Closed-cycle noble gas recycling system for high-repetition rate high-harmonic generation.

We present a compact closed-loop recycling system for noble and inert gases. It has been developed for an extreme-ultraviolet (XUV) frequency comb based on high-harmonic generation at 100 MHz repetition rate. The system collects gas injected at several bars of backing pressure through a micrometer-sized nozzle into the laser-interaction region with a differential pumping system comprising turbomolecular pumps, and subsequently compresses the gas to a pressure of up to 200 bar. By drastically reducing the waste of expensive gases such as xenon and krypton, it enables the long operation times needed for spectroscopic measurements, as well as for continuous operation of the XUV frequency comb.

The catastrophic effects of groundwater intensive exploitation and Megadrought on aquifers in Central Chile: Global change impact projections in water resources based on groundwater balance modeling.

Central Chile is undergoing its most severe drought since 2010, affecting ecosystems, water supply, agriculture, and industrial uses. The government's short-term measures, such as increasing groundwater extraction (by 383 % from 1997 to 2022), are exacerbating the situation, leading to long-term hydrological deterioration. The objective of this research is to establish the main processes driving the water table depth evolution within Central Chile over the period 1979-2023. This is done by conducting groundwater balances on five major hydrological basins of Central Chile. For the Megadrought (MD) period (2010-2022), the groundwater level depths reflect not only the recharge variability but, especially, the forcing trend of groundwater withdrawals: they represent 35 % and 65 %, respectively, of the total phreatic level drawdown. This result underlines the dominant role played by groundwater withdrawals in the current delicate state of Central Chile's groundwater resources, while revealing that drought is a new complex phenomenon to deal with, in the midterm, to revert the current water resource trend in Central Chile. Our study moreover presents the impact of climate change in the basin in the framework of six different groundwater withdrawal scenarios. In the worst case (i.e., RCP8.5), the aquifer recharge decreases 18 % with respect to 1979-1997, which is the period assumed to be unaffected by the impact of MD and withdrawals. Such a reduction may be irrelevant in the dynamics of the aquifer system if the current extraction rate does not change. The estimated recovery time needed to reach aquifer conditions equal to those of the unaffected period is approximately 50 years.

Stringent test of QED with hydrogen-like tin.

Inner-shell electrons naturally sense the electric field close to the nucleus, which can reach extreme values beyond 1015 V cm-1 for the innermost electrons1. Especially in few-electron, highly charged ions, the interaction with the electromagnetic fields can be accurately calculated within quantum electrodynamics (QED), rendering these ions good candidates to test the validity of QED in strong fields. Consequently, their Lamb shifts were intensively studied in the past several decades2,3. Another approach is the measurement of gyromagnetic factors (g factors) in highly charged ions4-7. However, so far, either experimental accuracy or small field strength in low-Z ions5,6 limited the stringency of these QED tests. Here we report on our high-precision, high-field test of QED in hydrogen-like 118Sn49+. The highly charged ions were produced with the Heidelberg electron beam ion trap (EBIT)8 and injected into the ALPHATRAP Penning-trap setup9, in which the bound-electron g factor was measured with a precision of 0.5 parts per billion (ppb). For comparison, we present state-of-the-art theory calculations, which together test the underlying QED to about 0.012%, yielding a stringent test in the strong-field regime. With this measurement, we challenge the best tests by means of the Lamb shift and, with anticipated advances in the g-factor theory, surpass them by more than an order of magnitude.

Photoelectron tomography with an intra-cavity velocity-map imaging spectrometer at 100 MHz repetition rate.

We present a compact velocity-map imaging (VMI) spectrometer for photoelectron imaging at 100 MHz repetition rate. Ultrashort pulses from a near-infrared frequency comb laser are amplified in a polarization-insensitive passive femtosecond enhancement cavity. In the focus, multi-photon ionization (MPI) of gas-phase atoms is studied tomographically by rotating the laser polarization. We demonstrate the functioning of the VMI spectrometer by reconstructing photoelectron angular momentum distributions from xenon MPI. Our intra-cavity VMI setup collects electron energy spectra at high rates, with the advantage of transferring the coherence of the cavity-stabilized femtosecond pulses to the electrons. In addition, the setup will allow studies of strong-field effects in nanometric tips.

