Plasma wakefield acceleration represents one of the most promising techniques able to overcome the limits of conventional rf technology and make possible the development of compact accelerators. With ...respect to laser-driven schemes, the particle beam-driven scenario is not limited by diffraction and dephasing issues; thus, it allows one to achieve larger acceleration lengths. Nevertheless, one of the most prominent drawbacks occurs at the end of the acceleration process and consists in the removal of the depleted high-charge driver while preserving the main features (emittance and peak current) of the accelerated witness bunch. Here we present a theoretical study demonstrating the possibility to reach these goals by using an innovative system consisting of an array of beam collimators and discharge capillaries operating as active-plasma lenses. Such a system allows one to extract and transport the accelerated and highly divergent witness bunch and, at the same time, provides for the removal of the driver. The study is completed with a set of numerical simulations conducted for different beam configurations. The physics of the interaction of particles with collimator is also investigated.
Starting from the electric fields produced by a point charge and a dipole traveling inside a circular vacuum chamber, in this paper we derive a formalism for a complete set of equations that describe ...the electromagnetic fields and the longitudinal and transverse coupling impedances arising by the interaction of a beam with a perfectly conducting pipe in the case of elliptic geometry. The expressions, which are valid for any frequency and beam energy, are written in terms of expansions of Mathieu functions, allow to range from a circular geometry to the parallel plates, and show an interesting parallelism with the well-known expressions for a circular pipe. We also obtain that, under the approximation of low frequency, the formalism allows us to derive the Laslett coefficients for parallel plates, circular and elliptic beam pipe.
There is a growing interest in engaging students and the general public about the meaning and objectives of doing science. When it is possible students can learn by actively engaging in the practices ...of science, conducting investigations, sharing ideas with their peers, teachers and scientists, learning to work with measuring apparatuses, to acquire and process data and use models so as to interpret phenomena. This is a process that requires a gradual collective growth. Schools and universities can both benefit from this cooperation. This paper presents activities of a project focusing on the radon survey in high schools. The ENVIRAD (environmental radioactivity) educational project involved about 2500 students and some tens of teachers in measurements while using solid state nuclear track detectors. This experience began about 15 years ago and is still carried out by various national projects managed by the same research group. The measurements and data analysis have been done in school laboratories and in the university radioactivity laboratory. Several hundred students were also involved in the transduction and signal processing. In some cases, pupils have also been involved in citizen awareness and the dissemination of this experience has kicked off a follow-up project explicitly addressed to citizens. The project has led to the opportunity to learn science through a real physics experiment. The students' enthusiasm allowed the collection of a relevant amount of data which benefitted both the regional survey on radon and the improvement of nuclear physics teaching at school. Through the project activities it was possible to recognize the interdisciplinary connections among different scientific disciplines connected to radioactivity.
Abyssal temperature and velocity observations performed within the framework of the Neutrino Mediterranean Observatory, a project devoted to constructing a km(3)-scale underwater telescope for the ...detection of high-energy cosmic neutrinos, demonstrate cross-fertilization between subnuclear physics and experimental oceanography. Here we use data collected south of Sicily in the Ionian abyssal plain of the Eastern Mediterranean (EM) basin to show for the first time that abyssal vortices exist in the EM, at depths exceeding 2,500 m. The eddies consist of chains of near-inertially pulsating mesoscale cyclones/anticyclones. They are embedded in an abyssal current flowing towards North-Northwest. The paucity of existing data does not allow for an unambiguous determination of the vortex origin. A local generation mechanism seems probable, but a remote genesis cannot be excluded a priori. The presence of such eddies adds further complexity to the discussion of structure and evolution of water masses in the EM.
Plasma based technology will allow an unprecedented reduction of the size of accelerating machines. Both fundamental research and applied science and technology will take profit of this feature. The ...same compactness is required downstream the accelerator module, where the plasma-accelerated beams usually experience a large angular divergences growth. Therefore compact, strong and tunable focusing devices are needed. Active-plasma lenses have been demonstrated to be a compact and affordable tool to generate radially symmetric magnetic fields. We present a new scheme using active-plasma lenses and a metallic collimator to catch and transport the witness bunch while removing the driver. The considered case study is in the context of the EuPRAXIA project.
In the framework of the KM3Net European project, the production stage of a large volume underwater neutrino telescope has started. The forthcoming installation includes 8 towers and 24 strings, that ...will be installed 100 km off-shore Capo Passero (Italy) at 3500 m depth. The KM3NeT tower, whose layout is strongly based on the NEMO Phase-2 prototype tower deployed in March 2013, has been re-engineered and partially re-designed in order to optimize production costs, power consumption, and usability. This contribution gives a description of the main electronics, including front-end, data transport and clock distribution system, of the KM3NeT tower detection unit.
•The effect of the LIPSS process on the surface chemical properties and consequently on SEY is investigated.•Femtosecond Laser-Induced Periodic Surface Structures (LIPSS) are used to reduce SEY in ...copper.•Copper treated with LIPSS shows a low surface debris density and is therefore less critical for ultra-high vacuum applications in particle accelerators.
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.
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LIBO is a proton accelerator that operates at
3
GHz
, the same frequency as the one adopted in the about 7500 electron linacs used for radiotherapy all over the world. Such a high frequency was ...chosen to obtain a large gradient (on average more than
10
MV/m
), and thus a short linac (about
15
m
) to boost the energy of the protons, extracted at about
60
MeV
from a cyclotron, up to the
200
MeV
needed for the treatment of deep-seated tumours.
This paper describes the design study of the full
3
GHz
Side Coupled Linac (modular structure, nine modules) and the construction and tests of the LIBO prototype (first module), which was built to accelerate protons from 62 to
74
MeV
with an RF peak power of
4.4
MW
. The items discussed are the beam dynamics parameters of the module (longitudinal and transverse acceptances), the constructional elements and procedures, the accuracies of the various mechanical elements, the cooling system, the RF tuning, the RF measurement and the RF power tests. These tests showed that, after a short conditioning time, the gradient in each of the four tanks of the module could reach
28.5
MV/m
, much larger than the nominal project value
(15.8
MV/m)
. The last section of the paper describes the successful acceleration tests performed at the Laboratori Nazionali del Sud of INFN in Catania with a solid-state
3
GHz
modulator lent by IBA.
An innovative Acoustic Positioning System for the km
3-scale neutrino telescope has been designed and is under realization within the KM3NeT Consortium. Compared to the Acoustic Positioning Systems ...used for the km
3 demonstrators, ANTARES and NEMO Phase 1, this new system is based on the “all data to shore” concept and it will permit the enhancement of detector positioning performances, reduction of costs and its use as real-time monitor of environmental acoustic noise.
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