Abstract
We present here a new method of performing X-ray edge-subtraction ptychographic imaging by combining multiple harmonics from an undulator synchtrotron source and an energy discriminating photon counting detector. Conventionally, monochromatic far-field X-ray ptychography is used to perform edge subtraction through the use of multiple monochromatic energy scans to obtain spectral information for a variety of applications. Here, we use directly the undulator spectrum from a synchrotron source, selecting two separate harmonics post sample using the Pixirad-1/Pixie-III detector. The result is two monochromatic images, above and below an absorption edge of interest. The proposed method is applied to obtain Au L-edge subtraction imaging of a Au-Ni grid test sample. The Au L-edge subtraction is particularly relevant for the identification of gold nanoparticles for biomedical applications. Switching the energy scan mechanism from a mechanical monochromator to an electronic detector threshold allows for faster spectral data collection with improved stability.
Highlights
We present here a new method of performing X-ray edge-subtraction ptychographic imaging by combining multiple harmonics from an undulator synchtrotron source and an energy discriminating photon counting detector
The Pixirad-1/Pixie-III X-ray Photon Counting Detector (XPCD) coupled to a CdTe sensor was used for the experiment
In colour mode Pixirad-1/Pixie-III outputs two images in a single acquisition: the first is the integration of the counts between Tlow and Thigh, the second is the integration of the counts above Thigh
Summary
We present here a new method of performing X-ray edge-subtraction ptychographic imaging by combining multiple harmonics from an undulator synchtrotron source and an energy discriminating photon counting detector. Monochromatic far-field X-ray ptychography is used to perform edge subtraction through the use of multiple monochromatic energy scans to obtain spectral information for a variety of applications. We use directly the undulator spectrum from a synchrotron source, selecting two separate harmonics post sample using the Pixirad-1/Pixie-III detector. We demonstrate a new modality for edge-subtraction ptychography that makes use of multiple undulator harmonics and a multiple threshold X-ray Photon Counting Detector (XPCD) — the Pixirad-1/Pixie-III11 — as an harmonic selector. The nature of the Pixie-III is such that the acceptable count rate is significantly higher compared to a hyperspectral detector[12], resulting in faster acquisition times while still offering energy discriminating capabilities. We demonstrate firstly that this is possible with the bandwidth of a single undulator harmonic and secondly that the harmonic selection can be achieved with an electronic threshold configuration, removing the need for a monochromator
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