A Positron Implantation Profile Estimation Approach for the PALS Study of Battery Materials

Positron annihilation spectroscopy is a powerful probe to investigate the interfaces in materials relevant for energy storage such as Li-ion batteries. The key to the interpretation of the results is the positron implantation profile, which is a spatial function related to the characteristics of the materials forming the battery. We provide models for the positron implantation profile in a cathode of a Li-ion battery coin cell. These models are the basis for a reliable visualization of multilayer geometries and their interfaces in thin cathodes of lithium-ion batteries

Quantum view of Li-ion high mobility at carbon-coated cathode interfaces

: Lithium-ion batteries (LIBs) are among the most promising power sources for electric vehicles, portable electronics and smart grids. In LIBs, the cathode is a major bottleneck, with a particular reference to its low electrical conductivity and Li-ion diffusivity. The coating with carbon layers is generally employed to enhance the electrical conductivity and to protect the active material from degradation during operation. Here, we demonstrate that this layer has a primary role in the lithium diffusivity into the cathode nanoparticles. Positron is a useful quantum probe at the electroactive materials/carbon interface to sense the mobility of Li-ion. Broadband electrical spectroscopy demonstrates that only a small number of Li-ions are moving, and that their diffusion strongly depends on the type of carbon additive. Positron annihilation and broadband electrical spectroscopies are crucial complementary tools to investigate the electronic effect of the carbon phase on the cathode performance and Li-ion dynamics in electroactive materials

Towards the formation of a positronium coherent beam

Positronium (Ps) has emerged as a promising test particle within the QUPLAS collaboration for investigating the gravitational effect. In this work, we present a novel approach to generate a monoenergetic and highly coherent Ps beam by creating a negative Ps ion (Ps$^-$, consisting of two electrons and one positron). The necessary positron beam is formed by using a high flux electron LINAC. Subsequently, we utilize a Fabry-Perot IR laser cavity operating at a wavelength of 1560 nm to selectively remove the extra electron. An alternative pulsed laser operating at a 3600 nm wavelength was studied to reduce broadening due to recoil and excitation. Here, we provide a Monte Carlo simulation to estimate the characteristics of the Ps beam, including its energy distribution and intensity profiles. The results obtained from this study will provide essential groundwork for future advancements in fundamental studies as Ps gravity measurements by using a Mach-Zehnder interferometer.Comment: 16 pages, 4 figure

Effect of ultra high-pressure homogenisation on natural-occurring micro-organisms in bovine milk

Abstract This study aimed to evaluate the effects of ultra high-pressure homogenisation (UHPH) on natural-occurring micro-organisms in bovine milk and compare the effects of heat and UHPH treatments. Whole raw milk was standardised at 3.5% and was processed using a Stansted High Pressure Homogeniser (model FPG11300, Stansted Fluid Power Ltd., Essex, UK). The microbiological quality of raw, high pasteurized (90ºC, 15 s) and pressure treated (200 and 300 MPa at inlet temperatures of 30 and 40ºC) milks was studied by enumerating total bacteria, psychrotrophic bacteria, coliforms, lactococci, lactobacilli and enterococci. UHPH treatments were as efficient (99.99%) as high-pasteurization treatment in reducing the total bacterial population, reaching important reductions (3-4 log cfu/ml). Lactococci count behaviour was similar to that of total bacteria count, reaching the same reductions. Psychrotrophic bacteria counts were not detected in high-pasteurized milks and were greatly reduced (~ 4 logs) in UHPH-treated milks. Coliforms, lactobacilli and enterococci were completed destroyed by both UHPH and heat treatments

A large-momentum-transfer matter-wave interferometer to measure the effect of gravity on positronium

This paper reports the study of a new interferometric configuration to measure the effect of gravity on positronium. A Mach–Zehnder matter-wave interferometer has been designed to operate with single-photon transitions and to transfer high momentum to a 200 eV positronium beam. The work shows the results and methods used to simulate the interferometer and estimate the operating parameters and the time needed to perform the experiment. It has been estimated that within less than 1 year, the acquisition time is sufficient to achieve a 10% accuracy level in measuring positronium gravitational acceleration, even with a poorly collimated beam, which is significant for theoretical models describing matter–antimatter symmetry. These results pave the way for single photon transition large momentum transfer interferometry with fast atomic beams, which is particularly useful for studies with antimatter and unstable atoms

