| 摘要 |
<p>The amplified pulses from a radioactivity detector are coupled through a delay line to a linear gate. The amplified pulses from the detector are also connected to a discriminator. The output of the discriminator is AND gated in a logical gate with a clock pulse which is synchronized with a high energy neutron source. The AND gate triggers a first single shot multivibrator which in turn triggers the linear gate. The delay line allows for the time required for the detector pulse to rise to the discriminator threshold and for the propagation delay in the logic circuitry. The linear gate opens before the arrival of the detector pulse and closes after it passes through. A J-K flip-flop circuit is triggered by the trailing edge of the output of the first single shot multivibrator to disable the AND gate, thus causing the linear gate to pass only the first detected pulse having the necessary discriminator level. The output of the AND gate is OR gated with the output of a second single shot multivibrator which is triggered off the trailing edge of the clock pulse. The output of the OR gate drives a negative high voltage pulser which is connected to a negative pulsing ring in a neutron generator. The leading edge of the clock pulse drives a positive high voltage pulser which is connected to a positive pulsing ring in the neutron generator. The neutron generator is thus extinguished upon the detection of the first detector pulse occurring within the clock pulse interval having the necessary discriminator threshold. In an alternative embodiment, a second AND gate is used to gate a source control clock pulse and the output from the J-K flip-flop to provide a driving pulse for the ion source pulser.</p> |
