| 摘要 |
A rapid random accessed electron beam memory system (10) comprises a disc (13) mounted for rotation and supporting an information storage medium. An electron gun (18, 19, 20) is mounted for movement across the disc. The gun has ultra-compactness and extremely low mass, yet capable of developing a finely focused electron beam probe at high beam current densities. The gun comprises a low-mass field emission cathode and means for heating the cathode, the cathode having an emitting tip and being adapted to receive a predetermined electrical potential to form a high brightness electron source at the tip. A low-mass electrode receives a predetermined accelerating potential for receiving electrons from the tip to form an electron beam. A single focus lens of low mass is positioned a relatively short object distance from the tip for receiving the beam and forms a finely focused, yet intense electron beam probe at a relatively short focal distance therefrom. The probe is of such high current density due to the brightness of the source and the power of the lens that the minimum diameter of the probe is significantly affected by space charge effects in said beam. The sum of the object and image distances are so small as to suppress the space charge contribution to probe diameter and thereby make practicable a finely focused, yet extremely intense electron beam probe. The total mass of the gun is so low as to be readily capable of being rapidly accelerated and decelerated to effectuate a rapid random accessing of data stored on the information storage medium. |
