Open Trap Research Articles

Control of the Radial Energy Deposition Profile in an Open Magnetic Trap During Electron Cyclotron Plasma Heating

We propose a method for controlling the radial profile of electron cyclotron plasma heating in an axisymmetric magnetic mirror by using minor perturbations of the magnetic field of the mirror. The method is based on the analysis of the ray trajectories behavior near the surface of the electron cyclotron resonance. A way to produce such perturbations by supplementing the system with an additional “quadrupole” pair of magnetic coils is also proposed. The possibility to improve the coupling of radiation with the plasma in an open trap is demonstrated, as well as the possibility to control the energy deposition profile by means of small variations of the current in the additional coils for two basic scenarios of electron cyclotron plasma heating, specifically, longitudinal launching of microwave radiation to the magnetic mirror region and trapping of obliquely launched radiation by the inhomogeneous magnetized-plasma column.

Experiments on the transportation of a magnetized plasma stream in the GOL-3 facility

The program of the deep upgrade of the GOL-3 multiple-mirror trap is presented. The upgrade is aimed at creating a new GOL-NB open trap located at the GOL-3 site and intended to directly demonstrate the efficiency of using multiple-mirror magnetic cells to improve longitudinal plasma confinement in a gasdynamic open trap. The GOL-NB device will consist of a new central trap, adjoint cells with a multiple-mirror magnetic field, and end tanks (magnetic flux expanders). Plasma in the central trap will be heated by neutral beam injection with a power of up to 1.5 MW and duration of 1 ms. At present, physical experiments directed at developing plasma technologies that are novel for this facility are being carried out using the 6-m-long autonomous part of the GOL-3 solenoid. The aim of this work was to develop a method for filling the central trap with a low-temperature start plasma. Transportation of a plasma stream from an arc source over a distance of 3 m in a uniform magnetic field with an induction of 0.5–4.5 T is demonstrated. In these experiments, the axial plasma density was (1–4) × 1020 m–3 and the mirror ratio varied from 5 to 60. In general, the experiments confirmed the correctness of the adopted decisions for the start plasma source of the GOL-NB device.

Experimental investigation of plasma flows in open trap with toroidal diverter under ECR discharge

The results of experimental investigations of plasma flows from an open trap with a toroidal diverter are presented. Cold plasma is generated when introducing microwave power under conditions of electron cyclotron resonance (ECR). The radiation is introduced by a waveguide through a vacuum-tight ceramic window across the axis of the device. By means of the Langmuir probes, the spatial distributions of plasma parameters are measured. The highest density is limited to a critical value nc (~1012 cm–3) for the generator frequency under use. It is found that the temperature and density of the plasma in the trap and in escaping flows are almost independent of the radius when the ECR zone is located near the open-trap confinement region and the density is close to nc. At the density n < nc, ring plasma structures, which collapse under the action of a low-frequency instability, are observed near the separatrix. The possible mechanisms of the occurrence of plasma structures and the nature of the plasma streams are discussed.

Threefold Increase of the Bulk Electron Temperature of Plasma Discharges in a Magnetic Mirror Device.

This Letter describes plasma discharges with a high temperature of bulk electrons in the axially symmetric high-mirror-ratio (R=35) open magnetic system gas dynamic trap (GDT) in the Budker Institute (Novosibirsk). According to Thomson scattering measurements, the on-axis electron temperature averaged over a number of sequential shots is 660±50 eV with the plasma density being 0.7×10^{19} m^{-3}; in few shots, electron temperature exceeds 900 eV. This corresponds to at least a threefold increase with respect to previous experiments both at GDT and at other comparable machines, thus, demonstrating the highest quasistationary (about 1 ms) electron temperature achieved in open traps. The breakthrough is made possible by application of a new 0.7 MW/54.5 GHz electron cyclotron resonance heating system in addition to standard 5 MW heating by neutral beams, and application of a radial electric field to mitigate the flute instability.

Pulse-Periodic Regime of Kinetic Instability of the ECR Discharge Plasma Under the Conditions of Double Plasma Resonance

UDC 533.9.01 We study the stability of a dense nonequilibrium plasma of the electron cyclotron resonance (ECR) discharge in an open magnetic trap immediately after the end of heating. The observed instability is accompanied by pulse-periodic generation of high-power electromagnetic radiation at a frequency that is close to the frequency of the upper hybrid resonance and the double gyrofrequency of electrons and by synchronous precipitations of fast electrons from the trap. It is shown that the observed instability is connected with excitation of plasma waves under the conditions of double plasma resonance in the decaying plasma of the ECR discharge.

Investigation of Magnetic Field Topology in Auto-oscillating Discharge

The magnetic field structure measurements are necessary for understanding of wave propagation in plasma of the auto-oscillating discharge in the open adiabatic trap PR-2. Measurements were made by the developed system for automatic positioning of magnetic probes placed inside the PR-2 vacuum chamber. All magnetic probes were pre-calibrated using Helmholtz coil. Four different circuit configurations were used to excite oscillations in wide frequency range. Observed frequencies of plasma oscillations using magnetic probes correspond to the circuit resonant frequencies.

Simulation of ion behavior in an open three-dimensional Paul trap using a power series method

Simulations of the dynamics of ions trapped in a Paul trap with terms in the potential up to the order 10 have been carried out. The power series method is used to solve numerically the equations of motion of the ions. The stability diagram has been studied and the buffer gas cooling has been implemented by a Monte Carlo method. The dipole excitation was also included. The method has been applied to an existing trap and it has shown good agreement with the experimental results and previous simulations using other methods.

Electron Cyclotron Resonance Near the Axis of a Mirror Trap

Propagation of an extraordinary electromagnetic wave in the vicinity of electron cyclotron resonance surface in an open linear trap is studied analytically, taking into account inhomogeneity of the magnetic field in paraxial approximation. Ray trajectories are derived from a reduced dispersion equation that makes it possible to avoid the difficulty associated with a transition from large propagation angles to the case of strictly longitudinal propagation. As an example, results of general theory are applied to the electron cyclotron resonance heating experiment which is under preparation on the Gas Dynamic Trap in the Budker Institute of Nuclear Physics.

Electron cyclotron resonance near the axis of a quadrupole linear trap

The quasi-longitudinal propagation of an extraordinary electromagnetic wave in the vicinity of the electron cyclotron resonance layer in an open linear trap with a quadrupole magnetic field is studied analytically, taking into account the inhomogeneity of the magnetic field in a paraxial approximation. The ray trajectories are derived from a simplified dispersion equation, that is, nonetheless able to accurately describe the transition from finite to zero perpendicular refractive index. A criterion for an on-axis resonance point to be an attractor for the ray trajectories is formulated, which generalizes a similar criterion for axisymmetric linear traps derived in a recent paper [D. S. Bagulov and I. A. Kotelnikov, Phys. Plasmas 19, 082502 (2012)].

Fusion modes of an axially symmetrical mirror trap with the high power injection of fast particles

We analyzed the energy balance of a fusion system based on an axially symmetrical open trap. In the considered system, the injection of high-energy (fast) particles is the main source of plasma external heating. Simulation of physical kinetics of the injected particles is based on the numerical solution of the Fokker-Planck equation taking into account scattering into the domain of losses and participation in the fusion reactions. Despite the considerable energy losses of the injected particles when leaving the trap due to the angular scattering, the considered system is sufficiently effective to be used as a source of neutrals for the hybrid (fusion-fission) reactor. The principle possibility of achieving a power amplification of Qpl ≈ 1 in plasma was demonstrated in operation modes with high neutron yield.

Electron cyclotron resonance near the axis of the gas-dynamic trap

Propagation of an extraordinary electromagnetic wave in the vicinity of electron cyclotron resonance surface in an open linear trap is studied analytically, taking into account inhomogeneity of the magnetic field in paraxial approximation. Ray trajectories are derived from a reduced dispersion equation that makes it possible to avoid the difficulty associated with a transition from large propagation angles to the case of strictly longitudinal propagation. Our approach is based on the theory, originally developed by Zvonkov and Timofeev [Sov. J. Plasma Phys. 14, 743 (1988)], who used the paraxial approximation for the magnetic field strength, but did not consider the slope of the magnetic field lines, which led to considerable error, as has been recently noted by Gospodchikov and Smolyakova [Plasma Phys. Rep. 37, 768–774 (2011)]. We have found ray trajectories in analytic form and demonstrated that the inhomogeneity of both the magnetic field strength and the field direction can qualitatively change the picture of wave propagation and significantly affect the efficiency of electron cyclotron heating of a plasma in a linear magnetic trap. Analysis of the ray trajectories has revealed a criterion for the resonance point on the axis of the trap to be an attractor for the ray trajectories. It is also shown that a family of ray trajectories can still reach the resonance point on the axis if the latter generally repels the ray trajectories. As an example, results of general theory are applied to the electron cyclotron resonance heating experiment which is under preparation on the gas dynamic trap in the Budker Institute of Nuclear Physics [Shalashov et al., Phys. Plasmas 19, 052503 (2012)].

