Main Pulse Research Articles

Temporal pre-pulse shaping in dual pulse laser produced plasma for the optimization of the EUV source in tin microdroplet system

Dual-laser beams interacting with small droplets of liquid tin are currently the most efficient systems for producing the 13.5 nm EUV photon radiation source required for the next generation microchips. Usually, EUV light is produced during the second main-pulse stage, while the pre-pulse (PP) is used for target preparation, i.e., droplet preheating, vaporization, and target deformation. However, the PP laser energy can be utilized more efficiently if the EUV producing plasma is being developed during the PP stage as well. In this work, we study the ways of optimization of the PP laser temporal shape to achieve conditions for maximum EUV output during the pre-pulse. The size of the deformed droplet is kept optimized for the following main laser pulse. Our simulations showed a significant increase in the EUV output at the pre-pulse stage when a ramping profile is used for the laser temporal shape. Using the ramped square pre-pulse produces 24% gain in the EUV output in comparison with the standard Gaussian temporal profile (i.e., regular Nd:YAG shape) for the same energy of the laser pulse.

Effect of the rising edge of ultrashort laser pulse on the target normal sheath acceleration of ions

Laser-driven ion acceleration is theoretically/numerically mostly studied with the assumption of an idealised main ultrashort pulse of the Gaussian temporal shape, where nanosecond/multi-picosecond pedestals and short prepulses preceding the main pulse can be incorporated in the form of modifications in the initial density profile of irradiated ionised targets. This paper shows that the relatively slowly rising edge (also called picosecond ramp) of the main ultrashort pulse, usually neglected in previous studies, can substantially change the efficiency of the target normal sheath acceleration of ions depending on the laser intensity. The rising edge can enhance ion acceleration at mildly relativistic laser intensities, but increases the divergence and reduces the cutoff energy of accelerated ions at highly relativistic intensities relevant to petawatt lasers.

A Comparative Study of the Power-law Relationship between the Pulse width and Energy of Precursor and Main Burst

In gamma-ray burst prompt emission, there is still no consistent conclusion if the precursor and main burst share the same origin. In this paper, we try to study this issue based on the relationship between pulse width and energy of the precursor and main burst. We systematically search the light curve data observed by Swift/BAT and Fermi/GBM, and find 13 long bursts with well-structured precursors and main bursts. After fitting the precursor light curve of each different energy channel with the Norris function, we find that there is not only a power-law relationship between precursor width and energy, but also a power-law relationship between the ratio of the rising width to the decaying width and energy. By comparing the relationship between the precursors and the main burst pulses, we find that the distribution of the precursors and the relationship between the power-law indices are roughly the same as those of the main burst. In addition, it is found that the precursor width distribution as well as the upper limit of the pulse width ratio does not exceed 1 and both are asymmetric, which are also consistent with the main burst. These indicate that the precursor and the main burst are indistinguishable, and the precursor and the main burst may have the same physical origin.

Angular distribution separation of the extreme ultraviolet emission and suprathermal ions with energy reduction

We have demonstrated angular distribution separation of the extreme ultraviolet (EUV) emission and suprathermal ions with a significant energy reduction for ions produced using dual pulse irradiation of a planar gadolinium (Gd) target. The pulse separation time between the pre-pulse and the main laser heating pulse was set at 30 ns, and the pre-plasma was irradiated at a distance of 50 μm above the target. Angular distributions of the EUV emission and the suprathermal ions were almost isotropic and followed a cos4θ distribution, respectively. The suprathermal ions were emitted normal to the target along the pre-pulse laser axis. The most probable energy of the suprathermal ions was less than 2 keV, while their maximum charge state was Gd6+ with the pre-plasma, compared to an energy of about 10 keV with a maximum charge state Gd15+ without the pre-plasma. The results suggest that the collector mirror position may be chosen to achieve a long lifetime, by avoiding damage from fast ion collisions.

