Particle Confinement Research Articles

Advancing the physics basis for quasi-helically symmetric stellarators

A new optimized quasi-helically symmetric configuration is described that has the desirable properties of improved energetic particle confinement, reduced turbulent transport by three-dimensional shaping and non-resonant divertor capabilities. The configuration presented in this paper is explicitly optimized for quasi-helical symmetry, energetic particle confinement, neoclassical confinement and stability near the axis. Post optimization, the configuration was evaluated for its performance with regard to energetic particle transport, ideal magnetohydrodynamic stability at various values of plasma pressure and ion temperature gradient instability induced turbulent transport. The effects of discrete coils on various confinement figures of merit, including energetic particle confinement, are determined by generating single-filament coils for the configuration. Preliminary divertor analysis shows that coils can be created that do not interfere with expansion of the vessel volume near the regions of outgoing heat flux, thus demonstrating the possibility of operating a non-resonant divertor.

Flexible YIG-poly(vinyl-alcohol) magnetic composite films for microwave applications

Flexible magnetic composite films based on yttrium iron garnet (YIG) and poly(vinyl alcohol) (PVA) with composition xYIG:(1 − x)PVA (0 ≤ x ≤ 0.63 wt) were successfully obtained by facile casting technique. The structure, magnetic, and microwave absorption properties of YIG/PVA films were characterized by XRD, Raman spectroscopy, FTIR, vibrant sample magnetometry (VSM), and ferromagnetic resonance (FMR) techniques. XRD, Raman and FTIR analysis confirmed the complete synthesis of YIG/PVA composites, without any chemical interaction between particles of YIG and PVA matrix. VSM experiments revealed a ferrimagnetic ordering in composite films with small in-plane anisotropy; their specific magnetization increases linearly with the YIG content. YIG/PVA films exhibit an effective imaginary microwave permeability of $$\mu^{\prime\prime}_{\max }$$ ~ 0.1–0.5, as determined by FMR measurements. Numerical simulations of the FMR spectra showed that the large FMR linewidth of $${\Delta H}_{\text{pp}} \sim$$ 80 kA/m is associated with the shape anisotropy and the interactions between YIG particles. A small effective field of $${H}_{\text{eff}}$$ = 20–25 kA/m was originated by the confinement of YIG particles within a PVA matrix into a two-dimensional geometry. The combination of flexibility, magnetic, and microwave properties makes of YIG/PVA films suitable materials for microwave absorption applications.

Plasma Profiles Modifications by Upgraded Power of IBW Heating System in HT-7 Tokamak

The enhancement in local and globalized electron heating has been observed after upgrading of ion Bernstien waves (IBWs) heating system in HT-7 tokamak. The overall capability of injection power has been upgraded from 350 to 600 kW (15–30 MHz) for best and active control of pressure and current density profiles, and to discover the new phenomena of plasma heating for good energy and particle confinement. A new quadruple T-type IBWs coupling antenna has been utilized which has been mounted in the toroidal direction on low field side in the device. The electron heating on both on-axis and off-axis electrons not delete has been observed. Not delete The change in direct electron heating via electron Landau damping (ELD) from IBWs has been investigated, while the bulk electron temperature showed a large rise with a heating factor, ∆(Tene)/Prf, up to 9.3 × 1019 eV m–3 kW–1 with central electron density (ne) 3.7 × 1019 m–3. The particle confinement has also been achieved with IBW injection power of 550 kW at frequency of 27 MHz and with toroidal magnetic field of 1.92 T. The modifications observed in electron temperature and other plasma profiles are discussed under various plasma conditions. The improved energy confinement has also been observed in this scenario.

Alpha particle ripple loss in CFETR steady-state scenario

Confinement of alpha particles is one of the key issues of burning plasma in tokamaks. Due to the discreteness of the toroidal field (TF) coils, the loss alpha particles induced by TF ripple can cause a strong heat load on the first wall. In this work, by using the guiding center code ORBIT, we investigated alpha particle TF ripple loss in Chinese Fusion Engineering Test Reactor (CFETR) steady-state scenario (v20190422), in which both the initial distribution and classical steady-state slowing down distribution of alpha particles are considered. Effects of TF ripple on three particle loss mechanisms, namely prompt loss, ripple well trapping loss and stochastic diffusion loss, are analyzed in detail. Through comparison, it is found that the stochastic diffusion is the main mechanism of alpha particle ripple loss. Moreover, the toroidal and poloidal profiles of the heat load on the first wall are calculated and compared with the safety threshold of CFETR. In addition, a comparison study of alpha particle ripple loss in the hybrid scenario (v20190422) has been carried out. It is found that both total particle loss fraction and maximum heat load in the steady-state scenario are approximately 50% larger than those in the hybrid scenario.

