The elemental opacities are calculated on a uniform grid of temperatures,
electron degeneracy paramaters and dimensionless photon energies u,
where u is defined as:
u Grids used on the Web Page
The opacities are calculated on a grid of 14,900 u points for each
temperature point. Because of run time and storage limitations,
this grid was thinned to 3900 points in the data files before they were
placed on the Web Page. With the recent upgrade to the server running the
Web Page, it was decided to place both the thinned and full data files on
the disk and let the user choose which one to use. The default is still
the thinned grid. Both grids are shown below:
Accessing the Dense u Grid
It is recommended that users do not routinely use the dense u grid,
especially if only interested in Rosseland "gray" opacities or the average
ionization of the plasma. The run times will increase by a factor of
5, with only a few percent change in the Rosseland "gray" opacity
and no change in the average ionization. Users must also keep in
mind that the denser tables are no more
spectroscopically resolved
than the normal grid, they just show more detail. The tables that will
benefit the most from the denser grids are the Planck "gray" opacity tables.
The finer energy grid (especially from u = 0. to u = 10.) will greatly
reduce the noise in the integration of the Planck "gray" opacities for
densities below .0001 gm/cc.
In order to use the dense u grid tables, users must specify each
element by the current MATID number given on the
current available material list
page and replace the l at the beginning with an n. Therefore,
if you specify aluminum as Al, al, 13 or l13718, you will get the thinned
grid data files, but if you specify n13718 you will get the new dense
grid files. Please note that there are no dense grid files for the
older versions, such as l13716 or t13710. Only the most current version
for each element has both the thinned and dense grid files.
u = hv / kT
hv is the photon energy in eV and kT is the temperature in eV.
The u grid is selected instead of the photon energy grid because
the same u grid can be used for all temperatures and cover the
important photon energy ranges needed to integrate the Rosseland and
Planck "gray" opacities. These photon energy ranges would be 0. - 20. eV
for a temperature of 1. eV and 0. - 2000. eV for a 100. eV temperature.
For the u grid, the range would be 0. - 20. for both temperatures.
u Values 3900 Point Grid 14,900 Point Grid
_________ ___________________________ ____________________________
0.0
|
| 1250 points, steps of .01 9600 points, steps of .00125
|
12.5
|
| 750 points, steps of .01 1600 points, steps of .005
|
20.0
|
| 1000 points, steps of .01 1000 points, steps of .01
|
30.0
|
| 233 points, steps of .3 700 points, steps of .1
|
100.0
|
| 300 points, steps of 3.0 900 points, steps of 1.0
|
1000.0
|
| 300 points, steps of 30.0 900 points, steps of 10.0
|
10000.0
|
| 67 points, steps of 333.3 200 points, steps of 100.0
|
30000.0
_____ _____
3900 points 14900 points