11March 2021 ESRFnews

INSIGHT

not be able to catch such a high rate of photons, but unlike XIDER it will sport much smaller pixels. This will satisfy those users hoping to maximise the greatly improved coherence of the new source.

Are those projects the only aspects to the DDP? No. For XIDER and SPHIRD to work, ISDD engineers will need to work on other key technologies in parallel. In particular, they will need to improve the efficiency, spatial resolution and timing response of the two main sensing technologies semiconductor sensors and scintillators which convert X-ray photons to measurable signals. They will also need to improve the performance of energy- dispersive detectors, which are used in spectroscopy experiments. Finally and obviously more photons and faster experiments mean more data: these will be sent, dispatched and treated via an upgraded, high-throughput distributed data- acquisition system.

Has ISDD made any progress on all these fronts? The ISDD engineers are currently testing the first application-specific integrated circuits, or ASICs essentially the electronics behind individual pixels for the new detector concept XIDER. Those for SPHIRD will follow before long. Fully working prototypes are likely to be several years away, but the development of the key technologies could have an effect on existing detectors much sooner, within two years. Meanwhile, combined with the new source and other upgraded instrumentation, the latest commercial devices will still provide users with X-ray data of unprecedented quality. There will always be an X-ray eye to assist, says Ruat. We just want our eyes to be open as wide as possible. 

Jon Cartwright

for the vast majority of hard X-ray scattering and diffraction experiments in which photons are counted one by one; and charge integration, in which the total charge generated by absorbed photons is integrated over time. Each of these schemes has its drawbacks: photon counters can be overwhelmed by EBS-like fluxes, while charge integrators, which are usually not designed for operation with continuous beams, cannot discard noise. By combining both schemes in one system, the first of the DDP s new detectors, XIDER, will be able to integrate and digitise the charge of high-energy photons, providing high dynamic-range, high duty-cycle, noise-free operation at very high flux about one billion photons per second per pixel, a 100-fold improvement on the best existing devices (JINST 15 C01040). By comparison, with just a 10-fold improvement, the second of the new detectors, SPHIRD, will

The EIGER2 technology being commissioned on many ESRF beamlines offers a count rate that is significantly better than other existing commercial systems. However, the ESRF needs to further detector technology itself if it is to make the most of its new source.

Why are detectors important? The ESRF s EBS upgrade has opened up a new vista in X-ray science. Users are planning time-resolved experiments at high photon energies; they want to combine multiple techniques and resolve previously unresolvable details. Ultimately, detectors are what enable this new science to be seen in the words of ESRF detector engineer Marie Ruat, they are the eyes of the synchrotron . The question is whether they are up to the task. Confronted with X-rays of unrivalled brightness and coherence, many older detectors would only be able to see an incomplete picture.

So we need new detectors? Yes, and in fact since the upgrade many new commercial detectors have already become operational, are being commissioned or are on their way. Eight of these use EIGER2 technology, whose maximum count rate is significantly better than other current commercially available systems. These detectors are already commissioned at the beamlines ID15B, ID11, ID27, ID22, ID10, ID17, for high-energy X-ray science, and ID02; an upgrade for the structural-biology beamline ID23-1 is in the pipeline. Another system, the Jungfrau 4M, will operate at 16 Gb/s for synchrotron serial-crystallography on the forthcoming flagship beamline at ID29. But commercial detectors are only part of the solution; after all, there is currently no other light source on Earth with the ESRF s requirements. For that reason, since 2018 the ESRF Instrumentation Services and Development Division (ISDD) has been working on a detector development plan (DDP), which will result in the creation of two entirely new detector systems.

What are these? Until now, most detectors have operated on the basis of one of two schemes: photon counting currently the preferred 2D detection technology

To maximise the potential of its new source, the ESRF is pushing the boundaries of detector technology in a major development project.

The eyes of the ESRF EBS

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ESRFMar21_Insight_v5.indd 11 26/02/2021 10:09