Lithium vapor density diagnostics for the PWFA plasma source at IPR

A photo-ionized Lithium vapor plasma source for Plasma Wakefield Acceleration (PWFA) experiment at Institute for Plasma Research (IPR), Gujarat has been developed as part of the ongoing Accelerator Programme. The plasma source is a 40 cm long Li vapor based heat pipe oven photo-ionized by a UV laser (193 nm) to produce a uniform column of Li plasma. Li vapor in the oven is produced by heating solid Li in helium buffer gas. In PWFA experiment, an accurate measurement of Li vapor density is important as it has got a direct consequence on the electron density of the plasma formed by single photon ionization. Three different optical diagnostics (White light absorption, UV absorption and Hooks method) have been employed in the present experiment to measure the Li neutral column density in the plasma source. The characterization and optimization studies of the Li vapor column formed in the oven have been carried out using these different optical diagnostics as a function of external oven temperature and the He buffer gas pressure. Here, we present the comparative study of the three different measurements carried out for the estimation of the line integrated Lithium vapor density. (author)