Figure 2
(a) Sketch of the data acquisition scheme. Individual X-ray pulses are detected by the APD; a fast preamplifier converts individual charge pulses into voltage signals. Readout by a high-speed analog-to-digital converter (ADC) is followed by FPGA-based data encoding and transfer through the PCI bus. Online data analysis can be performed by a graphics processing unit (GPU); the full data stream can be recorded. (b) Pulse-to-pulse online data analysis can be performed at bunch frequencies fb >> 31 MHz. In the example of waveform averaging, individual X-ray pulses are stored in registers in the GPU depending on the time of arrival, the dynamics as induced at, for example, fpp = 1 kHz (sketched in red) can therefore be probed in a stroboscopic manner. (c) Photograph (back side) of the high-bandwidth preamplifier PCB. The quadrant APD is located in the center; amplified signals are routed to four SMA connectors. Bias and supply voltages are provided via a mixed Sub-D connector. (d) Photograph of the detector head containing the quadrant APD as well as the preamplifier PCB as mounted at the beamline P08 at PETRA III. |