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

FAQs about the APS Upgrade

After 25 years of leading scientific discoveries, Argonne’s Advanced Photon Source (APS) will undergo an extensive upgrade that will keep the light source facility at the forefront of global X-ray science for the next quarter century and beyond. During the year-long installation period of the new electron storage ring, all operations, including scientific experiments, will pause.

We created a matrix of beamlines at other U.S. Department of Energy (DOE) light sources to help APS Users identify comparable beamline options for their research during the installation period.

Below is a series of Frequently Asked Questions (FAQ) about the APS Upgrade and the future of the facility, as recorded during Q&A sessions with the APS User community May 2021, November 2021 and May 2022. The latest information about the APS Upgrade is available at the project website.


Why is the upgrade necessary? (May 2021)

As research becomes more diverse and competitive, scientists need the best tools. The X-rays generated at the upgraded APS will be up to 500 times brighter than current capabilities. The resulting images will be sharper with higher resolution and generated at a fraction of the speed, revealing discoveries and data we have not even considered.

When will the installation period for the APS upgrade begin? (May 2021, May 2022)

The end of APS User Operations will be April 17, 2023.  The shutdown of the accelerator and start of the removal and installation period will be April 24, 2023, after a brief set of technical checks of the new Injection Extraction Timing System are conducted. 

How can the APS help me find other facilities where I can conduct experiments during the APS’ year-long shutdown? (Nov. 2021)

Use of other DOE facilities requires submission of a proposal to the appropriate light source user facility. Other DOE facilities will not set aside time for displaced APS users. We have developed a matrix of beamlines detailing and comparing APS capabilities with capabilities elsewhere in the DOE complex. Although beamlines at various facilities are not exactly the same, the matrix should help you identify roughly equivalent capabilities at other facilities.

When will the installation period for the APS upgrade be complete? (May 2021, May 2022)

The installation period will take 12 months. The upgraded APS will begin initial operations in April 2024. The shutdown period will remain at one year. Getting back online as fast and as safely as possible is a priority not just for the project, but for the photon science community as a whole.

Is there any risk the installation period will last longer than one year? (May 2021)

There are always risks, but the project team continues to mitigate them as they arise. Most equipment will be assembled and ready at the start of the installation period, and those whose deliveries extend beyond the start of the installation period are well understood. This includes all the large sub-assemblies that make up the new storage ring – some of them weighing up to 30 tons.  By doing the prep work and practicing on those pieces before the installation period starts, we have confidence we can meet the 12-month installation schedule.

What if there is another delay? (May 2021)

While there is always a risk of another delay, we believe the April 2023 start date is achievable. In August 2022 we charged an external panel with reviewing our plans, and they were found to be solid.  Of course, minimizing disruption to the user community has been a core deliverable of the APS Upgrade from day one. If another delay proves necessary, we will notify users. The APS Upgrade web page will include regular updates and schedules to keep all stakeholders regularly informed.

Will the APS continue operating until the April 2023 shutdown date? (May 2021)

Yes. There will be an operations run in the early months (January to April) of 2023.

When will the beamline I use shut down/come back online? (May 2021)

This varies by beamline. Most of the beamlines will continue to operate up until the storage ring installation period begins, and be recommissioned starting shortly after the installation period ends. This could mean within a month or two of the upgraded APS returning to operations. However, for feature beamlines and major enhancements, we cannot accomplish all work during the shutdown, so we will need to stagger the work. Several beamlines will shut down early.

How much does the upgrade cost? (May 2021)

The upgrade will cost $815 million and re-uses more than $1.5 billion in existing infrastructure. 

Are there any new updates to the beamline construction schedule? (Nov. 2021)

Of the 68 existing beamlines at the APS, 41 will need construction related to the upgrade. Beamlines not particularly affected by the upgrade should come back quickly; feature beamlines, if they are brand new, will likely take at least six months for commissioning before we transition to the full user program.

We will confirm announcements about beamline access approximately one year prior by email and in townhall sessions for each user community.  The most current information about the APS Upgrade can be found here.

What is the expected time to ramp up to 100 milliamps after the upgrade? 200 milliamps? (Nov. 2021)

When the one-year shutdown ends, we conservatively expect to be at 25 milliamps. We expect to then increase that current in stages to 100, 150, and ultimately 200 milliamps in the following run periods. We will take into account the possibility of issues with vacuum conditioning, feedback systems, beamlines and the storage ring itself. 