Isotope dependence of energy, momentum and particle confinement in tokamaks

The isotope dependence of plasma transport will have a significant impact on the performance of future D-T experiments in JET and ITER and eventually on the fusion gain and economics of future reactors. In preparation for future D-T operation on JET, dedicated experiments and comprehensive transport analyses were performed in H, D and H-D mixed plasmas. The analysis of the data has demonstrated an unexpectedly strong and favourable dependence of the global confinement of energy, momentum and particles in ELMy H-mode plasmas on the atomic mass of the main ion species, the energy confinement time scaling as ${\tau _E}\sim {A^{0.5}}$ (Maggi et al., Plasma Phys. Control. Fusion, vol. 60, 2018, 014045; JET Team, Nucl. Fusion, vol. 39, 1999, pp. 1227–1244), i.e. opposite to the expectations based only on local gyro-Bohm (GB) scaling, ${\tau _E}\sim {A^{ - 0.5}}$ , and stronger than in the commonly used H-mode scaling for the energy confinement (Saibene et al., Nucl. Fusion, vol. 39, 1999, 1133; ITER Physics Basis, Nucl. Fusion, vol. 39, 1999, 2175). The scaling of momentum transport and particle confinement with isotope mass is very similar to that of energy transport. Nonlinear local GENE gyrokinetic analysis shows that the observed anti-GB heat flux is accounted for if collisions, E × B shear and plasma dilution with low-Z impurities (9Be) are included in the analysis (E and B are, respectively the electric and magnetic fields). For L-mode plasmas a weaker positive isotope scaling ${\tau _E}\sim {A^{0.14}}$ has been found in JET (Maggi et al., Plasma Phys. Control. Fusion, vol. 60, 2018, 014045), similar to ITER97-L scaling (Kaye et al., Nucl. Fusion, vol. 37, 1997, 1303). Flux-driven quasi-linear gyrofluid calculations using JETTO-TGLF in L-mode show that local GB scaling is not followed when stiff transport (as is generally the case for ion temperature gradient modes) is combined with an imposed boundary condition taken from the experiment, in this case predicting no isotope dependence. A dimensionless identity plasma pair in hydrogen and deuterium L-mode plasmas has demonstrated scale invariance, confirming that core transport physics is governed, as expected, by the 4 dimensionless parameters ρ*, ν*, β, q (normalised ion Larmor radius, collisionality, plasma pressure and safety factor) consistently with global quasi-linear gyrokinetic TGLF calculations (Maggi et al., Nucl. Fusion, vol. 59, 2019, 076028). We compare findings in JET with those in different devices and discuss the possible reasons for the different isotope scalings reported from different devices. The diversity of observations suggests that the differences may result not only from differences affecting the core, e.g. heating schemes, but are to a large part due to differences in device-specific edge and wall conditions, pointing to the importance of better understanding and controlling pedestal and edge processes.

Effect of impurity radiation and helium particle confinement on tokamak–reactor plasma performance

In this paper two important matters for assessments the D–T plasma performance of future tokamak–reactors such as ITER and EU–DEMO projects are discussed. The first issue is the heat removal via the radiation of intrinsic and seeded impurities. The second is the helium particle confinement and ash removal. To study these issues, a simple numerical 0.5D-model is proposed. The impurity radiation in the tokamak high–temperature plasma is described by the coronal model. Coronal radiative cooling used rates are based on the tabulated data published in the recent works. Helium particle confinement and ash exhaust efficiency are determined by the variable parameter ρ* characterizing the ratio between the global helium particle confinement time and the energy confinement time τ E . Such approach allows simultaneously obtaining solutions of the particle and energy balance equations in steady–state conditions, taking account of the effect of impurity radiation loss and ash poisoning. Using known energy confinement scaling τ E and design parameters of the ITER and EU–DEMO projects the particle and energy balance equations have been solved. For fixed values of impurities concentration and ratios ρ*, iso–curves of constant fusion power were obtained. These curves are similar to the well–known Plasma OPeration CONtours (POPCON). The POPCON curves are often used to study the operating points of tokamak–reactors. It is shown that for the ITER parameters there is a noticeable margin in the ratio ρ*. For the design parameters of the EU–DEMO project, the margin for ratio ρ* is very small, which casts doubt on the feasibility of the project in its current form (at least with regard to the EU–DEMO steady–state project). Further research in this area is required. The methods and results obtained in this paper can be used for further conceptual analysis of tokamak–reactors operating space.

