Search

We present the conceptual design of a compact light source named BriXSinO. BriXSinO was born as demonstrator of the Marix project, but it is also a dual high flux radiation source Inverse Compton Source (ICS) of X-ray and Free-Electron Laser of THz spectral range radiation conceived for medical applications and general applied research. The accelerator is a push-pull CW-SC Energy Recovery Linac (ERL) based on superconducting cavities technology and allows to sustain MW-class beam power with almost just one hundred kW active power dissipation/consumption. ICS line produces 33 keV monochromatic X-Rays via Compton scattering of the electron beam with a laser system in Fabry-Pérot cavity at a repetition rate of 100 MHz. The THz FEL oscillator is based on an undulator imbedded in optical cavity and generates THz wavelengths from 15 to 50 micron., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

High order modes (HOMs) in multi-cell superconducting cavities are of particular concern in beam dynamics of linear accelerators, mainly those operating in CW mode with high current and high repetition rate. These undesired modes may invoke beam instabilities, beam breakup and increase the energy spread if not correctly pulled out and damped. The study reported in this paper is applied for damping the HOMs in the main Linac of BriXSinO, an ongoing project of an Energy Recovery Linac at LASA INFN laboratory. We developed a numerical model to study the interaction of monopole HOMs with the beam in long timescale. The presented model, named HOMEN (High Order Modes Evolution based on eNergy budget), allows the evaluation of the loss factor Kloss, crucial for evaluating the perturbing modes. At the same time, electromagnetic simulations of the standing wave multicell cavity, highlighted the dangerous modes and revealed a tolerable beam energy spread induced by HOMs. This method allows us to distinguish all dangerous modes of our interest for implementing the necessary damping mechanisms., Proceedings of the 31st International Linear Accelerator Conference, LINAC2022, Liverpool, UK

The paper analyses the phenomenon of gender discrimination in the Hard Sciences Sector. Our purpose is to discover more hidden dimensions of the discrimination phenomenon, such as the implementation of organizational models, the time management, the productivity indicators, which all refer to men workers. The sample used is the universe of INFN (National Institute for Nuclear Physics) in Naples, a sector of “Hard Sciences” (Physics, Astrophysics, etc...) always known for its strong segregation, both horizontal and vertical (we refer to the underrepresentation of women in the sector and /or in top positions). We used the narrative interviews and the functional analysis to study the characteristics of the workers inside INFN. We interviewed some of the employees at INFN in Naples: researchers, technologists, administrative staff and technicians. The results show that the models adopted inside the organization penalize women and often men too: they affect not so much the conventional discrimination indicators (kind of occupation, wages, tasks to be carried out and so on), but the quality of life of the workers (especially the women); these models find their origin in the way the society and the labor market are structured (e.g. the asymmetry of familiar and house tasks).

In many resonant structures the damping of parasitic or higher order modes is indispensable to guarantee a correct and stable performance. This is particularly true in the microwave region in case of cavities or other resonant systems operating in accelerating structures, where the mitigation of spurious resonance effects is mandatory to achieve high quality particle beams. We present the results on the mode suppression in a real pillbox cavity by inserting a properly designed pyramidal metamaterial that acts as light, small volume damper for specific resonances in the range 3–4 GHz, only slightly perturbing other intrinsic modes. Measurements of the cavity response without and with the metamaterial absorber are presented and compared with full wave simulations. Field distribution for the pillbox intrinsic modes under scrutiny is also presented, showing that damping induced by the metamaterial critically depends on its relative position inside the cavity.

