Participation of General Users at the APS

Issued October 8, 2002
Last updated March 16, 2011


The objective of the APS general user program is to provide maximum opportunities for productive use of the APS by qualified researchers through a central APS process for proposal submission, peer review, and beam time allocation.


Beamline: All instrumentation and facilities that extend from the source in the storage ring to an experiment station.

Beam Time Allocation Committees (BACs): Committees that determine which beamline will host each general user proposal and how much time each proposal will receive.

Beam time request form: Form used to request beam time both when the proposal is initially submitted and for subsequent cycles as long as the proposal is active.

General user: An investigator who applies for beam time through the APS peer-review proposal process for general users.

General user (beam) time: Time made available to general users on an APS experiment station/beamline. All general user beam time is allocated through the APS general user proposal process.

Primary reviewer: Member of a Proposal Review Panel who is assigned to lead the discussion of a given proposal.

Project status: A limited number of general user proposals may justify reliable, predictable access over several cycles (up to two years) on a specific beamline (or several beamlines). These proposals are candidates for project status, under which a fixed amount of beam time is allocated in advance for more than one cycle. A proposal requesting project status must specify the specific beamline or beamlines where the work will be performed and justify the need for that location. The proposer must also justify why the goals of the proposal cannot be achieved effectively or efficiently under a standard general user proposal (e.g., the level of investment, such as effort or setup time, to perform the experiment is so large that it can only be justified if regular or fixed access over several run cycles, can be assured).

Proposal spokesperson: Person identified on the proposal submission form as the primary point of contact.

Proposal Review Panels (PRPs): Peer-review groups, organized by technique or scientific discipline, that evaluate the scientific merit and technical feasibility of proposals and provide a rating for each.

Rapid access: The rapid access process provides an option for short-turnaround assignment of beam time for urgent needs that arise between the formal review and allocation cycles.


3.1 Determination of Beam Time Available to General Users

All time designated as general user time must be provided through the APS general user proposal submission and tracking system.

Each beamline must make at least 25% of its beam time available to general users. Typically, this time is figured as 25% of the number of user shifts scheduled by the APS each year. Groups that operate both bending-magnet beamlines and insertion-device beamlines must provide a minimum of 25% on each beamline. If two or more stations can be operated simultaneously, 25% of the time on each must be provided to general users. Individual beamlines, by agreement with the APS, may provide a larger percentage of time to general users. Beamlines may also reserve a portion of beam time for rapid access by general users, with the percentage of time being agreed upon by the beamline and APS management.

Several Collaborative Access Teams (CATs) operate as national user facilities; that is, approximately 100% of the beam time is available to general users. All proposals for experiments at these CATs are submitted and reviewed through the APS general user proposal system. However, these CATs award about 75% of the available beam time directly; the remaining proposals are allocated time by the BAC in the usual manner.

Beamlines operated entirely by the APS will make 80% of the beam time available to general users. Facility staff may compete for this general user beam time through the general user proposal process. If APS provides partial operational support for a beamline, the amount of general user time on that beamline will be negotiated on a case-by-case basis.

The APS permits general users to conduct both proprietary and non-proprietary research at the facility. Individual CATs, however, may petition the Associate Laboratory Director for the APS (ALD/APS) to exclude propriety research by general users.

CAT members may apply for general user time on any beamline. On their own beamlines, however, the following conditions apply:

  • The CAT formally offers more than 25% of the scheduled user shifts to general users on a regular basis. (CAT members are eligible only for the portion of general user time in excess of 25%.)
  • The intellectual basis of the research originates with the CAT member applying for general user time.

3.2 Submission

In general, proposals are solicited three times a year, about two months before each run. The APS web-based proposal submission and tracking system is used throughout the proposal process, from proposal preparation to beam time allocation. The prospective investigator uses the web form to provide detailed information on the experiment (including the specific beamline required, as appropriate) and the research personnel. The system provides access to individual beamline web pages and to a listing of the techniques and equipment available to general users at each beamline.

3.3 Review

Peer reviewers evaluate the scientific merit and technical feasibility of each proposal and assign a numerical rating. The ratings are defined in Table 1. Reviewers are strongly encouraged to provide comments as well. Different review processes are used for macromolecular crystallography and all other science.

3.3.1 Macromolecular Crystallography

Each macromolecular crystallography proposal is evaluated independently by two reviewers. These reviewers are drawn from a pool of individuals identified by the user community. The APS User Office maintains a database of these reviewers and assigns proposals by matching reviewer expertise and proposal content.

3.3.2 All Other Science

In all other areas, proposal review is handled by Proposal Review Panels (PRPs). Panels may be constituted in several technical or scientific areas to meet the requirements for competent scientific review of all general user proposals. If necessary, ad hoc reviews may supplement the review provided by a particular panel.

