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The precise determination of the luminosity is essential for many analyses in physics based on the data from the particle accelerator Large Hadron Collider (LHC) at CERN. There are different types of detectors used for the luminosity measurements. The focus of this review is on luminosity measurements with hybrid-pixel detectors and the progress made over the past decade. The first generations of detectors of the Medipix and Timepix families had frame-based readout, while Timepix3 has a quasi-continuous readout. The applications of the detectors are manifold, and in particular, the detectors have been operated in the harsh environment of the LHC. The excellent performance in detecting high fluxes of elementary particles made these detectors ideal tools to measure the delivered luminosity resulting from proton–proton collisions. Important aspects of this review are the performance improvements in relative luminosity measurements from one detector generation to another, the long-term stability of the measurements, absolute luminosity measurements, material activation (radiation-induced) corrections, and the measurement of luminosity from neutron counting. Rather than bunch-average luminosity provided by previous detector generations, owing to the excellent time-resolution, Timepix3 measured the luminosity of individual proton bunches that are 25 ns apart. This review demonstrates the large progress in the precision of luminosity measurements during LHC Run-1 and Run-2 operations using hybrid-pixel detectors, and thus their importance for luminosity measurements in the future of LHC operations.

Integrated circuits sensitive to both total ionizing dose (TID) and displacement damage (DD) effects can exhibit degradation profiles resulting from a combination of degradation mechanisms induced by both effects. This work presents circuit simulations based on experimental data to explain degradation mechanisms induced by combined TID and DD effects on a bipolar IC current source. First, the effect of the degradation of each internal transistor on the circuit’s response is evaluated by applying electrical parametric changes. Then simulations are performed from different degradation scenarios based on observed circuit behaviors to reproduce the different TID, DD, and combined TID–DD responses. These simulations show that a synergistic interaction between a current leakage induced by DD on a transistor located in the bandgap reference part with the gain degradation of a current mirror induced by both TID and DD appears to be responsible for the combined TID–DD response. It is also shown that the circuit degradation rate depends on the DDD/TID rate ratios encountered during the exposition.

Coating of surfaces facing particle beams with high-temperature superconductors (HTS) for reducing the beam coupling impedance is being considered for the next generation of hadron colliders, such as the FCC-hh at CERN, where HTS would be exposed to the high-frequency wakefields generated by the particle bunches and to the strong field of the steering magnets. In this frame, we present a simple model for the calculation of the microwave response of HTS exposed to a strong external magnetic field, which takes into account the nonlinearity of the pinning potential of the vortex lattice. The equation of motion of the vortex lattice is solved in first-order approximation, and we calculate the amplitude of the third-harmonic components in the electric field produced by vortex oscillation. We deduce the time-dependent surface impedance, which could serve as a boundary condition in the simulation codes for the calculation of beam-stability phenomena in particle accelerators. Finally, time-integration of the surface impedance allows exploring the dependence of the surface impedance on surface currents, useful for analyzing the experimental results obtained using simple resonators in terms of our model.

The investigations of multilayer surface nanostructures characteristics was performed with synchrotron radiation sources, characterized by an intensive, calculated continuum. It plays an important role in nanoelectronics metrological base. The main research were carried out at electron storage rings «Siberia-1» (Kurchatov Institute) and MLS (PTB, Berlin) with low electron energy, in a wide wavelength range, including visible range, AUV, VU, EUV and to exclude the X-ray radiation influence. The methods of the radiometers, photodiodes, filters and multilayer mirrors characteristics measurements are based on the synchrotron radiation absolute spectral characteristics and accelerated electrons number variation. The metrological investigations with synchrotron radiation was concentrated on: – absolute spectral responsivety of silicon photodiodes with multilayer filters for integral radiometers applications; – spectral transmittances of surface layers of photodiodes in the extreme ultraviolet region; – spectral reflectance coefficient of superlattice. The characteristics of photodiodes and filters on a synchrotron radiation source are measured using a monochromator and a reference detector. The use of a synchrotron radiation channel makes it possible to study the spectral transmittance of thin films and multilayer structures formed in the in situ mode. To form multilayer nanostructures directly on the receiving surface of photodetectors, an ion-plasma sputtering module is used. The optical scheme of the channel provides for the possibility of using monochromators of grazing incidence for the range of photon energies from 25 to 100 ev and normal incidence for the range of photon energies from 4 to 25 ev. At a photon energy of 40 ev, the absolute spectral sensitivity was 70 ma / W for a photodiode with a surface multilayer filter applied. To develop an experimental technique for measuring the spectral reflection coefficient of multilayer mirrors, and to create standard samples, the Mo/Si system was studied. Computer modeling of multi-layer coatings allows us to calculate the optical characteristics of superlattices in the extreme ultraviolet region. The obtained results of measurements of the spectral reflection coefficient of a multilayer coating in the photon energy range of 65–100 ev indicate a resonance reflection character with a max-imum at an energy of 83.5 ev and an energy width at a half-height of about 6.5 ev. The working wave-length of the reflecting mirror corresponds to the calculated one, which confirms the effectiveness of the adopted model.

The transient current technique (TCT) is widely used in the field of silicon particle detector development. So far, only laser wavelengths with a photon energy larger than or similar to the silicon bandgap (single photon absorption) were used. Recently, measurements using two-photon absorption (TPA) for silicon detector testing have been carried out for the first time. Excess carriers are only created at the focal point of the laser beam and thus resolution in all three spatial directions could be achieved. The resolution perpendicular to the incident laser beam could be increased roughly by a factor of 10. First measurements using this new method were performed at the Singular Laser Facility of Universidad del País Vasco (UPV)/Euskal Herriko Unibertzitatea (EHU). Following the initial success of the method, a compact TPA-TCT setup is under development. A first description of the setup and laser system is presented in this article., This work was supported in part by the Spanish Ministry of Economy and Competitiveness (MINECO) under Grant FPA2013-48387-C6-1-P and in part by the Wolfgang Gentner Programme of the German Federal Ministry of Education and Research under Grant 05E15CHA.

Radiation detectors need front-end electronics capable of measuring currents over a large dynamic range with femtoampere sensitivity. The goal of this work is to find an alternative to the legacy systems implemented using discrete components or technology nodes of 350 nm or higher. The 130 nm technology is evaluated on its leakage current performance to assess its employability in such applications. A comparative analysis of three low current measurement topologies, namely the charge balancing, reset counting, and direct slope measurement methods, is carried out and their performance in different current ranges is evaluated. The charge balancing method was found to provide a better dynamic range with greater accuracy. However, in the lower current range, the direct slope measurement method was found to give faster results than the other two methods with comparable accuracy. Also, an application-specific integrated circuit implementing the charge balancing method was found to be linear throughout the dynamic range of −1 fA to $-1\,\,\mu \text{A}$ and could measure currents with an accuracy of ±7%. This achievement in the 130 nm technology opens the way to using the high-speed digital cells offered by this technology in conjunction with the low-leakage transistors to design a high-speed accurate current measurement system.

