Abstract
Algorithms and procedures to fully automate retuning of synchrotron radiation beamlines over wide energy ranges are discussed. The discussion is based on the implementation at the National Institute of General Medical Sciences and the National Cancer Institute Structural Biology Facility at the Advanced Photon Source. When a user selects a new beamline energy, software synchronously controls the beamline monochromator and undulator to maintain the X-ray beam flux after the monochromator, preserves beam attenuation by determining a new set of attenuator foils, changes, as needed, mirror reflecting stripes and the undulator harmonic, preserves beam focal distance of compound refractive lens focusing by changing the In/Out combination of lenses in the transfocator, and, finally, restores beam position at the sample by on-the-fly scanning of either the Kirkpatrick-Baez mirror angles or the transfocator up/down and inboard/outboard positions. The sample is protected from radiation damage by automatically moving it out of the beam during the energy change and optimization.
Highlights
Reconfiguring synchrotron radiation beamlines from one X-ray energy to another is a frequent requirement in many types of synchrotron experiments
This situation can arise because the insertion device (ID) retunes to a different energy faster than the monochromator and because the monochromator retunes with constant speed over the Bragg angle change and the ID over the gap change, but neither over the energy change
Based on the time required to move the monochromator from the old to the new Bragg angle, we reduce the speed of changing the ID gap to match and start both devices synchronously
Summary
Reconfiguring synchrotron radiation beamlines from one X-ray energy to another is a frequent requirement in many types of synchrotron experiments. One example is the case of MX beamlines where typical beam time allocated for an experiment ranges between 6 and 24 h and, in most cases, users and lately, due to the pandemic, even support staff, are remote For such short experiments, changing beamline energy should be as simple, smooth, and fast as possible. MX beamlines at the Advanced Photon Source (APS) and distance It simplifies maintaining focus at the same point uses that implementation in the examples, we attempt to when changing energy by reducing the required device shift abstract the discussed algorithms from particular imple- (Vaughan et al, 2011). Both beamlines are equipped with constant exit they introduce an additional complexity to beamline energy height double-crystal monochromators (DCMs). Several alternative algorithms are available to accommodate differing beamline characteristics
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