Enhanced Light Element Sensitivity and Throughput Enabled by a New Pulse Processor Design in Super-X G3

Energy dispersive X-ray spectroscopy in the transmission electron microscope provides reliable nanoscale chemical composition analysis and is fundamental in the research of advanced nanomaterials and functional devices across materials science. In the past, the sensitivity of the signal measured by minimum mass fraction and single atom sensitivity has been increased with the development of the silicon drift detector designs and collection angle increases [1,2]. Dead time and energy resolution of sensors limit efficiency at higher count rates. This performance is critical in high current applications such as fast or large field of view 2D maps and compositional 3D studies using tomography where beam–specimen interaction increases at higher specimen tilts leading to high count rates. Here a compromise between energy resolution and dead time of the sensor is required by choosing different discriminator times in the electronics. In practice, this imposes a trade-off between throughput and energy resolution: settings that optimize energy resolution usually produce dead times above 30% (and thus signal loss), while low dead time settings used at high count rates reduce signal loss but worsen energy resolution. We present the performance of the new-generation Super-X G3 system (G3) and directly compare it to the established Super-X G2 detector (G2). When comparing the high-resolution shaping time of G2 (10 µs) with the optimized shaping time of G3 (1.3 µs), a clear reduction in detector dead time for G3 is observed while maintaining or improving energy resolution (Fig. 1). Measurements of the influence on the performance with different optimized pulse processing and shaping time settings of the new design will be presented. A marked increase in detection efficiency for low-energy X-ray signals is shown in the comparison of the boron signal in spectra of LaB6 demonstrating the sensitivity increase of the G3 while providing higher energy resolution compared to G2 (Fig. 2). G3 provides six-fold higher B Kα peak intensity and improved low-energy signal quality compared to the G2. The increase in detection efficiency at high count rates is demonstrated in Fig. 3, where line profiles of net counts over a precipitate are compared for a spectrum image taken with the same conditions using both detectors. We will show the performance gains in multiple compositional analysis applications and how the new design enhances light-element sensitivity and provides increased throughput at high X-ray count rates while simultaneously improving peak resolution. These improvements are particularly relevant for spectroscopy applications where sensitivity, speed, and accuracy are equally critical and where trade-offs are not acceptable. Comparison of the dead time of Super-X G2 versus G3 as a function of input count rate per segment. (Left) Summed-segment energy resolution for G3 and G2, highlighting the improved and stable performance of G3 across a wide range of output count rates. (Right) Equal beam current (0.2 nA) spectra of a LaB6 crystal on lacey carbon support recorded on the same area using the G2 (Left) and G3 (Right) detectors. Measured B peak FWHM is 42 eV for G2 and 34 eV for G3. The enhancement of the signal strength is obvious (∼6 times increase of the B peak height). Elemental map comparison of G2 and G3 on Al-Cu-Li (2055) alloy with Mn precipitates. (Inserts) The total acquisition time is 35 min using a 1.6 nA beam current. The substantially lower dead time of G3 (15% vs 55% for G2) yields more than twice the signal in a line profile across the precipitate, indicating the higher sensitivity of G3. Sample courtesy of Michal Jambor, Czech Academy of Sciences, Czechia.