How long will it take the upgraded beam to ramp up to full strength? (May 2021)

We are planning for the first run period in April 2024 to provide nominally 50% of beam for user operations. Modeling our expectations on the European Synchrotron Radiation Facility (ESRF), we believe we can ramp up quickly to stable operations. If there are no significant hardware failures, we expect to be at 100 milliamps within six months. We estimate the upgraded APS will be at 200 milliamps roughly 16 months after the installation period ends.  Note that the conversion from electron beam current to X-ray beam properties will be different in the upgraded APS era as compared to now. Users should check with beamline scientists about what the future X-ray properties will be at each beamline. 

Will chilled water, compressed air, experimental hutches, etc. still be available during the installation? (May 2021)

For the most part, yes. We have already completed several upgrades with a focus on attaining a higher order of cleanliness, including the addition of redundant cooling towers. Upgrades to air compressors, the liquid nitrogen distribution system, and a Module C liquid nitrogen storage tank for Sectors 18-27 replacement are also complete, so we do not anticipate a major shutdown of utilities. 

Will there be constraints regarding accessing the experiment hall floor during the shutdown, and how do we coordinate that with the CAT Beamlines? (May 2021)

Some isolation will need to happen during the installation and commissioning period. We are currently working out the plan for controlling access during this period and will communicate and coordinate that with users in the future.


Why will the upgraded APS use a horizontal injection scheme instead of vertical one, and does this have an impact on operating modes (e.g., 48-bunch mode vs. 324-bunch mode)? (May 2021)

The decision to implement a horizontal injection scheme was not based on the impact on operating modes. The decision to go from vertical to horizontal was made due to lingering concerns about the technical systems associated with the septum magnets, as well as the vacuum quality in the stored beam channel. We did not have the same concerns about the horizontal injection scheme so we chose the more reliable, less risky implementation.

Will the upgrade reduce beam loss? (Nov. 2021)

We expect more beam loss initially as we learn how to operate the new machinery and keep the equipment protected. The radiofrequency (RF) system in place at the APS is not being replaced as part of the upgrade, and we will continue using it for the next seven to eight years until the current klystrons are replaced with solid state amplifiers. However, new systems, power supplies, and magnets should result in a decline in beam loss associated with aging or obsolescent equipment. The APS is highly reliable, but we are always working to decrease beam loss and maximize availability of user operations.

What is the frequency of re-injection and what effect will that have on the beam in both 48-bunch and 324-bunch mode? (Nov. 2021)

The APS Upgrade will have two modes of operation: 324-bunches (low charge per bunch) and 48-bunches (high charge per bunch). To maintain 1% average current constancy, there will need to be different intervals between injection periods, depending on what mode you’re in. For example, for 324-bunch, injections will occur once every few seconds (less than 10 seconds) depending on lifetime to maintain constancy. For 48-bunch, the period between injections is longer (more like 30 seconds).

The APS-U swap-out injection scheme will extract a stored bunch and inject a new bunch on the central beam orbit. This will be quite different that the current topoff injection scheme where we add charge to existing bunches with off-axis injection. In the swap-out scheme, the injected bunch will have a larger emittance than the equilibrium emittance of the other stored bunches and thus have a minor impact on the total brightness for the few milliseconds after injection. We have estimated the impact to be < 2% during this period. The impact could be higher if we are not able to produce the necessary charge in the injector for each injection cycle. We are working to upgrade the injectors to make sure that we are able to provide the necessary charge for each injection. We are also planning to provide the appropriate timing signals to each beam line when each injection occurs.


What will be the duration of a single x-ray bunch after the APS Upgrade (in 324-bunch and in 48-bunch)? (Nov. 2021)

In 48-bunch mode, the bunch duration (rms) will be 104 picoseconds, with bunch spacing at 76.7 nanoseconds. In 324-bunch mode, the bunch duration (rms) will be 88 picoseconds with bunch spacing at 11.4 nanoseconds.

Is there a plan for how time will be divided between the 324-bunch and 48-bunch modes after the upgrade, both for the period immediately after the beamline is turned back on as well as the long-term vision? (Nov. 2021)

The APS-U will be commissioned in the “brightness” 324-bunch mode. Although we will be able to deliver “timing” 48-bunch mode following APS-U commissioning in a lower total average current, we will be continuing studies and adding hardware upgrades towards achieving 200 mA in the “timing” mode. The time scale for this development will be discussed following the APS-U commissioning. The long-term split is an operational choice and has not yet been determined.

