Electromagnetic Trap Research Articles

Internal electromagnetic waves, energy trapping, and energy release in simple time-domain simulations of single particle scattering.

During the decay phase of the interaction of a femto-second Gaussian pulse with a single spherical particle, the presence of quasi-periodic short oscillatory bursts of electromagnetic energy at points in the near field outside the particle have been observed in three-dimensional simulations. Analogous behavior can be very easy produced and understood in simple one-dimensional scattering calculations. In two dimensions the situation immediately becomes more complicated and interesting. Here we discuss results from two-dimensional pseudo-spectral time-domain simulations of scattering from circular, elliptical, and hexagonal particles with the real index of refraction m = 1.3. Our focus is on how energy initially trapped within a particle after interaction with an incident Gaussian pulse is released over time, and we show two kinds of events that can result in “bursts” of energy release from the particles: (i) the coalescence of counter-propagating wave-packet-like electromagnetic field structures that have maximum amplitude near the surface of the particle, and (ii) encounters of individual packets with surface regions of high curvature. The coalescence events in the circular case show the dynamical origin of a two-dimensional form of “photonic nanojet.” The two-dimensional simulations make clear the reason for quasi-periodic intermittent bursts at fixed near-field points outside the particle. Examination of field evolution shows that distinct near-surface internal field maxima, ostensibly the “source” of the emission bursts, are in fact inter-connected by caustic-like internal field structures that extend throughout the particle and have complex time evolution. The revealed intricacy of these connections suggests that understanding the origins of pulsed emissions in three dimensions, even for simple particle geometries, may be quite challenging.

FI-ICP-OES determination of Pb in drinking water after pre-concentration using magnetic nanoparticles coated with ionic liquid

Accurate measurement of trace metals in environmental, biological and medical samples often requires the application of enrichment and/or isolation procedures. Among the many pre-concentration and/or matrix separation techniques available, solid phase extraction procedures (SPE) are most widely employed. In the last years, surface functionalized magnetic-nanoparticles have been introduced, which offer distinct improvements compared to conventional column-based SPE approaches. In the present work, a Flow-Injection (FI) procedure for on-line separation of magnetic nanoparticles from aqueous sample solutions with subsequent ICP-OES analysis is proposed. Silica-coated magnetic cobalt nanoparticles covered with an outer layer of ionic liquid were used as sorbent material. After analyte extraction, the particle suspension was directed through an electro-magnetic trap, thereby the analyte loaded particles were separated from the sample solution. For analysis, the electro-magnet was switched off and the particles were transferred with the carrier solution to the ICP-OES used for element-specific online analysis. Compared to batch-wise methods, the FI-approach offers an additional enrichment step and requires less manual sample manipulation. Applicability of the proposed FI-ICP-OES procedure was demonstrated by the analysis of Pb in the reference material ERM-CA022a and tap-water samples collected from different districts in Vienna, Austria.

Bi-Orbital States in Hyperbolic Traps

We consider a charge in a general electromagnetic trap near a hyperbolic stationary point. The two-dimensional trap Hamiltonian is the sum of a hyperbolic harmonic part and higher order anharmonic corrections. We suppose that two frequencies of the harmonic part are under the resonance 1 : (−1). In this case, anharmonic terms define the dynamics and an effective Hamiltonian on the space of motion constants of the ideal harmonic operator. We show that if the anharmonic part is symmetric, then the effective Hamiltonian has unstable equilibriums and separatrix, which define distinct classically allowed regions in the space of motion constants of the ideal trap. The corresponding stationary states of the trapped charge can form bi-orbital states, i.e., a state localized on two distinct classical trajectories. We obtain semiclassical asymptotics of the energy splitting corresponding to the charge tunneling between these two trajectories in the phase space and express it in terms of complex instantons.

