[Mesa-users] Problem with r12778. Bug?

[Bill Paxton]

> On May 12, 2020, at 7:34 PM, Ian Foley via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> Hi Josiah, and Biil,
> 
> Applied your suggested mod and it works beautifully. I can now use gold tolerances and get good performance
> and better results too.

and we found a bug (soon to be fixed).  so it’s a win-win.  ;-)

bill



> 
> Thanks!
> Ian
> 
> 
> 
> On Wed, 13 May 2020 at 10:20, Josiah Schwab <jwschwab at ucsc.edu <mailto:jwschwab at ucsc.edu>> wrote:
> Hi Ian,
>  
> you have found a good work around for the problem until the next release when this bug will be fixed.
> as you noticed, the treatment in basic.net <http://basic.net/> avoids the problem, so it is only larger nets that will hit it when dealing with low temperatures.
> 
> To add a bit more, we noticed the rate chosen for li7 burning with a "soft" net (where your net file only specifies isotopes) isn't behaving correctly at low T.  (You might notice when you look closely the li7 profile looks "funny" in your model.)  Nets like pp_and_cno_extras.net <http://pp_and_cno_extras.net/> use a different rate, which is probably why this had gone unnoticed.
> 
> As a workaround, you can swap out the rate for a better behaved version.  Aaron Dotter suggested doing
> 
> remove_reaction(r_h1_li7_to_he4_he4)
> add_reaction(r_li7_pa_he4)
> 
> and when I added these lines to ian30r.net <http://ian30r.net/> (after the add_isos_and_reactions part) I no longer saw the issue.
> 
> I think the spikes in eps_nuc were associated with zones reaching logT > 7 and then having their li7 suddenly burn.  (Physically it should have burned at lower T).
> 
> Thanks for the bug report!
> 
> Josiah 
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