Impact on Beamlines

No.
The gains depend strongly on each beamline’s optical layout, photon energy range, and measurement approach. However, undulator beamlines can be grouped into three broad categories that each benefit in distinct ways:

• Beamlines using a secondary source aperture gain more intensity for a given slit size
• Beamlines that directly image the source gain proportionally smaller focal spots without flux loss
• Beamlines that weakly focus or do not focus the beam gain a more coherent, parallel beam.

Relative gains are generally larger at higher photon energies. Benefits are most significant for hard X-ray beamlines, while soft X-ray beamlines already operate near the diffraction limit and will see more moderate improvements in coherent flux, but will get the largest coherent fraction in absolute value.

Yes, though differently from hard X-ray beamlines.
MAX IV is already diffraction-limited in soft X-rays (up to approximately 330 eV with the current emittance). MAX 4^U extends this diffraction-limited performance up to approximately 2 keV, significantly expanding the tender X-ray range and delivering meaningful gains in coherent flux for scattering techniques at soft X-ray beamlines.

Yes.
The MAX 4^U Beamline Readiness Programme will add one (1) new beamline to the 3 GeV storage ring.
Additional ports are available on our 3 GeV storage ring, and MAX 4^U offers motivation to expand with additional beamlines and capabilities that leverage the upgraded source’s brightness and coherence. These developments complement ongoing beamline proposals at various design stages. Two additional beamlines are already in the Technical Design stage. These technical studies are funded in one case through the Wallenberg Initiative Materials Science for Sustainability (WISE) andin the other through Lund University.
More broadly, we aim to continue strengthening and developing our entire beamline portfolio across all our sources, in partnership with the user community.

We will follow an existing process, referred to as Expression of Interest, the details and timeline of which are not available yet. This process will involve gathering beamline proposals from the user community through consultation. Proposals will be reviewed and prioritized with involvement of multiple review committees, leading to a recommendation to the MAX IV board. We expect the process to start during 2026.

All undulator beamlines on the 3 GeV ring can potentially benefit from the emittance reduction provided by MAX 4^U.
Wiggler-based beamlines (Balder and the wide-field imaging mode of TomoWISE) will not gain from the emittance reduction, and will continue to perform at their world-class level.
Beamlines on the 1.5 GeV ring (R1) and Short Pulse Facility (SPF) are unaffected by the upgrade.

• Smaller X-ray source size
• Higher beam parallelism
• Increased coherent flux
• Higher effective brilliance

• Faster measurements
• Smaller beam spots
• Higher spatial resolution
• Improved sensitivity
• Greater phase contrast
• Access to diffraction-limited performance up to ~2 keV

• Nanoprobe/microprobe imaging and scanning
• Coherent diffraction imaging
• Phase contrast tomography
• In-situ / operando studies
• Time-resolved structural biology

The improvements vary by beamline and depend on photon energy and optical design, but broadly fall into three categories of gain: more intensity in a given focused beam size; smaller focused beam spots at unchanged intensity; and higher coherent fraction for coherence-based techniques.
In practice, users will see faster measurements (shorter beamtimes for equivalent data quality), improved spatial resolution (smaller X-ray beams on sample), and access to samples or signals previously too weak or too small to measure reliably.

While source properties will improve, beamline teams are carefully assessing how the upgraded source parameters integrate with existing optics. Any necessary adjustments will be planned and communicated in advance.

No.
No beamline relocations are planned.

Possibly.
MAX 4^U includes a beamline readiness programme to ensure that existing optics and instrumentation can fully exploit the improved source properties. Some upgrades or optimizations may be implemented where beneficial. These will be planned carefully and communicated clearly.

MAX 4U^U includes a beamline readiness programme specifically to ensure that our existing beamline portfolio on our 3 GeV storage ring fully benefits from the upgrade. The objective is to strengthen, not replace, our scientific capabilities.

No.
MAX 4^U does not involve relocating beamlines or changes to their geometry.

For many beamlines, yes. To fully exploit the improved source, X-ray optics must transmit the beam’s brilliance to the sample without degrading its quality. With ultra-low emittance, the X-ray beam quality can become so high that optical imperfections become the limiting factor. Fortunately, driven partly by demand from free-electron laser facilities, the quality of commercially available X-ray mirrors and optics has advanced dramatically in the last decade, and near-perfect optics are now obtainable. As part of the beamline readiness programme, a number of beamlines are expected to upgrade key X-ray optical components.

For many beamlines, upgraded or new detectors will be required to fully realize the benefits of increased flux density and higher data rates. Detector technology has evolved rapidly: newer gain-switching and integrating detectors can handle high flux while maintaining single-photon sensitivity, with frame rates of up to several hundred kilohertz and multi-megapixel arrays. We anticipate this technology will continue to advance rapidly, so we will remain focused on benchmarking the most suitable detector for our beamline capabilities once MAX 4^U is completed.

Possibly, for some beamlines. New undulator technologies in combination with the lower emittance can further improve performance, particularly at higher photon energies. For example, TomoWISE will use a shorter-period cryocooled permanent undulator to access high flux up to 45 keV. Similar devices would significantly increase the usable energy ranges of other hard X-ray beamlines. This will be evaluated in the beamline readiness programme.

The stability of our beamlines and accelerator should remain unchanged.