Each panel consists of at least four persons appointed by the ALD/APS for two-year terms, renewable by mutual consent. The ALD/APS also appoints the Review Panel Chairs. The APS User Organization Steering Committee (APSUO) and CAT Directors provide candidates for consideration by the ALD/APS.

Each PRP meets once before each user run. For each proposal, the Review Panel Chair assigns two primary reviewers, who must read the assigned proposal and be prepared to lead discussion regarding its content. All reviewers are expected to be somewhat familiar with all proposals and are expected to contribute to discussions of the proposal. At the meeting, the panel reaches a consensus evaluation of each proposal under consideration and assigns a score. Review criteria are available on the APS general user web page.

3.3.3 Project Status

Candidate project proposals will be evaluated by the appropriate PRP, then receive additional scrutiny by the subcommittee of the Scientific Advisory Committee (SAC) that reviews partner user proposals. The SAC subcommittee will use the following criteria to determine whether a proposal should be granted project status: (1) PRP rating, (2) supplemental information provided by the principal investigator on the proposal (in the Questions section), and (3) input from the management of the requested beamline(s). APS management makes the final decisions on project status.


Table 1. Definition of Ratings Used in Reviewing General User Proposals

1 - Extraordinary

The proposal involves highly innovative research of great scientific or technological importance. Proposed research will significantly advance knowledge in a specific scientific discipline/field or create a new technological area. Considerable societal relevance is demonstrated. The radiation characteristics of the APS are highly desirable for the success of the proposed work.

2 - Excellent

The proposed research is of high quality and has potential for making an important contribution to a specific field, scientific discipline, or technical development project. The work is cutting edge and is likely to be published in a leading scientific journal or lead to advances in a technological area. The radiation characteristics of the APS are important to the success of the proposed work.

3 - Good

The proposed research is near cutting-edge and likely to produce publishable results or incremental technological advances. Impact on a specific field, scientific discipline, or technological area is likely. Synchrotron radiation is essential to accomplish the intended goals of the research. The proposed work will greatly benefit from access to the APS.

4 - Fair

The proposed research is interesting but may not significantly impact a specific field, scientific discipline, or technological area. Publication may or may not result from this research. Synchrotron radiation is required, but the proposed work could be performed at other facilities.

5 - Poor

The proposed research is not well planned or is not feasible. Results would not make important contributions to fundamental or applied understanding, and work is not likely to result in publication. The need for synchrotron radiation is not clear.

3.4 Beamline Evaluation

Each beamline identified as a potential host for a general user proposal will determine the suitability of its facilities for the proposed experiment. Each prospective beamline may also provide any other information that may have bearing on the decision on whether to award beam time. This input may include (but is not limited to) environment, safety, and health issues; the past performance of an investigator; specific outreach on the part of the beamline; or a unique suitability of the sector or beamline facilities to accommodate the general user proposal.

3.5 Beam Time Awards

The reviewers’ scores and comments and comments from the beamlines are provided to a Beam Time Allocation Committee (BAC). Currently there are two BACs, one for macromolecular crystallography and one for all other science. Members of the BACs are appointed by the ALD/APS for a term of two years, renewable by mutual consent. The Directors of all operational CATs provide candidates for consideration by the ALD/APS.

The BACs meet once before each user run to determine which proposals will receive beam time and where. However, the allocation process differs for proposals that request a national user facility as a first choice and for new proposals that request rapid access during the submission cycle.

The APS User Office determines the number of shifts each beamline is obligated to provide to general users for each scheduling period on the basis of available user shifts, percentage GUP obligation for that beamline, and other beamline commitments (e.g., partner user proposals or general user proposals with project status). The APS authorizes the portion of general user time that a beamline may award as rapid access.

3.5.1 General Process

In awarding beam time, the BAC takes into consideration the following factors:

  • Proposal reviews and ratings from PRPs.
  • Beamline feasibility evaluations.
  • Special considerations (in support of outreach goals or for exploratory work).
  • Requested beamline(s).
  • Likelihood of success.
  • Demonstrated need for APS and beamline facilities.

The BAC determines which proposals will be allocated time, which beamline will receive each proposal, and the amount of time to be allocated to each proposal. If only one beamline is requested, the BAC must honor that request if at all possible. The BAC seeks a balance between adventurous, exploratory experiments and those with a clear expected result.

The BAC will also provide a waiting list of proposals, by beamline, so that if time becomes available (for example, through the cancellation of an awarded proposal), the next suitable proposal can be accommodated. If no suitable proposals are available, the CAT will be considered to have met its general user obligation for that cycle. Proposals on the waiting list are reconsidered in later review cycles.

