1,556 research outputs found
Molecular hydrogen in the galaxy and galactic gamma rays
Recent surveys of 2.6 mm CO emission and 100 MeV gamma-radiation in the galactic plane reveal a striking correlation suggesting that both emissions may be primarily proportional to the line-of-sight column density of H2 in the inner galaxy. Both the gamma ray and CO data suggest a prominent ring or arm consisting of cool clouds of H2 at a galactocentric distance of approximately 5 kpc with a mean density of approximately 4 atoms/cu cm. The importance of H2 in understanding galactic gamma ray observations is also reflected in the correlation of galactic latitude distribution of gamma rays and dense dust clouds. A detailed calculation of the gamma ray flux distribution in the 0 deg to 180 deg range using the CO data to obtain the average distribution of molecular clouds in the galaxy shows that most of the enhancement in the inner galaxy is due to pion-decay radiation and the 5 kpc ring plays a major role. Detailed agreement with the gamma ray data is obtained with the additional inclusion of contributions from bremsstrahlung and Compton radiation of secondary electrons and Compton radiation from the intense radiation field near the galactic center
Emission of gamma rays shifted from resonant absorption by electron-nuclear double transitions in ^{151}Eu^{2+}:CaF_2
We show that the emission of a gamma-ray photon by a nucleus can be
influenced by a microwave magnetic field acting on the atomic electrons. We
study theoretically these electron-nuclear double transitions (ENDTs) for
^{151}Eu nuclei in a CaF_2 lattice at low temperature, in the presence of a
static magnetic field and of a microwave magnetic field. The ENDTs acquire a
significant intensity for certain resonance frequencies. The ENDTs are of
interest for the identification of the position of the lines in complex
M\"{o}ssbauer spectra.Comment: 8 pages; 3 Postscript figures: Fig. 1, Fig. 2(a), Fig. 2(b
The I-mode confinement regime at ASDEX Upgrade: global propert ies and characterization of strongly intermittent density fluctuations
Properties of the Imode confinement regime on the ASDEX Upgrade tokamak are
summarized. A weak dependence of the power threshold for the LI transition on the toroidal
magnetic field strength is found. During improved confinement, the edge radial electric field
well deepens. Stability calculations show that the Imode pedestal is peelingballooning stable.
Turbulence investigations reveal strongly intermittent density fluctuations linked to the weakly
coherent mode in the confined plasma, which become stronger as the confinement quality
increases. Across all investigated structure sizes (
≈
⊥
k
5
–
12 cm
−
1
, with
⊥
k
the perpendicular
wavenumber of turbulent density fluctuations), the intermittent turbulence bursts are observed.
Comparison with bolometry data shows that they move poloidally toward the Xpoint and
finally end up in the divertor. This might be indicative that they play a role in inhibiting the
density profile growth, such that no pedestal is formed in the edge density profile.European Union (EUROfusion 633053)European Union (EUROfusion AWP15ENR09/IPP02
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