731 research outputs found
Impact of climate induced glacial melting on coastal marine systems in the Western Antarctic Peninsula region
IMCOAST is an international research program that features a multidisciplinary approach involving geo and biological sciences, field investigations, remote sensing and modeling and knowledge into the hydrographical and biological history of the marine coastal ecosystems of the Western Antarctic Peninsula region
Ramsey's Method of Separated Oscillating Fields and its Application to Gravitationally Induced Quantum Phaseshifts
We propose to apply Ramsey's method of separated oscillating fields to the
spectroscopy of the quantum states in the gravity potential above a vertical
mirror. This method allows a precise measurement of quantum mechanical
phaseshifts of a Schr\"odinger wave packet bouncing off a hard surface in the
gravitational field of the earth. Measurements with ultra-cold neutrons will
offer a sensitivity to Newton's law or hypothetical short-ranged interactions,
which is about 21 orders of magnitude below the energy scale of
electromagnetism.Comment: 7 pages, 6 figure
Constrains on non-Newtonian gravity from the experiment on neutron quantum states in the Earth's gravitational field
An upper limit to non-Newtonian attracive forces is obtained from the
measurement of quantum states of neutrons in the Earth's gravitational field.
This limit improves the existing constrains in the nanometer range
Quantum motion of a neutron in a wave-guide in the gravitational field
We study theoretically the quantum motion of a neutron in a horizontal
wave-guide in the gravitational field of the Earth. The wave-guide in question
is equipped with a mirror below and a rough absorber above. We show that such a
system acts as a quantum filter, i.e. it effectively absorbs quantum states
with sufficiently high transversal energy but transmits low-energy states. The
states transmitted are mainly determined by the potential well formed by the
gravitational field of the Earth and the mirror. The formalism developed for
quantum motion in an absorbing wave-guide is applied to the description of the
recent experiment on the observation of the quantum states of neutrons in the
Earth's gravitational field
Measurement of the neutron lifetime using a gravitational trap and a low-temperature Fomblin coating
We present a new value for the neutron lifetime of 878.5 +- 0.7 stat. +- 0.3
syst. This result differs from the world average value (885.7 +- 0.8 s) by 6.5
standard deviations and by 5.6 standard deviations from the previous most
precise result. However, this new value for the neutron lifetime together with
a beta-asymmetry in neutron decay, Ao, of -0.1189(7) is in a good agreement
with the Standard Model.Comment: 11 pages, 9 figures; extended content with some correction
Determination of the Weak Axial Vector Coupling from a Measurement of the Beta-Asymmetry Parameter A in Neutron Beta Decay
We report on a new measurement of the neutron beta-asymmetry parameter
with the instrument \perkeo. Main advancements are the high neutron
polarization of from a novel arrangement of super mirror
polarizers and reduced background from improvements in beam line and shielding.
Leading corrections were thus reduced by a factor of 4, pushing them below the
level of statistical error and resulting in a significant reduction of
systematic uncertainty compared to our previous experiments. From the result
, we derive the ratio of the axial-vector to the vector
coupling constant Comment: 5 pages, 4 figure
Testing the Unitarity of the CKM Matrix with a Space-Based Neutron Decay Experiment
If the Standard Model is correct, and fundamental fermions exist only in the
three generations, then the CKM matrix should be unitary. However, there
remains a question over a deviation from unitarity from the value of the
neutron lifetime. We discuss a simple space-based experiment that, at an orbit
height of 500 km above Earth, would measure the kinetic-energy, solid-angle,
flux spectrum of gravitationally bound neutrons (kinetic energy K<0.606 eV at
this altitude). The difference between the energy spectrum of neutrons that
come up from the Earth's atmosphere and that of the undecayed neutrons that
return back down to the Earth would yield a measurement of the neutron
lifetime. This measurement would be free of the systematics of laboratory
experiments. A package of mass kg could provide a 10^{-3} precision in
two years.Comment: 10 pages, 4 figures. Revised and updated for publicatio
Konzeption und Entwicklung eines Condition Monitoring Systems mit Low Cost Sensoren zur Überwachung von Roboterschwingungen
Im Rahmen dieser Veröffentlichung wird ein Konzept zur Erfassung des Schwingungsverhaltens von Industrierobotern mit Hilfe von Low Cost Sensoren vorgestellt. Durch dieses sollen die dynamischen Eigenschaften des Industrieroboters im gesamten Arbeitsraum untersucht werden. Die Roboterstruktur wird dazu durch eine speziell konstruierte Unwuchtscheibe angeregt. Das Messsystem besteht aus einem Beschleunigungssensor, einem Arduino-Mikrocontroller und einem eigens entwickelten Mess- und Auswerteprogramm in der Softwareumgebung MATLAB®. Die Validierung des Konzeptes erfolgt jeweils mit Messreihen an einem Kragbalken sowie an einem Industrieroboter durch den Vergleich mit einem Referenzmesssystem der Firma Brüel & Kjaer. Durch das entwickelte Low Cost Condition Monitoring System lassen sich die Anregungsfrequenzen und –amplituden mit hinreichender Genauigkeit erfassen und Rückschlüsse auf das Schwingungsverhalten des Industrieroboters ziehen
A Neutron Interferometric Method to Provide Improved Constraints on Non-Newtonian Gravity at the Nanometer Scale
In recent years, an energetic experimental program has set quite stringent
limits on a possible "non - 1/r^2" dependence on gravity at short length
scales. This effort has been largely driven by the predictions of theories
based on compactification of extra spatial dimensions. It is characteristic of
many such theories that the strength and length scales of such anomalous
gravity are not clearly determined from first principles. As a result, it is
productive to extend the current limits the range and strength of such
hypothetical interactions. As a heavy, neutral, and (almost) stable particle,
the neutron provides an ideal probe for the study of such hypothetical
interactions at very short range. In this work, we describe methods based on
neutron interferometry which have the capability to provide improved
sensitivity non-Newtonian forces down to length scales at and below an
nanometer.Comment: PDF-fil
Study of the neutron quantum states in the gravity field
We have studied neutron quantum states in the potential well formed by the
earth's gravitational field and a horizontal mirror. The estimated
characteristic sizes of the neutron wave functions in the two lowest quantum
states correspond to expectations with an experimental accuracy. A
position-sensitive neutron detector with an extra-high spatial resolution of ~2
microns was developed and tested for this particular experiment, to be used to
measure the spatial density distribution in a standing neutron wave above a
mirror for a set of some of the lowest quantum states. The present experiment
can be used to set an upper limit for an additional short-range fundamental
force. We studied methodological uncertainties as well as the feasibility of
improving further the accuracy of this experiment
- …