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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.

Electron cloud is an ubiquitous effect in positively charged particle accelerators and has been observed to induce unwanted detrimental impacts on beam quality, stability, 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 Cu foams, available from the market, and their qualification in terms of their vacuum behavior, impedance, secondary electron yield, gas desorption etc. More experimental effort is required to finally qualify foams as a mature technology to be integrated in accelerator environments. But, our preliminary results suggests that, when compatible with geometrical constrains, Cu foams can be utilized when low desorption yields are required and as e-cloud moderator in future particles accelerators., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany