See also: [[Orion Group Pixelated CZT Schematics]] and [[CdZnTe (CZT) Detectors]] # Single-Polarity Charge Sensing Motivation: Understanding the contribution of holes, and why they're mitigated in pixelated [[CdZnTe (CZT) Detectors]] Single-Polarity Charge Sensing is a method to mitigate the problem established by hole trapping in [[CdZnTe (CZT) Detectors]]. For CdZnTe, the [[mobility-lifetime product]] ($\mu \tau$) of holes is two orders of magnitude lower than that for electrons [^1] . The problem of hole trapping was solved through the introduction of a co-planar grid and later a pixelated design on the anode. These techniques are only sensitive to the electron motion in the detector, and not the holes, hence, "single-polarity charge sensing". In other words, [[Holes Do NOT Generate Signal in Pixelated CZT Detectors, the Cathode Signal Comes from the Electrons Moving Away From the Cathode]]. [^1]: [[@zhangEVENTSRECONSTRUCTION3D2005]] ## In Pixelated Detectors: When electrons are far away from the anode, they may induce many small signals on each pixel, but as they drift toward the anode, these signals are more localized to a single pixel, causing all other transient signals to fall to 0. This is a direct result of the [[Shockley-Ramo Theorem]] and the [[Small Pixel Effect]] and is visualized in the figure seen in the note: [[The Cathode and Anode Waveform shapes are generated directly from the Shockley-Ramo Theorem - Pixelated Anode Case]] and in [[@petrykAlgorithmsElectronicsProcessing|Matt's thesis]]. ![[Pasted image 20230116164256.png]]