A Digital Signal Processing Module for Time-Division Multiplexed Microcalorimeter Arrays

Abstract

We have developed a digital signal processing module for real time processing of time-division multiplexed data from SQUID-coupled transition-edge sensor microcalorimeter arrays. It is a 3U PXI card consisting of a standardized core processor board and a daughter board. Through fiber-optic links on its front panel, the daughter board receives time-division multiplexed data (comprising error and feedback signals) and clocks from the digital-feedback cards developed at the National Institute of Standards and Technology. After mixing the error signal with the feedback signal in a field-programmable gate array, the daughter board transmits demultiplexed data to the core processor. Real-time processing in the field-programmable gate array of the core processor board includes pulse detection, pileup inspection, pulse height computation, and histogramming into on-board spectrum memory. Data from up to 128 microcalorimeter pixels can be processed by a single module in real time. Energy spectra, waveform, and run statistics data can be read out in real time through the PCI bus by a host computer at a maximum rate of ~100 MB/s. The module's hardware architecture, mechanism for synchronizing with NIST's digital-feedback, and count rate capability are presented.