Beam Lifetime Optimization by Adjusting the Sextupoles at the Mls and Bessy

The Metrology Light Source (MLS) is a dedicated electron storage ring for metrology applications with three families of sextupoles. The existing setting of the three independently powered sextupole families respective to lifetime were roughly determined by scanning their strengths against each other. As a flexible machine the sextupole families of the MLS can be regrouped into new families, which increase the complexity of the scan procedure. Consequently the former strategy would be too time-consuming for refined global scan and it has to be complemented with physical constraints. Therefore a scheme has been developed to keep the chromaticity in a reasonable range during the scan and to reduce the degree of freedom, which is even more important at BESSY II with increasing number of independent sextupole circuits. This paper presents the principle of sextupole scan and the experimental results at the MLS and preliminary tests at BESSY II.