at Princeton University by NASA /Goddard Research grant #NSG -5277.

The Texas Instruments1 Virtual Phase CCD imager has been successfully operated in the frontside electron-bombarded mode. The entire active area of the imager was covered with 130 nm of thermally grown gate oxide while only the clocked half of each pixel was addi­ tionally covered with a 500 nm polysilicon electrode. No protective overcoat was grown over the imager. A 20 kV electron beam was focused onto the imager to a total dose in excess of 120,000 primary electrons per pixel. Both the parallel and serial clocks were operated between -15 V and +2 V throughout, and no adjustment in any of the operating parameters was required. However, flat band shifts on the order of 2 V were detected. Single primary electron events were clearly detected with a signal-to-noise ratio exceeding 10. In excess of 90% of the secondary charge generated by a primary event was collected in a single pixel. The standard virtual phase imager with only the protective overcoat deleted can be used with a photocathode in the electron-bombarded mode for observing low- to-moderate light levels and can act as a true photon counter.*