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The Advanced Proton Driven Plasma Wakefield Experiment (AWAKE) at CERN uses 6 cm long proton bunches extracted from the Super Proton Synchrotron (SPS) at 400 GeV beam energy to drive high gradient plasma wakefields for the acceleration of electron bunches to 2 GeV within a 10 m length. Knowledge and control of the position of both copropagating beams is crucial for the operation of the experiment. Whilst the current electron beam position monitoring system at AWAKE can be used in the absence of the proton beam, the proton bunch signal dominates when both particle bunches are present simultaneously. A new technique based on the generation of Cherenkov diffraction radiation (ChDR) in a dielectric material placed in close proximity to the particle beam has been designed to exploit the large bunch length difference of the particle beams at AWAKE, 200 ps for protons versus a few ps for electrons, such that the electron signal dominates. Hence, this technique would allow for the position measurement of a short electron bunch in the presence of a more intense but longer proton bunch. The design considerations, numerical analysis and plans for tests at the CERN Linear Electron Accelerator for Research (CLEAR) facility are presented., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

For the accelerator-based future of high energy physics at the energy frontier, CERN started to investigate a 92 km circumference Future Circular Collider (FCC), as e⁺/e⁻ collider the FCC-ee will operate at beam energies up to 182.5 GeV. Beside the machine operational aspects, beam instrumentation will play a key role in verifying and optimizing the machine to achieve the ambitious beam parameters and quality. This paper gives a brief overview of the various challenges to develop the required beam instruments, with focus on beam position, beam size and bunch length measurements, and well as an outline of the planned R activities., Proceedings of the 65th ICFA Advanced Beam Dynamics Workshop on High Luminosity Circular e+e- Colliders, eeFACT2022, Frascati, Italy

The Advanced Wakefield Experiment (AWAKE) at CERN investigates the Plasma-Wakefield acceleration of electrons driven by a relativistic proton bunch. After successfully demonstrating the acceleration process in the AWAKE Run 1, the experiment has now started the Run 2. The AWAKE Run 2 consists of several experimental periods that aim to demonstrate the feasibility of the AWAKE concept beyond the acceleration experiment, showing its feasibility as accelerator for particle physics application. As part of these developments, a dramatic effort in improving the AWAKE instrumentation is sustained. This contribution reports on the current developments of the instrumentation pool upgrade, including the digital camera system for transverse beam profile measurement, beam halo measurement and the spectrometer upgrade studies. The studies on the development of high-frequency beam position monitors are also described., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The AWAKE experiment studies the acceleration of electrons to multi-GeV levels driven by the plasma wakefield generated by an ultra-relativistic and high intensity proton bunch. The proton beam, being considerably more intense than the co-propagating electron bunch, perturbs the measurement of the electron beam position achieved via standard techniques. This contribution shows that the electrons position monitoring is possible by frequency discrimination, exploiting the large bunch length difference between the electron and proton beams. Simulations and a beam measurement hint, the measurement has to be carried out in a frequency regime of a few tens of GHz, which is far beyond the spectrum produced by the 1ns long (4 �� Gaussian) proton bunch. As operating a conventional Beam Position Monitor (BPM) in this frequency range is problematic, an innovative approach based on the emission of coherent Cherenkov Diffraction Radiation (ChDR) in dielectrics is being studied. After describing the monitor concept and design, we will report about the results achieved with a prototype system at the CERN electron facility CLEAR., Proceedings of the 10th International Beam Instrumentation Conference, IBIC2021, Pohang, Rep. of Korea

