Pulsed High Fields Research Articles

Comparing cerebral microembolisation patterns between high power short duration and pulsed field ablation techniques using artificial intelligence based robotic transcranial doppler monitoring

Abstract Thromboembolism is a rare (<1%) complication of atrial fibrillation (AF) ablation , but the incidence of silent ischaemic lesions (SIL) is 5-15% (1). Artificial intelligence (AI)-based robotic transcranial Doppler (r-TCD) enables real-time cerebral embolisation detection. We aimed to investigate the cerebral microembolization signal (MES) load with r-TCD of patients undergoing PF ablation, comparing the number of detected MES-s between 90 W radiofrequency (RFA) "very high power short duration (vHPSD) ablation" and "pulsed field ablation (PFA)" techniques. Our interim analysis included r-TCD registratums of 26 patients. 16 interventions were performed with VHPSD, 10 with PFA, during which we recorded the flow curve of the arteria cerebri media (ACM) bilaterally with r-TCD and analyzed the MES-s quantitatively and qualitatively with AI-based embolisation detection software. Postoperative cranial MRI exams were performed. Continuous variables were compared between the groups using a two-sample t-test, and categorical variables were compared using a Fisher exact test. The MES load by the different pulmonary veins was compared using Wilcoxon test and Bonferroni correction. A p-value below 0,05 was considered significant. The two groups were comparable regarding baseline parameters (mean age: 63 vs.58 p=0,253; EF:59% vs.62 .2% p=0,33). Ablations with vHPSD were significantly longer compared to PFA (88,7 min vs. 54,7 min p<0,001), left atrial time was significantly shorter with PFA (52,1 min vs. 29 min p<0 001), but the fluoroscopic time was significantly longer (5,4 min vs. 9,3 min p=0,009) during ablation with PFA. Neither solid emboli, nor ischaemic lesion or neurological deficit was detected. During the ablations, we saw an average of 246 gas MES-s with PFA and 138 with RFA (p=0,216). During PFA we analyzed the MES load per pulmonary vein: by the left superior vein we detected a median of 56,5 (IQR: 21,5-116,5), by the left inferior there were a median of 23 MES-s (IQR: 4,5 115,5), by the right inferior a median of 32 (IQR: 12-84,5), and by the right superior a median of 22,5(IQR: 8,5-70) respectively, p=0,03. While comparing each veins to each other, by the right vs. left superior vein, the p value resulted 0,01. On an initial sample,we detected known differences in the procedural parameters of the two interventions. There tended to be more MES-s during PFA, but this difference was not significant. Regarding the MES load by the ablation of different pulmonary veins, we found a significant overall difference between the MES load by the four veins, especially between the left and right superior vein. A larger number of interventions and r-TCD registratums is needed to determine the cerebral safety of PFA compared to RFA.

Well balanced pick-up assembly for double pulsed magnetic field apparatus

The generation of high magnetic pulsed fields involves several technological challenges. State-of-the-art field peak intensities can be achieved by means of double-coil systems and, as for other configurations, a special pick-up system is required to clean the signal from spurious components and artifacts. However, the design of a well-balanced pick-up for double-coil systems is not a trivial task because of the different mutual inductance of the two field coils. In general the pick-up can be optimized for one coil only, but not for both. Here we present a new pick-up concept specifically aimed at solving this problem, based on an active compensation bridge and a special compensating coil located outside field-generating coils. Besides yielding a good balance of the signal over all pulse duration, a further advantage is an additional increase in the signal-to-noise ratio.

Investigation on different materials after pulsed high field conditioning and low-energy H- irradiation

During operation, the radio-frequency quadrupole (RFQ) of the LINAC4 at CERN is exposed to high electric fields, which can lead to vacuum breakdown. It is also subject to beam loss, which can cause surface modification, including blistering, which can result in reduced electric field holding and an increased breakdown rate. First, experiments to study the high-voltage conditioning process and electrical breakdown statistics have been conducted using pulsed high-voltage DC systems in order to identify materials with high electric field handling capability and robustness to low-energy irradiation. In this paper, we discuss the results obtained for the different materials tested. To complement these, an investigation of their metallurgical properties using advanced microscopic techniques was done to observe and characterize the different materials and to compare results before and after irradiation and breakdown testing.

Precise parameter control of multicycle terahertz generation in PPLN using flexible pulse trains.

