Design of a timing circuit for random laser triggering on aerosol particles

A versatile timing device has been developed that permits a variety of lasers, including Nd : YAG (yttrium aluminum garnet), excimer, and CO 2 lasers, to be triggered at random times. The present application is to single-particle mass spectrometry, where the corresponding arrival times are random and signaled by a laser light-scattering apparatus. The timing circuit triggers the Nd : YAG laser flashlamps approximately 200 μ s prior to the desired laser output pulse, followed by the Q -switch triggering pulses, which can also be used to control other lasers and/or the ion extraction optics. The flashlamps are discharged ten times per second to maintain the proper heat load on the Nd : YAG laser flashlamps. If fewer than 10 particles ∕ s are detected by light-scattering apparatus, the unit sends substitute pulses to maintain the average of 10 discharges ∕ s . When the particle flux is higher than ten per second, the circuit is designed to ignore the extra particle events. A simpler version of the circuit is also described, which accepts two timing inputs and outputs a pulse for ion extraction at a preselected time.