A high speed gateable image pipeline

The authors present the results obtained with a prototype of a high speed gateable Vacuum Image Pipeline (VIP) for selection of non-repetitive images from a continuous stream. It allows snapshots with a very short exposure time (of the order of 10 nanoseconds) to be accepted (or rejected) after a decision time of a few microseconds. The VIP is a vacuum tube equipped with a photocathode, a system of metallic grids and a phosphor screen. Photoelectrons produced by the images focused on the photocathode are guided by a uniform magnetic field parallel to the tube axis. By acting on the grid potentials, the drift time of the photoelectrons inside the tue can be adjusted between 0.3 and 2 microseconds. An image among many others can then be selected by an external trigger with a time resolution between 4 and 30 ns depending on the delay time. The selected photoelectrons are finally accelerated by a high potential (+15 kV) onto the phosphor screen where they reproduce the triggered image. A spatial resolution of 33 lp/mm at a magnetic field of 0.1 T has been measured. The VIP is a useful tool for high energy physics