The application of high-temperature superconductors to accelerator magnets for future particle colliders is under study. Numerical methods are crucial for an accurate evaluation of the complex dynamical behavior of the magnets, especially concerning the magnetic field quality and thermal behavior. We present a coupled $\textbf{A}$-$\textbf{H}$ field formulation for the analysis of magneto-thermal transients in accelerator magnets. The magnetic field strength $\textbf{H}$ accounts for the eddy current problem in the source regions containing the superconducting domains, while the magnetic vector potential $\textbf{A}$ represents the magnetoquasistatic problem in the normal and non-conducting domains. Furthermore, we include a slab approximation for the source regions, making the formulation suitable for large scale models composed of thousands of tapes. In this work, the relevant equations are derived and discussed, with emphasis on the coupling conditions. The weak formulation is derived, and numerical results are provided in order to both, verify the formulation and scale it to the size of an accelerator magnet., Comment: 10 pages, 11 figures

A wind-and-react MgB 2 solenoid magnet for klystrons has been developed. While the current normal-conducting (Cu) magnet consumes 20 kW per magnet, this MgB$_2$ magnet consumes less than 3 kW in refrigerator power. The conduction-cooled half coil of the magnet is 337 mm in inner diameter; the winding pack, 19.4 mm wide × 136.6 mm high, uses 2.7 km of 10 filament circular conductor, which is insulated with glass 0.83 mm in diameter, and is reacted after being wound onto a stainless steel bobbin. The coil has Cu plates of 0.2 mm in thickness between each coil layer and on the inner and outer sides. The magnet has two coils and produces 0.8 T in the center and its stored energy is 11.8 kJ. Together with the above-mentioned coil structure, these coils can consume stored energy in itself at quench without a special quench protection system. A performance test of the magnet was successful.

Continuous developments in additive manufacturing (AM) technology are opening up opportunities in novel machining, and improving design alternatives for modern particle accelerator components. One of the most critical, complex, and delicate accelerator elements to manufacture and assemble is the radio frequency quadrupole (RFQ) linear accelerator, which is used as an injector for all large modern proton and ion accelerator systems. For this reason, the RFQ has been selected by a wide European collaboration participating in the AM developments of the I.FAST (Innovation Fostering in Accelerator Science and Technology) Horizon 2020 project. The RFQ is as an excellent candidate to show how sophisticated pure copper accelerator components can be manufactured by AM and how their functionalities can be boosted by this evolving technology. To show the feasibility of the AM process, a prototype RFQ section has been designed, corresponding to one-quarter of a 750 MHz 4-vane RFQ, which was optimised for production with state-of-the-art laser powder bed fusion (L-PBF) technology, and then manufactured in pure copper. To the best of the authors’ knowledge, this is the first RFQ section manufactured in the world by AM. Subsequently, geometrical precision and surface roughness of the prototype were measured. The results obtained are encouraging and confirm the feasibility of AM manufactured high-tech accelerator components. It has been also confirmed that the RFQ geometry, particularly the critical electrode modulation and the complex cooling channels, can be successfully realised thanks to the opportunities provided by the AM technology. Further prototypes will aim to improve surface roughness and to test vacuum properties. In parallel, laboratory measurements will start to test and improve the voltage holding properties of AM manufactured electrode samples. Continuous developments in Additive Manufacturing (AM) technologies are opening opportunities in novel machining, and improving design alternatives for modern particle accelerator components. One of the most critical, complex, and delicate accelerator elements to manufacture and assemble is the Radio Frequency Quadrupole (RFQ) linear accelerator, used as an injector for all large modern proton and ion accelerator systems. For this reason, the RFQ has been selected by a wide European collaboration participating in the AM developments of the I.FAST (Innovation Fostering in Accelerator Science and Technology) Horizon 2020 project. RFQ is as an excellent candidate to show how sophisticated pure-copper accelerator components can be manufactured by AM and how their functionalities can be boosted by this evolving technology. To show the feasibility of the AM process, a prototype RFQ section has been designed, corresponding to one-quarter of a 750 MHz 4-vane RFQ, which was optimised for production with state-of-art Laser Powder Bed Fusion (L-PBF) technology, and then manufactured in pure copper. To the best knowledge of the authors, this is the first RFQ section manufactured in the world by AM. Subsequently, geometrical precision and surface roughness of the prototype were measured. The results obtained are encouraging and confirm the feasibility of AM manufactured high-tech accelerator components. It has been also confirmed that the RFQ geometry, in particular the critical electrode modulation and the complex cooling channels, can be successfully realised thanks to the opportunities provided by the AM technology. Further prototypes will aim to improve surface roughness and to test vacuum properties. In parallel, laboratory measurements will start to test and improve the voltage holding properties of AM manufactured electrode samples.

Electron cooling is a fundamental process to guarantee the beam quality in low energy antimatter facilities. In extra low energy antiproton, the electron cooler reduces the emittance blowup of the antiproton beam and thus delivers a focused and bright beam to the experiments at the unprecedentedly low kinetic energy of 100 keV. In order to achieve a cold beam at this low energy, the electron gun of the cooler must emit a monoenergetic and relatively intense electron beam. An optimization of the extra low energy antiproton electron cooler gun involving a cold cathode is studied, with the aim of investigating the feasibility of using carbon nanotubes (CNTs) as cold electron field emitters. CNTs are considered among the most promising field emitting material. However, stability data for emission operation over hundreds of hours, as well as lifetime and conditioning process studies to ensure optimal performance, are still incomplete or missing, especially if the purpose is to use them in operation in a machine such as extra low energy antiproton. This manuscript reports experiments that characterize these properties and ascertain whether CNTs are reliable enough to be used as cold electron field emitters for many hundreds of hours.

We describe a laser-plasma platform for photon-photon collision experiments to measure fundamental quantum electrodynamic processes such as the linear Breit-Wheeler process with real photons. The platform has been developed using the Gemini laser facility at the Rutherford Appleton Laboratory. A laser wakefield accelerator and a bremsstrahlung convertor are used to generate a collimated beam of photons with energies of hundreds of MeV, that collide with keV x-ray photons generated by a laser heated plasma target. To detect the pairs generated by the photon-photon collisions, a magnetic transport system has been developed which directs the pairs onto scintillation-based and hybrid silicon pixel single particle detectors. We present commissioning results from an experimental campaign using this laser-plasma platform for photon-photon physics, demonstrating successful generation of both photon sources, characterisation of the magnetic transport system and calibration of the single particle detectors, and discuss the feasibility of this platform for the observation of the Breit-Wheeler process. The design of the platform will also serve as the basis for the investigation of strong-field quantum electrodynamic processes such as the nonlinear Breit-Wheeler and the Trident process, or eventually, photon-photon scattering. We describe a laser–plasma platform for photon–photon collision experiments to measure fundamental quantum electrodynamic processes. As an example we describe using this platform to attempt to observe the linear Breit–Wheeler process. The platform has been developed using the Gemini laser facility at the Rutherford Appleton Laboratory. A laser Wakefield accelerator and a bremsstrahlung convertor are used to generate a collimated beam of photons with energies of hundreds of MeV, that collide with keV x-ray photons generated by a laser heated plasma target. To detect the pairs generated by the photon–photon collisions, a magnetic transport system has been developed which directs the pairs onto scintillation-based and hybrid silicon pixel single particle detectors (SPDs). We present commissioning results from an experimental campaign using this laser–plasma platform for photon–photon physics, demonstrating successful generation of both photon sources, characterisation of the magnetic transport system and calibration of the SPDs, and discuss the feasibility of this platform for the observation of the Breit–Wheeler process. The design of the platform will also serve as the basis for the investigation of strong-field quantum electrodynamic processes such as the nonlinear Breit–Wheeler and the Trident process, or eventually, photon–photon scattering.

