Megapixel ion imaging with standard video

We present an ion imaging approach employing a real-time ion counting method with standard video. This method employs a center-of-mass calculation of each ion spot (more than 3x3 pixels spread) prior to integration. The results of this algorithm are subpixel precision position data of the corresponding ion spots. These addresses are then converted to the final image with user selected resolution, which can be up to ten times higher than the standard video camera resolution (640x480). This method removes the limiting factor imposed by the resolution of standard video cameras and does so at very low cost. The technique is used in conjunction with dc slice imaging, replacing the local maximum searching algorithm developed by Houston and co-workers [B. Y. Chang, R. C. Hoetzlein, J. A. Mueller, J. D. Geiser, and P. L. Houston, Rev. Sci. Instrum. 69, 1665 (1998)]. The performance is demonstrated using HBr and DBr photodissociation at 193 nm with 3+1 resonance enhanced multiphoton ionization detection of hydrogen and deuterium atom products. The measured velocity resolution for DBr dissociation is 0.50% (delta v/v), mainly limited in this case by the bandwidth of the photolysis laser. Issues affecting slice imaging resolution and performance are also discussed. (c) 2005 American Institute of Physics.