Velocity Filter Research Articles

Determining the contribution of vertical advection to the net ecosystem exchange at Hyytiälä forest, Finland

In nighttime the importance of advection processes to full carbon balance estimated by micrometeorological methods is pronounced. The vertical advection needs the determination of mean vertical velocity which can be obtained from planar fitting, which is the determination of mean local streamline coordinates based on the statistics of the wind field measured over long periods. We tested the utilization of planar-fitting based vertical advection using long-term eddy covariance and CO2 concentration gradient data at SMEAR II field station (Hyytiålå, Southern Finland). The vertical-advection corrected carbon balance, without any friction velocity filtering, agrees very well with those obtained by filtering and gap-filling procedure, and those by chambers and ecosystem model. Although no direct measurements for horizontal advection is available, the results indicate minor significance of horizontal advection in the studied cases.

α decay of the new isotopesRn193,194

The new neutron-deficient isotopes Rn-193,Rn-194 have been identified in the complete fusion reaction Cr-52+Sm-144 -> Rn-196(*) at the velocity filter SHIP. The alpha-decay energy and half-life value of Rn-194 were determined to be E-alpha=7700(10) keV and T-1/2=0.78(16) ms, respectively. For Rn-193 the half-life of T-1/2=1.15(27) ms and two alpha lines at E-alpha 1=7685(15) keV, I-alpha 1=74(20)% and E-alpha 2=7875(20) keV, I-alpha 2=26(12)% were found. The decay pattern of Rn-193, which is substantially different from that of the heavier odd-A Rn isotopes, provides first experimental evidence for the long-predicted deformation in the very neutron-deficient Rn nuclei.

Studies of 213g, mRa and 214g, mRa by α and γ decay

The decay of 213, 214Ra was studied by α-γ and γ-γ coincidence measurements. The nuclei were produced in the reactions 170Er(48Ca, xn)218-x Ra and 170Er(50Ti, 3n)217Th and subsequent α decay of 217Th to 213Ra. Evaporation residues recoiling out of the target were separated in-flight by the velocity filter SHIP and implanted into a position-sensitive 16-strip PIPS detector in order to study their subsequent decays. Associated γ-rays were detected by a four-fold Ge-Clover detector. In the present work we extracted new and improved data for 213, 214Ra including isomeric transitions. The results are discussed and compared with previously published data.

Effects of nonlinearity on the structure of PSBL beamlets

We investigate the nonlinear influence of the cross‐tail currents carried by beamlets (substructures of PSBL ion beams) on the topology of the magnetic field, and, correspondingly, on the dispersion properties of these substructures self‐consistently generated in this field. We found that some of the peculiarities of beamlet shapes found recently in CLUSTER data could be explained by taking into account the nonlinearity of the system. This model explains the steepening of local beamlets dispersion in comparison with the global dispersion of the enveloping VDIS structure. At the same time we found that velocity filter effects operating during beamlets propagation toward the Earth prevent the sign's reversal of this local dispersion.

Multiple attenuation using eigenvalue decomposition

Multiple reflections constitute one of the most troublesome forms of coherent noise in seismic exploration, especially in marine surveys. There are many approaches to attenuating or suppressing multiples, but none can remove all multiple reflections under all conditions. We have eveloped two new methods to attenuate multiple reflections using the Karhunen-Loeve transform which extract coherent information from multichannel input data in a least-squares sense. They supplement conventional methods. The first is the ‘localized multiple attenuation' method. Its aim is to attenuate a single (typically water bottom) multiple reflection in deep water or multisource marine acquisition. It is similar to velocity filter methods but is not as prone to spatial aliasing and edge effects. The criterion of local coherency gives the method the flexibility to discriminate between primary and multiple reflections. The second is the ‘targeted multiple attenuation' method. It uses the similarity between a primary reflection and its multiple in both the spatial and time directions. Its aim is to remove a particular multiple reflection associated with a specified primary rather than all the multiple energy for an entire trace. The method can be applied pre- or post-stack, and to 2D or 3D data. Keywords : multiple, reflection, suppression, eigenvector, eigenvalue Global Journal of Pure and Applied Sciences Vol. 12(2) 2006: 225-227

α-decay of the new isotopePo187: Probing prolate structures beyond the neutron mid-shell at N = 104

