| 摘要 |
PURPOSE:To extend the dynamic range, by switching a voltage impressed to an accelerator electrode of a diode electron gun into a voltage value giving a beam amount required for the standard operation and a voltage value giving a larger beam amount. CONSTITUTION:An output signal extracted from a photoconductive target 7 is amplified at a preamplifier 10, then output is passed through a clamp circuit 51, a clip circuit 52 and a pulse waveform shaping circuit 53, and a signal of bright part only of a level corresponding to two three times a reference signal is extracted. A switching circuit 54 is controlled with said output, a voltage having a value giving a required beam amount for the standard operation is impressed to the accelerator electrode 8 of the diode pickup tube 1 from a DC power supply 56 normally, and a voltage having a value providing a larger beam amount from a DC power supply 57 is impressed to the accelerator electrode 8 at a lighter part. |
