[fluka-discuss]: RE: Aluminum shield causes no attenuation

From: Philippe Schoofs <philippe.schoofs_at_cern.ch>
Date: Thu, 7 Jul 2016 07:14:02 +0000

HI Roman,

You can find the inelastic scattering length of your beam particles in the different materials in the output file. If you look for the "Inelastic" string of characters, you should see it ;)

Cheers
Philippe

From: owner-fluka-discuss_at_mi.infn.it [mailto:owner-fluka-discuss_at_mi.infn.it] On Behalf Of Roman Savinov
Sent: 07 July 2016 03:10
To: Vasilis Vlachoudis <Vasilis.Vlachoudis_at_cern.ch>; fluka-discuss_at_fluka.org
Subject: [fluka-discuss]: Re: Aluminum shield causes no attenuation


Hi Vasilis,



Can you please explain how to calculate the inelastic scattering length of a proton in material? How did you get 34.5 cm?



thank you,



Roman

________________________________
From: Vasilis Vlachoudis <Vasilis.Vlachoudis_at_cern.ch<mailto:Vasilis.Vlachoudis_at_cern.ch>>
Sent: Tuesday, June 28, 2016 8:08:32 AM
To: Roman Savinov; fluka-discuss_at_fluka.org<mailto:fluka-discuss_at_fluka.org>
Subject: RE: Aluminum shield causes no attenuation

Hi Roman,

the inelastic scattering length of a proton _at_ 1GeV on Al is 34.5cm, so you are still building
up the cascade and you have not reached the maximum yet, so you should expect
that the dose on the shield to go up as well in the water.
Just two other notes:
1. USRBIN by region doesn't return GeV/cm3 put integrated over the volume. You have
   to manually divide by the volume, which you claim in your formula as the second term
   however I don't see it on the excel file
2. You don't have a hemisphere but rather a quarter of a sphere in your geometry.

Cheers
Vasilis

________________________________
From: owner-fluka-discuss_at_mi.infn.it<mailto:owner-fluka-discuss_at_mi.infn.it> [owner-fluka-discuss_at_mi.infn.it] on behalf of Roman Savinov [rsavinov_at_calpoly.edu]
Sent: Tuesday, June 28, 2016 08:22
To: fluka-discuss_at_fluka.org<mailto:fluka-discuss_at_fluka.org>
Subject: [fluka-discuss]: Aluminum shield causes no attenuation

Dear FLUKA experts,



I have a hemisphere of water shielded by a layer of aluminum subject to GCR:

[cid:image001.png_at_01D1D82F.E69B1240]



I'm measuring the rate of dose absorption by water for 10 shielding thicknesses: from 10 to 50 g/cm2.

I expect to see a decreasing trend with increasing thickness but what I'm getting instead is a trend which is somewhat level:

[cid:image002.png_at_01D1D82F.E69B1240]

While, the absorption rate of the shield increases with thickness:

[cid:image003.png_at_01D1D82F.E69B1240]



Why doesn't water absorb less radiation as shielding layer getting thicker? Is it because 18.5 cm (50 g/cm2) of aluminum is as useless to shield from GCR as 3.7 cm (10 g/cm2)?



The inputs are as follows:

Source: GCR-IONF (protons - Carbon ions), GCR-SPE set to NO-NORM, the number of primary histories: 3e5

Target: hemisphere of water covered by layer of aluminum

Detector: USRBIN (by region, DOSE)



The conversion from USRBIN output to uGy/day is as follows:

[cid:image004.png_at_01D1D82F.E69B1240]

where the second term is division by target's volume; [pr/s] is found by: Fluxst/flux (these two values are from the .out file)

I attached my input file



Any help would be greatly appreciated,



Roman




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Received on Thu Jul 07 2016 - 11:19:40 CEST