Universal trapping in a three-beam optical lattice

We study electromagnetic trapping in an optical lattice formed by three equiangular in-plane beams. We demonstrate analytically that this optical lattice offers stable trapping sites for particles satisfying specific symmetries, irrespective of the exact nature of their electromagnetic response. Under small displacements, the particles are shown to be subject to equal restoring forces along all directions and the trap is isotropic. Though the intensity distribution of the trap forms a perfect hexagonal lattice, differences in phase variation along opposite directions cause the restoring force to be asymmetric for large displacements, resulting in a force landscape possessing only threefold symmetry. We then show numerically that this asymmetry affects the optical binding force between particles in adjacent trap positions and results in unequal shifts of their equilibrium positions. Universal trapping in the optical lattice combined with this asymmetric mechanical response of trapped particle pairs promises rich optomechanical effects.

Polarization effect in tip-enhanced infrared nanospectroscopy studies of the selective Y5 receptor antagonist Lu AA33810

A novel approach of combining conventional infrared spectroscopy (IR) and atomic force microscopy (AFM) is presented to better understand the behavior of a drug adsorbed on a metal substrate at the nanoscale level. Tip-enhanced infrared nanospectroscopy (TEIRA) was used for the first time to investigate Lu AA33810, a selective brain-penetrating Y5 receptor antagonist, after immobilization on gold nanoparticles (GNPs). Here, a gold coated AFM tip and gold substrate were used to obtain the near-field electromagnetic field trapping effect. Because of the huge signal enhancement, it was possible to obtain the spectral information regarding the self-assembled monolayer of the investigated molecule. The effect of two orthogonal polarizations (p- and s-polarization modulations) of the excitation laser beam on the spectral patterns is also discussed. The results show that there is a strong relationship between the state of polarization of the incident radiation and the relative infrared band intensities. Another factor affecting the observed spectral differences is the topology of the metal substrate, which may result in the induction of a cross-polarization effect. The performed analysis indicates that the C–C bond from the cyclohexyl group is oriented almost parallel to the metal surface. Conversely, the p- and s-polarized spectral variations suggest that the O=S=O angle is high enough to enable the simultaneous interaction of both oxygen atoms with the GNPs.

Electro-suppression of water nano-droplets' solidification in no man's land: Electromagnetic fields' entropic trapping of supercooled water.

Understanding water solidification, especially in "No Man's Land" (NML) (150 K < T < 235 K) is crucially important (e.g., upper-troposphere cloud processes) and challenging. A rather neglected aspect of tropospheric ice-crystallite formation is inevitably present electromagnetic fields' role. Here, we employ non-equilibrium molecular dynamics of aggressively quenched supercooled water nano-droplets in the gas phase under NML conditions, in externally applied electromagnetic (e/m) fields, elucidating significant differences between effects of static and oscillating fields: although static fields induce "electro-freezing," e/m fields exhibit the contrary - solidification inhibition. This anti-freeze action extends not only to crystal-ice formation but also restricts amorphisation, i.e., suppression of low-density amorphous ice which forms otherwise in zero-field NML environments. E/m-field applications maintain water in the deeply supercooled state in an "entropic trap," which is ripe for industrial impacts in cryo-freezing, etc.

Towards the first measurement of matter-antimatter gravitational interaction

The AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is a CERN based experiment with the central aim to measure directly the gravitational acceleration of antihydrogen. Antihydrogen atoms will be produced via charge exchange reactions which will consist of Rydberg-excited positronium atoms sent to cooled antiprotons within an electromagnetic trap. The resulting Rydberg antihydrogen atoms will then be horizontally accelerated by an electric field gradient (Stark effect), they will then pass through a moiré deflectometer. The vertical deflection caused by the Earth's gravitational field will test for the first time the Weak Equivalence Principle for antimatter. Detection will be undertaken via a position sensitive detector. Around 103 antihydrogen atoms are needed for the gravitational measurement to be completed. The present status, current achievements and results will be presented, with special attention toward the laser excitation of positronium (Ps) to the n=3 state and the production of Ps atoms in the transmission geometry.

A mechanism for electromagnetic trapping of extended objects

In this work a mechanism is proposed for levitation and stable confinement of a heavy rotating body using electromagnetic interactions alone, with no position-dependent control. Support of the weight and vertical confinement are achieved through an axisymmetric magnetic field while lateral confinement is accomplished by a rotating octupolar field via the Brouwer saddle mechanism. The orientational degrees of freedom are stabilized through gyroscopic action. The design features multiple variable parameters, thus allowing considerable flexibility for scaling the system size and maximizing the basin of attraction of the stable state.

68 GROWTH AND MARKET QUALITY OF PIGS BORN FROM MAGNETIC NANOPARTICLE-TREATED BOAR SPERMATOZOA

Sperm ejaculates contain a heterogeneous population of nonviable and viable spermatozoal cells. Ejaculates with high concentrations of poor quality or damaged spermatozoa can greatly impair the overall fertility of males. Recently, a novel technique termed nanopurification has been developed (Feugang et al. 2015 IVF Reprod. Med. Genet. 3, 2) to noninvasively target and remove poor quality spermatozoa from boar semen. Such removal will enrich insemination doses with high quality spermatozoa to enhance fertility successes. However, effects associated with offspring born from nanopurified semen and possible meat quality assurance have yet to be extensively studied. The objective of this study was to measure the growth performance and market characteristics of pigs born from standard or nanopurified spermatozoa. Boar semen was obtained in insemination doses from a local stud and was mixed with (nanopurified) magnetic nanoparticles (iron-oxide) specifically designed to interact with acrosome-reacted and apoptotic spermatozoa. After incubation, mixed semen were placed under an electromagnetic field trapping moribund sperm to allow collection of intact and viable spermatozoa. Six gilts were bred with standard non-purified (control; n = 3) or nanopurified (n = 3) semen, with subsequent pregnancies leading to full-term birth of viable offspring. At weaning, pigs of equal sexes (5 male and 5 female) were randomly selected from control (n = 10) and nanopurified (n = 10) litters. Pigs were fed and measured until market weight, at which meat quality and carcass characteristics were assessed. Data (mean ± SEM) were analysed with Student’s t-test and SAS software (SAS Institute Inc., Cary, NC, USA). The threshold of significance was set as P &lt; 0.05. Patterns of growth between groups were comparable up to market size (P &gt; 0.05). Standard pork quality parameters (lean carcass weight, loin eye area, percentage of lean cuts, loin and ham colouring, etc.) revealed no significant differences between groups (P &gt; 0.05). Dressing percentage was found higher in the nanopurified group compared with control, with a 1.5% increase (P &lt; 0.05). Marbling score tended to be significantly higher in the nanopurified group (2.7 ± 0.15) when compared with the control (2.3 ± 0.15). Findings indicate that sperm nanopurification does not impair growth of offspring and could ultimately lead to a higher pork carcass quality. Additional research is being conducted to confirm current findings and identify further effects of nanopurification regarding offspring and carcass quality. This work was supported by USDA-ARS Grant #58–6402–3-018.

Antihydrogen level population evolution: impact of positron plasma length

Antihydrogen is produced by mixing an antiproton and a positron plasma in a cryogenic electromagnetic trap. The dominant antihydrogen formation mechanism is three-body recombination, while the subsequent level population evolution is governed by various processes, mainly collisional (de)excitation, ionisation and radiative decay. In this work the impact of various positron plasma lengths on the level population evolution is investigated. The main interest is the ground-state antihydrogen atom yield. It is found that the ground state level population shows different power-law behaviors at short or longer positron plasma lengths.

Electromagnetic trapping of chiral molecules: orientational effects of the irradiating beam

The photonic interaction generally responsible for the electromagnetic trapping of molecules is forward-Rayleigh scattering, a process that is mediated by transition electric dipoles connecting the ground electronic state and virtual excited states. Higher order electric and magnetic multipole contributions to the scattering amplitude are usually negligible. However, on consideration of chiral discrimination effects (in which an input light of left-handed circular polarization can present different observables compared to right-handed polarization, or molecules of opposite enantiomeric form respond differently to a set circular polarization), the mechanism must be extended to specifically accommodate transition magnetic dipoles. Moreover, it is important to account for the fact that chiral molecules are necessarily nonspherical, so that their interactions with a laser beam will have an orientational dependence. Using quantum electrodynamics, this article quantifies the extent of the energetic discrimination that arises when chiral molecules are optically trapped, placing particular emphasis on the orientational effects of the trapping beam. An in-depth description of the intricate ensemble-weighted method used to incorporate the latter is presented. It is thus shown that, when a mixture of molecular enantiomers is irradiated by a continuous beam of circularly polarized light, a difference arises in the relative rates of migration of each enantiomer in and out of the most intense regions of the beam. As a consequence, optical trapping can be used as a means of achieving enantiomer separation.

Stabilization of Multi-electron Bubbles in Superfluid Helium

Multielectron bubbles (MEBs) in liquid helium were first observed in the late 1970s, but their properties have never been explored experimentally due to their short lifetimes and the difficulty to localize them. We report the observation of long- lived MEBs in a novel cell filled with superfluid helium at static negative pressures. MEBs were extracted from the electron filled vapor sheath of a heated filament loop embedded in the superfluid helium and observed by high-speed photography. MEBs are 2D electron gases on the 3D surface of hollow helium bubbles. Diameters can range from nanometers to millimeters, depending on the number of enclosed electrons. Electrons move in angular momentum states; deformations of the surface are called spherical ripplons. The attractive electron-ripplon interaction leads to an unusual form of superconductivity. If they can be compressed, Wigner crystallization and quantum melting can be observed, as well as a new phase for localization called the ripplo- polaron lattice. MEBs are unstable to tunneling discharge when pressed against a surface. Just as Bose gases are captured in a trap for study, MEBs must also be localized away from walls. We shall discuss methods of capturing them in an electromagnetic trap embedded in the liquid helium.

Positron cooling by vibrational and rotational excitation of molecular gases

Measurements of positron temperature as a function of time are presented when a positron gas, confined in an electromagnetic trap at an elevated temperature ( K), is cooled by interactions with the molecular gases , or CO at 300 K. A simple model describing positron thermalization by coupling to vibrational and rotational modes is presented, with cooling-rate predictions calculated in the Born approximation. Comparisons to the measured positron cooling-rate curves permit estimates of the magnitudes of the relevant cross sections. The results are compared with experiment for the case of vibrational excitation, where direct measurements exist; and they provide estimates of the rotational excitation cross sections where direct measurements are not currently possible. Positron cooling rates are compared for these gases at 300 K, and estimates of their effectiveness in cooling positrons to cryogenic temperatures are discussed.

An efficient biosensor made of an electromagnetic trap and a magneto-resistive sensor

Magneto-resistive biosensors have been found to be useful because of their high sensitivity, low cost, small size, and direct electrical output. They use super-paramagnetic beads to label a biological target and detect it via sensing the stray field. In this paper, we report a new setup for magnetic biosensors, replacing the conventional “sandwich” concept with an electromagnetic trap. We demonstrate the capability of the biosensor in the detection of E. coli. The trap is formed by a current-carrying microwire that attracts the magnetic beads into a sensing space on top of a tunnel magneto-resistive sensor. The sensor signal depends on the number of beads in the sensing space, which depends on the size of the beads. This enables the detection of biological targets, because such targets increase the volume of the beads. Experiments were carried out with a 6µm wide microwire, which attracted the magnetic beads from a distance of 60μm, when a current of 30mA was applied. A sensing space of 30µm in length and 6µm in width was defined by the magnetic sensor. The results showed that individual E. coli bacterium inside the sensing space could be detected using super-paramagnetic beads that are 2.8µm in diameter. The electromagnetic trap setup greatly simplifies the device and reduces the detection process to two steps: (i) mixing the bacteria with magnetic beads and (ii) applying the sample solution to the sensor for measurement, which can be accomplished within about 30min with a sample volume in the µl range. This setup also ensures that the biosensor can be cleaned easily and re-used immediately. The presented setup is readily integrated on chips via standard microfabrication techniques.

Near-field electromagnetic trapping through curl-spin forces

Near-field electromagnetic trapping of particles is generally obtained by means of gradient forces. In this paper, we discuss the attractive behavior of curl-spin forces, as well as their potential for near-field electromagnetic trapping and manipulation. It is demonstrated that curl-spin forces enable the trapping of particles operating at their resonant frequency. Such phenomena can be exploited to design more efficient and selective electromagnetic traps, to boost near-field energy exchange systems, and to bring stability to coupled resonant radiators. It also is illustrated how the balance between the gradient, radiation pressure, and curl-spin force components leads to the formation of zero-force rings around their sources, which explicitly demarcate the trapping regions. Analytical and numerical analyses are presented to assess the stability of the trapping mechanism.

