Re: AW: From energy density in GeV/cm3 to rad

From: Anna Ferrari <anna.ferrari_at_lnf.infn.it>
Date: Sun, 16 Jan 2011 18:07:23 +0100 (CET)

Dear Anna,

good that you find the mistake!
Just to clarify a bit more: absorbed dose is the energy deposited by
ionizing radiation per mass unit and 1 Gy of absorbed energy means 1J
deposited in 1 Kg of matter. To have the relation with the deposited
energy per unit volume (usually expressed in the convenient units GeV/cm3)
you have then to multiply by material density remembering to convert
Joules in GeV through the relation you wrote (1 GeV = 1.602 E-10 J)

1Gy (= 1 J/Kg) = E10/1.602 GeV/Kg = (E7/1.602) rho[g/cm3] GeV/cm3

and then as you find in the manual 1.602 E-7/rho is the coefficient to
pass from energy deposition in GeV/cm3 to absorbed energy in Gy.
Remeber also that all the results are per primary weigth.

kind regards,

Anna

PS: the first time in your calculation in rad you forgot a factor E3
coming from Kg->g...

> Dear Anna,
> sorry, I found my mistake.
>
> Best regards
> Anna Kiseleva
>

Dear Anna,
I try to understand the relation between different dimensions. In FLUKA
manual there is:
"Energy deposition will be expressed in GeV per cm3 per unit primary
weight. To obtain doses (in Gy per unit primary weight), the results must
be multiplied by (1.602176462E-7 / rho), where rho is the material density
in g/cm3."
But if I try to go from GeV/cm3 to Gy, I get different coefficient:

1 GeV =3D 1E9 eV = 1.6E-10 J -> 1 J = 1E10/1.6 GeV

1 Gy = 1 J/kg = 1E10/1.6 GeV/kg = 1E10/1.6 GeV/(1E3 g) * cm3/cm3 =
1E7/1.6/rho GeV/cm3

It means, I need to multiply GeV/cm3 by 1E7/1.6/rho in order to have Gy.
Please, correct my, but I don't understand, how this number
1.602176462E-7 / rho was calculate?

Best regards
Anna Kiseleva

>
> -----Ursprüngliche Nachricht-----
> Von: owner-fluka-discuss_at_mi.infn.it im Auftrag von Anna Ferrari
> Gesendet: So 16.01.2011 04:36
> An: Kiseleva, Anna
> Cc: fluka-discuss_at_fluka.org
> Betreff: Re: From energy density in GeV/cm3 to rad
>
>
> Dear Anna,
>
> first of all: in the SI, the International System of Units, the unit for
> the absorbed dose (and not the energy density) is the Gray (Gy) and not
> the rad. The use of the old unit rad ( = 10 mGy) is then discouraged.
>
> Said that, I have the impression that if you express the material density
>
> Kind regards,
>
> Anna
>
>> Dear FLUKA developers,
>>
>> I have questions.
>> I try arithmetically to recalculate energy density in rad:
>> 1 rad = 1e8/1.6022/(material density) GeV/cm3
>> But I got so big numbers if I calculate it for gas (argon). It is right?
>> And how I can compare these numbers with dose in rad?
>>
>> Best regards
>> Anna Kiseleva
>>
>> E-mail: A.Kiseleva_at_gsi.de
>> CBM
>> Gesellschaft fur Schwerionenforschung mbH
>> Planckstrasse 1,