Three-dimensional (3D) moment imaging with a USB3 oscilloscope

We report a new implementation of a recently developed 3D momentum imaging technique [Lee et al. J. Chem. Phys. 141, 221101 (2014)]. The previously employed high-speed digitizer in the setup is replaced by a portable USB3 oscilloscope. A new triggering scheme was developed to suppress trigger jitters and to synchronize the signals from a camera and the oscilloscope. The performance of the setup was characterized in the study of laser desorption/ionization of 2,5-dihydroxybenzoic acid on a velocity map imaging apparatus. A ∼60 picosecond time resolution in measuring time-of-flight is achieved with a count rate of ∼1 kHz, which is comparable to the system using high-speed digitizers. The new setup affords great portability and wider accessibility to the high-performing 3D momentum imaging technique.