A new benchmark of soft X-ray transition energies of Ne , CO 2 , and SF 6 : paving a pathway towards ppm accuracy.

Abstract: A key requirement for the correct interpretation of high-resolution X-ray spectra is that transition energies are known with high accuracy and precision. We investigate the K-shell features of Ne , CO 2 , and SF 6 gases, by measuring their photo ion-yield spectra at the BESSY II synchrotron facility simultaneously with the 1s-np fluorescence emission of He-like ions produced in the Polar-X EBIT. Accurate ab initio calculations of transitions in these ions provide the basis of the calibration. While the CO 2 result agrees well with previous measurements, the SF 6 spectrum appears shifted by ∼ 0.5 eV, about twice the uncertainty of the earlier results. Our result for Ne shows a large departure from earlier results, but may suffer from larger systematic effects than our other measurements. The molecular spectra agree well with our results of time-dependent density functional theory. We find that the statistical uncertainty allows calibrations in the desired range of 1-10 meV, however, systematic contributions still limit the uncertainty to ∼ 40-100 meV, mainly due to the temporal stability of the monochromator energy scale. Combining our absolute calibration technique with a relative energy calibration technique such as photoelectron energy spectroscopy will be necessary to realize its full potential of achieving uncertainties as low as 1-10 meV.

Artificial recharge by means of careo channels versus natural aquifer recharge in a semi-arid, high-mountain watershed (Sierra Nevada, Spain).

The acequias de careo are ancestral water channels excavated during the early Al-Andalus period (8th-10th centuries), which are used to recharge aquifers in the watersheds of the Sierra Nevada mountain range (Southeastern Spain). The water channels are maintained by local communities, and their main function is collecting snowmelt, but also runoff from rainfall from the headwaters of river basins and distributing it throughout the upper parts of the slopes. This method of aquifer artificial recharge extends the availability of water resources in the lowlands of the river basins during the dry season when there is almost no precipitation and water demand is higher. This study investigates the contribution of the careo channels in the watershed of Bérchules concerning the total aquifer recharge during the 2014-2015 hydrological year. Several channels were gauged, and the runoff data were compared with those obtained from a semi-distributed hydrological model applied to the same hydrological basin. The natural infiltration of meteoric waters accounted for 52% of the total recharge, while the remaining 48% corresponded to water transported and infiltrated by the careo channels. In other words, the careo recharge system enhances by 92% the natural recharge to the aquifer. Our results demonstrate the importance of this ancestral and efficient channel system for recharging slope aquifers developed in hard rocks. The acequias de careo are nature-based solutions for increasing water resources availability that have contributed to a prosperous life in the Sierra Nevada. Its long history (>1200 years) suggests that the system has remarkable resilience properties, which have allowed adaptation and permance for centuries in drastically changing climatic and socioeconomic conditions. This recharge system could also be applied to -or inspire similar adaptation measures in- semi-arid mountain areas around the world where it may help in mitigating climate change effects.

Probes to measure kinetic and magnetic phenomena in plasmas.

