Characterisation of target plasma required for REB-plasma interaction studies using cylindrical Langmuir probes

The target plasma required for relativistic electron beam (REB)-plasma interaction studies has been generated by a coaxial plasma gun. The measurement of electron density and temperature has been carried out using cylindrical Langmuir probes. Probes both oriented parallel and transverse to the flow have been used. The spatial as well as temporal variation of electron density and temperature have been studied. The typical electron density and temperature measured by probe were in the range of 9.0-3.5*1013 cm-3 and 5-7 eV respectively. The typical e-folding decay time of density was 6.2 mu s, while no appreciable change in electron temperature was observed until 10 mu s after the peak density. The density decays by about 50% at distance of 30 cm from the gun. The plasma flow velocity has been measured by the time of flight technique and was found to be 2.5*106 cm s-1. The plasma radius measured by dosimeter film, at distance of 30 cm from the gun was 3 cm.