Summary of the 16th IAEA technical meeting on energetic particles in magnetic confinement systems—theory of plasma instabilities

This report summarizes the contributions presented at the 16th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems—Theory of Plasma Instabilities, held in Shizuoka, Japan, 3–6 September 2019. The meeting brought together about 100 experts from nuclear fusion research sites worldwide to discuss the physics of energetic particles and plasma instabilities, at the first joint meeting from the two scientific disciplines. The main topics of the meeting were: alpha particles physics; transport of energetic particles; effects of energetic particles in magnetic confinement fusion devices; collective phenomena such as Alfvén eigenmodes, energetic particle modes and others; runaway electrons and disruptions; diagnostics for energetic particles; control of energetic particles confinement; multiscale physics and instabilities in burning plasmas.

Highly active and stable Ni dispersed on mesoporous CeO2-Al2O3 catalysts for production of syngas by dry reforming of methane

Ni-based mesoporous mixed CeO2-Al2O3 oxide catalysts prepared by one pot Evaporation Induced Self Assembly (EISA) were tested in dry reforming of methane. The textural, structural and physicochemical properties of the catalysts were studied by N2 adsorption-desorption, TEM-EDS, XRD and elemental analysis. The mobility of oxygen in the structure and the redox properties were investigated by OSCC measurements, TPR and in situ DRIFTS. Finally, the post-reaction samples were analyzed by TGA, RAMAN and TEM. The calcined catalysts prepared by EISA method present mesoporous structures with highly dispersed Ni in the form of NiAl2O4 spinel clusters. After reduction, small size metallic Ni particles are observed (< 5 nm). The presence of Ce in the structure interacting strongly with Al2O3 promotes the oxygen mobility and acts as sites for CO2 adsorption, increasing the activity of the catalyst and promoting the carbon removal mechanism. In absence of Ce in the mesoporous alumina support, the activity for carbon gasification is limited and C filaments accumulate inside the reactor. The same behavior occurs with CeO2-Al2O3 oxide prepared by EISA method when Ni is post-impregnated because of the presence of isolated larger Ni particles which promotes the decomposition of CH4. Therefore, Ni-based CeO2-Al2O3 catalysts prepared by one pot EISA method exhibited high activity and stability for the dry reforming of methane thanks to both properties which are the confinement of Ni particles and the inhibition of carbon deposition.

Topological effects of a spiral dislocation on quantum rings

We consider an elastic medium with a spiral dislocation, and then, we investigate the topological effects of the spiral dislocation on the confinement of a quantum particle to a two-dimensional quantum ring and a one-dimensional quantum ring. We show that the topology of the spiral dislocation modifies the spectra of energy. In particular, we show that the Costa term is modified in the energy levels. Besides, we analyse if the Aharonov–Bohm effect for bound states can exist in these cases.

Application of high frequency biasing and its effect in STOR-M tokamak

A pulsed oscillating power amplifier has been developed to apply high frequency biasing voltage to an electrode at the edge of the STOR-M tokamak plasma. The power amplifier can deliver a peak-to-peak oscillating voltage ±60 V and current 30 A within the frequency range 1 kHz–50 kHz. The electrode is located in the equatorial plane at radius ρ = 0.88. The frequency of the applied voltage has been varied between discharges. It is observed that the plasma density and soft x-ray intensity from the plasma core region usually increase at lower frequency regime 1 kHz–5 kHz as well as relatively higher frequency regime 20 kHz–25 kHz but seldom increase in between them. Increment of τ\\!E has been observed 40% and 20% for the frequency regimes of 1 kHz–5 kHz and 20 kHz–25 kHz, respectively, and τ\\!p increment is 25% for both frequency regimes. Transport simulation has been carried out using the ASTRA simulation code for STOR-M tokamak parameters to understand the physical process behind experimental observations at the higher frequency branch. The model is based on geodesic acoustic mode(GAM) excitement at resonance frequency associated with Ware-pinch due to the oscillating electric field produced by biasing voltage, which can suppress anomalous transport. Simulation results reproduce the experimental trends quite well in terms of the density, particle confinement, as well as energy confinement time evolution. All the results indicate that high frequency biasing is capable of improving confinement efficiently.

