User:Scott collis

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 $\alpha (i),\beta (i),\beta _{d}(i)$ 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.