Characterization of an architecture for front-end pixel binning in an integrating pixel array detector

TL;DR

This paper presents a novel front-end pixel binning architecture for hybrid pixel array detectors, enabling a trade-off between spatial resolution and frame rate, with tested performance showing promising results and areas for improvement.

Contribution

The paper introduces and characterizes a new front-end binning design in an integrating pixel detector, demonstrating its performance and potential benefits over traditional post-processing binning.

Findings

Binned pixels perform well with some performance degradation.

Noise increase due to parasitic capacitance is less than a factor of 2.

Binned mode maintains linear response up to ~10^7 x-rays/s.

Abstract

Optimization of an area detector involves compromises between various parameters like frame rate, read noise, dynamic range and pixel size. We have implemented and tested a novel front-end binning design in a photon-integrating hybrid pixel array detector using the MM-PAD-2.0 pixel architecture. In this architecture, the pixels can be optionally binned in a 2$\times$2 pixel configuration using a network of switches to selectively direct the output of 4 sensor pixels to a single amplifier input. Doing this allows a trade-off between frame rate and spatial resolution. Tests show that the binned pixels perform well, but with some degradation on performance as compared to an un-binned pixel. The increased parasitic input capacitance does reduce the signal collected per x-ray as well as increases the noise of the pixel. The increase in noise is, however, less than the factor of 2 increase one would observe for binning in post-processing. Spatial scans across the binned pixels show that no measured signal intensity is lost at the inner binning unit boundaries. In the high flux regime, at a 2$\times$2 pixel wide beam spot (FWHM) size, binned mode responds linearly up to a photon flux of ~10$^{7}$ x-rays/s, and performs comparably with un-binned mode up to a photon flux of ~10$^{8}$ x-rays/s. While this study demonstrates a proof of concept for front-end binning in integrating detectors, we also identify changes to this early-stage prototype which can further improve the performance of binning pixel structures.