Is hybrid single mode totally out of the question? Is there any way to implement it? (Nov. 2021)

We have no plans to pursue hybrid single mode because of the requirement for symmetric beam fill patterns. We are introducing a bunch-lengthening system with a higher harmonic RF system that stretches the bunch to make it longer than it would normally be. This reduces the charge density, which increases the Touschek lifetime (the dominant effect). To work properly, a symmetric fill pattern is required. Once the APS-U is commissioned, we may study the possibility of symmetric hybrid patterns, which are possible in principle. 


How will the upgrade benefit my research? (May 2021)

There is no single answer to this question because so many different types of measurements happen on the APS and will continue to happen on the APS after the upgrade. However, we know there will be immediate large benefits for experiments reliant on sub-micron X-ray beams, imaging (phase contrast), and coherence exploitation. We anticipate higher resolution lensless imaging and faster dynamics, and we know there will be a significant benefit for high-energy experiments. Superconducting undulators provide higher flux and will extend coherence techniques to higher energies.

What areas of science might not benefit from the upgrade? What will you be doing for those proposals? (May 2021)

All areas will benefit from the upgrade in some capacity and all proposals will continue to be judged on their scientific merit. 

For those who use softer X-rays for our research, how will this upgrade help us? (May 2021)

The APS is optimized to produce higher energy X-rays, but all beamlines will benefit from the increased current and better machine performance.  Experiments such as X-ray absorption spectroscopy that use larger beam sizes on bending magnets will gain by a factor of two from the higher current. As the APS has aged, critical systems have experienced challenges expected with aging technologies. The upgraded APS will replace these systems, thus providing improvements in beam stability and reliability.

How are you going to keep up with all the data collected after the upgrade? (May 2021)

The APS team is working with our colleagues in Argonne’s computing divisions to develop data pipelines and analysis now, with the goal of having them ready for implementation when the upgraded APS comes online. Data volume is the biggest issue on the feature beamlines, since they will have newer faster, larger detectors. Other beamlines should work just as well as they did before, but strategies for their data analysis will also continue to evolve.

Will the coherence of the beam make data analysis more difficult, if I am interested in averaging? (May 2021)

It should not be difficult to get time/special averaged measurements that do not exploit the beam coherence. However, you will have to work hard to preserve coherence.


How can I access the APS on site as a user? (May 2021)

The APS is open to on-site users.   Site access can only be granted to users identified as onsite users on approved Experiment Safety Assessment Forms (ESAFs), or if a Gate Pass is requested and processed by the User Program Office.  Visit the My APS Portal to request a Gate Pass or email  Users must follow COVID controls at the time of their visit. 

Will user institutions need new user agreements? (May 2021)

No. Existing user agreements will stay in place and Argonne will not need to renegotiate with every institution. 

When is the last call for APS proposals before the installation period? (May 2021)

The call for proposals for the 2023-1 cycle (the last run period using the APS) will be October 2022. 

Are you planning an early scientific commissioning period? (May 2021)

This varies by beamline. Most of the beamlines will shut down when the installation period starts and come back shortly after that period ends. We will use the normal general user program call to schedule beam time on untouched beamlines or those beamlines with modest upgrades (meaning ones that only need roughly one month of commissioning).  On the APS feature beamlines, we are developing a separate review process to identify key high-impact first experiments that will be scheduled during an early scientific commissioning period before the beamline fully opens to general users.

How will access be determined to upgraded beamlines? Regular general user proposals? Will there be early science partnerships or access during commissioning time? How will we apply for this time? (May 2022)

We are still discussing our approach but will likely have a special call for first experiments or early science proposals on feature beamlines to participate in scientific commissioning before we make the beamlines available to the general user program. That call will tentatively be November 2023. Special review committees including current review committees plus subject matter experts would evaluate proposals and get two to three groups per feature beamline involved in scientific commissioning. After technical commissioning, scientific experiments could begin.

We are also encouraging workshops in fall 2022 or early spring 2023 to discuss feature beamline experiments, formulate ideas and form groups that would put forth the best proposals.

