Pole Tip Research Articles

Influence of inhomogeneous magnetic field source location on the intensity of thermomagnetic convection in a closed loop

Purpose. Obtaining information on the influence of the location of the inhomogeneous magnetic field source relative to the heated section of a vertical hydrodynamic loop filled with magnetic fluid on the intensity of convective heat transfer along the loop.Methods. Experiments were carried out using a hydrodynamic loop made of a thin tube of circular cross-section and placed in a vertical plane. Heat source was carried out by a heater on a short vertical section of the loop, and heat removal was implement out by blowing the entire surface of the tube with thermostated air. The source of the magnetic field was the flat pole tips of the ferrite magnetic core, in the gap between which the heater was located. The position of the pole tips relative to the heater varied vertically in the experiments. In the control experiments, the source of the magnetic field was deleted. The circuit was filled with medium concentrated magnetic liquid of the type "magnetite - kerosene - oleic acid". The intensity of steady-state convective heat flow along the tube was calculated from the results of measuring the tube surface temperature by copper-constantane thermocouples. The measurement results were presented in dimensionless form - the relationship between the Nusselt number and Rayleigh number.Results. The unfluctuating mixed, thermomagnetic and gravitational, convection of the magnetic fluid in the loop was observed at any location of the pole tips of the magnetic core relative to the heater. At location of pole tips above the heater, competition of gravitational and thermomagnetic convection was observed, and the heat flux was weak. When the pole tips were placed below the heater, the Nusselt number was 2 - 4 times higher than in the control tests (only gravitational convection) with equal Rayleigh numbers. The highest Nusselt numbers were obtained when the field source was placed in center of the heater.Conclusion. Information on the influence of the relative location of the magnetic field source and the heater on convective heat transfer by magnetic fluid in a hydrodynamic loop is obtained experimentally. The optimal concerning of heat transfer intensity position of the field source was found.

Trade-off between torque ripple and vibration in an IPMSM by examining the temporal and spatial harmonics of flux density

Despite continuous effort to minimize torque ripple, the reduction of vibration has not been yet achieved due to the lack of link between these two performances. The difficulty of investigating the relationship stems from the fact that torque is solely influenced by tangential force whereas vibration is directly tied to radial force. In this paper, the correlation between torque ripple and vibration in an IPMSM (Interior Permanent Magnet Synchronous Motor) is established by examining the air-gap flux density in both radial and tangential directions. Its temporal and spatial harmonics are analyzed. A six-pole nine-slot IPMSM is used as a base configuration, and the air-gap flux density is varied by changing the height of a stator tooth tip. In the previous study, the same approach has been done to observe how to reduce torque ripple effectively. In this study, however, it is found that the trend of torque ripple is not the same as that of vibration with respect to the height of a pole tip, and the relation between the two is thoroughly observed and explained.

Control of the Probe-Sample Interaction Force at the Piconewton Scale by a Magnetic Microprobe in Aqueous Solutions

This article describes the design and implementation of a control system that controls the probe-sample interaction force at the piconewton scale by manipulating a magnetic microprobe in aqueous solutions under a microscope. The control system has two functions, namely accurate force generation by magnetic flux control and precise control of the probe-sample interaction force. Magnetic flux control uses an improved six-input-six-output digital control law along with a disturbance estimator to achieve two control objectives. First, the magnetic flux at each pole tip of a previously developed hexapole electromagnetic actuator can be individually and precisely controlled at frequencies over 4 kHz, and the experimental results precisely followed the theoretical predictions based on the design. Second, together with the optimized flux allocation, the flux control system generates precise magnetic forces, making the six-input hexapole actuator behave like a decoupled three-axis force generator with a bandwidth of more than 4 kHz. Interaction force control compares the measured deformation of the sample with the expected deformation, updated in real time by a deformation predictor, to generate the magnetic force to control the interaction between the probe and the sample. Digital control laws, the estimator, and the predictor are all implemented using a high-speed Field Programmable Gate Array (FPGA) system. Experiments confirm that through mathematical modeling, digital control technology, high-speed electronics, and real-time computation, accurate three-dimensional force generation at the piconewton scale with high bandwidth and precise interaction force control with zero-mean random error, attributed to random thermal force and measurement noise, are achieved.

