- #106
Astronuc
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2023 Award
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Well, yes, that is a reaction of interest for producing neutrons.cmb said:There are different means to create the neutrons for BNCT. Here is a company doing (p,n);
http://www.neutrontherapeutics.com/technology/
In fact, "Between 1.9– and 2.4–MeV bombarding energy, the neutrons are monoenergetic and the reaction cross section is large. Therefore the Li(p,n)Be reaction has long been used as a source of neutrons (n) at these energies [5]." Ref: https://mcnp.lanl.gov/pdf_files/la-ur-00-1067.pdf
Ref [5] from the report is J. H. GIBBONS and H.W. NEWSON, “The Li(p,n)Be Reaction,” Fast Neutron Physics, Vol.1, J. B. MARION and J. L. FOWLER, Eds., Interscience, New York (1960).
We usually refer to spallation reactions for (p,n) reactions, as opposed to fusion, but some use the term fusion. I'm not sure at what time frame is used to distinguish spallation from fusion.
When I check one of my texts on fusion for p+Li reactions, I find two 'fusion' reactions:
p + 6Li -> 3He + 4He + 4.0 MeV
p + 7Li -> 2 4He + 17.5 MeV
Theoretically, the p + 7Li would form an intermediate state 8Be, but 8Be is unstable and short-lived (half-life 8.19𝑥10−17seconds, so the state is not even considered in the evaluation of the process.
https://www.osti.gov/servlets/purl/1773479
Similarly for 5He in d+t fusion, the half-life is estimated to be 7.595×10-22 seconds. https://education.jlab.org/itselemental/iso002.html
http://atlas.physics.arizona.edu/~s...17/LectureSupplements/HeliumIsotopes_Wiki.pdf
In the case of p + 7Li -> 7Be + n, the product 7Be has a half-life of ~ 53.2 d and decays by electron capture back to 7Li, which is stable.
To be useful as a source of practical energy, the average temperature of the reactants should be as low as possible, in the keV range, as opposed to the MeV range. Note, for a nucleus or subatomic particle, 1 eV ~ 11605 K, so 1 keV ~11605000 K.
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