Discussion Overview
The discussion revolves around the relationship between nuclear reaction rates and cross sections, specifically exploring the threshold of cross sections necessary to achieve a near 100% reaction rate. Participants examine the implications of different cross section values and the factors influencing reaction probabilities.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant notes the significance of cross sections in determining the likelihood of nuclear reactions and speculates that a cross section of 100Kb or higher might be necessary for a near 100% reaction rate.
- Another participant argues that there is no direct relationship between cross section and reaction rate, questioning the meaning of "100%" in this context and suggesting that cross section ratios may be more relevant.
- A participant provides examples of very small cross sections, such as those associated with Higgs production and dark matter, indicating that even small values can be common in certain reactions.
- One participant mentions a specific reaction (7Li(p,n)7Be) with a cross section of 590 mb, suggesting that a cross section of 100,000 b would lead to all bombarding protons being consumed in the reaction.
- Another participant asserts that while a reaction rate can approach 1, it can never reach 100% due to competing processes with their own cross sections.
- A participant inquires about the possibility of manually increasing specific cross sections, expressing disappointment with the small values typically found in data tables.
- One participant cites positron annihilation as an example of a reaction with a fraction very close to 1, while questioning the commonality of positron capture reactions.
- Another participant responds that cross sections cannot be changed and discusses the energy dependence of positron capture probabilities.
Areas of Agreement / Disagreement
Participants express differing views on the relationship between cross sections and reaction rates, with some asserting that 100% reaction rates are unattainable while others speculate on the necessary conditions. The discussion remains unresolved regarding the exact implications of cross section values and the feasibility of achieving high reaction rates.
Contextual Notes
Participants highlight the complexity of nuclear reactions, noting that competing processes and energy levels significantly influence cross sections and reaction probabilities. The discussion reflects a range of assumptions and interpretations regarding the definitions and implications of cross sections.