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Preserving the quality of a positron beam in a plasma-based accelerator, where a wakefield suitable for positron transport and acceleration is generated by means of an electron filament, is challenging. This is due to the nature of the wakefields, characterized by focusing fields that vary nonlinearly in the transverse direction, and by accelerating fields that are non-uniform. These fields also change slice-by-slice along the beam. Maintaining a high beam quality is pivotal for application of positron beams in a plasma-based collider. In this paper, we show that an initial background plasma temperature can help mitigate the positron beam quality degradation in plasma-based accelerators that rely on electron filaments. We show that temperature effects broaden the electron filament and smooth radially both the non-linear transverse and the non-uniform longitudinal wakefields. Using warm plasmas opens up new possibilities to improve beam quality in several plasma-based positron acceleration concepts.

Reliable modeling of laser-plasma accelerators, where a short and intense laser pulse propagates in an underdense plasma over long distances, is a computationally challenging task. This is due to the great disparity among the scales involved in the modeling, ranging from the micrometer scale of the laser wavelength to, for instance, the meter scale of the laser-plasma interaction length for a multi-GeV-class laser-plasma accelerator. To reduce such imbalance, the time-averaged ponderomotive approximation may be used, where the plasma particle dynamics is analytically averaged over the laser frequency, and only spatiotemporal scales associated with the laser envelope are retained in the calculations, resulting in significant computational savings. In this paper, we characterize the accuracy and robustness of the time-averaged ponderomotive approximation for a range of laser parameters of interest for present and future laser-plasma accelerators, and we show that the error introduced by the averaging process is small in all relevant cases.

Dissipative capillary discharges form plasma channels which allow for high power laser guiding, enabling efficient electron acceleration in a laser wakefield accelerator. However, at the low plasma densities required to produce high-energy electrons, in order to avoid capillary wall damage, high power lasers need a tighter transverse confinement that cannot be achieved by the capillary discharge powered by Ohmic heating alone. The introduction of an additional laser for heating of the plasma leads to deeper and narrower plasma channels. Here we investigate the formation of laser-heated axially uniform plasma channels. We show that a high degree of longitudinal uniformity can be achieved despite significant evolution of the heater laser during its propagation through the channel.

Witness beam stability and preservation of its ultra-low emittance have been identified as critical challenges toward realizing a TeV-class, plasma-based linear collider. In fact, the witness bunch parameters required by a future TeV-class collider have been expected to trigger hosing instability and background ion motion, leading to emittance degradation and, potentially, to bunch loss. Recently, it has been shown that ion motion suppresses the hosing instability, and proper longitudinal bunch shaping can eliminate the ion-motion-induced emittance growth. In this paper, we propose and analyze a plasma-based method to generate the shaped bunches that enable emittance preservation in the presence of ion motion. The method is based on an adiabatic matching procedure, where a bunch with an initially untapered profile is injected in the plasma accelerator stage with an energy low enough that ion motion effects are initially small. As the bunch accelerates, it is adiabatically compressed, ion motion is gradually triggered, and the bunch slowly but continuously readjusts itself in the ion motion-perturbed wakefield acquiring the desired taper. The production of tapered witness bunch profiles that minimize energy spread and preserve emittance for collider-relevant parameters could enable the use of plasma-based accelerators for high-energy physics applications.

In this paper we discuss design considerations and beam dynamics challenges associated with laser-driven plasma-based accelerators as applied to multi-TeV-scale linear colliders. Plasma accelerators provide ultra-high gradients and ultra-short bunches, offering the potential for compact linacs and reduced power requirements. We show that stable, efficient acceleration with beam quality preservation is possible in the nonlinear bubble regime of laser-plasma accelerators using beam shaping. Ion motion, naturally occuring for dense beams (i.e., low emittance and high energy) severely damps transverse beam instabilities. Coulomb scattering by the background ions is considered and it is shown that the strong focusing in the plasma strongly suppresses scattering-induced emittance growth. Betatron radiation emission from the transverse motion of the beam in the plasma will result in beam power loss and energy spread growth; however for sub-100 nm emittances, the beam power loss and energy spread growth will be sub-percent for multi-TeV-class plasma linacs.

We would like to correct a misprint1 present in equation (1) of our paper [1]. The correct equation reads (Formula Presented).

We would like to correct a misprint1 present in equation (1) of our paper [1]. The correct equation reads (Formula Presented).

The principle of chromatic matching, i.e., using two laser modes of different geometric mode numbers and different colors so that they copropagate at the same group velocity, is proposed in order to realize the plasma undulator concept. Chromatic matching allows one to overcome group velocity slippage, whereby lower-order modes outrun higher-order ones, allowing for extended interaction lengths. The dephasing limit can be mitigated by using a special tapering of the plasma channel such that the electron bunch propagates in phase with the laser mode in addition to maintaining a constant undulator frequency. Furthermore, controlled dephasing is proposed as a means to induce chirp in the generated X-ray spectrum.

Guiding of relativistically intense laser pulses with peak power of 0.85 PW over 15 diffraction lengths was demonstrated by increasing the focusing strength of a capillary discharge waveguide using laser inverse bremsstrahlung heating. This allowed for the production of electron beams with quasimonoenergetic peaks up to 7.8GeV, double the energy that was previously demonstrated. Charge was 5pC at 7.8GeV and up to 62pC in 6GeV peaks, and typical beam divergence was 0.2mrad.

The use of higher-order modes is proposed to control the transverse wakefield structure generated by a laser pulse propagating through a plasma channel. This can be done in the quasilinear regime in both the Laguerre-Gaussian and Hermite-Gaussian bases for appropriate laser-plasma parameters, independent of the longitudinal field. Control of the wake can be achieved by using modes of different mode numbers but with matched phase velocities to generate tunable, matched laser propagation. The wake can be tuned by modifying the initial phase and amplitude of each mode. In addition, it is shown that two different higher order modes can propagate at the same group velocity by appropriately tuning the frequencies. Geometric and frequency tuning of the laser driver allows for greater control of the transverse phase-space of the accelerated electron bunch.

Mitigation of the beam hose instability in plasma-based accelerators is required for the realization of many applications, including plasma-based colliders. The hose instability is analyzed in the blowout regime including plasma ion motion, and ion motion is shown to suppress the hose instability by inducing a head-to-tail variation in the focusing force experienced by the beam. Hence, stable acceleration in plasma-based accelerators is possible, while, by use of proper bunch shaping, minimizing the energy spread and preserving the transverse beam emittance.

We would like to correct a typographical error which was introduced in Eqs. (5), (11), (14), (20a), and (20b) during revision of Ref. 1. The series expansion of the plasmaelectron phase space density to the first order of 〈x〉 and 〈px〉 [Eq. (5) in Ref. 1] correctly reads fp ≈ fp0 - cos θ (〈x〉∂r + 〈px〉∂pr)fp,0 The zeroth-order term, fp,0, was not printed in Ref. 1. Accordingly, the correct expansion of the wakefield potential [Eq. (11) in Ref. 1] is ψ(r,θ) ≈ ψ0(r) -cos θ Xp ∂r ψ0 (r), the correct expansion of the source term of the wakefield potential [Eq. (14) in Ref. 1] is S(r, θ) ≈ S0(r) - cos θ Xp ∂rS0(r), and the correct expansions of the force terms [Eqs. (20a) and (20b) in Ref. 1] are Fr,b ≈ Fr,b,o - cos θ Xb ∂rFr,b,0, Fr,b ≈ Fr,p,o - cos θ 〈x〈 ∂rFr,p,0, The zeroth order terms in Eqs. (5), (11), (14), (20a), and (20b) are missing in the printing of Ref. 1 but were fully taken into account for the calculation of all derived equations of the mathematical model. The developed mathematical model and physical conclusions in Ref. 1 are therefore all unaltered by, and consistent with, the above corrections.

© 2018 IOP Publishing Ltd. Laser plasma accelerators (LPA) offer an exciting possibility to deliver high energy, high brightness electrons beams in drastically smaller distance scales than is typical for conventional accelerators. As such, LPAs draw considerable attention as potential drivers for next generation light sources and for a compact linear collider. In order to asses the viability of an LPA source for a particular application, the brightness of the source should be properly characterized. In this paper, we present charge dependent transverse emittance measurements of LPA sources using both ionization injection and shock induced density down ramp injection, with the latter delivering smaller transverse emittances by a factor of two when controlling for charge density. The single shot emittance method is described in detail with a discussion on limitations related to second order transport effects. The direct role of space charge is explored through a series of simulations and found to be consistent with experimental observations.

© 2018 Author(s). Plasma structures based on leaky channels are proposed to filter higher-order laser mode content. The evolution and propagation of non-Gaussian laser pulses in leaky channels are studied, and it is shown that, for appropriate laser-plasma parameters, the higher-order laser mode content of the pulse may be removed while the fundamental mode remains well-guided. The behavior of multi-mode laser pulses is described analytically and numerically using envelope equations, including the derivation of the leakage coefficients, and compared to particle-in-cell simulations. Laser pulse propagation, with reduced higher-order mode content, improves guiding in parabolic plasma channels, enabling extended interaction lengths for laser-plasma accelerator applications.

© 2017 IOP Publishing Ltd. Detailed and reliable numerical modeling of laser-plasma accelerators (LPAs), where a short and intense laser pulse interacts with an underdense plasma over distances of up to a meter, is a formidably challenging task. This is due to the great disparity among the length scales involved in the modeling, ranging from the micron scale of the laser wavelength to the meter scale of the total laser-plasma interaction length. The use of the time-averaged ponderomotive force approximation, where the laser pulse is described by means of its envelope, enables efficient modeling of LPAs by removing the need to model the details of electron motion at the laser wavelength scale. Furthermore, it allows simulations in cylindrical geometry which captures relevant 3D physics at 2D computational cost. A key element of any code based on the time-averaged ponderomotive force approximation is the laser envelope solver. In this paper we present the accurate and efficient envelope solver used in the code INF&RNO (INtegrated Fluid & paRticle simulatioN cOde). The features of the INF&RNO laser solver enable an accurate description of the laser pulse evolution deep into depletion even at a reasonably low resolution, resulting in significant computational speed-ups.

© 2016 Elsevier B.V. A linear electron–positron collider based on laser-plasma accelerators using hollow plasma channels is considered. Laser propagation and energy depletion in the hollow channel is discussed, as well as the overall efficiency of the laser-plasma accelerator. Example parameters are presented for a 1-TeV and 3-TeV center-of-mass collider based on laser-plasma accelerators.

The advance in laser plasma acceleration techniques pushes the regime of the resulting accelerated particles to higher energies and intensities. In particular the upcoming experiments with the FLAME laser at LNF will enter the GeV regime with almost 1pC of electrons. From the current status of understanding of the acceleration mechanism, relatively large angular and energy spreads are expected. There is therefore the need to develop a device capable to measure the energy of electrons over three orders of magnitude (few MeV to few GeV) under still unknown angular divergences. Within the PlasmonX experiment at LNF a spectrometer is being constructed to perform these measurements. It is made of an electro-magnet and a screen made of scintillating fibers for the measurement of the trajectories of the particles. The large range of operation, the huge number of particles and the need to focus the divergence present unprecedented challenges in the design and construction of such a device. We will present the design considerations for this spectrometer and the first results from a prototype., Comment: 7 pages, 6 figures, submitted to NIM A

Objectives: To evaluate whether a training intervention can improve the ability of geriatricians to recognize depression in older persons. Design: Multicenter, cluster randomized clinical trial. Setting: Fourteen geriatric outpatient clinics in Italy, each representing the unit of randomization. Participants: After training, a total of 1,914 outpatients aged 65 years and older in both arms, not on antidepressant at entry, were blindly evaluated by the clinic geriatrician, in charge of routine clinical management, and by a field researcher, who formally diagnosed depression by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), taken as the criterion standard. Intervention: After randomization, geriatricians belonging to the intervention arm were assigned to receive a residential 3-day educational program on depression. Those in the control arm received a generic course on disease management in elderly people. Measurements: Sensitivity and specificity of the diagnosis of depression made by geriatricians, compared with the DSM-IV diagnosis. Results: Sensitivity and specificity were significantly higher in trained than in untrained geriatricians (49 vs 35% and 91 vs 88%, respectively; P=.002 in marginal regression models). Effectiveness of training was confirmed, adjusting for age, sex, and cognitive performance (P=.02). Conclusion: The ability of geriatricians to diagnose depression in older outpatients can be improved with a specific training intervention. Improvement of diagnostic performance might translate into more-appropriate clinical management.