Crossing the transition energy is always a delicate process, representing a potential source of strong perturbations of the dynamics of charged particle beams in a hadron circular accelerator. Since the first generation of multi-GeV rings, intense studies have been devoted to understanding the possible harmful mechanisms involved in transition crossing and to devise mitigation measures. Nowadays, several circular particle accelerators are successfully operating across the transition energy and this process is well mastered. In a completely different context, stable resonances of the traverse phase space have been proposed as new means of manipulating charged particle beams. While the original aim of such a proposal was multi-turn extraction from the CERN Proton Synchrotron to the Super Proton Synchrotron, many more applications have been proposed and studied in detail. In this paper, the two topics, i.e. transition crossing and stable resonances, have been brought together with the goal of providing a novel and non-adiabatic approach to perform a clean transition crossing. The idea presented here is that by judiciously using sextupoles and octupoles it is possible to generate stable islands of the horizontal phase space. These islands represent a second closed orbit whose properties can be selected independently of those of the standard, i.e. central, closed orbit. This provides a means of performing a non-adiabatic change of the transition energy experienced by the charged particles by displacing the beam between the two closed orbits. Crossing the transition energy is always a delicate process, representing a potential source of strong perturbations of the dynamics of charged particle beams in a hadron circular accelerator. Since the first generation of multi-GeV rings, intense studies have been devoted to understanding the possible harmful mechanisms involved in transition crossing and to devise mitigation measures. Nowadays, several circular particle accelerators are successfully operating across transition and this process is well mastered. In a completely different context, stable resonances of the traverse phase space have been proposed as new means of manipulating charged particle beams. While the original aim of such a proposal was multi-turn extraction from the CERN Proton Synchrotron to the Super Proton Synchrotron, many more applications have been proposed and studied in detail. In this paper, the two topics, i.e. transition crossing and stable resonances, have been brought together with the goal of providing a novel and non-adiabatic approach to perform a clean transition crossing. The idea presented here is that by judiciously using sextupoles and octupoles it is possible to generate stable islands of the horizontal phase space. These islands represent a second closed orbit whose properties can be selected independently of those of the standard, i.e. central, closed orbit. This provides a means of performing a non-adiabatic change of the transition energy experienced by the charged particles by displacing the beam between the two closed orbits.

The precise knowledge of the magnetic field produced by dipole magnets is critical to the operation of a synchrotron. Real-time measurement systems may be required, especially in the case of iron-dominated electromagnets with strong non-linear effects, to acquire the magnetic field and feed it back to various users. This work concerns the design and implementation of a new measurement system of this kind currently being deployed throughout the European Organization for Nuclear Research (CERN) accelerator complex. We first discuss the measurement principle, the general system architecture and the technology employed, focusing in particular on the most critical and specialized components developed, that is, the field marker trigger generator and the magnetic flux integrator. We then present the results of a detailed metrological characterization of the integrator, including the aspects of drift estimation and correction, as well as the absolute gain calibration and frequency response. We finally discuss the latency of the whole acquisition chain and present an outline of future work to improve the capabilities of the system.

The first mention of the impedance concept appeared on November 1966 in the CERN internal report "Longitudinal instability of a coasting beam above transition, due to the action of lumped discontinuities" by V.G. Vaccaro. This was the beginning of many studies, which took place over the last five decades, and today, impedances and wake fields continue to be an important field of activity, as concerns theory, simulation, bench and beam-based measurements. Building a reliable impedance or wake field model of a machine is the first necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics nonlinearities, transverse damper, noise, space charge, electron cloud, beam-beam (in a collider), etc. Beam collective instabilities, and their mitigation, cover a wide range of effects in particle accelerators and they have been the subjects of intense research. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all these intricate phenomena, as it is very often not possible to treat the different effects separately. With the increasing power of our computers this becomes easier but the need to continue and develop theories remains, to have a better understanding of the interplays between all these effects: the subject of impedance and beam instabilities in particle accelerators is far from being exhausted, as testified by the many new instability and stabilizing mechanisms which have been recently explained or discovered. Furthermore, in the context of the studies for possible future accelerators, some uncharted territories remain such as, for instance, the collective instabilities during the necessary ionization cooling for a muon collider., 24 pages, 23 figures, to be published in JINST (special Issue: ICFA Beam Dynamics Newsletter No. 82)

The Large Hadron electron Collider (LHeC) is a proposed future particle-physics project colliding 60 GeV electrons from a six-pass recirculating energy-recovery linac (ERL) with 7 TeV protons stored in the LHC. The ERL technology allows for much higher beam current and, therefore, higher luminosity than a traditional linac. The high-current, high-energy electron beam can also be used to drive a free electron laser (FEL). In this study, we investigate the performance of an LHeC-based FEL, operated in the self-amplified spontaneous emission mode using electron beams after one or two turns, with beam energies of, e.g., 10, 20, 30 and 40 GeV, and aim at producing x-ray pulses at wavelengths ranging from 8 to 0.5 Å. In addition, we explore a possible path to use the 40 GeV electron beam for generating photon pulses at much lower wavelengths, down to a few picometer. We demonstrate that such ERL-based high-energy FEL would have the potential to provide orders of magnitude higher average brilliance at Å wavelengths than any other FEL either existing or proposed. It might also allow a pioneering step into the picometer wavelength regime. The Large Hadron electron Collider (LHeC) is a proposed future particle-physics project colliding 60 GeV electrons from a six-pass recirculating energy-recovery Linac (ERL) with 7 TeV protons stored in the LHC. The ERL technology allows for much higher beam current and, therefore, higher luminosity than a traditional Linac. The high-current, high-energy electron beam can also be used to drive a free electron laser (FEL). In this study, we investigate the performance of an LHeC-based FEL, operated in the self-amplified spontaneous emission mode using electron beams after one or two turns, with beam energies of, e.g., 10, 20, 30 and 40 GeV, and aim at producing X-ray pulses at wavelengths ranging from 8~Å to 0.5~Å . In addition, we explore a possible path to use the 40 GeV electron beam for generating photon pulses at much lower wavelengths, down to a few picometre. We demonstrate that such ERL-based high-energy FEL would have the potential to provide orders of magnitude higher average brilliance at Å wavelengths than any other FEL either existing or proposed. It might also allow a pioneering step into the picometre wavelength regime.

Particle accelerators are among the most complex instruments conceived by physicists for the exploration of the fundamental laws of nature. Of relevance for particle physics are the high-energy colliders, such as the CERN Large Hadron Collider (LHC), which hosts particle physics experiments that are probing the Standard Model predictions and looking for signs of physics beyond the standard model. This paper presents a review of the recent Machine Learning activities carried out on beam measurements performed at the CERN Large Hadron Collider. This paper has been accepted for publication in IEEE Instrumentation and Measurement Magazine and in the published version no abstract is provided.

In the framework of the High-Luminosity Large Hadron Collider (HL-LHC) project, larger and shielded beam screens will be installed in the beam pipe of the superconducting magnets of the insertion next to the ATLAS and CMS detectors. The beam screen is a complex assembly that guarantees the vacuum requirements while shielding the magnet cold mass from the induced heat loads. Such an assembly has to withstand high intensity electromagnetic forces induced during magnet quenches. The mechanical stability was verified in a dedicated quench test campaign performed at the magnet test station of CERN. Strain gauges, custom-made probes, and optical fibers were installed in the beam screen to measure deformations during a quench. Magnetic field measurements were also carried out by means of pick-up coils mounted within the assembly. The main outcomes of this work are the elastic behaviour of the beam screen after 52 quenches and a satisfactory agreement between measurements and simulations.

