This program help to visualize the exponential decreasing nature of plasma density in a one dimensional slab by ambipolar diffusion. I have chosen the particular point at distance x = 0.01m from the slab to simulate the decay of density.

% This is a program to plot the decay of plasma by ambipolar diffusion in one dimensional slab:

clear all

close all

n_o = 1e12; % initial density in m^-3

L = 0.024; % length of edge from centre of the slab in m

D = 0.4; % ambipolar diffusion coeffecient in m^2/sec

T = (2*L/pi)^2/D; % tau:mean time between collision

t = 0:.00002:.002;

x = .010;

n = n_o*exp(-(t./T)).*cos(pi*x./2/L); % density distribution

comet(t,n),xlabel('t(time of decay)'),ylabel('n(density of plasma)'),

title('exponential decay of plasma dendity at position "x = .010m" of slab')