instrument. 4 Roadside Tracker results for a moving vehicle with two sources. 7 5 Graphical representation of the process of single frame vehicle image capture. 8 6 Block diagram of the overall data acquisition system. 7 Block diagram of s single channel of gamma-ray data acquisition. 8 Schematic diagram of gamma-ray buffer data structure. 9 Illustration of vehicle slices. 10 Progress of video hardware during the project. 11 Bayer image format. 12 Block diagram of video processing data flow. 13 Targets on the trailer roof. 14 Stereo point search approach. 15 Standard and high resolution video images. 16 Project timeline. 17 Major events during design phase. 18 Major events during POC construction phase. 19 Major events during phase 4. 20 RST standard 2-lane development site. 21 RST development site on main ORNL thoroughfare. 22 First offsite data collection site. 23 Major events during improvement, test and evaluation phase. 24 Major events during the limited use exercise. 25 Site at SRNL where high-speed tests were conducted. 26 RST performance vs velocity. 27 RST deployed near Belmont raceway. 28 Improved gamma performance after removal of video frame offset.
We have evaluated a collimator-less gamma-ray imaging system, which is based on thin layers of double-sided strip HPGe detectors. The positions of individual gamma-ray interactions will be deduced by the strip addresses and the Ge layers which fired. Therefore, high bandwidth pulse processing is not required as in thick Ge detectors. While the drawback of such a device is the increased number of electronics channels to be read out and processed, there are several advantages, which are particularly important for remote applications: the operational voltage can be greatly reduced to fully deplete the detector and no high bandwidth signal processing electronics is required to determine positions. Only a charge sensitive preamplifier, a slow pulse shaping amplifier, and a fast discriminator are required on a per channel basis in order to determine photon energy and interaction position in three dimensions. Therefore, the power consumption and circuit board real estate can be minimized. More importantly, since the high bandwidth signal shapes are not used to determine the depth position, lower energy signals can be processed. The processing of these lower energy signals increases the efficiency for the recovery of small angle scattering. Currently, we are studying systems consisting of up to ten 2mm thick Ge layers with 2mm pitch size. The required electronics of the few hundred channels can be integrated to reduce space and power. We envision applications in nuclear nonproliferation and gamma-ray astronomy where ease of operation and low power consumption, and reliability, are crucial.
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