Improving the Reliability of Particle Accelerator Magnets: Learning From Our Failures

There are many ways that a resistive particle accelerator electromagnet can fail, and most failure modes and their root causes are well known to more experienced magnet engineers. There are thousands of new electromagnets being fabricated every year and tens of thousands already operating in institutions worldwide. Yet some magnet engineers designing a new-style magnet still do not make the design choices that will lead to fewer failing magnets; fabricators still make errors as they assemble magnets and magnets still operate, for example, with low conductivity water (LCW) that corrodes or erodes the coils' conductor. One reason for these continuing problems is the lack of readily available information on the most reliable materials, fabrication techniques, and operating parameters. In order to learn from the experiences of other institutions running accelerators regarding their magnets' failure modes and how they have dealt with them, a web-based survey was created with 64 detailed questions. The survey was completed by 28 designers and operators of accelerator magnets worldwide covering conventional magnets 5 to 55 years old, being used in all kinds of accelerators, in dc, ramping, and pulsed modes. A detailed analysis of the survey's responses was carried out to find, for example, correlations between materials used and frequencies of related failure types. This paper describes the results of the survey analysis, leading to some more reliable design values, materials, fabrication techniques, and operating conditions, especially the properties of the LCW, and thus provides advice on how to improve the reliability of accelerator electromagnets.