TPC track distortions: correction maps for magnetic and static electric inhomogeneities

Inhomogeneities of the magnetic and electric fields in the active TPC volume lead to displacements of cluster coordinates, and therefore to track distortions. In case of good data taking conditions, the largest effects are expected from the inhomogeneity of the solenoidal magnetic field, and from a distortion of the electric field arising from a high voltage misalignment between the outer and inner field cages. Both effects are stable over the entire HARP data taking. The displacements are large compared to the azimuthal coordinate resolution but can be corrected with sufficient precision, except at small TPC radius. The high voltage misalignment between the outer and inner field cages is identified as the likely primary cause of sagitta distortions of TPC tracks. The position and the length of the target plays an important role. Based on a detailed modelling of the magnetic and static electric field inhomogeneities, precise correction maps for both effects have been calculated. Predictions from the correction maps are compared with laser data

Analysis of natural neutron flux in a seismically active zone

International audienceIn a seismically active zone in the near Almaty area (Kazakhstan) since 1996 observations of variations of a natural neutron flux have been conducted. Sometimes the neutron flux rises sharply within the one-hour interval in comparison with the background. It occurs on the eve of activation of seismic processes. Increase of the neutron flux level had taken place from 1 h to 10 days prior to earthquakes. It is also indicated a tendency of growth of the anomaly level in accordance with the growth of energetic class of the subsequent earthquake. A character of connection between the neutron flux and earthquakes is still not clear. It is proposed that the neutron flux anomalies caused by variations of cosmic radiation intensity under action of fluxes of solar material, which is burst into interplanetary space (solar wind) during solar flares. Energy of the solar wind transferred to Earth puts into action a trigger mechanism of the process of initiation of earthquakes at those places where conditions have already been prepared for them. The neutron flux anomalies can be used as substantial additional information for classical geophysical methods of short-term earthquake prediction

TPC cross-talk correction: CERN-Dubna-Milano algorithm and results

The CDM (CERN-Dubna-Milano) algorithm for TPC Xtalk correction is presented and discussed in detail. It is a data-driven, model-independent approach to the problem of Xtalk correction. It accounts for arbitrary amplitudes and pulse shapes of signals, and corrects (almost) all generations of Xtalk, with a view to handling (almost) correctly even complex multi-track events. Results on preamp amplification and preamp linearity from the analysis of test-charge injection data of all six TPC sectors are presented. The minimal expected error on the measurement of signal charges in the TPC is discussed. Results are given on the application of the CDM Xtalk correction to test-charge events and krypton events

Performance of TPC crosstalk correction

The performance of the CERN-Dubna-Milano (CDM) algorithm for TPC crosstalk correction is presented. The algorithm is designed to correct for uni-directional and bi-directional crosstalk, but not for self-crosstalk. It reduces at the 10% level the number of clusters, and the number of pads with a signal above threshold. Despite of dramatic effects in selected channels with complicated crosstalk patterns, the average longitudinal signal shape of a hit, and the average transverse signal shape of a cluster, are little affected by uni-directional and bi-directional crosstalk. The longitudinal signal shape of hits is understood in terms of preamplifier response, longitudinal diffusion, track inclination, and self-crosstalk. The transverse signal shape of clusters is understood in terms of the TPC's pad response function. The CDM crosstalk correction leads to an average charge decrease at the level of 15%, though with significant differences between TPC sectors. On the whole, crosstalk constitutes a relatively benign malfunction of the TPC readout which, after correction by the CDM algorithm and with proper attention to self-crosstalk, is not an obstacle to progress with physics analysis

Paleoflooding reconstruction from Holocene levee deposits in the Lower Meuse valley, the Netherlands

This study investigates the Holocene levee deposits and paleoflooding history of the Lower Meuse in the Netherlands based on archeological investigations and sedimentary analyses (grain size, end-member modelling, magnetic susceptibility and thermogravimetric analyses). The levee on the left bank in the study area near Ooijen contains a continuous sedimentary record in the NW downstream part. The archeological evidence and sedimentary results, including a grain size based flood energy index (LFEI), indicate that the Lower Meuse experienced a quiescent flooding period and low sedimentation rates during the mid-late Mesolithic when the levee was low and human influence was minor. Deposition during the Mesolithic shows a fining-upward trend and a highly-developed soil containing abundant artefacts. During the Neolithic and Bronze Age, the flooding intensity was low but gradually increased to a moderate level probably because of deforestation and increased runoff. Limited Bronze Age findings may reflect decreased human activity because of the increased flooding. Starting from the Iron Age, the Meuse experienced a generally enhanced flooding regime, which is reflected by erosion and coarsened sedimentation in the Iron Age and Roman Period. The high peak discharges during the Iron Age may have re-opened a low-lying paleochannel near to the levee during the intensified floods. This general increasing trend is interrupted by the lower flooding phase in the early Middle Ages (Dark Ages). From the middle to the late Middle Ages, the floods intensified again. The coarsening deposition and higher sedimentation rates since the Iron Age resulted from increased floods and higher sediment supply by deforestation and soil erosion. The findings of this study agree with a recent paleoflood reconstruction for the Lower Meuse by using a floodplain archive, implying that levee sediment records have potential in paleohydrological studies if the completeness of the record and chronological information is guaranteed

On spin-rotation contribution to nuclear spin conversion in C_{3v}-symmetry molecules. Application to CH_3F

The symmetrized contribution of E-type spin-rotation interaction to conversion between spin modifications of E- and A_1-types in molecules with C_{3v}-symmetry is considered. Using the high-J descending of collisional broadening for accidental rotational resonances between these spin modifications, it was possible to co-ordinate the theoretical description of the conversion with (updated) experimental data for two carbon-substituted isotopes of fluoromethane. As a result, both E-type spin-rotation constants are obtained. They are roughly one and a half times more than the corresponding constants for (deutero)methane.Comment: 13 pages with single-spacing, REVTeX, no figures, accepted for publication in <J. Phys. B