Figure 1
The codes have been used to predict the behavior of plasmas produced in the laboratory and
to analyze plasma sources of commercial interest. The first successful application of the
codes involved the analysis of opacity measurements. Here x rays are used to backlight a
plasma and the resulting transmission is recorded. For a given density and temperature,
level populations can be calculated assuming local thermodynamic equilibrium. These
populations with the calculated photoexcitation and photoionization cross sections are used
to predict the absorption properties of the plasma. Figure 1 is a comparison of theoretical
and observed transmission from experiments performed at the Rutherford Appleton
Laboratory in England. The absorbing medium is an aluminum plasma at a temperature of
40 eV and density of 0.0135 g/cm3.
Figure 1
It is well known that impurity radiation is a significant energy loss mechanism in tokomak plasmas. Here impurities from the wall contaminate the plasma, and electron collisions with these ions produce radiation which degrades the reactor performance. Also, impurity gases can be introduced into certain regions of the reactor to cool critical plasma facing components such as the divertor. The latter scheme is being considered for the development of the International Thermonuclear Experimental Reactor ( ITER ). Thus there is a crucial need for accurate calculations of radiative power loss for a variety of elements of interest. The Los Alamos codes have been used to provide more accurate estimates of power loss for various impurity ions. Significant discrepancies between these calculations and the standard method, which uses less accurate atomic physics, have been uncovered. The effects of electron density and metastable states have been found to be important.
The codes have been used to study several plasmas of commercial interest. One project involves the production of extreme ultraviolet radiation for lithography applications. Relativistic electron beams are injected into a slightly ionized gas. Energy is transfered from the beam electrons to the plasma electrons which become very hot. The hot electrons then ionize and excite the surrounding gas atoms to produce the desired radiation. The kinetics codes have been used to predict the output spectrum. In addition, the capability to provide the simultaneous solution of level populations and the free-electron energy distribution is being implemented for this project.
The codes have been used to generate xenon atomic data for the one- and two-dimensional modeling of plasma display panels. Here an electrical discharge is used to excite a gas and produce radiation which is used to drive a display panel. Since the computer simulations are very time consuming the calculated atomic data must be reduced to a model containing only a few atomic states. An averaging technique has been developed to perform this data reduction.
Other applications include spectroscopic diagnostics for inertial confinement fusion (ICF).
Here spectroscopy is used to determine the plasma temperature and density within ICF
hohlraums by comparison with calculated line ratios. Another project is a Los Alamos
/Russian collaboration to study highly resolved spectra from plasmas produced by various
means. This study has resulted in the identification of many satellite lines emitted from
magnesium and silicon plasmas. The codes have also been used to model x-ray laser plasmas
with regard to the gain coefficient for various lasing transitions. Various laser produced
plasmas from both Los Alamos and other outside sources have been studied. In addition,
electron beam effects were found to be important for determining spectral properties of
plasmas produced by pulsed power devices such as the x-pinch. Figure 2 shows a comparison
of theory and experiment for the Be-like spectrum of aluminum observed in the Cornell
University x-pinch. The electron beam effects are included in the calculation by using a non-Maxwellian electron distribution.
Figure 2