Z eff Measurement in Ohmic, L- and H-Mode Plasmas on HL-2A Tokamak

$Z_{\mathrm {eff}}$ is measured by two visible bremsstrahlung diagnostics on HL-2A tokamak, one of which uses a high spectral resolution spectrometer coupled with an electron multiplied CCD (temporal resolution of 100 Hz), and the other uses a filterscope system (temporal resolution of 1 MHz). The bremsstrahlung brightness measured by them coincides with each other very well. $\bar {Z}_{\mathbf {eff}}$ is systematically measured under different discharge conditions, such as divertor and limiter configurations, ohmic and auxiliary heating phases, before and after siliconization, and $L$ – $H$ transition. Under ohmic phase, $\bar {Z}_{\mathbf {eff}}$ is higher in the limiter configuration than that in the divertor configuration by a factor of ~1.5 under high-density regime. $\bar {Z}_{\mathbf {eff}}$ increases in all cases of auxiliary heating scenarios due to enhanced plasma–wall interaction, accompanied by influx increases of low ionization states of impurities such as C2+ and Fe1+ in plasma edge. Siliconization for wall conditioning is prominently effective in lowering the main impurity influxes in plasma edge and thus the impurity level, and a concentration of ~4% for carbon and ~0.2% for iron is roughly evaluated for a typical nonsiliconized plasma. A simple relationship that $Z_{\mathrm {eff}}$ is positively correlated with $\Phi _{\mathrm {in}}$ and $\tau _{\mathrm {p}}$ is verified from the L - and $H$ -mode features, where $\Phi _{\mathrm {in}}$ is the impurity influx and $\tau _{\mathrm {p}}$ the particle confinement time. A nearly constant $\bar {Z}_{\mathbf {eff}}$ evolution is observed during $L$ – $H$ and $H$ – $L$ transition and it seems that $\bar {Z}_{\mathbf {eff}}$ is insensitive to $L$ – $H$ and $H$ – $L$ transition under some $Z_{\mathrm {eff}}$ (0) threshold. The $Z_{\mathrm {eff}}$ profiles are flat/weakly hollow in plasma core region (rho $Z_{\mathrm {eff}}$ (0) and tend to be peaked when $Z_{\mathrm {eff}}$ (0) is larger than 3, which agrees with the neoclassical theory prediction.

Power threshold and confinement of the I-mode in the EAST tokamak

Sixty-five discharges have been confirmed as I-mode discharges after searching the EAST database from 2016 to 2018, and some additional I-mode discharges were obtained in 2019. The I-mode regime features no edge localized modes (ELMs), high energy confinement, and a steep temperature pedestal, while particle confinement remains at L-mode levels. The I-mode regime has been obtained over a small parameter space (BT = 2.4 – 2.7 T, Ip = 0.4 – 0.6 MA, q95 = 4 – 6) using a configuration with drift away from the active X-point. Most of the discharges in EAST are dominated by lower hybrid wave (LHW) heating. In addition, some are heated with both LHW and neutral beam injection (NBI) heating, and a few discharges are heated by NBI and electron cyclotron resonance heating (ECRH). Turbulence suppression in density perturbation has been defined as signaling the onset of the L-I transition. The power threshold of the I-mode is slightly larger than that of the 2008 ITPA scaling law of H-mode. The minimum L-I power threshold varies only weakly with BT, and the power range for the I-mode increases with increasing BT. The I-mode is superior to the L-mode in terms of energy confinement but is still slightly inferior to the H-mode under similar conditions, although the energy confinement time decreases more slowly with increasing heating power than it does in the typical H-mode case. NBI has some benefit for achieving higher confinement. The I-mode is very sensitive to the density near the edge. Under a constant high heating power, a small enhancement in the density will terminate the I-mode, sometimes leading to the I-H transition.

