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In the framework of the Spare Radio Frequency Quadrupole Project [1] the layout of an enhanced performance RFQ has been explored. In this note we report the results of the study, including the three options retained and we compare the performance of the different RFQ in relation to the LINAC4 overall performance.

Inspector and Inspector Services framework are innovative developer tools, designed at CERN and used for the design of control applications at the CERN accelerator complex. This paper presents the use of this framework in the implementation of an application that permits fast emittance reconstruction from profile measurements at Linac3 using the quadrupole variation method. The theoretical background is presented along with measurements, simulations, error analysis and technical characteristics of the application and software platform.

To provide HL-LHC performance, the CERN LHC injector chain underwent a major upgrade during an almost 2-year-long shutdown. In the first half of 2021 the injectors were gradually re-started with the aim to reach at least pre-shutdown parameters for LHC as well as for fixed target beams. The strategy of the commissioning across the complex, a summary of the many challenges and finally the achievements will be presented. Several lessons were learned and have been integrated to define the strategy for the performance ramp-up over the coming years. Remaining limitations and prospects for LHC beam parameters at the exit of the LHC injector chain in the years to come will be discussed. Finally, the emerging need for improved operability of the CERN complex will be addressed, with a description of the first efforts to meet the availability and flexibility requirements of the HL-LHC era while at the same time maximizing fixed target physics output., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

Beam loss occurs in Radio Frequency Quadrupoles (RFQ), and has been observed in the H⁻ linear accelerator Linac4 (L4) at CERN. To determine if beam loss can induce breakdowns, and to compare the robustness of different materials, tests have been done using pulsed high-voltage DC systems. Electrical breakdown phenomena and conditioning processes have been studied using these systems. Cathodes of different materials were irradiated with 1.2x10¹⁹ H⁻ p/cm², the estimated beam loss of the L4 RFQ over 10 days. The irradiated electrodes were installed in a system to observe if the irradiated area coincided with the breakdown locations, with pulsing parameters similar to the RFQ. Tests of irradiated and non-irradiated electrodes of the same material were done for comparison. The main difference observed was an increase in the number of breakdowns during the initial conditioning that returned to non-irradiated sample values with further running. Visual observations after irradiation show the beam centre and a halo the same diameter of the beam pipe. Breakdown clusters occur in the centre and halo regions, suggesting irradiation is not the only factor determining the breakdown probability., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK

In December 2020 the newly commissioned LINAC4 started delivering beam for the CERN proton accelerator chain, replacing the old LINAC2. LINAC4 is a 352 MHz normal conducting linac, providing a beam of negative hydrogen ions at 160 MeV that are converted into protons at injection into the PS Booster synchrotron. In this paper we report on the achieved beam performance, availability, reproducibility and other operational aspects of LINAC4 during its first fully operational year. We also present the machine developments performed and the plans for future improvements., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

High frequency structures generally translate to high efficiency performances thanks to reduced surfaces of the inner cavity. Two round-profiles geometry and some variations of two important parameters of a 750 MHz IH-DTL are proposed in this paper in order to improve shunt impedance performance regarding an existing solution with flat-walled cavity developed by CERN. The proposed designs are shaped such that they guarantee an easy connection of RF and vacuum auxiliaries. Electromagnetic simulations are checked with CST Microwave Studio., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK

During operation the LINAC4 RFQ (Radio-Frequency-Quadrupole) is exposed to high electric fields which can lead to vacuum breakdown. It is also subject to beam loss that can cause surface modification, including blistering, which can result in reduced electric field handling and an increased breakdown rate. An experimental study has been made to identify materials with high electric field capability and robustness to low-energy irradiation. In this paper we briefly discuss the selection criteria and we analyze these materials investigating their metallurgical properties using advanced microscopic techniques such as Scanning Electron Microscope, Electron Back Scattered Diffraction, Energy-dispersive X-ray Spectroscopy and conventional optical microscopy. These allow to observe and characterize the different materials on aμand a nano-scale, allowing us to compare results before and after irradiation and breakdown testing., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK

We identified the first case in Italy of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.529 variant, using whole-genome sequencing in an Italian subject traveling from Mozambique. Specific mutation profiles deserve further investigations to clarify potential effects on vaccination efficacy. This case highlights the crucial role of rapid and continuous surveillance of SARS-CoV-2 variant circulation.

The 352 MHz Linac4-RFQ is the first rf accelerating structure of the CERN accelerator complex, accelerating an H⁻ beam to 3 MeV. After successful commissioning in 2013, superficial vane damage has been observed in 2020. In view that the RFQ is a single point of failure, in parallel to the production of a near identical spare (RFQ2), design studies on a longer-term upgrade have been launched: Linac4-RFQ3. Main goals are to achieve a design with higher beam acceptance, reduced beam losses, and reduced RF breakdown rate. Two versions of RFQ are under study: a conventional RFQ built by brazing copper, as well as an RFQ with titanium vane tips (brazed on copper). High-gradient experiments suggest that titanium vane tips support higher surface fields compared to copper, up to 40 MV/m, and are more resistant against beam irradiation. In this paper, we present beam dynamics and rfdesign of both variants of RFQ3., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK