Run 19 Regular Proposals

Latest Proposal Schedule

Mode of Access Run Cycle Proposal Call Status Deadline Cycle Begins Cycle Ends
Scientific Campaign Proposal LCLS 20 Accepting Letters of Interest 28 May 2021 Jan 2022 Jun 2022
Regular User Proposal LCLS 20 Further details coming soon TBD Jan 2022 Jun 2022
Protein Crystal Screening (PCS) LCLS 19 Submitted Proposals under review 09 Feb 2021 May 2021 Dec 2021
Rapid Access (CXI, MFX) Contact for details Ongoing  
MeV-UED Regular User Proposal UED 3 Experiments Scheduled 14 Dec 2020 May 2021 Sep 2021

  Proposals are submitted through the User Portal.

LCLS call for Regular Proposals for period: April 2021 – October 2021 (Run 19)

Submission Deadline: 28 October 2020 (4pm PDT)

We are pleased to announce the next call for LCLS Proposals as LCLS continues its instrument deployment in conjunction with the LCLS-II upgrade.

For this run, the copper accelerator (capable of up to 120 Hz) will be available with two separate undulator systems and an increasing set of upgraded instruments.

The hard X-ray undulator will provide vertical polarization and up to 25 keV X-rays in the fundamental, as well as rapid tuning/scanning capability using the new variable gap system. This undulator will provide beam to the existing suite of hard X-ray instruments.

The second undulator source will deliver soft X-rays to an early configuration of two instruments being developed for LCLS-II (TMO and ChemRIXS). User proposals should target experiments using up to 120 Hz beam delivery.

In Run 19, LCLS will be commissioning the new qRIXS sample chamber (not complete RIXS spectrometer), adding new capabilities in soft x-ray material science, and is seeking user interest in the formation of a community team to contribute to an ‘early science’ program. qRIXS will then be made available for user proposals in the subsequent Run 20.

Standard Configurations: For Run 19, LCLS will continue to emphasize the use of Standard Configurations for the hard X-ray instruments, 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. The reduced amount of setup and test time results in significantly more users and experiments being allocated beam time. 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.

LCLS encourages "data collection" proposals where a single shift should be sufficient to produce a full data set suitable for publication, using a suitable Standard Configurations.

LCLS also encourages Rapid Access proposals for structural biology at any time during the run cycle.

Experimental stations available to users:

A Virtual LCLS “Town Hall” User Meeting will be held at 8:30am Pacific Daylight Time on October 22 2020.

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.

Modes of Beam Operation:

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

Capabilities Offered for Run 18

Soft X-ray Undulator (SXU): A variable gap undulator system will be used, providing horizontal polarization (same as the previous fixed-gap LCLS undulator) for photon energies from 270 eV to 2000 eV, dependent on instrument choice. A guideline for the expected pulse energy is shown here for soft X-rays, with details dependent on pulse duration and other factors. For more information, please contact Bill Schlotter ( ).

Hard X-ray Undulator (HXU): A variable gap undulator system will be used, providing photon energies up to 25 keV in the fundamental. This undulator will have vertical polarization. This is expected to increase the throughput of most monochromatic experiments but some experimental geometries may need some reconsideration. A guideline for the expected pulse energy is shown here for hard x-rays, with details dependent on pulse duration and other factors. For more information, please contact Bill Schlotter ( ).

Early Science: Immediately following technical commissioning of the qRIXS sample chamber and goniometer, a period of early science will be organized and led by LCLS staff and will include a limited number of expert users. This Early Science program will focus on elastic scattering (i.e. without the emission spectrometer) and is intended to be pilot experiments that bridge between technical commissioning of the instrument and regular user operations (through the PRP Regular Proposal process). If you are interested to participate and contribute to the Early Science program on qRIXS (or for further information) please contact Georgi Dakovski

Repetition Rate: We have the capability to split the delivery of the 120 Hz output of the electron accelerator between the two undulators to allow parallel delivery to soft and hard X-ray instruments. Users should expect operations at a rate below 120 Hz as the standard practice.

Soft X-ray Instruments: Two soft X-ray instruments are available for experiments during Run 19. These are TMO and ChemRIXS which were deployed in Run 18 and are expected to be ready to serve a broad user community. Proposals to TMO and ChemRIXS are greatly encouraged and will be prioritized where possible. Detailed information on each instrument can be found in the linked documents.

Hard X-ray Capabilities and Areas of Emphasis for Run 19: The existing suite of Hard X-ray instruments of LCLS will be on offer for Run 19, with a set of new detectors now available. Please contact the relevant instrument scientists for details on the expected capabilities for each instrument.

In addition to Standard Configurations, LCLS expects to give special attention to hard X-ray proposals making use of the following capabilities.

  • >15 keV Operation: With the new hard X-ray undulator, beam delivery up to 25 keV in the fundamental with pulse energy of up to 1 mJ is expected. Proposals making use of photon energies above 15 keV are encouraged and will be prioritized where possible. For more information, please contact Sebastien Boutet (

Submitting LCLS Proposals

The Linac Coherent Light Source (LCLS) encourages scientists from diverse fields to propose experiments utilizing LCLS's unique capabilities. Access to LCLS is open to the international community. There is no cost to submit proposals or conduct experiments at LCLS. However, users are responsible for their own travel expenses and (in rare cases) for any extraordinary consumables required by the experiment.

Register as a user and submit LCLS proposals through the User Portal

Read the proposal preparation guidelines, along with information on the new Standard Configurations, and the proposal review process prior to writing your proposal. Users are encouraged to review the LCLS instrument descriptions and contact LCLS instrument scientists to discuss technical capabilities and proposed experiments.

Protein Crystal Screening (PCS) Proposals will be included in Run 19. A separate call for PCS proposals will be issued with a planned submission deadline of January 26, 2021. For more information, please contact Mark Hunter (

SSRL Beam Time

For some LCLS proposals, the science case can be significantly enhanced by having access to SSRL beamtime in addition to proposed LCLS time. For this Run 19 Regular Proposal call, 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 - LCLS has introduced a new access channel “Scientific Campaign Proposals” that represents an augmentation of the Regular Proposal process. Science campaigns are a mechanism to support more extensive research “programs” or campaigns, requiring a series of beamtimes, and targeting specific areas of science where there is great potential scientific impact from some unique capabilities of LCLS. The scientific scope and impact of the proposed research should be well above a Regular User Proposal as described above.

A specific call for Science Campaign Proposals in Biology for Run 19 was issued on 15 July 2020, and is separate from this call for Regular User Proposals for Run 19. Scientific Campaign proposals that are not awarded beamtime as a “campaign” will be automatically considered by the Proposal Review Panel for allocation of a single beamtime in Run 19. For further details regarding Campaign Proposals, please see the updated proposal preparation guidelines and proposal review process.

Rapid Access - The LCLS Rapid Access Program enables high-impact experiments on biological structure determination at the CXI and MFX instruments through rolling proposal review and rapid scheduling.  Schedule constraints can impact Rapid Access throughout the LCLS schedule so please visit the details page or contact Mark Hunter ( for additional information and guidance about available setups.