Impact of a charge sheet on neoclassical transport

Perpendicular electron heating in cyclotron waves accumulates resonant particles on the low magnetic field side, where an electron charge sheet may result (Hsu et al 1984 Phys. Rev. Lett. 53 564). Electrostatic fields are produced on both sides of the charge sheet. The impact of a charge sheet on transport is investigated based on neoclassical theory. A full particle simulation is performed using the Boris algorithm. The electrostatic field in the R-direction traps circulating particles or makes trapped particles circulate depending on the field direction. Transport coefficients are rigorously derived for such an electrostatic field. The electrostatic trapping or de-trapping changes the trapped particle population, bootstrap current and thermal conductivity. The positive electrostatic field corresponding to the negative biasing reduces transport, and then a thermal barrier is produced. Therefore, a strong positive electrostatic field can improve confinement. The transport behavior qualitatively agrees with a polarity study of biasing in TEXTOR, where the particle confinement time is three times lower in positive biasing.

Fuel flow and stock during deuterium-deuterium start-up of fusion reactor with advanced plasma model

Flow and stock of fuels in a fusion reactor has been investigated from the aspect of system-dynamics. In particular, operational scenario of the start-up only by deuterium has been discussed with an integrated model of burning plasmas including effects of dilution due to helium ash. The start-up only from deuterium has been attracting interests since initial loading of tritium in a fusion reactor is a critical issue because of limited availability of tritium. The present work solves the flow of tritium in a reactor with advanced modeling of plasma compared to a previous work. The temporal evolution of plasma temperature has been solved in an integrated manner of temperature and density profiles, an empirical scaling of energy confinement time, isotope effect of confinement, slowing down and velocity distribution function of energetic particles, dilution due to helium ash, and radiation losses. Performance of a reactor in terms of fusion power as well as tritium breeding has been assessed.

Burning fraction, radial transport, and steady state profiles of multi-species particles in CFETR burning plasmas

The burning fraction of fuel particles is a crucial issue for future fusion reactors. In order to achieve the high tritium burning fraction required by China Fusion Engineering Test Reactor (CFETR) engineering design, fueling depths and quantities should be estimated by particle control analysis for different scenarios. Thus, in this paper, a multi-species fluid model of deuterium-tritium (D-T) fusion plasmas is applied to study radial transport and profile evolution with CFETR parameters under different fueling conditions. In the model, alpha particles are treated with a slowing down model and diffusion coefficients are introduced according to . Then, in such a self-consistent burning plasma simulation, the results show that the fusion reaction and fueling parameters effect remarkably changes the shape of D/T profiles, while to alphas and helium ash however, the effect of the fueling parameters is much weaker. It is also seen that the burning fraction is increased substantially with the fueling depth, and significantly affected by particle confinement. Furthermore, by substantially raising the D:T ratio to the regime of above unity, the burning fraction can be increased notably, but with a cost of a certain level of fusion power reduction.

On the Core-Shell Nanoparticle in Fractional Dimensional Space

The investigation of core-shell nanoparticles has been greatly exciting in biomedical applications, as this remains of prime importance in targeted drug delivery, sensing, etc. In the present work, the polarizability and scattering features of nanoparticles comprised of nano-sized dielectric/metallic core-shell structures were investigated in the fractional dimensional (FD) space, which essentially relates to the confinement of charged particles. For this purpose, three different kinds of metals—namely aluminum, gold and silver—were considered to form the shell, having a common silicon dioxide (SiO2) nanoparticle as the core. It is noteworthy that the use of noble metal-SiO2 mediums interface remains ideal to realize surface plasmon resonance. The core-shell nanoparticles were considered to have dimensions smaller than the operating wavelength. Under such conditions, the analyses of polarizability and the scattering and absorption cross-sections, and also, the extinction coefficients were taken up under Rayleigh scattering mechanism, emphasizing the effects of a varying FD parameter. Apart from these, the tuning of resonance peaks and the magnitude of surface plasmons due to FD space parameter were also analyzed. It was found that the increase of FD space parameter generally results in blue-shifts in the resonance peaks. Apart from this, the usage of gold and silver shells brings in fairly large shifts in the peak positions of wavelengths, which allows them to be more suitable for a biosensing purpose.

