Re: Score neutron from 16O(p,xn) reaction

From: Francesco Cerutti <>
Date: Wed, 3 Dec 2008 13:24:28 +0100

Dear Lee,

since you are interested in neutron production, you need a good statistics=
for nuclear reactions undergone by beam protons. They travel 4mm in water,=
whereas their inelastic scattering length is more than 50cm. This means=20
that most of them, as you said, stop before interacting through inelastic=
reactions (-> no neutron production). Thus you need to bias, i.e.=20
artificially reduce the inelastic scattering length.
For long range (high energy) particles, a criterion is comparing the=20
inelastic scattering length and the geometry size (what I wrote=20
previously). In my last message, I wanted to point out that indeed this=20
is not your case, since the range is less than the target length, thus the=
latter is not relevant for the choice of the biasing factor. Sorry for the=
confusion this caused to you.



On Wed, 3 Dec 2008, =A7=F5=A8=B0=ADl wrote:

> Dear Francesco:
>> Since the 20MeV proton range in water (around 4mm) is less than your tar=
>> length, the latter is indeed not relevant to the choice of the biasing
>> factor for the inelastic scattering length.
>> The reduction factor in WHAT(2) has to be set comparing the inelastic sc=
attering length of beam protons in > water (printed in the .out file) and t=
he lenght of your target (after one scattering length - assuming it as > =
constant along the energy range of interest - about 63% of the beam particl=
es underwent an inelastic > reaction).
> Sorry, I may misinterpret the message from your reply
> Please let me state what I I understand and correct me.
> The inelastic cross section ( around 4.4 m barns for (p,n)) is very
> small compare to electronic interaction.
> Most of the proton didn't undergo inelastic scattering, but electronic
> interaction.
> From the output , the inelastic scattering length of water is 56cm.
> So if want to increase the interaction probability of inelastic
> scattering, I set the biasing factor for inelastic interaction like
> 0.01, the inelastic scattering length became 0.56cm.
> In the other way ,
> I knew the 20MeV proton range in water (around 4mm) is less than target.
> It seems to me that biasing is not so necessary.
> The two confuses me.
> Lee

Francesco Cerutti
CH-1211 Geneva 23
tel. ++41 22 7678962
fax ++41 22 7668854
Received on Wed Dec 03 2008 - 15:49:08 CET

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