Four-frame gated optical imager with 120-ps resolution

In this paper we describe the operation and applications of a commercially available framing camera capable of four separate two-dimensional images with each frame having a 120-ps gate width. The time separation between frames can be selected arbitrarily. Fast gating of a single frame is accomplished by using a wafer image intensifier tube in which the cathode is capacitively coupled to an external electrode placed outside of the input window of the tube. This electrode is then pulsed relative to the microchannel plate by a narrow (120 ps), high-voltage pulse. The transmission of the tube as a function of time has been verified using a laser-diode pulser and is approximately Gaussian with a FWHM of 120 ps. Multiple frames are obtained by using multiple gated tubes which can then share a single bias supply and pulser with relative gate times selected by the cable lengths between the tubes and the pulser. A beamsplitter system has been constructed which produces a separate image for each tube from a single scene. In the present system, the tubes use S-20 photocathodes with an 18 mm diameter and quartz input windows. Spatial resolution is unchanged between d.c. and fast gated operations and has been measured to 10 1p/mm. Applications to time-dependent behavior will be presented.