13,274 research outputs found

    Commissioning of the 1.4 Mev/u High Current Heavy Ion Linac at Gsi

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    The disassembly of the Unilac prestripper linac of the Wideroe type took place at the beginning of 1999. An increase of more than two orders of magnitude in particle number for the most heavy elements in the SIS had to be gained. Since that time the new High Current Injector (HSI) consisting of H-type RFQ and DTL-structures for dual beam operation was installed and successfully commissioned. The High Charge Injector (HLI) supplied the main linac during that time. Simultaneously conditioning and running in of the rf-transmitters and rf-structures were done. The HSI commissioning strategy included beam investigation after each transport and acceleration section, using a versatile diagnostic test stand. Results of the extensive commissioning measurements (e.g. transverse emittance, bunch width, beam transmission) behind LEBT, RFQ, Super Lens, IH tank I and II and stripping section will be discussed. An 40Ar1+ beam coming from a MUCIS ion source was used to fill the linac up to the theoretical space charge limit. Routine operation started in November 1999.Comment: Linac 2000, FR201, 5 pages, 8 figure

    Stellar Velocity Dispersion and Black Hole Mass in the Blazar Markarian 501

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    The recently discovered correlation between black hole mass and stellar velocity dispersion provides a new method to determine the masses of black holes in active galaxies. We have obtained optical spectra of Markarian 501, a nearby gamma-ray blazar with emission extending to TeV energies. The stellar velocity dispersion of the host galaxy, measured from the calcium triplet lines in a 2"x3.7" aperture, is 372 +/- 18 km/s. If Mrk 501 follows the M-sigma correlation defined for local galaxies, then its central black hole has a mass of (0.9-3.4)x10^9 solar masses. This is significantly larger than some previous estimates for the central mass in Mrk 501 that have been based on models for its nonthermal emission. The host galaxy luminosity implies a black hole of 6x10^8 solar masses, but this is not in severe conflict with the mass derived from the M-sigma relation because the M_BH-L_bulge correlation has a large intrinsic scatter. Using the emission-line luminosity to estimate the bolometric luminosity of the central engine, we find that Mrk 501 radiates at an extremely sub-Eddington level of L/L_Edd ~ 10^-4. Further applications of the M-sigma relation to radio-loud active galactic nuclei may be useful for interpreting unified models and understanding the relationship between radio galaxies and BL Lac objects.Comment: To appear in ApJ Letters. 5 pages, 2 figure

    A simple remark on a flat projective morphism with a Calabi-Yau fiber

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    If a K3 surface is a fiber of a flat projective morphisms over a connected noetherian scheme over the complex number field, then any smooth connected fiber is also a K3 surface. Observing this, Professor Nam-Hoon Lee asked if the same is true for higher dimensional Calabi-Yau fibers. We shall give an explicit negative answer to his question as well as a proof of his initial observation.Comment: 8 pages, main theorem is generalized, one more remark is added, mis-calculation and typos are corrected etc

    Theoretical and experimental investigations of the drag of installed aircraft radiators

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    The present report proposes the determination of the absolute magnitude of the total radiator drag and, in addition, of the different causes of the radiator drag

    Accelerator Operation at the GSI High Current Injector

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    The correlation potential in density functional theory at the GW-level: spherical atoms

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    As part of a project to obtain better optical response functions for nano materials and other systems with strong excitonic effects we here calculate the exchange-correlation (XC) potential of density-functional theory (DFT) at a level of approximation which corresponds to the dynamically- screened-exchange or GW approximation. In this process we have designed a new numerical method based on cubic splines which appears to be superior to other techniques previously applied to the "inverse engineering problem" of DFT, i.e., the problem of finding an XC potential from a known particle density. The potentials we obtain do not suffer from unphysical ripple and have, to within a reasonable accuracy, the correct asymptotic tails outside localized systems. The XC potential is an important ingredient in finding the particle-conserving excitation energies in atoms and molecules and our potentials perform better in this regard as compared to the LDA potential, potentials from GGA:s, and a DFT potential based on MP2 theory.Comment: 13 pages, 9 figure
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