Frequency Rf Research Articles

Effect of defects on the thermomagnetic instabilities of superconducting radio-frequency cavities with a multilayer structure

Abstract Vortex motion can lead to significant energy dissipation, resulting in hot spots and thermomagnetic instabilities that are detrimental to the application of superconductors. This paper presents a theoretical examination of thermomagnetic instabilities triggered by vortex motion within a Nb$_{3}$Sn-I-Nb cavity featuring a multilayer structure. The investigation is conducted using Ginzburg-Landau theory in conjunction with the heat diffusion equation. The numerical simulations align well with experimental data from Nb$_{3}$Sn superconducting cavities. Given that the performance of SRF cavities is highly sensitive to various defects, this study also considers the interaction between vortices and these defects. It reveals the impact of edge cracks and impurities on temperature rise and the quality factor. The findings indicate that edge cracks significantly reduce the threshold field for thermomagnetic instability in superconducting radio-frequency (SRF) cavities. The performance of SRF cavities is influenced not only by the RF field amplitude and frequency but also by the length and number of edge cracks. These results offer valuable insights for evaluating the performance of SRF cavities subjected to RF fields.

Absorber-Free Mode-Locking of a Hybrid Integrated Diode Laser at Sub-GHz Repetition Rate

We demonstrate absorber-free passive and hybrid mode-locking at sub-GHz repetition rates, using a hybrid integrated extended cavity diode laser operating near 1550 nm. The laser is based on InP as a gain medium and a Si3N4 waveguide feedback circuit. Absorber-free Fourier domain mode-locking with ≈15 comb lines at around 0.2 mW total power is achieved with repetition rates around 500 MHz, using three highly frequency-selective micro-ring resonators that extend the on-chip cavity length to 0.6 m. To stabilize the repetition rate, hybrid mode-locking is demonstrated by weak RF modulation of the diode current. The RF injection reduces the Lorentzian linewidth component from 8.9 kHz to a detection-limited value of around 300 mHz. To measure the locking range of the repetition rate, the injected RF frequency is tuned with regard to the passive mode-locking frequency and the injected RF power is varied. The locking range increases approximately as a square-root function of the injected RF power. At 1 mW injection, a wide locking range of about 80 MHz is obtained. We also observe the laser maintaining stable mode-locking when the DC diode pump current is increased from 40 mA to 190 mA, provided that the cavity length is maintained constant with thermo-refractive tuning.

An Inductor‐Less Zero‐IF Down‐Conversion Mixer With Low Flicker Noise and High Conversion Gain

ABSTRACTThis paper presents a novel active inductor (AI) to improve the performance of a down‐conversion active mixer in terms of conversion gain (CG) and flicker noise. The proposed AI exhibits negative resistance and partially flat inductance over a wide frequency band of 0.5–4.5 GHz. The effect of inserting the AI between the source of the switching quad of a Gilbert cell mixer is theoretically analyzed. The proposed inductor‐less mixer, designed to operate at a 2.4‐GHz RF input frequency and a 10‐MHz IF output frequency, employs current reuse and self‐forward body bias (SFBB) techniques. The proposed circuit is simulated in Cadence Spectre‐RF using RF‐TSMC 0.18‐μm CMOS technology. Post‐layout simulations demonstrate that the proposed AI significantly reduces flicker noise by over 23 dB at an IF output frequency of 1 kHz and improves the CG by over 16 dB at an RF frequency of 2.4 GHz. The proposed mixer achieves a CG of 37.6 dB and a flicker noise corner frequency of 6 kHz. Additionally, it exhibits a third‐order intermodulation intercept point (IIP3) of −5.2 dBm and a double‐sideband noise figure (DSB‐NF) of 6.1 dB at the IF output frequency of 10 MHz. Operating with a 1.5‐V supply, the proposed mixer consumes 10.6 mW of power.

