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ALBA is currently equipped with two x-ray pinhole cameras for continuous beam size monitoring using the synchrotron radiation from two different bending magnets. The first pinhole was installed in day-1 and it is working properly since 2012 as the work-horse for the ALBA emittance measurements, while the second one has been commissioned in beginning 2021 for redundancy purposes. This paper summarizes the exercises to characterize the Point Spread Function (PSF) of both pinhole cameras using analytical calculations, SRW simulations, and experimental measurements using the beam lifetime., Proceedings of the 11th International Beam Instrumentation Conference, IBIC2022, Kraków, Poland

"Fast Monte-CarlO approach to Coherence of Undulator Sources" (FOCUS) is a new GPU-based code to compute the transverse coherence of X-ray radiation from undulator sources. The code relies on scaled dimensionless quantities and analytic expressions of the electric field emitted by electrons in an undulator, obtained in the frequency domain under paraxial approximation (justified by the assumption of ultra-relativistic electrons) and free space propagation, with the addition of the resonance approximation. We describe the core structure of the code, which exploits GPUs for massively parallel computations. We validate our approach by direct comparison with SRW (Synchrotron Radiation Workshop) simulations. The benchmarks prove that FOCUS yields similar results with respect to SRW, while at the same time reducing the computation times by five orders of magnitude. Finally, we show examples of applications to beam size diagnostics. The aim of the code is to fast evaluating the transverse coherence properties of undulator X-ray radiation as a function of the electron beam parameters, and to support and help preparing more rigorous numerical simulations with traditional codes like SRW., Proceedings of the 11th International Beam Instrumentation Conference, IBIC2022, Kraków, Poland

At ALBA Synchrotron each of the two in-air pinhole imaging systems is able to see several beam spots at once due to specific pinhole grid with 3x3 holes placed in the path of the X-ray fan. Each beam image has its own properties, such as source pinhole aperture size, its Point Spread Function (PSF) and copper filter thickness, all of which impact the electron beam size calculation. Until now, these parameters were applied manually to the pinhole device servers for numerical image analysis, so this semi-manual beam size calculator is subject to frequent adjustments and human monitoring. This study looks at feasibility of training and pointing an Artificial Neural Network (ANN) at image stream coming from pinhole cameras in real time, track all detected beam spots and analyze them, with the end goal to automate the whole pinhole beam image processing., Proceedings of the 10th International Beam Instrumentation Conference, IBIC2021, Pohang, Rep. of Korea

We report on 2D beam size measurements with a novel interferometric technique named Heterodyne Near Field Speckles, capable of resolving few-micrometer beam sizes. It relies on the interference between the weak spherical waves scattered by a colloidal suspension and the intense transilluminating X-ray beam. Fourier analysis of the resulting speckles enables full 2D coherence mapping of the incoming radiation, from which the beam sizes along the two orthogonal directions are retrieved. We show experimental results obtained with 12.4 keV X-rays at the NCD-SWEET undulator beamline at ALBA, where the vertical beam size has been changed between 5 and 15 micrometers by varying the beam coupling. The results agree well with the estimated beam sizes from the pinhole calculations. Finally, we discuss recent investigations on alternative targets aimed at improving the signal-to-noise ratio of the technique., Proceedings of the 10th International Beam Instrumentation Conference, IBIC2021, Pohang, Rep. of Korea

The Heterodyne Near Field Speckles (HNFS) is a special type of interferometry technique where radiation is scattered by nanoparticles suspended in a medium. The scattered waves and the transmitted radiation form an interference pattern, which is modulated by the spatial coherence of the radiation and by the scattering properties of the nanoparticles. The superposition of many such interference patterns results in a speckle pattern, from which the spatial coherence of the radiation and thus the transverse beam profile can be determined. In this contribution we present approaches for simulating the HNFS patterns from hard X-ray radiation and compare then with data from experiments at the ALBA synchrotron., Proceedings of the 9th International Beam Instrumentation Conference, IBIC2020, Santos, Brazil

ALBA is equipped with two different current transformers (FCT and DCCT), and a third one (ICT) is now in design stage to be installed in 2019. A comparative study of the different currents transformers was carried out in order to characterize their contribution to longitudinal and transverse impedance. The gap in the vacuum chamber of the current transformers was varied in order to study its effect on the heat deposited by the beam in the corresponding device and on the resonance in the longitudinal impedance spectrum. The simulation results are compared to the experience with the existing current transformers in operation., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

