Figure 1: When a radiation pulse with a dose rate exceeding a selectable threshold is sensed, the NED generates (1) An NED Output Voltage (step function); (2) An Open Collector for a Wired “OR”; and (3) A Latch (resetable flag). The Open Collector signal lags the NED Output Voltage by ~ 1ns.

The NED is designed to “trip” at a pre-determined dose rate (threshold level). The threshold level can be set between 5E5 Rad(Si)/s and 1E8 Rad(Si)/s using an external resistor. The response time is less than 15 ns. The NED produces 3 output voltages:

1. NED Output Voltage . When no nuclear event is detected, the output voltage is at the logic “High”, typically between 3V and 5V. When a nuclear event is detected, a step function, at the logic “Low” is generated. The step function is available for ~ 2 μs and is automatically reset by the NED circuitry. If there are multiple events, the NED will “be extended” for another 2 μs if the 2 nd event is more than 200 ns after the 1 st.

2. Open Collector . This feature enables the System to tie together a number of NEDs, so that if one (or more) of them goes off, the System gets the NED Output Voltage described above. This feature, a Wired OR, is illustrated in Fig. 2.

3. Latch . The difference between the NED Output Voltage and the Latch is that the Latch is a flag that gets reset by the System. In contrast, the NED Output Voltage is reset by the NED circuitry and is available to respond to additional pulses.

Figure 2: Several NEDs share a common Pull Up Resistor. If ANY of the five NEDs “trip”, the System will receive an NED Output Voltage indicating that a nuclear event has occurred