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

From: <>
Date: Thu, 13 Nov 2008 11:58:38 +0800

Dear Francesco:

> ii. you misinterpreted the use of the cylindrical mesh of USRBIN. Its axis
> is the z axis (since this is the standard beam axis) and, for each
> longitudinal z-bin, the transverse plane (xy) can be split into radial and
> azimuthal bins. You described correctly the azimuthal angle (going from -180
> to 180 deg, with 0 deg corresponding to the x axis), but that cannot be
> properly used as polar angle with respect to a beam direction parallel to
> the x axis!
I want to score the product neutron angle distribution with respect to
the beam direction, compare with ICRU63.
If I consider single longitudinal z (plane xy), then the azimuthal
angle is the angle distribution of the product neutron with respect to
the beam direction.
Sorry, I had difficulty comprehend this.

> It is correct. I have a couple of remarks about.
> i. you left empty WHAT(4-5) on the first line. This means that default
> values are taken and this way you score neutrons as they are produced in any
> nuclear reaction, neglecting their transport up to the detector. Note that
> if you put instead regions 2 and 3, respectively, defining the target
> surface as scoring surface (thus considering the neutron transport through
> water), the energy interval used as filter will be in fact - not apparently
> - (very) slightly changed due to matching with the group structure applying
> to neutron energies below 20 MeV.
> ii. in order to increase your statistics, you might need to bias the
> interaction probability of primary protons in water (LAM-BIAS card)

In LAM-BIAS card, I'm interested in 16O(p,n) reaction, is it correct that I set
what(4) for proton and what(5) for neutron.
I had a few runs that I need to increase the statistics,
Is there any value that I should take into consideration for biasing
the inelastic hadronic interaction length , like figure of merit(FOM)
in code MCNP or the range of 20MeV in water(1.9mm)

Please advise me.

My Best Regards.


Chenyen Lee
Department of Nuclear Medicine
Chang Gang Memorial Hospital

Received on Thu Nov 13 2008 - 19:35:23 CET

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