Comparison between modeled and experimental emission rates in ASTRAL argon plasmas.

Argon emission rate coefficients are measured in the ASTRAL helicon plasma source using a 0.33 m scanning monochromator and a CCD camera. ASTRAL produces bright intense Ar plasmas with the following parameters: n$_{e}$ = 10$^{12}$ - 10$^{13}$ cm$^{-3}$ and T$_{e}$ = 2 - 10 eV, B-field $\le $ 1.3 kGauss, rf power $\le $ 2 kWatt. A rf compensated Langmuir probe is used to measure T$_{e}$ and n$_{e}$. In this experiment Ar I, Ar II and Ar III transitions are monitored as a function of T$_{e}$ while n$_{e}$ is kept constant. Thus, experimental emission rates are obtained as a function of T$_{e}$ and compared to theoretical predictions. Using the ADAS suite of codes, we present spectral modeling of Ar plasmas produced in the ASTRAL helicon plasma source. Recent R-matrix electron-impact excitation data are combined with a new R-matrix calculation that includes pseudo-states contributions. Our collisional-radiative formalism assumes that the excited levels are in quasi-static equilibrium with the ground and metastable populations.~ Good to excellent agreement has been obtained by including T$_{e}$ and n$_{e}$ profiles in the modeling. The experiment-theory comparison confirms that T$_{e}$ is the dominant parameters in determining the emission rate coefficients in these plasmas.