Dual-microcomb generation via a monochromatically pumped dual-mode microresonator

Microcombs have enabled a host of cutting-edge applications from metrology to communications that have garnered significant attention in the last decade. Nevertheless, due to the thermal instability of the microresonator, additional control devices like auxiliary lasers are indispensable for single-soliton generation in some scenarios. Specifically, the increased system complexity would be too overwhelming for dual-microcomb generation. Here, we put forward a novel approach to mitigate the thermal instability and generate the dual-microcomb using a compact system. This process is akin to mode-division multiplexing, as the dual-microcombs are generated by pumping the dual-mode of a single Si3N4 microresonator with a continuous-wave laser. Both numerical simulations and experimental measurements indicate that this innovative technique could offer a straightforward way to enlarge the soliton existence range, allowing entry into the multistability regime and triggering another microcomb alongside the main soliton pulse. This outcome not only shines new light on the interaction mechanism of microresonator modes but also provides an avenue for the development of dual-microcomb-based ranging and low phase noise microwave generation.

Single-shot observation of nonlinear pulse splitting in a Kerr medium.

We report single-shot, time-resolved observation of self-steepening and temporal splitting of near-infrared, 50 fs, micro-joule pulses propagating nonlinearly in flint (SF11) glass. A coherent, smooth-profiled, 60-nm-bandwidth probe pulse that propagated obliquely to the main pulse through the Kerr medium recorded a time sequence of longitudinal projections of the main pulse's induced refractive index profile in the form of a phase-shift "streak," in which frequency-domain interferometry recovered with ∼10 fs temporal resolution. A three-dimensional simulation based on a unidirectional pulse propagation equation reproduced observed pulse profiles.

Model-Based Calibration and Control of Tailpipe Nitrogen Oxide Emissions in a Light-Duty Diesel Engine and Its Assessment through Model-In-The-Loop

The present paper investigates two different strategies for model-based calibration and control of tailpipe nitrogen oxide emissions in a light-duty 3.0 L diesel engine equipped with an aftertreatment system (ATS). The latter includes a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and an underfloor selective catalytic reduction (SCR) device, in which the injection of diesel exhaust fluid (DEF), marketed as ‘AdBlue’, is also taken into account. The engine was modeled in the GT-SUITE environment, and a previously developed model-based combustion controller was integrated in the model, which is capable of adjusting the start of injection of the main pulse and the total injected fuel mass, in order to achieve desired targets of engine-out nitrogen oxide emissions (NOx) and brake mean effective pressure (BMEP). First, a model-based calibration strategy consisting of the minimization of an objective function that takes into account fuel consumption and AdBlue injection was developed and assessed by exploring different weight factors. Then, a direct model-based controller of tailpipe nitrogen oxide emissions was designed, which exploits the real-time value of the SCR efficiency to define engine-out NOx emission targets for the combustion controller. Both strategies exploit the model-based combustion controller and were tested through a Model-in-the-Loop (MiL) under steady-state and transient conditions. The advantages in terms of tailpipe NOx emissions, fuel consumption, and AdBlue injection were finally discussed.

Observational signature of continuously operating drivers of decayless kink oscillation

Context. Decayless kink oscillations, which are nearly omnipresent in the solar corona, are believed to be driven by continuously operating energy supply. Aims. In this Letter, we investigate an external continuous excitation of an apparent decayless oscillation during an X1.1 flare on June 20, 2023 (SOL2023-06-20T16:42). Methods. The decayless kink oscillation was identified in the coronal loop at extreme ultraviolet (EUV) wavelengths and the associated flare quasi-periodic pulsations (QPPs) were simultaneously observed in passbands of hard X-ray (HXR), microwave, and ultraviolet (UV) emissions. Results. The kink oscillation is detected as a transverse oscillation of the coronal loop, which reveals five apparent cycles with an average period of about 130 ± 10 s. The oscillation amplitude does not show any significantly decay, suggesting a decayless oscillation. At the same time, the solar flare occurs in the vicinity of the oscillating loop and exhibits five main pulses in HXR, microwave, and UV emissions, which could be regarded as flare QPPs. They have similar periods of about 100–130 s, which may indicate successive and repetitive energy releases during the flare impulsive phase. The peak of each loop oscillation cycle appears to follow the pulse of the QPPs, suggesting that the transverse oscillation is closely associated with flare QPPs. Conclusions. Our observations support the scenario where the repetitive energy released following flare QPPs could be invoked as external, continuously operating drivers of the apparent decayless kink oscillation.