Experiments using the heterodyne near field speckle method (HNFS) have been performed at ALBA to characterize the spatial coherence of the synchrotron radiation, with the ultimate goal of measuring both the horizontal and vertical electron beam sizes. The HNFS technique consists on the analysis of the interference between the radiation scattered by a colloidal suspension of nanoparticles and the synchrotron radiation, which in this case corresponds to the hard x-rays (12keV) produced by the in-vacuum undulator of the NCD-Sweet beamline. This paper describes the fundamentals of the technique, possible limitations, and shows the first experimental results changing the beam coupling of the storage ring., Proceedings of the 8th International Beam Instrumentation Conference, IBIC2019, Malmö, Sweden

We present the recent developments of a study aiming at measuring the transverse beam profile using the Heterodyne Near Field Speckles (HNFS) method. The HNFS technique consists of a suspension of nanoparticles suspended in a liquid and illuminated by synchrotron radiation (either in the visible or in X-ray wavelength range). The transverse coherence of the source, and therefore, under the conditions of validity of the Van Cittert and Zernike theorem, the transverse electron beam size is retrieved from the interference between the transmitted beam and the spherical waves scattered by each nanoparticle. We here describe the fundamentals of this technique, as well as the recent experimental results obtained with 12 keV radiation at the NCD beamline at ALBA. The applicability of such technique for future accelerators (e.g. CLIC or FCC) is also discussed., Proceedings of the 7\textsuperscript{th} Int. Beam Instrumentation Conf., IBIC2018, Shanghai, China

Analyzing streak camera images of the beam injected into a Storage Ring with no RF voltage allows calculating several parameters, like the energy loss per turn and the energy mismatch between injected and stored beams. These measurements are based on the analysis of the centroid drift path of a bunch as it spirals inwards, changing its rotation period. This drift is clear and measurable in single and multi-bunch modes in several horizontal sweep speeds of the streak. With this technique we also measure the momentum compaction factor and observe its change with respect to the insertion devices’ open/closed states. The obtained values are comparable with theoretical expectations, as well as with values measured by other means., Proceedings of the 7\textsuperscript{th} Int. Beam Instrumentation Conf., IBIC2018, Shanghai, China

The non-invasive diagnostics in the ALBA Booster-to-Storage (BTS) transfer consist of Beam Position Monitors (BPM) and Synchrotron Radiation Monitors (SRM), which together provide position, size and shape of the beam. However, they were not reliable enough for a systematic improvement of the transfer efficiency in the BTS, which has been fluctuating since day one. In order to optimize it, two major upgradse have been performed: first, the BPM electronics have been upgraded for single-pass beam detection, showing a factor 10 better position resolution than the former units. Secondly, the SRMs mechanics and automation were significantly improved to provide a more robust optics alignment. Both BPMs and SRMs are now routinely used to keep transmission efficiency along the BTS constant over weeks., Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

Strip line Beam Positions Monitors (BPMs) are the main devices used for non-intercepting position measurement for the electron LINAC of ELI-NP (Extreme Light Infrastructure - Nuclear Physics). All the 29 BPMs have the same design, with the exception of the one installed in one of the dump line, which has a much larger acceptance than the others. BPMs will also be used to measure the charge of the beam, by measuring the sum of the pickups signals and calibrating it with beam charge monitors installed along the LINAC. An analytical model has been developed for the proposed BPMs. This model has been checked by means of PIC/wakefield simulations, in order to obtain the pickups signals at the passage of the beam and to study the effects of BPMs non-linearities, particularly on charge measurements. Details of the analytical model, results of the numerical simulations and the correction algorithm proposed for charge measurements are described in this paper., Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

Transverse Couple Bunch Instabilities (TCBI) have been identified at ALBA as one of the main beam current limitations since its early commissioning in 2011. In these last years, we have developed several diagnostics tools that allow us a better characterization of these instabilities. The Synchrotron Radiation Interferometry has been equipped with a Fast Gated Camera (FGC) to measure the bunch-by-bunch beam size evolution, which, in combination with the diagnostics tools of the Transverse Multibunch Feedback system, provides us with a fruitful insight of these phenomena. This paper describes these diagnostics tools, and as an example, compares the emittance and tune evolution switching on/off some of the vacuum pumps at the Storage Ring., Proceedings of the 6th Int. Beam Instrumentation Conf., IBIC2017, Grand Rapids, MI, USA

