Search results for "MAGNETIC FIELD"
showing 10 items of 1488 documents
Design and Calculations for the New ECRIS at KVI
2005
In this paper a brief description is given of the on‐going upgrade of the CAPRICE‐type ECRIS injector of the K=600 AGOR cyclotron at KVI. This upgrade is motivated by the new TRIμP program, which requires a significant increase of available beam intensity by up to two orders in magnitude. The upgrade follows the AECR design of the university of Jyvaskyla, which was originally pioneered at LBNL (USA). We will discuss the mechanical design and magnetic field calculations of the solenoidal and the permanent magnetic hexapole fields.
A decade of SN 1993J : discovery of radio wavelength effects in the expansion rate
2009
We studied the growth of the shell-like radio structure of supernova SN 1993J in M 81 from September 1993 to October 2003 with very-long-baseline interferometry (VLBI) observations at the wavelengths of 3.6, 6, and 18 cm. We developed a method to accurately determine the outer radius (R) of any circularly symmetric compact radio structure such as SN 1993J. The source structure of SN 1993J remains circularly symmetric (with deviations from circularity under 2%) over almost 4000 days. We characterize the decelerated expansion of SN 1993J until approximately day 1500 after explosion with an expansion parameter m = 0.845 ± 0.005 (R ∝ tm). However, from that day onwards the expansion differs whe…
Test of the generation of High-Frequency Gravitational Waves by irradiating a dielectric film in a resonant cavity
2004
A recent proposal for generating High Frequency Gravitational Waves (HFGW) is based on the conversion of electromagnetic waves into gravitational waves by irradiating a dielectric film in the extreme conditions of a high vacuum and a strong magnetic field. These HFGWs can be tested using an electron paramagnetic resonant spectrometer (EPRS). This device contains all the necessary ingredients: a vacuum chamber, microwave generator, a strong magnetic field, and a resonant cavity where the substance to be analysed is introduced. The EPR spectrum of a very small paramagnetic core in a substance is the graph of the absorption of the paramagnetic core as a function of the strong magnetic field B.…
Gyrotron Operation in the ‘No-Start-Current’ Zone
2018
It is conventionally assumed that the gyrotrons can operate either in the regime of soft self-excitation, where the beam current exceeds the start current, or in the regime of hard excitation, where the beam current is lower than the start current. The authors have found one more possibility of gyrotron operation: in the region where there is no start current at all. Although it is not clear whether this region represents a special interest for gyrotron operation, it can be useful to learn that such opportunity may exist and can be used for interpreting some experimental results.
Timing of the 2008 outburst of SAX J1808.4–3658 with XMM-Newton: a stable orbital-period derivative over ten years
2009
We report on a timing analysis performed on a 62-ks long XMM-Newton observation of the accreting millisecond pulsar SAX J1808.4-3658 during the latest X-ray outburst that started on September 21, 2008. By connecting the time of arrivals of the pulses observed during the XMM observation, we derived the best-fit orbital solution and a best-fit value of the spin period for the 2008 outburst. Comparing this new set of orbital parameters and, in particular, the value of the time of ascending-node passage with the orbital parameters derived for the previous four X-ray outbursts of SAX J1808.4-3658 observed by the PCA on board RXTE, we find an updated value of the orbital period derivative, which …
Small-polaron transport inLa0.67Ca0.33MnO3thin films
1998
We present a detailed study of the activated resistivity of ${\mathrm{La}}_{0.67}{\mathrm{Ca}}_{0.33}{\mathrm{MnO}}_{3}$ films up to 600 K under the influence of high magnetic fields. Data in zero field can be explained by small polaron hopping as treated in the Friedman-Holstein theory. Based on the spin orientation of ferromagnetic clusters in a magnetic field, we develop a phenomenological model describing the temperature and field dependence of the resistivity with a minimum of free parameters. We find that the polarons have a magnetic contribution to their activation energy for hopping which depends on the variation of the spin order with increasing temperature and can be modified by a…
Bright X-Ray Flares in Orion Young Stars from COUP: Evidence for Star-Disk Magnetic Fields?
2005
We have analyzed a number of intense X-ray flares observed in the Chandra Orion Ultradeep Project (COUP), a 13 days observation of the Orion Nebula Cluster (ONC). Analysis of the flare decay allows to determine the size, peak density and magnetic field of the flaring structure. A total of 32 events (the most powerful 1% of COUP flares), have sufficient statistics for the analysis. A broad range of decay times (from 10 to 400 ks) are present in the sample. Peak flare temperatures are often very high, with half of the flares in the sample showing temperatures in excess of 100 MK. Significant sustained heating is present in the majority of the flares. The magnetic structures which are found, a…
Overdamped dynamics of paramagnetic ellipsoids in a precessing magnetic field
2009
We report on the dynamical behavior of paramagnetic ellipsoidal particles dispersed in water and floating above a flat plane when subjected to an external precessing magnetic field. When the magnetic field and the long axis of the particles are on the same plane, two clear regimes are distinguished in which the particles follow the magnetic modulation synchronously or asynchronously. Both regimes are also observed when the field precesses at an angle $\ensuremath{\vartheta}l90\ifmmode^\circ\else\textdegree\fi{}$ with respect to the normal to the confining plane, while the transition frequency increases with decreasing precession angle. We combine experimental observations with a theoretical…
Second harmonic generation by an isolated spin
1970
Abstract The second harmonic generation at microwave frequency by a spin S = 1 2 in a cavity has been studied as a function of the external magnetic field using a resolvent technique, and the average transition rates to states with an increased number of double-frequency photons has been calculated. In spite of the crudeness of the model, a good qualitative agreement has been found between the predictions of the present theory and recent experimental results on non-linear behaviour of paramagnetic spin systems in a microwave field.
Effects of the magnetodipolar interactions in the alternating magnetic fields
1999
A macroscopic theory for the description of the structure formation in a system of magnetic dipoles under the action of a high-frequency rotating field is presented. Continuum equations for the effective magnetic field strength describing particle interactions are derived. It is shown that, contrary to the case of a constant magnetic field, where the demagnetizing field arising from a concentration fluctuation stabilizes the system with respect to the phase separation, the same concentration fluctuation will be amplified in the case of a rotating magnetic field, leading to the formation of a layered structure. The extensions of the model necessary for the description of the formation of the…