Micro-Mirrors Help Better Understand Synchrotron Light Sources

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Synchrotron radiation is useful as a diagnostic tool for cutting edge research in many areas including material, chemistry, biology and etc.  In most of the synchrotron radiation light source facilities, a variety of techniques are provided to fulfil the purpose including macromolecular crystallography, soft and hard x-ray microscopy, microXAS imaging, x-ray scattering and diffraction, photoemission spectroscopy and x-ray absorption and emission spectroscopies. Usually, the synchrotron radiation is generated by relativistic electron beam passing through a special magnet called undulator or wiggler. To generate the synchrotron radiation with certain intensity and brightness, the electron beams will be stored in the synchrotron accelerator or storage ring and the total charge will be accumulated. Due to the beam loss in the storage ring, fresh relativistic electron beam will be injected into the ring to keep the charge or current more or less the same.

In the past, the injection process was studied in simulations, but the experiment result was few especially the injection process with the stored beam present. That is because the old method to measure the injection with the stored beam present suffers from the dynamic range. When using synchrotron radiation as a diagnostic for the electron beam itself, the intensity ratio between the injection and the stored beam will be more than 104, which is beyond the dynamic range of most conventional cameras. In a paper recently published in Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, H.D. Zhang et al. developed an imaging system using a digital micro-mirror-array device (DMD) combined with conventional camera to solve the dynamic range issue regarding to this problem. With a few examples, this method demonstrate the ability for online diagnose of the injection, which will benefit for better understanding the injection process and further studying the advanced or renowned injection mode.

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