ID28 u35

Energy of the 3. and 5. harmonics of a 32 mm period linear undulator as a function of the magnetic gap. The working points of ID28, are indicated by the red points.

The ID28 straight section is currently equipped with three undulators of 32 mm magnetic period (U32). The choice of the magnetic period is the result of a compromise between the necessary tunability within the working energy range between 13.8 and 25.7 keV and maximising the flux by reducing the undulator period as much as possible. Figure indicates the various gap settings for the six working energies of the instrument and the 3. and 5. harmonics of the undulator.