The Super Proton Synchrotron (SPS) is both, the final machine in the pre-accelerator chain of the Large Hadron Collider (LHC) at CERN, and a machine providing several experiments with proton and ion beams. In the framework of CERN���s LHC Injectors Upgrade (LIU) project, aimed at improving the performances of the pre-accelerators in view of the high-luminosity upgrade of the LHC, the Beam Position Monitor (BPM) system of the SPS was redesigned during Run 2 of the LHC and deployed during the subsequent Long Shutdown 2 (LS2). This new system is called ALPS (A Logarithmic Position System) and acquires the signals from some 240 BPMs. It is designed to improve the system���s reliability and reduce the required maintenance with respect to its predecessor. During the restart of the SPS in 2021, the BPM system was a key element of the fast recommissioning of the machine, proving the validity of the chosen design approach and pre-beam commissioning strategy. This paper aims to illustrate the design choices made for ALPS, the strategy for commissioning it with beam in parallel with the machine restart, the commissioning procedure and the results obtained., Proceedings of the 10th International Beam Instrumentation Conference, IBIC2021, Pohang, Rep. of Korea

The Large Hadron Collider (LHC) at CERN will be equipped with two hollow electron lenses (HEL) for the high luminosity upgrade, which allow for scraping of the LHC proton or ion beams transverse tails by overlapping a coaxial hollow electron beam over a 3 m length. A precise alignment of the two beams is essential for the HEL functionality, the bunched LHC hadron beam of up to 7 TeV beam energy, and the non-relativistic, DC-like electron hollow beam of 10 keV energy. The absolute and relative transverse positions of both beams will be monitored by two stripline beam position monitors (BPM), located in the HEL, and the pickup signal processed by a narrowband signal detection system. This paper summarizes the analysis of the expected proton and electron beam signals, including laboratory measurements, with aim of a narrowband diode-detection read-out electronics as BPM signal processor., Proceedings of the 10th International Beam Instrumentation Conference, IBIC2021, Pohang, Rep. of Korea

This report summarizes the results of MD1447 about the hierarchy limit of the LHC collimation system in IR7 at 6.5 TeV and its impedance, performed during MD block 1 of 2016. The hierarchy breakage seen in a similar activity in 2015 when deploying 1σ-retractions between TCSG and TCP collimators was confirmed, and a viable solution demonstrated with beam. In addition, measurements of tune–shifts induced by changes in collimator gaps were performed when moving the IR7 TCSG collimators all together, or when moving only those with the largest contribution to impedance. The MD activity included a re-alignment of all the IR7 collimatorsto the beam, prior to the investigations on the hierarchy breakage, and an instability threshold measurement, at the end. The MD activity is important for understanding the limitations from impedance; these limitations have direct impact on the choice of the machine configuration kept during operation (e.g. for deploying TCP-TCSG retractions in IR7 smaller than the present ones), or for optimising the design of future devices (e.g. as presently foreseen by the HL-LHC project, since outcomes are important ingredients for finalizing the baseline configuration of the upgraded collimation system).

With the technology improvements of analog-to-digital converters in terms of sampling rate and achievable resolution, direct digitization of beam signals is of growing interest in the field of beam diagnostics. The selection of a state-of-the-art analog-to-digital converter for such a task imposes a trade-off between sampling frequency and resolution. Understanding the dependency of the system performance on these features is fundamental. This paper presents an analysis and design methodology for such architectures. Analytical tools are used to guide the designer and to estimate the system performance as a function of the analog-to-digital converter performance. These estimations are then validated by Monte-Carlo simulations. As an example of this methodology an analysis for the next-generation electronics of the Large Hadron Collider beam position monitoring system is presented. The analytical model and the results obtained are discussed, along with comparisons to beam measurements obtained at the Large Hadron Collider., Proceedings of the 9th International Beam Instrumentation Conference, IBIC2020, Santos, Brazil

