8,533 research outputs found

    Transatlantic intimacies: The homoerotic affect worlds of nineteenth-century print culture

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    The thesis argues that during the late-nineteenth century, an alternative means of same-sex erotic communication was conceived of in transatlantically published American and British künstlerroman novels written by female authors. This alternative discourse was communicated affectively to initiated readers by way of metaphorical descriptions of painting, music, accompanying illustrations, and photography, and these novels all participate in the work of moving non-normative sexuality into the public sphere at the turn of the century. Through readings of works by Kate Chopin, Julia Magruder, and Amy Levy, the thesis explores the ways that these affective interactions were constructed, and the manner in which they hailed implied readers into an intimate public with one another. Ultimately, these novels offer a type of guide for members of the initiated intimate public that functioned as a signpost on the path that led to queer performativity as a way of life in the twentieth century

    Experimental characterization of active plasma lensing for electron beams

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    The active plasma lens represents a compact and affordable tool with radially symmetric focusing and field gradients up to several kT/m. In order to be used as a focusing device, its effects on the particle beam distribution must be well characterized. Here, we present the experimental results obtained by focusing an high-brightness electron beam by means of a 3 cm-long discharge-capillary pre-filled with Hydrogen gas. We achieved minimum spot sizes of 24 μ m (rms) showing that, during plasma lensing, the beam emittance increases due to nonlinearities in the focusing field. The results have been cross-checked with numerical simulations, showing an excellent agreement

    Focusing of High-Brightness Electron Beams with Active-Plasma Lenses

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    Plasma-based technology promises a tremendous reduction in size of accelerators used for research, medical, and industrial applications, making it possible to develop tabletop machines accessible for a broader scientific community. By overcoming current limits of conventional accelerators and pushing particles to larger and larger energies, the availability of strong and tunable focusing optics is mandatory also because plasma-accelerated beams usually have large angular divergences. In this regard, active-plasma lenses represent a compact and affordable tool to generate radially symmetric magnetic fields several orders of magnitude larger than conventional quadrupoles and solenoids. However, it has been recently proved that the focusing can be highly nonlinear and induce a dramatic emittance growth. Here, we present experimental results showing how these nonlinearities can be minimized and lensing improved. These achievements represent a major breakthrough toward the miniaturization of next-generation focusing devices

    Beam manipulation with velocity bunching for PWFA applications

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    The activity of the SPARC_LAB test-facility (LNF-INFN, Frascati) is currently focused on the development of new plasma-based accelerators. Particle accelerators are used in many fields of science, with applications ranging from particle physics research to advanced radiation sources (e.g. FEL). The demand to accelerate particles to higher and higher energies is currently limited by the effective efficiency in the acceleration process that requires the development of km-size facilities. By increasing the accelerating gradient, the compactness can be improved and costs reduced. Recently, the new technique which attracts main efforts relies on plasma acceleration. In the following, the current status of plasma-based activities at SPARC_LAB is presented. Both laser- and beam-driven schemes will be adopted with the aim to provide an adequate accelerating gradient (1–10 GV/m) while preserving the brightness of the accelerated beams to the level of conventional photo-injectors. This aspect, in particular, requires the use of ultra-short (<100fs) electron beams, consisting in one or more bunches. We show, with the support of simulations and experimental results, that such beams can be produced using RF compression by velocity-bunching

    Summary of working group 1: Electron beams from plasmas

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    Abstract We briefly summarize the contributions that have been presented in the Working Group 1 sessions, dedicated to electron beams from plasmas

    EuPRAXIA@SPARC_LAB: the high-brightness RF photo-injector layout proposal

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    At EuPRAXIA@SPARC_LAB, the unique combination of an advanced high-brightness RF injector and a plasma-based accelerator will drive a new multi-disciplinary user-facility. The facility, that is currently under study at INFN-LNF Laboratories (Frascati, Italy) in synergy with the EuPRAXIA collaboration, will operate the plasma-based accelerator in the external injection configuration. Since in this configuration the stability and reproducibility of the acceleration process in the plasma stage is strongly influenced by the RF-generated electron beam, the main challenge for the RF injector design is related to generating and handling high quality electron beams. In the last decades of R&D activity, the crucial role of high-brightness RF photo-injectors in the fields of radiation generation and advanced acceleration schemes has been largely established, making them effective candidates to drive plasma-based accelerators as pilots for user facilities. An RF injector consisting in a high-brightness S-band photo-injector followed by an advanced X-band linac has been proposed for the EuPRAXIA@SPARC_LAB project. The electron beam dynamics in the photo-injector has been explored by means of simulations, resulting in high-brightness, ultra-short bunches with up to 3 kA peak current at the entrance of the advanced X-band linac booster. The EuPRAXIA@SPARC_LAB high-brightness photo-injector is described here together with performance optimisation and sensitivity studies aiming to actual check the robustness and reliability of the desired working point.Comment: 5 pages,5 figures, EAAC201