Diagnostic tools are of fundamental importance in experimental research. In plasma physics, probes are usually used to obtain the plasma parameters, such as density, temperature, electromagnetic fields, and waves. This Review focuses on low-temperature plasma diagnostics where in situ probes can be used. Examples of in situ and remote diagnostics will be shown, proven by many experimental verifications. This Review starts with Langmuir probes and then continues with other diagnostics such as waves, beams, and particle collectors, which can provide high accuracy. A basic energy analyzer has been advanced to measure distribution functions with three-dimensional velocity resolution, three directions in real space and time resolution. The measurement of the seven-dimensional distribution function is the basis for understanding kinetic phenomena in plasma physics. Non-Maxwellian distributions have been measured in magnetic reconnection experiments, scattering of beams, wakes of ion beams, etc. The next advance deals with the diagnostics of electromagnetic effects. It requires magnetic probes that simultaneously resolve three field components, measured in three spatial directions and with time resolution. Such multi-variable data unambiguously yield field topologies and related derivatives. Examples will be shown for low frequency whistler modes, which are force-free vortices, flux ropes, and helical phase rotations. Thus, with advanced probes, large data acquisition and fast processing further advance in the fields of kinetic plasma physics and electromagnetic phenomena can be expected. The transition from probes to antennas will also be stimulated. Basic research with new tools will also lead to new applications.

An ultralow-noise superconducting radio-frequency ion trap for frequency metrology with highly charged ions.

We present a novel ultrastable superconducting radio-frequency (RF) ion trap realized as a combination of an RF cavity and a linear Paul trap. Its RF quadrupole mode at 34.52 MHz reaches a quality factor of Q ≈ 2.3 × 105 at a temperature of 4.1 K and is used to radially confine ions in an ultralow-noise pseudopotential. This concept is expected to strongly suppress motional heating rates and related frequency shifts that limit the ultimate accuracy achieved in advanced ion traps for frequency metrology. Running with its low-vibration cryogenic cooling system, electron-beam ion trap, and deceleration beamline supplying highly charged ions (HCIs), the superconducting trap offers ideal conditions for optical frequency metrology with ionic species. We report its proof-of-principle operation as a quadrupole-mass filter with HCIs and trapping of Doppler-cooled 9Be+ Coulomb crystals.

Isotopic content in high mountain karst aquifers as a proxy for climate change impact in Mediterranean zones: The Port del Comte karst aquifer (SE Pyrenees, Catalonia, Spain).

The objective of this work is to characterize the impact of climate change in the karst aquifer of the Port del Comte Massif (PCM). Six regional climate models (RCMs) from CLYM'PY Project are used to analyse the magnitude and trends of changes on precipitation and temperature (RCP4.5 and RCP8.5 scenarios) and how these changes propagate through the hydrogeological system as groundwater resources availability and the associated water isotopic content. The study uses the RCMs climate change forcings as input data to a combination of (1) a semi-distributed hydrological model for simulating the hydrodynamical response of the aquifer, and (2) a lumped parameter model for simulating the isotopic content in groundwater at the outlet of the aquifer. A mean decrease of 2.6% and 1.9% in yearly precipitation and a mean increase of 1.9 and 3.1 °C in average temperature is expected in PCM at the end of the 21st century in the RCP4.5 and RCP8.5 scenarios, respectively. This climate signal entering the hydrogeological system results in a mean decrease in recharge of 3.9% and 0.5% from rainfall and of 59.3% and 76.1% from snowmelt, and a decrease of 7.6% and 4.5% in total system discharge, but also generates an isotopic enrichment in groundwater discharge (δ18OGW) of 0.50‰ and 0.84‰, respectively. Moreover, from a long-term (2010-2100) perspective, the mean trend in δ18OGW is 0.7‰/100 yr and 1.2‰/100 yr for RCP4.5 and RCP8.5, respectively, resulting in easily measurable annual lapse rates with the current analytical methods.

XUV frequency comb production with an astigmatism-compensated enhancement cavity.

We have developed an extreme ultraviolet (XUV) frequency comb for performing ultra-high precision spectroscopy on the many XUV transitions found in highly charged ions (HCI). Femtosecond pulses from a 100 MHz phase-stabilized near-infrared frequency comb are amplified and then fed into a femtosecond enhancement cavity (fsEC) inside an ultra-high vacuum chamber. The low-dispersion fsEC coherently superposes several hundred incident pulses and, with a single cylindrical optical element, fully compensates astigmatism at the w0 = 15 µm waist cavity focus. With a gas jet installed there, intensities reaching ∼ 1014 W/cm2 generate coherent high harmonics with a comb spectrum at 100 MHz rate. We couple out of the fsEC harmonics from the 7th up to the 35th (42 eV; 30 nm) to be used in upcoming experiments on HCI frequency metrology.

