Effect of Aperture Closure in Intense Pulsed Light Ion Beam Measurement

The effect of aperture closure on the irradiation of an intense pulsed light ion beam of ion current density (J i) 1–8 kA/cm2 has been evaluated experimentally. By using biased ion collectors the aperture closure is observed for J i>1 kA/cm2 and the closing speed increases with increasing J i or decreasing aperture size. At J i=8 kA/cm2, an aperture of diameter 0.3 mm is closed 40 ns after the rise of J i. From the evaluation of the magnetic energy spectrometer, the effect is greater for heavy ions of C+, O+, than for protons.