Emittance related topics for fourth generation storage ring light sources

Abstract: In this thesis several aspects related to a new generation of storage ring light sources are discussed. Due to a reduction of electron beam emittance, fourth generation storage rings provide synchrotron radiation sources close to the diffraction limit at X-ray wavelengths. This results in a significant increase in photon brightness that is beneficial in a variety of synchrotron radiation based experiments. The MAX IV Laboratory in Lund, Sweden, operates the first storage ring light source of the fourth generation. Its 3 GeV storage ring has a circumference of 528 m and employs a multibend achromat lattice with a horizontal electron beam emittance of 0.33 nm rad.Beam size and emittance diagnostics of ultralow horizontal and vertical emittance electron beams can be achieved by focusing synchrotron radiation from dipole magnets, to form an image of the beam. When imaging in the visible and near-visible spectral ranges, diffraction and emission effects are dominant. The presented refined methods, however, make it possible and even beneficial to deduce small electron beam sizes from this radiation. Diagnostics of the longitudinal charge distribution in the bunch, based on time-resolved measurements of synchrotron radiation, are of special interest, since bunch lengthening with passive harmonic rf cavities is an essential ingredient in the concept of the storage ring, extending Touschek lifetime and mitigating the effects of intrabeam scattering.The horizontal emittance in the MAX IV 3 GeV storage ring will lead, after correction of coupling and minimization of vertical dispersion, to a very low vertical emittance, lower than what might be requested by synchrotron radiation experimentalists. Operating with the negative consequences of a too low emittance such as a Touschek lifetime shorter than necessary and an increased intrabeam scattering can, however, be avoided if the vertical emittance is adjusted to a desired level in a controlled way. A scheme is introduced that excites vertical emittance by vertical dispersion while maintaining small source sizes for synchrotron radiation production in the insertion devices, and restores Touschek lifetime.