Loss and revival of coherence in the interaction between a positron beam and a photon field

We study the interaction between a positron beam in the single-particle regime in an interferometric configuration and a microwave electromagnetic field. We discuss the conditions under which quantum interference can be affected by the field and we outline its possible experimental study in the framework of QUantum interferometry and gravitation with Positrons and LASers (QUPLAS) experiment

Fitoseidos (Acari: Phytoseiidae) en maíz y en vegetación de ribazo en Navarra. Densidades y composición de especies

En el presente trabajo se da cuenta de las especies de fitoseidos encontradas sobre Tetranychus turkestani en el cultivo de maíz y en la vegetación de ribazo durante los años 1992 a 1994 en Navarra. En total se han encontrado quince especies de fitoseidos, siendo la más abundante y frecuente en maíz Amblyseius californicus (McGregor) siendo también muy frecuente en plantas espontaneas. Del resto de las especies destacan Euseius stipulates (A.-H.) en maíz y Amblyseius cucumeris (Oudemans) en maíz y en ribazo. Se ha determinado la presencia a lo largo del período del cultivo de las diversas especies y las densidades de fitoseidos por especie vegetal, destacando en este caso el alto valor que alcanza el maíz. Asimismo se ha observado la diferente composición de la fauna de fitoseidos en los cuatro habitats implicados: planta de maíz, restos de la cosecha anterior, gramíneas y otras especies de ribazo.The present work identifies the predaceous phytoseid mites on Tetranychus turkestani on corn from Navarra, in the years 1992-1994. A total of 15 species have been found. Amblyseius californicus (McGregor) is the most abundant mite on corn and on the border vegetation, Euseius stipulatus (A.-H.) on corn and Amblyseius cucumeris (Oudemans) on Gramineae and on remains of the anterior corn crop. The phytoseid presence through corn life cycle has been determinated and the phytoseid density by vegetal species (the highest density is the corn too). Finally, the different composition of the phytoseid community it has been observed in the four implicated habitats: corn, remains of the anterior corn crop, gramineas and other border plants

infiltration and selective interactions at the interface in polymer oxide hybrid solar cells

Positron annihilation spectroscopy was used to characterize polymer-based hybrid solar cells formed by poly(3-hexylthiophene) (P3HT) finely infiltrated in a porous TiO2 skeleton. A step-change improvement in the device performance is enabled by engineering the hybrid interface by the insertion of a proper molecular interlayer namely 4-mercaptopyridine (4-MP). In order to obtain depth-resolved data, positrons were implanted in the sample using a variable-energy positron beam. The characteristics of the partially filled nanoporous structures were evaluated in terms of the depth profile of the positronium yield and the S-parameter. A quantitative evaluation of the pore filling in the deep region is given from the analysis of Coincidence Doppler Broadening taken at fixed implantation energy. We note a remarkable difference in terms of the positronium yield when the 4-MP interlayer is introduced, which means a better covering of P3HT on the porous surface

Annihilation of low energy antiprotons in silicon

The goal of the AE$\mathrm{\bar{g}}$IS experiment at the Antiproton Decelerator (AD) at CERN, is to measure directly the Earth's gravitational acceleration on antimatter. To achieve this goal, the AE$\mathrm{\bar{g}}$IS collaboration will produce a pulsed, cold (100 mK) antihydrogen beam with a velocity of a few 100 m/s and measure the magnitude of the vertical deflection of the beam from a straight path. The final position of the falling antihydrogen will be detected by a position sensitive detector. This detector will consist of an active silicon part, where the annihilations take place, followed by an emulsion part. Together, they allow to achieve 1$$ precision on the measurement of $\bar{g}$ with about 600 reconstructed and time tagged annihilations. We present here, to the best of our knowledge, the first direct measurement of antiproton annihilation in a segmented silicon sensor, the first step towards designing a position sensitive silicon detector for the AE$\mathrm{\bar{g}}$IS experiment. We also present a first comparison with Monte Carlo simulations (GEANT4) for antiproton energies below 5 MeVComment: 21 pages in total, 29 figures, 3 table