Speaker
Description
The Advanced Light Source Upgrade (ALS‑U) project at the Lawrence Berkeley National Laboratory (LBNL) requires a comprehensive evaluation of a swap‑out incident, defined as an errant electron beam being injected into a photon beamline and subsequently lost, resulting in potentially unacceptable radiation dose levels on the experimental floor. Historically, for the currently operated ALS facility, this scenario was analyzed through detailed reverse‑tracking accelerator physics simulations to determine the precise locations and apertures of beam masks capable of intercepting mis‑steered electrons inside the accelerator tunnel. While effective, that method demanded extensive knowledge of all lattice elements and required nearly two years of sustained computational effort.
For ALS‑U, a more streamlined and forward‑looking methodology was developed. Consistent with the current ALS safety strategy, the upgraded facility will rely on multiple engineered layers of protection, including beam‑energy and beam‑current interlocks to reduce the probability of occurrence and interlocked radiation monitors to minimize event duration. Additionally, clearing magnets at the entrance of photon beamlines together with photon beam masks will ensure that any errant beam is lost inside the shield walls.
However, because the ALS‑U magnet lattice was still evolving during the safety analysis phase, traditional reverse‑tracking was impractical. Instead, a ray‑tracing–based approach that uses all electron beam trajectories transmitted through the main aperture that separates the electron storage ring from the photon transport line and includes the effect of the clearing magnet field, was implemented to identify the worst possible electron strike locations for a set of representative beamlines, followed by radiation‑transport simulations to quantify dose levels outside the shield walls and verify the existing shielding.
This analysis validates the efficacy of the clearing‑magnet concept, allows to optimize masks aperture and location along a beamline without the need of extensive electron beam reverse tracking, and identifies locations where supplemental shielding is needed.
Together, these results provide a robust technical basis for the ALS‑U swap‑out safety strategy and ensure that the upgraded facility meets stringent radiation‑protection requirements while enabling next‑generation synchrotron performance.
| Topics | T1. Source terms, new accelerator facilities and related topics |
|---|