In this paper we extensively describe the heterodyne near field speckle method (HNFS) to characterize both spatial and temporal coherence of synchrotron radiation (SR). The method relies on Fourier analysis of near field speckles generated by scattering from nanoparticles suspended in a liquid. A criterion based on master curves of power spectra is introduced and validated by measurements on the visible light produced by the ALBA bending dipole. While spatial coherence measurements with HNFS have been reported, we present for the first time measurements of the temporal coherence of SR wavefronts with the HNFS method both for narrowband and white light beams. In the former case, using a band-pass filter, a coherence time of 40±10 fs is measured, in good agreement with the expected value of 43 fs for the filter inverse linewidth. Moreover, by exploiting the self-reference scheme of the technique, we show that coherence areas propagate carrying nonvanishing curvature. In the latter case, the measured coherence time of the incident SR without any monochromator is 1.6±0.4 fs, corresponding to a bandwidth of 240 nm at a peak wavelength of 350 nm. Exploiting the Wiener-Kintchine theorem, we also retrieve the SR power spectral density at the sample position from the measured temporal coherence function. Results are in good agreement with the measurements performed using a standard spectrometer, yielding a coherence time of 1.4 fs.

The streak camera has been used to measure the bunch length since the ALBA storage ring commissioning in 2011. Previously, we developed an optical calibration system based on the Michelson interferometry. Similar to the work at the DLS*, in this report we show the calibration kit based on the different electrical delays which can be used via rf switches. We compare both calibration systems and we show measurements of the longitudinal impedance obtained with the new calibration., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

During 5 years of operation in the 3 GeV storage ring of ALBA, the 124 beam loss monitors (BLM) have provided stable measurements of relative losses around the machine, with around 10% breakdown of units. We have analyzed these BLM failures and correlated the integrated received dose with any special conditions of each BLM location which might have led to their breakdown. We also show studies of beam losses in the insertion devices, with particular attention to the results in the multipole wiggler (MPW), where the vacuum chamber is (suspected to be) misaligned and high BLM counts are detected., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

The advanced source of Gamma-ray photons will be soon built near Bucharest (Romania) by an European consortium (EurogammaS) led by INFN, as part of the ELI-NP (Extreme Light Infrastructure-Nuclear Physics). It will generate photons by Compton back-scattering in the collision between a multi-bunch electron beam, at a maximum energy of 720 MeV, and a high intensity recirculated laser pulse. An S-Band photo-injector and the following C-band Linac, which are under construction, will operate at 100Hz repetition rate with macro pulses of 32 electron bunches, separated by 16ns and with 250pC nominal charge. Stripline and cavity BPMs will be installed along the linac, in order to measure both the position and charge of the electron beam. Stripline BPM response can be considered linear within a limited area around the BPM origin. In order to use the full BPM acceptance area, without accuracy losses due to non-linearities, we plan to use correction algorithms, developed on the basis of simulations and measurements of BPMs response. In particular, suitable high-order surface polynomials will be used., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

In this work we describe a novel beam diagnostic method based on coherence characterization of broad-spectrum bending magnet radiation through the Heterodyne Near Field Scattering (HNFS) technique. HNFS is a self-referencing technique based on the interference between the transmitted beam and the spherical waves scattered by each particle of a colloidal suspension. The resulting single-particle interferogram shows circular fringes modulated by the spatio-temporal Complex Coherence Factor (CCF) of the radiation. Superposition of a number of these patterns results in a stochastic speckle field, from which spatial and temporal coherence information of the source can be retrieved in near field conditions. Here we describe the basics of this technique, the experimental setup mounted along the hard X-ray pinhole at the ALBA synchrotron light source, and the possibility of transverse electron beam size retrieval from the spatial coherence function of the emitted dipole radiation. We also show preliminary results concerning power spectral density of visible synchrotron radiation as obtained from temporal coherence., Proceedings of the 5th Int. Beam Instrumentation Conf., IBIC2016, Barcelona, Spain

We have developed a 2D finite element-based software for Matlab to study non-resonant effects in BPMs of arbitrary geometry, in particular the geometric nonlinearities. The developed code called BpmLab utilizes an open-source tetrahedral mesh generator DistMesh, combined with a short implementation of FEM with linear basis functions to find the electrostatic field distribution for boundary electric potential excitation. The BPM response as a function of beam position is calculated in a single simulation for all beam positions using the potential ratios, according to the Green's reciprocity theorem. The code offers ways to correct the geometrical nonlinear distortion, either by polynomials or by direct inversion of the electrode signals through numerical optimization. This work is an overview of the BpmLab capabilities to date, including its extensive benchmarking and validation against other methods, Proceedings of the 4th International Beam Instrumentation Conference, IBIC2015, Melbourne, Australia