INCAPE23-A Fully Differential Active Inductor with Cascode Current Mirror Using 0.18-um Technology for RF Frequency

This paper introduces a fully differential CMOS active inductor integrated with a cascoded current mirror, tailored for applications within the RF frequency range. The active inductor design is meticulously realized using CMOS 0.18-µm technology. The circuit implementation comprises a fully differential cross-coupled pair of transistors, strategically employed to impart negative feedback, thereby enhancing the quality factor (Q). The cascoded current mirror functions as a pivotal biasing component, facilitating control over the current source to modulate negative feedback and Q factor tuning. Simultaneously, two resistors integrated into the differential structure are crucial in managing the frequency spectrum. Simulation results substantiate a Q factor of 16k, coupled with an inductance of 14 nH, prominently achieved at 3 GHz frequency. Additionally, the objective of achieving a robust Q factor at 3.5 GHz, amounting to 500, is successfully realized. Noteworthy is the adaptability in achieving a frequency range spanning 2 GHz to 3.6 GHz by manipulating resistor values. Furthermore, the study observes that manipulation of supply voltage and current source enables the tuning of Q factor values from 70 to 16k. A performance assessment, juxtaposed with previously published works, underscores the viability of the proposed active inductor for applications within the gigahertz frequency range of RF.

Reinterpreting radio frequency heating and current drive theory in a tokamak

Quasilinear treatments are widely used for tokamaks to evaluate radio frequency (rf) heating and current drive. Even though the core of a tokamak plasma is weakly collisional, the solution of the linearized kinetic equation is evaluated using unperturbed collisionless trajectories while often treating successive poloidal circuits of the passing (and trapped) particles as uncorrelated or nearly so. In addition, the most important effect of tokamak geometry, the mirror force, is usually mistreated or ignored when obtaining the solution. These concerning aspects of rf treatments are clarified by considering lower hybrid heating and current drive to illustrate that the electrons in resonance with the applied rf are enclosed by narrow collisional boundary layers, and that tokamak geometry makes it necessary to retain poloidal variation when solving a weakly collisional linearized kinetic equation. Other aspects such as collisional boundary layers at the trapped–passing boundary, cyclotron resonances, and the limitations of quasilinear theory are also considered. The new insights lead to a fundamentally different formulation and interpretation of the solution of the linearized Fokker–Planck equation used for rf quasilinear theory in a tokamak, while retaining many of the features that have contributed to its successful application to rf heating and current drive.

Feature importance for estimating rating of perceived exertion from cardiorespiratory signals using machine learning.

The purpose of this study is to investigate the importance of respiratory features, relative to heart rate (HR), when estimating rating of perceived exertion (RPE) using machine learning models. A total of 20 participants aged 18 to 43 were recruited to carry out Yo-Yo level-1 intermittent recovery tests, while wearing a COSMED K5 portable metabolic machine. RPE information was collected throughout the Yo-Yo test for each participant. Three regression models (linear, random forest, and a multi-layer perceptron) were tested with 8 training features (HR, minute ventilation (VE), respiratory frequency (Rf), volume of oxygen consumed (VO2), age, gender, weight, and height). Using a leave-one-subject-out cross validation, the random forest model was found to be the most accurate, with a root mean square error of 1.849, and a mean absolute error of 1.461 ± 1.133. Feature importance was estimated via permutation feature importance, and VE was found to be the most important for all three models followed by HR. Future works that aim to estimate RPE using wearable sensors should therefore consider using a combination of cardiovascular and respiratory data.

Quantifying spin-torque efficiency and magnetoresistance coefficient by microwave photoresistance in spin-torque ferromagnetic resonance

During the spin-torque ferromagnetic resonance (ST-FMR) measurement, the magnetization precession driven by the microwave field yields the radio frequency (rf) oscillating magnetoresistance and its time-averaged change (photoresistance). Here, we find that the strength of photoresistance can be directly determined by using dc bias current Idc modulating the symmetric component VS of the ST-FMR voltage spectrum. By measuring the angular dependence of photoresistance, we can quantify the in-plane and out-of-plane precession angles of ST-FMR, the actual rf current distribution in the magnetic and non-magnetic sublayers, and the magnitude of spin-torque and various magnetoresistance coefficients. These experimentally obtained values and analysis methods can more accurately quantify the spin-torque efficiency of both in-plane and out-of-plane spin polarizations by self-consistent calculation of the precession angle without harsh assumptions. And, we further confirm this universal method in three spintronic systems: the prototypical Pt/Py bilayer with anisotropic magnetoresistance (AMR), Py/Cu/Co20Tb80 spin valve trilayer with AMR and giant magnetoresistance, and [Co/Ni]3/Co/Pt multilayer with AMR and anisotropic interface magnetoresistance. This method eliminates potential deviation in calculating spin-torque efficiency by previously reported line shape analyzation and linewidth modulation methods of the ST-FMR technique and significantly extends its application range in characterizing spintronic materials and nanodevices.

Multidimensional Analysis of Physiological Entropy during Self-Paced Marathon Running.

The pacing of a marathon is arguably the most challenging aspect for runners, particularly in avoiding a sudden decline in speed, or what is colloquially termed a "wall", occurring at approximately the 30 km mark. To gain further insight into the potential for optimizing self-paced marathon performance through the coding of comprehensive physiological data, this study investigates the complex physiological responses and pacing strategies during a marathon, with a focus on the application of Shannon entropy and principal component analysis (PCA) to quantify the variability and unpredictability of key cardiorespiratory measures. Nine recreational marathon runners were monitored throughout the marathon race, with continuous measurements of oxygen uptake (V˙O2), carbon dioxide output (V˙CO2), tidal volume (Vt), heart rate, respiratory frequency (Rf), and running speed. The PCA revealed that the entropy variance of V˙O2, V˙CO2, and Vt were captured along the F1 axis, while cadence and heart rate variances were primarily captured along the F2 axis. Notably, when distance and physiological responses were projected simultaneously on the PCA correlation circle, the first 26 km of the race were positioned on the same side of the F1 axis as the metabolic responses, whereas the final kilometers were distributed on the opposite side, indicating a shift in physiological state as fatigue set in. The separation of heart rate and cadence entropy variances from the metabolic parameters suggests that these responses are independent of distance, contrasting with the linear increase in heart rate and decrease in cadence typically observed. Additionally, Agglomerative Hierarchical Clustering further categorized runners' physiological responses, revealing distinct clusters of entropy profiles. The analysis identified two to four classes of responses, representing different phases of the marathon for individual runners, with some clusters clearly distinguishing the beginning, middle, and end of the race. This variability emphasizes the personalized nature of physiological responses and pacing strategies, reinforcing the need for individualized approaches. These findings offer practical applications for optimizing pacing strategies, suggesting that real-time monitoring of entropy could enhance marathon performance by providing insights into a runner's physiological state and helping to prevent the onset of hitting the wall.

Numerical Simulation of the Dynamics of RF Capacitive Discharge in Carbon Dioxide

In this research, the one-dimensional fluid code SIGLO-rf was used to study the internal parameters of RF capacitive discharge in carbon dioxide, focusing mainly on time-averaged and spatio-temporal distributions of discharge parameters. With the help of this code, in the range of distances between electrodes d = 0.04 – 8 cm, RF frequencies f = 3.89 – 67.8 MHz, and values of carbon dioxide pressure p = 0.1 – 9.9 Torr, averaged over the RF period axial profiles of the density of electrons, positive and negative ions were calculated as well as potential and electric field strength. It is shown that the discharge plasma in CO2 contains electrons, positive ions, as well as negative ions. The negative ions of atomic oxygen are formed by the dissociative attachment of electrons to CO2 molecules. Studies of the spatio-temporal dynamics of plasma parameters (electron density, potential and electric field strength, as well as ionization and attachment rates) in RF capacitive discharge in CO2 showed that during half of the RF period, 1 to 3 ionization bursts are usually observed. They correspond to stochastic heating in the near-electrode sheath and the formation of passive and active double layers near the sheath boundaries. The passive double layer appears in the cathode phase and maintains the discharge plasma. The active layer is formed in the anodic phase and ensures a balance of positive and negative charges escaping to the electrode during the RF period. It was found that when the conditions pd = 2 Torr cm and fd = 27.12 MHz cm are met simultaneously, during half of the RF period, 4 intense ionization peaks are observed: resulting from stochastic heating, passive, active, and additional (auxiliary) double layers. The auxiliary double layer helps bring electrons to the surface of the temporary anode and occurs near its surface inside the near-electrode sheath. Using the similarity law, the conditions for the existence of these 4 ionization peaks in a wide range of RF frequencies, carbon dioxide pressures, and distances between electrodes were verified.

Effect of gas injection pattern on magnetically expanding rf plasma source

Abstract Argon gas is injected from a back plate having either a radial center hole or shower-patterned eight holes into a 13.3-cm-diameter and 25-cm-long radio frequency (rf) plasma source attached to a 43.7-cm-diameter and 65cm-long diffusion chamber under an expanding magnetic field, which resembles the magnetic nozzle rf plasma thruster. The source has a double-turn loop antenna powered by a 13.56 MHz rf generator at a maximum power level of ~2.8 kW in low-pressure argon, providing a plasma density of about 1018 m−3 in the source. A high plasma density and a slightly low electron temperature are obtained for the shower-pattered case in both the source tube and the diffusion chamber, compared with the center hole case, suggesting that the neutral density profile significantly affects the plasma density profile. This result will provide an improvement in the thruster performance by the gas injection pattern.

UNCERTAINTY EVALUATION USING LAW OF PROPAGATION AND MONTE CARLO SIMULATION METHODS WITH THE AUTORFPOWER MEASUREMENT SOFTWARE

RF power measurement is essential in RF and microwave metrology. For reliable and accurate power measurement, automatic measurement is preferred. A software application in C#, named AutoRFPower, was developed for automatic RF power measurement and uncertainty calculations at this study. According to the GUM document, this application is enhanced for uncertainty calculations by utilizing the Law of Propagation method and the Monte Carlo Simulation method. Trial measurements were performed at different RF power levels and frequencies between 50 MHz and 18 GHz using the AutoRFPower software. Law of Propagation and Monte Carlo Simulation uncertainty calculations were carried out by AutoRFPower based on the trial measurements and by the Oracle Crystal Ball simulation application. All measurements and their uncertainty calculations were compared with each other, and this study validated the uncertainty calculation of AutoRFPower. In addition, it was observed that in the Monte Carlo Simulation, uncertainty calculation results were non-symmetrical normal distribution, contrary to the assumption of symmetrical normal distribution according to the Low of Propagation method. Moreover, it has been observed that the statistical distribution of uncertainty changes depending on the dominant component of the parameters in the model function used for the uncertainty calculation with the Monte Carlo Simulation method.

Determination of the significance of atomic concentration on surface properties of Ba x Mg1-x F2 alloy coatings via microscopic and spectroscopic techniques.

Both BaF2 and MgF2 compounds and Ba x Mg1-x F2 alloy thin films were deposited on glass and silicon (Si) substrates in nanometric sizes (100 ± 10 nm) in a high vacuum environment by radio frequency (rf) magnetron sputtering. Using BaF2 (99% purity) and MgF2 (99% purity) target materials and adjusting the power levels applied to these targets, Ba x Mg1-x F2 alloy coatings at different atomic concentrations were formed under the same vacuum conditions. The microstructure and surface characteristics of the samples were analysed with the help of spectroscopic and microscopic methods. For the surface characterization, with scanning acoustic microscopy (SAM), 2-dimensional surface acoustic images of the samples were mapped, the surface acoustic impedance values were determined, and information about the micro hardness of the materials was obtained. Surface roughness values and grain sizes were obtained by taking 3-dimensional surface images of investigated materials using atomic force microscopy (AFM). Average nanometric particle sizes were determined for each sample with scanning electron microscopy (SEM), therefore, information about surface homogeneity was obtained. For the microstructural characterization, quantitative elemental analysis was performed using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDS), and stoichiometric ratios of atomic compositions were identified. By evaluating the data obtained from the microscopic and spectroscopic measurements, the effect of the atomic concentration parameter on the morphological properties of the material was determined. The usability of the produced binary fluoride alloy thin film coatings is promising for emerging optoelectronic, ceramic industry, biomedical and surface acoustic wave applications.

Ultrastructural, metabolic and genetic characteristics of determinants facilitating the acquisition of macrolide resistance by Streptococcus pneumoniae

AimsTo investigate the molecular events associated with acquiring macrolide resistance genes [mefE/mel (Mega) or ermB] in Streptococcus pneumoniae (Spn) during nasopharyngeal colonization. Methods and resultsGenomic analysis of 128 macrolide-resistant Spn isolates revealed recombination events in genes of the conjugation apparatus, or the competence system, in strains carrying Tn916-related elements. Studies using confocal and electron microscopy demonstrated that during the transfer of Tn916-related elements in nasopharyngeal cell biofilms, pneumococcal strains formed clusters facilitating their acquisition of resistance determinants at a high recombination frequency (rF). Remarkably, these aggregates comprise both encapsulated and nonencapsulated pneumococci that span extracellular and intracellular compartments. rF assessments showed similar rates regardless Mega was associated with large integrative and conjugative elements (ICEs) (>23 kb) or not (∼5.4 kb). The rF for Mega Class IV(c) insertion region (∼53 kb) was three orders of magnitude higher than the transformation of the capsule locus. Metabolomics studies of the microenvironment created by colonization of human nasopharyngeal cells revealed a link between the acquisition of ICEs and the pathways involving nicotinic acid and sucrose. ConclusionsPneumococcal clusters, both extracellular and intracellular, facilitate macrolide resistance acquisition, and ICEs were acquired at a higher frequency than the capsule locus. Metabolic changes could serve as intervention targets.

AC Loss Measurement in Nb3Sn Coil for a New Fast Switching-field MR Concept Magnet.

The ability to perform magnetic resonance (MR) imaging or spectroscopy at significantly different magnetic field strengths during scanning holds great potential for expanding the range of contrast parameter options and obtaining high "superthermal" spin polarization for increased signal-to-noise ratio (SNR) or measuring certain spins at what would otherwise be impractically high RF frequencies. Enabling measurements at multiple field strengths heretofore has required either rapidly altering the strength of a resistive magnet with pulsed currents or shuttling the specimen between two field regions. We propose a novel approach to switching-field MR that we expect to be practical for live animal and ultimately human imaging. In this paper we propose the design of a liquid-helium-free fast switching-field MR magnet that can change the field very quickly in time (≤ 1 s) between significantly different field strengths. For this magnet, two types of Nb3Sn wire are selected, and AC loss is measured by electrical method, and characteristics are analyzed.

Square Parametric Excitation: A Digital Resonant Method for the Quadrupole Ion Trap.

Digital ion trap technology is an alternate method for driving quadrupole ion traps and mass filters using variable frequency, fixed amplitude RF square waves in place of variable amplitude, fixed frequency RF sine waves. This technique offers some advantages such as an increase in the high mass analysis range by varying frequency and lower overall voltage requirements. Here, we present a complex square waveform developed for resonant parametric excitation in a quadrupole linear ion trap. Unlike traditional resonance methods, the driving RF square wave and auxiliary square wave are coupled using the same digital circuitry without the need for transformer coupling. In this work, we use this complex waveform to selectively excite the first order parametric resonances of ion motion. The square parametric excitation method presented here employs a simple and repetitive circuit design consisting of a low-voltage waveform generator followed by a series of high-voltage MOSFET switches. This design allows for resonance methods to be easily implemented in the all-digital quadrupole. The complex square waveform can perform the same useful functions as sine wave auxiliary signals, such as selective mass elimination and mass isolation. We also demonstrate that the mass resolution performance and S/N of our digital mass spectrometer is improved by applying the complex square waveform during ion ejection.

