User:Scott collis
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Hello! This is just a temporary place holder page until I get around to making it better... I will try to contribute a bit more to en.wiki as I find I am using it so much in writing my PhD thesis... If you want to find out more about me you can visit my Personal page
Ok this stuff here is a place to save stuff I am working on:
One technique for the determination of electron temperatures in a plasma to monitor two spectral lines of neutral helium, one involving a triplet and one involving a singlet upper state. While the emissivity of the individual transitions has a dependence on both electron temperature and density the ratio of the two emissivities responds pre-dominantly to temperature variations.
The rate of increase of the density of helium atoms in a particular excited state, i, can be calculated by using the equation shown in FIGURE \cite{thecrm} where n(i) is the density of helium atoms in the quantum state i, C(i,j) is the rate co-efficient for collisional excitation from state i to j, A(i,j) is the rate of spontaneous transition from state i to j, S(i) the rate co-efficient for ionisation from state i and α(i),β(i),βd(i) are the rate co-efficients for three body, radiative and dielectric recombination, respectively. For a plasma in quasi steady-state we can take the left hand side of the equation to be zero yielding a set of simultaneous equations describing the population density of each state.
The collisional radiative model (CRM) solves the equations shown in \icf{fig:crm} for the population densities up to a principal quantum number (left hand side of \icf{fig:energylevs}, denoted as n) of 7. Between n=8 and n=10 triplet and singlet states are grouped separately and n=11 to n=26 all states are grouped into a state representing all states within that quantum number.