A methodology has been developed to perform electrical characterization of the stripline BPMs for the future Gamma Beam System of ELI Nuclear Physics facility in Romania. Several prototype units are extensively benchmarked and the results are presented in this paper. The BPM sensitivity function is determined using a uniquely designed motorized test bench with a stretched wire to measure the BPM response map. Here, the BPM feedthroughs are connected to Libera Brilliance electronics and the wire is fed by continuous wave signal, while the two software-controlled motors provide horizontal and vertical motion of the BPM around the wire. The electrical offset is obtained using S-parameter measurements with a Network Analyzer (via the "Lambertso" method) and is referenced to the mechanical offset., Proceedings of the 4th International Beam Instrumentation Conference, IBIC2015, Melbourne, Australia

Collimators with embedded beam position monitor (BPM) button electrodes will be installed in the Large Hadron Collider (LHC) during the current long shutdown period. For the subsequent operation, BPMs will allow the collimator jaws to be kept centered around the beam orbit. In this manner, a better beam cleaning efficiency and machine protection can be provided at unprecedented higher beam energies and intensities. A collimator alignment algorithm is proposed to center the jaws automatically around the beam. The algorithm is based on successive approximation and takes into account a correction of the nonlinear BPM sensitivity to beam displacement and an asymmetry of the electronic channels processing the BPM electrode signals. A software implementation was tested with a prototype collimator in the Super Proton Synchrotron. This paper presents results of the tests along with some considerations for eventual operation in the LHC., peer-reviewed

This Report gives a full description of the ELENA Ring to be built within the circumference of the Antiproton Decelarator (AD) Ring, in Building 193 at CERN. The ELENA ring will further decelerate the antiprotons coming from the AD at the momentum of 100 MeV/c down to 13.7 MeV/c, which corresponds to the kinetic energy of 100 keV before extracting to the physics experiments in the same building. The history of such an extra low energy antiproton ring at CERN goes a long way back, and even to the Decelerator’s previous incarnation, the Low Energy Antiproton Ring (LEAR), which came into operation in 1983. Already at that time, there were physics’ requests to further decelerate the antiprotons expected from LEAR by proposals for ELENA. Appendix I illustrates the cover pages of two such CERN documents from 1982.

The CERN LHC is equipped with two Synchrotron Radiation Monitor (BSRT) systems used to characterise transverse and longitudinal beam distributions. Since the end of the 2011 LHC run the light extraction system, based on a retractable mirror, has suffered deformation and mechanical failure that is correlated to the increase in beam intensity. Temperature probes have associated these observations to a strong heating of the mirror support with a dependence on the longitudinal bunch length and shape, indicating the origin as electromagnetic coupling between the beam and the structure. This paper combines all this information with the aim of characterising and improving the system in view of its upgrade during the current LHC shutdown. Beam-based observations are presented along with electromagnetic and thermomechanical simulations and complemented by laboratory measurements, including the study of the RF properties of different mirror bulk and coating materials.

This report describes aperture measurements in the IR8 triplet region performed during the MD block 4 on 29 of November 2012. The goal was to determine whether the available aperture in the triplets is sufficient to apply a two-dimensional separation scheme for the future 25 ns runs of the LHC. The limiting plane for the intended separation scheme is the vertical one. For the measurement, proton beams at 450 GeV in the injection optics configuration were used. The vertical separation bump is increased until losses are observed. To obtain independent measurements in both triplets additional bumps from the outer corrector magnets have been used, generated by YASP. Measurements have been done with and without horizontal crossing angle.

Beams of cooled antiprotons at keV energies shall be provided by the Ultra-low energy Storage Ring (USR) at the Facility for Low energy Antiproton and Ion Research (FLAIR) and the Extra Low ENergy Antiproton ring (ELENA) at CERN's Antiproton Decelerator (AD) facility. Both storage rings put challenging demands on the beam position monitoring (BPM) system as their capacitive pick-ups should be capable of determining the beam position of beams at low intensities and low velocities, close to the noise level of state-of-the-art electronics. In this contribution we describe the design and anticipated performance of BPMs for low-energy ion beams with a focus on the ELENA orbit measurement systems. We also present the particular challenges encountered in the numerical simulation of pickup response at very low beta values. Finally, we provide an outlook on how the implementation of faster algorithms for the simulation of BPM characteristics could potentially help speed up such studies considerably.

