
Sunil


On Fri, Nov 28, 2014 at 4:38 PM, Roxana-georgiana Rata U1179323 <
Roxana.Rata_at_hud.ac.uk> wrote:

>
> Dear FLUKA experts,
>
> I have to simulate a 250 MeV carbon beam hitting a stainless steel pipe
> and to measure the neutron dose equivalent.
> I created my input, my simulation is running perfectly but it seems that
> the neutron dose is to low. In theory I should obtain 29 uSv/h for 1% beam
> loss (2.5x10^7 ions/s)
> Could you, please, check my input and tell me what I'm doing wrong?
>
> Thank you!
>
> Regards,
>
> Roxana
> University of Huddersfield inspiring tomorrow's professionals.
>
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carbon250_26_plot.png
(image/png attachment: carbon250_26_plot.png)

Received on Thu Dec 04 2014 - 07:57:39 CET

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