2,504 research outputs found
Isochronicity Correction in the CR Storage Ring
A challenge for nuclear physics is to measure masses of exotic nuclei up to
the limits of nuclear existence which are characterized by low production cross
sections and short half-lives. The large acceptance Collector Ring (CR) at FAIR
tuned in the isochronous ion-optical mode offers unique possibilities for
measuring short-lived and very exotic nuclides. However, in a ring designed for
maximal acceptance, many factors limit the resolution. One point is a limit in
time resolution inversely proportional to the transverse emittance. But most of
the time aberrations can be corrected and others become small for large number
of turns. We show the relations of the time correction to the corresponding
transverse focusing and that the main correction for large emittance
corresponds directly to the chromaticity correction for transverse focusing of
the beam. With the help of Monte-Carlo simulations for the full acceptance we
demonstrate how to correct the revolution times so that in principle
resolutions of dm/m=1E-6 can be achieved. In these calculations the influence
of magnet inhomogeneities and extended fringe fields are considered and a
calibration scheme also for ions with different mass-to-charge ratio is
presented.Comment: 6 figures, recised version May 201
Probing the gravitational redshift with an Earth-orbiting satellite
We present an approach to testing the gravitational redshift effect using the RadioAstron satellite. The experiment is based on a modification of the Gravity Probe A scheme of nonrelativistic Doppler compensation and benefits from the highly eccentric orbit and ultra-stable atomic hydrogen maser frequency standard of the RadioAstron satellite. Using the presented techniques we expect to reach an accuracy of the gravitational redshift test of order 10^(−5), a magnitude better than that of Gravity Probe A. Data processing is ongoing, our preliminary results agree with the validity of the Einstein Equivalence Principle
Dynamics of perpendicular recording heads
3D modeling and inductance measurements were used to design an ultra-high frequency perpendicular system. Kerr microscopy and spin-stand experiments with focused ion beam (FI-B) trimmed perpendicular heads and perpendicular media directly verified the high frequency concepts
Recommended from our members
Magnetic characterization of perpendicular recording media
In this paper, we describe techniques for the magnetic characterization of perpendicular recording media. Such measurements made using traditional techniques, such as the vibrating sample magnetometry (VSM) and alternating gradient force magnetometer (AGFM), have to be corrected for the sample shape demagnetizing factor, which is often found not to be equal to -4p. For measurements other than the simple hysteresis loop, such as remanence curves, this correction must be carried out in real time and we describe the method by which this can be achieved and the process for achieving the correct demagnetization of perpendicular films prior to measurements of the isothermal remanent magnetization curve. A further complication is that real perpendicular media have a soft underlayer beneath the recording layer, which swamps and confuses signals from instruments such as VSM or AGFM. Hence, we describe the construction and use of a magnetooptical Kerr effect magnetometer, which does not penetrate significantly into the soft layer and enables the perpendicular layer to be measured independently. We describe the properties of a traditional alloy perpendicular medium and a Co-Pd multilayer system, which in the latter case exhibits multiple switching behavior. We also address the issue of the effect of the soft underlayer on the coupling in similar longitudinal films and find that the presence of the underlayer induces significant additional coupling effects that may well give rise to an increase in noise in recorded signal
Hydrides and fracture of pure zirconium and zircaloy-4 hydrogenated at temperatures typical for loss-of-coolant accident conditions
Search for Oscillation of the Electron-Capture Decay Probability of Pm
We have searched for time modulation of the electron capture decay
probability of Pm in an attempt to confirm a recent claim from a group
at the Gesellschaft f\"{u}r Schwerionenforschung (GSI). We produced Pm
via the Sn(Na, 5n)Pm reaction at the Berkeley 88-Inch
Cyclotron with a bombardment time short compared to the reported modulation
period. Isotope selection by the Berkeley Gas-filled Separator is followed by
implantation and a long period of monitoring the Nd K x-rays
from the daughter. The decay time spectrum of the x-rays is well-described by a
simple exponential and the measured half-life of 40.68(53) seconds is
consistent with the accepted value. We observed no oscillatory modulation at
the proposed frequency at a level 31 times smaller than that reported by
Litvinov {\it et al.} (Phys. Lett. B 664 (2008) 162; arXiv:0801.2079
[nucl-ex]). A literature search for previous experiments that might have been
sensitive to the reported modulation uncovered another example in Eu
electron-capture decay. A reanalysis of the published data shows no oscillatory
behavior.Comment: 12 pages (double-spaced), 6 figure
- …