The Large Hadron Collider (LHC) has now been operated successfully for 3 years relying on the good performance of its beam instrumentation, including position and tune monitors and their respective feedback systems. This contribution gives an overview of the performance and limitations of the current orbit and tune systems. The major hardware and software modifications performed in 2012 are presented as well as the developments and improvements planned during the Long Shutdown 1 (LS1). The last part of the paper discusses the expected performances of both systems with 6.5TeV beams after LS1.

At present the beam based alignment of the LHC collimators is performed by touching the beam halo with the two jaws of each device. This method requires dedicated fills at low intensities that are done infrequently because the procedure is time consuming. This limits the operational flexibility in particular in the case of changes of optics and orbit configuration in the experimental regions. The system performance relies on the machine reproducibility and regular loss maps to validate the settings. To overcome these limitations and to allow a continuous monitoring of the beam position at the collimators, a design with in-jaw beam position monitors was proposed and successfully tested with a mock-up collimator in the CERN-SPS. Extensive beam experiments allowed to determine the achievable accuracy of the jaw alignment for single and multi-turn operation. In this paper the results of these experiments are discussed. The measured alignment accuracy is compared to the accuracies achieved with the present collimators in the LHC., peer-reviewed

The transverse beam emittances of the LHC proton and ion beams can be inferred by measuring the beam sizes with Wire Scanner (WS), Synchrotron Radiation (BSRT) and Beam Gas Ionization (BGI) monitors. The Abort Gap Monitor (AGM) and the Longitudinal Density Monitor (LDM) are used to characterize the longitudinal distributions. This paper covers at first all aspects related to the use of such devices in 2012. Achieved performances, reliability and operational limitations, like system failures due to high intensity beams or ageing are covered. A particular emphasis is given to the planned system upgrades for improving accuracy and robustness, while coping with both the operational limits and the LHC energy and intensity upgrades after LS1. This includes the impact of the 25 ns bunch spacing on the bunch per bunch measurements and the need for resolving smaller beam sizes at 7 TeV.

Next gen­er­a­tion of the LHC col­li­ma­tors will be equipped with but­ton beam po­si­tion mon­i­tors (BPMs) em­bed­ded into the col­li­ma­tor jaws. Such a so­lu­tion will im­prove the ac­cu­ra­cy of the jaw align­ment with respect to the beam and re­duce the beam time nec­es­sary for the collima­tor setup. This paper de­scribes re­sults of elec­tro­mag­net­ic simu­la­tions of the jaw BPMs per­formed with the CST Par­ti­cle Stu­dio suite, aimed at char­ac­ter­i­sa­tion of the BPMs as well as the simulation soft­ware it­self. The re­sults are com­pared to the mea­sure­ments ob­tained with beam on a pro­to­type sys­tem in­stalled in the CERN SPS.

Since June 2011 the rapid increase of the luminosity performance of the LHC has come at the expense of both increased temperature and pressure of specific, near-beam, LHC equipment. In some cases, this beam induced heating has caused delays while equipment cool-down, beam dumps and even degradation of some devices. This contribution gathers the observations of beam induced heating, attributed to longitudinal beam coupling impedance, their current level of understanding and possible actions planned to be implemented during the 1st LHC Long Shutdown (LS1) in 2013-2014.

After the 2011 run, actions were put in place during the 2011/2012 winter stop to limit beam induced radio frequency (RF) heating of LHC components. However, some components could not be changed during this short stop and continued to represent a limitation throughout 2012. In addition, the stored beam intensity increased in 2012 and the temperature of certain components became critical. In this contribution, the beam induced heating limitations for 2012 and the expected beam induced heating limitations for the restart after the Long Shutdown 1 (LS1) will be compiled. The expected consequences of running with 25 ns or 50 ns bunch spacing will be detailed, as well as the consequences of running with shorter bunch length. Finally, actions on hardware or beam parameters to monitor and mitigate the impact of beam induced heating to LHC operation after LS1 will be discussed.

Collimators with embedded Beam Position Monitor (BPM) buttons will be installed in the LHC during the upcoming long shutdown period. During the subsequent operation, the BPMs will allow the collimator jaws to be kept centered around the beam trajectory. In this manner, the best possible beam cleaning efficiency and machine protection can be provided at unprecedented higher beam energies and intensities. A collimator alignment algorithm is proposed to center the jaws automatically around the beam. The algorithm is based on successive approximation, as the BPM measurements are affected by non-linearities, which vary with the distance between opposite buttons, as well as the difference between the beam and the jaw centers. The successful test results, as well as some considerations for eventual operation in the LHC are also presented., peer-reviewed