Backside-illuminated scientific CMOS detector for soft X-ray resonant scattering and ptychography

Abstract

The impressive progress in the performance of synchrotron radiation sources is nowadays driven by the so-called `ultimate storage ring' projects which promise an unprecedented improvement in brightness. Progress on the detector side has not always been at the same pace, especially as far as soft X-ray 2D detectors are concerned. While the most commonly used detectors are still based on microchannel plates or CCD technology, recent developments of CMOS (complementary metal oxide semiconductor)-type detectors will play an ever more important role as 2D detectors in the soft X-ray range. This paper describes the capabilities and performance of a camera equipped with a newly commercialized backside-illuminated scientific CMOS (sCMOS-BSI) sensor, integrated in a vacuum environment, for soft X-ray experiments at synchrotron sources. The 4 Mpixel sensor reaches a frame rate of up to 48 frames s−1 while matching the requirements for X-ray experiments in terms of high-intensity linearity (>98%), good spatial homogeneity (<1%), high charge capacity (up to 80 ke−), and low readout noise (down to 2 e− r.m.s.) and dark current (3 e− per second per pixel). Performance evaluations in the soft X-ray range have been carried out at the METROLOGIE beamline of the SOLEIL synchrotron. The quantum efficiency, spatial resolution (24 line-pairs mm−1), energy resolution (<100 eV) and radiation damage versus the X-ray dose (<600 Gy) have been measured in the energy range from 40 to 2000 eV. In order to illustrate the capabilities of this new sCMOS-BSI sensor, several experiments have been performed at the SEXTANTS and HERMES soft X-ray beamlines of the SOLEIL synchrotron: acquisition of a coherent diffraction pattern from a pinhole at 186 eV, a scattering experiment from a nanostructured Co/Cu multilayer at 767 eV and ptychographic imaging in transmission at 706 eV.

Single-shot experiments at the soft X-FEL FERMI using a back-side-illuminated scientific CMOS detector

“…This first version is equipped with a 'standard' GPIXEL CMOS-BSI sensor developed for visible spectrum applications, the GSENSE400BSI-TVSIB. As reported by Desjardins et al (2020), the sensor has a maximum quantum efficiency (QE) around an energy of 1000 eV and a poor efficiency for lower beam energies (due to the surface antireflection protective coating). Compared to the prototype noncoated version, GSENSE400BSI-GP, or the latest version introduced recently by GPIXEL, GSENSE400BSI-Pulser (Harada et al, 2020; https://www.gpixel.com), the efficiency of GSENSE400BSI-TVSIB is only 20% around 50 eV.…”

“…As described previously, the magnetic scattering intensity has been measured as a function of the FEL intensity. In order to safely test the linearity of the CMOS, the FEL intensity has been kept far from the damage threshold of the sensor based on our previous X-ray characterization (Desjardins et al, 2020).…”

“…It is based on 2048 Â 2048 pixels of 11 mm 2 with two gains and a combined gain mode to achieve the high dynamic range (HDR). The illumination on the back side (BSI), the thin silicon epitaxial thickness and the entrance window coating layer enable a good efficiency to be obtained over the entire XUV and soft X-ray domain (Desjardins et al, 2020). The dynamic range can reach 92 dB with a low electronic noise (down to 2 e À RMS) and a relatively large charge full-well capacity (up to 100 ke À ).…”

“…The sensor has met with a certain success and it is already integrated by several camera manufacturers for UV and visible applications (https://andor.oxinst.com, https://www.photo metrics.com, https://www.ximea.com, https://www.pco.de, http://www.tucsen.com, etc.). Recently, two versions have been evaluated at beamlines of Synchrotron SOLEIL (Desjardins et al, 2020), reporting a sufficient X-ray quantum efficiency and showing the particular interest in this CMOS technology. It has been shown that these sensors dramatically increase the full-frame acquisition speed (48 Hz for the standard gain and 24 Hz for the HDR mode) compared to the commercial Back-Side-Illuminated Charge-Coupled Device (CCD-BSI) routinely used at soft X-ray facilities.…”

“…It has been shown that these sensors dramatically increase the full-frame acquisition speed (48 Hz for the standard gain and 24 Hz for the HDR mode) compared to the commercial Back-Side-Illuminated Charge-Coupled Device (CCD-BSI) routinely used at soft X-ray facilities. The first utilization of this device opened up perspectives for soft X-ray ptychography (Mille et al, 2022), soft X-ray scattering techniques (Desjardins et al, 2020;Marras et al, 2021) and other applications, such as soft X-ray fluorescence (Staeck et al, 2021). Another obvious application concerns the implementation of such a class of detectors at ultra-short X-ray sources (laser-based X-ray source or free-electron laser), where the low frame rate of the standard commercially available CCD-BSI (see, for example, Vodungbo et al, 2012;Wang et al, 2012) limits the time of data collection.…”