The CERN Super Proton Synchrotron (SPS) uses 215 beam position monitors (BPMs) to observe the beam orbit when accelerating protons or ions on a fast ramp cycle to beam energies of up to 450 GeV/c. In the frame of the CERN LHC Injector Upgrade (LIU) initiative the aged, and diffi- cult to maintain homodyne-receiver based BPM read-out system is currently being upgraded with A Logarithmic Po- sition System ¿ ALPS. As the name indicates, this new BPM electronics builds upon the experience at CERN with using logarithmic detector amplifiers for beam position processing, and is well suited to cover the large range of beam intensities accelerated in the SPS. The system will use radiation toler- ant electronics located in close proximity to the split-plane or stripline beam position monitor with GB/s optical data transmission to the processing electronics located on the surface. Technical details of the analog and digital signal processing, the data transmission using optical fibers, cal- ibration and testing, as well as first beam tests on a set of ALPS prototypes are presented in this paper., Proceedings of the 8th International Beam Instrumentation Conference, IBIC2019, Malmö, Sweden

Non-invasive diagnostics is essential to get important information about intense hadron beams, e.g. the transverse beam profile, which is indispensable in order to attain high brilliance and luminosity for upgrades on present machines and for future projects. Furthermore, it can be used to optimise parameter settings in environment of the running machine. An electron beam probe (EBP) is a beam diagnostics instrument which scans a low energy, low current electron beam through a hadron beam and obtains information from the detected response. The electrons are shot perpendicular through the hadron beam to be examined, which causes deflection in the beam potential of the intense hadron bunch, that needs to be detected and further analysed. We propose to build the EBP scanning apparatus for synchrotrons under ultra-high vacuum condition. The results of multi particle simulations evaluating limitations the expected measurement potential and limitations are presented. This work will be performed in collaboration with CERN., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The CERN Linear Electron Accelerator for Research (CLEAR) has now finished its second year of operation, providing a testbed for new accelerator technologies and a versatile radiation source. Hosting a varied experimental program, this beamline provides a flexible test facility for users both internal and external to CERN, as well as being an excellent accelerator physics training ground. The energy can be varied between 60 and 220 MeV, bunch length between 1 and 4 ps, bunch charge in the range 10 pC to 2 nC, and number of bunches in the range 1 to 200, at a repetition rate of 0.8 to 10 Hz. The status of the facility with an overview of the recent experimental results is presented., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

The Schottky monitors installed at the LHC enable the detection of Schottky noise of the two circulating proton / ion beams. From Schottky noise, beam parameters like tune, chromaticity, and relative emittance, can be extracted in a non-destructive and purely parasitic method of measurement. The primary goal of this MD was to study the Schottky monitors capability to reliably and accurately determine the beam chromaticities at injection energy. Furthermore, the possibility to track the beam emittance has been investigated.

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE), based at CERN, explores the use of a proton driven plasma wake-field to accelerate electrons at high energies over short distances. This paper introduces the Beam Position Measurement (BPM) system of the proton beamline and its performance. This BPM system is composed of 21 dual plane button pickups distributed along the 700m long transfer line from the CERN Super Proton Synchrotron (SPS) extraction point to beyond the plasma cell. The electrical pulses from the pickups are converted into analogue signals proportional to the intensity and displacement of the beam using logarithmic amplifiers, giving the system a high dynamic range (>50dB). These signals are digitized and processed by an FPGA-based front-end card featuring an ADC sampling at 40Msps. Each time a bunch is detected, the intensity and position data is sent over 1km of copper cable to surface electronics through a serial link at 10 Mbps. There, the data is further processed and stored. The dynamic range, resolution, noise and linearity of the system as evaluated from the laboratory and 2016 beam commissioning data will be discussed in detail., Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

This paper presents the development of an upgrade to the beam position interlock system for the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN). The beam orbit at the beam dump kicker is continuously monitored by 16 beam position monitors that are part of the machine protection system. In case of unacceptable orbit movement the system has to trigger the beam abort immediately to prevent damage to the machine. An upgrade of the present system is underway with the aim of handling a larger dynamic range of bunch intensities, and coping with different bunch time structures (both the standard bunch spacing of 25 ns and special doublet bunches spaced by 5 ns). The proposed architecture combines the analogue signals from opposite pickup electrodes on a single read-out channel, and stretches it with a delay-line based comb-filter. The resulting signal, covering a dynamic range of 60 dB, is digitised at 3.2 GSPS and processed inside a Field-programmable Gate Array (FPGA) to extract a position value. Different signal processing techniques are compared on simulated ideal beam signals, and preliminary results of a prototype installation is presented., Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

