The 3.0 GeV ALBA Synchrotron Light Source, in operation with users since 2012, is looking forward an upgrade aimed at enhancing the brightness and coherence fraction of the delivered X-ray beam. The Storage Ring (SR) will be completely renewed but we plan on keeping the same orbit length and the position of the ID source points. The energy of the electrons will be preserved and the same injector will be used. Major part of the Insertion Devices and Front Ends will be kept; new ones will feed additional long Beamlines (230m-275m), included on the project. The “dark period” is foreseen for 2030-2031. This paper presents the strategic plans being developed to test and assemble the new SR components, the dismantling of the present SR and the seamless installation of the upgraded SR. Emphasizing a cost-effective and time-efficient approach, we have started the planning by focusing on optimizing spaces and equipment movements necessary for the upgrade process.

ALBA is working on the upgrade project that shall transform the actual storage ring, in operation since 2012, into a 4th generation light source, in which the soft X-rays part of the spectrum shall be diffraction limited. The project was launched in 2021 with an R&D budget to build prototypes of the more critical components. The storage ring upgrade is based on a MBA lattice which has to comply with several constraints imposed by the decision of maintaining the same circumference (269 m), the same number of cells (16), the same beam energy (3 GeV), and as many of the source points as possible unperturbed. At present, the lattice optimization, iterating with the technical constraints of space and performance, is ongoing. This paper presents the status of the project, with the present proposed lattice, the proposed design for magnets, vacuum chambers and girders, the proposed RF system with fundamental and harmonics cavities, and the general context of the upgrade.

A collaboration agreement between the ALBA, DESY and HZB institutions was signed on 2021 in order to commission the 3rd harmonic normal conducting, HOM damped, active cavity designed and prototyped by ALBA. The cavity prototype arrived to ALBA in December 2021, and successfully passed the low power RF and vacuum tests. Afterwards, in January 2022 it was sent to HZB and mounted in the SUPRALAB@HZB, in the HoBiCat bunker for bead-pull measurements and high-power conditioning. Finally, in May 2022 the cavity was installed in the BESSY-II ring for test with beam. In this contribution we summarize and highlight the major results after two years of commissioning with beam including the lengthening capability of the cavity for single bunch and homogeneous filling pattern, lifetime increase measurements, HOM damping capability and transient beam loading effects due to the presence of a gap in the filling pattern.

A digital direct RF feedback (DDRF) has been implemented in the DLLRF of the ALBA synchrotron light source in order to mitigate the beam loading effects of the beam. Specifically, with the DDRF implemented in the main cavities, the tune shift due to beam loading can be minimized and therefore the DC-Robinson instability can be mitigated. It can also be used to minimize voltage drops in case of transients after a cavity loss during the operation. Also, for the next generation machine ALBA-II and applied to the active 3rd harmonic system, it can be used to fight against AC-Robinson instability induced by the harmonic cavities, increasing the damping rate of the fundamental CBI mode, and reducing the transient beam loading effects. In this contribution we present measurements with beam of the DDRF applied to ALBA main cavities, demonstrating a reduction of a factor two in the effective impedance of the cavity as seen by the beam.

Due to the constrains imposed by the tight geometry of the ALBA storage ring, the initial 6BA lattice envisioned for the ALBA-II upgrade was reconsidered in favor of a more relaxed 5BA configuration. The first engineering studies of magnets and vacuum chambers made evident many short comings of the 6BA optics. The here proposed 5BA optics allows for an easier integration at cost of a small increase of the natural emittance. The employed linear and non-linear optics optimization process is here described along with the first studies about dynamic aperture and lifetime.