Measurement of the electron density in a strontium vapour laser

Abstract

A two-wavelength (10.6 mu m/632.8 nm) Mach-Zehnder interferometer is employed to provide radially and temporally resolved measurements of the electron density in a longitudinally discharge-excited strontium vapour laser over a wide range of operating conditions. From these results it is possible to gain an estimate of both the electron temperature and the Sr2+ ion density.

Sr+excitation and electron temperatures in an Sr+laser

“…There is a slight fall in T. during the afterglow period of spontaneous emission, shown in the upper curve of figure 5, which is about half the size of the fall in T, calculated from measurements of the electron density (Loveland and Webb 1992). Although T, and T. are not necessarily related, it is worth noting that the greater fall, in x, is for higher buffer gas pressure of 330mbar, compared with loombar, which results in a greater cooling rate of the electrons.…”

“…where n, is the electron density in m -3 while the units of T. and AE are eV. Measurements of the electron density (Loveland and Webb 1992) have yielded values in the region of 7 x IOzo m -3 for ne and have also permitted calculations of T. of around 4OOO K (0.34 eV), and so the condition in equation ( 5) is satisfied by a factor of 30 for the energy gap of 0.7 eV spanning the three upper levels observed in this experiment.…”

“…The top curve ( T x , 0) was obtained from assuming a Boltzmann distribution and the lower points ( T s , 0 ) from equation (3). Also shown (A) are the calculations of T. based on measurements of the electron density during the shorter duration of spontaneous emission when the buffer gas pressure is 330 mbar (Loveland and Webb 1992).…”