Snowmelt as a determinant factor in the hydrogeological behaviour of high mountain karst aquifers: The Garcés karst system, Central Pyrenees (Spain).

Time series of environmental tracers (groundwater stable isotope composition, electrical conductivity and temperature) and concentration breakthrough curves of artificial tracers (uranine, eosine, amino-G and naphtionate) have been analyzed to characterize fast preferential and slow matrix in-transit recharge flows in the Paleocene-Eocene limestone aquifer of the Ordesa and Monte Perdido National Park, an alpine karst system drained by a water table cave, a rare hydrological feature in high mountain karst systems with similar characteristics. Snowmelt favors the areal recharge of the system. This process is reflected in the large proportion of groundwater flowing through the connected porosity structure of the karst aquifer, which amounts the 75% of the total system water discharge. From the perspective of water resources recovery, the water capacity of the fissured-porous zone (matrix) represents 99% of the total karst system storage. The volume associated to the karst conduits is very small. The estimated mean travel times are 9 days for conduits and 475 days for connected porosity. These short travel times reveal high vulnerability of the karst system to pollutants in broad sense and a great impact of climate change on the associated water resources.

Detection of metastable electronic states by Penning trap mass spectrometry.

State-of-the-art optical clocks1 achieve precisions of 10-18 or better using ensembles of atoms in optical lattices2,3 or individual ions in radio-frequency traps4,5. Promising candidates for use in atomic clocks are highly charged ions6 (HCIs) and nuclear transitions7, which are largely insensitive to external perturbations and reach wavelengths beyond the optical range8 that are accessible to frequency combs9. However, insufficiently accurate atomic structure calculations hinder the identification of suitable transitions in HCIs. Here we report the observation of a long-lived metastable electronic state in an HCI by measuring the mass difference between the ground and excited states in rhenium, providing a non-destructive, direct determination of an electronic excitation energy. The result is in agreement with advanced calculations. We use the high-precision Penning trap mass spectrometer PENTATRAP to measure the cyclotron frequency ratio of the ground state to the metastable state of the ion with a precision of 10-11-an improvement by a factor of ten compared with previous measurements10,11. With a lifetime of about 130 days, the potential soft-X-ray frequency reference at 4.96 × 1016 hertz (corresponding to a transition energy of 202 electronvolts) has a linewidth of only 5 × 10-8 hertz and one of the highest electronic quality factors (1024) measured experimentally so far. The low uncertainty of our method will enable searches for further soft-X-ray clock transitions8,12 in HCIs, which are required for precision studies of fundamental physics6.

100 MHz frequency comb for low-intensity multi-photon studies: intra-cavity velocity-map imaging of xenon.

We raise the power from a commercial 10 W frequency comb inside an enhancement cavity and perform multi-photon ionization of gas-phase atoms at 100 MHz for the first time, to the best of our knowledge. An intra-cavity velocity-map-imaging setup collects electron-energy spectra of xenon at rates several orders of magnitude higher than those of conventional laser systems. Consequently, we can use much lower intensities ${\sim}{{10}^{12}} \;{\rm W}/{{\rm cm}^2} $∼1012W/cm2 without increasing acquisition times above just a few seconds. The high rate and coherence of the stabilized femtosecond pulses are known to be transferred to the actively stabilized cavity and will allow studying purely perturbative multi-photon effects, paving the road towards a new field of precision tests in nonlinear physics.

Coherent laser spectroscopy of highly charged ions using quantum logic.