The new neutron-deficient isotope $^{187}\mathrm{Po}$ has been identified in the complete fusion reaction $^{46}\mathrm{Ti}$+$^{144}\mathrm{Sm}$\ensuremath{\rightarrow}$^{187}\mathrm{Po}$+$3n$ at the velocity filter SHIP. Striking features of the $^{187}\mathrm{Po}$ \ensuremath{\alpha} decay are the strongly-hindered decay to the spherical ground state and unhindered decay to a surprisingly low-lying deformed excited state at 286 keV in the daughter nucleus $^{183}\mathrm{Pb}$. Based on the potential energy surface calculations, the $^{187}\mathrm{Po}$ ground state and the 286 keV excited state in $^{183}\mathrm{Pb}$ were interpreted as being of prolate origin. The systematic deviation of the \ensuremath{\alpha}-decay properties in the lightest odd-A Po isotopes relative to the smooth behavior in the even-A neighbors is discussed. Improved data for the decay of ${}^{187}{\mathrm{Bi}}^{m,g}$ were also obtained.

α-decay spectroscopy of the new isotopeAt192

Decay properties of the new neutron-deficient nuclide $^{192}\mathrm{At}$ have been studied in the complete fusion reaction $^{144}\mathrm{Sm}$($^{51}\mathrm{V}$,3n)$^{192}\mathrm{At}$ at the velocity filter SHIP. Two isomeric states with half-lives of 88(6) ms and 11.5(6) ms, respectively, and with complex $\ensuremath{\alpha}$-decay schemes were identified in $^{192}\mathrm{At}$. The decay pattern of one of the isomers suggests that it is based on the oblate-deformed $\ensuremath{\pi}2{f}_{7/2}\ensuremath{\bigotimes}\ensuremath{\nu}1{i}_{13/2}$ configuration, which confirms the expected onset of deformation in the At isotopes by approaching the neutron midshell at $N=104$.

Effects of polyline simplification of dynamic GPS data under forest canopy on area and perimeter estimations

The objectives of this study were to determine Global Positioning System (GPS) positional errors while moving under the forest canopy and to clarify the effects of polyline simplification on area and perimeter estimations. We used the Pathfinder Pro XR and GPSMAP 76S, which are categorized as “high-end mapping” and “general navigation” GPS receivers, respectively. The field tests were conducted in both natural and plantation forests. The results showed that the Pathfinder Pro XR, which has better multipath rejection technology, worked well, especially in the plantation forest under unfavorable conditions of higher stand density. We used analysis of variance to clarify the effects of the receiver type, positioning mode, stand type, and polyline simplification method on area and perimeter estimations. The receiver type and positioning mode were found to be significant factors that affected area estimation. The Pathfinder Pro XR estimated the area more accurately than the GPSMAP 76S, and differential GPS estimated the area more accurately than autonomous GPS. With respect to the perimeter, the receiver type, positioning mode, and polyline simplification method were found to be significant factors. The results showed that perimeter estimation was improved by using the velocity filter, and further improved by using the velocity filter and Douglas-Peucker algorithm, especially when the Pathfinder Pro XR was used. The GPSMAP 76S estimated the perimeter accurately without any filtering because its default speed filter worked well, even though the GPSMAP 76S is a general navigation GPS receiver.

Continuous Loading of an Electrostatic Trap for Polar Molecules

A continuously operated electrostatic trap for polar molecules is demonstrated. The trap has a volume of approximately 0.6 cm3 and holds molecules with a positive Stark shift. With deuterated ammonia from a quadrupole velocity filter, a trap density of approximately 10(8) cm(-3) is achieved with an average lifetime of 130 ms and a motional temperature of approximately 300 mK. The trap offers good starting conditions for high-precision measurements, and can be used as a first stage in cooling schemes for molecules and as a "reaction vessel" in cold chemistry.

Super-Gaussian mirror for high-field-seeking molecules

A matter wave mirror using a single, pulsed, super-Gaussian (SG) optical beam for specular reflection of neutral ground-state molecules is studied. The mirror has a high reflectivity close to 100% and nearly perfect specular reflection over a large incident angle. This mirror avoids the usual problems due to surface roughness and the van der Waals interactions that occur in conventional atomic mirrors. Further, it is capable of reflectance and transmittance with applications to velocity filtering and deceleration of cold molecules.

Decay studies of 215-217Th using ER- γ- α- γ coincidences

The decay of 215-217Th was investigated by ER-γ-α-γ coincidence measurements. The nuclei were produced by the reaction 170Er(50Ti, xn)220-xTh. Evaporation residues recoiling out of the target were separated in flight by the velocity filter SHIP and stopped in a position-sensitive 16-strip PIPS-detector in order to study their subsequent decays. Associated γ-rays were detected by a fourfold Ge-Clover detector. In the present work we extracted new and improved data for 215-217Th including isomeric decays. The results are discussed and compared to previously published data.

