110 research outputs found
Particle production in the outflow of a midlatitude storm
The concentrations of atmospheric gases and condensation nuclei (CN) or aerosol in the outflow of a storm were measured aboard a NASA DC-8 aircraft, as described in a companion paper [Twohy et al., 2002]. The data are used here to study the production of the aerosol. Major fluctuations in CN concentration are observed, in correlation with gas-phase species, but these are shown to arise as the result of the mixing of two distinct air masses. It is deduced that the CN originated in a storm outflow air mass and that its concentration before mixing was approximately uniform over a flight distance of about 200 km. The formation of the aerosol by nucleation followed by growth and coagulation is analyzed assuming that it consists of water and sulphuric acid produced locally by the oxidation of SO2. The analysis uses analytic models, and it is concluded that a 5 min burst of nucleation was followed by growth and coagulation over a period of about 5 hours. Both the mass and number concentrations of the observed aerosol can be reproduced by this analysis within a timescale consistent with that of the storm. The final number concentration is very insensitive to the initial SO2 concentration
Contactless 2-dimensional laser sensor for 3-dimensional wire position and tension measurements
We have developed a contact-free 2-dimensional laser sensor with which the
position of wires can be measured in 3 dimensions with an accuracy of better
than 10 micrometer and with which the tension of the wires can be determined
with an accuracy of 0.04 N. These measurements can be made from a distance of
15 cm. The sensor consists of commercially available laser pointers, lenses,
color filters and photodiodes. In our application we have used this laser
sensor together with an automated 3 dimensional coordinate table. For a single
position measurement, the laser sensor is moved by the 3-dimensional coordinate
table in a plane and determines the coordinates at which the wires intersect
with this plane. The position of the plane itself (the third coordinate) is
given by the third axis of the measurement table which is perpendicular to this
plane. The control and readout of the table and the readout of the laser sensor
were realized with LabVIEW. The precision of the position measurement in the
plane was determined with wires of 0.2 mm and 0.3 mm diameter. We use the
sensor for the quality assurance of the wire electrode modules for the KATRIN
neutrino mass experiment. We expect that the precision is at least comparable
or better if the wires are thinner. Such a device could be well suited for the
measurement of wire chamber geometries even with more than one wire layer.Comment: 15 pages, 8 figure
Precision high voltage divider for the KATRIN experiment
The Karlsruhe Tritium Neutrino Experiment (KATRIN) aims to determine the
absolute mass of the electron antineutrino from a precise measurement of the
tritium beta-spectrum near its endpoint at 18.6 keV with a sensitivity of 0.2
eV. KATRIN uses an electrostatic retardation spectrometer of MAC-E filter type
for which it is crucial to monitor high voltages of up to 35 kV with a
precision and long-term stability at the ppm level. Since devices capable of
this precision are not commercially available, a new high voltage divider for
direct voltages of up to 35 kV has been designed, following the new concept of
the standard divider for direct voltages of up to 100 kV developed at the
Physikalisch-Technische Bundesanstalt (PTB). The electrical and mechanical
design of the divider, the screening procedure for the selection of the
precision resistors, and the results of the investigation and calibration at
PTB are reported here. During the latter, uncertainties at the low ppm level
have been deduced for the new divider, thus qualifying it for the precision
measurements of the KATRIN experiment.Comment: 22 pages, 12 figure
Low Energy Neutrino Physics after SNO and KamLAND
In the recent years important discoveries in the field of low energy neutrino
physics (E in the MeV range) have been achieved. Results of the
solar neutrino experiment SNO show clearly flavor transitions from to
. In addition, the long standing solar neutrino problem is
basically solved. With KamLAND, an experiment measuring neutrinos emitted from
nuclear reactors at large distances, evidence for neutrino oscillations has
been found. The values for the oscillation parameters, amplitude and phase,
have been restricted. In this paper the potential of future projects in low
energy neutrino physics is discussed. This encompasses future solar and reactor
experiments as well as the direct search for neutrino masses. Finally the
potential of a large liquid scintillator detector in an underground laboratory
for supernova neutrino detection, solar neutrino detection, and the search for
proton decay is discussed.Comment: Invited brief review, World Scientific Publishing Compan
Final Results from phase II of the Mainz Neutrino Mass Search in Tritium Decay
The paper reports on the improved Mainz experiment on tritum
spectroscopy which yields a 10 times' higher signal to background ratio than
before. The main experimental effects and systematic uncertainties have been
investigated in side experiments and possible error sources have been
eliminated. Extensive data taking took place in the years 1997 to 2001. A
residual analysis of the data sets yields for the square of the electron
antineutrino mass the final result of eV/c. We derive an upper limit of
eV/c at 95% confidence level for the mass itself.Comment: 22 pages, 22 figures submitted to EPJ
First detection and energy measurement of recoil ions following beta decay in a Penning trap with the WITCH experiment
The WITCH experiment (Weak Interaction Trap for CHarged particles) will
search for exotic interactions by investigating the beta-neutrino angular
correlation via the measurement of the recoil energy spectrum after beta decay.
As a first step the recoil ions from the beta-minus decay of 124In stored in a
Penning trap have been detected. The evidence for the detection of recoil ions
is shown and the properties of the ion cloud that forms the radioactive source
for the experiment in the Penning trap are presented.Comment: 9 pages, 6 figures (9 figure files), submitted to European Physical
Journal
Neutrino Mass and Oscillation
The question of neutrino mass is one of the major riddles in particle
physics. Recently, strong evidence that neutrinos have nonzero masses has been
found. While tiny, these masses could be large enough to contribute
significantly to the mass density of the universe. The evidence for
nonvanishing neutrino masses is based on the apparent observation of neutrino
oscillation -- the transformation of a neutrino of one type or "flavor" into
one of another. We explain the physics of neutrino oscillation, and review and
weigh the evidence that it actually occurs in nature. We also discuss the
constraints on neutrino mass from cosmology and from experiments with negative
results. After presenting illustrative neutrino mass spectra suggested by the
present data, we consider how near- and far-future experiments can further
illuminate the nature of neutrinos and their masses.Comment: 43 pages, 8 figures, to appear in the Annual Review of Nuclear and
Particle Science, Vol. 49 (1999
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