Run 22 Regular Proposals

Call for Proposals for period: August 2023 – March 2024 (Run 22)
Linac Coherent Light Source - SLAC National Accelerator Laboratory

Deadline: 4:00 p.m. Pacific Standard Time (PST) 28 February 2023

We are pleased to announce the call for LCLS Proposals for Run 22. This Run offers the first user experiments using the beam from the new LCLS-II superconducting high repetition rate accelerator and the initial set of new soft x-ray instruments. It also offers a continuation of the existing hard X-ray instruments, but now with dedicated use of the LCLS copper linac accelerator.

For this Run, the superconducting accelerator is expected to be operated up to 33 kHz. Detailed performance parameters will be subject to lessons learned during commissioning over the next few months, and so proposals should be adaptable to a range of likely performance levels. The existing copper accelerator will continue to operate up to 120 Hz for the hard X-ray instruments.

The hard X-ray undulator will be served by the copper accelerator, providing vertical polarization and up to 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 (XPP, XCS, MFX, CXI & MEC).

The soft X-ray undulator will primarily be served by the superconducting accelerator, providing beam to the soft X-ray instruments (TMO, ChemRIXS and qRIXS).

User proposals are sought for 2 of the soft instruments and all the hard X-ray instruments, as described below. For the soft X-ray instruments, an Early Science program is planned as described in the next section.

User proposals for the soft x-ray instruments (TMO & ChemRIXS) using LCLS-II superconducting beam.

Following technical commissioning in Run 21, a period of ‘Early Science’ on each of these instruments will extend into Run 22. Letters of intent were gathered as part of the LCLS Run 21 call and the Early Science program to be executed will flow from these letters of intent. Participation in the Early Science program by the community is still open, and interest can be directed to the following individuals.

After the period of early science, TMO and ChemRIXS will be available for user proposals submitted as part of this call. The new instruments will offer a set of capabilities described below.

The TXI instrument will be commissioned starting in the second half of Run 22. The commissioning will initially focus on tender X-ray spectroscopy capabilities in liquid jets. LCLS will host a workshop in the April-May timeframe focused on an Early Science program exploiting these capabilities. Interest in participation in the workshop and the TXI Early Science Program should be directed to the LCLS Chemical Science Dept. Head Thomas Wolf (


The Time-resolved Atomic, Molecular and Optical Science instrument (TMO) is optimized for studying the dynamics of isolated quantum systems using charged particle spectroscopy, pump/probe methodologies, and/or nonlinear x-ray interactions. Following the technical commissioning and Early Science phases, the TMO instrument will be made available for User experiments in Run 22, providing the first opportunity to make use of the new superconducting LCLS-II accelerator. Run 22 proposals are expected to make use of the capabilities available at the first interaction point of the TMO instrument. We will offer two standard configurations for Run 22, the first configuration features the magnetic bottle electron time-of-flight spectrometer (MBES). The second configuration features the energy- and angle- resolving spectrometer (MRCO). In either configuration, the TMO instrument is capable of performing pump/probe measurements making use of either the newly commissioned, high-repetition rate (33 kHz) OPCPA laser system, or x-ray pulse pairs produced directly by the FEL. Contact Instrument Lead James Cryan ( with any questions.


Anticipating a successful technical commissioning and Early Science phase (currently scheduled for the second half of Run 21), the chemRIXS instrument will be made available for general users proposals using the high repetition rate LCLS-II beam in Run 22. ChemRIXS will make use of the existing instrumentation in combination with a new OPCPA laser system and will focus on transient X-ray absorption (in total and partial fluorescence yield) and/or RIXS spectroscopy experiments in liquid jets. For more information please check our website and/or contact: Instrument Lead Georgi Dakovski ( or Kristjan Kunnus ( with any questions.


During Run 22, the qRIXS instrument is expected to undergo full technical commissioning and an Early Science program, which is open to participation from the user community. The qRIXS instrument is designed to support a wide variety of experimental techniques, such as transient x-ray absorption, diffraction, reflectivity and RIXS. We anticipate that qRIXS will be made available for general user proposals using high repetition rate X-rays in the subsequent Run 23 period. For more information please check our website and/or contact: Instrument Lead Georgi Dakovski ( with any questions.

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

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

Proposal Types Available

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 14 2023.

Standard Configurations: For Run 22, 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. Standard Configurations 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.

Data Collection proposals are encouraged, where a single shift should be sufficient to produce or complete a full data set suitable for publication using a suitable Standard Configuration. Data Collection proposals should be submitted as regular proposals and clearly marked as Data Collection in the title. The proposals can be shorter in length at the discretion of the PI. Rapid Access proposals are welcomed at any time during the Run cycle, although such access is highly constrained, dependent on the availability of the requested configuration.

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. Contact Chris Kupitz ( for additional information and guidance about available setups.

Protein Crystal Screening (PCS) proposals will be considered for Run 22. A separate call for PCS proposals will be issued with a planned submission deadline in March 2023. For more information, please contact Chris Kupitz (

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 Instrument Contacts:

LCLS Scientific Department Head Contacts:

Submitting LCLS Proposals

The Linac Coherent Light Source (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 (listed above) to discuss technical capabilities and proposed experiments. 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. Participation in the Virtual Town Hall is also encouraged.

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 User Portal

Read the proposal preparation guidelines, along with information on the available Standard Configurations, and the proposal review process prior to writing your proposal. A Proposal Template has been created to provide guidance on the format and structure of proposal submissions.

SSRL Beam Time tied to LCLS Experiments

For some LCLS proposals, the science case can be significantly enhanced by having access to SSRL beamtime in addition to proposed LCLS time. SLAC will consider a limited number of proposals that make a strong scientific case for beamtime 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 ( Scheduling of time across facilities is complicated and availability depends strongly on which of the SSRL beamlines is requested.

Other Access Modes to LCLS

Science Campaigns. No new Science Campaigns are sought for Run 22.

Timeline for Run 22

Run Cycle Proposal Type Proposal Submission Deadline Run Cycle Begins Run Cycle Ends
LCLS 22 Regular User Proposal February 28, 2023 4 pm Pacific Aug 2023 Mar 2024
LCLS 22 Protein Crystal Screening (PCS) March 28, 2023 4 pm Pacific Aug 2023 Mar 2024

A Virtual LCLS “Town Hall” User Meeting will be held at 8:00am Pacific Daylight Time on February 14 2023. 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. Information on how to connect will be sent separately.