Laser-driven atomic-probe-beam diagnostics

A new laser-driven atomic-probe-beam diagnostic (LAD) is proposed for local , time-resolved measurements of electric field and ion dynamics in the acce lerating gap of intense ion beam diodes. LAD adds new features to previous Stark-shift diagnostics which have been progressively developed in several laboratories, from passive observation of Stark effect on ion species or fa st (charge-exchanged) neutrals present naturally in diodes, to active Stark atomic spectroscopy (ASAS) in which selected probe atoms were injected int o the gap and excited to suitable states by resonant laser radiation. The L AD scheme is a further enhancement of ASAS in which the probe atoms are als o used as a local (laser-ionized) ion source at an instant of time. Analysi s of the ion energy and angular distribution after leaving the gap enables measurement, at the chosen ionization location in the gap, of both electros tatic potential and the development of ion divergence. Calculations show th at all of these quantities can be measured with sub-mm and ns resolution. U sing lithium or sodium probe atoms, fields from 0.1 to 10 MV/cm can be meas ured. (C) 2000 American Institute of Physics. [S0034-6748(00)04512-3].