Cross section systematics for the lightest Bi and Po nuclei produced in complete fusion reactions with heavy ions

The production of the very neutron-deficient nuclides $^{184\ensuremath{-}192}\mathrm{Bi}$ and $^{186\ensuremath{-}192}\mathrm{Po}$ in the vicinity of the neutron midshell at N = 104 has been studied by using heavy-ion-induced complete fusion reactions in a series of experiments at the velocity filter SHIP. The cross sections for the xn and pxn evaporation channels of the $^{46}\mathrm{Ti}$+$^{144}\mathrm{Sm}$$\ensuremath{\rightarrow}^{190}\mathrm{Po}{}^{*},$$^{98}\mathrm{Mo}$+$^{92}\mathrm{Mo}$$\ensuremath{\rightarrow}^{190}\mathrm{Po}{}^{*},$$^{50,52}\mathrm{Cr}$+$^{142}\mathrm{Nd}$$\ensuremath{\rightarrow}^{192,194}\mathrm{Po}{}^{*}$, and $^{94,95}\mathrm{Mo}$+$^{93}\mathrm{Nb}$$\ensuremath{\rightarrow}^{187,188}\mathrm{Bi}{}^{*}$ reactions were measured. The results obtained, together with the previously known cross section data for the heavier Bi and Po nuclides, are compared with the results of statistical model calculations carried out with the HIVAP code. It is shown that a satisfactory description of the experimental data requires a significant (up to 35%) reduction of the theoretical fission barriers. The optimal reactions for production of the lightest Bi and Po isotopes are discussed.

Statistics of high-altitude and high-latitude O<sup>+</sup> ion outflows observed by Cluster/CIS

Abstract. The persistent outflows of O+ ions observed by the Cluster CIS/CODIF instrument were studied statistically in the high-altitude (from 3 up to 11 RE) and high-latitude (from 70 to ~90 deg invariant latitude, ILAT) polar region. The principal results are: (1) Outflowing O+ ions with more than 1keV are observed above 10 RE geocentric distance and above 85deg ILAT location; (2) at 6-8 RE geocentric distance, the latitudinal distribution of O+ ion outflow is consistent with velocity filter dispersion from a source equatorward and below the spacecraft (e.g. the cusp/cleft); (3) however, at 8-12 RE geocentric distance the distribution of O+ outflows cannot be explained by velocity filter only. The results suggest that additional energization or acceleration processes for outflowing O+ ions occur at high altitudes and high latitudes in the dayside polar region. Keywords. Magnetospheric physics (Magnetospheric configuration and dynamics, Solar wind-magnetosphere interactions)

FT-ICR: A non-destructive detection for on-line mass measurements at SHIPTRAP

The SHIPTRAP facility is set up behind the velocity filter SHIP at GSI. One of the main physics goals is the direct mass determination of trans-uranium nuclides by Penning trap mass spectrometry. In this contribution the applicability of the non-destructive Fourier Transform-Ion Cyclotron Resonance (FT-ICR) detection technique to mass spectrometry of short-lived nuclides is discussed.

The ion-trap facility SHIPTRAP

The Penning-trap mass spectrometer at the ion trap facility SHIPTRAP is in the final stage of commissioning. First on-line mass measurements of neutron-deficient radionuclides in the rare-earth region around A = 147 were performed in July 2004. Systematic investigations in order to determine systematic errors are ongoing. Further improvements of the efficiency of the system are in preparation, e.g. improved detection schemes and further optimization of the stopping cell. SHIPTRAP will then address exotic nuclides produced in fusion-evaporation reactions at the velocity filter SHIP. This production technique will give access to nuclei not available at ISOL facilities, especially in the transuranium region.

Decay studies of 210-214Fr using α- γ-coincidences

The α-decay fine structure of 210-214Fr has been studied by α-γ-coincidence measurements. The nuclei were produced using the 12C on 209Bi reaction. Evaporation residues recoiling out of the target were separated in-flight by the velocity filter SHIP and stopped in a position-sensitive 16-strip PIPS-detector in order to study their subsequent decays. In the present work new and improved results for 210-214Fr, produced by α-decay of the primary reaction products 214-218Ac, were extracted. The results are discussed and compared to previously published data.