High-sensitivity Beamformed Observations of the Crab Pulsar's Radio Emission

We analyzed four epochs of beamformed European VLBI Network data of the Crab Pulsar at 1658.49 MHz. With the high sensitivity resulting from resolving out the Crab Nebula, we are able to detect even the faint high-frequency components in the folded profile. We also detect a total of 65,951 giant pulses, which we use to investigate the rates, fluence, phase, and arrival time distributions. We find that for the main pulse component, our giant pulses represent about 80% of the total flux. This suggests we have a nearly complete giant pulse energy distribution, although it is not obvious how the observed distribution could be extended to cover the remaining 20% of the flux without invoking large numbers of faint bursts for every rotation. Looking at the difference in arrival time between subsequent bursts in single rotations, we confirm that the likelihood of finding giant pulses close to each other is increased beyond that expected for randomly occurring bursts—some giant pulses consist of causally related microbursts, with typical separations of ∼30 μs—but also find evidence that at separations ≳100 μs the likelihood of finding another giant pulse is suppressed. In addition, our high sensitivity enabled us to detect weak echo features in the brightest pulses (at ∼0.4% of the peak giant pulse flux), which are delayed by up to ∼300 μs.

Elliptically polarized, nanosecond dual-pulse Raman laser with tunable pulse interval and pulse amplitude ratio

Dual-pulse solid state lasers with pulse interval of tens nanoseconds have been applied in laser-induced breakdown spectroscopy, laser drilling, medical treatment, and atmospheric monitoring. Here, a Yb:YAG/Cr4+:YAG/YVO4 passively Q-switched Raman laser has been developed for generating dual-pulse lasers with tunable pulse interval and elliptical polarization. Pulse interval and pulse amplitude ratio between peaks of satellite pulse and main pulse are controlled by adjusting the incident pump power (Pin). As Pin increases from 1.3 to 5.9 W, the pulse interval decreases from 63.1 to 36.3 ns, and the pulse amplitude ratio between peaks of satellite pulse and main pulse increases from 0.1 to 1.1 for dual-pulse Raman lasers. At Pin = 4.9 W, dual-pulse Raman laser with equal peak power of 1.7 kW and pulse interval of 40.2 ns is obtained. The pulse widths are 2.7 and 3.6 ns, and the pulse energy are 4.6 and 6.2 μJ for the main pulse and satellite pulse, respectively. The elliptical polarization with ellipticity tunable from 0.08 to 0.54 is obtained for dual-pulse passively Q-switched Raman laser as Pin increases. Such a nanosecond dual-pulse laser source has the potential to expand simple, compact portable and economical laser applications in various fields.

In situ U-Pb dating of carbonate veins in Cambrian shales constrains fluid flow and hydrocarbon evolution at the southeastern margin of the Upper Yangtze platform, southwestern China

Fluid flow in sedimentary basins not only impacts redistribution of the geothermal cycle and precipitation of ore deposits, but also exerts control on hydrocarbon migration and accumulation. However, reconstructing the history of fluid flow in basins that have experienced multiple tectonic deformation events is exceedingly difficult. Here, we examined petrography, in situ U-Pb geochronology, and rare earth element (REE) and C-O isotope geochemistry, as well as fluid inclusion microthermometry of fracture fillings within the Cambrian Niutitang Formation shales at the southeastern margin of the Upper Yangtze platform, southwestern China. The results show that four main fluid flow pulses are identified based on cathodoluminescence images, U-Pb ages, and geochemical data, namely, 446−428 Ma (fibrous calcite and barytocalcite), 343−329 Ma (calcite I), 113 Ma (calcite II), and 63 Ma (calcite III). The fibrous calcite (ca. 446 Ma) and barytocalcite (ca. 428 Ma) veins, corresponding to the late Caledonian Orogeny, show significantly positive Eu-Y anomalies, negative Ce anomalies, and enrichment in heavy REE, similar to their host rocks, suggesting that the mineral-forming fluids were derived mainly from dissolution of the host rocks. An abundance of bitumen inclusions with homogenization temperatures (Th) of 93.1−137.4 °C and high salinities (5−8 wt%) indicate that the first fluid flow pulse occurred during the oil generation stage in a closed fluid system. Calcite I (ca. 343−329 Ma) exhibits REE depletion and high Y/Ho ratios, a low fluid inclusion salinity (2−10 wt%) with Th = 78.4−125.8 °C, and C-O isotopic compositions similar to the underlying marine carbonates. This suggests that calcite I formed in an open fluid system, which was related to the transition from compression to extension during the Hercynian Orogeny. The pre-existing faults were reactivated and opened, resulting in the leakage and reconstruction of hydrocarbon reservoirs. Calcite II (ca. 113.4 Ma) has similar REE+Y patterns and C-O isotopic compositions to the host rocks. It contains abundant single-phase hydrocarbon gas (CH4) inclusions with high Th (164.1−211.1 °C) and salinity (6−14 wt%) values, indicating that the third phase fluid was derived largely from the host rocks and migrated during the early Yanshanian Orogeny. Lastly, calcite III (ca. 62.7 Ma) exhibits extremely low REE concentrations, low δ13CPDB [Peedee belemnite] values (−6.74‰), and low fluid inclusion salinities (0.3−7.0 wt%) with Th = 61.9−97.1 °C, suggesting that the fourth fluid flow pulse was affected by meteoric water to some extent. This can be interpreted to represent an open fluid system, which caused gas dispersion in the Niutitang Formation shales. Our findings provide important references for reconstructing the history of fluid flow in tectonically complex basins worldwide.