The CERN Super Proton Synchrotron (SPS) is a fast cycling hadron accelerator delivering protons with momenta of up to 450 GeV/c for the Large Hadron Collider (LHC), fixed target experiments and other users such as the AWAKE plasma acceleration experiment, and also used to accelerate heavy ions. This paper presents the upgrade initiative for the SPS beam position measurement system in the frame of the CERN LHC Injector Upgrade (LIU) project. The new SPS beam position read-out electronics will be based on logarithmic amplifiers, using signals provided by the 216 existing beam position monitors, the majority of which are based on split-plane 'shoebox' technology. It will need to cover a dynamic range sufficient to manage the wide range of SPS beam intensities and bunch formatting schemes to provide turn-by-turn and averaged beam orbits along the SPS acceleration cycles. In order to avoid long coaxial cables, the front-end electronics including the digitisation, will be located inside the accelerator tunnel, with optical transmission to surface processing electronics. This represents an additional challenge in terms of radiation tolerance of electronics components and materials., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

In order to achieve the highest beam intensities possible in the LHC the highest quality beam possible has to be supplied by the injector chain. The Super Proton Synchrotron (SPS) at CERN is the last accelerator in the injector chain of the LHC. One factor that is currently known to limit the intensity of the beam for injection to the LHC, is the longitudinal beam-coupling impedance in the SPS. One known source of multi-bunch instability is the vacuum flanges and campaigns to mechanically shield this source were completed in the year 2000. However, today it cannot be excluded that some of these shields may have partial or indeed full failures. Since these flanges are next to a QF magnet and are in most cases connected to a BPH (Beam Position Monitor Horizontal), it is possible to carry out via the BPH an in-situ measurement of the effectiveness of the shields. In this paper we present a methodology as well as measurement results taken with this non-intrusive in-situ method. From measurements, it is possible to identify if the flanges are without any impedance shield, equipped with either a fully functioning shield or a shield exhibiting non-ideal properties., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The objectives of the PACMAN* project are to improve the precision and accuracy of the alignment of accelerator components. Two steps of alignment are concerned: the fiducialisation, i.e. the determination of the reference axis of components w.r.t alignment targets, and the initial alignment of components on a common support assembly. The main accelerator components considered for the study are quadrupoles, 15 GHz BPM and RF structures from the Compact LInear Collider (CLIC) project. Different methods have been developed to determine the reference axis of these components with a micrometric accuracy, as well as to determine the position of this reference axis in the coordinate frame of the common support assembly. The tools and methods developed have been validated with success on dedicated test setups using CLIC components. This paper will provide a compilation of the main achievements and results obtained., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) at CERN aims to develop a proof-of-principle electron accelerator based on proton driven plasma wake-field acceleration. The core of AWAKE is a 10 metre long plasma cell filled with Rubidium vapour in which single, 400 GeV, proton bunches extracted from the CERN Super Proton Synchrotron (SPS) generate a strong plasma wakefield. The plasma is seeded using a femtosecond pulsed Ti:Sapphire laser. The aim of the experiment is to inject low energy electrons onto the plasma wake and accelerate them over this short distance to an energy of several GeV. To achieve its commissioning goals, AWAKE requires the precise measurement of the position and transverse profile of the laser, proton and electron beams as well as their temporal synchronisation. This contribution will present the beam instrumentation systems designed for AWAKE and their performance during the 2016 proton beam commissioning period., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The LHC Schottky monitors have the potential to measure and monitor some important beam parameters, tune, momentum spread, chromaticity and emittance, in a non-invasive way. We present recent upgrade and improvement efforts of the transverse LHC Schottky systems operating at 4.8 GHz. This includes optimization of the slotted waveguide pickups and a re-design of the RF front-end electronics to detect the weak, incoherent Schottky signals in presence of large, coherent beam harmonics., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

