Characterisation of the Medipix3 detector for 60 and 80 keV electrons

Abstract

In this paper we report quantitative measurements of the imaging performance for the current generation of hybrid pixel detector, Medipix3, used as a direct electron detector. We have measured the modulation transfer function and detective quantum efficiency at beam energies of 60 and 80keV. In single pixel mode, energy threshold values can be chosen to maximize either the modulation transfer function or the detective quantum efficiency, obtaining values near to, or exceeding those for a theoretical detector with square pixels. The Medipix3 charge summing mode delivers simultaneous, high values of both modulation transfer function and detective quantum efficiency. We have also characterized the detector response to single electron events and describe an empirical model that predicts the detector modulation transfer function and detective quantum efficiency based on energy threshold. Exemplifying our findings we demonstrate the Medipix3 imaging performance recording a fully exposed electron diffraction pattern at 24-bit depth together with images in single pixel and charge summing modes. Our findings highlight that for transmission electron microscopy performed at low energies (energies <100keV) thick hybrid pixel detectors provide an advantageous architecture for direct electron imaging.

Quantitative imaging of hybrid chiral spin textures in magnetic multilayer systems by Lorentz microscopy

“…Experimental images were obtained in Fresnel mode using a JEOL ARMcF operated at 200kV [33]. Additionally, we used a pixelated detector, Medipix3, to acquire images rather than a traditional CCD camera due to superior noise performance [34]. In Fig.…”

Electron crystallography with the EIGER detector

“…MAPS detectors are more suited to higher electron energies due to their reduced thickness, which minimizes electron scattering within the sensor (McMullan et al, 2014(McMullan et al, , 2009. The Medipix family of hybrid pixel detectors (Llopart et al, 2002;Ballabriga et al, 2011) have previously shown good spatial resolution between 60-120 keV electron energies (McMullan et al, 2007(McMullan et al, , 2009Mir et al, 2017). However, hybrid pixel detectors are currently not suited to high-resolution imaging of electrons with energies above 100 keV due to their large point spread, but, unlike monolithic detectors, hybrid pixel detectors are ideally suited for measuring electron diffraction patterns due to their high dynamic range, on-pixel electroncounting capabilities, radiation hardness and high frame rate (Nederlof et al, 2013;van Genderen et al, 2016).…”

Sub-100 nanosecond temporally resolved imaging with the Medipix3 direct electron detector

“…CSM was originally conceived to handle multi-pixel events arising from spreading of the secondary electron-hole charge under diffusion. For high energy electrons, we have shown that the algorithm can provide simultaneous improvement of both the DQE and MTF for energies in the range 60-80 keV [20], therefore correcting for lateral spreading in the sensor of the primary radiation also. The process of detecting and counting an incident primary electron is now discussed for two cases with close reference to Figure 1 Following the electron arrival, e-h pair charge generated in the sensor volume along the path traveled by the primary electron moves under the applied bias and this movement induces a signal at the readout pixel electrodes.…”

“…When operating in CSM, it is sensible to set the THA threshold to a low value (so that all individual pixels in an event cluster are considered) and THB to a higher value. Since the latter operates on summed charge, the DQE performance is improved, provided primary electron energies have an average lateral spread that is less than the 2 × 2 pixel block size [20]. The count dependence on threshold value for CSM and SPM are shown in Figure 5(a).…”