A&T Sector Note on the PS transverse feedback

In a particle accelerator, several contributions can degrade the beam quality and particularly the beam transverse emittance. In this document we will describe a system used in the CERN Proton Synchrotron (PS) to cope with the injection steering errors and the transverse instabilities: the PS transverse feedback (PS TFB). As time progresses, this system is also being used for other purpose, to increase in a controlled way the beam transverse emittance and to excite the beam for the Multi-Turn-Extraction (MTE). In 2016, it has been successfully used on some operational beams to damp injection oscillations. This allowed to test the reliability of the system for its operational deployment. A piquet service is available in case of problem

Matching Studies Between the CERN PSB and PS Using Turn-by-Turn Beam Profile Acquisitions with a Residual Beam Gas Ionisation Monitor

In the framework of the LHC Injectors Upgrade project, the Beam Gas Ionisation (BGI) profile monitors installed in the Proton Synchrotron (PS) were fitted with a gas injection system capable of boosting the signal rate high enough to capture single turn acquisitions immediately after injection. This contribution reports on the studies carried out during the beam commissioning of the BGI system in a turn-by-turn matching monitor mode for its eventual implementation in an optimisation framework to preserve emittance during transfer between the PS Booster and PS. The BGI commissioning included a benchmarking with data from a wire-grid secondary emission monitor inserted into the circulating beam

A Ferroelectric Fast Reactive Tuner (FE-FRT) to Combat Microphonics

A prototype Fast Reactive Tuner (FRT) for superconducting cavities has been developed, which allows the frequency to be controlled by application of a potential difference across a newly developed ultra-low loss ferro-electric material residing within the tuner. The tuner operates at room temperature, outside of the cryostat and coupled to the cavity via an antenna and co-axial cable. This technique allows for active compensation of microphonics, eliminating the need to design over-coupled fundamental power couplers and thus significantly reducing RF power particularly for low beam current applications. Modelling; simulation; and stability analysis, of the tuner; cavity; measurement system; and feedback loop, have been performed in the frequency and time domain, and are compared to the latest experimental results. The potential benefits of applying this techniques to ERLs, which are seen as one of the major use cases, are detailed both in general and with regards to specific projects. Ideas and designs for an improved next generation FRT are also discussed

CERN’s SRF Test Stand for Cavity Performance Measurements

Recent deployment of a digital LLRF system within the cavity testing framework of CERN’s vertical test cryostats has permitted a full revamp of cavity performance validation. With both full continuous and pulse mode operation, steady state a transient RF behaviour can be effectively probed. Due to direct and integrated control and monitoring of environmental test conditions, standard and novel RF measurement procedures have been developed and integrated into the testing infrastructure, along with a coherent data flow of high granularity measurement data. We present an overview of this cavity measurement system and address the underlying architectural structure, data handling and integration of user interfaces. In addition we highlight the benefits of variety of RF cavity measurements that can now be accommodated in our large 2 K cryostats

Ferro-Electric Fast Reactive Tuner Applications for SRF Cavities

A Ferro-Electric fast Reactive Tuner (FE-FRT) is a novel type of RF cavity tuner containing a low loss ferroelectric material. FE-FRTs have no moving parts and allow cavity frequencies to be changed extremely quickly (on the timescale of 100s of ns or less). They are of particular interest for SRF cavities as they can be placed outside the liquid helium environment and without an FE-FRT it’s typically very difficult to tune SRF cavities quickly. FE-FRTs can be used for a wide variety of use cases including microphonics suppression, RF switching, and transient beam loading compensation. This promises entirely new operational capabilities, increased performance and cost savings for a variety of existing and proposed accelerators. An overview of the theory and potential applications will be discussed in detail

A Ferroelectric Fast Reactive Tuner for Superconducting Cavities

A prototype FerroElectric Fast Reactive Tuner (FE-FRT) for superconducting cavities has been developed, which allows the frequency to be controlled by application of a potential difference across a ferroelectric residing within the tuner. This technique has now become practically feasible due to the recent development of a new extremely low loss ferroelectric material. In a world first, CERN has tested the prototype FE-FRT with a superconducting cavity, and frequency tuning has been successfully demonstrated. This is a significant first step in the development of an entirely new class of tuner. These will allow electronic control of cavity frequencies, by a device operating at room temperature, within timescales that will allow active compensation of microphonics. For many applications this could eliminate the need to use over-coupled fundamental power couplers, thus significantly reducing RF amplifier power

