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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

International audience; Coupled resonators in an assembled structure lose their individuality and in co-operation contribute to the generation of structure modes (resonant frequencies). The resonant frequencies of these modes are the only measurable quantities. In order to predict structural behaviour in a variety of cases, the problem that arises is the extraction of all the parameters characterizing the structure from the measurements mentioned here. If all the modes are confined in a bandwidth that is small with respect to the central frequency, the total coupled resonator system is well represented by a circuit of unknown lumped constants. The structure modes are the solutions of the equation obtained by equating to zero the determinant relevant to the lumped circuit representation. The equation is a polynomial of the squared frequency variable, the degree of which is equal to the number M of circuits. The analysis method described in this paper consists in varying, by an unknown amount, the frequency of a single resonator in the chain. This variation will produce a change in the frequencies of all structure modes. It is possible to find certain invariants linearly dependent on all the unchanged parameters of the circuit. These invariants have an algebraic representation that allows the extraction of the structure parameter values with extremely high accuracy. The proposed method is quite general and, in the present work, we give an example applying the method to the characterization of a side-coupled linac (SCL)

Recent results in accelerator physics have shown the feasibility of a coupling scheme between a cyclotron and a linac for proton acceleration. Cyclotrons with energies up to 30 MeV, mainly devoted to radioisotopes production, are available in a large number of medical centres. These two evidences have suggested the idea to study and design a linac booster able to increase the initial proton energy up to the values required for the treatment of tumors, like the ocular ones. One of the main challenges in such a project is related to meet the requirement of having sufficient mean current for therapy from a given injection current coming from the cyclotron. In this paper we will review the rationale of the project in order to optimize the transmittance and to minimize the duty-cycle. In this frame we will discuss the basic design of a compact 3GHz linac, from 30 to 62 MeV, with a new approach to the cavities used in a SCL (Side Coupled Linac) structure (PALME project).

One of the main problems in the design of high intensity rf accelerators is the presence of higher order modes (HOMs) which might degrade the beam quality. Accelerating cavities require HOMs suppression, whereas keeping a high quality factor (Q) for the fundamental mode. Both these requirements can be hardly met in closed metallic cavities, especially at high frequency where the configurations become cumbersome and technically unviable. Cavities based on photonic band gap (PBG) concepts showed that HOMs can be efficiently suppressed without affecting the fundamental mode. We present here simulations and measurements at room and cryogenic (77 K) temperature on some metallic (Copper) and metallo-dielectric (Copper + sapphire) PBG based cavities, in order to study their rf behavior as resonant element in particle accelerators. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2486–2491, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22016

By means of a general theory we examine the Sands and Rees method (1974) of measurement of the longitudinal coupling impedance between a particle beam and the vacuum chamber components. We discuss the validity limits of the method in relation to the presence of the central wire which simulates the beam.

An overview of the Frascati Phi -factory and the salient project features are presented. The engineering design of vacuum and magnetic components, diagnostics, power supplies of the accumulator ring and of the main rings is in progress. The main concern, at this time, is how to handle the multibunch instability that is the most harmful problem in the design of high current storage rings and the most serious limitation for the luminosity. The parasitic high-order modes of the RF cavities are responsible for such an instability. >

The lattice for the double ring e/sup +/e/sup -/ collider DA Phi NE of the Frascati Phi -factory project is presented. Electrons and positrons circulate in two horizontally separated storage rings and collide at a horizontal half angle of 10 mrad in one or two interaction points. This allows a very short bunch distance and therefore a very high collision frequency (

After the installation of the optical cavity of the LELA experiment, a series of tests of the cavity alignment relative to the electron beam direction has been performed, showing the problems due to the peculiarity of this cavity. The use of piezoelectric translators in ultrahigh vacuum has permitted a smooth and precise control of the cavity optical axis. Preliminary results on mirror damage due to UV radiation have also been obtained.

The alignment of the LELA optical cavity, 17.5 m long, is described. The procedure to attain a close alignment of the undulator radiation axis and the cavity axis using an external laser is reported. Measurements of Q from stored light spectra are presented. Mirror degradation at increasing integrated electron currents is considered.