The choice of the magnetic abrasive action method for processing cutting plates

The existing methods of processing workpieces between two pole tips are described in detail. It is proved that the addition of movements in the process of magnetic abrasive treatment significantly increases the production capabilities, and the plates are obtained with a radius specified by technologists and other geometric parameters. The developed method and device make it possible to process plates on different machines and at different technological parameters. Graphs of the dependence of roughness, material removal and plate radius on processing parameters are described in detail. In conclusion, conclusions are drawn about the viability of the method, as well as the prospects for the development of the magnetic abrasive treatment method. Key words. Operating surfaces, regular microgeometry, material removal per unit area, magnetic abrasive polishing, rounding of the tool cutting edge, two-pole tips

INVESTIGATION OF THE DRAG FORCES FROM THE SIDE OF THE POWDER ENVIRONMENT ON THE PARTS MOVEMENT DURING THE MAGNETO-ABRASIVE FINISHING IN THE ANNULAR BATH

The influence of the technological parameters of the magneto-abrasive finishing (MAF) process on the drag forces to the parts movement of different sizes and shapes, made of ferro- and paramagnetic materials, which act from the side of the ferro-abrasive powder medium formed from various powders in the magneto-abrasive tool (MAT) was investigated. The features of the interaction of the structural elements of the MAT with the surfaces being finished are determined. The influence of the magnetic field strength on the drag forces of the movement of the parts of different sizes and shapes in the MAT was established. It was shown that the process of interaction of MAT with the surfaces of samples being finished with characteristic dimensions up to 12 mm in the annular bath with a width of 35 mm occurs in the "free flow around" mode, while the MAF of samples with characteristic dimensions larger than 12 mm occurs in the "flow around" and "jamming" mode of representative volumes of the MAT between the pole tips and the surface being finished – in the zone of the formed little moving dead zone.
 With the increase in the size of the MAT particles from 200/100 μm to 400/315 μm, the relative value by which the drag forces increase is 1.25–1.65, which is explained by the greater magnetization of larger powders and their formations in the composition of the MAT and, accordingly its greater rigidity.

Design of the Superconducting Magnet System for the New $g-2$/EDM Experiment in the J-PARC

A superconducting solenoid system has been designed for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$g$</tex-math></inline-formula> -2/EDM experiment at the J-PARC, which is used to store muon beam of 0.3 GeV/c. High homogeneous magnetic field is required to be below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 0.1 ppm at 3 T within a muon storage region of 33.3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 1.5 cm in radius and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathbf {\pm }$</tex-math></inline-formula> 5 cm in height around the magnet center. The muon beam is spirally injected to the storage region from the top end of the magnet, therefore the magnetic field distribution is carefully designed in the region where the muon beam pass through. In order to achieve both requirements, NbTi superconducting coils are surrounded by an iron yoke with pole tips, which can optimize the field distribution by adjusting the shape and size. The superconducting coils are cooled by pool boiling in liquid helium, and the evaporated helium gas is re-condensed by GM cryocoolers to keep the liquid helium level for a long time. The main coils are operated in a persistent current mode to remove the magnetic field fluctuation with time caused by a power supply. This paper presents the current design of the magnet system for the experiment at the J-PARC.

Design of Coil-Dominated Quadrupole Triplet for High Rigidity Isotope Beams

Iron-dominated superconducting magnets are one of the most popular and most used design choices for superconducting magnetic quadrupoles for accelerator systems. While the iron yoke and pole tips are economic and effective in shaping the field, the large amount of iron also leads to certain drawbacks, namely, unwanted harmonics from the sextupole correctors nested inside of quadrupole iron pole tips. Additional problems include the cryogenic design challenges of the iron yoke being part of the cold mass, and the mechanical challenges of mounting the sextupole and octupole. The Facility for Rare Isotope Beams (FRIB) plans to implement a coil-dominated cosine-theta type quadrupole as a future upgrade, and the advantages of using an iron-free quadrupole, along with the methods and choices of the design and the approach for the planned fabrication, as well as current status of the project are overviewed in this paper.

Cross-subject variability of the optic radiation anatomy in a cohort of 1065 healthy subjects.

Optic radiations are tracts of particular interest for neurosurgery, especially for temporal lobe resection, because their lesion is responsible for visual field defects. However, histological and MRI studies found a high inter-subject variability of the optic radiation anatomy, especially for their most rostral extent inside the Meyer's temporal loop. We aimed to better assess inter-subject anatomical variability of the optic radiations, in order to help to reduce the risk of postoperative visual field deficiencies. Using an advanced analysis pipeline relying on a whole-brain probabilistic tractography and fiber clustering, we processed the diffusion MRI data of the 1065 subjects of the HCP cohort. After registration in a common space, a cross-subject clustering on the whole cohort was performed to reconstruct the reference optic radiation bundle, from which all optic radiations were segmented on an individual scale. We found a median distance between the rostral tip of the temporal pole and the rostral tip of the optic radiation of 29.2mm (standard deviation: 2.1mm) for the right side and 28.8mm (standard deviation: 2.3mm) for the left side. The difference between both hemispheres was statistically significant (p = 1.10-8). We demonstrated inter-individual variability of the anatomy of the optic radiations on a large-scale study, especially their rostral extension. In order to better guide neurosurgical procedures, we built a MNI-based reference atlas of the optic radiations that can be used for fast optic radiation reconstruction from any individual diffusion MRI tractography.

Design of Two-Phase 4/6 Switched Reluctance Motor for Bidirectional Starting in Washing Machine Application

In this article, design modification of stator poles of conventional two-phase switched reluctance motor is proposed to achieve self-start in both directions of rotation. Stator poles are slanted in a particular direction at the pole tips. This creates a range of rotor positions where torque polarity is the same for both phases, so starting torque is available. A unique excitation scheme is also proposed to run the motor in a particular direction from any initial position. The sequence in which the two phases are excited and the duration of their first excitation decides the direction of continuous rotation. Washing machine is selected as a potential application of the proposed work. Design parameters such as input voltage, rated current, and torque-speed characteristics are investigated to suit top-load washing machines. Simulations are carried out in finite element analysis software. Relation between the slant angle of the stator pole tip and minimum starting torque is analyzed through parametric simulations. Experiments are performed on a prototype two-phase switched reluctance motor. An incremental encoder is used as a position sensor. The initial position is not known, but self-starting in both directions of rotation is achieved with the proposed excitation scheme.

Torque analysis of a permanent magnet synchronous motor using flux densities in air gap

Permanent magnet synchronous motors (PMSMs) having high power density and high efficiency are rigorously researched in various premium applications. Among PMSMs, many studies have been conducted on interior permanent magnet synchronous motors (IPMSMs) to improve torque ripple, but its accurate estimation is not straightforward. Therefore, a six-pole nine-slot (6p/9s) IPMSM is adopted as a base model due to its popularity in academia and industries, and other two pole/slot combinations (8p/12s and 10p/15s) are additionally selected to investigate the influence of a pole/slot combination on torque ripple. Torque performance is easily identified by analyzing tangential force due to their direct proportional relation. In this paper, magnetic flux densities in radial and tangential direction are systematically analyzed since tangential force is determined by the product of the two magnetic flux densities. The modification of a stator pole regarding its tip thickness is chosen as a key parameter in 6p/9s IPMSM. The thickness of a stator pole tip opposite to the direction of spin is more critical in torque ripple improvement. It is verified that the proposed method is sufficient for accurate torque prediction.

