Speaker
Description
With the increase in repetition rate of free-electron lasers, bandwidth requirements of front-end detector ASICs become of utmost importance. The Linac Coherent Light Source (LCLS-II) at SLAC National Laboratory will achieve an increase in pulse rate, which is expected to reach a frequency of 1 MHz. Detectors at LCLS have hitherto been operating under the full-frame readout scheme, where data from the entire detector pixel matrix are transmitted pulse by pulse. To cope with this increase in pulse frequency, new approaches to handle data are needed. In low-occupancy experiments, one of the options is to follow a sparsified readout scheme, in which the only pixels that transmit data are the ones that recorded a signal over a user-designated threshold. In low-occupancy experiments, this greatly reduces the required bandwidth to read out an event frame and consequently allows for data extraction under high repetition rate scenarios. An ASIC prototype exploiting sparsification is SparkPix-T, a front-end detector ASIC composed of 176 x 192 pixels with a pitch of 100 μm x 100 μm. The device performs high-precision time and space measurements and is capable of operating at up to 1 MHz repetition rate, thus making it compliant with the LCLS-II upgrade for experiments requiring a time-of-flight detector. In order to support the readout of SparkPix-T under bench-testing and LCLS beamline characterization scenarios, an FPGA-based data acquisition system was developed. The DAQ system employed multi-gigabit transceiver links over fiber and fast serial electrical links via custom protocols to handle the data. It also supported the configuration of the ASIC and offered the ability to interface with the FEL timing data distribution network. This article describes the data acquisition system in detail and showcases results from experimental testing.
| Workshop topics | Front-end electronics and readout |
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