A diamond double-sided strip detector for alpha-tagging in associated particle imaging

- In associated particle imaging, neutrons from deuterium-tritium fusion are used to interrogate objects of interest. The associated particle imaging technique utilizes an alpha-tagging sensor in the neutron generator to detect the alpha particle that is emitted antiparallel to the neutron, providing neutron birth time and direction. This technique of neutron imaging and induced fission imaging can provide higher contrast image reconstructions and better estimations of fissile material mass than passive measurement techniques. The performance goals of an alpha-tagging sensor in associated particle imaging are a 700-ps timing resolution, a 0.5 mm spatial resolution, high level of radiation hardness, low sensitivity to X-rays, high signal-to-noise ratio, and survivability in the high temperature bake out of the neutron generator. Currently employed YAP scintillators are overwhelmed by the intense X-ray field in the neutron generator, requiring a new alpha tagging sensor design to be developed. We have developed and tested a diamond double-sided strip detector as a proposed sensor for associated particle imaging. Diamond is radiation hard, has a low sensitivity to X-rays, fast timing capabilities, high signal-to-noise ratio, and can withstand the temperatures of bake-out. The spatial resolution can be accomplished with a charge division readout and double-sided strip design. We measured the timing resolution of a single crystal chemical vapor deposition (CVD) diamond with a Cividec C6 charge amplifier readout by measuring the time-of-flight of 241Am alpha particles between a thin plastic scintillator and the diamond. We also fabricated a polycrystalline CVD diamond double-sided strip detector with charge division readout to test the spatial resolution of the design. We found that the detector met both the 700-ps timing resolution and the 0.5 mm spatial resolution goals (both reported as FWHM resolution).