Terahertz radiation from shockwave front irradiated with femtosecond optical pulses

AbstractFemtosecond double optical pulse experiments with nanosecond time delay were conducted in air. Terahertz pulses were generated from laser plasmas produced by the irradiation with the main pulses on shockwave excited by the pre‐pulse illumination. Intensity of the terahertz pulses depends on the time difference Δt and relative position Δy between the pre‐ and main pulses. We found a characteristic dependence of the intensity of the terahertz pulses on Δy at a longer time delay, Δt = 14.7 ns, which has two maxima while only one maximum was observed when delay times were at and shorter than 9.7 ns. The results are discussed taking into account air density distribution of the shockwave. The terahertz emission spectroscopy shown here can be a useful technique for investigating density structure and its time variation of shockwave with high temporal resolution.

Study of the variability and components of the pulsar B0823+26 at a frequency of 111 MHz

ABSTRACT Studies of the pulsar B0823+26 have been carried out using the Large Phased Array (LPA) radio telescope. At a time span of 5.5 yr, the amplitudes of the main pulse (MP), postcursor (PC), and interpulse (IP) were evaluated in daily sessions lasting 3.7 min. It is shown that the ratio of the average amplitudes of MP in the bright (B) and quiet (Q) modes is 60. For B-mode, the average ratio of MP amplitudes to IP amplitudes is 65, and the ratio of MP amplitudes to PC amplitudes is 28. The number of sessions with a nulling is 4 per cent of the total number of sessions. Structure function (SF) and correlation function analysis of MP, IP, and PC amplitude variations of over a long-time interval allowed us to detect typical time scales 37 ± 5 d and one year. The analysis of time variations shows that the time scale of 37 d is well explained by refraction on inhomogeneities of interstellar plasma, which is distributed mostly quasi-uniformly in the line of sight. This scintillation makes the main contribution to the observed variability. Analysis of the structure function showed that there may be a few days variability. This time scale does not have an unambiguous interpretation but is apparently associated with the refraction of radio waves on the interstellar medium. One-year variability time scale has not been previously detected. We associate its appearance with the presence of a scattering layer on a closely located screen at a distance of about 50–100 pc from the Earth.

Complex diagnostic and numerical study of x-ray and particle emissions under relativistic ultra-short laser-solid interaction

In this report, we present the experimental results on the generation of x-ray emission and particle acceleration using high temporal contrast (∼10–9 at picosecond time scale), ultrashort (), relativistic () near-IR laser pulses interacting with Titanium foils. Complex diagnostics, including the energy spectra of accelerated electrons from both front and rear target sides, electron angular distribution and x-ray spectroscopy of the plasma emission were employed. Analysis of the characteristic radiation produced by highly charged Ti+20 ions led to the conclusion that laser-plasma interaction, which leads to the generation of keV hot plasma, occurs at plasma densities 10x higher than relativistic critical electron density. Numerical simulations, including hydrodynamic calculations to model pre-plasma, generated on nanosecond-picosecond time scale under our experimental conditions and relativistic particle-in-cell simulations for main pulse interaction with the plasma reproduce well electron energy and angular distributions. They show the onset of hole boring effect under near normal incidence that leads to plasma density steepening and enables penetration of high intensity laser radiation into the overcritical plasma to much higher densities (up to 30 ), what is in a good agreement with the results of x-ray spectroscopy.