Η παρούσα διδακτορική διατριβή εστιάζει στο φαινόμενο χωρικού φορτίου παρουσία βητατρονικών συντονισμών στους επιταχυντές του Ευρωπαϊκού Κέντρου Πυρηνικών Ερευνών (CERN) και πιο συγκεκριμένα στο σύγχροτρο πρωτονίων (PS) και στο σύγχροτρο πρωτονίων booster (PSB). Το φαινόμενο χωρικού φορτίου είναι το κυρίαρχο φαινόμενο για τη δυναμική σε επιταχυντές υψηλής λαμπρότητας και χαμηλής ενέργειας, όπως οι επιταχυντές που μελετήθηκαν. Αποτελεί τον κύριο περιορισμό για την αποδοτικότητά τους κατά την λειτουργία. Στον PS, απώλειες παρατηρούνται για βητατρονικές συχνότητες μεγαλύτερες από Qy=6.25, κυρίως για δέσμες με ισχυρό φαινόμενο χωρικού φορτίου. Η παρούσα εργασία δείχνει ότι αυτή η συμπεριφορά οφείλεται σε συντονισμούς που εγείρονται από το φαινόμενο χωρικού φορτίου εξαιτίας της υψηλής συμμετρικότητας του PS, τυπικό χαρακτηριστικό των συγχρότρων πρώτης γενιάς. Προσομοιώσεις αποδεικνύουν ότι ο συντονισμός που παρατηρείται όταν Qy=6.25 είναι μη συνεκτικός. Ο αναλυτικός υπολογισμός των όρων οδήγησης συντονισμού (RDT) που προέρχονται από το δυναμικό του φαινομένου χωρικού φορτίου καταδεικνύει ότι οι συχνότητες λειτουργίας του PS περιβάλλεται από πολλαπλούς μη συνεκτικούς συντονισμούς εξαιτίας του φαινομένου χωρικού φορτίου. Αντίστοιχα, μελέτες ανάλυσης και χαρτογράφησης του χώρου των συχνοτήτων (FMA) δείχνουν την οδήγηση των συντονισμών και αποκαλύπτουν ότι ο μηχανισμός που οδηγεί στις παρατηρούμενες απώλειες είναι η περιοδική διάσχιση των συντονισμών. Πειραματικές μελέτες και προσομοιώσεις δείχνουν την απόκριση των δεσμών υψηλής λαμπρότητας στην PS στους συντονισμούς καταγράφοντας τις απώλειες και την αύξηση της εκπεμπτικότητας. Η χρήση δεσμών μικρότερη λαμπρότητας επιτρέπει τον προσδιορισμό και την αντιστάθμιση συντονισμών που οφείλονται σε σφάλματα στον επιταχυντή. Τέλος, μετρήσεις και προσομοιώσεις σε συντονισμούς οφειλώμενους είτε σε σφάλματα είτε στο φαινόμενο χωρικού φορτίου καταδεικνύουν τη διαφορετική συμπεριφορά των απωλειών με βάση την λαμπρότητα της δέσμης και την πηγή της διέγερσής τους. Το τελευταίο μέρος της διατριβής παρουσιάζει μελέτες στον PSB, και συγκεκριμένα για τον συντονισμό Montague, συντονιμός εγειρόμενος από το φαινόμενο χωρικού φορτίου που προκαλεί σύζευξη των εγκάρσιων πεδίων της κίνησης. Η αναλυτική προσέγγιση του υπολογισμού των RDT φανερώνει ότι η μηχανή θα μπορούσε να λειτουργεί σε ένα διαφορετικό χώρο συχνοτήτων, Q4Q3, όπου ο συντονισμός καταστέλλεται. Μετρήσεις και προσομοιώσεις με διαφορετικές ταχύτητες διέλευσης του συντονισμού, φανερώνουν ανταλλαγή εκπεμπτικοτήτων στον σύνηθες χώρο λειτουργίας, Q4Q4, ενώ η καταστολή του συντονισμού στον χώρο Q4Q3 φανερώνεται με την διατήρηση της εκπεμπτικότητας και στα δύο εγκάρσια πεδία της κίνησης κατά τη διέλευση του συντονισμού. Ο συντονισμός Montague μελετήθηκε και σε συνδυασμό με γραμμικούς συντονισμούς που προκαλούν σύζευξη της κίνησης και εγείρονται από σφάλματα στον επιταχυντή σε μετρήσεις και προσομοιώσεις.

The combination of oscillation data collection with fixed-target microchips for regular crystal dispersion is an efficient method for collecting serial crystallography data at synchrotrons. Background scatter from noncrystal substrates is especially minimized., A fixed-target approach to high-throughput room-temperature serial synchrotron crystallography with oscillation is described. Patterned silicon chips with microwells provide high crystal-loading density with an extremely high hit rate. The microfocus, undulator-fed beamline at CHESS, which has compound refractive optics and a fast-framing detector, was built and optimized for this experiment. The high-throughput oscillation method described here collects 1–5° of data per crystal at room temperature with fast (10° s−1) oscillation rates and translation times, giving a crystal-data collection rate of 2.5 Hz. Partial datasets collected by the oscillation method at a storage-ring source provide more complete data per crystal than still images, dramatically lowering the total number of crystals needed for a complete dataset suitable for structure solution and refinement – up to two orders of magnitude fewer being required. Thus, this method is particularly well suited to instances where crystal quantities are low. It is demonstrated, through comparison of first and last oscillation images of two systems, that dose and the effects of radiation damage can be minimized through fast rotation and low angular sweeps for each crystal.

The LHC collimation system must adopt materials with excellent thermal shock resistance, high electrical conductivity, geometrical stability, and radiation hardness. Two novel composites, Molybdenum–Carbide–Graphite and Copper–Diamond, are proposed for the LHC collimation upgrade. A postirradiation examination was performed to assess the status of the composites, tested under intense proton beam impacts at the CERN HiRadMat facility. Metrology measurements, computed tomography, and 3D topography allowed to evaluate the localized spallation induced by the beam. This article provides an overview of the thermophysical characterization of the two composites before irradiation and nondestructive postirradiation results.

Traditional heavy-ion testing for single-event effects is carried out in cyclotron facilities with energies around 10 MeV/n. Despite their capability of providing a broad range of linear energy transfer (LET) values, the main limitations are related to the need of testing in a vacuum and with the sensitive region of the components accessible to the low range ions. In this paper, we explore the use of ultrahigh energy (UHE) (5-150 GeV/n) ions in the CERN accelerator complex for radiation effects on electronics testing. At these energies, we show, both through simulations and experimental data, the significant impact of the ion energy on the ionization track structure and associated volume-restricted LET value, highlighting the possible limitations for radiation hardness assurance for high-energy accelerator applications. In addition, we show that from a nuclear interaction perspective, UHE ions behave similar to protons independently of their significantly larger mass.

Accelerators magnets must have minimal magnetic field imperfections to reduce particle-beam instabilities. In the case of coils made of high-temperature superconducting (HTS) tapes, the magnetization due to persistent currents adds an undesired field contribution, potentially degrading the magnetic field quality. In this paper we study the use of superconducting screens based on HTS tapes for reducing the magnetic field imperfections in accelerator magnets. The screens exploit the magnetization by persistent currents to cancel out the magnetic field error. The screens are aligned with the main field component, such that only the undesired field components are compensated. The screens are self-regulating, and do not require any externally applied source of energy. Measurements in liquid nitrogen at 77 K show for dipole-field configurations a significant reduction of the magnetic field error up to a factor of four. The residual error is explained via numerical simulations accounting for the geometric defects in the HTS screens, achieving satisfactory agreement with experimental results. Simulations show that if screens are increased in width and thickness, and operated at 4.5 K , field errors may be eliminated almost entirely for the typical excitation cycles of accelerator magnets.

