A sensitive dispersion interferometer with high temporal resolution for electron density measurements

A dispersion interferometer with a sensitivity of up to 10(-4) fringe shift s and a time resolution of about 1 ns was developed. This time resolution e xceeds previous systems by three orders. The operation of the dispersion in terferometer and its characteristic properties are discussed and the experi mental setup of the installation is explained in detail. The stability of t he interferometer was tested and it was shown that its operation point drif ts less than 0.25 rad/h. The interferometer was used to investigate the hig h power ion diodes at the pulse generator KALIF, where focused proton beams with power densities of up to 1 TW/cm(2) are generated. For the very first time the electron line density inside the diode gap, where the protons are accelerated, could be directly measured. The line density was on the order of several 10(13) cm(-2). A straightforward estimation of the line density using a simplified diode model proved to be in excellent agreement with th e results. The dispersion interferometer can be used for sensitive electron density measurements on nanosecond time scales. Further developments to im prove the sensitivity are discussed. (C) 2000 American Institute of Physics . [S0034-6748(00)03807-7].