# US accelerator projects: Lab reports

28 September 2021

• Earlier this summer, the Advanced Light Source (ALS), a synchrotron user facility at the US Department of Energy’s (DOE) Lawrence Berkeley National Laboratory, received federal approval (known as Critical Decision 2) for the 590 million budget, schedule and technical scope of a major upgrade project (ALS-U) that will boost the brightness of its X-ray beams at least a hundredfold. In addition to the replacement of the existing electron storage ring, the upgrade involves construction of two new beamlines to take full advantage of ALS-U’s enhanced beam properties. The project will also provide for the realignment of existing beamlines and a seismic and shielding upgrade of the storage-ring tunnel. A key challenge with ALS-U is the construction of a second concentric ring, called an accumulator, inside the already-cramped concrete tunnels that house the storage ring. This unique feature enables a technique called on-axis, swap-out injection, which allows the electron beam to be injected into the storage ring with minimal perturbation. • While construction work for the815 million upgrade of Argonne National Laboratory’s Advanced Photon Source (APS) is already well under way, the replacement of the facility’s existing electron storage ring – which will require a year-long shutdown of the APS experimental programme – is now scheduled to kick off in April 2023. That represents a 10-month delay versus the original planned refit owing to the operational impacts of the COVID-19 pandemic. The upgrade of the APS, a national synchrotron research facility funded by the US DOE, will reduce electron beam emittance by a factor of 70 from its present value which, together with a doubling of stored beam current and the introduction of high-performance insertion devices (some superconducting), will yield X-ray beams two to three orders of magnitude brighter than the current machine. Delaying the shutdown for the storage-ring upgrade will allow the APS to continue operating for all three experimental runs in 2022.

• The US DOE’s Brookhaven National Laboratory (BNL) has named Wolfram Fischer as chair of its Collider–Accelerator Department (C-AD). C-AD develops, improves and operates BNL’s suite of particle and heavy-ion accelerators – including the Relativistic Heavy Ion Collider (RHIC) and Alternating Gradient Synchrotron (AGS) – and will also play a key role in supporting the upcoming construction of the Electron-Ion Collider (see Partnership yields big wins for the EIC). Fischer previously served as accelerator division head in C-AD.