LCLS Run 25 Call for Proposals

LCLS Call for Proposals for period: September 2025 – February 2026 (Run 25 Hard X-rays and Soft X-rays)

Submission Deadline: 04 March 2025 (4:00 PM Pacific Time)

We are pleased to announce the call for LCLS Proposals for Run 25. This Run will offer capabilities on the soft X-ray instruments using the beam from the new LCLS-II superconducting high repetition rate accelerator. It also offers a continuation of the existing hard X-ray instruments, with dedicated use of the LCLS copper accelerator.

For Run 25, the superconducting accelerator is expected to be operated up to a nominal 33 kHz. Detailed performance parameters will be subject to lessons learned during commissioning, and so proposals should be adaptable to a range of likely performance levels. Close coordination with the relevant instrument scientist teams is strongly advised in the preparation of your proposals.

The soft X-ray undulator will be served by the superconducting accelerator, providing beam to three soft X-ray instruments for user proposals (TMO, chemRIXS and qRIXS). The second TMO endstation (DREAM) will also be available.

The copper accelerator will continue to operate up to 120 Hz for the hard X-ray instruments, providing vertical polarization and up to 20-25 keV X-rays in the fundamental, as well as rapid tuning / scanning capability using the variable gap system. This undulator will provide beam to the suite of hard X-ray instruments (XCS, MFX, CXI & MEC). In Run 25, the XPP instrument will not be available as it is undergoing a rebuild for the LCLS-II-HE upgrade. We expect most of the scientific capabilities typically supported at XPP to be feasible at the other hard X-ray instruments, in particular XCS. Please contact LCLS Instrument Scientists to discuss options for your proposal.

Register and submit your proposals through the new Universal Proposal System (UPS). 

For information about this new system and explain the features and functionality of this new tool please visit the link below:

Universal Proposal System Information

A Virtual LCLS “Town Hall” User Meeting to discuss Run 25 will be held at 9:00 am Pacific Daylight Time on February 6, 2025.

User proposals for the soft X-ray instruments (TMO, chemRIXS and qRIXS) using LCLS-II superconducting beam.

TMO:
The Time-resolved Atomic, Molecular and Optical Science instrument (TMO) was developed to study the dynamics of isolated quantum systems using charged particle spectroscopy, pump/probe methodologies, and/or nonlinear X-ray interactions. The TMO instrument will continue to be available for User experiments in Run 25 providing the opportunity to make use of the superconducting LCLS-II accelerator. Run 25 proposals are expected to make use of the capabilities available at either interaction point. At the first interaction point (IP1) we will offer multiple standard configurations for Run 25: the first configuration features the magnetic bottle electron time-of-flight spectrometer (MBES), the second configuration features the energy- and angle- resolving electron spectrometer (MRCO). For either configuration, the high power OPCPA laser system can be operated up to 33 kHz. At the second interaction point (IP2) we will offer a standard configuration with the new reaction microscope (DREAM) endstation. This standard configuration will feature ion and electron detection capabilities. The DREAM endstation is coupled to a high repetition rate Yb-based laser system (33 kHz nominal, operation up to 100 kHz can be considered). For more information please check our website and/or contact Instrument Lead James Cryan (jcryan@slac.stanford.edu) with any questions.

chemRIXS:
ChemRIXS is a dedicated instrument to study condensed phase chemistry with pump-probe spectroscopy using high repetition rate soft X-rays. For Run 25 chemRIXS will be available for general user proposal using the high repetition rate LCLS-II beam at the nominal 33 kHz repetition rate. The liquid standard configuration of chemRIXS is optimized for pump-probe RIXS and XAS experiments using liquid jets in combination with the OPCPA laser system with 800 nm fundamental wavelength. New high-throughput SVLS spectrometer with nominal 2000 resolving power will be available for RIXS and PFY-XAS measurements. Simultaneously with the spectrometer, upgraded detectors for transmission-XAS and APDs for total fluorescence yield XAS detection will be offered. For more information please check our website and/or contact Instrument Lead Kristjan Kunnus (kristjan@slac.stanford.edu) with any questions.

qRIXS:
qRIXS is a dedicated instrument designed to investigate correlated-electron condensed matter systems using a wide variety of time-resolved spectroscopy methods.  It will be made available for general user proposals in the Run 25 call for proposals at the anticipated 33kHz repetition rate. Experiments requiring >33 kHz can be considered and should be discussed with LCLS Instrument Scientists before submission. The qRIXS instrument supports a wide variety of experimental techniques, such as time-resolved resonant inelastic x-ray scattering, transient X-ray absorption, diffraction, reflectivity.  For more information please check our website and/or contact Instrument Lead Georgi Dakovski (dakovski@slac.stanford.edu) with any questions.

