## 2 Methods  
The experiments were performed on an FEI Tecnai Osiris operated at 200 kV with four silicon drift detectors forming a Super-X EDX system [14] and a vintage Gatan Imaging Filter (GIF 200). The detector used to record the individual electron events is the Advapix Minipix TPX3 camera which we selected for its size fitting the dimension of a custom-developed retractable mount sliding into the original video camera port of the GIF. The time resolution of this detector is 1.56 ns and the maximum count rate that it can handle before saturation is 1 \(\times\) 10\({}^{6}\) events per second. This is low compared to conventional imaging in TEM but since we focus on core-loss EELS, the detector can record these much lower incoming inelastic count rates with ease. Because standard installed EDX pulse processors do not give information on the TOA of the incoming X-rays, the amplified analog output signals from the Super-X system are connected to an electronic pulse processor (DANTE) [15] which is able to identify both the energy of the X-ray and its TOA. The sampling frequency of the AD converters on the 8 input channels is 8 ns which forms a lower limit for the time resolution in our setup. However, as will be shown in Section 4.6, the limit on the time resolution is currently dominated by the X-ray detector response time and well above this 8 ns sampling rate. Compared to our previous work [11], the implementation of the pulse processor gives the ability to record single X-ray events from all four silicon drift detectors (SDD) of the Super-X doubling its collection efficiency. Furthermore, a versatile scan engine [13] is hooked up to the microscope to synchronize the timing of the electron and X-ray signals with the scanning of the electron probe. To this end, the scan engine sends a trigger signal to both electron detector and X-ray pulse processor to start the acquisition. Since the devices use different clocks, synchronization signals are sent out every 200 us to prevent the clocks from drifting too much with respect to each other and with respect to the scan sequence. Thanks to the open Python API of both external scan engine, DPP and Minipix detector a fully automated measurement scheme can be set up conveniently. In this work, two different types of acquisition are used. One is the static beam where we acquire only one X-ray and EEL spectrum. The other one is the mapping configuration where we scan the beam over the sample while recording EELS and EDX spectral data as an event stream. Since the TOA of every event is stored and synchronized to the scan engine, the position of the probe for every event can be determined. Please note that because of this event-based detection, the limit on scan speed is only determined by the scan engine and scan coil system response time. The possibility to recreate the EELS and EDX maps is similar to the work in [PERSON] et al. [16] where an event-based camera is used to retrieve the 4D-STEM datasets at us speeds. When the coincidence mapping is performed, multi-frame scanning is used to minimize the effects of drift by providing the ability to align the multiple scan frames in software. For every acquisition, the camera length is reduced to the minimum and the largest 3 mm GIF aperture is chosen giving an estimated collection angle of 20 mrad in an attempt to maximize the collection efficiency of the electron detection. After the data collection, the single X-ray and electron events are coupled to each other where for every X-ray, all the electrons within a time window of 100 us are labeled as a coincidence event and the energy of the X-ray (\(E_{x}\)), electron energy loss (\(E_{e}\)) and the time difference between these two events (\(\Delta t\)) are stored as a new event containing three components (\(\Delta t\), \(E_{x}\), \(E_{e}\)). A time window of 100 us is chosen as a preprocessing step in order to ensure that the correlation will be properly captured.