Analytical model for the uncorrelated emittance evolution of externally injected beams in plasma-based accelerators

This article introduces an analytical formalism for the calculation of the evolution of beam moments and the transverse emittance for beams which are externally injected into plasma wakefield accelerators. This formalism is then applied to two scenarios with increasing complexity - a single beam slice without energy gain and a single beam slice with energy gain, both propagating at a fixed co-moving position behind the driver. The obtained results are then compared to particle-in-cell (PIC) simulations as well as results obtained using an semi-analytic numerical approach (SANA). We find excellent agreement between results from the analytical model and from SANA and PIC

Ponderomotive Injection in Plasma Wakefield Accelerators

A new electron injection scheme is proposed in sub-relativistic plasma wakefield accelerators. A transverse laser ionizes a dopant gas and ponderomotively accelerates the released electrons in the direction of wake propagation. This process enables electron trapping in the wakefield even for a wakefield potential below the trapping threshold. We study the scheme theoretically and by means of particle-in-cell simulations to demonstrate high-quality beam formation and acceleration with sub-micrometer normalized emittances and sub-percent uncorrelated energy spreads

Estudio de la consistencia interna y estructura factorial de tres versiones de la escala de Zung para ansiedad

Background: The Zung’s rating instrument for anxiety disorders has been used in several Colombian researches. Its internal consistency and factor structure have not been reported among university students. Objective: To calculate the internal consistency and explore the factor structure of three versions of the Zung’s rating instrument for anxiety disorders among university students. Method: Two-hundred and twenty-one medicine and psychology students of a private university in Cartagena, Colombia, completed the 20-item version of the Zung’s rating instrument for anxiety disorders. The mean of age of students was 20.5 years (SD=2.6), 64.4% were women, and 54.3% studied medicine. Cronbach alpha was computed and exploratory factor analysis was done for the three versions. Results: The 20-item version of the Zung’s rating instrument for anxiety disorders presents Cronbach alpha coefficient of 0.77 and three principal factors accounted for 40.1% of the total variance. The 10-item version showed Cronbach alpha of 0.83 and two-dimensional structure responsible of 54.0% of the total variance. The 5-item version showed Cronbach alpha of 0.74 and one-dimensional structure accounted for 49.5% of the total variance. Conclusions: The 10- and 5-item version of the Zung’s rating instrument for anxiety disorders present better psychometric properties than the original 20-item version. It is necessary to estimate the properties of these versions compared with a gold standard. Antecedentes: La escala de Zung para ansiedad se ha usado en varias investigaciones en Colombia. Sin embargo, no se ha informado la consistencia interna y la estructura de factores en estudiantes universitarios. Objetivo: Estimar la consistencia interna y la estructura factorial de tres versiones de la escala de Zung para ansiedad en estudiantes de una universidad privada de Cartagena, Colombia. Método: Doscientos veintiún estudiantes de medicina y psicología completaron la versión de 20 puntos de la escala de Zung para ansiedad. La media para la edad fue 20.5 (DE=2.6), 64.4% eran mujeres y 55.3% estudiaban medicina. Se calculó el alfa de Cronbach y se realizó un análisis de factores exploratorio para las tres versiones. Resultados: La escala de 20 puntos mostró un coeficiente de alfa de Cronbach de 0.77 y tres factores principales responsables de 40.1% de la varianza total. La versión de 10 puntos mostró una consistencia interna de 0.83 y una estructura bidimensional que explicaba 54% de la varianza. La versión de cinco puntos mostró una consistencia interna de 0.74 y una estructura unidimensional que daba cuenta de 49.5% de la varianza. Conclusiones: Las versiones de diez y cinco puntos de la escala de Zung para ansiedad presentan mejor comportamiento psicométrico que la versión original de 20 puntos. Se necesita estimar el comportamiento psicométrico de estas versiones frente a un criterio de referencia

