The Advanced Photon Source
a U.S. Department of Energy Office of Science User Facility

Early Closure of Some XSD Beamlines Due to APS-U Construction


As you may have heard by now, the construction of multiple beamlines for the Advanced Photon Source Upgrade (APS-U) Project will require a staggered installation schedule, which must start significantly ahead of the dark period.  This is due to the limited capacity of vendors for critical components such as enclosures, and the need to distribute the effort from local staff and contactors.  That means some operating X-ray Science Division (XSD) beamlines will be going off line before the start of the dark period due to the need to move some programs to accommodate feature beamlines, while other XSD beamlines will be interrupted and re-started before APS shuts down for the installation of the new multi-bend achromat-based storage ring. The XSD, APS, and APS-U managements have developed a draft schedule for beamline closures and program interruptions.  While the current stance of Argonne due to COVID-19 will likely affect this schedule, we would like to start communicating with the user communities as early as possible, so that they can plan for any affected research programs.

The first impacted beamline on the schedule is 4-ID-C.  Sector 4 will become dedicated to hard x-rays with the conversion of 4-ID-D into POLAR, an APS-U featured beamline focused on studies of magnetic materials at extreme conditions. POLAR will make use of the entire insertion device straight section currently shared between soft x-ray and hard x-ray undulators. The enclosure for POLAR is tentatively scheduled for construction in calendar year 2021.  This construction schedule forces an earlier shut down of 4-ID-C, the soft x-ray beamline, due to interferences in floor space.  On February 21, 2020, APS management sent a message to all recent 4-ID-C users stating that 4-ID-C will cease operations April 2021 and will only be accepting users until the 2021-1 run. General User Proposals requesting time at 4-ID-C will be accepted up to the 2021-1 cycle (included). Proposals not allocated by the end of the 2021-1 cycle will become inactive.

The next beamlines expected to be impacted are 20-ID and 4-ID-D.  As a result of the APS-U plan to build a long beamline at 20-ID, the programs at 20-ID will be moving to canted-undulator beamlines at 25-ID, which is currently under construction. 4-ID-D was scheduled for temporarily suspended user operations in April 2021 (the end of the 2021-1 cycle) for a period of 1.5 to 2 beam-time cycles.   We were preparing letters of notification to recent users of 20-ID and 4-ID-D but have decided to hold those letters for now as the construction schedule may be impacted by the current coronavirus situation.  When a clearly picture of the impact of COVID-19 on the APS-U construction schedule emerges, we will update letters, if necessary, and send them to the relevant user communities as soon as possible.  Hopefully we will be able to post the entire early closure schedule soon after that.

For questions or more information, please contact Denny  Mills ( or Jonathan Lang (   ― Denny Mills

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