On the upper limit of laser intensity attainable in non-ideal vacuum

The upper limit of the laser field strength in perfect vacuum is usually considered as the Schwinger field, corresponding to ~10^29W/cm^2. We investigate such limitations under realistic non-ideal vacuum conditions and find out that intensity suppression appears starting from 10^25W/cm^2, showing an upper threshold at 1026W/cm^2 level if the residual electron density in chamber surpasses 109cm^-^3. This is because the presence of residual electrons triggers the avalanche of quantum-electrodynamics cascade that creates copious electron and positron pairs. The leptons are further trapped within the driving laser field due to radiation-reaction, which significantly depletes the laser energy. The relationship between the attainable intensity and the vacuity is given according to particle-in-cell simulations and theoretical analysis. These results answer a critical problem on the achievable light intensity based on present vacuum conditions and provide a guideline for future 100's-Petawatt class laser development

Quasi-monochromatic bright gamma-ray generation from synchronized Compton scattering via azimuthal spatial-temporal coupling

High energy photons can be generated via inverse Compton scattering (ICS) in the collision between energetic electrons and intense laser pulse. The development of laser plasma accelerators promises compact and all-optical gamma-ray sources by colliding the electrons from laser wakefield accelerators to its high-power driving pulse reflected by a plasma mirror. However, the law of optical focusing hinders realization of both high photon yield and monochromatic spectrum in this scenario. We propose an azimuthal spatial-temporal convertor that decouples the focal field strength from laser spot size using helical parabolic geometry. It decomposes the driving laser beam into a pulse train of almost identical divergence angle and focal depth, creating synchronized ICS in the optimized linear regime. The scheme resolves the dilemma between high efficiency and narrow energy spread, facilitating the generation of monochromatic gamma-ray using high power lasers beyond relativistic field strengths

Adsorption of Tetracycline and Sulfamethoxazole on Crop Residue-Derived Ashes: Implication for the Relative Importance of Black Carbon to Soil Sorption

The main objective of this study was to investigate the key factors and mechanisms of antibiotic adsorption on crop residue-derived black carbon, as well as the relative importance of black carbon to the overall sorption to soil. Batch sorption experiments were performed for two reference antibiotics (sulfamethoxazole and tetracycline) on wheat- and maize-residue-derived black carbon. After removal of the mineral fraction from the raw black carbon by acidification, tetracycline exhibited less enhanced adsorption than sulfamethoxazole, implying stronger complexation of tetracycline on the mineral components. The antibiotic adsorption on the demineralized black carbon was very strong (The measured Kd was in the order of 103–105 L/kg). The adsorbent surface area-normalized adsorption of sulfamethoxazole was higher on the demineralized black carbon than on nonporous graphite due to the micropore-filling effect. The opposite trend observed for bulky tetracycline was attributed to the size-exclusion effect. Owing to the strong surface complexation and/or cation exchange reaction, sorption of tetracycline to Na+-exchanged montmorillonite, soil humic acids, and bulk soil was remarkably stronger than sulfamethoxazole. It was estimated that the contribution of black carbon to the overall sorption to bulk soil was important for sulfamethoxazole, but negligible for tetracycline

Mechanisms for strong adsorption of tetracycline to carbon nanotubes: A comparative study using activated carbon and graphite as adsorbents

Significant concerns have been raised over the presence of antibiotics including tetracyclines in aquatic environments. We herein studied single-walled carbon nanotubes (SWNT) and multi-walled carbon nanotubes (MWNT) as potential effective adsorbents for removal of tetracycline from aqueous solution. In comparison, a nonpolar adsorbate, naphthalene, and two other carbonaceous adsorbents, pulverized activated carbon (AC) and nonporous graphite, were used. The observed adsorbent-to-solution distribution coefficient (Kd, L/kg) of tetracycline was in the order of 104−106 L/kg for SWNT, 103−104 L/kg for MWNT, 103−104 L/kg for AC, and 103−105 L/kg for graphite. Upon normalization for adsorbent surface area, the adsorption affinity of tetracycline decreased in the order of graphite/SWNT > MWNT ≫ AC. The weaker adsorption of tetracycline to AC indicates that for bulky adsorbates adsorption affinity is greatly affected by the accessibility of available adsorption sites. The remarkably strong adsorption of tetracycline to the carbon nanotubes and to graphite can be attributed to the strong adsorptive interactions (van der Waals forces, π−π electron-donor−acceptor interactions, cation-π bonding) with the graphene surface. Complexation between tetracycline and model graphene compounds (naphthalene, phenanthrene, pyrene) in solution phase was verified by ring current-induced 1H NMR upfield chemical shifts of tetracycline moieties