Precision spectroscopy of atomic systems1 is an invaluable tool for the study of fundamental interactions and symmetries2. Recently, highly charged ions have been proposed to enable sensitive tests of physics beyond the standard model2-5 and the realization of high-accuracy atomic clocks3,5, owing to their high sensitivity to fundamental physics and insensitivity to external perturbations, which result from the high binding energies of their outer electrons. However, the implementation of these ideas has been hindered by the low spectroscopic accuracies (of the order of parts per million) achieved so far6-8. Here we cool trapped, highly charged argon ions to the lowest temperature reported so far, and study them using coherent laser spectroscopy, achieving an increase in precision of eight orders of magnitude. We use quantum logic spectroscopy9,10 to probe the forbidden optical transition in 40Ar13+ at a wavelength of 441 nanometres and measure its excited-state lifetime and g-factor. Our work unlocks the potential of highly charged ions as ubiquitous atomic systems for use in quantum information processing, as frequency standards and in highly sensitive tests of fundamental physics, such as searches for dark-matter candidates11 or violations of fundamental symmetries2.

High-Precision Determination of Oxygen K_{α} Transition Energy Excludes Incongruent Motion of Interstellar Oxygen.

We demonstrate a widely applicable technique to absolutely calibrate the energy scale of x-ray spectra with experimentally well-known and accurately calculable transitions of highly charged ions, allowing us to measure the K-shell Rydberg spectrum of molecular O_{2} with 8 meV uncertainty. We reveal a systematic ∼450 meV shift from previous literature values, and settle an extraordinary discrepancy between astrophysical and laboratory measurements of neutral atomic oxygen, the latter being calibrated against the aforementioned O_{2} literature values. Because of the widespread use of such, now deprecated, references, our method impacts on many branches of x-ray absorption spectroscopy. Moreover, it potentially reduces absolute uncertainties there to below the meV level.

Detection of the 5p - 4f orbital crossing and its optical clock transition in Pr9.

Recent theoretical works have proposed atomic clocks based on narrow optical transitions in highly charged ions. The most interesting candidates for searches of physics beyond the Standard Model are those which occur at rare orbital crossings where the shell structure of the periodic table is reordered. There are only three such crossings expected to be accessible in highly charged ions, and hitherto none have been observed as both experiment and theory have proven difficult. In this work we observe an orbital crossing in a system chosen to be tractable from both sides: Pr[Formula: see text]. We present electron beam ion trap measurements of its spectra, including the inter-configuration lines that reveal the sought-after crossing. With state-of-the-art calculations we show that the proposed nHz-wide clock line has a very high sensitivity to variation of the fine-structure constant, [Formula: see text], and violation of local Lorentz invariance; and has extremely low sensitivity to external perturbations.

Secuelas morfo-funcionales en mujeres operadas de cáncer de mama en las regiones de la Araucanía y del Bío-Bío, Chile / Morphofunctional consequences in women operated for breast cancer of the region of Araucanía and Bío-Bío, Chile

El tratamiento quirúrgico del cáncer de mama puede dejar secuelas tardías tales como escápula alada, pérdida de movilidad articular del hombro, sobrepeso, etc. Basado en lo anterior, el objetivo del presente estudio fue describir las secuelas morfofuncionales en mujeres operadas de cáncer de mama de las regiones de la Araucanía y del Bío-Bío, Chile, explorando también si el procedimiento quirúrgico conllevaría a la presencia de escápula alada. Para ello, se realizó un estudio cuantitativo, observacional y de corte transversal en treinta mujeres operadas de cáncer de mama, de edades comprendidas entre 28 y 76 años (55,67±11,60). Un profesional entrenado evaluó peso, estatura, índice de masa corporal (IMC), índice de cintura cadera (ICC), rangos articulares de hombro (ROM, Range of Movement) y fuerza prensil, aplicándose además la prueba de Hoppenfeld para identificar escápula alada. Los resultados mostraron diferencias significativas en el ROM a la abducción de hombro (p<0,05), correlación significativa positiva de leve (r=0,370) a moderada (r=0,514) entre el ROM del lado afectado tanto para la flexión como la abducción con la fuerza prensil. Destacan, un IMC de 28,91±5,31 kg/m2, un ICC de 0,86±0,06 cm y la presencia de escápula alada en el 36,7 % de las participantes. No se encontró asociación entre el abordaje quirúrgico y la presencia de escápula alada. Hubo secuelas morfo-funcionales en las mujeres en estudio, destacándose las alteraciones en el rango de movimiento del miembro superior, sobrepeso, riesgo cardiovascular y la presencia de escápula alada, sin asociarse al tipo de abordaje quirúrgico.

