[Mesa-users] Ni Mixing

[Bill Paxton]

> On Jan 28, 2019, at 1:26 PM, Wilson Ricks via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> Hello,
> 
> How exactly does MESA add/mix Ni56 in the "example_ccsn_IIp" inlist? "inlist_shock_part6" seems to suggest that Ni56 is added to scale with the O16 distribution somehow, but I have not been able to find more information in the files.
> 
> Thanks,
> Wilson

the code that actually does the work is in run_star_extras, subroutine set_nico_mass.

(it is in with a lot of ugly left-over code that i should have discarded long ago.  apologies for that junk.)

these controls are given in the inlist

x_ctrl(12) - new Ni mass in Msun
x_ctrl(35) - min mass for Ni in Msun, as offset above inner boundary of model
x_ctrl(36) - max mass for Ni in Msun, as offset above He_core_mass
x_ctrl(37) - min velocity that will be included in model for Stella; this can lead to revision of min mass for Ni
	so that the requested amount of Ni will be in the model for Stella.

if the max mass for Ni is specified as < 0, then the rescaling is done for the entire model.  this is the typical case, so i’ll outline that.  for the other case, take a look at the code.

1st step is to replace Co56 by Ni56, in effect ignoring Ni56 decay before breakout.  this rather dubious action seems to be consistent with the use of “ni mass created in explosion” in the literature.  

it then adds up the old amount of ni to get the ratio of new to old.

using that ratio, all cells have their ni mass fraction scaled by that fraction, and the oxygen mass fraction changed accordingly to keep the sum of mass fractions equal to 1.

hope that helps,
bill








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