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Photon science with extended ultra violet (EUV) to soft X-ray photons generated by state of the art synchrotrons and FEL sources imposes an urgent need for suitable photon imaging detectors. Besides a high quantum efficiency, requirements on such EUV detectors include high frame rates, very large dynamic range, single-photon sensitivity with low probability of false positives, small pixel pitch and (multi)- megapixels. Owing to their unique features back illuminated scientific CMOS (sCMOS) imagers can be tailored to these particular needs [1]. In general application driven detector development is a sensible, albeit time consuming approach allowing to take full advantage of the luminosity improvements that FELs and diffraction-limited synchrotron rings (SRs) can provide. Conversely such characteristics can be found in few state of the art commercial detectors based on sCMOS, which have been recently developed for other applications mainly in the visible light regime. In particular back thinned sCMOS are suited for experiments exploiting the water window (between 282 eV and 533 eV) and transition metal L-edges, a target photon energy range which implies vacuum operations. Applying some modifications, in particular UHV compatibleness, these commercial devices can be disposed for EUV and soft X-ray applications as demonstrated by [2].
In this contribution we describe the adaption of the PCO edge 4.2 bi for soft X-ray imaging in the energy range from 35 eV – 2000 eV. The PCO edge is build around the GSENSE2020BSI-APM-NUN PulSar back thinned sCMOS sensor, which has been designed by Gpixel (https://www.gpixel.com) and has been processed by Tower Semiconductor (https://towersemi.com). The sensor comprises 2048 x 2048 pixels with a pixel size of 6.5 µm x 6.5 µm, which translates into an active area of 13.3 mm x 13.3 mm. The sensor exhibits a full well capacity of 48 000 e- and a readout noise of 1.9 e- (rms) with a typical dynamic range of 88 dB. The integration time can be adjusted between 10 µs – 2 seconds. Using its USB 3.1 data interface the maximum frame rate is given by 40 fps for the full frame while it can reach for instance 520 fps for a region of interest of 2048 x 128 pixels. In addition, a total of 4 trigger signals are provided to synchronize image acquisitions. Vacuum compatibility has been obtained by sealing the carrier board of the sensor, which constitutes the barrier between vacuum and normal atmosphere. In this fashion it is possible to keep the entire readout and trigger electronics in air. At the moment a KF flange based interface plate is utilized to attach the camera and subsequently sensor to the experimental vacuum chamber (Figure 1). Here we present the first measurements carried out at the CiPo beamline at Elettra Sincrotrone Trieste with a modified soft X-ray PCO Edge 4.2 bi showing a very high quantum efficiency greater than 60% in the energy range between 30 eV and 100 eV and greater than 80% for energies between 100 eV and 1000 eV. Soft X-ray imaging capabilities have been assessed by means of slanted edges and generation of Airy patterns through a pin hole (Figure 1). Moreover, spectral X-ray imaging with this single photon processing detector can be accomplished.
[1] A. Marras, J. Correa, S. Lange, et al., J. Synchrotron Radiat. 2021, 28, 131.
[2] Desjardins, K., Medjoubi, K., Sacchi, M., Popescu, H., Gaudemer, R., Belkhou, R., et al. (2020). research papers. J. Synchrotron Rad (2020). 27, 1–13.