2D-smoothing of laser beam fluctuations in optical compressor

We propose a modification of the four diffraction gratings Treacy compressor (TC)—a double-smoothing grating compressor (DSGC)—which enables smoothing of spatial fluctuations of a laser beam in two directions. Smoothing along the groves is due to oblique incidence on the gratings or tilted grooves. Smoothing in the direction normal to the grooves is achieved due to the use of nonidentical pairs of gratings. It is shown that the far-field fluence and the focal beam intensity after the DSGC are like those after the TC. Smoothing is a consequence of spatial harmonics lagging behind or overtaking the main pulse in proportion to the transverse wave vector. Analytical expressions are obtained for the spectrum of fluence fluctuations and fluence rms at the DSGC output. The efficiency of suppressing small-scale self-focusing in transmissive optical elements after the DSGC, for example, in the case of post-pulse compression is assessed.

Control of Spatiotemporal Localization of Infrared Pulses in Gas-Filled Capillaries Using Weak Ultraviolet Pulses

Manipulation of intense pulse propagation in gas-filled capillaries is desirable for various high-field applications. Tuning the parameters of the driving laser pulse and the working gas is the conventional approach, and it provides limited capability of control. Here we demonstrate through numerical simulations a practical scheme to control the propagation of intense pulses. A weak ultraviolet pulse is launched into a capillary with a negative delay with respect to a main infrared pulse. The pulses begin to temporally overlap due to dispersion. As the main pulse self-compresses, the control pulse is strongly red-shifted due to cross-phase modulation. The frequency shifts of the two pulses mitigate pulse walk-off and allow an efficient coupling, substantially extending the effective interaction length. This interesting phenomenon may benefit applications such as high-order harmonic generation.

Archean to Paleoproterozoic magmatic and metamorphic evolution of the Lofoten – Vesterålen area in northern Norway through zircon U-Pb and Hf isotopic analysis

Neoarchean (2.8–2.5 Ga) and Paleoproterozoic (2.5–1.6 Ga) crust preserves a record of major crustal growth events, the oldest supercontinent assemblies, and the likely transition to modern plate tectonics. The Lofoten–Vesterålen area in Norway underwent a multistage tectono-magmatic history from the Neoarchean to the Paleoproterozoic. In this region three main components are distinguished: 1) a granulite facies zone (GFZ); 2) an amphibolite facies zone (AFZ); and 3) an anorthosite-mangerite-charnockite-granite (AMCG) suite. New zircon U-Pb and Lu-Hf isotope data are used to investigate the evolution of this 2.7–2.6 and 1.9–1.8 Ga crust and evaluate how the developments fit in the global context of Earth’s crustal evolution. In-situ LASS–MC-ICPMS analyses were conducted on zircons to simultaneously determine U-Pb ages and Hf isotope compositions. Solution Hf isotope compositions were additionally obtained on zircons previously dated by ID-TIMS. In general, there is a good agreement between solution and in-situ data. Samples from the GFZ and AFZ both yield Neoarchean (2.7–2.6 Ga) and Paleoproterozoic (1.9–1.8 Ga) populations. Neoarchean populations have εHf(i) of +0.9 to −0.3; Paleoproterozoic populations have εHf(i) around −16 and −7 at ∼1.80 and ∼1.87 Ga, respectively. The AMCG suite was emplaced in two magmatic pulses: the early one at 1.87–1.86 Ga characterized by εHf(∼1.87 Ga) ∼ −7, and the main pulse at 1.80–1.79 Ga has εHf(∼1.80 Ga) between −4.0 and −15.0. Metamorphic overprinting recorded within the GFZ and the AMCG at ∼1.80 Ga is absent in the AFZ, supporting the hypothesis of a tectonic boundary between these domains. The Hf isotope compositions suggest that Paleoproterozoic magmatism was sourced from a combination of juvenile material and incorporated ancient crust, probably in variable proportions, as suggested by the variation in the isotope composition of the AMCG suite. Broadly chondritic Hf isotope compositions in Neoarchean rocks indicate the absence of significantly older crust as a source component. Main crustal growth events recorded in the Lofoten–Vesterålen area coincide with global age peaks and zircon Hf isotope record. The AMCG suite was emplaced during the Columbia supercontinent assembly. Neoarchean and Paleoproterozoic crust in the Lofoten–Vesterålen area exemplifies the elevated preservation potential in collisional tectonic settings.