Rainbow trapping using chirped all-dielectric periodic structures

We report a numerical investigation of rainbow trapping (light of different wavelengths) at different spatial locations in a newly designed two-dimensional photonic structure that is formed using chirping parameters in two-dimensional photonic crystals. Chirped parameters ensure trapping of certain light wavelengths inside these structures. To achieve broadband electromagnetic wave trapping, we properly adjust and chirp the position and dielectric filling factor of each unit cell within a photonic crystal structure. The low group velocity regions of the dielectric continuum bands at the Brillouin zone edge enable different wavelengths to be slowed and stopped along the propagation direction. The all-dielectric transparent material nature of the proposed structure realizes light trapping in different electromagnetic regions by spatially varying the effective refractive index of the structure.

Development of a monoenergetic ultraslow antiproton beam source for high-precision investigation

The ASACUSA collaboration developed an ultraslow antiproton beam source, monoenergetic ultraslow antiproton source for high-precision investigation (MUSASHI), consisting of an electromagnetic trap with a liquid He free superconducting solenoid and a low energy antiproton beam transport line. The MUSASHI was capable of trapping and cooling more than $1\ifmmode\times\else\texttimes\fi{}{10}^{7}$ antiprotons and extracting them as an ultraslow antiproton beam with energy of 150--250 eV.

High-Bandwidth Magnetic Tweezers for Applying Torsion to Single DNA Molecules

The mechanical and functional properties of DNA arise from its double helical structure. It is now widely accepted that the torsional properties of DNA and DNA supercoiling play an important role in the kinetics of many DNA-binding proteins, but the mechanism underlying this relationship remains unclear. To address this gap in our understanding, we need an instrument that can accurately measure and control torsional stress applied to DNA. We have developed a high-bandwidth electromagnetic trapping system that can generate a uniform magnetic field in the sample region and apply constant torque above 102 pN·nm on the samples under study. The octupole magnetic trap is integrated into a microscope-based particle tracking system and can rotate superparamagnetic particles with three degrees of rotational freedom. The large signal bandwidth of the current in the coils can reach above 3kHz at 800uH inductive load and the heat generated by the current is dissipated by an active PID-controlled cooling system to prevent heating biological samples. The magnetic trap is being designed to independently control force and torque, allowing us to confine superparamagnetic particles in a trap with low torsional stiffness that is suitable for torque application and measurement at biologically relevant scales. To directly measure the torsional strain in DNA, we are planning to use superparamagnetic beads coated with metal on one hemisphere. Our magnetic torque tweezers are intended to quantitatively measure the changes of torsional stress in DNA and overcome the complexity and heating problems shared by previous optical and magnetic tweezers studies.

When should we change the definition of the second?

The microwave caesium (Cs) atomic clock has formed an enduring basis for the second in the International System of Units (SI) over the last few decades. The advent of laser cooling has underpinned the development of cold Cs fountain clocks, which now achieve frequency uncertainties of approximately 5×10(-16). Since 2000, optical atomic clock research has quickened considerably, and now challenges Cs fountain clock performance. This has been suitably shown by recent results for the aluminium Al(+) quantum logic clock, where a fractional frequency inaccuracy below 10(-17) has been reported. A number of optical clock systems now achieve or exceed the performance of the Cs fountain primary standards used to realize the SI second, raising the issues of whether, how and when to redefine it. Optical clocks comprise frequency-stabilized lasers probing very weak absorptions either in a single cold ion confined in an electromagnetic trap or in an ensemble of cold atoms trapped within an optical lattice. In both cases, different species are under consideration as possible redefinition candidates. In this paper, I consider options for redefinition, contrast the performance of various trapped ion and optical lattice systems, and point to potential limiting environmental factors, such as magnetic, electric and light fields, collisions and gravity, together with the challenge of making remote comparisons of optical frequencies between standards laboratories worldwide.