Resistive-wall impedance constitutes a significant percentage of the total beam-coupling impedance budget of an accelerator. A number of different reduction techniques have been proposed during the years depending on the specific applications, ranging from higher order modes damping to solutions entailing high electrical-conductivity coatings of the pipe. This article investigates the use of metamaterial-based absorbers for sensibly reducing or nearly canceling the beam-coupling impedance. We design and fabricate subwavelength 2-D metallic resonant structures based on the split-ring resonator (SRR) geometry that can be employed as mode dampers in accelerating structures. A number of prototypes have been fabricated and measured in a “test model” pillbox cavity. Experimental results, combined with full-wave electromagnetic simulations, prove the efficiency of the SRR-based metamaterials. This article opens up to the possibility of considering metamaterials as a valid alternative to other devices for impedance mitigation in experimental setups commonly operating along a particle beamline, such as accelerating cavities or collimators, and more in general for the development of filters with a large out-of-band signal rejection in specific applications.

The electron-cloud phenomenon is one cause of beam instabilities in high intensity positive particle accelerators. Among the proposed techniques to mitigate or control this detrimental effect, micro-/nano-geometrical modifications of vacuum chamber surfaces are promising to reduce the number of emitted secondary electrons. Femtosecond laser surface structuring readily allows the fabrication of Laser Induced Periodic Surface Structures (LIPSS) and is utilized in several fields, but has not yet been tested for secondary electron emission reduction. In this study, such treatment is carried out on copper samples using linearly and circularly polarized femtosecond laser pulses. The influence of the formed surface textures on the secondary electron yield (SEY) is studied. We investigate the morphological properties as well as the chemical composition by means of SEM, AFM, Raman and XPS analyses. Surface modification with linearly polarized light is more effective than using circularly polarized light, leading to a significant SEY reduction. Even though the SEY maximum is only reduced to a value of ~1.7 compared to standard laser-induced surface roughening approaches, the femtosecond-LIPSS process enables to limit material ablation as well as the production of undesired dust, and drastically reduces the number of redeposited nanoparticles at the surface, which are detrimental for applications in particle accelerators. Moreover, conditioning tests reveal that LIPSS processed Cu can reach SEY values below unity at electron irradiation doses above 10−3 C/mm2.

This paper presents an update on women and physics in Italy over the past five years. The numbers of women with physics degrees and the statistics on women with careers in universities or in the main Italian research institutions (National Institute for Nuclear Physics, National Institute of Astrophysics, and National Research Council) are given. Also, results are reported from European projects, such as Transforming Organisational Culture for Gender Equality in Research and Innovation and Gender Equality Network in the European Research Area in which Italy is involved.

The electromagnetic characterisation of different materials for the inner wall coating of beam pipes is a long-standing problem in accelerator physics, regardless the purpose they are used for, since their presence may affect in an unpredictable way the beam coupling impedance and therefore the machine performance. Moreover, in particle accelerators and storage rings of new generation very short bunches might be required, extending far in frequency the exploration of the beam spectrum and rendering therefore more and more important to assess the coating material response up to hundreds of GHz. This paper describes a time domain method based on THz waveguide spectroscopy to infer the coating properties at very high frequencies. The technique has been tested on Non Evaporable Getter thick films deposited by DC magnetron sputtering on copper plates.

Many resonant structures in the microwave region need damping of parasitic or higher order modes in order to optimise their performance. In cavities or other systems operating in accelerating structures, for example, the mitigation of spurious resonance effects is indispensable to achieve high quality particle beams. We present here a parametric study on the absorption properties of a multilayered metamaterial having the shape of a truncated pyramid to be used as light, small volume damper in a microwave cavity. Full wave simulations have been performed for a single absorber varying its size and number of layers and for a linear array changing the distance between the single elements. A case study is proposed, where a single pyramid is inserted in a real pillbox cavity. Measurements of the cavity response without and with the metamaterial absorber are presented and compared with numerical results.