User proposals for the Hard X-ray Instruments using the 120 Hz accelerator

The hard X-ray instruments of LCLS (XCS, MFX, CXI & MEC) will be available using the 120 Hz accelerator as in previous LCLS runs.

Proposals that make use of the Standard Configurations available on each of the Hard X-ray Instruments are highly encouraged, including short proposals that can make use of a more limited amount of beamtime with higher likelihood of scientific success using those standard configurations.

LCLS Hard X-ray Instrument Contacts:

Proposal Types Available (for all instruments)

(1) General User Proposals

A Proposal Template has been created to provide guidance on the format and structure of submissions. Users are strongly encouraged to follow this guidance, to help ensure that appropriate information is supplied to the Proposal Review Panel (PRP). This template along with updated proposal preparation guidelines will also be discussed during the Virtual Town Hall on February 6, 2025.

Proposals that can be scientifically successful using fewer than the typical 5 shifts are acceptable if the scientific needs are consistent with a shorter experiment. Proposers are asked to make it clear in their proposals that level of risk and scientific ambition is consistent with the number of shifts requested.

Standard Configurations:

For Run 25, LCLS will continue to emphasize the use of Standard Configurations, where a target of 50% or more of the beamtime is expected to be awarded to experiments utilizing the many configurations available. These provide a defined platform for running many similar experiments efficiently, leading to more users and experiments being allocated beam time. Proposals that make use of the Standard Configurations available are highly encouraged, including shorter experiments that can make use of a more limited amount of beamtime with higher likelihood of scientific success using a standard configuration.

Standard Configuration proposals require the inclusion of a parameter table, which can be found on the instrument-specific website. Users are strongly encouraged to contact the relevant instrument scientists to discuss and plan their proposals of any kind, but especially those that use (or could be adapted to use) Standard Configurations.

The Hard X-ray Standard Configurations continue to evolve to meet the needs of the scientific community and some have been updated. Please note the following additions:

  • XCS: A newly developed spectrometer based on polycapillary optics (polyXAS) is now available for measuring X-ray absorption spectra of 3d and 5d transition metals from low-concentration solution-phase samples (well below 1 mM). This spectrometer is compatible with the liquid jet endstation (LJE) standard configuration at the X-ray Correlation Spectroscopy (XCS). For more information about this instrument and its capabilities please contact Roberto Alonso-Mori (robertoa@slac.stanford.edu).

  • MEC: MEC will be accepting rapid access proposals (see below) for laser-only VISAR shots.

    IFE Science: Proposals to the MEC science area that address inertial fusion energy (IFE) priority research opportunities (PROs) are strongly encouraged. There is a goal of scheduling up to 50% of MEC science experiments in the IFE area, consistent with recent guidance from DOE. Such proposals should be clearly indicated as addressing IFE, such as by identifying the relevant PROs from the 2022 IFE Basic Research Needs (BRN) Workshop Report. These proposals will be reviewed by a sub-panel of the MEC PRP consisting of experts in IFE science in collaboration with LaserNetUS, alongside a sub panel for general MEC science. For more information on any aspect of MEC, please contact Instrument Lead Eric Galtier (egaltier@slac.stanford.edu) with any questions.

(2) Dataset Collection and Screening (DC&S) proposals:

LCLS offers a short proposal mechanism for experiments that can make use of a short amount of beam time (up to one or two shifts) using a frequently deployed configuration to collect a dataset or screen samples in preparation for a regular LCLS proposal. DC&S proposals need to make use of a configuration already in place for regular LCLS experiments and they are therefore scheduled “as opportunity arises”. This access mechanism is tailored to:

  • Experiments where one or two shifts would be sufficient to complete an existing or collect a full dataset, suitable for publication. As part of the proposal, your science case should justify why your experiment can be accomplished in 1 - 2 shifts. If applicable, it should reference the previously reviewed proposal or beamtime.
  • New user groups or projects that need half a shift (6 hours) to gain experience or screen samples in preparation for submitting a full proposal.

