71 research outputs found
Plasma ramps caused by outflow in gas-filled capillaries
Plasma confinement inside capillaries has been developed in the past years
for plasma-based acceleration to ensure a stable and repeatable plasma density
distribution during the interaction with either particles or laser beams. In
particular, gas-filled capillaries allow a stable and almost predictable plasma
distribution along the interaction with the particles. However, the plasma
ejected through the ends of the capillary interacts with the beam before the
inner plasma, affecting the quality of the beam. In this article we report the
measurements on the evolution of the plasma flow at the two ends of a 1 cm
long, 1 mm diameter capillary filled with hydrogen. In particular, we measured
the longitudinal density distribution and the expansion velocity of the plasma
outside the capillary. This study will allow a better understanding of the
beam-plasma interaction for future plasma-based experiments.Comment: 5 pages, 6 figures, EAAC 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
numerical studies on capillary discharges as focusing elements for electron beams
Abstract Active plasma lenses are promising technologies for the focusing of high brightness electron beams due to their radially symmetric focusing and their high field gradients (up to several kT/m). However, in a number of experimental situations, the transverse non-uniformity of the current density flowing in the lens causes beam emittance growth and increases the minimum achievable spot size. To study the physics of the capillary discharge processes employed as active plasma lenses, we developed a 2-D hydrodynamic computational model. Here, we present preliminary simulation results and we compare the computed magnetic field profile with one from literature, which has been experimentally inferred. The result of the comparison is discussed
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
Wake fields effects in dielectric capillary
Plasma wake-field acceleration experiments are performed at the SPARC LAB
test facility by using a gas-filled capillary plasma source composed of a
dielectric capillary. The electron can reach GeV energy in a few centimeters,
with an accelerating gradient orders of magnitude larger than provided by
conventional techniques. In this acceleration scheme, wake fields produced by
passing electron beams through dielectric structures can determine a strong
beam instability that represents an important hurdle towards the capability to
focus high-current electron beams in the transverse plane. For these reasons,
the estimation of the transverse wakefield amplitudes assumes a fundamental
role in the implementation of the plasma wake-field acceleration. In this work,
it presented a study to investigate which parameters affect the wake-field
formation inside a cylindrical dielectric structure, both the capillary
dimensions and the beam parameters, and it is introduced a quantitative
evaluation of the longitudinal and transverse electric fields
Overview of Plasma Lens Experiments and Recent Results at SPARC_LAB
Beam injection and extraction from a plasma module is still one of the
crucial aspects to solve in order to produce high quality electron beams with a
plasma accelerator. Proper matching conditions require to focus the incoming
high brightness beam down to few microns size and to capture a high divergent
beam at the exit without loss of beam quality. Plasma-based lenses have proven
to provide focusing gradients of the order of kT/m with radially symmetric
focusing thus promising compact and affordable alternative to permanent magnets
in the design of transport lines. In this paper an overview of recent
experiments and future perspectives of plasma lenses is reported
Soil carbon determination for long‐term monitoring revisited using thermo‐gravimetric analysis
Soils and the vadose zone are the major terrestrial repository of carbon (C) in the form of soil organic matter (SOM), more resistant black carbon (BC), and inorganic carbonate. Differentiating between these pools is important for assessing vulnerability to degradation and changes in the C cycle affecting soil health and climate regulation. Major monitoring programs from field to continent are now being undertaken to track changes in soil carbon (SC). Inexpensive, robust measures that can differentiate small changes in the C pools in a single measurement are highly desirable for long-term monitoring. In this study, we assess the accuracy and precision of thermo-gravimetric analysis (TGA) using organic matter standards, clay minerals, and soils from a national data set. We investigate the use of TGA to routinely differentiate between C pools, something no single measurement has yet achieved. Based on the kinetic nature of thermal oxidation of SC combined with the different thermodynamic stabilities of the molecules, we designed a new method to quantify the inorganic and organic SC and further separate the organic biogeochemically active SOM (as loss on ignition, LOI) from the resistant BC in soils. We analyze the TGA spectrums of a national soil monitoring data set (n = 456) and measure total carbon (TC) using thermal oxidation and also demonstrate a TC/LOI relationship of 0.55 for soils ranging from mineral soils to peat for the United Kingdom consistent with previous monitoring campaigns
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