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Dear FLUKA-ites,
I'm glad I found this, I was having a similar issue with the 2.22 MeV =
gammas from neutron capture on hydrogen.
Does anyone know why the RESNUCLEI rate of 2H production is ~150x higher =
with NEW-DEFA than with PRECISIO? When I run with PRECISIO, I find that =
the 2.2 MeV gamma production (found from USDRAW as suggested) nearly =
matches the RESNUCLEI rates for 2H. What could cause such a large =
discrepancy?
I will certainly use PRECISIO from now on, but I'd like to know why.
I was also somewhat concerned about using MGDRAW for this, as =
documentation =
(
http://www.fluka.org/web_archive/earchive/prova/att-0814/UserRoutines.pdf=
) strongly recommends against using MGDRAW whenever low energy neutrons =
are involved. Should I be concerned about this?
Cheers!
Josh
On Jan 24, 2013, at 2:17 AM, Anton Lechner <Anton.Lechner_at_cern.ch> =
wrote:
> 2013 11:17:17 +0100 (CET)
> X-Virus-Scanned: clamav-milter 0.97.6 at smtp1.mi.infn.it
> X-Virus-Status: Clean
> Sender: owner-fluka-discuss_at_smtp2.mi.infn.it
>=20
> Dear,
>=20
> First of all, do not use NEW-DEFA as DEFAULTS setting but PRECISIO.=20
>=20
> Note that photons (with energy ~0.002223 MeV) produced in =
1-H(n,gamma)2-H interactions may still interact within your target, and =
therefore your USRBDX scoring of photons leaving the target is not the =
most suitable way to exactly count such neutron interactions. If you are =
interested to count individual photons produced in 1-H(n,gamma)2-H, I =
would rather use the MGDRAW routine, in particular the USDRAW entry. If =
activated via the USERDUMP card (see manual), USDRAW is called after =
physical interactions; secondaries like photons will then be available =
in the GENSTK common. The ICODE value for your neutron interaction is =
300. One can then for example loop over stack entries to retrieve =
particle type, energy and weight, e.g.:
> DO 10 INP =3D 1, NP
> WRITE(50,*) 'Particle=3D',KPART(INP),' Energy=3D',TKI(INP),=20=
> & ' Weight=3D',WEI(INP) =20
> 10 CONTINUE
> In other words, if a 1-H(n,gamma)2-H interaction occurs you will =
obtain a ~0.002223 MeV photon on the stack after such a neutron capture.
> You may find more information about MGDRAW (and USDRAW in particular) =
in the "Programming User Routines" lecture of the last advanced FLUKA =
course (TRIUMF2012).
>=20
> Concerning the scoring of residual nuclei, your approach is the =
correct one, i.e. you will get the number of 2-H directly in the =
RESNUCLE output (obviously per primary). One important point is the =
following (thanks to Francesco for reminding me this): the residuals =
from low-energy neutron interactions, such as the considered =
1-H(n,gamma)2-H, are only created for scoring purposes if one issues the =
RESNUCLE card. This means, no information about the residuals is =
available in USDRAW.
>=20
> Just as a general comment, I would like to remind you that many of =
your neutrons will just undergo elastic interactions in the target and =
eventually leave the target without being captured (at these neutron =
energies the capture cross section of 1-H being about two orders of =
magnitude smaller than the cross section for elastic scattering). You =
can account for neutrons leaving your target in the BXDRAW entry of =
MGDRAW.
>=20
> Cheers, Anton
>=20
>=20
>=20
> ________________________________________
> From: owner-fluka-discuss_at_mi.infn.it [owner-fluka-discuss_at_mi.infn.it] =
on behalf of ssghodke_at_barc.gov.in [ssghodke_at_barc.gov.in]
> Sent: 14 December 2012 13:24
> To: fluka-discuss_at_fluka.org
> Subject: thermal neutron capture in Hydrogen
>=20
> Dear fluka experts
> We are trying to find out the reaction rate of the thermal neutron =
capture
> reaction 1H(n,gamma)2D. We have taken a cylinder (rad =3D 1.784cm, H =3D=
10cm)
> filled with hydrogen at a density 1g/cm3. We have used the following
> tallies (by taking all the integral values, surface=3D1, volume=3D1):
> 1) The USRTRACK to find out the integral thermal neutron fluence =
(Phi) in
> the volume of the cylinder. This output is used to calculate reaction =
rate
> (N*sigma*Phi) by taking sigma =3D 0.33 barns. (of course we got =
N*sigma*Phi=3D
> 0.08696)
> 2) The RESNUCLEI to find out the production of 2D.
> 3) The USRBDX to find the out the number of capture gammas =
(2.2MeV)
> crossing the cylinder.
> But none of these three values match with each other. We are attaching =
the
> input and output files. Please suggest any correction in the input =
file.