Oleg Aleksandrovich Lavrentyev

Oleg Aleksandrovich Lavrentyev, regarded as a founding father of Soviet fusion research, died of cardiac arrest on 10 February 2011 in Kharkov, Ukraine.Lavrentyev was born on 7 July 1926 in Pskov, Soviet Union. He became interested in nuclear physics in his youth after reading a book about it, but his quest to learn more was put on hold after the outbreak of World War II. In 1944, with only an eighth-grade education, he crossed the front line and volunteered in the Soviet army as an artilleryman. After the war he continued service in the army as a signalman on Sakhalin Island until July 1950. In the army’s library on the island, Lavrentyev read all the books he could find on math, physics, and chemistry. He learned about the atomic bomb and attempts to create a hydrogen one.Lavrentyev sent a letter to the Kremlin saying, “I know the secret of the hydrogen bomb.” An officer sent by the Kremlin to interrogate Lavrentyev gave him two weeks to put his ideas in writing. In two weeks during July 1950, he secretly wrote the report, in which he confidently declared that a hydrogen bomb could be made with lithium-6 deuteride and initiated by a huge pulse of neutrons from a nuclear fission bomb to create tritium and facilitate deuterium–tritium thermonuclear fusion reactions.In the report, Lavrentyev also advocated developing, for peaceful applications, a nuclear fusion reactor in which spherical electrostatic grids would accelerate and confine plasma. The proposal, made independently before others published their work on the topic, initiated the Soviet program on controlled thermonuclear fusion research. Lavrentyev’s report, which Andrei Sakharov reviewed positively, inspired Sakharov and Igor Tamm to consider using magnetic fields for fusion reactors.Lavrentyev enrolled in Moscow State University in August 1950. During an accelerated program of study, he proposed an “electromagnetic trap” that would confine plasma by electrostatic plugging of magnetic cusps.Several months elapsed before government officials finally contacted Lavrentyev about the report. The nuclear weapons program, overseen by secret police chief Lavrenti Beria, provided him with an apartment and a tutor. But in 1953, before Lavrentyev graduated, Joseph Stalin died, and Beria was executed. People wrongly associated Lavrentyev with Beria, which led to Lavrentyev’s being ostracized and not receiving a promised job at the nuclear weapons development laboratory (now the Kurchatov Institute).In April 1956 Lavrentyev was hired by the Kharkov Physical-Technical Institute (now the Kharkov Institute of Physics and Technology) in Ukraine, where he worked his entire career. In 1966, under the direction of Boris Safronov, he completed his Kandidat dissertation—on electromagnetic traps—at the institute.Lavrentyev built small electromagnetic traps, but he was unable to construct a bigger machine after his supervisor, Anatoly Kalmykov, died and funding was cut. Although he never received adequate financial support, Lavrentyev was still able to pursue his research on a low budget.Lavrentyev developed the theory of plasma confinement and heating in electromagnetic traps; it included the lifetime of ions diffusing in velocity space over the potential barrier and the reduction of the potential barrier by electron space charge in the gaps between the anodes. He analyzed the collisionless heating of ions during electron-beam injection and determined the electron loss rates by diffusion across and along the magnetic field and in velocity space over the electrostatic potential barrier of the cathodes. In his Jupiter 2M experiment, Lavrentyev and his group measured the predicted potential well and demonstrated that electron cross-field diffusional losses were nearly classical.In 2004 Lavrentyev was awarded a doctor of sciences degree by the Kharkov National University for his thesis “Electrostatic and electromagnetic traps of high-temperature plasma.” In his later years, he designed a 4-GW “Elemag” thermonuclear reactor, a powerful neutron source for materials testing. He devised a mechanism to directly convert electron thermal energy into electricity and demonstrated it at low currents. Five students earned their Kandidat degrees under his leadership. He wrote or cowrote more than 100 scientific articles and had 30 inventions. He was named the 2003 Honored Worker in Science and Technology of the Ukraine and was awarded the 2004 K. D. Sinelnikov Prize of the Ukrainian Academy of Sciences for excellence in plasma physics.Lavrentyev will be remembered for his innovative vision, patient persistence, gentle manner, and kindness, and for inspiring the field of nuclear fusion research in the Soviet Union.Oleg Aleksandrovich LavrentyevPPT|High resolution© 2011 American Institute of Physics.