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

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

La inteligencia espiritual como estrategia para afrontar de manera constructiva el estrés laboral docente

Teachers´ activity is frequently threatened by the precarious conditions in which this practice is carried out. Teachers are exposed to different psychosocial risks that affect their performance and well-being. The present pre-test post-test study with a control group aims to examine the incidence of a intervention program based on the development of spiritual intelligence (SI) about the levels of stress reported by a group of 115 teachers from official educational institutions in Sincelejo (Sucre, Colombia). Within this intervention program, SI is understood as the ability to build a healthy (or adaptive) system of spiritual values or beliefs and adopt it as a lifestyle. SI encompasses three fundamental dimensions: cognitive (spiritual knowledge), affective (spiritual experience) and behavioral (contingency). Descriptive and inferential analysis were performed (intragroup and intergroup) and the variations of each institution were compared with their relationship to the teachers´ perception of the levels of stress before and after the intervention (measurements carried out on 2018 - 2019). The results show that teachers' perception of the levels of stress changed significantly from a high to a low risk factor.La actividad docente se ve amenazada frecuentemente por las condiciones precarias en las que se lleva a cabo. Los docentes están expuestos a diferentes riesgos de carácter psicosocial que afectan su desempeño y bienestar. El presente estudio pre-test post-test con grupo control tiene como objetivo examinar la incidencia de un programa de intervención basado en el desarrollo de la inteligencia espiritual (IE) sobre los niveles de estrés reportados por un grupo de 115 docentes de instituciones educativas oficiales de Sincelejo (Sucre, Colombia). Dentro de este programa de intervención, la IE se entiende como la capacidad de construir un sistema saludable (o adaptativo) de valores o creencias espirituales y de adoptarlo como estilo de vida. La IE abarca tres dimensiones fundamentalmente: cognitiva (conocimiento espiritual), afectiva (vivencia espiritual) y conductual (contingencia). Se hicieron análisis de tipo descriptivo e inferencial (intra-grupo e inter-grupo) y se compararon las variaciones de cada institución en relación con la percepción de los niveles de estrés de los docentes antes y después de la intervención (mediciones realizadas 2018 – 2019). Los resultados muestran que la percepción de los niveles de estrés de los docentes se transformaron significativamente, pasando de ser un factor de riesgo alto a uno bajo

Controlled density-downramp injection in a beam-driven plasma wakefield accelerator

This paper describes the utilization of beam-driven plasma wakefield acceleration to implement a high-quality plasma cathode via density-downramp injection in a short injector stage at the FLASHForward facility at DESY. Electron beams with charge of up to 105 pC and energy spread of a few percent were accelerated by a tunable effective accelerating field of up to 2.7 GV/m. The plasma cathode was operated drift-free with very high injection efficiency. Sources of jitter, the emittance and divergence of the resulting beam were investigated and modeled, as were strategies for performance improvements that would further increase the wide-ranging applications for a plasma cathode with the demonstrated operational stabilityComment: 11 pages, 9 figure

Progress in hybrid plasma wakefield acceleration

Plasma wakefield accelerators can be driven either by intense laser pulses (LWFA) or by intense particle beams (PWFA). A third approach that combines the complementary advantages of both types of plasma wakefield accelerator has been established with increasing success over the last decade and is called hybrid LWFA→PWFA. Essentially, a compact LWFA is exploited to produce an energetic, high-current electron beam as a driver for a subsequent PWFA stage, which, in turn, is exploited for phase-constant, inherently laser-synchronized, quasi-static acceleration over extended acceleration lengths. The sum is greater than its parts: the approach not only provides a compact, cost-effective alternative to linac-driven PWFA for exploitation of PWFA and its advantages for acceleration and high-brightness beam generation, but extends the parameter range accessible for PWFA and, through the added benefit of co-location of inherently synchronized laser pulses, enables high-precision pump/probing, injection, seeding and unique experimental constellations, e.g., for beam coordination and collision experiments. We report on the accelerating progress of the approach achieved in a series of collaborative experiments and discuss future prospects and potential impact

Particle-in-Cell Simulation Studies for Hybrid Laser-Plasma Accelerators and Plasma Eyepieces

Plasma wakefield accelerators driven by either laser or electron beams have shown great potential for future applications. Output beam quality from plasma has improved tremendously over the past decade. This, to a large extend, was enabled by progress in high-performance computing and numerical techniques based on particle-in-cell simulations. In this proceedings paper, we present two recent simulation studies, on hybrid plasma accelerators and on plasmabased laser focusing, opening new avenues in the application of compact accelerators and for the generation of high-brightness electron beams

Ponderomotively Assisted Ionization Injection in Plasma Wakefield Accelerators

An injection scheme is proposed to realize electron trapping in sub-relativistic plasma wakefield accelerators. A laser under oblique angle of incidence ionizes a dopant gas in plasma and ponderomotively accelerates the released electrons into 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 (PIC) simulations to demonstrate high-quality beam formation and acceleration with sub-micrometer normalized emittances and sub-percent uncorrelated energy spreads

Ponderomotively Assisted Ionization Injection in Plasma Wakefield Accelerators

An injection scheme is proposed to realize electron trapping in sub-relativistic plasma wakefield accelerators. A laser under oblique angle of incidence ionizes a dopant gas in plasma and ponderomotively accelerates the released electrons into 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 (PIC) simulations to demonstrate high-quality beam formation and acceleration with sub-micrometer normalized emittances and sub-percent uncorrelated energy spreads