Novel alignment techniques used in multiphoton ionization experiments for laser plasma beat wave

This paper describes the techniques used to create a fully ionized plasma by the multiphoton ionization of gases at pressures of a few Torr to give an initial electron density precision of better than a few percent, necessary for beat‐wave experiments. A gas containment vessel has been constructed using high vacuum techniques with a temperature control system to maintain the fill gas pressure constant. Novel alignment techniques are used that do not require an alignment target placed in the vessel. This involves the use of a rotating pencil beam to determine the focusing of the optics.