Il volume è un contributo originale al dibattito sugli interventi a favore della parità di genere nell’Università e nella ricerca. Presenta i risultati della ricerca-azione condotta, insieme alla sperimentazione del programma pilota di mentoring, nell’ambito del progetto europeo GENOVATE@UNINA. Ponendosi in interlocuzione con le ricerche europee più recenti - sviluppate entro la cornice culturale e il quadro di riferimento degli interventi per il cambiamento strutturale, promossi anche attraverso il settimo programma quadro e Horizon 2020 - assume, come quadro di riferimento interpretativo, i processi di cambiamento globale che investono la regolazione del sistema scientifico-accademico. La trattazione si sviluppa seguendo un percorso lineare, che dal dibattito sulle politiche per la parità di genere conduce al disegno dello schema pilota di mentoring (il primo esclusivamente al femminile, nell’università italiana) e, quindi, alla ricerca che ha accompagnato il progetto nel suo percorso. L’interpretazione dei risultati, sorretta da interviste biografico-narrative sui percorsi di carriera e da focus group con mentori e mentee, rivela attraverso quali pratiche e quali processi si producono e riproducono le diseguaglianze di genere nell’accademia e nella ricerca. Con gli strumenti dell’indagine valutativa, questi risultati sono quindi messi a fuoco per ricostruire il funzionamento del mentoring come pratica di genere capace di de-costruire i processi che producono diseguaglianza e produrre effetti trasformativi del contesto scientifico-accademico.

Resistive-wall impedance constitutes a significant percentage of the total beam-coupling impedance budget of an accelerator. Under extreme conditions, like large power handling and ultrahigh vacuum, metamaterial-based absorbers can represent a valid alternative to other approaches for impedance mitigation in specific accelerator components, like resonant (parasitic) cavities or collimators operating along the beam line. We design sub-wavelength 2D metallic resonant structures based on split rings or on 3D hyperbolic tapered waveguide arrays that can be employed as mode dampers in accelerating structures. A number of prototypes are fabricated and then measured in a "test model" pillbox cavity.

The iPipe project consists in the instrumentation, with Fiber Bragg Grating sensors (FBGs), of the beam pipe of the CMS experiment, which is part of the LHC. Being spectrally encoded, the FBGs are not sensitive to electromagnetic interference and broadband-radiation-induced losses. These characteristics allow to realize long distance punctual sensing systems, capable to operate in harsh environments like the underground experimental and accelerator facilities at CERN. The iPipe secures the measurement of any deformation induced on the central beam pipe by any motion in the CMS detector due to element displacement or to magnetic field induced deformations. Moreover, the iPipe FBG temperature sensors represent a unique solution to monitor the beam pipe thermal behavior during the various operational and maintenance phases. This paper reports the use of the iPipe to measure the beam induced heating on the CMS vacuum chamber throughout 2016 and 2017. A first comparison between the measurements and the heat load predicted from beam induced RF heating due to the coupling impedance of the CMS pipe is also reported., Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada

The ICFA Mini-Workshop on Impedances and Beam Instabilities in Particle Accelerators, was held in Benevento, Italy, from 18 to 22 September, 2017. The rich scientific program of the workshop was defined and shaped by a strongly motivated International Advisory Committee, composed of worldwide experts who actively provided their inputs. The conference venue was the San Vittorino complex, located in the very center of the historical town of Benevento. The workshop was supported and sponsored by the University of Sannio, three ongoing large accelerator projects (High Luminosity LHC, LHC Injectors Upgrade, LHC Collimation), the European network ARIES and the INFN section of Naples. Moreover, it was held under the auspices of the Italian Physical Society (SIF). The main goal was to summon the accelerator community actively working in the field of impedances and beam instabilities, and discuss together recent advancements and breakthroughs while defining future directions. Eighty-four participants from different laboratories all around the world attended the workshop, with a strong representation of young accelerator physicists with little experience and plenty of enthusiasm. That's why all the speakers made their best effort to provide a solid educational background into their subjects, before highlighting novelties, challenges and open questions. The workshop chairs also had the great pleasure to celebrate Prof. Vittorio G. Vaccaro on the occasion of the 50 years since the birth of the concepts of beam coupling impedance and stability charts, to which he gave fundamental contributions unanimously recognised by the whole community. The workshop also provided the opportunity to remember dearly Dr. Francesco Ruggiero, who passed away 10 years ago, by highlighting in the opening speech his amazing foresight into all the beam dynamics issues of LHC and all future machines.

