Electronic readout

Charge readout of MPGDs with VMM3a/SRS

The Scalable Readout System (SRS) a powerful and versatile electronic readout system dedicated to MPGDs. The original reference implementation with the APV25 as front-end ASIC is currently replaced with a new version using the VMM3a ASIC. The VMM3a, original developed for the ATLAS New Small Wheel Upgrade is a readout ASIC, specifically developed for the readout of gaseous detectors, offering with its integration into the SRS new capabilities for the readout of MPGDs. Out of the plurality of VMM3a/SRS’ features, two prominent ones are the high rate capability and a continuous self-triggered readout.

Left: Photograph of a triple-GEM detector, equipped with 4 VMM3a hybrid PCBs and the SRS crate in front of it. Middle: X-ray image of a bat, recorded with this set-up. Right: Zoom of the bat’s torso, where the bones can be resolved.


The high rate capability allows for example rapid high quality X-ray imaging. With the amount of recorded events in a short time it is possible to resolve even fine details.

Due to the combination of the high rate capability with a continuous self-triggered readout, it is possible to record continuous processes; in other words: it is possible to record videos with VMM3a/SRS. For example, slicing the data stream into frames of 500 µs length allows to see the opening procedure of the shutter of an X-ray tube.

Illustration of the opening of the shutter of an X-ray tube, with the continuous process sliced in frames of 500 µs length.