Synthesis of biotin caped Mn2+ activated ZnS quantum dots with their structural stability and modulation of opto-electronic properties

Mn2+ activated ZnS (ZnS:Mn2+) nanoparticles biotin matrix have been synthesized by chemical co-precipitation route. X-ray diffraction (XRD) results confirmed single phase zinc blend structure with crystallite sizes ranging from 1.5 to 1.9 nm. The small particle sizes are believed to have single domain crystallites because of quantum confinement of particles in the biotin matrix. Scanning electron microscopy (SEM) analysis shows smooth and polygon shape potato like morphology having cluster size varying from 77μm to 182μm. Optical measurement shows the band gap of 3.85 eV which has been blue shifted and is accredit to the quantum size effect. The particle size estimated for this gap is to be 2.03 nm and is good agreement with sizes obtained from XRD. The luminescence feature of the as synthesized sample was also reported. The photoluminescence (PL) spectra shows two wide peaks centred at 408 nm and 520 nm respectively. The first emission at 408 nm with short time is attributed to the defects of ZnS while another peak at 520 nm attributed in green emission due to the elemental sulphur species on the surface of zinc sulphide. The both emissions are blue shifted and are attributed to the small particle sizes. The well known manganese related orange-red emission peak cantered at 590 nm has not been observed and is completely quenched that confirmed that the Mn2+ ions have been allocated outside the ZnS crystals. A new emission at 338 nm appears to have radiative transitions from the defect level to the acceptor levels. Thus, by using suitable activator and capping molecule, we are able to stabilize the growth of nanoparticles at room temperature, thereby enhance the structural and opto-electronic properties.

Impact of E × B flow shear stabilization on particle confinement and density peaking at JET

The impact of the flow shear stabilization on particle transport and density peaking at JET is analyzed in the framework of integrated modelling with the CRONOS code. For that purpose, plasmas from a power scan which show a significant increasing of density peaking with the injected neutral beam injection power have been used as a modeling basis. By means of simulations with the quasi-linear model GLF23 for the heat and particle transport, a strong link between the particle confinement and flow shear stabilization is found. This is particularly important close to the pedestal region where the particle pinch direction becomes strongly inward for high flow shear values. Such impact introduces some non-negligible deviation from the well-known collisonality dependence of the density peaking, whose general trend has been also obtained in the framework of this modelling by performing pedestal density scans.

Anomalous losses of energetic particles in the presence of an oscillating radial electric field in fusion plasmas

The confinement of energetic particles in nuclear fusion devices is studied in the presence of an oscillating radial electric field and an axisymmetric magnetic equilibrium. It is shown that, despite the poloidal and toroidal symmetries, initially integrable orbits turn into chaotic regions that can potentially intercept the wall of the tokamak, leading to particle losses. It is observed that the losses exhibit algebraic time decay different from the expected exponential decay characteristic of radial diffusive transport. A dynamical explanation of this behaviour is presented, within the continuous time random walk theory. The central point of the analysis is based on the fact that, contrary to the radial displacement, the poloidal angle is not bounded and a proper statistical analysis can therefore be made, showing for the first time that energetic particle transport can be super-diffusive in the poloidal direction and characterised by asymmetric poloidal displacement. The connection between poloidal and radial positions ensured by the conservation of the toroidal canonical momentum, implies that energetic particles spend statistically more time in the inner region of the tokamak than in the outer one, which explains the observed algebraic decay. This indicates that energetic particles might be efficiently slowed down by the thermal population before leaving the system. Also, the asymmetric transport reveals a new possible mechanism of self-generation of momentum.

A levitated magnetic dipole configuration as a compact charged particle trap.

As a magnetic confinement configuration for electron-positron pair-plasmas, the APEX collaboration [T. S. Pedersen et al., New J. Phys. 14, 035010 (2012)] plans to construct a compact levitated dipole experiment with a high-temperature superconducting coil. In order to realize stable levitation of the dipole field coil, a simple feedback-controlled levitation system was constructed with conventional analog circuits. We report the properties of a prototype levitation system using a permanent magnet and compare its behavior to predictions from a stability analysis. We also present a practical review needed for the construction of a compact levitated dipole trap system based on the work of Morikawa et al. [Teion Kogaku, J. Cryo. Soc. Jpn. 39, 209 (2004)]. Numerical orbit analysis suggests improved confinement properties of charged particles in a dipole field trap by replacing the permanent magnet with a levitated superconducting coil magnet. Such a compact dipole field configuration is potentially applicable to the confinement of various charged particles including positrons and electrons.