On the feasibility of electron cyclotron heating of overcritical plasma in a magnetic mirror trap

The feasibility of matching electromagnetic radiation in the electron cyclotron frequency range to a dense plasma in an open magnetic trap by producing an inverted (with a minimum on the axis) plasma density profile is discussed. The use of such a profile shows promise for the implementation of efficient cyclotron heating at plasma densities above the critical density, at which the Langmuir frequency is equal to the heating radiation frequency. Examples of the magnetic field and plasma density distributions in a mirror trap are presented for which analysis of the beam trajectories shows the feasibility of efficient electron cyclotron absorption of microwave beams in overcritical plasma.

Two multidimensional chromatographic methods for enantiomeric analysis of o,p′-DDT and o,p′-DDD in contaminated soil and air in a malaria area of South Africa

In rural parts of South Africa the organochlorine insecticide DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) is still used for malaria vector control where traditional dwellings are sprayed on the inside with small quantities of technical DDT. Since o,p′-DDT may show enantioselective oestrogenicity and biodegradability, it is important to analyse enantiomers of o,p′-DDT and its chiral degradation product, o,p′-DDD, for both health and environmental-forensic considerations. Generally, chiral analysis is performed using heart-cut multidimensional gas chromatography (MDGC) and, more recently, comprehensive two-dimensional gas chromatography (GC×GC). We developed an off-line gas chromatographic fraction collection (heart-cut) procedure for the selective capturing of the appropriate isomers from a first apolar column, followed by reinjection and separation on a second chiral column. Only the o,p′-isomers of DDT and DDD fractions from the first dimension complex chromatogram (achiral apolar GC column separation) were selectively collected onto a polydimethylsiloxane (PDMS) multichannel open tubular silicone rubber trap by simply placing the latter device on the flame tip of an inactivated flame ionisation detector (FID). The multichannel trap containing the o,p′-heart-cuts was then thermally desorbed into a GC with time-of-flight mass spectrometry detection (GC–TOFMS) for second dimension enantioselective separation on a chiral column (β-cyclodextrin-based). By selectively capturing only the o,p′-isomers from the complex sample chromatogram, 1D separation of ultra-trace level enantiomers could be achieved on the second chiral column without matrix interference. Here, we present solventless concentration techniques for extraction of DDT from contaminated soil and air, and report enantiomeric fraction (EF) values of o,p′-DDT and o,p′-DDD obtained by a new multidimensional approach for heart-cut gas chromatographic fraction collection for off-line second dimension enantiomeric separation by 1D GC–TOFMS of selected isomers. This multidimensional method is compared to the complementary technique of comprehensive GC×GC–TOFMS using the same enantioselective column, this time as the first dimension of separation.

Management of Cosmopolites sordidus and Metamasius hemipterus in Banana by Pheromone-Based Mass Trapping

Mass trapping Cosmopolites sordidus (Coleoptera, Curculionidae) using a pheromone-baited pitfall trap and Metamasius hemipterus (Coleoptera, Curculionidae) using a pheromone-sugarcane-baited open gallon trap was conducted in commercial banana. Four traps for each insect per hectare were placed in each of two 5-hectare plots of banana. Two additional 5-hectare plots were designated as controls and treated according to the plantation protocol. Capture rates of C. sordidus and M. hemipterus declined by >75 % over 10-12 months. In the banana growing region studied, corm damage was due primarily to C. sordidus, while only a minor amount of damage was attributable to M. hemipterus. Corm damage reduction in trapping plots was, thus, attributed primarily to C. sordidus trapping. In trapping plots, corm damage decreased by 61-64 % during the experiment. Banana bunch weights increased 23 % relative to control plots after 11-12 months of trapping. Fruit diameter did not vary between bunches harvested from trapping plots vs. control plots. Plant vigor, however, as determined by stem circumference at one meter above ground increased in plots with traps compared to control plots. Trapping for C. sordidus in two plantations of over 200 hectares each, reduced corm damage 62-86 % relative to pre-trapping levels. Insecticide control measures in place when the experiment commenced resulted in about 20-30 % corm damage, while use of pheromone trapping to manage C. sordidus lowered corm damage to 10 % or less. It is estimated that the increase in value of increased yield obtained in this trial (23 %) is about $4,240 USD per year per hectare, while the cost of pheromone trapping is approximately $185 USD per year per hectare. The trapping program becomes revenue neutral if bunch weights increase by an average of 1 % per year of trapping. Approximately 10 % of all plantation area in Costa Rica use the pheromone trapping system described here. The system also is used in Martinique, Guadeloupe, and the Canary Islands.