This paper describes a reliable, handy, and inexpensive measurement system to characterize, in the sub-THz frequency range, the coating materials used in the beam pipes of accelerators. The method is based on time domain measurements of an electromagnetic wave passing through a waveguide having a thin central slab, where the coating material is deposited on both sides. Two horn antennas are integrated on both sides of the device to optimize the signal collection and detection. This novel technique is tested on slabs coated with a nonevaporable getter (NEG) and allows to evaluate the surface impedance in the frequency range from 0.1 to 0.3 THz.

Questo lavoro di ricerca raccoglie e analizza alcuni dati relativi alla presenza delle donne nelle facoltà scientifiche nel corso dell'ultimo decennio. Si tratta di un percorso di analisi intrapreso dal Coordinamento napoletano “Donne nella Scienza” e motivato dalla convinzione che una conoscenza quantitativa e puntuale dei rapporti di genere su scala locale sia un prerequisito indispensabile per proporre azioni positive volte ad incidere sul contesto in cui si opera. In questa comunicazione vengono presentati i dati relativi alla composizione di genere nell’ambito della formazione universitaria e della carriera accademica nelle discipline scientifiche dell’Università “Federico II” di Napoli – che, essendo il più grande ateneo del Sud Italia, risulta altamente rappresentativo della realtà accademica meridionale - nonché del Politecnico e dell'Università di Torino che, insieme, costituiscono uno dei più grandi centri universitari del Nord. L'obiettivo della presente analisi è quello di individuare la collocazione temporale del punto di divergenza della forbice che differenzia il percorso femminile da quello maschile, le differenze tra settori scientifici diversi, le eventuali peculiarità rispetto all'andamento nazionale ed europeo, le specificità geografiche e le differenze tra grandi atenei del Nord e del Sud.

Electron cloud has a ubiquitous effect in positively charged particle accelerators and has been observed to induce unwanted detrimental effects on beam quality, sta- bility, vacuum etc. A great effort has been recently devoted to the search of new material morphology and/or coatings which can intrinsically mitigate beam instabilities deriving from electron cloud effects. In this context, we present some characterization of commercially available Cu foams and their qualification mainly in terms of secondary elec- tron yield (SEY), along with the vacuum behavior, their impact on the impedance budget, photo-desorption yield, etc. More experimental efforts are required to finally qual- ify foams as a mature technology to be integrated into accelerator systems. Our preliminary results suggest po- tentially interesting use in the accelerator technology.

Experimental results for an open resonator fed by a rectangular waveguide in the 18–20-GHz frequency band are presented. The data are compared with theoretical results arising from the mode-matching approach to the problem to give a simple equivalent circuit. © 1995 John Wiley & Sons, Inc.

In a recent investigation, we studied two-dimensional point-defected photonic bandgap cavities composed of dielectric rods arranged according to various representative periodic and aperiodic lattices, with special emphasis on possible applications to particle acceleration (along the longitudinal axis). In this paper, we present a new study aimed at highlighting the possible advantages of using hybrid structures based on the above dielectric configurations, but featuring metallic rods in the outermost regions, for the design of extremely-high quality factor, bandgap-based, accelerating resonators. In this framework, we consider diverse configurations, with different (periodic and aperiodic) lattice geometries, sizes, and dielectric/metal fractions. Moreover, we also explore possible improvements attainable via the use of superconducting plates to confine the electromagnetic field in the longitudinal direction. Results from our comparative studies, based on numerical full-wave simulations backed by experimental validations (at room and cryogenic temperatures) in the microwave region, identify the candidate parametric configurations capable of yielding the highest quality factor., 13 pages, 5 figures, 3 tables. One figure and one reference added; minor changes in the text