Losses of vacuum-chamber full-penetration weldments

In the storage ring of the 7 GeV Advanced Photon Source, there are 480 vacuum-chamber end flanges and 80 tube welded joints, accounting for a total of 560 full-penetration weldments. This note is to give an estimation of the longitudinal and transverse losses contributed by these weldments. For this purpose, the elliptical cross-section of the structure is approximated by a circular one. The 2D code TBCI is then employed to calculate the losses for three different beam bunch lengths, which are, respectively, 0.58, 1.16 and 1.76 cm. As a comparison, the losses of the RF cavities and of the transitions between beam chamber and insertion device (ID) sections are also listed. It is seen that the losses contributed by the weldments are very small. They should not have any significant effects on beam dynamics