APS-U and BioCAT

The APS is now nearly 30 years old and badly needs a refit. The APS is scheduled to shut down on April 17, 2023 to build an entirely new accelerator and storage ring (“APS-U”) to replace the current APS ring and restart operations at the beginning of April, 2024. Once completed, the new APS-U ring will provide about 100 times greater brightness than is currently available. This will provide both increased flux and reduced beam sizes for all APS beamlines, including BioCAT 18ID.

Below we provide a brief overview of our plans for this upgrade, and how it will affect our users. This page will be updated with more information and resources as our plans develop.

Benefits of APS-U for BioCAT users:

The new accelerator and storage ring (“APS-U”) will be built in the same building as the existing APS, representing a $815 million upgrade. The new accelerator design (multi-bend acromat) will reduce electron beam emittance (source size x divergence) by a factor of 70 (primarily in the horizontal direction) from its present value. By doubling the beam current (100 to 200 mA) this will also result in approximately twice the flux delivered to our samples. More important for us is the much smaller electron beam source size. The vertical X-ray beam size and divergence will be ~1/3 of what it is now in normal running mode (brightness) and about the same in the timing mode if the ring. The horizontal beam size, however, will be reduced by ~ 1/20 and the beam divergence by ~¼ of what it is now. The spot size of the focused beam with the normal beamline optics, currently ~ 30 x 140 µm will go down to < 30 x 30 µm (conservative) resulting in improved signal to noise in all experiments and shorter minimum exposure times for time- resolved experiments. The more symmetrical focused beam will result in higher quality X-ray fiber diffraction patterns. We will likely be able to do time-resolved microfluidic SAXS using the normal beamline optics making these experiments much easier to perform and schedule. Microbeam experiments with our compound refractive lens (CRL) optics will benefit from much greater flux densities and smaller focal spots (< 2 x 2 µm with the 1.8 m focal length CRL, < 0.5 x 0.5 µm with the -0.05 m focal length CRL) enabling faster and higher spatial resolution micro-diffraction experiments and new possibilities for SAXS with microfluidic mixers.

BioCAT user program during the shutdown

The APS plans to shut down on April 17, 2023 and restart operations at the beginning of April, 2024. There will be no user access to the APS for this “Dark Period”. BioCAT staff will use this period to do refurbishments and improvements to Beamline 18ID. We have also made arrangements with beamlines at the SSRL, the ALS, and MacCHESS to run part of our user program on their beamlines during this dark period. Users will be able to apply for BioCAT supported time at these facilities using the normal proposal mechanisms at these facilities. In order to reduce the burdens of staff at these other beamlines, BioCAT scientists will help coordinate and plan these experiments, and help users analyze data as appropriate. BioCAT staff will make multiple trips to these facilities to help do specific kinds of experiments. This will be particularly important for muscle diffraction experiments as well as complex SAXS experiments. We also expect to run some time-resolved SAXS experiments at the LIXS beamline at NSLS II.

More details on our specific plans for the dark period:

In March 2022 BioCAT had a virtual town hall to discuss the APS-U and it’s impact on BioCAT. Videos and slides from that town hall are available here: