A laser pulse shaper for the low-emittance radiofrequency SPARC electron gun

To generate a very low emittance electron beam in a 3-GHz radiofrequency gun, the photocathode has to be driven by a powerful 10-ps light pulse with a rise time of less than 1 ps: This target pulse can be generated from a subpicosecond laser pulse by inserting an appropriate shaping device. We discuss a programmable 4f grating-lensshaper configured so as to transform a 100-fs pulse emitted by a Ti:Sa laser into a rectangular pulse with a fast rise time. We analyze the sensitivity of the system to perturbations of the optical-component alignment and input-signal characteristics. We then briefly discuss the acousto-optic programmable dispersive filter shaping system. r 2004 Elsevier B.V. All rights reserved

The path and the multi-teaching issues in the coupled pendulum and mass-spring experiments

The main task of an introductory laboratory course is to foster students' manual, conceptual and statistical ability to investigate physical phenomena. Needing very simple apparatus, pendulum experiments are an ideal starting point in our first-year laboratory course because they are rich in both physical content and data processing. These experiments allow many variations, e.g. pendulum bobs can have different shapes, threads can be tied to a hook at their edge or pass through their centre of mass, they can be hanged as simple or bifilar pendulums. In these many variations, they emphasize the difference between theory and practice in the passage from an idealized scheme to a real experimental asset, which becomes evident, for example, when the pendulum bob cannot be considered an idealized point mass. Moreover, they require careful observation of details such as the type of thread used and its rigidity or the bob initial slant, which leads to different behaviors. Their mathematical models require a wide range of fundamental topics in experimental data analysis: arithmetic and weighted mean, standard deviation, central limit theorem application, data distribution, and the significant difference between theory and practice. Setting the mass-spring experiment immediately after the pendulum highlights the question of resonance, revises the gap between theory and practice in another context, and provides another occasion to practice further techniques in data analysis

Apparent superluminal advancement of a single photon far beyond its coherence length

We present experimental results relative to superluminal propagation based on a single photon traversing an optical system, called 4f-system, which acts singularly on the photon's spectral component phases. A single photon is created by a CW laser light down{conversion process. The introduction of a linear spectral phase function will lead to the shift of the photon peak far beyond the coherence length of the photon itself (an apparent superluminal propagation of the photon). Superluminal group velocity detection is done by interferometric measurement of the temporal shifted photon with its correlated untouched reference. The observed superluminal photon propagation complies with causality. The operation of the optical system allows to enlighten the origin of the apparent superluminal photon velocity. The experiment foresees a superluminal effect with single photon wavepackets.Comment: 11 pages, 2 figure

Conceptual Design of a Soft X‐ray SASE‐FEL Source

FELs based on SASE are believed to be powerful tools to explore the frontiers of basic sciences, from physics to chemistry to biology. Intense R&D programs have started in the USA and Europe in order to understand the SASE physics and to prove the feasibility of these sources. The allocation of considerable resources in the Italian National Research Plan (PNR) brought about the formation of a CNR‐ENEA‐INFN‐University of Roma "Tor Vergata" study group. A conceptual design study has been developed and possible schemes for linac sources have been investigated, bringing to the SPARX proposal. We report in this paper the results of a preliminary start to end simulation concerning one option we are considering based on an S‐band normal conducting linac with high brightness photoinjector integrated in a RF compressor

The spring-mass experiment as a step from oscillationsto waves: mass and friction issues and their approaches

The spring-mass experiment is a step in a sequence of six increasingly complex practicals from oscillations to waves in which we cover the first year laboratory program. Both free and forced oscillations are investigated. The spring-mass is subsequently loaded with a disk to introduce friction. The succession of steps is: determination of the spring constant both by Hooke's law and frequency-mass oscillation law, damping time measurement, resonance and phase curve plots. All cross checks among quantities and laws are done applying compatibility rules. The non negligible mass of the spring and the peculiar physical and teaching problems introduced by friction are discussed. The intriguing waveforms generated in the motions are analyzed. We outline the procedures used through the experiment to improve students' ability to handle equipment, to choose apparatus appropriately, to put theory into action critically and to practice treating data with statistical methods.El experimento resorte-masa es un paso en una secuencia de seis prácticas cada vez más complejas de oscilaciones a ondas en el que cubrimos el programa del primer año del laboratorio. Ambas oscilaciones libres y forzadas son investigadas. El resorte-masa se carga posteriormente con un disco para introducir la fricción. La sucesión de pasos es: determinación de la constante del resorte tanto por la ley de Hooke y la ley de oscilación frecuencia-masa, reducción del tiempo de medición, y representación de curvas de fase y resonancia. Todos los controles cruzados entre cantidades y leyes se realizan aplicando las normas de compatibilidad. Se discute la masa no despreciable del resorte y los problemas específicos de física y enseñanza derivados de la fricción. Se analizan las formas de onda complejas generadas en los desplazamientos. Se describen en términos generales los procedimientos utilizados en el experimento para mejorar la capacidad de los alumnos para manejar los equipos, para elegir adecuadamente los aparatos, para poner de manera crítica la teoría en práctica, y para practicar el tratamiento de los datos con métodos estadísticos

1st Italian Workshop on Carbon Nanotubes for Electronic Applications (ICNTE 2007)

SCOPE OF THE WORKSHOP This workshop aims to highlight the state of art on carbon nanotubes research activities for electronic applications and the perspectives of the Italian research groups active in such area. The required multidisciplinary approach pushes to define a shared strategy dealing with future challenging opportunities associated with the use of CNT in this prominent field of application. In this framework, the workshop offers the opportunity to identify synergies and to promote a more robust cooperation and coordination among the different research groups. Moreover, the just started FP7 could be used as driving force for implementing the strategy, giving opportunities to the Italian research community to present new ideas, new cooperating initiatives both at National and at International levels