Resonant Cavity Beam Position Monitors (RF-BPMs) are diagnostic instruments capable of achieving beam position resolutions down to the nanometre scale. To date, their nanometric resolution capabilities have been predicted by simulation and verified through beam-based measurements with particle beams. In the frame of the PACMAN project at CERN, an innovative methodology has been developed to directly observe signal variations corresponding to nanometric displacements of the BPM cavity with respect to a conductive stretched wire. The cavity BPM of this R&D study operates at the TM110 dipole mode frequency of 15GHz. The concepts and details of the RF stretched wire BPM test-bench to achieve the best resolution results are presented, along with the required control hardware and software., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

For five of the LHC experiments the second p-Pb collision run planned in 2016 offered the opportunity to answer a range of important physics questions arising from the surprise discoveries (e.g., flow-like collective phenomena in small systems) made in earlier Pb-Pb, p-Pb and p-p runs. However the diversity of the physics and their respective capabilities led them to request very different operating conditions, in terms of collision energy, luminosity and pile-up. These appeared mutually incompatible within the available one month of operation. Nevertheless, a plan to satisfy most requirements was developed and implemented successfully. It exploited different beam lifetimes at two beam energies of 4 Z TeV and 6.5 Z TeV, a variety of luminosity sharing and bunch filling schemes, and varying beam directions. The outcome of this very complex strategy for repeated re-commissioning and operation of the LHC included the longest ever LHC fill with luminosity levelled for almost 38 h. The peak luminosity achieved exceeded the design value by a factor 7.8 and integrated luminosity substantially exceeded the experiments' requests., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

A transverse intra-bunch feedback system is currently under study at CERN for the SPS, to mitigate beam instabilities caused by electron clouds and coupled transverse modes (TMCI). This feedback system is designed for a bandwidth of 1 GHz, and based on a digital feedback controller and broadband power amplifiers. For the kicker, a periodic, quasi-TEM slotted transmission-line structure is foreseen which promises to meet the bandwidth requirements. This paper discusses the electromagnetic design and the mechanical implementation of a prototype kicker, demonstrating its performance and limitations based on numerical simulations., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

To achieve the luminosity goals in a next generation linear collider, acceleration and preservation of ultra-low emittance particle beams is mission critical and requires a precise alignment between the main accelerator components. PACMAN is an innovative doctoral training program, hosted by CERN, with the goal of developing high accuracy metrology and alignment methods and tools to integrate those components in a standalone, automatic test bench. The method will be validated on CLIC components, a proposed Compact Linear Collider currently studied at CERN. The alignment between the electrical center of the Beam Position Monitor (BPM) and the magnetic center of the associated Main Beam Quadrupole (MBQ) is of particular importance to minimize the emittance blow-up, and therefore in the focus of the PACMAN project. The two components have been independently characterized on separated test benches by stretched and vibrating wire techniques. Preliminary conclusions are presented in this paper, with emphasis on the characterization of the electrical center of the BPM., Proceedings of the North American Particle Accelerator Conf., NAPAC2016, Chicago, IL, USA

We propose a new solution to fiducialise the three major components of the CLIC collider: quadrupoles, beam-position monitors (BPM), and accelerating structures (AS). This solution is based on the use of a copper-beryllium (CuBe) wire to locate the reference position, i.e. the symmetry axes of the components (their magnetic, respectively electromagnetic centre axis), and to determine their position in the common support assembly defining a local coordinate system, with respect to the fiducials. These alignment targets will be used later to align the support assembly in the tunnel. With such a method, several accelerator components of different types, supported by a dedicated adjustment system, can be simultaneously fiducialised and pre-aligned using the same wire, enabling a micrometric accuracy with help of a 3D coordinate measurement machine (CMM). Alternative solutions based on frequency scanning interferometry (FSI) and micro-triangulation are also under development, to perform such fiducialisation and initial alignment directly in the tunnel after transport of the components on their common support. Complementary studies have also been undertaken on the development of a new seismic sensor, on a high-stiffness nano-positioning system with a millimetre stroke, on miniature rotating search coils, and on the extrapolation of the uncertainties of measurements considering variations of temperature. These developments are part of the PACMAN project (a study on Particle Accelerator Components’ Metrology and Alignment to the Nanometre scale), an innovative Doctoral Programme, where 10 PhD students hosted at CERN work towards their PhD thesis. The methods and tools being developed are presented in this paper, as well as the first results obtained.