Hybrid systems in the nuclear fuel cycle. Principles of operation and applications

The problem of utilization of nuclear fuel cycle waste is one of the main problems of modern nuclear energetics. In the Institute of Nuclear Physics of the Siberian Branch of the Russian Academy of Sciences (RAS) in cooperation with the Nuclear Safety Institute of the RAS, a model of a subcritical hybrid system with a plasma neutron driver based on an open gas-dynamic trap is being developed to solve this problem. Modeling of the plasma behavior in the source was carried out using the zero-dimensional GENESYS code, which takes into account the processes of capturing of injected atoms by ions and the processes of Coulombic interactions with warm plasma. This code also contains a module for calculating the linear power of neutron emission along the axis of the trap using the Monte Carlo method. As a template for the fuel blanket, a homogenized blanket of the EFIT system was used. The calculation of neutron-physical characteristics was carried out using a static NMC code which uses a method of direct modeling of neutron trajectories. The article presents the results of optimization of parameters of this system. In particular, the optimal length of the source emission zone was determined and the dependence of the multiplication factor on the thickness of the buffer zone of the subcritical blanket was determined.

Fourier Transform Mass Spectrometry

This article provides an introduction to Fourier transform-based mass spectrometry. The key performance characteristics of Fourier transform-based mass spectrometry, mass accuracy and resolution, are presented in the view of how they impact the interpretation of measurements in proteomic applications. The theory and principles of operation of two types of mass analyzer, Fourier transform ion cyclotron resonance and Orbitrap, are described. Major benefits as well as limitations of Fourier transform-based mass spectrometry technology are discussed in the context of practical sample analysis, and illustrated with examples included as figures in this text and in the accompanying slide set. Comparisons highlighting the performance differences between the two mass analyzers are made where deemed useful in assisting the user with choosing the most appropriate technology for an application. Recent developments of these high-performing mass spectrometers are mentioned to provide a future outlook.

Ultrasensitive characterization of site-specific glycosylation of affinity-purified haptoglobin from lung cancer patient plasma using 10 μm i.d. porous layer open tubular liquid chromatography-linear ion trap collision-induced dissociation/electron transfer dissociation mass spectrometry.

Site-specific analysis of protein glycosylation is important for biochemical and clinical research efforts. Glycopeptide analysis using liquid chromatography-collision-induced dissociation/electron transfer dissociation mass spectrometry (LC-CID/ETD-MS) allows simultaneous characterization of the glycan structure and attached peptide site. However, due to the low ionization efficiency of glycopeptides during electrospray ionization, 200-500 fmol of sample per injection is needed for a single LC-MS run, which makes it challenging for the analysis of limited amounts of glycoprotein purified from biological matrixes. To improve the sensitivity of LC-MS analysis for glycopeptides, an ultranarrow porous layer open tubular (PLOT) LC column (2.5 m × 10 μm i.d.) was coupled to a linear ion trap (LTQ) collision-induced dissociation/electron transfer dissociation mass spectrometer to provide sensitive analysis of N-linked protein glycosylation heterogeneity. The potential of the developed method is demonstrated by the characterization of site-specific glycosylation using haptoglobin (Hpt) as a model protein. To limit the amount of haptoglobin to low picomole amounts of protein, we affinity purified it from 1 μL of pooled lung cancer patient plasma. A total of 26 glycoforms/glycan compositions on three Hpt tryptic glycopeptides were identified and quantified from 10 LC-MS runs with a consumption of 100 fmol of Hpt digest (13 ng of protein, 10 fmol per injection). Included in this analysis was the determination of the glycan occupancy level. At this sample consumption level, the high sensitivity of the PLOT LC-LTQ-CID/ETD-MS system allowed glycopeptide identification and structure determination, along with relative quantitation of glycans presented on the same peptide backbone, even for low abundant glycopeptides at the ∼100 amol level. The PLOT LC-MS system is shown to have sufficient sensitivity to allow characterization of site-specific protein glycosylation from trace levels of glycosylated proteins.