The LHC Injector Upgrade (LIU) was launched in 2010 in synergy with the High Luminosity LHC (HL-LHC) project.^2) It includes the consolidation/upgrade of the PS Booster RF systems:^3,4) all the existing ferrite-loaded RF cavities are being replaced with wideband RF systems during the 2019–2020 long shut down. The magnetic-annealed cores improve the cavity performance and reduce the number of the straight sections for RF systems. In 2013, during the first long shut down of the LHC, LS1, we performed a beam loading test in J-PARC using a one-cell type Booster cavity. The beam test using a high intensity beam proved that direct-feedback can work in conjunction with the other beam loading compensation system.^5) J-PARC also cooperates on the R&D; of a Rad-Hard solid-state amplifier. A recent irradiation test shows that the amplifier can withstand up to 2 kGy under mixed field irradiation.^6) J-PARC contributions for the LIU project will be reported.

HiRadMat is a unique user facility providing a controlled test environment for accelerator experiments investigating the effects of high energy, high intensity proton beam. HiRadMat uses a 440 GeV/c proton beam fastly-extracted from the CERN SPS and can currently provide a maximum pulse intensity of 3.5 × 10^13 protons. Initially designed to explore the damage thresholds of accelerator components which experienced thermal shocks induced by high-brightness beams, HiRadMat has continued to advance into new areas of research. This contribution will focus on the significant role that HiRadMat plays in Targetry R&D; where previous experiments will be discussed and future ideas presented. Due to the extensive CERN support available experiments at HiRadMat have evolved from new target concepts (like powder target and prototype material sample experiments) to validation studies for full-scale prototypes, including absorber jaws for LHC and HL-LHC, collimator’s and spallation targets, and more recently cryogenic and pre-irradiated sample experiments. Similarly, diagnostics (e.g., strain gauges, LDVs, temperature sensors) as well as visual inspection and beam monitoring devices (e.g., radiation hard cameras, lighting systems, microphones) have continued to develop providing users with in-situ beam-time statistics and beam profile information resulting in more accurate measurements of the prompt-beam effects. The future upgrade of HiRadMat will be discussed with details on multiple stages of development from improved functionality of the laboratory to optimisation of the experimental area regarding beam potential.

The achromatic telescopic squeezing (ATS) scheme has brought an essential conceptual foundation to the HL-LHC project, making possible a strong and clean (achromatic) reduction of ${\ensuremath{\beta}}^{*}$, an important parameter with respect to which several HL-LHC sub-systems were dimensioned (e.g., the 150 mm aperture of the new inner triplet quadrupoles) or justified (crab-cavities for mitigating the geometric luminosity loss factor at low ${\ensuremath{\beta}}^{*}$ and subsequent large crossing-angle). The basic mechanics of the scheme is shortly reminded, highlighting as well some of its by-products (Landau damping, long-range beam-beam mitigation with octupoles), and a recent improvement which made possible an early, but still partial, implementation of ATS optics in the LHC for the 2017 and 2018 LHC physics runs. The main focus of the paper will be on the experimental validation of the scheme, via the development of dedicated machine configurations and high-intensity beam tests which took place in Run 2. The paper will conclude on the configuration presently in mind to operate the LHC during its third exploitation period (Run 3), while trying to ensure a smooth enough transition toward the HL-LHC, in terms of optics, beam parameters, and dedicated beam manipulations (${\ensuremath{\beta}}^{*}$-leveling).

The Large Hadron-electron Collider (LHeC) at CERN is a design study in the context of the LHC luminosity upgrade project, HL-LHC, to establish electron-proton/nucleus collisions with centre-of-mass energies in the TeV regime and luminosities in the order of 10^34𝑐𝑚−2𝑠−1. It implies the construction of an energy recovery linac in racetrack configuration to provide an intense 50 GeV electron beam that will collide with the HL-LHC hadron beams. Such an energy recovery racetrack could also be used at the Future Circular Collider, the FCC-eh, with even higher centre-of-mass energies and similar luminosities. In this paper we will review the status of the project with focus on the accelerator design progress, based on the updated thorough LHeC design report, published in March 2020.

The HL-LHC interaction region magnet triplets (Q1,Q2, and Q3) will be composed of superconducting Nb3Sn quadru-poles. The MQXF quadrupole protection system is based on CLIQ (Coupling-Loss Induced Quench system) and outer layer quench heaters.This paper reports a summary of quench heaters to coil high voltage tests performed on MQXF short and long coils in air after fabrication, and in air and He gas after magnet training. Breakdown voltage values demonstrate good marginwith respect to the Electrical design criteria for the HL-LHC inner triplet mag-nets. A modification in thequench heater installation-with an ex-tra layer of fiber glass between the coil and the quench heater trace-has been proposed and tested in a mirror magnet to further increase electrical margins. Results demonstrated improvements of high voltage margin at the expense of a clear increase of hot spot temperature.Thebaseline heater to coil insulation was assessed to be able to guarantee safe operation for the Nb3Sn quadrupole mag-nets for the interaction regions of HL-LHC. The HL-LHC interaction region magnet triplets (Q1, Q2, and Q3) will be composed of superconducting Nb3Sn quadrupoles. The MQXF quadrupole protection system is based on CLIQ (Coupling-Loss Induced Quench system) and outer layer quench heaters. This paper reports a summary of quench heaters to coil high voltage tests performed on MQXF short and long coils in air after fabrication, and in air and He gas after magnet training. Breakdown voltage values demonstrate good margin with respect to the Electrical design criteria for the HL-LHC inner triplet magnets. A modification in the quench heater installation- with an extra layer of fiber glass between the coil and the quench heater trace- has been proposed and tested in a mirror magnet to further increase electrical margins. Results demonstrated improvements of high voltage margin at the expense of a clear increase of hot spot temperature. The baseline heater to coil insulation was assessed to be able to guarantee safe operation for the Nb3Sn quadrupole magnets for the interaction regions of HL-LHC.

