Differential cross-section and scattering.

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Homework Help Overview

The discussion revolves around a problem involving the absorption of neutrons by a cadmium foil, specifically focusing on the calculation of the fraction of neutrons absorbed. The context includes concepts from nuclear physics and scattering theory.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are attempting to determine whether to treat the problem as involving thick or thin foil. There are questions about the relevance of the neutron's kinetic energy in the calculations and the definitions of variables used in the formulas.

Discussion Status

Some participants have provided links to resources and attempted calculations based on the formulas found there. However, there is a lack of clarity regarding certain variables and their meanings, leading to confusion about the role of the neutron's energy in the problem. Multiple interpretations of the problem setup are being explored.

Contextual Notes

There is uncertainty regarding the definitions of variables such as n (number density) and A (area of the foil), as well as the significance of the neutron energy provided in the problem statement. Participants are encouraged to clarify these terms to facilitate better understanding.

hhhmortal
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Homework Statement



A beam of 0.38 MeV neutrons is incident on a 113Cd foil of thickness 1mm. The absorption
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cross-section for 0.38 MeV neutrons is 5 barns. What is the fraction of neutrons absorbed by the foil?


The Attempt at a Solution



I'm not sure whether I should treat this as scattering in a thick or thin foil and how the energy of the incoming particles is related to the total scattering of particles.


Thanks.
 
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hhhmortal said:
Hi! I tried using the formulae given in that webpage. Problem is I don't know where the kinetic energy of the neutron (0.38 MeV) comes in into that equation. Anyhow I still get the wrong answer..

Just post your calculation. People will help you.
 
For scattering in a thin foil:

R = F σ n A dx

We have to find R/F and then to get fraction of neutrons absorbed by foil (1 - R/F)

We know what σ, n and dx are, but not A. I don't know why they give me the energy value of the neutrons...?
 
Please write what is n, A , etc..because many people use their own convention so better to write the key. Is A the mass number of target. ?
Did you miss anything in your question?
Okay i just made a simple calculation using the formula found in that website..
is your solution, i.e the fraction of neutron beam scattered is 0.023? (1-0.23)=0.977.
In fact i am sorry i also don't know why they have given the energy of beam.
 
Rajini said:
Please write what is n, A , etc..because many people use their own convention so better to write the key. Is A the mass number of target. ?
Did you miss anything in your question?
Okay i just made a simple calculation using the formula found in that website..
is your solution, i.e the fraction of neutron beam scattered is 0.023? (1-0.23)=0.977.
In fact i am sorry i also don't know why they have given the energy of beam.

Sorry forgot about that.

F = flux incident on target. (particles per m² per sec)

A = Total area of foil

n = number density of target atoms
σ = scattering cross section
dx = thickness of foil

Im having the exact same problem, I still can't figure it out.


Thanks.
 

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