Decay studies of 214-216Ac by α- γ- γ-coincidences

The α-decay fine structure of 214Ac, 215Ac and 216Ac has been studied using the α-γ-coincidence technique. The nuclei were produced by 209Bi( 12C, xn)221-xAc-reactions. Evaporation residues were separated in-flight from the primary beam using the velocity filter SHIP at GSI, Darmstadt. The separated nuclei were implanted into a position-sensitive 16-strip PIPS Si detector and their subsequent decays were measured. In these studies new and improved decay data for 214-216Ac were obtained.

LISE++ : design your own spectrometer

The program LISE is designed to predict intensities and purities for the planning of future experiments with in-flight separators, as well as for beam tuning during experiments where its results can be quickly compared to on-line data. LISE++ is the new generation of the LISE code, which allows the creation of a spectrometer through the use of different sections (dispersive section, velocity filter, electrostatic separator and gas-filled separator ...) called The code has an improved interface, new utilities, and a spectrometer schematics which allows a quick editing of blocks. The code can be freely downloaded from the following sites: http://www.nscl.msu.edu/lise or http://dnr080.jinr.ru/lise .

Ballistic skin simulant

Hydrogels prepared from water solutions containing 10–20 mass% gelatine are generally accepted muscle tissue simulants in terminal ballistic research. They, however, do not have a surface layer which simulates the effect of human skin. The purpose of this research was to find a suitable skin simulant for enhancing the testing fidelity and the credibility of the results with gelatine-based materials when assessing the injury potential of not only high energy bullets, but also especially that of non-penetrating “less lethal” kinetic impact ammunition and relatively low energy ricochet fragments. A skin simulant also permits the simulation and assessment of exit wounds. The mechanical and ballistic properties of human skin and target simulant were established on the basis of results found in the literature. Some errors in these were found. The corrected values are included in this paper for comparison. The target values of the mechanical properties of the skin simulant were the following: threshold velocity v th = 94 ± 4 m/s, tensile strength 18 ± 2 N/mm 2 and elongation at break 65 ± 5%. A selection of synthetic and natural materials was evaluated as skin simulants by analysing their mechanical and ballistic properties. The results were compared to literature values obtained with human cadavers. The tests showed that the best skin simulant of the ones evaluated was semi-finished chrome tanned upholstery “crust” cowhide of 0.9–1.1 mm nominal thickness. Its threshold velocity was 90.7 m/s, tensile strength 20.89 ± 4.11 MPa and elongation at break 61 ± 9%. These values are the same as the average values of human skin. Of the synthetic materials evaluated, 1 mm thick natural rubber can be used on impact side as a threshold velocity filter with some reservations although its theoretical threshold velocity is only 82.9 m/s.

The exterior cusp and its boundary with the magnetosheath: Cluster multi-event analysis

Abstract. We report on the observation of three high-altitude cusp crossings by the Cluster spacecraft under steady northward IMF conditions. The focus of this study is on the exterior cusp and its boundaries. At the poleward edge of the cusp, large downward jets are present; they are characterized by a dawn-dusk component of the convection velocity opposite to the IMF By direction and a gradual evolution (velocity filter effect) corresponding to an injection site located at the high-latitude magnetopause tailward of the cusp, with subsequent sunward convection. As one moves from the poleward edge into the exterior cusp proper, the plasma gradually becomes stagnant as the result of the mirroring and scattering of the aforementioned plasma flows. The existence of such a stagnant region (Stagnant Exterior Cusp: SEC) is found in all events studied here even when the IMF By is large and the clock angle is ~90°. The SEC-magnetosheath boundary appears as a spatial structure that has a normal component of the magnetic field pointing inward, in accordance with a probable connection between the region and the magnetosheath (with northward field). This boundary generally has a deHoffmann-Teller velocity that is slow and oriented sunward and downward, compatible with a discontinuity propagating from a location near the high-latitude magnetopause. Although the tangential stress balance is not always satisfied, the SEC-magnetosheath boundary is possibly a rotational discontinuity. Just outside this boundary, there exists a clear sub-Alfvénic plasma depletion layer (PDL). These results are all consistent with the existence of a nearly steady reconnection site at the high-latitude magnetopause tailward of the cusp. We suggest that the stability of the external discontinuity (and of the whole region) is maintained by the presence of the sub-Alfvénic PDL. However, examination of the electron data shows the presence of heated electrons propagating parallel to the magnetic field (upward) just outside of the SEC-magnetosheath boundary. This appears inconsistent with their source being the northern lobe reconnection site. Finally, the definition of the magnetopause at high latitudes is revisited. To define the SEC-magnetosheath boundary as the magnetopause would lead to the misnaming of the "exterior cusp".