GRB 221009A: Revealing a Hidden Afterglow during the Prompt Emission Phase with Fermi-GBM Observations

Recently, LHAASO reported the detection of the brightest-of-all-time GRB 221009A, revealing the early onset of a TeV afterglow. We analyze the spectral evolution of the X-ray/gamma-ray emission of GRB 221009A measured by the Fermi Gamma-ray Burst Monitor (GBM) during the dips of two prompt emission pulses (i.e., intervals T 0 + [300–328] s and T 0 + [338–378] s, where T 0 is the GBM trigger time). We find that the spectra at the dips transit from the Band function to a power-law function, indicating a transition from the prompt emission to the afterglow. After ∼T 0 + 660 s, the spectrum is well described by a power-law function, and the afterglow becomes dominant. Remarkably, the underlying afterglow emission at the dips smoothly connect with the afterglow after ∼T 0 + 660 s. The entire afterglow emission measured by GBM can be fitted by a power-law function F ∼ t −0.95±0.05, where t is the time since the first main pulse at T* = T 0 + 226 s, consistent with the TeV afterglow decay measured by LHAASO. The start time of this power-law decay indicates that the afterglow peak of GRB 221009A should be earlier than T 0 + 300 s. We also test the possible presence of a jet break in the early afterglow light curve, finding that both the jet break model and single power-law decay model are consistent with the GBM data. The two models cannot be distinguished with the GBM data alone because the inferred jet break time is quite close to the end of the GBM observations.

On space-time media that compute their own inverse

We show that it is possible to design a space-time medium such that the time scattering anticipates the space scattering in the medium and produces the exact inverse for the space scattering. Probing such a medium with a single broadband pulse thus also results in a single broadband pulse on the other side of the space-time heterogeneity. The transmission coefficient of such systems is unity. The reflection coefficient is non-zero, however, as both the time and spatial boundaries scatter waves in the backward direction. The time boundaries thus add energy. To construct a single pulse on the other side of a stack bounded by n interfaces, 2(n−1)−1 additional well-scaled and well-timed pulses need to be emitted following the main pulse, to cancel multiple reflections in the forward direction. Scattering at a time boundary doubles the number of wavepackets propagating in a medium. Furthermore, time refraction and reflection coefficients have the form required to produce well-scaled pulses. The required 2(n−1)−1 pulses can thus be efficiently generated by a single pulse interacting with n time boundaries. The contrasts across the time boundaries are the spatial contrasts in reverse. The time “thicknesses” of the boundaries are a simple function of the layer velocities.

Crop cultivation in the Talayotic settlement of Son Fornés (Mallorca, Spain): agricultural practices on the western Mediterranean islands in the first millennium bce

The Balearic Islands were colonised around the transition from the Chalcolithic to the Bronze Age, not earlier than 2300 cal bce and certainly much later than any central or eastern Mediterranean islands. The number of archaeobotanical records is low and consists mainly of cereals and a few pulses. We present here new results of our long-term study of Son Fornés, an archaeological site on Mallorca which was occupied since the beginning of the Iron Age Talayotic period (~ 850 cal bce) and until Roman times (123 bce onwards), in the Balearic Islands. In the Talayotic period of Son Fornés Hordeum vulgare var. vulgare (hulled barley) and Triticum aestivum/durum/turgidum (free-threshing wheat) were the main cereals grown and Vicia faba (broad bean) was the main pulse, while Avena sp. (oats) is considered to have been a weed but was nonetheless consumed and was probably in an early phase of being domesticated. For the subsequent post-Talayotic (ca. 550 − 250 bce), Classic I and Classic II, the Republican Roman occupation period (from 123 bce onwards) the databases are weak, displaying hulled barley as the main crop and broad bean as the main pulse. The archaeobotanical records of Ficus carica (fig), Olea europaea (olive) and Vitis vinifera (grapevine) represent wild or cultivated and domesticated forms. Prunus dulcis (almond) and Pinus pinea (stone pine) were found on Eivissa (Ibiza), pointing to a Phoenician introduction to the islands, while Phoenix dactylifera (date palm) and Castanea sativa (chestnut), found on Menorca, might have been brought in by the Romans. The number of crops being used on the Balearic Islands was limited when compared to sites of similar periods on the European mainland or the central and eastern Mediterranean islands. According to carbon isotope results of Δ13C, hulled barley grew under damper conditions than free-threshing wheat. The high δ15N values indicated that both crops were well-manured with animal dung during the entire occupation period.