The interplay between head-on beam-beam interaction and external sources of noise can be a significant source of emittance growth, especially when considering large beam-beam tune shifts as for the HL-LHC upgrade project. In this experiment the emittance growth of colliding bunches with different brightness and therefore different beam-beam parameters in the presence of an external white noise source with different amplitudes is measured for different gains of the transverse feedback.

PACMAN, a study on Particle Accelerator Components' Metrology and Alignment to the Nanometre scale, is an Innovative Doctoral Program, funded by the European Commission, hosted by CERN. The objective is to propose new methods allowing the determination of the reference axis of accelerator components with respect to external alignment targets. A test bench, using real components of the Compact Linear Collider (CLIC) study, will demonstrate the feasibility of the solutions developed with micrometric accuracy. The study concerns the methods developed using a stretched wire to determine the magnetic axis of small aperture magnets, the electrical centre of a 15 GHz RF-BPM or the electro-magnetic axis of an accelerating cavity. Solutions are also carried out to measure the position of the wire with respect to the external alignment targets, using a 3D Coordinate Measuring Machine or portable alternatives based on Frequency Scanning Interferometry or micro-triangulation. Other systems developed are also taken into account: a nano-positioning system to validate the nanometric resolution of the BPM and a dedicated seismic sensor to characterize the environment during the measurements., Proceedings of the 4th International Beam Instrumentation Conference, IBIC2015, Melbourne, Australia

The beam alignment requirements for the next generation of lepton colliders have become increasingly challenging. As an example, the alignment requirements for the three major collider components of the CLIC linear collider are as follows. Before the first beam circulates, the Beam Position Monitors (BPM), Accelerating Structures (AS)and quadrupoles will have to be aligned up to 10 μm w.r.t. a straight line over 200 m long segments, along the 20 km of linacs. PACMAN is a study on Particle Accelerator Components' Metrology and Alignment to the Nanometre scale. It is an Innovative Doctoral Program, funded by the EU and hosted by CERN, providing high quality training to 10 Early Stage Researchers working towards a PhD thesis. The technical aim of the project is to improve the alignment accuracy of the CLIC components by developing new methods and tools addressing several steps of alignment simultaneously, to gain time and accuracy. The tools and methods developed will be validated on a test bench. This paper presents the technical systems to be integrated in the test bench, the results of the compatibility tests performed between these systems, as well as the final design of the PACMAN validation bench., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

In collaboration with LAPP and IFIC, two units of a prototype stripline Beam Position Monitor (BPM) for the CLIC Drive Beam (DB), and its associated readout electronics have been successfully installed and tested in the Two-Beam-Module (TBM) at the CLIC Test Facility 3 (CTF3) at CERN. This paper gives a short overview of the BPM system and presents the performance measured under different Drive Beam configurations., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

