Semiconductor detectors with optimized proximity signal readout

Semiconductor-based radiation detectors are used in detection, imaging, and spectroscopy of x-rays, gamma rays, and charged particles for applications in the areas of nuclear and medical physics, astrophysics, environmental remediation, nuclear nonproliferation, and homeland security. Detectors used for imaging and particle tracking are more complex as they typically must also measure the location of the radiation interaction in addition to he deposited energy. In such detectors, the position measurement is generally achieved by dividing or segmenting the electrodes into many strips or pixels and then reading out the signals from all electrode segments. This requires complex detector fabrication and signal readout processes and is often associated with high cost, low yield, and high power requirements. There clearly is a need for a detector technology that can achieve fine position resolution while maintaining the excellent energy resolution intrinsic to semiconductor detectors, can be fabricated through simple processes, does not require complex electrical interconnections to the detector, and can reduce the number of required channels of readout electronics. Proximity electrode signal readout, in which the electrodes are not in physical contact with the detector surface, satisfies these needs. On equal footing is the need to develop low cost, high density readout electronics adapted to the unique demands required in a proximity electrode readout detector. Our overall project vision is to demonstrate the viability of a large HPGe strip detector using novel proximity sensing electrodes paired with a low cost, high density spectrometer capable of real time signal processing. Phase I allowed us to successfully refine the concept of the proximity sensing in HPGe detectors by employing a large area detector prototype in single sided strip configuration and reconstructing sub-strip pitch position resolution. In Phase II we will further develop and optimize this promising new technology resulting in a fully operational, multi-dimensional position sensitive HPGe detector with real-time processing and display of energies and positions. We will achieve this goal through detailed characterization and modeling of the detectors, which will guide the optimization of the fabrication processes and implementation of proximity sensing HPGe detectors. In parallel we will refine and optimize signal processing schemes that enable the determination of energies and positions of the gamma-ray interactions in real time. Commercial Applications and Other Benefits: If this concept can be successfully demonstrated for imaging as well as particle tracking applications, XIA and our commercialization partner ORTEC will develop benchtop and portable products intended for medical and mining industries, basic and applied research in within DOE and DHS offices.