3.5.2 Special Cases

For rapid-access requests on new proposals submitted during a run cycle, the requested beamline evaluates the proposal immediately, in parallel with the normal peer review. If the beamline considers the proposed experiment acceptable and beam time is available, the experiment can be scheduled. However, the proposal will continue through the normal review process, with the conclusions evaluated retrospectively. The BAC provides oversight of the rapid-access general user proposal process.

For proposals requesting a beamline operated by a CAT that is classified as a national user facility, in general, 75% of the beam time is allocated directly by the CAT, from among the general user proposals requesting that beamline. The DOE-required 25% of the beam time is allocated by the BAC through the normal review process. The BAC considers only those proposals that the CAT has not already selected.

If issues arise for which no formal policy exists, the BAC will resolve these issues until a formal policy can be developed and approved.


The proposal submission, review, and allocation system is diagrammed in Figure 1 and described in the following sections.

4.1 Submission

Proposers can request up to three specific beamlines, or they may indicate that any appropriate beamline is acceptable. For proposals in areas other than macromolecular crystallography, at least one beamline must be identified as a potential host. For beamlines operated by the APS through the X-ray Operations and Research Section (XOR), users must also specify the instrument or capability needed. The proposal submission form includes a listing of techniques and capabilities, and the system provides links to individual beamline web pages and the APS Beamline Directory.

A single proposal form is used for all general user experiments. This form requests basic information required by the APS about the proposers, the subject of the proposed research, agencies funding the research, beamline(s) of interest, and an abstract. Additional or different information is requested depending on whether the proposal is for macromolecular crystallography or all other science.

All submitted proposals go simultaneously to the requested beamlines, the Proposal Review Panels, and the APS User Office.

4.2 Review

4.2.1 Macromolecular Crystallography

Each macromolecular crystallography proposal goes directly to two reviewers selected by the APS User Office by matching proposal content and reviewer expertise. Proposals are sent electronically to reviewers, who are asked to return their reviews electronically within one week. If a particular review is not received by that deadline, the proposal is sent to another reviewer. If the scores received differ by more than 1.0, the Macromolecular Crystallography PRP will review the proposal and provide a final score. For each evaluation cycle, the APS User Office provides a list of proposals and their scores to the BAC.

4.2.2 All Other Science

The user identifies an appropriate Proposal Review Panel (PRP) on the proposal submission form. For each proposal, the Review Panel Chair determines that the proposal is, in fact, appropriate for the panel and assigns a primary reviewer. For each evaluation cycle, all PRPs meet at the APS shortly after the submission deadline. Working from the definitions given in Table 1, each PRP establishes a consensus score (to two significant digits) for each proposal assigned to it. The PRP also sets a maximum amount of beam time that each proposal should be allocated during its lifetime. This limit serves as a guide to the BAC when beam time awards are made. For each evaluation cycle, the APS User Office provides a list of proposals and their consensus scores to the BAC.

4.2.3 Project Status

The User Office coordinates review of project status requests with the relevant PRP (selected by the proposer) and with the SAC subcommittee for partner user proposals.

4.2.4 Rapid Access

Submitted proposals requesting rapid access are considered on a continuing basis and are not subject to evaluation cycle deadlines. To permit timely access, the proposal is sent to the requested beamline at the same time it is sent to the reviewers. The beamline may choose to award beam time and schedule the user’s visit before the review is completed. If so, the normal review process will still take place, with the conclusions evaluated retrospectively. The beamline provides a list of scheduled rapid-access proposals to the BAC (through the User Office).

4.3 Beamline Evaluation

All prospective beamlines listed on the proposal are notified when the APS User Office receives a proposal (or beam time request). The beamlines may view and comment on the proposal at any time after it is submitted. These beamlines also receive the reviewers’ reports.

Each beamline has the opportunity to provide input to the BAC regarding the suitability of its facilities for the experiments proposed for its beamline.

Prior to the meeting of the BAC, the beamlines designated as national user facilities select beam time requests for beam time award and forward their decisions to the APS User Office for use by the BAC.

4.4 Beam Time Awards

Shortly after the all review scores have been determined and beamlines have provided input, the two BACs (macromolecular crystallography and non-MC or all other science) allocate beam time. The non-MC BAC meets, reviews the electronic autoallocation process, adjusting the allocations as appropriate on the basis of demand, instrument choice, and beamline feasibility assessments. The MC BAC members review the autoallocations electronically, confer electronically as needed, and the MC BAC Chair makes any needed adjustments.