    Neutron spectrometer for fast nuclear reactors

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    In this paper we describe the development and first tests of a neutron spectrometer designed for high flux environments, such as the ones found in fast nuclear reactors. The spectrometer is based on the conversion of neutrons impinging on 6^6Li into α\alpha and tt whose total energy comprises the initial neutron energy and the reaction QQ-value. The 6^6LiF layer is sandwiched between two CVD diamond detectors, which measure the two reaction products in coincidence. The spectrometer was calibrated at two neutron energies in well known thermal and 3 MeV neutron fluxes. The measured neutron detection efficiency varies from 4.2×10−4\times 10^{-4} to 3.5×10−8\times 10^{-8} for thermal and 3 MeV neutrons, respectively. These values are in agreement with Geant4 simulations and close to simple estimates based on the knowledge of the 6^6Li(n,α\alpha)tt cross section. The energy resolution of the spectrometer was found to be better than 100 keV when using 5 m cables between the detector and the preamplifiers.Comment: submitted to NI

    Characterization of self-injected electron beams from LWFA experiments at SPARC_LAB

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    The plasma-based acceleration is an encouraging technique to overcome the limits of the accelerating gradient in the conventional RF acceleration. A plasma accelerator is able to provide accelerating fields up to hundreds of GeV/mGeV/m, paving the way to accelerate particles to several MeV over a short distance (below the millimetre range). Here the characteristics of preliminary electron beams obtained with the self-injection mechanism produced with the FLAME high-power laser at the SPARC_LAB test facility are shown. In detail, with an energy laser on focus of 1.5 J1.5\ J and a pulse temporal length (FWHM) of 40 fs40\ fs, we obtained an electron plasma density due to laser ionization of about 6×1018 cm−36 \times 10^{18}\ cm^{-3}, electron energy up to 350 MeV350\ MeV and beam charge in the range (50−100) pC(50 - 100)\ pC.Comment: 6 pages, 11 figures, conference EAAC201

    Artroplastia total no cementada en la coxartrosis secundaria a displasia y luxación congenita de cadera

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    Se revisan 13 prótesis no cementadas implantadas en 12 paciente s que presentaban una coxartrosis secundaria a una displasia congénita de cadera. Los paciente s han sido seguidos más de 2 años de evolución. En todos los casos se utilizó la via de abordaje postero-lateral. Se implantó siempre la prótesis tipo PCA procediéndose en 7 casos a la realización, a nivel acetabular, de un alo o autoinjerto complementario. A nivel femoral se utilizaron 7 vástagos estándar, 3 medianos y 3 largos para facilitar la restauración del centro rotatorio original de la cadera. En los pacientes que presentaban una luxación importante se llevaron a cabo osteotomías de acortamiento a nivel subtrocantérico. Los pacientes han sido evaluados pre y post-operatoriamente tanto desde el punto de vista radiográfico como clínico. Desde el punto de vista clínico, se obtuvieron 8 resultados excelentes, 3 buenos, 1 discreto y 1 malo. Todos los pacientes estaban plenamente satisfechos con el resultado de la operación habiendo aumentado drásticamente su nivel de actividad. Solamente en un caso fue necesario practicar una intervención de revisión a los 4 años de la artroplastia primitiva, a causa de una grave osificación periprotésica. Solamente se tuvo una complicación intraoperatoria consistente en una fractura de la diálisis femoral.Thirteen non-cemented hips prostheses implanted in 12 patients with an osteoartritis secundar y to congenita l dislocation and dysplasi a of the hip wer e reviewed . Patients had a more than 2 years follow-up. The postero-lateral surgical approach was employed in all cases. On the acetabular side, we always used the PCA socket type. On the femoral side we implanted a PCA standard stem in 7 cases, mid stem in 3 cases and a long stem in 3. Acetabular bone autograft was added in 7 patients. In order to restore the original center of rotacion of the hip, in patients with a severe dislocation we perfomed also a shortening sub-trochanteric osteotomy; all the patients wer e evaluated pre and post-operatively with two separate forms. The first regarding the clinical evaluation, the second for radiographic assessment. All the patients were fully satisfied with the operation increasing dramatically their activity level. We obtained 8 excellent results, 3 good, 1 fair and 1 poor. One case required a revision for a severe heterotopic bone formation about 4 years after the first implant. We had a diaphyseal femoral fracture as the sole inly an intraoperative complication
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