Impact of beam coupling impedance on crab cavity noise induced emittance growth

Crab cavities will be deployed as a part of the High Luminosity Large Hadron Collider (HL-LHC) upgrade to mitigate the luminosity reduction induced by the crossing angle at the main experiments (ATLAS and CMS). Two prototype crab cavities have been installed in the CERN Super Proton Synchrotron (SPS) in 2018 for studies with proton beams. An issue of concern is the transverse emittance growth induced by noise in the crab cavity radio frequency (rf) system, which is anticipated to limit the performance of the HL-LHC. In measurements conducted in the SPS in 2018, the crab cavity noise-induced emittance growth was measured to be a factor of 4 lower than predicted from the existing analytical models. In this paper, it is shown that the observed discrepancy is explained by damping effects from the beam coupling impedance, which were not included in the models up to now. Using the van Kampen mode approach, a new theory is developed, suggesting that the impedance can separate the coherent tune from the incoherent spectrum leading to an effective reduction of the crab cavity rf noise-induced emittance growth. This mechanism is validated in tracking simulations using the SPS impedance model as well as in dedicated experimental measurements conducted in the SPS in 2022. The implications for the HL-LHC project are discussed. Published by the American Physical Society 2024

Structural, linear/nonlinear optical characteristics and radiation shielding effectiveness of Cu4O3/Cu2O dual-phase thin films: Influence of oxygen flow rate in reactive sputtering process

In the present work, we investigated the impact of oxygen flow rate on the structural, linear, and nonlinear optical characteristics while also evaluating the radiation shielding effectiveness during reactive radio frequency (rf) sputtering in the deposition of Cu4O3/Cu2O dual-phase thin films. Microstructural analysis revealed distinct changes with increased OFRs, switching from a Cu2O cubic structure phase to a Cu4O3 tetragonal structure phase. The XRD patterns revealed good crystallinity, and the crystallite size of the film reduced from 28 nm to 22 nm, and the microstrain exhibited an opposing trend as the oxygen flow rate increased. In contrast, investigating the optical properties of dual-phase Cu4O3 and Cu2O thin films using UV–Vis–NIR spectroscopy revealed intriguing trends in the absorbance spectra, absorption coefficient, and extension index. The apparent bandgap increases from 2.0 eV to 2.62 eV with increasing oxygen flow rates. In addition, nonlinear optical parameters, including the nonlinear refractive index n2 linear, nonlinear sensitivity (χ1 and χ3), and nonlinear absorption coefficient βc were calculated to demonstrate the applicability of these materials. The dual-phase structure of the films enhances their potential for effective radiation shielding. Our findings provide valuable insights into the design of properties of Cu4O3/Cu2O dual-phase thin films for applications ranging from photoelectric and nonlinear optical devices to radiation shielding effectiveness.

The Role of Pain and Blood Simulation of Nonsuicidal Self-Injury in Emotion Regulation Among Adolescents With Depression Based on the Principle of Harm Reduction: An Experimental Study

