Micrometer-resolution imaging using MÖNCH: towards G₂-less grating interferometry

Abstract

MÖ NCH is a 25 mm-pitch charge-integrating detector aimed at exploring the limits of current hybrid silicon detector technology. The small pixel size makes it ideal for high-resolution imaging. With an electronic noise of about 110 eV r.m.s., it opens new perspectives for many synchrotron applications where currently the detector is the limiting factor, e.g. inelastic X-ray scattering, Laue diffraction and soft X-ray or high-resolution color imaging. Due to the small pixel pitch, the charge cloud generated by absorbed X-rays is shared between neighboring pixels for most of the photons. Therefore, at low photon fluxes, interpolation algorithms can be applied to determine the absorption position of each photon with a resolution of the order of 1 mm. In this work, the characterization results of one of the MÖ NCH prototypes are presented under low-flux conditions. A custom interpolation algorithm is described and applied to the data to obtain high-resolution images. Images obtained in grating interferometry experiments without the use of the absorption grating G 2 are shown and discussed. Perspectives for the future developments of the MÖ NCH detector are also presented.

X-ray Fourier ptychography

“…The experimental complications that we encountered during these proof-of-principle measurements can mostly be addressed rather easily. Most cumbersome were limitations posed by the detectors, i.e., their limited size, which required their being repositioned when scanning the objective lens, slow readout when using charge-coupled devices (CCDs), or low-flux requirements when aiming for subpixel data interpolation ( 19 ). Yet, faster and larger detectors are, in principle, available and/or are being developed.…”

“…As the required precision of the objective movements scales with the resolution, the objective was mounted on a 3D piezo-electric stage with a maximum range of 100 μm. The data were collected using a 400 × 400 pixel prototype MOENCH detector with a physical pixel size of 25 μm ( 19 , 28 ). Using slits 22 m upstream of the sample, the flux was reduced such that single-photon events were detectable within 0.25 ms acquisitions to allow for data interpolation to a pixel size of 6.25 μm.…”

“…The data interpolation on the detector ( 19 ) introduced periodic artifacts (fig. S2), which were addressed by setting the contribution of the corresponding frequencies to zero.…”

Full-field spectroscopic measurement of the X-ray beam from a multilayer monochromator using a hyperspectral X-ray camera

“…In the sensor, each detected X-ray photon induces a charge cloud, typically spanning multiple pixels (Kimmel, 2008). When the incident photon flux is sufficiently low, the charge clouds are observed separately in the read out frames, allowing for accurate reconstruction of the total deposited charge and location of the interaction (Kimmel et al, 2006;Ordavo et al, 2011;Cartier et al, 2016). Its high-end readout electronics are interfaced with a new and in-house-developed control and processing software chain (Van Assche et al, 2018b), resulting in an energy resolution of approximately 150 eV (at Mn K) and a spatial resolution better than the pixel size.…”

Silicon pixel R&D for the CLIC detector

“…Nonetheless, samples have been produced with slim-edge 200 µm thick planar sensors and active-edge sensors of 50 µm thickness, allowing measurements of their performance. It should be noted that large-scale bumpbonding of 25 µm pitch detectors has already been demonstrated [10], where access to the ASIC wafers is possible. Some testbeam performance plots of a CLICpix bump-bonded to a 50 µm thick active-edge sensor can be seen in figure 5.…”