Due to the high K value (4.8) of the LELA undulator, we expect a significant UV induced damage of TiO2SiO2 dielectric mirrors. Preliminary tests on commercial grade mirrors exhibit a great loss of reflectivity, due to two distinct processes of induced degradation. One of them is surface absorption of carbon in the upper SiO2-air interface. It is not affected by annealing. The other corresponds to a volume damage induced by the high energy radiation present during injection into the accelerator or during the runs at 1.5 GeV for synchrotron radiation production.

The radiation emitted by the linear undulator installed on a straight section of the ADONE storage ring is studied both experimentally and theoretically. In particular, expressions are provided for the field at finite distance, based on the complex Fresnel integral. In addition, several expressions are derived for the average intensity pattern as a function of the electron beam divergence and energy spread. These formulae are used for analysing the spectral and angular patterns of the radiation measured from a distance of 20 m from the undulator origin. The excellent quality of the undulator and the negligible influence on the pattern of the electron beam divergence are confirmed by the satisfactory agreement of the measured radiation field with the computer-generated one.

After a brief discussion of the influence of the e-beam finite emittance on the small signal gain of the LELA free electron laser, the optical cavity of the FEL built on the ADONE storage ring in Frascati is described. Particular attention is devoted to the description of the alignment and tuning problems, both of which have been solved by means of a remote control system.

A detailed description of the parameter choice for the LELA optical cavity is presented. Particular attention has been devoted to the alignement problems solved by means of a remote control system. First results on mirror damage due to UV radiation will be also reported.

Progress in the LELA (free electron laser on ADONE) experiment from September 1986 to July 1987 is described. Improvements in machine lattice and control, and automation in cavity alignment allowed for a maximum Q factor of ≈ 103.

The glasses (AgI) x (Ag 2 O n B 2 O 3 ) 1−x have been studied by optical and X-ray absorption spectroscopy at various x and n concentrations. The optical absorption of the n=4 glasses shifts linearly at the increasing of the AgI content x. Extrapolating to x=1, the corresponding value for α-AgI is crossed. The comparison of the EXAFS structures at the I L 3 edge of the n=3, x=0.3 glass and of β-AgI seems to indicate that the Ag-I coordination is substantially unmodified in the glass with respect to that in β-AgI. A further comparison of the EXAFS at the Ag L 3 edge allows to discuss the coordination Ag-O in the glass.

A short summary of the wiggler magnet beam lines and relative instrumentation installed at the Adone storage ring in Frascati is given. The future development of the wiggler laboratory is described. Preliminary results on the scientific activity in progress are presented.

Recent results on optical gain measurements on the ADONE FEL are reported and discussed. In addition, the results of a computer analysis of the Rayleigh length which optimizes the extraction of energy from the ADONE beam are discussed together their implications on the configuration of the optical cavity to be used for the FEL oscillator. These simulations have been based on a suitable extension of the Madey's theorem and on a representation of the electron work against the field of a gaussian beam by means of the far field radiated by the single electron. In turn, the accuracy of the calculated far field has been tested by comparison with the measured patterns of the spontaneous radiation.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In the last years the superionic materials have raised a great interest in physicists and chemists for their characteristic property of high ionic condutivity [1]. Most of the new materials which have been used for application as solid electrolytes [2] were crystalline materials in which the structure allows high ionic conductivity. Among superionic conductors, silver iodide is one of the most studied for the motion of conducting ions through the sites: a low potential barrier implies a weak bond between the mobile ion and the reticular structure. Now our interest for ionic compounds is turned to glassy materials. They have the advantage of easiness of preparation in a large range of dimensions. Moreover their composition can be almost continuously changed. For these considerations we have been stimulated to study borate glasses containing silver iodide: in particular (AgI)x (Ag2O n B2O3)1−x glasses at various x and n concentrations.

A short description of the LELA (Free Electron Laser on Adone) experiment is given. Results on the spontaneous radiation angle and energy spectra and preliminary results on optical gain measurements are also discussed.