Adsorption of Pharmaceutical Antibiotics on Template-Synthesized Ordered Micro- and Mesoporous Carbons

The presence of pharmaceutical antibiotics in aquatic environments poses potential human health and ecological risks. We synthesized ordered micro- and mesoporous carbons, and further conducted batch experiments to systematically examine their adsorption properties toward three antibiotics, sulfamethoxazole, tetracycline, and tylosin, in aqueous solution. In comparison, nonporous graphite, single-walled carbon nanotubes, and two commercial microporous activated carbons were included as additional adsorbents. Adsorption of low-sized sulfamethoxazole was stronger on the activated carbons than on other carbonaceous adsorbents resulting from the pore-filling effect; in contrast, due to the size-exclusion effect adsorption of bulky tetracycline and tylosin was much lower on the activated carbons, especially for the more microporous one, than on the synthesized carbons. After normalizing for adsorbent surface area, adsorption of tetracycline and tylosin on the synthesized carbons was similar to that on nonporous graphite, reflecting complete accessibility of the adsorbent surface area in adsorption. Additionally, compared with other porous adsorbents the synthesized carbons showed faster adsorption kinetics of tetracycline and tylosin, which was attributed to their regular-shaped, open and interconnected three-dimensional pore structure. The findings indicate that template-synthesized micro- and mesoporous carbons are promising adsorbents for the removal of antibiotics, particularly, the bulky and flexible-structured compounds, from aqueous solution

Adsorption of Sulfonamide Antibiotics to Multiwalled Carbon Nanotubes

The presence of sulfonamide antibiotics in aquatic environments has been recognized as an issue warranting consideration. In this study, we evaluated multiwalled carbon nanotubes (MWNT) as a potential effective adsorbent for removal of two sulfonamide antibiotics, sulfapyridine and sulfamethoxazole, from aqueous solutions. Nonporous, functionality-free graphite was included as a comparative adsorbent. Despite the very low hydrophobicity, the two sulfonamides adsorbed strongly to MWNT and graphite, a fact attributed to π−π electron coupling with the graphene surface of the adsorbent. For both sulfonamide antibiotics, similar patterns of pH-dependent adsorption were observed between MWNT and graphite, implying the predominance of graphene structures for the adsorption to MWNT. Moreover, the observed pH effects on adsorption indicate that the protonated neutral form of sulfonamide adsorbs much more strongly than the deprotonated anionic counterpart does. The effects of ionic strength (NaCl and CaCl2) and the presence of a dissolved soil humic acid on adsorption of the two antibiotics to MWNT and graphite were also assessed. Ring current-induced 1H NMR upfield chemical shifts further verified face-to-face complex formation between neutral sulfamethoxazole and model π-electron donor compounds (naphthalene, phenanthrene, and pyrene) in solution

Adsorption of Monoaromatic Compounds and Pharmaceutical Antibiotics on Carbon Nanotubes Activated by KOH Etching

The relatively low surface area and micropore volume of carbon nanotubes limit their potential application as effective adsorbents for hydrophobic organic contaminants. In this study, KOH dry etching was explored to prepare activated single-walled carbon nanotubes (SWNT) and multiwalled carbon nanotubes (MWNT) for adsorption of model monoaromatic compounds (phenol and nitrobenzene) and pharmaceutical antibiotics (sulfamethoxazole, tetracycline, and tylosin) in aqueous solutions. With activation, the specific surface area was increased from 410.7 m2/g to 652.8 m2/g for SWNT and from 157.3 m2/g to 422.6 m2/g for MWNT, and substantial pore volumes were created for the activated samples. Consistently, adsorption of the test solutes was enhanced 2−3 times on SWNT and 3−8 times on MWNT. Moreover, the activated carbon nanotubes showed improved adsorption reversibility for the selected monoaromatics, as compared with the pristine counterparts, which was attributed to the more interconnected pore structure and less pore deformation of the activated adsorbents. This is the first study on the adsorption/desorption of aqueous organic contaminants by KOH-activated carbon nanotubes. The findings indicate that KOH etching is a useful activation method to improve the adsorption affinity and adsorption reversibility of organic contaminants on carbon nanotubes