Surgical treatment of breast cancer can leave late sequelae such as winged scapula, loss of joint mobility of the shoulder, overweight, etc. Based on the above, the objective of the present study was to describe the morpho-functional sequelae in women operated on for breast cancer from the regions of Araucanía and Del BíoBío, Chile, also exploring whether the surgical procedure would lead to the presence of scapula winged. For this, a quantitative, observational and cross-sectional study was conducted in thirty women operated on for breast cancer, aged between 28 and 76 years (55.67 ± 11.60). A trained professional evaluated weight, height, body mass index (BMI), hip waist index (ICC), shoulder joint ranges(ROM, Range of Movement) and prehensile strength, and applied the Hoppenfeld test to identify the winged scapula. The results showed significant differences in the ROM to shoulder abduction (p <0.05), positive significant correlation of mild (r = 0.370) to moderate (r = 0.514) between the ROM of the affected side for both flexion and abduction with prehensile force. Highlights, a BMI of 28.91 ± 5.31 kg / m2, an ICC of 0.86 ± 0.06 cm and the presence of winged scapula in 36.7 % of the participants. No association was found between the surgical approach and the presence of the winged scapula. There were morphofunctional sequelae in the women under study, highlighting the alterations in the range of movement of the upper limb, overweight, cardiovascular risk and the presence of the winged scapula, without being associated with the type of surgical approach.

Evidence of Extreme Ultraviolet Superfluorescence in Xenon.

We present a comprehensive experimental and theoretical study on superfluorescence in the extreme ultraviolet wavelength regime. Focusing a free-electron laser pulse in a cell filled with Xe gas, the medium is quasi-instantaneously population inverted by 4d-shell ionization on the giant resonance followed by Auger decay. On the timescale of ∼10 ps to ∼100 ps (depending on parameters) a macroscopic polarization builds up in the medium, resulting in superfluorescent emission of several Xe lines in the forward direction. As the number of emitters in the system is increased by either raising the pressure or the pump-pulse energy, the emission yield grows exponentially over four orders of magnitude and reaches saturation. With increasing yield, we observe line broadening, a manifestation of superfluorescence in the spectral domain. Our novel theoretical approach, based on a full quantum treatment of the atomic system and the irradiated field, shows quantitative agreement with the experiment and supports our interpretation.

A cryogenic radio-frequency ion trap for quantum logic spectroscopy of highly charged ions.

A cryogenic radio-frequency ion trap system designed for quantum logic spectroscopy of highly charged ions (HCI) is presented. It includes a segmented linear Paul trap, an in-vacuum imaging lens, and a helical resonator. We demonstrate ground state cooling of all three modes of motion of a single 9Be+ ion and determine their heating rates as well as excess axial micromotion. The trap shows one of the lowest levels of electric field noise published to date. We investigate the magnetic-field noise suppression in cryogenic shields made from segmented copper, the resulting magnetic field stability at the ion position and the resulting coherence time. Using this trap in conjunction with an electron beam ion trap and a deceleration beamline, we have been able to trap single highly charged Ar13+ (Ar XIV) ions concurrently with single Be+ ions, a key prerequisite for the first quantum logic spectroscopy of a HCI. This major stepping stone allows us to push highly-charged-ion spectroscopic precision from the gigahertz to the hertz level and below.