Immediately following the BAC meeting (and before the general users are notified), the beamlines are notified by the APS User Office of the beam time awards on their facilities. Should the beamline strongly disagree with the decision of the BAC (e.g., if the proposed experiment is not technically feasible on the beamline), the beamline coordinator may appeal to the chair of the BAC. This appeal must be made within two working days. In these cases, the BAC Chair is authorized to act on behalf of the BAC to resolve the appeal.

Once the BAC awards beam time, the beamline is responsible for scheduling the general user experiment and informing the APS User Office of the dates. Beamlines should make every effort to schedule awarded general user proposals in the next run. However, if no suitable time can be agreed upon with the general user, the beamline may schedule a general user in the following run. Upon mutual agreement between the beamline and the general user, awarded time may be scheduled at a later time.

For rapid-access beam time requests, a beamline may choose to award beam time at any time after the proposal is submitted. This process provides a mechanism for beamlines to meet user needs for prompt access to their facilities.

4.5 Appeals

If a proposal is not awarded beam time, the APS User Office will notify the proposal spokesperson and explain why. The proposer may modify and resubmit the proposal or withdraw it. If the proposer has concerns about how the review process was administered, he or she may communicate these concerns in writing to the ALD/APS.

Appeals for denial of beam time for a beamline that is designated as a national user facility are heard jointly by the beamline and the BAC. Otherwise, the following appeals are heard by the ALD/APS:

  • Denial of beam time for all beamlines except those designated as national user facilities.
  • Damage to beamline-owned equipment.
  • Beamline failure to perform/comply.
  • User failure to perform/comply.
  • Beamline requests to reduce general user beam time obligations.


The APS provides the following support to the general user proposal process:

  • Maintains a web-based system for proposal submission, tracking, and review.
  • Maintains a beamline directory listing techniques and equipment available to general users.
  • Maintains databases of reviewers and review panels.
  • Arranges for peer review of proposals.
  • Provides all administrative support for review meetings.
  • Notifies users of decisions regarding allocation of beam time.


6.1 Beamline Responsibilities

When a beamline or station is declared operational, it must provide the APS with a memo stating the instruments and techniques that will be available to general users and identifying any exceptions to this APS general user policy (e.g., the exclusion of general users conducting proprietary or classified research.)

Any beamline made available to a general user will be equipped, and in proper working condition, to deliver photons having the radiation characteristics required for the generic class of experiments for which the beamline was approved. The beamline will also supply all equipment that was designated as available to general users when the beamline was declared operational, as well as provide the required amount of technical support.

The beamline will also permit the general user to use existing sector laboratory facilities in the Laboratory Office Module for tasks that cannot reasonably be done off-site.

The host beamline will provide each general user with the technical training required to use the beamline and any ancillary equipment to which the general user has been granted access. If a general user requests the use of individually owned equipment not officially designated for general user use, the beamline may refuse the request or, at its discretion, require the general user to use it in collaboration with the owner of the equipment.

For CAT-owned beamlines, during scheduled general user access periods, the host beamline will give general users the same level of technical support that it provides to its members.

6.2 Beamline Rights

For general user proposals in which beamline staff members are not collaborating, the beamline may determine that costs associated with the proposed experiment are in excess of routine expenditures. In these cases, the beamline will advise the APS User Office, which will ensure that the general user has a funded operating cost code (User Account) in place to cover the supplies, materials, or services required by the general user. To cover routine costs incurred by general users at the APS, the APS will provide a cost code and spending authority limits.

A beamline may request in writing to the BAC that a specific general user not be granted time on that beamline. The written request must state the reasons for the exclusion of a particular general user. Appeals to the decision of the BAC to these requests will be decided by the ALD/APS. Requests for other exclusions to this policy (e.g., to exclude a particular category of general users) must also be made in writing to the ALD/APS, who will address each request individually.


7.1 General User Responsibilities

All general users must complete appropriate training (at a minimum, all core APS user training requirements and sector-specific training) and have a valid User Agreement in place between the APS and the institution that sponsors the research. General users who damage equipment owned by a CAT or APS after receiving appropriate training in its use will be held liable for the damage, according to the provisions of their institutional user agreements.

Each general user must also submit an Experiment Safety Assessment Form for each experiment to be conducted.

General users are required to submit full citations of all publications resulting from their work to the APS User Office for inclusion in the APS publications database and to provide this information to the host beamline. Failure to submit the required publication citations may result in denial of requests for beam time in subsequent proposals. When work performed at the APS by a general user is submitted for publication, the author must include appropriate acknowledgment of the APS and the beamline in the manuscript.

7.2 General User Rights

General users have the right to appeal denial of beam time as outlined under the Appeals section of these procedures.

Figure 1. Submission, Review, and Allocation Process

for APS General User Proposals