A 250-TW laser system (FLAME - Frascati laser for acceleration and multidisciplinary experiments) is now in its commissioning phase in a new laboratory at LNF-INFN in the framework of the PLASMONX (Plasma acceleration and monochromatic X-ray generation) project. The laser will deliver25fs duration pulses with an energy up to 6J, at a 10Hz repetition rate. An ad hoc target area has also been designed and is currently being set up, allowing the first test experiments of electron laser wakefield acceleration to be carried out over the next few months in a safe, radiation-protected environment. An overview of the main features of the laser system and target area is given, along with a survey of the design and set-up of the self-injection test experiment, which is expected to reach the production of sub-GeV electron bunches.

Radiation Pressure Acceleration (RPA) by circularly polarized laser pulses is emerging as a promising way to obtain efficient acceleration of ions. We briefly review theoretical work on the topic, aiming at characterizing suitable experimental scenarios. We discuss the two reference cases of RPA, namely the thick target (Hole Boring) and the (ultra)thin target (Light Sail) regimes. The different scaling laws of the two regimes, the related experimental challenges and their suitability for foreseen applications are discussed.

Psoriasis is a multifactorial chronic inflammatory skin disease that often occurs in patients who are overweight or obese. In literature the connections between obesity and eating disorders are well known, but few studies have investigated the link between eating disorders and psoriasis. We hypothesized that Eating Disorders (ED) can be considered a psychogenic cofactors, which contribute to the development of obesity and metabolic syndrome in psoriatic patients, who are frequently prone to psychiatric comorbidity.From January to April 2011 we enrolled 100 consecutive psoriatic outpatients and a control group of 100 selected non-psoriatic outpatients, matched by age, gender, and BMI to the study group. The assessment battery was composed by the Psoriasis Area Severity Index (PASI) score, the Eating Disorder Inventory (EDI) and the Symptom Checklist-90 Revised (SCL-90-R®).Our data showed that most of EDI and SCL-90R subscales was mostly altered in psoriatic population compared to patients without psoriasis. Moreover, we noticed in patients with psoriasis an association between the progressive weight increase and an impairment on most of EDI subscales.Psoriasis is associated with psychopathological traits, which are frequently found in EDs. Since obesity makes psoriasis less susceptible to therapy and weight loss improves drug response, dermatologists should be alert to suspect the presence of this condition.

Male sex determination in humans is controlled by the SRY gene, which encodes a transcriptional regulator containing a conserved high mobility group box domain (HMG-box) required for DNA binding. Mutations in the SRY HMG-box affect protein function, causing sex reversal phenotypes. In the present study, we describe a 19-year-old female presenting 46,XY karyotype with hypogonadism and primary amenorrhea that led to the diagnosis of 46,XY complete gonadal dysgenesis. The novel p.E89K missense mutation in the SRY HMG-box was identified as a de novo mutation. Electrophoretic mobility shift assays showed that p.E89K almost completely abolished SRY DNA-binding activity, suggesting that it is the cause of SRY function impairment. In addition, we report the occurrence of the p.G95R mutation in a 46,XY female with complete gonadal dysgenesis. According to the three-dimensional structure of the human SRY HMG-box, the substitution of the conserved glutamic acid residue by the basic lysine at position 89 introduces an extra positive charge adjacent to and between the positively charged residues R86 and K92, important for stabilizing the HMG-box helix 2 with DNA. Thus, we propose that an electrostatic repulsion caused by the proximity of these positive charges could destabilize the tip of helix 2, abrogating DNA interaction.