Plasma Lenses for Relativistic Laser Beams in Laser Wakefield Accelerators

Focusing petawatt-level laser beams to a variety of spot sizes for different applications is expensive in cost, labor and space. In this paper, we propose a plasma lens to flexibly resize the laser beam by utilizing the laser self-focusing effect. Using a fixed conventional focusing system to focus the laser a short distance in front of the plasma, we can adjust the effective laser beam waist within a certain range, as if a variety of focusing systems were used with the plasma lens acting as an adjustable eyepiece in a telescope. Such a setup is a powerful tool for laser wakefield accelerator experiments in state-of-art petawatt laser projects and allows for scanning focal spot parameters.Comment: 12 pages, 11 figure

Wakefield-Induced Ionization injection in beam-driven plasma accelerators

We present a detailed analysis of the features and capabilities of Wakefield-Induced Ionization (WII) injection in the blowout regime of beam driven plasma accelerators. This mechanism exploits the electric wakefields to ionize electrons from a dopant gas and trap them in a well-defined region of the accelerating and focusing wake phase, leading to the formation of high-quality witness-bunches [Martinez de la Ossa et al., Phys. Rev. Lett. 111, 245003 (2013)]. The electron-beam drivers must feature high-peak currents ($I_b^0\gtrsim 8.5~\mathrm{kA}$) and a duration comparable to the plasma wavelength to excite plasma waves in the blowout regime and enable WII injection. In this regime, the disparity of the magnitude of the electric field in the driver region and the electric field in the rear of the ion cavity allows for the selective ionization and subsequent trapping from a narrow phase interval. The witness bunches generated in this manner feature a short duration and small values of the normalized transverse emittance ($k_p\sigma_z \sim k_p\epsilon_n \sim 0.1$). In addition, we show that the amount of injected charge can be adjusted by tuning the concentration of the dopant gas species, which allows for controlled beam loading and leads to a reduction of the total energy spread of the witness beams. Electron bunches, produced in this way, fulfil the requirements to drive blowout regime plasma wakes at a higher density and to trigger WII injection in a second stage. This suggests a promising new concept of self-similar staging of WII injection in steps with increasing plasma density, giving rise to the potential of producing electron beams with unprecedented energy and brilliance from plasma-wakefield accelerators

Flavour and polarisation in heavy neutrino production at e+ e- colliders

We analyse l W nu production at ILC, paying special attention to the role of the final lepton flavour and beam polarisation in the search for a new heavy neutrino N. We show that a sizeable coupling to the electron V_eN ~ 10^-2 is necessary to have an observable signal in any of the channels, despite the fact that the signal may be more visible in muon or tau final states. The non-observation of a heavy neutrino at ILC will improve the present upper bound on its mixing with the electron by more than one order of magnitude, V_eN < 0.007 for m_N between 200 and 400 GeV.Comment: 17 pages, 5 PS figures. References added. To be published in PL

Hábitos alimentarios del complejo Rhinella margaritifera (Laurenti, 1768) (AMPHIBIA: BUFONIDAE), Amazonas, Colombia

The present study was conducted with four species of the complex Rhinella margaritifera: Rhinella alata (Thominot, 1884), Rhinella castaneotica (Caldwell, 1991), Rhinella margaritifera (Laurenti, 1768) y Rhinella sp., to which they are analyzed aspects related to their eating habits and morphometry. The material that formed the basis for this work was collected in the locality the Quebradon Ayo, of La Pedrera, Amazonas department, Colombia. Anuran were examined 77 to which were principal components analysis to establish groupings by species and feeding habits; In addition there was a synthesis of previous studies on eating habits of the family Bufonidae, comparing them with the results obtained.El presente estudio se realizó con cuatro especies del Complejo Rhinella margaritifera: Rhinella alata (Thominot, 1884), Rhinella castaneotica (Caldwell, 1991), Rhinella margaritifera (Laurenti, 1768) y Rhinella sp., a las cuales se les analizaron aspectos relacionados con sus hábitos alimentarios y morfometria. El material que sirvió de base para este trabajo fue coleccionado en la localidad el Quebradón El Ayo, corregimiento de La Pedrera, departamento del Amazonas, Colombia. Fueron examinados 77 anuros a los cuales se les efectuaron análisis de componentes principales para establecer agrupaciones por especie y hábitos de alimentación; adicionalmente se realizó una síntesis de estudios anteriores sobre hábitos alimentarios de la familia Bufonidae, contrastándolos con los resultados obtenidos