A. Lüdeke, PSI, Villigen, Switzerland; M. Bieler, DESY, Hamburg, Germany; R. H. A. Farias, LNLS, Campinas, Brazil; S. Krecic, Elettra-Syncrotrone Trieste, Italy; R. Müller, HZB, Berlin, Germany; M. Pont, CELLS-ALBA, Cerdanyola del Vallès, Spain; M. Takao, JASRI/SPring-8, Japan


Storage ring light sources aim for high operational reliability. Very often beam availability is used as an operation metric to measure the reliability. A survey of several light sources reveals that the calculation of availability varies significantly between facilities. This complicates useful comparisons of reliability. Furthermore the beam availability typically does not provide insight regarding reliability of beam characteristics such as orbit- and beam size stability.

The authors propose specific metrics to evaluate the reliability of storage ring light sources; these metrics allow detailed and meaningful comparison across facilities. Such comparisons are useful to further optimize the reliability of storage ring light source facilities.


Reliability is typically defined as the ability of a system to serve a given function over time. In this sense the reliability of a particle accelerator is very important for user facilities like storage ring light sources and provides an important design objective for new large scale accelerator facilities as for example the International Linear Collider (Himel 2007). Clearly operation metrics should quantify the reliability of a particle accelerator. If the objective is to assess the improvement of a specific facility over time, then the operation metric should be closely related to specific user requirements (Lüdeke 2014). In order to compare reliability of different facilities, one needs a common standard for the calculation of operation metrics.

Commonly beam availability or “up-time” is often used to compare the reliability of light sources. While statistics are published for most light sources, few facilities supply precise definitions on how the information is calculated. A survey of several light sources revealed (Lüdeke 2009) that the calculation of this metric varies considerably. The conditions under which beam is considered ’available’ are often defined only in simple common sense terms, and even if there are formal definitions, they differ between facilities. Furthermore a large variety of failure modes is often convolved into “beam not available”, commonly referred to as “downtime”. Since many downtime failure modes are specific to individual facilities, this further complicates the comparison of beam availability.

Our aim is to provide simple, well-defined, formal operation metrics for storage ring light sources to make beam reliability at these facilities comparable. The metrics serve to clarify for each facility the beam parameters specified for the users, how the statistical data is processed and how well the standards are met. The authors make the case that the application of these metrics will refine the ability to learn from and compare reliability at storage ring of light sources.