Timber buildings are characterized by a thermal inertia lower than other technological solutions in construction. For this reason, some configurations may lead to higher cooling demand and poorer energy performance in hot climates, such as the Mediterranean ones. Possible improvement interventions often regard additional thermal mass but, if not accurately designed, they can worse significantly structural and seismic perfo rmance of timber buildings - which is of primary importance in many Italian regions. In this framework, the TimBEESt project studied some technological solutions for timber buildings in Light Timber Frame and Cross-Laminated Timber, able to improve the dynamic behaviour of the opaque components without worsening their seismic performance. First, the Italian territory was analysed in order to find classes of climate and seismic solicitations and energy and structural performances of reference LTF and CLT building models were simulated. Then, for each Italian province, specific interventions and improvements were defined and evaluated.

We address a particular instance where open quantum systems may be used as quantum probes for an emergent property of a complex system, as the temperature of a thermal bath. The inherent fragility of the quantum probes against decoherence is the key feature making the overall scheme very sensitive. The specific setting examined here is that of quantum thermometry, which aims to exploits decoherence as resource to estimate the temperature of a sample. We focus on temperature estimation for a bosonic bath at equilibrium in the Ohmic regime (ranging from sub-Ohmic to super- Ohmic), by using pairs of qubits in different initial states and interacting with different environments, consisting either of a single thermal bath, or of two independent ones at the same temperature. Our scheme involves pure dephasing of the probes, thus avoiding energy exchange with the sample and the consequent perturbation of temperature itself. We discuss the interplay between correlations among the probes and correlations within the bath, and show that entanglement improves thermometry at short times whereas, if the interaction time is not constrained, coherence rather than entanglement, is the key resource in quantum thermometry., Comment: 8 pages, 6 figures

A 250-TW laser system (FLAME - Frascati laser for acceleration and multidisciplinary experiments) is now in its commissioning phase in a new laboratory at LNF-INFN in the framework of the PLASMONX (Plasma acceleration and monochromatic X-ray generation) project. The laser will deliver < 25 fs duration pulses with an energy up to 6J, at a 10Hz repetition rate. An ad hoc target area has also been designed and is currently being set up, allowing the first test experiments of electron laser wakefield acceleration to be carried out over the next few months in a safe, radiation-protected environment. An overview of the main features of the laser system and target area is given, along with a survey of the design and set-up of the self-injection test experiment, which is expected to reach the production of sub-GeV electron bunches. © 2010 Taylor and Francis.

We solve Poisson's equation in d=2,3 space dimensions by using a spectral method based on Fourier decomposition. The choice of the basis implies that Dirichlet boundary conditions on a box are satisfied. A Green's function based procedure allows us to impose Dirichlet conditions on any smooth closed boundary, by doubling the computational complexity. The error introduced by the spectral truncation and the discretization of the charge distribution is evaluated by comparison with the exact solution, known in the case of elliptical symmetry. To this end boundary conditions on an equipotential ellipse (ellipsoid) are imposed on the numerical solution. Scaling laws for the error dependence on the the number K of Fourier components for each space dimension and the number N of point charges used to simulate the charge distribution are presented and tested. A procedure to increase the accuracy of the method in the beam core region is briefly outlined.

In this paper, a time series analysis of collisional effects in a numerical simulation of a coasting beam transverse dynamics is presented. The simulation performs a numerical integration of the Hamilton's equations of a two-dimensional system of particles, describing the transverse dynamics of the beam. Then, an analysis of the time series generated has been applied in order to describe the dynamics of the system by means of the mean field equations, with the addition of a stochastic process in order to model Coulomb collisions.

We propose a two dimensional model of charged particles moving along the z axis, on which they are focused by a linear attracting field. The particles are organized into parallel uniformly charged wires, which interact with a logarithmic potential. The mean field is described by the Poisson-Vlasov equation, whereas Hamilton's equations need to be solved to take into account the effect of collisions. The relaxation to the self consistent Maxwell-Boltzmann distribution is observed in numerical simulations for any initial distribution and the relaxation time scales linearly with the number N of wires, having fixed the total current. We prove that such scaling holds in the kinetic approach given by Landau's theory. To this end we use an approximation to the cross section of the cut-off logarithmic potential, which is asymptotically exact for large N. The drift term inherits the scaling law of the cross section and provides the required scaling for the relaxation time