[Mesa-users] [External] Re: About changing nuclear reaction rates.

Fri May 27 13:46:19 UTC 2022

Great! Thanks Rob. That makes life easier. Now I have one fewer excuse for still using an old version.

-Zach

From: Rob Farmer<mailto:robert.j.farmer37 at gmail.com>
Sent: Friday, May 27, 2022 9:36 AM
To: Meisel, Zach<mailto:meisel at ohio.edu>
Cc: Francisco De Geronimo<mailto:degeronimofrancisco at gmail.com>; mesa-users<mailto:mesa-users at lists.mesastar.org>
Subject: Re: [External] Re: [Mesa-users] About changing nuclear reaction rates.

So there is a new way to set the rate https://docs.mesastar.org/en/release-r22.05.1/changelog.html#rates<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.mesastar.org%2Fen%2Frelease-r22.05.1%2Fchangelog.html%23rates&data=05%7C01%7Cmeisel%40ohio.edu%7C8d3c37ea3f014a2e607408da3fe5d732%7Cf3308007477c4a70888934611817c55a%7C0%7C0%7C637892553639011026%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=IyWrTNChju738uQljCadsc%2B93RqABVanvZYSXbH3p0I%3D&reserved=0> where we added a hook other_rate_get (https://github.com/MESAHub/mesa/blob/main/star/other/other_rate_get.f90<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FMESAHub%2Fmesa%2Fblob%2Fmain%2Fstar%2Fother%2Fother_rate_get.f90&data=05%7C01%7Cmeisel%40ohio.edu%7C8d3c37ea3f014a2e607408da3fe5d732%7Cf3308007477c4a70888934611817c55a%7C0%7C0%7C637892553639011026%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=BVNVVceNZ8pAtQXIDQ5rYjU0HvyAAfI1%2BjTmZYbNZf0%3D&reserved=0>) that you can use to modify an existing rate (but it will still be interpolated over)

>Also, when you're changing a reaction rate, consider if you need to change the reverse rate as well in order to be physically consistent. You can ignore this step if the reverse rate is tiny, but it may not be small for low Q-value, high-temperature situations.

That is handled automatically now in mesa, if you provide a custom rate table we will compute the reverse rate in detailed balance for you

Rob

On Fri, 27 May 2022 at 14:58, Meisel, Zach <meisel at ohio.edu<mailto:meisel at ohio.edu>> wrote:
Yes, changing the coefficients works, at least up to version 9793. It probably works for later versions too, but I haven’t tried it myself.

Make sure that your inlist is calling the rate coefficient table that you’re editing, e.g. by looking at the output as Rob suggests.

A downside to adjusting the coefficients is that fitting a reaction rate in Reaclib format can be painful. Often you have to decide on what fit residual is good enough and what temperature range you really need to fit, while making sure the rate doesn't blow up at higher and lower temperatures. Note that you can add rate sets, so that you're using more than just one 7 parameter function to represent the rate, but instead a sum of 7-parameter functions.

Also, when you're changing a reaction rate, consider if you need to change the reverse rate as well in order to be physically consistent. You can ignore this step if the reverse rate is tiny, but it may not be small for low Q-value, high-temperature situations.

-Zach

----
Zach Meisel
Associate Professor of Physics & Astronomy
Director, Edwards Accelerator Laboratory
Ohio University
Email: meisel at ohio.edu<mailto:meisel at ohio.edu>
Web: http://inpp.ohio.edu/~meisel

From: Mesa-users <mesa-users-bounces at lists.mesastar.org<mailto:mesa-users-bounces at lists.mesastar.org>> on behalf of Francisco De Geronimo via Mesa-users <mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>>
Sent: Friday, May 27, 2022 8:07:34 AM
To: Rob Farmer <robert.j.farmer37 at gmail.com<mailto:robert.j.farmer37 at gmail.com>>
Cc: mesa-users <mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>>
Subject: [External] Re: [Mesa-users] About changing nuclear reaction rates.

Use caution with links and attachments.
Hi Francis and Rob,
thanks for taking time to reply.
Francis: I was referring to the coefficients of the formula of the rate. If I dont misunderstand, they appear in the
 mesa-r21.12.1/data/rates_data/
folder. My idea was to give the formula directly to MESA.

Rob: Thanks, I will take a look there! I was looking directly to the enuc output 😅

Best regards,

Francisco

El vie, 27 may 2022 a las 7:34, Rob Farmer (<robert.j.farmer37 at gmail.com<mailto:robert.j.farmer37 at gmail.com>>) escribió:
Your custom rate should have been written out into the rates cache folder so you can check to see how mesa interpolated it:

cd $MESA_DIR/rates/test
./show_rates ../../data/rates_data/cache/YOUR_RATE_0.bin > rate.txt

Rob

On Fri, 27 May 2022 at 12:23, Francis Timmes via Mesa-users <mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>> wrote:
hi francisco,

easily from an inlist or a run_star_extras? no.

but mesa is open-source, open-knowledge so one is free
to modify anything one likes. if you dig this deep into
source code, best to make your own copy so as not to disturb
the rest of mesa. somehow though, modifying the coefficients
of a mathematical interpolation formula will need care.

but maybe i'm misunderstanding.
might be useful to show what you are seeing,
and how it leads to coefficients being a culprit.

fxt

> On May 26, 2022, at 12:20 PM, Francisco De Geronimo <degeronimofrancisco at gmail.com<mailto:degeronimofrancisco at gmail.com>> wrote:
>
> Hi Francis,
> thanks for your time.
> As you say, the table could be better.
> Besides that, changing the coefficients is not possible with the current version?
>
> Best regards,
>
> Francisco
>
> El jue, 26 may 2022 a las 15:13, Francis Timmes (<fxt44 at mac.com<mailto:fxt44 at mac.com>>) escribió:
> > not with the adopted rate but with the interpolation of the table.
>
> ... or the number of points defining the rate.
> using ~20 points over 4 orders of magnitude in temperature may lead to such an effect.
> in broad terms, several hundred or thousand temperature points is better.
>
> fxt
>
>
>
> > On May 26, 2022, at 4:46 AM, Francisco De Geronimo via Mesa-users <mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>> wrote:
> >
> > Dear MESA users,
> > I'm trying to change an existing nuclear reaction rate.
> > From the webpage, I found that this could be possible:
> >
> > "change rates for existing reactions
> > create a file of (T8, rate) pairs as in data/rates_data/rates add the file name to reactions.list (you can have a local copy of reactions.list as well as rates directory)".
> >
> > So the way is to provide the table with T8 and the value of the rate.
> > My question is: is it possible to change the reaction rate in my work directory by modifying the coefficients of the function representing it?
> > Im asking this because I noted small bumps in the final Enuc profile, when using the table procedure, that seems to be related not with the adopted rate but with the interpolation of the table.
> >
> > Cheers,
> >
> > Francisco
> > _______________________________________________
> > mesa-users at lists.mesastar.org<mailto:mesa-users at lists.mesastar.org>
> > https://lists.mesastar.org/mailman/listinfo/mesa-users<https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.mesastar.org%2Fmailman%2Flistinfo%2Fmesa-users&data=05%7C01%7Cmeisel%40ohio.edu%7C8d3c37ea3f014a2e607408da3fe5d732%7Cf3308007477c4a70888934611817c55a%7C0%7C0%7C637892553639011026%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=69b5uQz%2Fi7VfDHGjf5%2BR6rdAS2EhsxZWfu%2Bwj4Am0Gg%3D&reserved=0>
> >
>

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