(Invited) Electrochemistry: Adventures in Metallization

Microelectronics has benefited enormously from electrochemistry, particularly in metallization. Metallizing through-holes in multilevel printed circuit boards was a major, successful application of electroless Cu (1). Electroless Co-based magnetic films deposited on non-magnetic electroless nickel films on rigid aluminum disks propelled the magnetic storage industry for years.A decade or more ago, it looked as if electroless Co(W)(P) was the ideal candidate to replace PVD Ta-based liners for CMOS back-end-of-line (BEOL) builds (2). Its cost undid it, however, despite meeting selectivity, diffusion barrier and reliability requirements. Electrolytic Cu has been an outstanding success for CMOS BEOL interconnect metallization, mostly because of its submicron feature superfilling ability (3).Following such success, electrolytic and electroless deposition methods have never been far from microelectronics researchers’ interest. In this talk, I will describe examples of electrochemical metallization in chip level, power conversion and MEMS areas that I have worked on. MRAM Final Interconnect Level Capping We recently developed a maskless, electroless, high-P-content, Ni(P) capping process for the final Cu bitline wiring level in our STTM MRAM 200 mm wafer test vehicles. This replaced a two litho mask, final aluminum metal interconnect level, drastically shortening process time.This novel protective layer enables functional testing of MRAM device memory state retention in an air atmosphere at elevated temperatures (4). The Ni(P)-coated wafers show virtually unchanged device resistance and magnetoresistance (MR) for MRAM 4Kb arrays. Magnetic Inductor Fabrication Magnetic inductors are increasing in importance in the ongoing development of integrated, on-chip power conversion. The latter is critical for realizing the dream of granular, DC-DC power delivery using dedicated voltage regulators (VR). Traditionally, the large size of the inductor component has impeded efforts to fabricate the VR in one module.We explored potentially manufacturable processes for magnetic-core inductors with enhanced inductance using through-mask electrodeposited Ni45Fe55 (Fig. 1) (5) and electroless Co(W)(P) layers (6). Electroless Co(W)(P) yoke material performed best overall, showing excellent magnetic properties, good magnetic anisotropy and coercivity of less than 0.1 Oe (6). The resistivity of the Co(W)(P) material was about 90-100 µΩcm; a value of 100 µΩcm is desired to limit yoke eddy current loss at high frequencies.Device scaling has finally brought magnetic inductor fabrication within reach of BEOL CMOS fabs. Magnetic Minimotor Fabrication High-aspect-ratio optical or X-ray lithography (LIGA) and electrodeposition processes were used to fabricate variable-reluctance, nearly planar, integrated minimotors with 6-mm-diameter rotors on silicon wafers (7). The motors comprised six electrodeposited Ni81Fe19 (Permalloy) horseshoe-shaped cores that surrounded the rotor. We formed copper coils around each core. LIGA processing provided vertical wall profiles, which were important for the rotor and stator core pole tips (see stator pole tip, feature D, in Fig. 2).We fabricated the rotors separately and slipped them onto the shaft after releasing them from the substrate wafer. Shaft fabrication via electrodeposition occurred as part of the stator fabrication process.The LIGA fabricated minimotor (100 μm thick Permalloy core with 40 μm thick rotor) represented the successful integration of aligned X-ray exposures and planarizing dielectric into a MEMS fabrication process, producing a working, five-layer magnetic motor. I will show some minimotor operational data.[1]. See papers in IBM J. Res. Develop., 28(6) (1984), available online.[2]. See, e.g., Y. Shacham-Diamand et al., J. Electrochem. Soc., 148 (2001) C162.[3]. P. C. Andricacos et al., IBM J. Res. Develop., 42, 567 (1998).[4]. E. J. O'Sullivan et al., 2019 Meet. Abstr. MA2019-02 916; doi: 10.1149/MA2019-02/15/916.[5]. E. J. O'Sullivan et al., ECS Transactions 50(10):93-105, doi: 10.1149/05010.0093ecst.[6]. N. Wang et al., MMM-Intermag, paper HG-11, 2013.[7]. E. J. O'Sullivan et al., IBM J. of Res. Develop., 42, 681 (1998). Acknowledgements The authors gratefully acknowledge the efforts of the staff of the Microelectronics Research Laboratory (MRL) at the IBM T. J. Watson Research Center, where some of the fabrication work described in this talk was carried out. Figure 1

Positioning of the coil and reduction of the first harmonic of the magnetic field in the superconducting cyclotron using support link forces

A high magnetic field in a superconducting cyclotron is associated with large magnetic forces acting on the magnet coils. These coils are placed in a position using support links that provide stability against the magnetic forces. However, the present configuration of our K500 superconducting cyclotron at VECC, Kolkata does not allow the superconducting coil to be centred with respect to pole tips. This causes field error and beam losses before extraction as observed in our superconducting cyclotron. An analytical model is developed to locate the optimal positioning of the superconducting coils based on support link forces. The present paper describes the methodology for positioning the superconducting coil that produces minimum field error and maintains a safe limit for link forces. Different analyses are presented and compared with experimental data of the superconducting cyclotron at VECC Kolkata.

Electromagnetic Investigation on a Sextupole HTS Magnet for RAON

The rare isotope accelerator complex for online experiments (RAON) is a heavy-ion accelerator equipped with an in-flight fragment separator (IF) system and isotope separation online technique in South Korea. Six quadrupole and a sextupole high-temperature superconducting (HTS) magnets are installed in the hot cell of the IF system, which is a high radiation region, to arrange the ion beams and correct the chromatic aberrations of the ion beams. The magnets are developed and installed for RAON at the Institute for Basic Science (IBS), South Korea. Superconducting magnet systems should be capable of a stable operation against high radiation heating and thermally and electromagnetically robust in the intense radioactive hot cell region. In this paper, we describe the design, fabrication, and evaluation of a sextupole HTS magnet. Electromagnetic designs are conducted considering the position of the HTS magnets and the angle of the yoke pole tip <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> The required design specifications are proposed as a part of RAON of IBS considering the following electromagnetic performance: 1) a magnetic field gradient of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \geq $</tex-math></inline-formula> 3.9 T/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , 2) magnetic field uniformity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ &lt; $</tex-math></inline-formula> 0.5%, 3) effective length of 450 ± 1 mm, and 4) operating temperature of ∼ 45 K.