Physical Basis for the Use of Long Pulse Electron Beam in Multi-Mirror Trap

Recent high plasma parameters were reached in experiments on plasma heating in the multi-mirror open trap GOL-3. In these experiments deuterium plasma with density 1014–1016 cm-3 in the 12-m trap with corrugated magnetic field of 4.8T/3.2T was heated by a relativistic electron beam of eU £ 0.8 MeV, I £ 20 kA, j ~ 1–2 kA/cm2, pulse duration ~ 9 ¼s and angular spread £ 0.2 rad. The electron temperature Te ~ 1-4 keV and ion one to Ti ~ 1-2 keV were reached. After the beam pulse the electron temperature of the plasma quickly (~20 ¼s) decreased to ~100 eV. In turn, this leads to an increase in the rate of cooling of ions through the ion-electron collisions, which, together with particle losses determines the energy confinement time of plasma as 0.5-1 ms.To increase the plasma parameters a prolonged heating of the plasma by the electron beam is proposed. The paper considers basic physical phenomena in the beam-plasma interaction and required parameters of the long pulse beam. A choice of long pulse beam parameters is based on the obtained experimental results and scalings. Then estimates of the expected plasma parameters under the influence of the new beam have been done.

PHEROMONE BAITED TRAP FOR THE MANAGEMENT OF RED PALM WEEVIL, Rhynchophorus ferrugineus F. (Coleoptera: Curculionidae) POPULATION IN COCONUT PLANTATIONS

4-methyl-5-nonanol (ferrugineol), the major component of theaggregation pheromone of Rhynchophorus ferrugineus F. was evaluated as alure for trapping of this pest in coconut plantations in Sri Lanka. Trap design,longevity of ferrugineol in field conditions, and the effect of trapping ondamage incidence of R. ferrugineus were studied. N-pentanol, a knowncompound present in coconut stem volatiles was used in combination offerrugineol in all tested traps. Trap designs tested were; an open plasticbucket, a funnel trap, and a modified metal trap. The open plastic bucket (5 L)baited with ferrugineol-pentanol, which was hung on coconut palm stem at 1.5m, caught significantly more number of adult weevils than ferrugineolpentanolbaited funnel and metal traps. An open plastic bucket trap was sixtimes less expensive than the metal trap currently recommended by theCoconut Research Institute, Sri Lanka. Ferrugineol remained effective as abait for 12 weeks under field conditions. High capture rates of adult R.ferrugineus were obtained in ferrugineol baited open bucket traps inplantations where the initial damage incidence was high. Monthly surveys ofindividual palms during pheromone trapping revealed that a sharp reductionof the number of coconut palms damaged by R. ferrugineus in 10-hectareexperimental blocks. Continuous trapping of weevils with ferrugineol over aperiod of time significantly lowered the infestation of this pest.

Mitigating sea turtle by‐catch in coastal passive net fisheries

AbstractThere is growing evidence that small‐scale, coastal, passive net fisheries may be the largest single threat to some sea turtle populations. We review assessments of turtle interactions in these fisheries, and experiments on gear‐technology approaches (modifying gear designs, materials and fishing methods) to mitigate turtle by‐catch, available from a small number of studies and fisheries. Additional assessments are needed to improve the limited understanding of the relative degree of risk coastal net fisheries pose to turtle populations, to prioritize limited conservation resources and identify suitable mitigation opportunities. Whether gear technology provides effective and commercially viable solutions, alone or in combination with other approaches, is not well‐understood. Fishery‐specific assessments and trials are needed, as differences between fisheries, including in gear designs; turtle and target species, sizes and abundance; socioeconomic context; and practicality affect efficacy and suitability of by‐catch mitigation methods. Promising gear‐technology approaches for gillnets and trammel nets include: increasing gear visibility to turtles but not target species, through illumination and line materials; reducing net vertical height; increasing tiedown length or eliminating tiedowns; incorporating shark‐shaped silhouettes; and modifying float characteristics, the number of floats or eliminating floats. Promising gear‐technology approaches for pound nets and other trap gear include: replacing mesh with ropes in the upper portion of leaders; incorporating a turtle releasing device into traps; modifying the shape of the trap roof to direct turtles towards the location of an escapement device; using an open trap; and incorporating a device to prevent sea turtle entrance into traps.