[FLASH-USERS] Unexpectedly Low Zbar Values Despite High Ion Temperatures - EOS Problem

[Hansen, Eddie]

Hi Owen,

Are the cells where you have unexpectedly low Zbar mixed cells? If there is a significant amount of chamber material, then the Zbar could go below ms_targZMin.

If you send your par file (and setup command), I can look to see if there are maybe any typos or settings that might be causing the issue.

--
Eddie Hansen
Applications Group Leader
Flash Center for Computational Science


From: flash-users <flash-users-bounces at flash.rochester.edu> on behalf of Owen Bardeen <owenbardeen at gmail.com>
Date: Thursday, July 31, 2025 at 4:49 PM
To: flash-users at flash.rochester.edu <flash-users at flash.rochester.edu>
Subject: Re: [FLASH-USERS] Unexpectedly Low Zbar Values Despite High Ion Temperatures - EOS Problem
What's even more off is I have ms_targZmin set to .02 in my .par file. I'm very confused as to why my initial ionization is even lower than this (by about 2 orders of magnitude).

On Wed, Jul 30, 2025 at 1:55 PM Owen Bardeen <owenbardeen at gmail.com<mailto:owenbardeen at gmail.com>> wrote:

Hello all,

I'm encountering an issue with Zbar values in my FLASH simulation and would appreciate any help.

I've set up a LaserSlab simulation with a spherical target. When I check the output files, plotting tion, nion, and average ionization (determined as ye/sumy according to page 587 of the user manual), I see average ionization is orders of magnitude different from what I expect from looking at the EOS tables (checking the Zbar corresponding to the tion and nion I see in my output) I give to FLASH.

I've confirmed that:

  *   The Zbar values in the table are physically reasonable.
  *   Ion temperature and density in the relevant regions match the expected range.
  *   I'm plotting Zbar from the simulation’s checkpoint or plot files, not the raw EOS data.

I’m wondering if this might be due to:

  *   FLASH not reading or using the Zbar in my IONMIX properly?
  *   Something I'm missing with differences in the units?
  *   Weird interpolation of Zbar done by FLASH?

If anyone has experience debugging EOS/Zbar behavior in FLASH, I’d be grateful for any suggestions.

For reference, I am using the LaserSlab module, FLASH4.7.1. My EOS tables are generated using Propaceos software.

Thanks in advance for your help,
Owen
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