Influence on Neutron spectrum due to energy loss of beam

[andy95220]

Suppose some protons are impacted on a Lithium target to produce neutrons with energies close to the proton energy. If one considers Energy-loss due to proton-target collision (ionization of the target atoms), will this kind of energy loss influence neutron energy spectrum?

I am asked by my professor to calculate the energy loss of a proton beam with kinetic energy of 100MeV in a 28mm thick lithium target. I used Bethe-Bloch Eq to get the energy loss of the proton beam is about 3 MeV. But I have no idea whether this will have any influence on the spectrum of neutron.

I asked my professor today. He said we only need to consider Bethe-Bloch Eq to get the answer...Does anyone have any suggestion?

 

[Astronuc]

What determines the energy of a neutron produced from a (p,n) reaction with ⁶Li or ⁷Li?

Should there be a difference in neutron energy from a (p,n) reaction with a 97 MeV proton vs a 100 MeV proton?

Also, think of what the Bethe-Bloch equation represents. Are there other energy loss/transfer mechanisms?

 

[andy95220]

What determines the energy of a neutron produced from a (p,n) reaction with ⁶Li or ⁷Li?

Should there be a difference in neutron energy from a (p,n) reaction with a 97 MeV proton vs a 100 MeV proton?

Also, think of what the Bethe-Bloch equation represents. Are there other energy loss/transfer mechanisms?

I guess there is no influence on the neutron energy spectrum since the neutron is not charged...is this reasonable?

 

[Astronuc]

I guess there is no influence on the neutron energy spectrum since the neutron is not charged...is this reasonable?

What neutron energy would one expect from a (p,n) reaction with ⁶Li and ⁷Li?

 

[andy95220]

What neutron energy would one expect from a (p,n) reaction with ⁶Li and ⁷Li?

One should expect the neutrons to have same energy of the protons. I don’t know much about nuclear reactions. Could you please explain more?

 

[Astronuc]

One should expect the neutrons to have same energy of the protons. I don’t know much about nuclear reactions. Could you please explain more?

So, it appears that one has not done nuclear reactions yet. Therefore the emphasis on the question in the original power is the effect of slowing down protons and the consequence of the expected neutron energy. Getting back to that, what would one expect as the consequence of less energetic protons?

With respect to nuclear reactions, one has to consider the difference in masses of the incident particle (proton in this case) and target nucleus, and the masses of the resulting nucleus and neutron. One needs to determine the change in mass by taking the difference of the masses before the reaction and those after. If the change in mass is positive, the reaction is exoergic, i.e., there is excess energy available to the products. If the mass difference is negative, the reaction is endoergic, and there will need to be some energy input (e.g., kinetic energy) to make the reaction happen.
http://230nsc1.phy-astr.gsu.edu/hbase/Nuclear/nucrea.html

 

[andy95220]

So, it appears that one has not done nuclear reactions yet. Therefore the emphasis on the question in the original power is the effect of slowing down protons and the consequence of the expected neutron energy. Getting back to that, what would one expect as the consequence of less energetic protons?

With respect to nuclear reactions, one has to consider the difference in masses of the incident particle (proton in this case) and target nucleus, and the masses of the resulting nucleus and neutron. One needs to determine the change in mass by taking the difference of the masses before the reaction and those after. If the change in mass is positive, the reaction is exoergic, i.e., there is excess energy available to the products. If the mass difference is negative, the reaction is endoergic, and there will need to be some energy input (e.g., kinetic energy) to make the reaction happen.
http://230nsc1.phy-astr.gsu.edu/hbase/Nuclear/nucrea.html

Thank you for your comments! Yes you are right! But I don’t know what’s the consequences of less energetic protons, could you please give me more hints?

 

[Astronuc]

But I don’t know what’s the consequences of less energetic protons, could you please give me more hints?

What does one know about conservation of energy in nuclear reactions?

What textbook is one using?

 

[mfb]

You are almost there. You know the neutron energy from a 100 MeV proton (assuming you followed the previous hints). What will the neutron energy from a 97 MeV proton be compared to the previous case?