A portable magnet for radiation biology and dosimetry studies in magnetic fields.

In the current and rapidly evolving era of real-time MRI-guided radiotherapy, our radiation biology and dosimetry knowledge is being tested in a novel way. This paper presents the successful design and implementation of a portable device used to generate strong localized magnetic fields. These are ideally suited for small-scale experiments that mimic the magnetic field environment inside an MRI-linac system, or more broadly MRI-guided particle therapy aswell. A portable permanent magnet-based device employing an adjustable steel yoke and magnetic field focusing cones has been designed, constructed, and tested. The apparatus utilizes two banks of Nd Fe B permanent magnets totaling around 50 kg in mass to generate a strong magnetic field throughout a small volume between two pole tips. The yoke design allows adjustment of the pole tip gap and exchanging of the focusing cones. Further to this, beam portal holes are present in the yoke and focusing cones, allowing for radiation beams of up to 5 5 cm to pass through the region of high magnetic field between the focusing cone tips. Finite element magnetic modeling was performed to design and characterize the performance of the device. Automated physical measurements of the magnetic field components at various locations were measured to confirm the performance. The adjustable pole gap and interchangeable cones allows rapid changing of the experimental set-up to allow different styles of measurements to beperformed. A mostly uniform magnetic field of 1.2 T can be achieved over a volume of at least 3 3 3 cm . This can be reduced in strength to 0.3 T but increased in volume to 10 10 10 cm via removal of the cone tips and/or adjustment of the steel yoke. Although small, these volumes are sufficient to house radiation detectors, cell culture dishes, and various phantom arrangements targeted at examining small radiation field dosimetry inside magnetic field strengths that can be changed with ease. Most important is the ability to align the magnetic field both perpendicular to, or inline with, the radiation beam. To date, the system has been successfully used to conduct published research in the areas of radiation detector performance, lung phantom dosimetry, and how small clinical electron beams behave in these strong magneticfields. A portable, relatively inexpensive, and simple to operate device has successfully been constructed and used for performing radiation oncology studies around the theme of MRI-guided radiotherapy. This can be in either inline and perpendicular magnetic fields of up to 1.2 T with x-ray and particlebeams.

Influence of the pole tips inclination angle during magnetic abrasive polishing on the quality of the drilling rod locking joint threaded surface

Influence of the pole tips inclination angle during magnetic abrasive polishing on the quality of the drilling rod locking joint threaded surface

Focusing Properties of the Magnetic Structure of Isochronous Cyclotrons With Large Spiraling Angle of Pole Tips

Focusing Properties of the Magnetic Structure of Isochronous Cyclotrons With Large Spiraling Angle of Pole Tips

Role of the Histological Variant for the Prognosis and Course of the Focal Segmental Glomerulosclerosis

Abstract The focal segmental glomerulosclerosis is characterized by a morphological heterogeneity, most likely reflecting different pathogenetic mechanisms. The Colombian classification distinguishes five morphological types – non-specific (not otherwise specified or classical), perihilar, cellular, a tubular pole (tip) one and a collapsing one. Eighty-one (81) patients were studied. Their distribution according to the histological variant showed the highest frequency of the non-specific (classical) variant – 70.4%, followed by the perihilar variant – 27.20%, the cellular variant – 1.2% and the collapsing variant – 1.2%. No patients with tip lesions were identified. There were significant differences in the creatinine levels and the glomerular filtration rate (GFR) at the beginning and at the end of the follow-up between patients with the perihilar and the non-specific variants. Patients with the perihilar variant had a better treatment response with a high percentage of patients achieving complete remission – 59.1%. Patients with the non-specific variant had a high chance of treatment failure – 26.3% had no effect from treatment. The results of the study give grounds to assume that the histological variant affects the clinical picture, course and therapeutic response in patients with focal segmental glomerulosclerosis. It could be used as a prognostic marker of disease behavior and guide the clinician in treatment decisions.