Note that the DC&S proposal mechanism unifies and replaces the Protein Crystal Screening (PCS) and Data Set Collection (DSC) programs that were offered in previous runs. DC&S proposals will be reviewed and prioritized independently from regular proposals to allow like-for-like comparison.

Data Collection and Screening proposals should make use of one of the following templates:

Beam time availability for this type of proposal is contingent on scheduling constraints and experiments are required to make use of one of the following frequently deployed configurations:

  • XCS: horizontal liquid jet for solution scattering and hard X-ray spectroscopy
  • MFX: horizontal liquid jet in helium/air for solution scattering or crystallography (may be combined with X-ray emission spectroscopy and/or pump laser capabilities, dependent on availability)
  • MFX: droplet-on-tape sample delivery system for crystallography (may be combined with X-ray emission spectroscopy and/or pump laser capabilities, dependent on availability)
  • MFX: fixed targets in air
  • CXI: liquid jet in the micronfocus chamber (no pump laser)
  • CXI: gas phase scattering in the micronfocus chamber with 200 nm or 266 nm pump laser (only available for dataset collection experiments, not sample screening)
  • MEC: X-ray diffraction with uniaxial compression
  • MEC: X-ray imaging with long pulse laser side irradiation

Please contact Sandra Mous (smous@slac.stanford.edu) for additional information and guidance on DC&S proposals.

(3) Rapid Access proposals

Rapid Access proposals are welcome at any time during the run cycle, although such access is constrained and dependent on the requested configuration's availability. Rapid Access proposals should typically target Standard Configurations and must articulate why urgent access is needed. Access has typically been aimed at structural biology studies (e.g. COVID research) but will be considered for any subject area with an appropriate case, subject to facility availability.

Modes of Beam Operation:

For up-to-date information on LCLS performance, please contact the respective instrument scientist listed above, and see the Machine FAQ and the Machine Parameters table, which includes a Multi-Color Pulse Mode Table.

LCLS Scientific Department Head Contacts

For general inquiries when preparing proposals:

Submitting LCLS Proposals

LCLS encourages scientists from diverse fields and backgrounds to propose experiments utilizing the facility’s capabilities. New users are particularly welcome. Users are encouraged to review the LCLS instrument descriptions and contact LCLS staff to discuss technical capabilities and proposed experiments (see Scientific Department Head and Lead Instrument Scientist contacts above). These staff will provide advice on how to translate your scientific ideas into an LCLS experiment, and can help introduce new users to potential partner user groups if desired. Communication with the LCLS team is strongly encouraged to help maximize your chances of success.

Access to LCLS is open to the international community, with selection based on scientific merit. There is no charge to conduct experiments at LCLS, and the facility is able to help with the costs of performing experiments (e.g. consumables). However, users are responsible for their own travel expenses.

Register as a user and submit LCLS proposals through the Universal Proposal System (UPS)

Registration in UPS is required for all members of the proposal team (Principal Investigators and Co-Proposers), and is quick and easy using your existing ORCiD credentials.

Read the proposal preparation guidelines, along with information on new standard configurations, and the proposal review process prior to writing your proposal.

Please pay particular attention to the updated LCLS Proposal Evaluation Criteria (notably in the area of: Originality/Degree of Innovation) and ensure that your proposal makes the strongest case for evaluation following these criteria.

SSRL Beam Time tied to LCLS Experiments

For some LCLS proposals, the science case can be significantly enhanced by having access to SSRL beam time in addition to proposed LCLS time. SLAC will consider a limited number of proposals that make a strong scientific case for beam time access to SSRL. These proposals should indicate how much time is requested, when the time would be needed relative to the LCLS time, as well as which SSRL beamline would be needed. If users have questions about which SSRL beamlines would be appropriate for the proposed scientific goals, please contact Piero Pianetta (pianetta@slac.stanford.edu). Scheduling of time across facilities is complicated and availability depends strongly on which of the SSRL beamlines is requested.

Timeline for Run 25

Run CycleSubmission DeadlineCycle BeginsCycle Ends
Run 25March 4, 2025
4:00 PM (Pacific Time)		September 2025February 2026

A Virtual LCLS “Town Hall” User Meeting will be held at 9:00am Pacific Daylight Time on February 6, 2025.

This webcast meeting will be held to inform potential users about developments at LCLS before the upcoming LCLS proposal deadline. LCLS staff will inform the community about the latest capabilities and will be available for Q&A.