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

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

EUPRAXIA@SPARC_LAB: Beam Dynamics studies for the X-band Linac

In the framework of the Eupraxia Design Study an advanced accelerator facility EUPRAXIA@SPARC_LAB has been proposed to be realized at Frascati (Italy) Laboratories of INFN. Two advanced acceleration schemes will be applied, namely an ultimate high gradient 1 GeV X-band linac together with a plasma acceleration stage to provide accelerating gradients of the GeV/m order. A FEL scheme is foreseen to produce X-ray beams within 3-10 nm range. A 500-TW Laser system is also foreseen for electron and ion production experiments and a Compton backscattering Interaction is planned together with extraction beamlines at intermediate electron beam energy for neutron beams and THz radiation production. The electron beam dynamics studies in the linac are here presented together with the preliminary machine layout.Comment: 5 pages, 3 figures, NIM-A proceedings of EAAC201

Electromagnetic and beam dynamics studies for high gradient accelerators at terahertz frequencies

THz radiation is one of the most appealing portion of the electromagnetic spectrum in terms of multi-disciplinary use in basic science and technology. Beyond the numerous applications, a great interest is its potential for future, compact linear accelerators. Conventional radio-frequency accelerating structures operating at the S and C band can reach gradients up to 30 - 50MV/m, respectively; higher accelerating gradients, of the order of 100MV/m, have been obtained with X-band cavities. THz-based accelerating structures enable operation at even higher gradient, potentially up to the GV/m scale, holding great potential for their application to free-electron lasers and linear colliders, for instance. Here we present electromagnetic and beam dynamics studies about the use of a dielectric loaded waveguide to accelerate electron bunches by mean of a narrow-band multi-cycle THz pulse. The excitation of the accelerating structure by the THz pulse and the bunch acceleration in the excited field are investigated through CST Microwave Studio and GPT simulations

Longitudinal phase-space manipulation with beam-driven plasma wakefields

The development of compact accelerator facilities providing high-brightness beams is one of the most challenging tasks in field of next-generation compact and cost affordable particle accelerators, to be used in many fields for industrial, medical and research applications. The ability to shape the beam longitudinal phase-space, in particular, plays a key role to achieve high-peak brightness. Here we present a new approach that allows to tune the longitudinal phase-space of a high-brightness beam by means of a plasma wakefields. The electron beam passing through the plasma drives large wakefields that are used to manipulate the time-energy correlation of particles along the beam itself. We experimentally demonstrate that such solution is highly tunable by simply adjusting the density of the plasma and can be used to imprint or remove any correlation onto the beam. This is a fundamental requirement when dealing with largely time-energy correlated beams coming from future plasma accelerators

Nailfold capillaroscopy abnormalities are associated with the presence of anti-endothelial cell antibodies in Sjogren's syndrome

[No abstract available

Epstein-Barr virus persistence and infection of autoreactive plasma cells in synovial lymphoid structures in rheumatoid arthritis.

OBJECTIVES: Rheumatoid arthritis (RA) is associated with an increased Epstein-Barr virus (EBV) blood DNA load, a robust immune response to EBV and cross-reactive circulating antibodies to viral and self-antigens. However, the role of EBV in RA pathogenesis remains elusive. Here, we investigated the relationship between synovial EBV infection, ectopic lymphoid structures (ELS) and immunity to citrullinated self and EBV proteins. METHODS: Latent and lytic EBV infection was investigated in 43 RA synovial tissues characterised for presence/absence of ELS and in 11 control osteoarthritis synovia using RT-PCR, in situ hybridisation and immunohistochemistry. Synovial production of anti-citrullinated protein (ACPA) and anti-citrullinated EBV peptide (VCP1/VCP2) antibodies was investigated in situ and in vivo in the severe combined immunodeficiency (SCID)/RA chimeric model. RESULTS: EBV dysregulation was observed exclusively in ELS+ RA but not osteoarthritis (OA) synovia, as revealed by presence of EBV latent (LMP2A, EBV-encoded small RNA (EBER)) transcripts, EBER+ cells and immunoreactivity for EBV latent (LMP1, LMP2A) and lytic (BFRF1) antigens in ELS-associated B cells and plasma cells, respectively. Importantly, a large proportion of ACPA-producing plasma cells surrounding synovial germinal centres were infected with EBV. Furthermore, ELS-containing RA synovia transplanted into SCID mice supported production of ACPA and anti-VCP1/VCP2 antibodies. Analysis of CD4+ and CD8+ T-cell localisation and granzyme B expression suggests that EBV persistence in ELS-containing synovia may be favoured by exclusion of CD8+ T cells from B-cell follicles and impaired CD8-mediated cytotoxicity. CONCLUSIONS: We demonstrated active EBV infection within ELS in the RA synovium in association with local differentiation of ACPA-reactive B cells

RF injector design studies for the trailing witness bunch for a plasma-based user facility

The interest in plasma-based accelerators as drivers of user facilities is growing worldwide thanks to its compactness and reduced costs. In this context the EuPRAXIA collaboration is preparing a conceptual design report for a multi-GeV plasma-based accelerator with outstanding electron beam quality to pilot, among several applications, the operation of an X-ray FEL, the most demanding in terms of beam brightness. Intense beam dynamics studies have been performed to provide a reliable working point for the RF injector to generate a high-brightness trailing witness bunch suitable in external injection schemes, both in particle beam and laser driven plasma wakefield acceleration. A case of interest is the generation of a witness beam with 1 GeV energy, less than 1 mm-mrad slice emittance and 30 pC in 10 fs FWHM bunch length, which turns into 3 kA peak current at the undulator entrance. The witness beam has been successfully compressed down to 10 fs in a conventional SPARC-like photo-injector and boosted up to 500 MeV in an advanced high-gradient X-band linac reaching the plasma entrance with 3 kA peak current and the following RMS values: 0.06% energy spread, 0.5 mm-mrad transverse normalised emittance and a focal spot down to 1 $\mu m$. RF injector studies are here presented with the aim to satisfy the EuPRAXIA requests for the Design Study of a plasma-based user facility.Comment: 5 pages, 7 figures, European Advanced Accelerator Concepts 201

Temperature analysis in the shock waves regime for gas-filled plasma capillaries in plasma-based accelerators

Plasma confinement represents a crucial point for plasma-based accelerators and plasma lenses because it can strongly affect the beam properties. For this reason, an accurate measurement of the plasma parameters, as plasma temperature, pressure and electron density, must be performed. In this paper, we introduce a novel method to detect the plasma temperature and the pressure for gas-filled capillaries in use at the SPARC-LAB test facility. The proposed method is based on the shock waves produced at the ends of the capillary during the gas discharge and the subsequent plasma formation inside it. By measuring the supersonic speed of the plasma outflow, the thermodynamic parameters have been obtained both outside and inside the capillary. A plasma temperature around 1.4 eV has been measured, that depends on the geometric properties and the operating conditions of the capillary

Focusing of high-brightness electron beams with active-plasma lenses

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