High-Yield Pulsed Neutron Generator

A pulsed neutron generator is proposed for the detection of special nuclear material. A recently developed microwave-excited plasma neutron generator will be pulsed to produce the activating neutrons whose pulse lengths vary from 100 microseconds to 2 ms with a fall time of less than 1 microseconds. We demonstrated that we can increase the peak yield as a function of either RF or microwave power, and thus maintain a high average yield. We modified two existing Adelphi generators to demonstrate pulse widths from 50 microseconds to 2 ms with repetition rates of 250 Hz to 5 KHz. We observed pulsed operation by observing the plasma photon yield and the fast and thermal neutron yields. We found that the generator could maintain its plasma at low pressures even though it was being pulsed. We computer simulated the use of a gate electrode to both truncate the pulse fall time and determine neutron pulse structure. We fabricated this gate electrode and its accompanied electronics and installed them in an Adelphi generator. The electrode was shown to operate with the design voltages. The proposed Phase II generator is designed to be low cost, and mechanically and electronically robust, to ensure its wide distribution and use at ports throughout the world. The proposed device is expected to be much lighter than the existing Adelphi generators and require less power. It is a high average yield generator that meets with SNM-detection-system integrators' requirements. The project has a high probability of success based on the Phase I research successes and recent development by Adelphi and Lawrence Berkeley National Laboratory.