This work has been supported in part by the FEDER/Junta de Andalucia Project Grant P18-FRJ-3735 and by the UK Science and Technology Facilities Council (STFC) Grant ST/P001246/1. Funding for open access charge: Universidad de Granada/CBUA., We review the projected sensitivity to physics beyond the Standard Model via indirect searches at the Future e + e- Circular Collider (FCC-ee). The indirect sensitivity to new physics is discussed both from a model-independent perspective, using the formalism of Effective Field Theories, but also from the point of view of more specific classes of well-motivated models., FEDER/Junta de Andalucia Project P18-FRJ-3735, UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) ST/P001246/1

Dissertation, RWTH Aachen University, 2021; Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen, Diagramme (2021). = Dissertation, RWTH Aachen University, 2021, The JEDI collaboration is currently performing a direct measurement of the Electric Dipole Moment (EDM) of charged particles with beams of polarized protons and deuterons, using the COoler SYnchrotron (COSY) at the Forschungszentrum Jülich in Germany. For the precision EDM search, the JEDI collaboration is aiming for an experimental target with systematic errors of the same order of magnitude as the statistical sensitivity of10−29 e cm per year of data acquisition. The Magnetic Dipole Moment (MDM) is many orders of magnitude larger than the EDM. If the beam trajectory in the storage ring deviates from the nominal trajectory, this can cause the particles to move through a radial magnetic field. As a result of the interaction with the MDM, this leads to spin precessions which are indistinguishable from a true EDM signal. Therefore, it is important that the beam orbit be very close to the magnetic center ofthe focusing elements in the ring. The RMS deviation of the orbit from the nominal orbit should be as close to zero as possible. This means that the Beam Position Monitors(BPMs) must have a suitable sensitivity that meets the goals of the EDM experiment up to the desired accuracy level.In this work, a novel compact inductive BPM based on a segmented toroidal coil (Rogowski coil) has been developed. Various aspects of this Rogowski BPM as a non destructive monitor for measuring the transverse beam coordinates were investigated. The theoretical model describing the induced voltages of the Rogowski BPM was extended using the "lumped model" approximation to obtain a more realistic description ofthe measurement of the induction signals. In this extended model, the coupling between individual quadrant coils was considered. Further theoretical studies were performed to investigate the effect of the angular overlap of the winding on the electrical response. Also, the sensitivity of the beam positions to the specifics of the windings of the segments was investigated. Electromagnetic simulations performed in COMSOL Multiphysics were used to investigate a simple 3D model for the Rogowski BPM. Simulations were performed in bothtime and frequency domains. Different boundary conditions were applied on individual quadrants to investigate the electrical properties of the coils. Another simplified model describing a single quadrant coil in the Rogowski BPM was developed assuming a 2Daxisymmetric geometry. In this analysis, the impedance and the inductance of the single coil were studied over a frequency range of 10MHz.Several hardware developments and improvements, starting from a simple ring coilup to the complete BPM with its feed throughs, flanges and connectors, were achieved. Developments on the laboratory test bench enabled more accurate calibrations. Thenewly developed cylindrical knife-edge structure was used to study the behavior ofthe stepper motor drives with a laser tracker, and absolute BPM calibration (with anaccuracy of a few micrometers) is possible after the BPMs are installed in the accelerator. Calibration measurements for the Rogowski BPM were performed in the test bench and compared with the theoretical model. A good agreement between the measurement results and the theoretical expectations was achieved. Various experimental investigations were carried out in the laboratory, such as theme asurement of the frequency response, the measurement of the position response, the measurement of the stability of the resonance curves, as well as the tuning of there sonance curves with shunt capacitors, the measurement of the time variations of the electrical signals, as well as the effect of the wave form of the excitation source on the BPM calibration, the possibility of using the BPM as a BCT, and the distribution of the Signal to Noise Ratio (SNR). In addition, the effect of the geometric specifications of the windings, the way the whole circuit is connected, and the system’s Self Resonant Frequency (SRF) on the position resolution at different frequencies were also investigated. Two Rogowski BPMs with different geometrical and electrical characteristics were developed and successfully installed and tested in COSY. They were installed at the entrance and exit of the Radio Frequency Wien Filter (RF WF). The results of local orbit bumps introduced around the RF WF showed reasonable and linear position responses measuredby the two BPMs. A resolution of up to 400 nm was achieved with the Rogowski BPMs (for a single position measured at 750 kHz during a sampling time of 1s, a system’s SRF of 3.229 MHz and aparticle intensity of 5 × 109). This corresponds to an order of magnitude improvementin resolution compared to typical capacitive BPMs used in COSY. Moreover, with thenewly proposed method for absolute instrument calibration, and taking into account the accuracy of the stepper drives used for calibration, as well as the errors caused by temporal drifts, the accuracy of the Rogowski BPMs is expected to be about 20 µm (errorof three standard deviations, corresponding to a beam off-centered by 1 cm), which constitutes an improvement by a factor of five compared to typical BPMs., Published by RWTH Aachen University, Aachen

IEEE transactions on magnetics 57(2), 6100105 (2021). doi:10.1109/TMAG.2020.3005722, Published by IEEE, New York, NY

Very high energy electron (VHEE) beams have been proposed as an alternative radiotherapy modality to megavoltage photons; they penetrate deeply without significant scattering in inhomogeneous tissue because of their high relativistic inertia. However, the depth dose distribution of a single, collimated VHEE beam is quasi-uniform, which can lead to healthy tissue being overexposed. This can be largely overcome by focusing the VHEE beam to a small spot. Here, we present experiments to demonstrate focusing as a means of concentrating dose into small volumetric elements inside a target. We find good agreement between measured dose distributions and Monte Carlo simulations. Focused radiation beams could be used to precisely target tumours or hypoxic regions of a tumour, which would enhance the efficacy of radiotherapy. The development of new accelerator technologies may provide future compact systems for delivering these focused beams to tumours, a concept that can also be extended to X-rays and hadrons. Very high energy electrons (VHEE) penetrate deeply in tissues and can provide an alternative to photon irradiation for tumour treatment. Using VHEE beams at CERN Linear Electron Accelerator for Research (CLEAR) focused into a water phantom, the authors demonstrate on-axis dose enhancement at a depth of 5–6 cm, proving that such beams can produce dose concentration to small volume elements, hence limiting the effect on adjacent healthy tissues if used for radiotherapy.

Machine learning entails a broad range of techniques that have been widely used in Science and Engineering since decades. High-energy physics has also profited from the power of these tools for advanced analysis of colliders data. It is only up until recently that Machine Learning has started to be applied successfully in the domain of Accelerator Physics, which is testified by intense efforts deployed in this domain by several laboratories worldwide. This is also the case of CERN, where recently focused efforts have been devoted to the application of Machine Learning techniques to beam dynamics studies at the Large Hadron Collider (LHC). This implies a wide spectrum of applications from beam measurements and machine performance optimisation to analysis of numerical data from tracking simulations of non-linear beam dynamics. In this paper, the LHC-related applications that are currently pursued are presented and discussed in detail, paying also attention to future developments., peer-reviewed

The electron lens in the Fermilab Integrable Optics Test Accelerator (IOTA) will enable new research in nonlinear integrable optics, space-charge compensation, electron cooling, and the stability of intense beams. This research addresses scientific questions on high-brightness beams and operational challenges of high-power accelerators for nuclear and particle physics. We review the roles that electron lenses play in this field and the physical principles behind their applications. The design criteria and specifications for the IOTA storage ring and electron lens are then discussed. We conclude with a description of the components of the apparatus.

The radar method for remote detection at large distances of radiation pollution in the atmosphere and on the Earth’s surface is considered. The design of radar for determine of radioactive formations in the atmosphere and near the Earth surface is developed. In the developed radar for increase the efficiency of detection and identification of the composition of radioactive contaminants, the antennas are divided into transmitting and receiving. This allowed for the detection of radiation contamination microwave signal with a tunable wavelength. The fiber-optic communication system is used to transmit signals from receiving antennas. The results of investigations of radioactive pollution in the atmosphere are presented.

