Detective Quantum Efficiency of the Timepix4 Hybrid Pixel Detector and its Application to Parallel-Beam Diffraction

Abstract

The detective quantum efficiency (DQE) and normalised noise power spectrum (NNPS) of the Timepix4 hybrid pixel detector in event-driven mode in TEM have been measured at 100 kV and 200 kV. In a raw data readout mode, the zero-frequency DQE exceeds 0.9 at both 100 kV and 200 kV. At the Nyquist frequency, the DQE remains above 0.2 at 100 kV but drops close to zero at 200 kV. Initial parallel-beam diffraction data from a polycrystalline gold nanoparticle sample is reported which shows that at 200 kV Timepix4 can detect weak diffracted information beyond a 75 mrad half-angle.

Figures (5)

• Figure 1: MTF, NNPS and DQE of Timepix4 detector for 100 kV and 200 kV electrons. X-axes are the fraction of spatial frequency to the Nyquist frequency of the detector. The ideal MTF and DQE curves are calculated as described in Section \ref{['sec:method_ideal_mtf_and_dqe']}.The semitransparent background of DQE curves indicates estimated uncertainties, as discussed in Section \ref{['sec:uncertainty_dqe']}.
• Figure 2: $\sigma_{\mathrm{MTF}}$, $\sigma_{\mathrm{NPS}}$, $\sigma_{\mathrm{DQE}}$, $\sigma_{\mathrm{NNPS}}$, $\frac{\sigma_{\mathrm{MTF}}}{\mathrm{MTF}}$, $\frac{\sigma_{\mathrm{NPS}}}{\mathrm{NPS}}$, $k_{\mathrm{DQE}}$ and $k_{\mathrm{NNPS}}$ for 100 kV and 200 kV. X-axes are the ratio of spatial frequency to the Nyquist sampling frequency of the detector. $\sigma_{\mathrm{NPS}}(0)$ and $\frac{\sigma_{\mathrm{NPS}}(0)}{\mathrm{NPS}(0)}$ are marked as dots on y-axis.
• Figure 3: Parallel-Beam Diffraction pattern from a polycrystalline gold sample recorded on a Timepix4 detector at 200 kV and corresponding average radial line profiles. (a) Diffraction pattern recorded on a Timepix4 detector. Colormap is log-scale. (b) Average radial line profile of the diffraction pattern in (a), plotted on both linear (red line) and log scales (blue line).
• Figure 4: Average radial line profile of the diffraction pattern (0 to 40 mrad, corresponding to a limiting d-spacing of 0.06275 nm) and indexed gold reflections. The line profile is plotted on log scales. Indexed reflections are indicated by black dotted lines.
• Figure 5: Experimental average radial line profile (red solid line, background removed) and simulated diffraction intensity distribution (green dash line). The blue dotted lines indicate the detector edges. (a) line profiles from 8 to 85 mrad (corresponding to d-spacings from 0.3138 to 0.0295 nm). (b), (c) and (d) line profiles in the range of 8 to 35 mrad (corresponding to d-spacings from 0.3138 to 0.0717 nm), 30 to 60 mrad (corresponding to d-spacing from 0.0837 to 0.0418 nm) and 55 to 85 mrad (corresponding to d-spacing from 0.0456 to 0.0295 nm), respectively with different y-axis scales applied.