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NSLS-II User Guide

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Beam Time Allocation

The total amount of beam time available on a beamline each cycle is a combination of the time required for commissioning, maintaining, and upgrading the beamlines (called “technical commissioning” time) and the time available for user experiments (called the “user-available” time). As new beamlines come online, they transition from a majority of technical commissioning (TC) time to a majority of user-available (UA) time. 

Each cycle, beamlines may designate a fraction of their UA time for “science commissioning (SC)” experiments and allocate appropriate GU proposals for this purpose. Science commissioning is aimed at engaging the scientific community in user-assisted commissioning of new beamlines and/or newly implemented endstation capabilities. 

The TC and UA fractions are determined by management in consultation with beamline staff prior to each run cycle. The use of TC and SC time by each beamline is reviewed each cycle by NSLS-II management to ensure that it is appropriate and justified.

Once a beamline reaches mature operations, which is typically ~1 year after “first light”, a minimum of 50% of the UA time is allocated to a combination of GU, BAG, and RA proposals every run cycle. Up to 40% of the UA time may be allocated to PU proposals and up to 10% of the UA time may be allocated for beamline discretionary time.

Beam time allocation and scheduling

Each cycle, the Proposal Review Panels review and score new proposals and they also recommend beam time allocations for all beam time requests (BTRs) against existing proposals. For the BTRs, if a proposal has already received beam time in one or more prior run cycles, the beam time request must also include a brief statement of progress resulting from those previous beam time awards. This progress report is reviewed by the PRP, and if it is not satisfactory, the PRP may reduce future beam time allocations.

Once allocation recommendations are made by the PRPs, they are approved and finalized by beamline staff and management. Users are notified of the results of the review process via the PASS system and the Lead Beamline Scientist at each beamline is responsible for the scheduling.