>=20
>=20
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charset=us-ascii
<html><head><meta http-equiv=3D"Content-Type" content=3D"text/html =
charset=3Dus-ascii"></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; =
"><div>Dear FLUKA-ites,</div><div><br></div>I'm glad I found this, I was =
having a similar issue with the 2.22 MeV gammas from neutron capture on =
hydrogen.<div><br></div><div>Does anyone know why the RESNUCLEI rate of =
2H production is ~150x higher with NEW-DEFA than with PRECISIO? =
When I run with PRECISIO, I find that the 2.2 MeV gamma production =
(found from USDRAW as suggested) nearly matches the RESNUCLEI rates for =
2H. What could cause such a large =
discrepancy?</div><div><br></div><div>I will certainly use PRECISIO from =
now on, but I'd like to know why.</div><div><br></div><div>I was also =
somewhat concerned about using MGDRAW for this, as documentation (<a =
href=3D"
http://www.fluka.org/web_archive/earchive/prova/att-0814/UserRouti=
nes.pdf">
http://www.fluka.org/web_archive/earchive/prova/att-0814/UserRout=
ines.pdf</a>) strongly recommends against using MGDRAW whenever low =
energy neutrons are involved. Should I be concerned about =
this?</div><div><br></div><div>Cheers!</div><div><br></div><div>Josh</div>=
<div><br><div><div>On Jan 24, 2013, at 2:17 AM, Anton Lechner <<a =
href=3D"mailto:Anton.Lechner_at_cern.ch">Anton.Lechner_at_cern.ch</a>> =
wrote:</div><br class=3D"Apple-interchange-newline"><blockquote =
type=3D"cite">2013 11:17:17 +0100 (CET)<br>X-Virus-Scanned: =
clamav-milter 0.97.6 at <a =
href=3D"
http://smtp1.mi.infn.it">smtp1.mi.infn.it</a><br>X-Virus-Status: =
Clean<br>Sender: <a =
href=3D"mailto:owner-fluka-discuss_at_smtp2.mi.infn.it">owner-fluka-discuss_at_s=
mtp2.mi.infn.it</a><br><br>Dear,<br><br>First of all, do not use =
NEW-DEFA as DEFAULTS setting but PRECISIO. <br><br>Note that photons =
(with energy ~0.002223 MeV) produced in 1-H(n,gamma)2-H interactions may =
still interact within your target, and therefore your USRBDX scoring of =
photons leaving the target is not the most suitable way to exactly count =
such neutron interactions. If you are interested to count individual =
photons produced in 1-H(n,gamma)2-H, I would rather use the MGDRAW =
routine, in particular the USDRAW entry. If activated via the USERDUMP =
card (see manual), USDRAW is called after physical interactions; =
secondaries like photons will then be available in the GENSTK common. =
The ICODE value for your neutron interaction is 300. One can then for =
example loop over stack entries to retrieve particle type, energy and =
weight, e.g.:<br> DO 10 INP =3D 1, =
NP<br> =
WRITE(50,*) =
'Particle=3D',KPART(INP),' Energy=3D',TKI(INP), <br> =
& =
&n=
bsp; ' Weight=3D',WEI(INP) <br> 10 =
CONTINUE<br>In other words, if a 1-H(n,gamma)2-H interaction =
occurs you will obtain a ~0.002223 MeV photon on the stack after such a =
neutron capture.<br>You may find more information about MGDRAW (and =
USDRAW in particular) in the "Programming User Routines" lecture of the =
last advanced FLUKA course (TRIUMF2012).<br><br>Concerning the scoring =
of residual nuclei, your approach is the correct one, i.e. you will get =
the number of 2-H directly in the RESNUCLE output (obviously per =
primary). One important point is the following (thanks to Francesco for =
reminding me this): the residuals from low-energy neutron interactions, =
such as the considered 1-H(n,gamma)2-H, are only created for scoring =
purposes if one issues the RESNUCLE card. This means, no information =
about the residuals is available in USDRAW.<br><br>Just as a general =
comment, I would like to remind you that many of your neutrons will just =
undergo elastic interactions in the target and eventually leave the =
target without being captured (at these neutron energies the capture =
cross section of 1-H being about two orders of magnitude smaller than =
the cross section for elastic scattering). You can account for neutrons =
leaving your target in the BXDRAW entry of MGDRAW.<br><br>Cheers, =
Anton<br><br><br><br>________________________________________<br>From: =
<a =
href=3D"mailto:owner-fluka-discuss_at_mi.infn.it">owner-fluka-discuss_at_mi.infn=
.it</a> [<a =
href=3D"mailto:owner-fluka-discuss_at_mi.infn.it">owner-fluka-discuss_at_mi.infn=
.it</a>] on behalf of <a =
href=3D"mailto:ssghodke_at_barc.gov.in">ssghodke_at_barc.gov.in</a> [<a =
href=3D"mailto:ssghodke_at_barc.gov.in">ssghodke_at_barc.gov.in</a>]<br>Sent: =
14 December 2012 13:24<br>To: <a =
href=3D"mailto:fluka-discuss_at_fluka.org">fluka-discuss_at_fluka.org</a><br>Sub=
ject: thermal neutron capture in Hydrogen<br><br>Dear fluka =
experts<br>We are trying to find out the reaction rate of the thermal =
neutron capture<br>reaction 1H(n,gamma)2D. We have taken a cylinder (rad =
=3D 1.784cm, H =3D 10cm)<br>filled with hydrogen at a density 1g/cm3. We =
have used the following<br>tallies (by taking all the integral values, =
surface=3D1, volume=3D1):<br>1) The =
USRTRACK to find out the integral thermal neutron fluence (Phi) =
in<br>the volume of the cylinder. This output is used to calculate =
reaction rate<br>(N*sigma*Phi) by taking sigma =3D 0.33 barns. (of =
course we got N*sigma*Phi=3D<br>0.08696)<br>2) =
The RESNUCLEI to find out the production =
of 2D.<br>3) The USRBDX to find the out =
the number of capture gammas (2.2MeV)<br>crossing the cylinder.<br>But =
none of these three values match with each other. We are attaching =
the<br>input and output files. Please suggest any correction in the =
input file.<br><br><br></blockquote></div><br></div></body></html>=
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Received on Wed Apr 10 2013 - 09:45:52 CEST