Investigation of the process of reactive ion-beam sputtering of gallium arsenide using optical emission spectroscopy

The aim of this work was to study the process of reactive ion-beam sputtering of gallium arsenide using optical emission analysis of plasma in the target region to determine the optimal conditions for the formation of intrinsic GaAs oxides. The ion source was a plasmatron based on an anode layer accelerator (UAS), which generated a stream of accelerated argon and oxygen ions with an energy of 400–1200 eV. The target was made from tellurium doped gallium arsenide. Intense GaI lines (2874.2 Å, 2943.6 Å, 4033.0 Å and 4172.1 Å), atomic argon ArI, argon ions, and also FeI lines were detected in the spectrum upon sputtering of GaAs by Ar+ ions. The appearance of iron lines can be explained by the sputtering of the pole tips of the magnetic system of the ion source. An increase in the accelerating voltage from 1 to 3 kV leads to an increase in the intensity of the peaks of atomic gallium GaI (4172.1 Å) by 2.38 times, the GaI line (4033.0 Å) by 3.25 times, the GaI line (2943.6 Å) 3.4 times, GaI lines (2874.2 Å) 5 times. It was found that an increase in the partial pressure of oxygen leads to a sharp decrease in the peaks of GaI (4033.0 Å) and GaI (4172.1 Å) due to the chemical interaction of gallium and oxygen. Sputtering in pure oxygen reduces the intensity of these peaks by 8 and 5 times, respectively. The intensities of the peaks of atomic gallium GaI (2874.2 Å) and GaI (2943.6 Å) decreased in 2 and 1.78 times, respectively. In the presence of a positive potential on the target, the intensity of all lines of atomic gallium monotonically decreases with increasing potential. In the emission spectrum, lines of atomic oxygen OI (7774.2 Å) and molecular positive ions O+2 (6418.7 Å, 6026.4 Å, 5631.9 Å and 5295.7 Å) were detected. In the presence of a positive potential on the target, a monotonic decrease in the intensity of the above oxygen lines was observed. This indicates an intensification of chemical interaction of oxygen with target elements and, accordingly, a decrease in the free active oxygen particles.

Anatomic Correlates and Surgical Experience with Goel Orbital Cortical Approach to Caudate Head Tumors

We analyzed cortical landmarks, trajectory of approach, and various fiber tracts in the vicinity of our earlier described approach through the orbital/basal surface of the frontal lobe to access tumors located in the region of the caudate nucleus. We also present a new lateral orbital trajectory to approach these tumors. The orbital surfaces of 3 formalin fixed and frozen cadaveric brain specimens were dissected to decipher the white fibers in the region of the caudate nucleus. Safe trajectories to lesions of the head of the caudate nucleus were identified, and the anatomic landmarks of the approach were evaluated. Three patients with caudate head tumors were operated using this approach. The caudate head lies at an average distance of 34 mm from the tip of the frontal pole, 24 mm from the basal medial orbital surface of the frontal lobe, 35 mm from the basal lateral orbital surface, and 37 mm from the superior surface of the frontal lobe. Two avenues were identified to approach the caudate head: one by making a cortical incision in the lateral orbital gyrus (lateral orbital approach), and the second by making a corticectomy in the medial orbital gyrus (medial orbital approach) in line with the temporal pole. All 3 patients were operated successfully using this approach. Surgical approach to the caudate head through the orbital surface of the frontal lobe as described by us provides the shortest trajectory and safe surgical route to access tumors of the caudate nucleus.

An Ion-Optical Circuit of a Small-Sized Mass-Spectrometer for the Isotope Analysis of Hydrogen–Helium Mixtures

We discuss an ion-optical system (IOS) of a mass spectrometer designed for isotopic measurements of light gases, containing a magnetic prism with plane-parallel pole tips and two sector-wise, cylindrical-capacitor identical in geometry, symmetrically located relative to the prism. The relationships between the geometric parameters of the capacitors and the prism are given, which are necessary to ensure achromatic focusing of the ion beam in the plane of the detector receiving slit. We assessed numerically the effect of IOS aberrations on the mass resolution of the IOS and determined the optimal emittance of the ion beam at the source output, which enables achieving a resolution at the level of 3000–3500 with an output slit of the ion source of approximately 50 μm, high transmittance of the mass analyzer, small dimensions of the magnetic prism, and a moderate total length of the central ion trajectory (less than 1 m). The IOS is characterized by a high dispersion in masses, which is much larger than the dispersion of conventional sector magnetic mass spectrometers of the same dimensions. The IOS consists of simple geometry elements, which reduces the costs of its implementation and makes the mass spectrometer technologically advanced and convenient to set up and operate.