I am playing with your open source code NucNet Projects (simple_snII) like what you have done in PHYSICAL REVIEW C 89, 025807 (2014).
I have a question when I change the reaction rate using the XPath expressions.
It seems that the reaction rates (and thus the calculated abundances) are not changed when I select the reactions with the expression [reactant = 'gamma' and product = 'n'] and multiply the rate by a factor of e.g. 10.
However, the reaction rates (and thus the abundances) do change when I select the reactions with the expression [reactant = 'n' and product = 'gamma'] and multiply the rate by a factor of e.g. 10.
The same effect is observed for 'p' and 'alpha' induced reactions.
Can you tell me why this happens?
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Thanks for your post. The code computes reverse reactions from forward reactions by detailed balance; thus, for example, it will compute the fe57(gamma,n)fe56 reaction rate from the fe56(n,gamma)57fe reaction rate. This ensures that the abundances will go into the correct equilibrium.
The input data typically has only the forward (exothermic) reaction rate data, and the XPath selects on those data. In the above example, since only the fe56(n,gamma)fe57 data are present, selecting on reactant = 'gamma' and product = 'n' wouldn't find fe57(gamma,n)fe56.
When one modifies a reaction rate, one should also modify the reverse reaction rate since the equilibrium will not change. Thus, when the code increases the fe56(n,gamma)fe57 rate by a factor of 10, it will also increase the fe57(gamma,n)fe56 rate by a factor of 10 (detailed balance). If one wants to change the (gamma,n) rate by a different factor, one must use an NSE correction factor. Here you are effectively changing the Q value of the reaction.
In short, use an XPath to select the forward (exothermic) reaction. The reverse reaction will then automatically change appropriately. I hope that helps. Best wishes.
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Thanks a lot for your detailed explanation.
It is clear for me now. If I understand correctly, your explanation also works for other reactions e.g., (alpha,n), (alpha,p) and (n,p).
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Yes. If you choose the XPath expression [reactant = 'he4' and product = 'n'], the code will select (a,n) reactions from the input data. If you modify the rates for those reactions, you will change them and their reverse (n,a) reactions. By choosing that XPath, however, you won't select out any reactions that are in the data as (n,a) reactions. To select all (a,n) and (n,a) from the input data, use the XPath expression "[(reactant = 'he4' and product = 'n') or (reactant = 'n' and product = 'he4')]".
You can always test by printing the reactions with the print_reactions libnucnet example codes. Best wishes.
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I am playing with your open source code NucNet Projects (simple_snII) like what you have done in PHYSICAL REVIEW C 89, 025807 (2014).
I have a question when I change the reaction rate using the XPath expressions.
It seems that the reaction rates (and thus the calculated abundances) are not changed when I select the reactions with the expression [reactant = 'gamma' and product = 'n'] and multiply the rate by a factor of e.g. 10.
However, the reaction rates (and thus the abundances) do change when I select the reactions with the expression [reactant = 'n' and product = 'gamma'] and multiply the rate by a factor of e.g. 10.
The same effect is observed for 'p' and 'alpha' induced reactions.
Can you tell me why this happens?
Thanks for your post. The code computes reverse reactions from forward reactions by detailed balance; thus, for example, it will compute the fe57(gamma,n)fe56 reaction rate from the fe56(n,gamma)57fe reaction rate. This ensures that the abundances will go into the correct equilibrium.
The input data typically has only the forward (exothermic) reaction rate data, and the XPath selects on those data. In the above example, since only the fe56(n,gamma)fe57 data are present, selecting on reactant = 'gamma' and product = 'n' wouldn't find fe57(gamma,n)fe56.
When one modifies a reaction rate, one should also modify the reverse reaction rate since the equilibrium will not change. Thus, when the code increases the fe56(n,gamma)fe57 rate by a factor of 10, it will also increase the fe57(gamma,n)fe56 rate by a factor of 10 (detailed balance). If one wants to change the (gamma,n) rate by a different factor, one must use an NSE correction factor. Here you are effectively changing the Q value of the reaction.
In short, use an XPath to select the forward (exothermic) reaction. The reverse reaction will then automatically change appropriately. I hope that helps. Best wishes.
View and moderate all "Getting Help with Nucnet Tools" comments posted by this user
Mark all as spam, and block user from posting to "Discussion"
Thanks a lot for your detailed explanation.
It is clear for me now. If I understand correctly, your explanation also works for other reactions e.g., (alpha,n), (alpha,p) and (n,p).
Yes. If you choose the XPath expression [reactant = 'he4' and product = 'n'], the code will select (a,n) reactions from the input data. If you modify the rates for those reactions, you will change them and their reverse (n,a) reactions. By choosing that XPath, however, you won't select out any reactions that are in the data as (n,a) reactions. To select all (a,n) and (n,a) from the input data, use the XPath expression "[(reactant = 'he4' and product = 'n') or (reactant = 'n' and product = 'he4')]".
You can always test by printing the reactions with the print_reactions libnucnet example codes. Best wishes.