International audience; The Compact Linear Collider (CLIC) could provide $e^+e^−$ collisions in two detectors simultaneously possibly at a bunch train frequency in the linac twice the baseline design value. In this paper, a novel dual beam delivery system (BDS) design is presented in order to serve two interaction regions (IR1 and IR2) including optics designs and the evaluation of luminosity performance with synchrotron radiation (SR) and solenoid effects for both energy stages of CLIC, 380 GeV and 3 TeV. IR2 features a larger crossing angle than the current baseline. The luminosity performance of the novel CLIC scheme was evaluated by comparing the different BDS designs with and without the detector solenoid field effects. It has to be highlighted that the impact of the detector solenoid on luminosity had not been evaluated for the current CLIC baseline, which amounts to a loss of about 4% that corresponds to the same value of the old baseline design. At 380 GeV the novel dual BDS design features same luminosities than the current baseline. However at 3 TeV the luminosity performance is reduced by 2% from the baseline design for the IR1 and by 33% for the IR2. The dual CLIC BDS design provides adequate luminosities to two detectors and proves to be a viable candidate for future linear collider projects.

Plasma wakefield dynamics over timescales up to 800 ps, approximately 100 plasma periods, are studied experimentally at the Advanced Wakefield Experiment (AWAKE). The development of the longitudinal wakefield amplitude driven by a self-modulated proton bunch is measured using the external injection of witness electrons that sample the fields. In simulation, resonant excitation of the wakefield causes plasma electron trajectory crossing, resulting in the development of a potential outside the plasma boundary as electrons are transversely ejected. Trends consistent with the presence of this potential are experimentally measured and their dependence on wakefield amplitude are studied via seed laser timing scans and electron injection delay scans., 11 pages, 8 figures

The electrical quality assurance (ELQA) of the superconducting circuits of CERN's Large Hadron Collider (LHC) during its second Long Shutdown (LS2) requires the execution of vast measurement campaigns. Each of 1658 electrical circuits as well as the instrumentation of each of the 1746 individual cryo-assemblies housing magnets, bus-bars and other components of the superconducting circuits, has to undergo a series of tests. At the beginning of the shutdown the tests are performed before and after the warm-up from cryogenic temperatures. The same tests are repeated at the end of the shutdown, this time before and after the cool-down. As part of the dipole bypass diode insulation consolidation project and due to the replacement of a few non-conform magnets, additional electrical tests and measurements had to be performed throughout the shutdown period. With each measurement, electrical parameters like resistance, complex impedance, and the quality of the insulation are verified and stored for future reference. Due to the many thousands of measurements to be performed, multiple automated mobile test benches had to be developed for the different test types along with dedicated database and analysis software applications for the documentation and follow-up of the test results and the non-conformities observed.

Intelligent robotic systems are becoming essential for inspections and measurements in harsh environments. This article presents the design of an omnidirectional robotic platform for tunnel inspection with spatial limitations. This robot was born from the need to automate the surveillance process of the Super Proton Synchrotron (SPS) accelerator of the European Organization for Nuclear Research (CERN), where there is remaining radiation. The accelerator is located within a tunnel that is divided by small doors of 400 × 200 mm dimensions, through which the robot has to cross. The designed robot brings a robotic arm, and the needed devices to carry out the inspection. Thanks to this design, the robot application may vary by replacing certain devices and tools. In addition, this paper presents the kinematic and dynamic control models for the robotic platform.

European physical journal special topics 229(24), 3675 - 4284 (2020). doi:10.1140/epjst/e2020-000127-8, This report presents the conceptual design of a new European research infrastructure EuPRAXIA. The concept has been established over the last four years in a unique collaboration of 41 laboratories within a Horizon 2020 design study funded by the European Union. EuPRAXIA is the first European project that develops a dedicated particle accelerator research infrastructure based on novel plasma acceleration concepts and laser technology. It focuses on the development of electron accelerators and underlying technologies, their user communities, and the exploitation of existing accelerator infrastructures in Europe. EuPRAXIA has involved, amongst others, the international laser community and industry to build links and bridges with accelerator science — through realising synergies, identifying disruptive ideas, innovating, and fostering knowledge exchange. The Eu-PRAXIA project aims at the construction of an innovative electron accelerator using laser- and electron-beam-driven plasma wakefield acceleration that offers a significant reduction in size and possible savings in cost over current state-of-the-art radiofrequency-based accelerators. The foreseen electron energy range of one to five gigaelectronvolts (GeV) and its performance goals will enable versatile applications in various domains, e.g. as a compact free-electron laser (FEL), compact sources for medical imaging and positron generation, table-top test beams for particle detectors, as well as deeply penetrating X-ray and gamma-ray sources for material testing. EuPRAXIA is designed to be the required stepping stone to possible future plasma-based facilities, such as linear colliders at the high-energy physics (HEP) energy frontier. Consistent with a high-confidence approach, the project includes measures to retire risk by establishing scaled technology demonstrators. This report includes preliminary models for project implementation, cost and schedule that would allow operation of the full Eu-PRAXIA facility within 8—10 years., Published by Springer, Heidelberg

The luminosity of a particle collider is an extremely crucial performance parameter describing its capability of producing interactions in the collision point. However, imperfections in a collider can lead to luminosity loss. Among different imperfections, an important one is stray magnetic fields. For the Compact Linear Collider (CLIC), a collider being considered as one of the main options in Europe after the Large Hadron Collider, simulations showed an unprecedented sensitivity of the machine to fields on the order of 0.1 nT. Hence, such tight constraints require special design considerations to prevent performance loss. Different shielding techniques are available in the literature, typically relying on an active shielding strategy and capable of reducing the magnetic field amplitudes down to the nano-Tesla level. However, measuring fields with such amplitudes is challenging by using state-of-the-art commercially available sensors and therefore, a passive shielding strategy, consisting in enveloping sections of the beamline with a magnetic shield, is a more attractive option. For CLIC, Mumetal®, a Ni–Fe alloy with advertised relative permeability above 100,000, was chosen. In this paper, the DC and AC magnetic characterization of two samples of Mumetal®, one annealed in its final form and the other one non-annealed is presented, showcasing how the annealing results in a boost of the magnetic permeability of more than order of magnitude. As a case study, the shielding performance of a 1-mm thin layer of Mumetal® enveloping CLIC’s beamline is estimated.

The CompactLight European consortium is designing a state-of-the-art x-ray free-electron laser driven by radiofrequency X-band technology. Rooted in experimental data on photo-injector performance in the recent literature, this study estimates analytically and numerically the performance of the CompactLight delivery system for bunch charges in the range 75&ndash, 300 pC. Space-charge forces in the injector, linac transverse wakefield, and coherent synchrotron radiation in bunch compressors are all taken into account. The study confirms efficient lasing in the soft x-rays regime with pulse energies up to hundreds of microjoules at repetition rates as high as 1 kHz.

Numerical optimization algorithms are already established tools to increase and stabilize the performance of particle accelerators. These algorithms have many advantages, are available out of the box, and can be adapted to a wide range of optimization problems in accelerator operation. The next boost in efficiency is expected to come from reinforcement learning algorithms that learn the optimal policy for a certain control problem and hence, once trained, can do without the time-consuming exploration phase needed for numerical optimizers. To investigate this approach, continuous model-free reinforcement learning with up to 16 degrees of freedom was developed and successfully tested at various facilities at CERN. The approach and algorithms used are discussed and the results obtained for trajectory steering at the AWAKE electron line and LINAC4 are presented. The necessary next steps, such as uncertainty aware model-based approaches, and the potential for future applications at particle accelerators are addressed., peer-reviewed

In this document, I recall my own personal memories of the conception, design, construction and operation of particle accelerators and particle colliders over the past 50 years. This is not meant to be a technical report, and this is evidenced by the style of writing (commonly used first person singular), but more to give an insight to the historical beginnings and endings of some of the world’s most technically complex and expensive scientific instruments.

