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

From: Roxana-georgiana Rata U1179323 <Roxana.Rata_at_hud.ac.uk>
Date: Thu, 4 Dec 2014 14:08:09 +0000

Dear Sunil,

Thank you for your help. Indeed, at this stage I am interested to obtain the prompt neutron dose, to see if we need a roof above the machine.
Right now, I am running the simulations as you suggested me.
Thank you for you useful advices.
I have another questions. I will have to make the same scenario, but for other ions like O, Ne, He, Ar, Xe. DOSEEQ can be used for heavy ions?
Because in the manual I found that :
Dose conversion coefficients exist only for some particle types: hadrons, muons, photons, electrons/positrons. For all other particle types, zero factor will be returned. This is particularly
 important for heavy ions where zero factor will be scored

Regards,

Roxana
________________________________
From: Sunil C [csunil11_at_gmail.com]
Sent: Thursday, December 04, 2014 5:16 AM
To: Roxana-georgiana Rata U1179323
Cc: fluka-discuss_at_fluka.org
Subject: Re: [fluka-discuss]: heavy ion dose scoring

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<mailto: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
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Received on Thu Dec 04 2014 - 16:27:25 CET

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