5,921 research outputs found
Micromegas TPC studies at high magnetic fields using the charge dispersion signal
The International Linear Collider (ILC) Time Projection Chamber (TPC)
transverse space-point resolution goal is 100 microns for all tracks including
stiff 90 degree tracks with the full 2 meter drift. A Micro Pattern Gas
Detector (MPGD) readout TPC can achieve the target resolution with existing
techniques using 1 mm or narrower pads at the expense of increased detector
cost and complexity. The new MPGD readout technique of charge dispersion can
achieve good resolution without resorting to narrow pads. This has been
demonstrated previously for 2 mm x 6 mm pads with GEMs and Micromegas in cosmic
ray tests and in a KEK beam test in a 1 Tesla magnet. We have recently tested a
Micromegas-TPC using the charge dispersion readout concept in a high field
super-conducting magnet at DESY. The measured Micromegas gain was found to be
constant within 0.5% for magnetic fields up to 5 Tesla. With the strong
suppression of transverse diffusion at high magnetic fields, we measure a flat
50 micron resolution at 5 Tesla over the full 15 cm drift length of our
prototype TPC.Comment: 7 pages, 3 figure
Accurate estimations of circumstellar and interstellar lines of quadruply ionized vanadium using the coupled cluster approach
Accurate {\it ab initio} calculations have been carried out to study the
valence electron removal energies and oscillator strengths of astrophysically
important electromagnetic transitions of quadruply ionized vanadium, .
Many important electron correlations are considered to all-orders using the
relativistic coupled-cluster theory. Calculated ionization potentials and fine
structure splittings are compared with the experimental values, wherever
available. To our knowledge, oscillator strengths of electric dipole
transitions are predicted for the first time for most of the transitions. The
transitions span in the range of ultraviolet, visible and near infrared regions
and are important for astrophysical observations.Comment: Submitted in Astrophysical
RF amplification property of the MgO-based magnetic tunnel junction using field-induced ferromagnetic resonance
The radio-frequency (RF) voltage amplification property of a tunnel
magnetoresistance device driven by an RF external-magnetic-field-induced
ferromagnetic resonance was studied. The proposed device consists of a magnetic
tunnel junction (MTJ) and an electrically isolated coplanar waveguide. The
input RF voltage applied to the waveguide can excite the resonant dynamics in
the free layer magnetization, leading to the generation of an output RF voltage
under a DC bias current. The dependences of the RF voltage gain on the static
external magnetic field strength and angle were systematically investigated.
The design principles for the enhancement of the gain factor are also
discussed.Comment: 12 pages, 3 figure
Green Inhibitors for Prevention of Metal and Alloys Corrosion: An Overview
Corrosion control of metal is of technical, economical, environmental and aesthetical importance. The use of inhibitor is the best way to prevent metal and alloys from corrosion. There is an intensive effort underway to develop new plant origin corrosion inhibitors for metal subjected to various environmental conditions. These efforts are motivated by the desire to replace toxic organic corrosion inhibitors used for mitigation of corrosion of various metals and alloys in solutions. Plants represent a class of interesting source of compounds currently being explored for use in metal corrosion protection in most systems, as possible replacement of toxic synthetic inhibitors. The green corrosion inhibitors are bio degradable, non-toxic, environmentally benign, and low cost, are obtained from renewable resources with minimal health and safety concerns. Investigations of corrosion inhibiting abilities of tannins, alkaloids, organic amino acids and organic dyes of plant origin are of interest. Development of computational modeling backed by wet results would help in understanding the mechanism of inhibition action, their adsorption patterns, inhibitor-metal surface interface and help in the development of designer inhibitor with an understanding of the time required for the release of self-healing inhibitors. The present paper restricts itself mainly to the plant materials as “Green Corrosion Inhibitor”. Keywords: Green Corrosion Inhibitor, Corrosion Inhibition, Plant Extracts
Relativistic calculations of the lifetimes and hyperfine structure constants in Zn
This work presents accurate {\it ab initio} determination of the magnetic
dipole (M1) and electric quadrupole (E2) hyperfine structure constants for the
ground and a few low-lying excited states in Zn, which is one of
the interesting systems in fundamental physics. The coupled-cluster (CC) theory
within the relativistic framework has been used here in this calculations. Long
standing demands for a relativistic and highly correlated calculations like CC
can be able to resolve the disagreements among the lifetime estimations
reported previously for a few low-lying states of Zn. The role of
different electron correlation effects in the determination of these quantities
are discussed and their contributions are presented.Comment: 9 pages, 1 figure. submitted to J. Phys. B Fast Trac
Realization of astrosat Model with Fused Deposition Modelling
The current work focuses on the challenges faced while realizing the 3D Model of ASTROSAT using Fused Deposition Modelling (FDM) - A material extrusion based additive manufacturing technology. Initially, the entire assembly of the ASTROSAT was studied and modified appropriately to suit the demonstration model. The modified assembly was scaled down to 1:6 scale. The scaled down model was then re-modified at the local subsystems (or individual component) level, according to the manufacturability through FDM and this was the major challenge faced due to constraint on minimum printable feature size. All the subsystems or individual components were converted to STL format and were printed on FORTUS 400MC of Stratasys. Thus obtained 3D printed parts were assembled as per the assembly drawing. It was found that, the FDM technology and Additive Manufacturing technology as a whole, is very useful in realizing the complicated demonstration modelsin a very short duration, without compromising the prominent engineering features
Resolution studies of cosmic-ray tracks in a TPC with GEM readout
A large volume TPC is a leading candidate for the central tracking detector
at a future high energy linear collider. To improve the resolution a new
readout based on micro-pattern gas detectors is being developed. Measurements
of the spatial resolution of cosmic-ray tracks in a GEM TPC are presented. We
find that the resolution suffers if the readout pads are too wide with respect
to the charge distribution at the readout plane due to insufficient charge
sharing. For narrow pads of 2 x 6 mm**2 we measure a resolution of 100
micometer at short drift distances in the absence of an axial magnetic field.
The dependence of the spatial resolution as a function of drift distance allows
the determination of the underlying electron statistics. Our results show that
the present technique uses about half the statistical power available from the
number of primary electrons. The track angle effect is observed as expected.Comment: 18 pages, 8 figures, version as published in Nucl. Inst. Met
- …