Applied geometric tolerancing in accelerator component design

The authors discuss how the ANSI Y14.5M 1982 Standard for Dimensioning and Tolerancing applies to the fabrication of components for cryogenic accelerators. Information on selecting datums and assigning positional tolerances that ensure stress-free mechanical mating conditions as well as interchangeability of parts is included. In addition, modifiers can be used in the feature-control frames that specify allowable deviations from nominal geometry; their use reduces the cost of fabrication without compromising ease of mechanical assembly. The physics requirements unique to the design of linear accelerators also call for the prudent application of some seldom-used modifier that reduces the need for alignment of initial assemblies to optimize accelerator performance.<>