Search results for "electromagnetic"
showing 10 items of 1595 documents
Duality relation between radiation thermodynamics and cosmic string loop thermodynamics
2011
We discuss thermodynamics of electromagnetic radiation, with p=(1/3){rho} and S{proportional_to}T{sup 3}V, and of cosmic string loops, with p=-(1/3){rho} and S{proportional_to}T{sup -3}V, where p stands for pressure, T temperature, {rho} energy density, S entropy, and V volume. We write the thermodynamic formalisms under a common framework that illustrates their formal relationship and allows us to go from one to the other through a smooth transformation. From a microscopic perspective, these relations arise from the energy relations u({lambda})=hc/{lambda} for the photons of electromagnetic radiation, and u(l)=(c{sup 4}/a{sup 2}G)l for cosmic string loops, a being a numerical (dimensionles…
Radiation resistance and optical properties of lead fluoride Cherenkov crystals
1998
Abstract Optical properties of large size lead fluoride (PbF 2 ) crystals of three different manufacturers and their degradation caused by 60 Co γ-radiation have been investigated. Transmission losses have been systematically studied at absorbed energy doses between 0.1 and 7 kGy. Several radiation induced absorption bands have been observed. Optical bleaching with light of wavelengths ≳365 nm has been found very effective to restore the original characteristics even after repeated irradiations. This observation together with the high density and the ultraviolet extended transmission make PbF 2 an excellent choice for high rate and high resolution e.m. calorimetry.
Luminescent detectors of ionising radiation
2003
Abstract At present in slow neutron imaging an active layer of an imaging plate IP contains a mixture of storage phosphors, usually BaFBr:Eu 2+ used for imaging of X-rays, and a neutron converter material, usually Gd 2 O 3 , LiF. A novel Li-containing luminescent material perspective for a direct neutron conversion and storage is discussed. Irradiation of LiBaF 3 crystals results in generation of Frenkel defect pairs and creation of F-type centres responsible for three absorption bands in UV-and visible spectral region. Because photo-stimulation in each of these absorption bands leads to bleaching of induced absorption, the F-type colour centres are convenient for storage of radiation dose.…
Determination of helium number densities in high-frequency electrodeless plasma
2010
Abstract The number densities of He first excited states 2 3 S 1 , 2 1 S 0 , 2 3 P 0,1,2 , and 2 1 P 0 were measured by absorption and self-absorption methods. The emission lines in the range 290–730 nm were used to determine the number densities of He metastable and resonant states of inductively coupled high-frequency electrodeless lamps filled with helium at pressure 0.1 Torr. The obtained number densities of helium metastable levels 2 3 S 1 and 2 1 S 0 are 2×10 12 and 3×10 11 cm −3 , respectively. For the 2 3 P 0,1,2 and 2 1 P 0 levels the determined number densities are ten times smaller than that of the metastable levels. Values of number densities from measurements using both method…
A new frozen-spin target for 4π particle detection
1999
Abstract A new frozen-spin target has been developed, that allows the detection of emitted particles in an angular acceptance of almost 4π in the laboratory frame. The central part of this new target represents a 3He/4He dilution refrigerator that is installed horizontally along the beam axis. The refrigerator includes an internal superconducting holding coil to maintain the nucleon polarization in the frozen-spin mode longitudinally to the beam. The design of the dilution refrigerator and the use of an internal holding coil enabled for the first time the measurement of a spin-dependent total cross section in combination with a polarized solid state target. This new frozen-spin target was u…
Resonant Nuclear Fusion Processes and the Gamma Rays of SS 433
1984
Gamma-ray spectral lines have recently been reported coming from the celestial object SS 433, which is known to emit high-speed jets in opposite directions. The proposed identification of the lines as coming from fusion reactions on nitrogen nuclei as part of the carbon-nitrogen-oxygen cycle operating in the jets has now received observational support. Predictions of strengths and widths of additional lines which, if seen, would provide valuable new information about conditions giving rise to the jets are presented.
TAS measurements for reactor physics and nuclear structure
2011
In this contribution we will present recent total absorption measurements of the beta decay of neutron‐rich nuclei performed at the IGISOL facility of the Univ. of Jyvaskyla. In the measurements the JYFL Penning Trap was used as a high resolution isobaric separator. The total absorption technique will be described and the impact of recent results in the fields of reactor physics (decay heat calculations) and nuclear structure will be discussed.
Near threshold photoproduction of eta mesons off the proton.
1995
We have measured precise total and differential cross sections for the reaction $\ensuremath{\gamma}p\ensuremath{\rightarrow}p\ensuremath{\eta}$ from threshold to 790 MeV at the MAMI accelerator in Mainz with the neutral meson spectrometer TAPS. Resonance parameters of the ${S}_{11}$(1535) resonance and the electromagnetic coupling $\ensuremath{\gamma}p\ensuremath{\rightarrow}{S}_{11}$ have been extracted from the data. Contributions from the ${D}_{13}$(1520) resonance to $\ensuremath{\eta}$ photoproduction in the threshold region have been identified for the first time via interference terms in the angular distributions.
Results from the Real Photon Programme at MAMI
1995
The accelerator MAMI (Mainzer Mikrotron) with its excellent beam properties and its duty factor of 100% allows to apply coincidence techniques in intermediate energy nuclear physics, which has led to a variety of results with high precision. The real photon collaboration (A2) uses energy tagged bremsstrahlung photons with energies up to 800 MeV. We have results on total photon absorption (proton, deuteron, 3He and U), on Compton scattering (proton, 4He and 12C) and on meson production, especially on π°- and η-photoproduction. Double pion production on the proton and the deuteron was measured. The two and three body breakup of 3He was investigated as well as the reactions (γ,NN) and (γ, π ± …
Baryon transition form factors at the pole
2016
Electromagnetic resonance properties are uniquely defined at the pole and do not depend on the separation of the resonance from background or the decay channel. Photon-nucleon branching ratios are nowadays often quoted at the pole, and we generalize the considerations to the case of virtual photons. We derive and compare relations for nucleon to baryon transition form factors both for the Breit-Wigner and the pole positions. Using the MAID2007 and SAID SM08 partial wave analyses of pion electroproduction data, we compare the $G_M$, $G_E$, and $G_C$ form factors for the $\Delta(1232)$ resonance excitation at the Breit-Wigner resonance and pole positions up to $Q^2=5$ GeV$^2$. We also explore…