Approaching the High-Intensity Frontier Using the Multi-Turn Extraction at the CERN Proton Synchrotron

Complementary to the physics research at the LHC, several fixed target facilities receive beams from the LHC injector complex. In the scope of the fixed target physics program at the Super Proton Synchrotron, high-intensity proton beams from the Proton Synchrotron are extracted using the Multi-Turn Extraction scheme, which is based on particle trapping in stable islands of the horizontal phase space. Considering the number of protons requested by future experimental fixed target facilities, such as the Search for Hidden Particles experiment, the currently operationally delivered beam intensities are insufficient. Therefore, experimental studies have been conducted to optimize the Multi-Turn Extraction technique and to exploit the possible intensity reach. The results of these studies along with the operational performance of high-intensity beams during the 2017 run are presented in this paper. Furthermore, the impact of the hardware changes pursued in the framework of the LHC Injectors Upgrade project on the high-intensity beam properties is briefly mentioned.Complementary to the physics research at the LHC, sev- eral fixed target facilities receive beams from the LHC in- jector complex. To serve the fixed target physics program at the Super Proton Synchrotron, high-intensity proton beams from the Proton Synchrotron are extracted using the Multi- Turn Extraction technique based on trapping parts of the beam in stable resonance islands. Considering the num- ber of protons requested by future experimental fixed target facilities, such as the Search for Hidden Particles experi- ment, the currently operationally delivered beam intensities are insufficient. Therefore, experimental studies have been conducted to optimize the Multi-Turn Extraction technique and to exploit the possible intensity reach. The results of these studies along with the operational performance of high- intensity beams during the 2017 run are presented in this paper. Furthermore, the impact of the hardware changes pur- sued in the framework of the LHC Injectors Upgrade project on the high-intensity beam properties is briefly mentioned

Beam Commissioning and Optimisation in the CERN Proton Synchrotron After the Upgrade of the LHC Injectors

The CERN LHC injector chain underwent a major upgrade during the Long Shutdown 2 (LS2) in the framework of the LHC Injectors Upgrade (LIU) project. After 2 years of installation work, the Proton Synchrotron (PS) was restarted in 2021 with the goal to achieve pre-LS2 beam quality by the end of 2021. This contribution details the main beam commissioning milestones, difficulties encountered and lessons learned. The status of the fixed-target and LHC beams will be given and improvements in terms of performance, controls and tools will be described

Gestion intégrée des ressources naturelles en zones inondables tropicales

De par leur richesse en ressources naturelles renouvelables, les zones inondables tropicales revêtent un intérêt social et économique majeur pour les pays en développement. Cependant, les fleuves tropicaux sont aujourd'hui de plus en plus aménagés pour satisfaire les besoins liés à de nouvelles activités. Les zones jusque-là régulièrement inondées par la crue annuelle se réduisent ou alors les rythmes de leur inondation sont profondément modifiés. Les impacts de tels changements sont nombreux et portent atteinte à la biodiversité et à la durabilité des systèmes d'exploitation. Il s'avère alors nécessaire de définir de nouvelles approches de la gestion de l'eau, des espaces et des ressources vivantes, qui tout à la fois préservent les écosystèmes et prennent en considération les besoins des différents usagers. Tel est l'objectif de cet ouvrage qui pose, dans un premier temps, la problématique sociétale autour de laquelle cette gestion doit être repensée, en faisant apparaître la diversité d'acteurs et d'institutions concernés. Il présente ensuite les acquis les plus récents de la recherche sur le fonctionnement de ces écosystèmes ainsi que sur les pratiques et stratégies déployées par les populations qui les exploitent. Enfin est abordée la question des instruments à mettre en place pour assurer l'effectivité d'une gestion durable des zones inondables tropicales : après avoir fait le point sur les apports de la recherche concernant les outils de traitement et de partage de l'information environnementale, l'ouvrage se termine par un débat sur les conditions de création et de fonctionnement des institutions de suivi, de concertation et de décision