Zeolite-Templated Microporous Carbon As a Superior Adsorbent for Removal of Monoaromatic Compounds from Aqueous Solution

A microporous carbon with very high specific surface area and narrow pore size distribution was synthesized using Y zeolite as a template. The structural, porosity, and surface characteristics of the material were investigated by elemental analysis, N2 adsorption, powder X-ray diffraction, and Raman spectroscopy. The batch adsorption technique was performed to assess adsorption of three monoaromatic compounds, phenol, 1,3-dichlorobenzene, and 1,3-dinitrobenzene, on the synthesized carbon. Nonporous graphite, single-walled carbon nanotubes, and two commercial microporous activated carbons were also included as comparative adsorbents. The synthesized microporous carbon showed extraordinarily high adsorption affinity (comparable or higher than activated carbons and carbon nanotubes) for the three adsorbates, and very fast adsorption/desorption kinetics (equilibrium reached less than 3 h) and complete adsorption reversibility for phenol. These adsorption properties were attributed to the large hydrophobic surface area and the regular-shaped, open and interconnected three-dimensional pore structure of the synthesized microporous carbon. Additionally, with normalization of adsorbent surface area adsorption of a bulky solute, 1,2,4,5-tetrachlorobenzene, was prominently higher on the synthesized carbon than on the activated carbons, due to alleviated size exclusion effect. Findings of the present work highlight the potential of using zeolite-templated carbons as effective adsorbents for removal of hydrophobic organic contaminants in water treatment

Axionlike-particle generation by laser-plasma interaction

The hypothetical axion and axion-like particles, feebly coupled with photon, have not yet been found in any experiment. With the improvement of laser technique, much stronger but shorter quasi-static electric and magnetic fields can be created in laboratory using laser-plasma interaction, compared to the fields of large magnets, to help the search of axion. In this article, we discuss the feasibility of ALPs exploration using planarly or cylindrically symmetric laser-plasma fields as background and an x-ray free-electron laser as probe. Both the probe and the background fields are polarized such that the existence of ALPs in the corresponding parameter space will cause polarization rotation of the probe, which can be detected with high accuracy. Besides, a structured field in the plasma creates a tunable transverse profile for the interaction and improves the signal-to-noise ratio via phase-matching mechanism. The ALP mass discussed in this article ranges from $10^{-3}$ eV to 1 keV. Some simple schemes and estimations on ALP production and polarization rotation of probe photon are given, which reveals the possibility of future laser-plasma ALP source in laboratory

Twisting Relativistic Electrons Using Ultra-intense Circularly Polarized Lasers in the Radiation-dominated QED Regime

Relativistic vortex particles offer a promising avenue for investigating and manipulating processes in high-energy and nuclear physics, as they provide an additional degree of freedom in the form of orbital-angular-momentum (OAM). Despite the potential benefits, the generation and detection of these particles have proven to be a significant challenge. In this work, we present a new method for producing high-energy vortex electrons and $\gamma$-photons by colliding relativistic electrons with circularly polarized laser pulses in the radiation-dominated quantum electrodynamics (QED) regime. We use the laser-dressed vortex state to develop a nonlinear scattering theory, which allows us to understand the transfer of spin angular momenta (SAM) to intrinsic OAM in the highly nonlinear multi-photon process. The theory shows that electrons in the vortex state carry higher intrinsic OAM when radiation-reaction becomes significant, with the central OAM number proportional to the amount of energy taken by the $\gamma$-photon. This study provides an effective approach to generating high-energy vortex electron beams using laser intensities that are currently achievable. Additionally, the emission spectra of energetic electrons in vortex states are found to exhibit multi-peaks, which sets them apart from plane-wave electrons and makes them easier to distinguish