For the Compact LInear Collider (CLIC) project at CERN, maintaining low emittance beams, as they are transported along the two independent 10-20 km long main linacs, is crucial. The beam trajectory therefore has to be very well aligned to the magnetic centre of the quadrupole magnets. A series of microwave cavity beam position monitors (BPM) is foreseen to detect the position of the beam along the main linacs to precisely monitor the beam trajectory in the circular beam pipe of only 8 mm diameter. The PACMAN project aims to demonstrate the pre-alignment of the magnetic field of a main CLIC quadrupole with the electro-magnetic centre of a 15 GHz RF-BPM to the required sub-micron accuracy. This paper focuses on stretched-wire measurements of a CLIC Test Facility (CTF) cavity BPM, to locate its electrical centre. Details of two measurement methods are discussed: RF signal excitation of the wire and analysis of RF signal transfer through the slot-coupled waveguides of the cavity, using the stretched wire as a passive target. This contribution will present the theory behind these measurements, their electromagnetic analysis and first, preliminary experimental results., Proceedings of the 4th International Beam Instrumentation Conference, IBIC2015, Melbourne, Australia

The CLIC project, currently under study at CERN is an electron-positron collider at 3 TeV centre-of-mass energy and luminosity of 2*1034 cm⁻²s^{−1}. Achieving such luminosity requires a beam dimension of 1 nm in the vertical plane and high beam stability. The TD24 is a traveling wave structure operating at 12 GHz designed to reach 100 MV/m at constant gradient. It consists of two coupling cells and 24 disks. The RF is coupled from cell to cell though an iris of 5.5 mm. To minimize the occurrence of wake-fields and minimize the emittance growth Δεy below 5%, the pre-alignment precision of the electrical centre of the accelerating structure (AS) on its support has to be better than 7 μm. Following, the AS is actively aligned with beam using the wake-field monitor (WFM) signals, with a resolution of 3.5 μm. A test bench for laboratory measurements has been designed and exploits the asymmetry created by RF scattering parameters of an off-centre conductive wire, stretched to locate the electromagnetic centre of the AS. Simulations and preliminary measurement results are presented., Proceedings of the 4th International Beam Instrumentation Conference, IBIC2015, Melbourne, Australia

The main beam of the Compact LInear Collider (CLIC) requires the beam trajectory to be measured with 50 nm spatial resolution. It also requires a time resolution capable of making position measurements of the head and tail of the 156 ns long CLIC bunch train, for use in dispersion free steering based on an energy chirp applied along the train. For this purpose, a stainless steel 15 GHz cavity BPM prototype has been manufactured, installed at the CLIC Test Facility (CTF3) and tested with beam. An improved design has been fabricated from copper. We discuss results from the two types of the prototype pickups, both from laboratory tests and from beam tests. We also cover the development of the new downconverter electronics., Proceedings of the 4th International Beam Instrumentation Conference, IBIC2015, Melbourne, Australia

The LHC Schottky system allows the measurement of beam parameters such as tune and chromaticity in an entirely non-invasive way by extracting information from the statistical fluctuations in the incoherent motion of particles. The system was commissioned in 2011 and provided satisfactory beam-parameter measurements during LHC run 1 for lead-ions. However, for protons its usability was substantially limited due to strong interfering signals originating from the coherent motion of the particle bunch. The system has recently been upgraded with optimized travelling-wave pick-ups and an improved 4.8~GHz microwave signal path, with the front-end and the triple down-mixing chain optimized to reduce coherent signals. Design and operational aspects for the complete system are shown and the results from measurements with LHC beams in Run II are presented and discussed., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The main objective of this MD was to record Schottky spectra under well known machine conditions. In summary, 7 set-points for the chromaticity and 8 for the emittance have been established and Schottky spectra have been recorded for each setting. The data will be used to benchmark and develop different fitting algorithms. This note presents the initial attempt of curve-fitting and discusses its shortcomings.

This paper presents the preliminary electromagnetic design of a stripline Beam Position Monitor (BPM) for the High Luminosity program of the Large Hadron Collider (HL-LHC) at CERN. The design is fitted into a new octagonal shielded Beam Screen for the low-beta triplets and is optimized for high directivity. It also includes internal Tungsten absorbers, required to reduce the energy deposition in the superconducting magnets. The achieved broadband directivity in wakefield solver simulations presents significant improvement over the directivity of the current stripline BPMs installed in the LHC., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA