Magnetic Investigations Research Articles

Differential magnetic probe based on balanced filter with high electric field suppression

AbstractA differential magnetic field probe based on a balanced filter is proposed to improve electric field suppression. The probe comprises a rectangular metal loop for detection and a balanced filter transmission. Three 1/4λ stepped impedance transmission lines are designed between the detective part and balanced filter for impedance matching. The balanced filter can suppress the common mode signals generated by a normal electric field but has little influence on the differential signals detected by a tangential magnetic field thus, the electric field suppression of the magnetic probe can be enhanced. The measurement results show that the working frequency of the proposed magnetic probe ranges from 10 to 20 GHz, and the electric field suppression ratio is over 35 dB from 10 to 15 GHz.

Differential magnetic field probe calibration based on symmetric de‐embedding technology

AbstractThe de‐embedding calibration method has been proposed to achieve high‐precision calibration for a single port electric field or magnetic field probe, which can effectively eliminate the calibration ripple. However, the method's effectiveness for a four‐port calibration system has not been verified yet. In this paper, a four‐port de‐embedding calibration method with a differential magnetic field probe is proposed, and its effectiveness is proved. Two symmetric grounded coplanar waveguide transmission lines are applied in the proposed method to solve the ABCD‐matrix of the embedded part of the calibrator. The de‐embedded S‐parameter model of the four‐port calibration system for differential magnetic field probe can be obtained. The calibration results indicate that the proposed method can also reduce the calibration ripple and compensate for the attenuation caused by the calibrator. Compared with the traditional calibration method using a microstrip line calibrator, the ripples of the proposed method can be reduced by 34%. The analysis results of the frequency interval of the ripple (FIR) in different methods show that the de‐embedding method can reduce the FIRs (except around 1.2 GHz) caused by the reflection of the calibrator and retain the FIR (about 1.2 GHz) caused by the reflection of the probe itself.

Development of correlation ECE system for electron temperature fluctuation measurement in LHD

Correlation-ECE (C-ECE) is a standard method for investigating turbulence driven transport. This method allows electron temperature fluctuations that contain information on turbulent transport and independent thermal noise. The turbulence feature is extracted from a correlation analysis from two close locations. The A C-ECE system is utilized on the large helical device (LHD) to measure emission within the frequency range of 74–79.6 GHz. This system employs the spectral decorrelation method and serves as a collective Thomson scattering diagnostic receiver in the LHD. The C-ECE receiver system is comprised of a filter bank system with 32 band-pass filters and a fast digitizer system operating at a sampling rate of 12.5 GHz in the intermediate frequency (IF) stage. This study presents initial experimental results on temperature fluctuation spectra in the LHD, obtained through the C-ECE system using a coherency-based analysis method. An MHD mode at 5 kHz is excited from the onset of neutral beam injection in a magnetic probe, and coherence spectra are obtained from two C-ECE receiver systems. The temperature fluctuation results are derived from the coherence spectrum after bias removal and indicate a level of approximately 3% in the frequency range of 0 to 400 kHz. Further investigations will be conducted to explore drift wave turbulence activities and reconstruct the radial profile of temperature fluctuation in the LHD using the C-ECE receiver systems.

Coaxial Cable-Based Magnetic and Electric Near-Field Probes to Measure On-Chip Components up to 330 GHz

Coaxial Cable-Based Magnetic and Electric Near-Field Probes to Measure On-Chip Components up to 330 GHz

Total neutron emission from deuteron fusion and plasma pinch compression in a medium-sized plasma focus operating with D2 and D2 + Ne gas mixtures—Experimental results

Newly obtained results on hot and dense deuterium and deuterium-neon plasma compression in a z-pinch electrical discharge configuration are presented. The investigated plasma was generated and compressed using 269 high-current discharges in a medium-sized (dense) plasma focus device. The experimental chamber of the device was filled with deuterium and deuterium-neon gas mixtures under constant total mass/density conditions. Magnetic and electric probes, beryllium neutron activation counter, and high-speed four-frame vacuum ultraviolet/soft x-ray pinhole camera were used to study the plasma dynamics and radiation emission. The results obtained experimentally for the first time confirmed clearly a decrease in the minimum radius of plasma columns with an increase in initial neon fraction. Simultaneously, a decrease in the total neutron emission from deuteron fusion was found. The observed plasma/discharge evolution revealed that the classical description of plasma-focus discharges can be approximately correct up to the moment of maximum compression. Including, existence of quasi-equilibrium plasma compression is probable. It is also possible that the homogeneity of plasma columns during the slow compression phase and maximum compression moment increases with the increase in initial neon fraction. The effect of higher stabilization (repeatability) of discharges was confirmed, for higher initial neon fractions. The dependency of the total neutron emission yield on the parameters describing the full discharge dynamics and the maximum discharge voltage was confirmed. The existence of this type of dependency, for a minimum pinch radius is also possible. In contrast, there was little dependency to the total discharge current parameters measured in the collector area.

Construction and measurement of the prototype side-coupled standing-wave tube for electron Linac

Due to Iran's growing need for accelerators in various applications, NSTRI (Nuclear Science and Technology Research Institute) has defined a 6 MeV e-Linac (electron linear accelerator) project for medical and inspection applications. This electron accelerator has a side-coupled standing wave tube that operates in π/2 mode at the frequency of 2998.5 MHz. This paper presents a summary of the construction and cold test stage of the prototype tube for this accelerator. The prototype tube was constructed from aluminum and clamped with bolts.In the cold test stage, low-power RF measurements werecarried out using a side-coupled cavity tuning method and a bead-pull measurement technique. Using a network analyzer, magnetic and electric probes, and a mechanical structure constructed for this tube made the RF tuning possible. After tuning, the resonant frequency, unloaded quality factor, and effective shunt impedance of the aluminum tube were achieved at 2998.57 MHz, 7970, and 83.25 MΩ/m respectively.

Probe Screening Techniques for Rapid, High-Resolution Core Analysis and Their Potential Usefulness for Energy Transition Applications

Core analysis techniques have traditionally been used mainly for hydrocarbon reservoir applications. However, the same techniques are equally applicable to reservoir issues associated with energy transition, such as geothermal prospects, carbon geosequestration, and hydrogen storage. Traditionally, much core analysis has been performed successfully using core plugs. However, this approach has certain drawbacks: (1) the selected plugs may not necessarily be representative of the full range of lithologies, (2) key features (e.g., thin naturally cemented or fractured zones) may be missed, (3) high-resolution detail at the lamina scale may be missed, (4) depth shifting to well logs may not be sufficiently accurate, and (5) this strategy may be more sensitive to missing core. In this paper, we highlight the usefulness of probe core analysis techniques on slabbed core and powdered samples. For many reservoirs relevant to energy transition, it is crucial to have a high-resolution continuous record of petrophysical properties so that key features are not missed. Probe measurements are less destructive, without the need to cut core plugs, and provide: (1) high-resolution data at the lamina scale so that key features and small-scale heterogeneities can be identified, (2) improved depth matching to well-log data, and (3) rapid, cost-effective data. We describe examples highlighting some different probe techniques. While some techniques are well known, such as probe permeability, others, such as probe acoustics, probe luminance (from linear X-ray measurements), and probe magnetics, are less familiar to core analysts but are well suited for analyzing cores from reservoirs associated with energy transition as well as hydrocarbons. For example, potential geothermal prospects involve studying igneous and metamorphic samples (where the main radiogenic heat sources reside) as well as sedimentary samples, and differences in the magnetic susceptibility signals using a small, portable magnetic probe can quickly differentiate the different rock types. Probe acoustics can be used to (1) rapidly identify anisotropy by orienting the acoustic transmitter-receiver bracket in different directions, (2) identify open microfractures via longer transit times, and (3) produce high-resolution porosity profiles after correlation of transit times with some representative plug or well-log porosity data. Probe luminance and associated linear X-ray images, which are related to density, can indicate small-scale heterogeneities that may impact permeability variation and anisotropy and may not be seen from mere visual observations of the slabbed core surface.

All-in-One Microfluidic Chip for Online Labeling, Separating, and Focusing Rare Circulating Tumor Cells from Blood Samples Followed by Inductively Coupled Plasma Mass Spectrometry Detection.

Circulating tumor cell (CTC) detection is essential for early cancer diagnosis and evaluating treatment efficacy. Despite the growing interest in isolating CTCs and further quantifying surface biomarkers at the single-cell level, highly efficient separation of rare CTCs from massive blood cells is still a big challenge. Here, we developed an all-in-one microfluidic chip system for the immunolabeling, magnetic separation, and focusing of HepG2 cells (as a CTC model) and online combined it with single cell-inductively coupled plasma mass spectrometry (SC-ICP-MS) for quantitative analysis of the asialoglycoprotein receptor (ASGPR) on single HepG2 cells. Lanthanide-labeled anti-ASGPR monoclonal antibody and antiepithelial cell adhesion molecule-modified magnetic beads were prepared as signal and magnetic probes, respectively. Target cells were highly efficiently labeled with signal and magnetic probes in the mixing zone of the microfluidic chip and then focused and sorted in the separation zone by specific magnetic separation techniques to avoid matrix contamination. The average cell recovery of HepG2 cells was derived to be 94.1 ± 5.7% with high separation efficiency and purity. The sorted cells with signal probes were detected for enumeration and quantification of ASGPR on their surface by SC-ICP-MS. The developed method showed good specificity and high sensitivity, detecting an average of (1.0 ± 0.2) × 105 ASGPR molecules per cell surface. This method can be used for absolute quantitative analysis of ASGPR on the surface of single hepatocellular carcinoma cells in real-world samples, providing a highly efficient analytical platform for studying targeted drug delivery in cancer therapy.

High-Resolution Magnetic Imaging Probe With Staggered Sensor Arrays for Small Defects Inspection

High-Resolution Magnetic Imaging Probe With Staggered Sensor Arrays for Small Defects Inspection

A Two-Turn Shielded-Loop Magnetic Near-Field PCB Probe for Frequencies up to 3 GHz.

This paper proposes a novel design of shielded two-turn near-field probe with focus on high sensitivity and high electric field suppression. A comparison of different two-turn loop topologies and their influence on the probe sensitivity in the frequency range up to 3 GHz is presented. Furthermore, a comparison between a single loop probe and a two-turn probe is given and different topologies of the two-turn probe are analyzed and evaluated. The proposed probes were simulated using Ansys HFSS and manufactured on a standard FR4 substrate four-layer printed circuit board (PCB). A measurement setup for determining probe sensitivity and electric field suppression ratio using an in-house made PCB probe stand, vector network analyzer, microstrip line (MSL) and the manufactured probe is presented. It is shown that using a two-turn probe design it is possible to increase the probe sensitivity while minimizing the influence on the probe spatial resolution. The average sensitivity of the proposed two-turn probe compared to the conventional design is increased by 10.1 dB in the frequency range from 10 MHz up to 1 GHz.

Tailored Chemical Reactivity Probes for Systemic Imaging of Aldehydes in Fibroproliferative Diseases.

During fibroproliferation, protein-associated extracellular aldehydes are formed by the oxidation of lysine residues on extracellular matrix proteins to form the aldehyde allysine. Here we report three Mn(II)-based, small-molecule magnetic resonance probes that contain α-effect nucleophiles to target allysine in vivo and report on tissue fibrogenesis. We used a rational design approach to develop turn-on probes with a 4-fold increase in relaxivity upon targeting. The effects of aldehyde condensation rate and hydrolysis kinetics on the performance of the probes to detect tissue fibrogenesis non-invasively in mouse models were evaluated by a systemic aldehyde tracking approach. We showed that, for highly reversible ligations, off-rate was a stronger predictor of in vivo efficiency, enabling histologically validated, three-dimensional characterization of pulmonary fibrogenesis throughout the entire lung. The exclusive renal elimination of these probes allowed for rapid imaging of liver fibrosis. Reducing the hydrolysis rate by forming an oxime bond with allysine enabled delayed phase imaging of kidney fibrogenesis. The imaging efficacy of these probes, coupled with their rapid and complete elimination from the body, makes them strong candidates for clinical translation.

Locked mode detection during error field identification studies

At the beginning of a machine operation, an assessment of the intrinsic error fields, spurious magnetic field perturbations which can affect plasma dynamics, is often carried out by executing the compass scan method [Scoville J.T. et al. Nucl. Fusion 43 250 (2003)]. This method relies on the application of 3D magnetic fields with various phases, induced by EF correction coils, to trigger a locked mode. The instant of locked mode onset allows the identification of the amplitude and phase of the intrinsic error field, from which the empirical correction currents for its minimization can be deduced. The presence of a locked mode needs to be carefully monitored during this study because of the potential disruptive mode behavior, especially in devices which can tolerate a maximum number of disruptions, as in SPARC and in ITER. A novel method, the so-called non-disruptive compass scan method [Paz-Soldan C. et al., Nuclear Fusion 54 (2014) 073013], avoids the disruption risk, as the name recalls, via magnetic island healing, i.e. stabilizing the locked mode. The magnetic island healing is achieved by switching off the error field correction coil current during the execution of the compass scan and asynchronously by increasing the plasma density. The crucial point of this new method is the detection of the locked mode to initiate the EFCC-density control actions. In this work, the locked mode detector adopted during non-disruptive compass scan test at JET is presented, together with brand-new locked mode metrics, which take into account the actual poloidal deformation due to a locked mode and a class of MHD instabilities, named Beta Alfvén Eigenmodes, that appear in the Mirnov signal in concomitance to the locked mode. The use of multiple metrics for locked mode detection during the execution of the non-disruptive compass scan increases the fidelity of the real-time control system to pinpoint the event, compensating possible magnetic probe failure, and initiate the control sequences to heal the magnetic island.

Difunctional Magnetic Nanoparticles Employed in Immunochromatographic Assay for Rapid and Quantitative Detection of Carcinoembryonic Antigen.

Immunochromatographic assay (ICA) plays an important role in in vitro diagnostics because of its simpleness, convenience, fastness, sensitivity, accuracy, and low cost. The employment of magnetic nanoparticles (MNPs), possessing both excellent optical properties and magnetic separation functions, can effectively promote the performances of ICA. In this study, an ICA based on MNPs (MNP-ICA) has been successfully developed for the sensitive detection of carcinoembryonic antigen (CEA). The magnetic probes were prepared by covalently conjugating carboxylated MNPs with the specific monoclonal antibody against CEA, which were not only employed to enrich and extract CEA from serum samples under an external magnetic field but also used as a signal output with its inherent optical property. Under the optimal parameters, the limit of detection (LOD) for qualitative detection with naked eyes was 1.0 ng/mL, and the quantitative detection could be realized with the help of a portable optical reader, indicating that the ratio of optical signal intensity correlated well with CEA concentration ranging from 1.0 ng/mL to 64.0 ng/mL (R2 = 0.9997). Additionally, method comparison demonstrated that the magnetic probes were beneficial for sensitivity improvement due to the matrix effect reduction after magnetic separation, and the MNP-ICA is eight times higher sensitive than ICA based on colloidal gold nanoparticles. The developed MNP-ICA will provide sensitive, convenient, and efficient technical support for biomarkers rapid screening in cancer diagnosis and prognosis.

Structure of Fluctuations in the Edge Plasma of a Stellarator in Modes with Transport Transitions

The evolution of fluctuating signals from electrostatic and magnetic probes and reflectometry on the L-2M stellarator is presented. The L-2M facility is a quasi-stationary toroidal magnetic trap in which plasma is generated and heated by high-power pulsed microwave radiation. Pulses with transitions to improved confinement modes accompanied by an increase in energy, increase in plasma density, and restructuring of the peripheral electric field, were analyzed. Spectral analysis of signals is carried out using Fourier analysis and various wavelets. The possible influence of magnetohydrodynamic and kinetic instabilities on the development of transient processes is considered.

Structure of Fluctuations in the Edge Plasma of a Stellarator in Modes with Transport Transitions

The evolution of fluctuating signals from electrostatic and magnetic probes and reflectometry on the L-2M stellarator is presented. The L-2M facility is a quasi-stationary toroidal magnetic trap in which plasma is generated and heated by high-power pulsed microwave radiation. Pulses with transitions to improved confinement modes accompanied by an increase in energy, increase in plasma density, and restructuring of the peripheral electric field, were analyzed. Spectral analysis of signals is carried out using Fourier analysis and various wavelets. The possible influence of magnetohydrodynamic and kinetic instabilities on the development of transient processes is considered.

Competitive immunoassay using enzyme-regulated Fe3O4@COF/Fe3+ fluorescence probe for natural chloramphenicol detection

Accurate and sensitive detection of chloramphenicol (CAP) in natural samples is essential for ensuring human health. Herein, an enzyme-regulated fluorescence sensor using Fe3O4@COF/Fe3+ probe, is developed for CAP determination. Fe3O4@COF, synthesized via hydrothermal method, exhibits dual functions as a magnetic carrier and signal probe. Bovine serum albumin conjugated-chloramphenicol, adsorbed on the surface of Fe3O4@COF, competes with CAP for antibody binding. The antibody interacts with alkaline phosphatase via the biotin-streptavidin system. Meanwhile, ascorbic acid, produced from the enzyme-catalyzed reaction dominated by alkaline phosphatase, effectively restores the fluorescence of Fe3O4@COF that is quenched by Fe3+. After experimental verification and gradual optimization, a logarithmic linear relationship between CAP concentration and fluorescence intensity is established in the range of 2 × 10−4∼10 μg mL−1, with a good limit of detection (9.2 × 10−5 μg mL−1). Proposed method exhibits excellent stability (15 days) and reusability (8 cycles), providing a sensitive and reliable method for accurate CAP detection. The readouts show good agreement with HPLC and recoveries during laboratory and natural CAP analysis.

Molecular magnetic resonance imaging of liver inflammation using an oxidatively activated probe

Many liver diseases are driven by inflammation, but imaging to non-invasively diagnose and quantify liver inflammation has been underdeveloped. The inflammatory liver microenvironment is aberrantly oxidising owing in part to reactive oxygen species generated by myeloid leucocytes. We hypothesised that magnetic resonance imaging using the oxidatively activated probe Fe-PyC3A will provide a non-invasive biomarker of liver inflammation. A mouse model of drug-induced liver injury was generated through intraperitoneal injection of a hepatoxic dose of acetaminophen. A mouse model of steatohepatitis was generated via a choline-deficient, l-amino acid defined high-fat diet (CDAHFD). Images were acquired dynamically before and after intravenous injection of Fe-PyC3A. The contrast agent gadoterate meglumine was used as a non-oxidatively activated negative control probe in mice fed CDAHFD. The (post-pre) Fe-PyC3A injection change in liver vs. muscle contrast-to-noise ratio (ΔCNR) recorded 2min post-injection was correlated with liver function test values, histologic scoring assigned using the NASH Clinical Research Network criteria, and intrahepatic myeloid leucocyte composition determined by flow cytometry. For mice receiving i.p. injections of acetaminophen, intrahepatic neutrophil composition correlated poorly with liver test values but positively and significantly with ΔCNR (r= 0.64, p <0.0001). For mice fed CDAHFD, ΔCNR generated by Fe-PyC3A in the left lobe was significantly greater in mice meeting histologic criteria strongly associated with a diagnosis NASH compared to mice where histology was consistent with likely non-NASH (p= 0.0001), whereas no differential effect was observed using gadoterate meglumine. In mice fed CDAHFD, ΔCNR did not correlate strongly with fractional composition of any specific myeloid cell subpopulation as determined by flow cytometry. Magnetic resonance imaging using Fe-PyC3A merits further evaluation as a non-invasive biomarker for liver inflammation. Non-invasive tests to diagnose and measure liver inflammation are underdeveloped. Inflammatory cells such as neutrophils release reactive oxygen species which creates an inflammatory liver microenvironment that can drive chemical oxidation. We recently invented a new class of magnetic resonance imaging probe that is made visible to the scanner only after chemical oxidation. Here, we demonstrate how this imaging technology could be applied as a non-invasive biomarker for liver inflammation.

TCCD Fusion Imaging to Estimate Intracranial Pressure and Tissue Displacement with Large Hemispheric Infarction.

Despite breakthroughs in stroke treatment, some patients still experience large infarctions of the cerebral hemispheres resulting in mass effect and tissue displacement. The evolution of mass effect is currently monitored using serial computed tomography (CT) imaging. However, there are patients who are ineligible for transport, and there are limited options for bedside monitoring of unilateral tissue shift. We used fusion imaging for overlaying transcranial color duplex with CT angiography. This method allows overlay of live ultrasound on top of CT or magnetic resonance imaging scans. Patients with large hemispheric infarctions were eligible to participate. Position data from the source files were used and matched with live imaging and correlation to magnetic probes on the patient's forehead and ultrasound probe. Shift of cerebral parenchyma, displacement of the anterior cerebral arteries, basilary artery and third ventricle were analyzed, as well as pressure on the midbrain, and the displacement of the basilar artery on the head were analyzed. Patients received multiple examinations in addition to standard care of treatment with CT imaging. The sensitivity for diagnosing a shift of 3mm with fusion imaging was 100%, with a specificity of 95%. No side effects or interactions with critical care equipment were recorded. Fusion imaging is an easy method to access and acquire measurements for critical care patients and follow-up of tissue and vascular displacement after stroke. Fusion imaging may be a decisive support for indicating hemicraniectomy.

Detection of crack on a mild steel plate by using a magnetic probe incorporating an array of fluxgate sensors

Magnetic flux leakage (MFL) and eddy current testing (ECT) are two of the most commonly used techniques to detect cracks in ferromagnetic materials. The MFL technique excels in determining the locality of a crack, while the ECT technique can provide useful information regarding the dimension and orientation of cracks. The objective of this research is to propose a simultaneous application of both MFL and ECT techniques in a single probe and to improve the visual resolution of the defect by superimposing signals from a sensor array. A magnetic probe was developed with an array of fluxgate sensors and two excitation coils. Line scan measurements and 2D mapping of artificial slits with different depths were conducted on a mild steel SS400 plate with a thickness of 12 mm to evaluate the performance of the developed probe. The line scan measurement results demonstrated the ability of the probe to detect the presence of artificial slits on the sample and to predict the depth of the slits, especially at the 110-Hz excitation frequency. Then, from the 2D mapping results, the location of the slit was determined. Furthermore, by obtaining a superimposed 2D map generated by each sensor, an improved 2D map resolution with lower background noise was obtained.

A pH-responsive magnetic resonance tuning probe for precise imaging of bacterial infection in vivo.

Accurate and sensitive detection of bacteria is essential for treating bacterial infections. Herein, a pH-responsive magnetic resonance tuning (MRET) probe, whose T1-weighted signal is activated in the bacteria-infected acid microenvironment, is developed for in situ accurately magnetic resonance imaging (MRI) of bacterial infection in vivo. The MRET probe (MDVG-1) is an assembly of paramagnetic enhancer (gadolinium-modified i-motif DNA3, abbreviated as Gd-DNA3-Gd) and the precursor of superparamagnetic quencher (DNA and vancomycin-modified magnetic nanoparticle, abbreviated as MDV). The T1-weighted signal of Gd-DNA3-Gd is quenched once the formation of MDVG-1 (MRET ON). Interestingly, the MDVG-1 probe was disassembled into the monomers of Gd-DNA3-Gd and MDV under the bacteria-infected acid microenvironment, resulting significantly enhanced T1-weighted signal at the infected site (MRET OFF). The pH-responsive MRET probe-based enhanced MRI signal and bacteria targeting significantly improve the distinction between bacterial infectious tissues and sterile inflamed tissues, which provides a promising approach for accurately detecting bacterial infection in vivo. STATEMENT OF SIGNIFICANCE: : Detecting pathogenic bacteria in vivo based on magnetic resonance imaging (MRI) strategy has been exploring recently. Although various bacterial-targeted MRI probes have been developed to image bacteria in vivo, the MRI signal of these MRI probes is always "on", which inevitably generates nonspecific background MRI signals, affecting the accuracy of MRI to a certain extent. In the current study, based on the magnetic resonance tuning (MRET) phenomenon, we present a pH-responsive MRET probe (MDVG-1) with T2-weighted imaging to T1-weighted imaging switchable properties to achieve in situ precise imaging of bacterial infection in vivo.