This box synchronizes two pulsed lasers. When the first laser fires some of the light falls on a photo diode. The signal from the photo diode is ~200mV and ~20nS long. This input and an adjustable reference level are sent to a high speed comparator. The comparators output is used to trigger a couple of one-shots. The first one-shot gates a photomultiplier tube (PMT) immediately while providing a variable delay to the second one-shot. The second one-shot provides a fixed width output pulse to trigger the second laser. This allows the first laser to fire (ablating a target) while the PMT is off (no risk of destroying it). Immediately after the first laser fires the PMT is turned on to monitor the probe beam. After a few uS the second laser will fire (probing the plasma that the first laser created). This delay circuit is currently being used in Dr. Kwong's lab.