The low (sub %) efficiencies so-far demonstrated for nonlinear optical down-conversion to terahertz (THz) frequencies are a primary limiting factor in the generation of high-energy, high-field THz-radiation pulses (in particular narrowband, multicycle pulses) needed for many scientific fields. However, simulations predict that far higher conversion efficiencies are possible by use of suitably-optimized optical sources. Here we implement a customized optical laser system producing highly-tunable trains of infrared pulses and systematically explore the experimental optimization of the down-conversion process. Our setup, which allows tuning of the energy, duration, number and periodicity of the pulses in the train, provides a unique capability to test predictions of analytic theory and simulation on the parameter dependences for the optical-to-THz difference-frequency generation process as well as to map out, with unprecedented precision, key properties of the nonlinear crystal medium. We discuss the agreements and deviations between simulation and experimental results which, on the one hand, shed light on limitations of the existing theory, and on the other hand, provide the first steps in a recipe for development of practical, high-field, efficiency-optimized THz sources.

Adiabatic approach for heteronuclear SABRE hyperpolarization at high magnetic field

Signal Amplification By Reversible Exchange (SABRE) is a technique aimed at enhancing weak NMR signals of heteronuclei by utilizing the non-equilibrium spin order of parahydrogen. SABRE polarization transfer takes place by means of metalorganic complexes that interact with parahydrogen and the substrate to be polarized in a reversible manner. To achieve substrate hyperpolarization in the high magnetic field of an NMR magnet, radiofrequency (RF) excitation is required. There are two general options for the RF field amplitude: constant or modulated. To date, there has been limited optimization of the adiabatic SABRE conditions. In SABRE, the presence of chemical exchange significantly complicates the spin dynamics involved in polarization transfer and the optimization of adiabatic RF sweeps. We conducted a comprehensive analysis of high-field SABRE pulse sequences with RF sweeps on the heteronuclear channel, specifically 15N. We proposed a simple method for optimizing the amplitude modulation profile of the RF field, which is efficient for systems undergoing chemical exchange. Our approach involved utilizing the dependence of 15N polarization on the amplitude of the constant RF field on the 15N channel. By employing the "optimal" adiabatic RF profile, we achieved a 2.5-fold increase in 15N SABRE-derived polarization at high magnetic field compared to a linear sweep. We theoretically assessed the benefit of RF sweeps over constant RF fields for SABRE at high magnetic field. We demonstrated experimentally that at temperatures −5∘C - +10∘C RF sweeps are more efficient than constant RF field. Maximal increase in 15N polarization achieved was 1.7-fold for bound and 1.4-fold for free substrate. We attribute this increase in polarization to the adiabaticity of the polarization transfer process. This behavior was explained via numerical solution of SABRE master equation for different dissociation rate constants.

Comprehensive analysis of relaxation decays from high-resolution relaxometry

Relaxometry consists in measuring relaxation rates over orders of magnitude of magnetic fields to probe motions of complex systems. High-resolution relaxometry (HRR) experiments can be performed on conventional high-field NMR magnets equipped with a sample shuttle. During the experiment, the sample shuttle transfers the sample between the high-field magnetic center and a chosen position in the stray field for relaxation during a variable delay, thus using the stray field as a variable field. As the relaxation delay occurs outside of the probe, HRR experiments cannot rely on the control of cross-relaxation pathways, which is standard in high-field relaxation pulse sequences. Thus, decay rates are not pure relaxation rates, which may impair a reliable description of the dynamics. Previously, we took into account cross-relaxation effects in the analysis of high-resolution relaxometry data by applying a correction factor to relaxometry decay rates in order to estimate relaxation rates. These correction factors were obtained from the iterative simulation of the relaxation decay while the sample lies outside of the probe and a preceding analysis of relaxation rates which relies on the approximation of a priori multi-exponential decays by mono-exponential functions. However, an analysis protocol matching directly experimental and simulated relaxometry decays should be more self consistent and more generally applicable as it can accommodate deviations from mono-exponential decays. Here, we introduce Matching INtensities for the Optimization of Timescales and Amplitudes of motions Under Relaxometry (MINOTAUR), a framework for the analysis of high-resolution relaxometry that takes as input the intensity decays at all fields. This approach uses the full relaxation matrix to calculate intensity decays, allowing complex relaxation pathways to be taken into account. Therefore, it eliminates the need for a correction of decay rates and for fitting multi-exponential decays with mono-exponential functions. The MINOTAUR software is designed as a flexible framework where relaxation matrices and spectral density functions corresponding to various models of motions can be defined on a case-by-case basis. The agreement with our previous analyses of protein side-chain dynamics from carbon-13 relaxation is excellent, while providing a more robust analysis tool. We expect MINOTAUR to become the tool of choice for the analysis of high-resolution relaxometry.

SYNERGIZING FOOD SAFETY, QUALITY AND GENETIC IMPROVEMENT: THE INTERSECTION OF FOOD MICROBIOLOGY AND PROCESSING

The fusion of food microbiology and processing has given rise, to a field that encompasses food safety, quality and genetic enhancement. This convergence plays a role in ensuring the safety, nutritional value and overall superiority of the food we consume. By integrating knowledge of microbiology with genetic improvement strategies significant progress has been made in preservation methods and food processing techniques. Innovative processing technologies have proven effective in mitigating the presence of microorganisms and extending the shelf life of food products thereby enhancing food safety. Techniques such as high pressure processing pulsed fields and ultraviolet light have gained recognition for their ability to regulate microbial populations and maintain the nutritional integrity of food. This comprehensive approach to food safety combines principles from both microbiology and processing to address challenges and safeguard health. Concurrently strategies in the realm of food microbiology and processing strive to enhance the quality and nutritional value of our meals. Probiotics, which are microorganisms that offer health benefits are employed to promote wellbeing, bolster function and overall vitality. Through engineering probiotics can be customized to target health advantages. The presence of antibiotic microorganisms like Listeria monocytogenes and Salmonella poses a risk, to food safety. To tackle this problem various approaches are utilized, such as enhancement, focused antimicrobial techniques and rigorous compliance, with safety protocols. The utilization of rapid microbiological methods, such as PCR and metagenomics, enables improved monitoring and detection of evolving microorganisms, thereby enhancing food safety. DNA-based techniques are used to combat microbial food fraud, authenticate products, detect adulteration, and trace the origins of ingredients, all of which contribute to consumer trust and the integrity of the food supply chain.

Spatiotemporal modeling of direct acceleration with high-field terahertz pulses.

We present an improved model for electron acceleration in vacuum with high-energy THz pulses that includes spatiotemporal effects. In our calculations, we examined the acceleration with 300 GHz and 3.0 THz central frequency THz pulses with properties corresponding to common sources, and compared the Gaussian and Poisson spectral amplitudes and the associated time profiles of the electric fields. Our calculation takes into account both the longitudinal field and the spatio-spectral evolution around the focus. These aspects of the model are necessary due to the tight focusing and the duration towards a single-cycle of the THz pulses, respectively. The carrier-to-envelope phase (CEP) and the tilting angle of the coincident few- or single-cycle THz pulses must be tuned in all cases in order to optimize the acceleration scheme. We reveal additionally that electron beams with different final energies and different divergences can be generated based on simulated THz pulses having different Porras factors, describing the frequency dependence of the spatiotemporal amplitude profile, which may depend strongly on the method used to generate the single-cycle THz pulses.

High Resolution Ex Vivo Diffusion Tensor Distribution MRI of Neural Tissue

Neural tissue microstructure plays a key role in developmental, physiological and pathophysiological processes. In the continuing quest to characterize it at ever finer length scales, we use a novel diffusion tensor distribution (DTD) paradigm to probe microstructural features much smaller than the nominal MRI voxel size. We first assume the DTD is a normal tensor variate distribution constrained to lie on the manifold of positive definite matrices, characterized by a mean and covariance tensor. We then estimate the DTD using Monte Carlo signal inversion combined with parsimonious model selection framework that exploits a hierarchy of symmetries of mean and covariance tensors. High resolution multiple pulsed field gradient (mPFG) MRI measurements were performed on a homogeneous isotropic diffusion phantom (PDMS) for control, and excised visual cortex and spinal cord of macaque monkey to investigate the capabilities of DTD MRI in revealing neural tissue microstructural features using strong gradients not typically available in clinical MRI scanners. DTD-derived stains and glyphs, which disentangle size, shape, and orientation heterogeneities of microscopic diffusion tensors, are presented for all samples along with the distribution of the mean diffusivity (MD) within each voxel. We also present a new glyph to visualize the symmetric (kurtosis) and asymmetric parts of the fourth-order covariance tensor. An isotropic mean diffusion tensor and zero covariance tensor was found for the isotropic PDMS phantom, as expected, while the covariance tensor (both symmetric and asymmetric parts) for neural tissue was non-zero indicating that the kurtosis tensor may not be sufficient to fully describe the microstructure. Cortical layers were clearly delineated in the higher moments of the MD spectrum consistent with histology, and microscopic anisotropy was detected in both gray and white matter of neural tissue. DTD MRI captures crossing and splaying white matter fibers penetrating into the cortex, and skewed fiber diameter distributions in the white matter tracts within the cortex and spinal cord. DTD MRI was also shown to subsume diffusion tensor imaging (DTI) while providing additional microstructural information about tissue heterogeneity and microscopic anisotropy within each voxel.

Highly efficient generation of narrowband terahertz radiation driven by a two-spectral-line laser in PPLN.

We demonstrate record ∼0.9% efficiencies for optical conversion to narrowband (<1% relative bandwidth) terahertz (THz) radiation by strongly cascaded difference frequency generation. These results are achieved using a novel, to the best of our knowledge, laser source, customized for high efficiencies, with two narrow spectral lines of variable separation and pulse duration (≥250 ps). THz radiation generation in 5% MgO-doped periodically poled lithium niobate (PPLN) crystals of varying poling period was explored at cryogenic and room temperature operation as well as with different crystal lengths. This work addresses an increasing demand for high-field THz radiation pulses which has, up to now, been largely limited by low optical-to-THz radiation conversion efficiencies.

Modulated terahertz generation in femtosecond laser plasma filaments by high-field spintronic terahertz pulses

Strong-field terahertz (THz) light-matter interaction provides various nonlinear control approaches in condensed matter physics, energy and material sciences, electron acceleration, and manipulation. Recently developed spintronic THz emission with minimum complexities has been demonstrated to have the capability for generating high field strengths. Up to now, nonlinear applications based on the spintronic THz transients have yet been realized. Here, we report THz emission from two-color femtosecond laser plasma filaments modulated by a 60-kV/cm THz pulse from W/CoFeB/Pt heterostructures. Enhanced THz radiation based on electron acceleration in plasma is recorded when the direction of the spintronic THz modulating field is in line with that of the electron movement. This behavior is quantitatively reproduced by a local current model of the plasma THz source. Our experimental and theoretical results may inspire further nonlinear THz investigation and accelerate ultrafast THz engineering in matter.

Uniformly scalable lithium niobate THz pulse source in transmission geometry.

A novel THz source, based on optical rectification in LiNbO3 using the tilted-pulse-front technique, is proposed and experimentally demonstrated. The pulse-front tilt is introduced by a volume phase holographic grating, efficiently used at perpendicular incidence in transmission, and the THz pulses are produced in a LiNbO3 plane-parallel nonlinear echelon slab, arranged parallel to the grating. As a unique feature, the entire setup has a plane-parallel, transmission-type configuration, which straightforwardly enables distortion-free scaling to large sizes, high pulse energies and high THz field strengths. The possibility of operating the setup at cryogenic temperature for increased THz generation efficiency is also investigated. Calculations predict efficiencies of 95% for diffraction and 2% for THz generation at room temperature with a refractive-index-matching liquid between the grating and the echelon slab.

High slew rate pulsed electromagnetic field enhances bone consolidation and shortens daily treatment duration in distraction osteogenesis

AimsDistraction osteogenesis (DO) is a useful orthopaedic procedure employed to lengthen and reshape bones by stimulating bone formation through controlled slow stretching force. Despite its promising applications, difficulties are still encountered. Our previous study demonstrated that pulsed electromagnetic field (PEMF) treatment significantly enhances bone mineralization and neovascularization, suggesting its potential application. The current study compared a new, high slew rate (HSR) PEMF signal, with different treatment durations, with the standard Food and Drug Administration (FDA)-approved signal, to determine if HSR PEMF is a better alternative for bone formation augmentation.MethodsThe effects of a HSR PEMF signal with three daily treatment durations (0.5, one, and three hours/day) were investigated in an established rat DO model with comparison of an FDA-approved classic signal (three hrs/day). PEMF treatments were applied to the rats daily for 35 days, starting from the distraction phase until termination. Radiography, micro-CT (μCT), biomechanical tests, and histological examinations were employed to evaluate the quality of bone formation.ResultsAll rats tolerated the treatment well and no obvious adverse effects were found. By comparison, the HSR signal (three hrs/day) treatment group achieved the best healing outcome, in that endochondral ossification and bone consolidation were enhanced. In addition, HSR signal treatment (one one hr/day) had similar effects to treatment using the classic signal (three three hrs/day), indicating that treatment duration could be significantly shortened with the HSR signal.ConclusionHSR signal may significantly enhance bone formation and shorten daily treatment duration in DO, making it a potential candidate for a new clinical protocol for patients undergoing DO treatments.Cite this article: Bone Joint Res 2021;10(12):767–779.

Field-resolved high-order sub-cycle nonlinearities in a terahertz semiconductor laser

The exploitation of ultrafast electron dynamics in quantum cascade lasers (QCLs) holds enormous potential for intense, compact mode-locked terahertz (THz) sources, squeezed THz light, frequency mixers, and comb-based metrology systems. Yet the important sub-cycle dynamics have been notoriously difficult to access in operational THz QCLs. Here, we employ high-field THz pulses to perform the first ultrafast two-dimensional spectroscopy of a free-running THz QCL. Strong incoherent and coherent nonlinearities up to eight-wave mixing are detected below and above the laser threshold. These data not only reveal extremely short gain recovery times of 2 ps at the laser threshold, they also reflect the nonlinear polarization dynamics of the QCL laser transition for the first time, where we quantify the corresponding dephasing times between 0.9 and 1.5 ps with increasing bias currents. A density-matrix approach reproducing the emergence of all nonlinearities and their ultrafast evolution, simultaneously, allows us to map the coherently induced trajectory of the Bloch vector. The observed high-order multi-wave mixing nonlinearities benefit from resonant enhancement in the absence of absorption losses and bear potential for a number of future applications, ranging from efficient intracavity frequency conversion, mode proliferation to passive mode locking.

Rapid fabrication of Cu/40-μm thick full Cu3Sn/Cu joints by applying pulsed high frequency electromagnetic field for high power electronics

With the application of wide bandgap semiconductors for high power electronics, the joints are inevitably faced with a trade-off between withstanding high temperature environments and remaining low bonding temperatures. In this study, a full Cu3Sn intermetallic compounds layer with thickness of 40 μm, which can survive at 679 °C, were obtained between Cu plates using pulsed High Frequency Electromagnetic Field (HFEF) within 10 min at ambient temperature. Output power and frequency of the HFEF was 6 kW and 530 kHz, respectively. In contrast to common Sn-based solder joints, the joints prepared through HFEF consisted predominately of Cu3Sn, because both the horizontal and vertical temperature gradients and the eddy currents within the joints strongly promoted the 3D diffusion of copper atoms. With increasing HFEF exposure time, the Cu3Sn changed from an irregular needle-like to smoothly scalloped or columnar morphology. The HFEF approach enabled Cu3Sn joints to achieve a superior shear strength (>56 MPa) and a greater stand-off height (>30 μm), which are useful to mitigate the coefficient of thermal expansion (CTE) mismatch problems; thereby yielding higher reliability. We envision that these full Cu3Sn joints prove useful in a wide range of applications in high-temperature and high-power electronics.

Electron nuclear interactions in spin-3/2 color centers in silicon carbide: A high-field pulse EPR and ENDOR study

High-frequency pulsed electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) were used to determine electron nuclear interactions on remote ligand shells of silicon and carbon in spin-3/2 color centers with an optically induced high-temperature spin alignment in hexagonal $4H$-, $6H$-, and rhombic $15R$-silicon carbide (SiC) polytypes. The EPR and ENDOR experimental data relate unambiguously to spin-3/2 centers in which the optically induced alignment of the spin-level populations occurs. The identification is based on resolved ligand hyperfine interactions with carbon and silicon nearest, next-nearest, and the more distant neighbors and on the determination of the unpaired electron spin densities. The hyperfine interactions with $^{29}\mathrm{Si}$ and $^{13}\mathrm{C}$ nuclei are unambiguously separated due to the selective population of the fine-structure levels with certain values of ${\mathrm{M}}_{\mathrm{S}}$. The signs of these interactions and, as a result, the signs of oscillating spin density at $^{29}\mathrm{Si}$ and $^{13}\mathrm{C}$ nuclei, are determined. On the basis of the EPR and optically induced ENDOR measurements, signs of the fine-structure splitting for all the centers were demonstrated, which made it possible to establish the character of optically induced spin alignment, including the inverse populations of the spin levels for these centers. The values of hyperfine interaction with $^{29}\mathrm{Si}$ and $^{13}\mathrm{C}$ nuclei, including those remote from the localization of the spin-3/2 center, are tabulated, which can be used by a number of algorithms in quantum information processing as long-term memory.

CoMOF5(pyrazine)(H2O)2 (M = Nb, Ta): Two-Layered Cobalt Oxyfluoride Antiferromagnets with Spin Flop Transitions.

Two cobalt oxyfluoride antiferromagnets CoMOF5(pyz)(H2O)2 (M = Nb 1, Ta 2; pyz = pyrazine) have been synthesized via conventional hydrothermal methods and characterized by thermogravimetric (TGA) analysis, FTIR spectroscopy, electron spin resonance (ESR), magnetic susceptibility, and magnetization measurements at both static low field and pulsed high field. The single-crystal X-ray diffraction indicates both compounds 1 and 2 are isostructural and crystallize in the monoclinic space group C2/m with a two-dimensional Co2+ triangular lattice in the ab plane, separated by the nonmagnetic MOF5 (M = Nb 1, Ta 2) octahedra along the c-axis with large intertriangular-lattice Co···Co distance. Because of low dimensionality together with frustrated triangular lattice, compounds 1 and 2 exhibit no long-range antiferromagnetic order until ∼3.7 K. Moreover, a spin flop transition is observed in the magnetization curves at 2 K for both compounds, which is further confirmed by ESR spectra. In addition, the ESR spectra suggest the presence of a zero-field spin gap in both compounds. The high field magnetization measured at 2 K saturates at ∼7 T with Ms = 1.55 μB for 1 and 1.71 μB for 2, respectively, after subtracting the Van Vleck paramagnetic contribution, which is usually observed for Co2+ ions with pseudospin spin of 1/2 at low temperature. Powder-averaged magnetic anisotropy of g = 3.10 for 1 (3.42 for 2) and magnetic superexchange interaction J/kB = -3.2 K for 1 (-3.6 K for 2) are obtained.

Crystallization behavior, ultrahigh power density and high actual discharge energy density of lead-free borate glass-ceramics containing TiO2

This work presents SrO-BaO-Nb2O5-B2O3-P2O5-K2O-TiO2 glass-ceramics prepared by controlled crystallization method. The uniformly dense microstructure with fine grains can be achieved by introducing TiO2. The structural changes were confirmed by the results of SEM and TEM. The 0.5 mol% TiO2 added glass heated at 750 °C for 2 h demonstrates excellent comprehensive properties of εr= 110, BDS = 1408 kV/cm, high energy storage efficiency (η) of 92% and energy storage density of 9.65 J/cm3. The as-prepared glass-ceramic exhibits ultrahigh power density (86.21 MW/cm3), actual discharge energy density (1.00 J/cm3) and excellent temperature stability. These findings qualify this environment-friendly glass-ceramics as one potential candidate for energy storage applications, especially in high power and pulsed power system field.

High-field THz pulses from a GaAs photoconductive emitter for non-linear THz studies.

We report the emission of high-field terahertz pulses from a GaAs large-area photoconductive emitter pumped with a Ti:Sapphire amplifier laser system at 800 nm wavelength and 1 kHz repetition rate. The maximum estimated terahertz electric field at the focus is ≳230 kV/cm. We also demonstrate the capability of the terahertz field to cause a non-linear effect, which usually requires high-field terahertz pulses generated through optical rectification or an air plasma. A significant drop in the optical conductivity of optically pumped GaAs due to Γ-L inter-valley scattering of free electrons caused by the strong THz field is found.

Effective magnetic Hamiltonian at finite temperatures for rare-earth chalcogenides

Alkali metal rare-earth chalcogenide $ARECh2$ (A=alkali or monovalent metal, RE=rare earth, Ch=O, S, Se, Te), is a large family of quantum spin liquid (QSL) candidates we discovered recently. Unlike $YbMgGaO4$, most members in the family except for the oxide ones, have relatively small crystalline electric-field (CEF) excitation levels, particularly the first ones. This makes the conventional Curie-Weiss analysis at finite temperatures inapplicable and CEF excitations may play an essential role in understanding the low-energy spin physics. Here we considered an effective magnetic Hamiltonian incorporating CEF excitations and spin-spin interactions, to accurately describe thermodynamics in such a system. By taking $NaYbSe2$ as an example, we were able to analyze magnetic susceptibility, magnetization under pulsed high fields and heat capacity in a systematic and comprehensive way. The analysis allows us to produce accurate anisotropic exchange coupling energies and unambiguously determine a crossover temperature ($\sim$25 K in the case of $NaYbSe2$), below which CEF effects fade away and pure spin-spin interactions stand out. We further validated the effective picture by successfully explaining the anomalous temperature dependence of electron spin resonance (ESR) spectral width. The effective scenario in principle can be generalized to other rare-earth spin systems with small CEF excitations.