D. Cohen
15July09

Argon Spectral Modeling with PrismSpect

I used a very large atomic model (every available level that leads to optical or UV transitions; about 2000 levels), and ran a series of steady-state, non-LTE ("collisional-radiative") ionization/excitation and spectral synthesis calculations. 

All models assumed 99% H and 1% Ar by number and a total ion density of 10^12 cm^-3

For each calculation, I plotted the near UV and optical range 200 to 1100 nm that (I think) roughly corresponds to the range over which the SSX spectrometer operates (looking at plots Tim gave me of spectra from argon shots) and I also plotted the far UV range 70 to 110 nm, where there are some lines that are significantly stronger than those seen in the optical range.  I have labeled all strong (and many weak) lines. 

Executive summary: at temperatures of 10 to 15 eV, the 213.6/219.3 nm line ratio (Ar V to Ar IV) looks like a promising temperature diagnostic.  Either line could be a good IDS target, too. 

As Tim had already noticed, when the plasma temperature is low, there are lines in the red visible but when it's higher, the lines shift to the blue. 

I have hand-written some of the strongest lines for each simulation on the next page.   Following that, are copies of two measured spectra (again, from Tim).  Then there is a summary of the simulations, listing the mean charge state of neon and the ionization fractions for Ar and H. 

Following that are the annoted spectral plots.