This study aims to explore the role of pain and blood in emotion regulation during nonsuicidal self-injury (NSSI) among adolescents with depression, which included 108 depressed adolescents with NSSI and 110 depressed adolescents without NSSI, to assess the impact of pain and blood on subjective emotional states, and pulse frequency (Pf), respiratory frequency (Rf), galvanic skin response (GSR), and electromyography (EMG). Significant condition×group×time interactions for positive emotions (β = −0.082, SE = 0.026, P = 0.002), Pf (β = −0.045, SE = 0.013, P = 0.001) and GSR (β = −0.041, SE = 0.018, P = 0.027) were found, indicating a significant increase in positive emotions and a significant decrease in Pf and GSR in the NSSI group post-pain/blood stimulus, especially within the first 10 seconds (for Pf, GSR)/3.5 minutes (for positive emotions) following stimulus. And Pf and GSR showed a more pronounced decrease over time in the NSSI group during the pain condition than in the blood condition. These findings highlight the significance of pain and blood in emotion regulation for adolescents with depression who engage in NSSI. Moreover, clinical healthcare professionals may be inspired by the pain and blood stimulus of NSSI based on the harm reduction principle, which provides new ideas for exploring potential interventions that can assist adolescents with depression regulate their emotions and reduce the occurrence of NSSI. And more relevant studies need to be carried out in this area.

On fused filament fabrication of PLA nanofiber reinforced PCL matrix-based smart porous scaffolds

In the past, studies were reported on polycaprolactone (PCL) and polylactic acid (PLA) nanofibers (NF)-based scaffolds for tissue engineering applications. But hitherto, little has been reported on the sensing capability of PLA-NF reinforced PCL composite (PPNC)-based smart porous scaffolds for online health monitoring (OHM) of joint strains/ tendon tears/ contusions/ rhabdomyolysis, etc. In this study, smart porous scaffolds (SPS) were fabricated by fused filament fabrication (FFF) using PPNC for OHM (of joint strains/ tendon tears/ contusions/ rhabdomyolysis, etc.) with tuneable sensing and mechanical properties. The results suggest that FFF parameters, zigzag fill pattern, 0.20 mm layer thickness, and 80 % infill percentage are the best-predicted settings for maximum yield stress (σymax) of SPS. Further, a vector network analyzer was used to ascertain the sensing capability of SPS. The resonance frequency (Rf) for PCL (virgin) and PPNC with minimum yield stress (σymin) and σymax were observed as 2.3021, 2.6008, and 2.4315 GHz respectively. The simulated return loss (S11), specific absorption ratio (SAR), and Rf for PCL (−10.7593 dB, 0.977 W/kg, and 2.6450 GHz), PPNC with σymin (−10.5737 dB, 1.437 W/kg and 2.3400 GHz) and PPNC with σymax (−10.9429 dB, 1.155 W/kg and 2.5050 GHz) indicate that experimental data is in good co-relation with the observed values. The results are supported by a scanning electron microscope and differential scanning calorimetry.

High-angular-momentum Rydberg states in a room-temperature vapor cell for dc electric-field sensing

We prepare and analyze Rydberg states with orbital quantum numbers ℓ≤6 using three-optical-photon electromagnetically induced transparency (EIT) and radio frequency (rf) dressing, and employ the high-ℓ states in electric-field sensing. Rubidium-85 atoms in a room-temperature vapor cell are first promoted into the 25F5/2 state via Rydberg-EIT with three infrared laser beams. Two rf dressing fields then (near-)resonantly couple the 25F, 25H(ℓ=5), and 25I(ℓ=6) Rydberg states. The dependence of the rf-dressed Rydberg-state level structure on rf powers, rf and laser frequencies is characterized using EIT. Furthermore, we discuss the principles of dc-electric-field sensing using high-ℓ Rydberg states and experimentally demonstrate the method using test electric fields of ≲50 V/m induced via photo-illumination of the vapor-cell wall. We measure the highly nonlinear dependence of the dc-electric-field strength on the power of the photo-illumination laser. Numerical calculations, which reproduce our experimental observations well, elucidate the underlying physics. Our paper is relevant to high-precision spectroscopy of high-ℓ Rydberg states, Rydberg-atom-based electric-field sensing, and plasma electric-field diagnostics. Published by the American Physical Society 2024