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Pixelated semiconductor gamma-ray detectors are a versatile tool for the characterization of radiation in a wide range of environments. The latest low noise, waveform sampling electronics coupled with innovative reconstruction algorithms allow for year-on-year improvements in energy and position resolution. Meanwhile, CdZnTe’s unparalleled combination of high energy resolution and 3D position sensitivity enables many advanced algorithms for imaging and other applications. The development of radiation detectors based on new materials further ensures a bright horizon for this technology. This dissertation presents new work covering all three aspects of pixelated semiconductor radiation detection in the Orion Group of the University of Michigan. New electronics development is presented which aims to condense all the front end control logic and some of the digital processing currently done by field programmable gate arrays and computers down onto a single silicon chip. This can enable significant further reductions in radiation detector size, weight and power while maintaining the high performance and imaging capabilities characteristic of CdZnTe. Subpixel position reconstruction accuracy and precision was improved by a series of new algorithms. Machine learning models trained to predict subpixel positions from signal waveforms demonstrated improvement over the resolution that could be achieved with classical techniques. The radial position was predicted to less than 200 µm precision using only the collecting pixel waveform. Additionally, an improvement of 50 µm position resolution is demonstrated for the XY subpixel coordinates. Meanwhile, a range of algorithms are considered for correcting position distortions due to space charge, nonideal weighting potentials and other effects. An iterative technique is presented that successfully corrects some of the distortions in the cathode/anode ratio depth reconstruction. A technique is presented to image pair production events in CdZnTe. This is typically accomplished with electron tracking. Here, a method to reconstruct images without electron tracking is presented, which exploits asymmetries in pair production and charge induction physics. The imaging capability is demonstrated both in simulation and in experiment with the 4.44 MeV photons from a PuBe source. Extensive work is done to characterize and improve the performance of perovskitebased radiation detectors. Thanks to waveform digitization and principal component analysis techniques, world-record performance of less than 1% full width at half maximum for the Cs-137 662 keV line is achieved with pixelated CsPbBr3-based detectors. Hybrid organic-inorganic solution grown perovskites are also demonstrated to work, with a resolution of less than 3% achieved for the same Cs-137 line.

High energy density (HED) systems are some of the most extreme environments ever created by mankind. Systems with pressures greater than 1 MBar can only be created by a handful of devices on earth, often utilizing high intensity lasers or pulsed power machines. HED systems offer a view into an extreme form of matter only seen in stellar cores, supernovas and other powerful astrophysical systems. Creating HED systems on Earth offer the possibility, if the physics and technology can be matured, to one day create a fusion power plant. If a system is hot and dense enough, the fusion reaction can drive more fusion reactions through the alpha particle depositing its energy. There has been a generation goal of getting this fusion chain reaction to create high yield and gain, however, this regime, called ignition, has remained elusive. Diagnosing HED systems to understand the degradation preventing ignition presents a challenge. HED pockets are often short lived (nanoseconds or picoseconds) and concurrent with a release of a physical blast shock, nuclear particles, a strong electromagnetic pulse and a noisy radiation environment. Cherenkov detectors to measure energy thresholded, time resolved gamma rays is one such technique that can be applied to these systems to gain insight and understanding to the properties of HED systems. In this dissertation, the fundamentals and background of this diagnostic technique are applied in detail to three HED systems. Gas Cherenkov detectors are applied onto the National Ignition Facility's inertial confinement fusion ignition campaigns. Inertial confinement fusion uses high powered lasers to compress a capsule full of deuterium-tritium fuel surrounding by a carbon ablator shell, which is used to push the fuel into high densities and temperatures. A technique to isolate a 4.4 MeV carbon gamma ray is introduced and applied to understand the areal density and compression of the outside portion of the inertial confinement fusion pusher. The new data reveals that the outside portion of the pusher followed the expected hydrodynamic predicted trends, while the inner fuel portion of the pusher looks to be degraded and less compressible. This data suggests for specific degradation mechanisms acting on the capsule that preferentially degrade the fuel, such as ablator-ice mix. The time resolution of the gamma detector also gives information about the velocity of the carbon ablator during the fusion burn. Second, gamma ray measure mix studied field on the OMEGA laser system are shared, showing a complicated mix landscape for spherical implosions. Aerogel Cherenkov detectors are fielded on the Mercury pulsed power facility at the Naval Research Lab which creates an accelerated electron beam to create a strong bremsstrahlung x-ray source. The Aerogel Cherenkov detectors are able to characterize and measure time resolved signals of the x-ray pulse, vital information for the x-ray pulse to be feed into a radiography or photofission source. This dissertation presents a body of work that applies a diagnostic technique to an extreme experimental conditions, receives novel measurements and interprets their results.