Computer physics communications 271, 108204 - (2022). doi:10.1016/j.cpc.2021.108204, Merlin++ is a C++ charged-particle tracking library developed for the simulation and analysis of complex beam dynamics within high energy particle accelerators. Accurate simulation and analysis of particle dynamics is an essential part of the design of new particle accelerators, and for the optimization of existing ones. Merlin++ is a feature-full library with focus on long-term tracking studies. A user may simulate distributions of protons or electrons in either single particle or sliced macro-particle bunches. The tracking code includes both straight and curvilinear coordinate systems allowing for the simulation of either linear or circular accelerator lattice designs, and uses a fast and accurate explicit symplectic integrator. Physics processes for common design studies have been implemented, including RF cavity acceleration, synchrotron radiation damping, on-line physical aperture checks and collimation, proton scattering, wakefield simulation, and spin-tracking. Merlin++ was written using C++ object orientated design practices and has been optimized for speed using multicore processors. This article presents an account of the program, including its functionality and guidance for use. Program Title: Merlin++ CPC Library link to program files:https://doi.org/10.17632/4x4nsbhz37.1 Developer's repository link: 10.5281/zenodo.3700155 Licensing provisions: GPLv2+ Programming language: C++ Nature of problem: Complexity of particle accelerators beam dynamics over extensive tracking distances. Solution method: Long-term particle accelerator and tracking simulations utilizing explicit symplectic integrators. Additional comments including restrictions and unusual features: For further information see github.com/Merlin-Collaboration, Published by North Holland Publ. Co., Amsterdam

We present recent progress with our algorithm and its implementation called simpa described in a previous paper. The algorithm has a new and unique approach to long-term 4D tracking of charged particles in arbitrary static electromagnetic fields. Using the improvements described in this paper, we made frequency analysis and dynamic aperture studies in ELENA. The effect of the end fields and the perturbation introduced by the magnetic system of the electron cooler on dynamic aperture is shown. A special feature of this study is that we have not introduced any multipole errors into the model. The dynamic aperture calculated in this paper is the direct consequence of the geometry of the magnetic elements. Based on the results, we make a few suggestions to reduce the losses during the deceleration of the beam. We briefly present recent progress with our algorithm and its implementation called SIMPA described in a previous paper. The algorithm has a new and unique approach to long-term 4D tracking of charged particles in arbitrary static electromagnetic fields. Using the improvements described in this paper, we made frequency analysis and dynamic aperture studies in ELENA. The effect of the end fields and the perturbation introduced by the magnetic system of the electron cooler on dynamic aperture is shown. A special feature of this study is that we have not introduced any multipole errors into the model. The dynamic aperture calculated in this paper is the direct consequence of the geometry of the magnetic elements. Based on the results, we make a few suggestions to reduce the losses during the deceleration of the beam.

Several studies are on-going at CERN in the framework of the Physics Beyond Collider study group, with main aim of broadening the physics research spectrum using the available accelerator complex and infrastructure. The possibility to design a layout that allows fixed-target experiments in the primary vacuum of the CERN Large Hadron Collider (LHC), without the need of a dedicated extraction line, is part of these studies. The principle of the layouts presented in this paper is to deflect beam halo protons on a fixed-target placed in the LHC primary vacuum, by means of the channeling process in bent crystals. Moreover, the presence of a second bent crystal adjacent to the target opens a unique opportunity for the first direct measurement of electric and magnetic dipole moments of short-lived baryons. Two possible layouts are reported, together with a thorough evaluation on their expected performance and impact on LHC operations. Several studies are on-going at CERN in the framework of the Physics Beyond Collider study group, with main aim of broadening the physics research spectrum using the available accelerator complex and infrastructure. The possibility to design a layout that allows fixed-target experiments in the primary vacuum of the CERN Large Hadron Collider (LHC), without the need of a dedicated extraction line, is included among these studies. The principle of the layouts presented in this paper is to deflect beam halo protons on a fixed-target placed in the LHC primary vacuum, by means of bent crystals (i.e. crystal channeling). Moreover, interaction products emerging from the target can be used to perform electromagnetic dipole moments measurements of short-living baryons. Two possible layouts are reported, together with a thorough evaluation on their expected performance and impact on LHC operations.

At the Large Hadron Collider (LHC), the interplay between a series of effects, including intrabeam scattering (IBS), synchrotron radiation, longitudinal beam manipulations, two beam effects (beam-beam, e-cloud) and machine nonlinearities, can change the population of the core and tails and lead to non-Gaussian beam distributions, at different periods during the beam cycle. By employing generalized distribution functions, it can be demonstrated that the modified non-Gaussian beam profiles have an impact in the beam emittance evolution by itself and thereby to the collider luminosity. This paper focuses on the estimation of beam distribution modification and the resulting rms beam size due to the combined effect of IBS and synchrotron radiation by employing a Monte-Carlo simulation code which is able to track 3D generalized particle distributions (SIRE). The code is first benchmarked over classical semianalytical IBS theories and then compared with measurements from the LHC at injection and collision energies, including projections for the High-Luminosity LHC (HL-LHC) high brightness regime. The impact of the distribution shape on the evolution of the bunch characteristics and machine performance is finally addressed. At the Large Hadron Collider (LHC), the interplay between a series of effects, including intrabeam scattering (IBS), synchrotron radiation, longitudinal beam manipulations, two beam effects (beam-beam, e

An 8-km long MgB$_{2}$ wire for a prototype klystron magnet was made and evaluated. The wire was made by a typical in situ method; it has 10 filaments and 0.67 mm in outer diameter. The homogeneity of I $_{c}$ of this wire was evaluated by several methods. Deviation of I $_{c}$ values in short sample wires was very small. In addition, the current sharing temperature of the MgB$_{2}$ magnet (made of two reels of wire 2.9 km long each) agreed well with the estimated value of the I $_{c}$-B-T properties in short sample wires. Based on the obtained results, it can be said that the I $_{c}$ properties of the entire wire length are quite uniform.

An M$_{g}$B$_{2}$ superconducting solenoid magnet has been developed for electron beam focusing in X-band (12 GHz) klystrons for particle accelerator RF systems, to provide a central field of 0.8 T at 57 A and at ≥ 20 K. It has successfully realized significant AC-plug power saving in one order of magnitude compared with that for a conventional Cu solenoid magnet. The large-scale application may be expected for the Compact Linear Collider (CLIC) project proposed as a future accelerator candidate at CERN. It requires ~ 5,000 klystrons, and the M$_{g}$B$_{2}$ magnet application will realize significant AC-plug power saving. This paper describes progress in a prototype M$_{g}$B$_{2}$ superconducting solenoid magnet development and discusses the future prospect.

International audience; Sophisticated infrastructures often exhibit misbehaviour and failures resulting from complex interactions of their constituent subsystems. Such infrastructures use alarms, event and fault information, which is recorded to help diagnose and repair failure conditions by operations experts. This data can be analysed using explainable artificial intelligence to attempt to reveal precursors and eventual root causes. The proposed method is first applied to synthetic data in order to prove functionality. With synthetic data the framework makes extremely precise predictions and root causes can be identified correctly. Subsequently, the method is applied to real data from a complex particle accelerator system. In the real data setting, deep learning models produce accurate predictive models from less than ten error examples when precursors are captured. The approach described herein is a potentially valuable tool for operations experts to identify precursors in complex infrastructures.