On the non-feature beamlines, committees will look for experiments that will produce high impact science early but also make particularly effective use of new capabilities of the source. These will likely follow the precedent of our traditional general user program.

Will partner user proposals be considered or encouraged on upgraded beamlines to help develop new capabilities? (May 2022)

Not at the beginning. Until we know the APS is working and ready for general user proposals, the emphasis will be to get the upgraded APS up and running with its new capabilities. After that, we can start considering partner/user proposals.

When is the first call for proposals to use the upgraded APS? (May 2021)

All general user (and other) proposals will expire when the installation period begins. We anticipate that there will be a new proposal call for general user operations during the shutdown. The APS User Office will provide a calendar of general user dates of interest for the post-upgrade runs when that information is known.

Can I find comparable beamlines at other light sources during the year-long upgrade installation period?

Ideally, yes. There is no time specifically set aside at the other DOE light sources for APS general users in search of beam time, but we have developed a matrix of beamlines at other storage rings to help users identify other facilities that are comparable to what they could use at APS.  The installation period will be complete and the upgraded facility will be operational before the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory is scheduled to shut down for its own upgrade, which is scheduled for 2025.

Will the APS help me apply for beam lines at the other light source? (May 2022)

Unfortunately, no. Users must submit proposals directly to other light sources. Many facilities are aware of our schedule and they may be ready to help users who otherwise wouldn’t use their facilities.

Wouldn’t it be helpful to recommend European light sources? Some are closer to APS in feature capabilities? (May 2022)

Our matrix indicates overlap at light sources within BES. However, users are welcome to look at other light sources. You may find more exact capabilities by looking further afield.

Would it make sense to have special committees for the enhanced beamlines, just as for the feature beamlines? (May 2022)

We are considering that possibility. We want to find the right balance of bringing the beamlines back after significant rebuilding and getting the most science out of the new machine. Deliveries from vendors and construction schedule are factors. The Scientific Advisory Committee has established these questions as a focus of its fall meeting.  

With ESRF and Max IV running, are there any changes of expectations to beams or experiment performance, post upgrade, to learn from their operations? (May 2022)

We have monitored the commissioning of both light sources in real time and both were impressive. We will try to meet same bar but vacuum conditioning, COVID-19 interruptions and supply chain issues make our installation different. Regardless, there are opportunities to lean from their experiences, and we hope to do more of it.

Can I borrow equipment for experiments at other light sources? (May 2021)

No. This would be very difficult to do logistically, and the risk of equipment breakage is too high.

When the upgraded APS begins operating in 2024, will its improved brightness and data collection speed result in an increase in the number of successful proposals? (May 2021)

Typically, the number of proposals that can run is not limited by brightness or flux, but by staffing levels. We are always exploring ways to gain efficiencies and accommodate more users and measurements. The upgraded APS will generate larger, more complex data sets, but will not necessarily lead to a greater number of successful proposals. 

Will remote access to beamlines still be available once the upgraded APS is back up and running? (May 2021)

Yes, the upgraded APS will still allow for remote access on beamlines capable of supporting remote access. During the COVID-19 pandemic, we have worked hard to implement and enhance remote data-taking capabilities, and we will continue to do so when the upgraded APS is online. However, onsite user presence remains critical in order for users to optimally use the upgraded APS’ capabilities and beam time. This is particularly true for complex in situ/operando conditions/reaction studies. The feedback loop between users and beamline scientists in extracting the maximum potential from the measurements is difficult to realize with fully remote users. 

Will requesting remote access hurt or help my chances of securing beam time? (May 2021)

Requesting remote access will neither hurt nor help users’ chances of securing beam time. However, due to variations in expertise and/or bandwidth, there are limits as to what the beamline staff can do for users. Scope and scale of measurements could be affected.

Will the beamline I use move to somewhere else in the upgraded APS? (May 2021)

Minimizing the number of relocations was a key part of the beamline construction plan. Due to the construction of the Long Beamline Building and other factors, some relocations are necessary. The beamlines for 20-ID, 33-ID, USAXS, and Bionanoprobe will move. Other programs will close or evolve, like the soft X-ray XCMD program at 4-ID-C and the structural biology program currently at 19-ID. 


What if I have more questions not answered here?

Users with questions regarding access, registration, legal agreements, and proposals should contact the APS Users Office at Other questions can be submitted via Please check this FAQ page for updates.