1,984 research outputs found
On the graphical extraction of multipole mixing ratios of nuclear transitions
We propose a novel graphical method for determining the mixing ratios
{\delta} and their associated uncertainties for mixed nuclear transitions. It
incorporates the uncertainties both on both the measured and the theoretical
conversion coefficients. The accuracy of the method has been studied by
deriving the corresponding probability density function. The domains of
applicability of the method are carefully defined
Internal conversion and summing effects in heavy-nuclei spectroscopy
Expérience GANIL, spectrometre LISEInternal conversion of low-energy nuclear transitions occurs with a high probability in heavy nuclei. After the emission of the conversion electron, a cascade of X-rays, Auger or Coster–Krönig electrons takes place. In -decay experiments in which the nuclei of interest are implanted into a silicon detector, these atomic processes contribute to the detected energy. To understand the distortions of -particle energy spectra, knowledge of the various atomic yields is required. Using state-of-the-art calculations, new atomic yields are computed in Es and compared to those available in the literature. Detailed simulations of the Md decay are performed and compared to experimental data. Possible ways to discriminate between the available atomic yields are also discussed
How large is the spreading width of a superdeformed band?
Recent models of the decay out of superdeformed bands can broadly be divided
into two categories. One approach is based on the similarity between the
tunneling process involved in the decay and that involved in the fusion of
heavy ions, and builds on the formalism of nuclear reaction theory. The other
arises from an analogy between the superdeformed decay and transport between
coupled quantum dots. These models suggest conflicting values for the spreading
width of the decaying superdeformed states. In this paper, the decay of
superdeformed bands in the five even-even nuclei in which the SD excitation
energies have been determined experimentally is considered in the framework of
both approaches, and the significance of the difference in the resulting
spreading widths is considered. The results of the two models are also compared
to tunneling widths estimated from previous barrier height predictions and a
parabolic approximation to the barrier shape
AGATA: Performance of -ray tracking and associated algorithms
AGATA is a modern -ray spectrometer for in-beam nuclear structure
studies, based on -ray tracking. Since more than a decade, it has been
operated performing experimental physics campaigns in different international
laboratories (LNL, GSI, GANIL). This paper reviews the obtained results
concerning the performances of -ray tracking in AGATA and associated
algorithms. We discuss -ray tracking and algorithms developed for
AGATA. Then, we present performance results in terms of efficiency and
peak-to-total for AGATA. The importance of the high effective angular
resolution of -ray tracking arrays is emphasised, e.g. with respect to
Doppler correction. Finally, we briefly touch upon the subject of -ray
imaging and its connection to -ray tracking
High-contrast Ultrabroadband Frontend Source for High Intensity Few-Cycle Lasers
An ultrabroadband seed source for high-power, high-contrast OPCPA systems at
800 nm is presented. The source is based on post compression in a hollow-core
fiber followed by crossed polarized waves (XPW) filtering and is capable of
delivering 80J, 5fs, CEP-stable (0.3rad RMS) pulses with excellent
spectral and temporal qualit
Spatial-domain interferometer for measuring plasma mirror expansion
International audienceWe present a practical spatial-domain interferometer for characterizing the electronic density gradient of laser- induced plasma mirrors with sub-30-femtosecond temporal resolution. Time-resolved spatial imaging of an intensity- shaped pulse reflecting off an expanding plasma mirror in- duced by a time-delayed pre-pulse allows us to measure characteristic plasma gradients of 10–100 nm with an ex- pansion velocity of 10.8 nm/ps. Spatial-domain interferom- etry (SDI) can be generalized to the ultrafast imaging of nm to μm size laser-induced phenomena at surfaces
Brunel-Dominated Proton Acceleration with a Few-Cycle Laser Pulse
International audienceExperimental measurements of backward accelerated protons are presented. The beam is produced when an ultrashort (5 fs) laser pulse, delivered by a kHz laser system, with a high temporal contrast (10 8), interacts with a thick solid target. Under these conditions, proton cutoff energy dependence with laser parameters, such as pulse energy, polarization (from p to s), and pulse duration (from 5 to 500 fs), is studied. Theoretical model and two-dimensional particle-in-cell simulations, in good agreement with a large set of experimental results, indicate that proton acceleration is directly driven by Brunel electrons, in contrast to conventional target normal sheath acceleration that relies on electron thermal pressure
Carrier-envelope phase stability of hollow-fibers used for high-energy, few-cycle pulse generation
We investigated the carrier-envelope phase (CEP) stability of a hollow-fiber
setup used for high-energy, few-cycle pulse generation. Saturation of the
output pulse energy is observed at 0.6 mJ for a 260 um inner-diameter, 1 m long
fiber, statically filled with neon, with the pressure adjusted to achieve an
output spectrum capable of supporting sub-4fs pulses. The maximum output pulse
energy can be increased to 0.8mJ by using either differential pumping, or
circularly polarized input pulses. We observe the onset of an
ionization-induced CEP instability, which does not increase beyond an input
pulse energy of 1.25 mJ due to losses in the fiber caused by ionization. There
is no significant difference in the CEP stability with differential pumping
compared to static-fill, demonstrating that gas flow in differentially pumped
fibers does not degrade the CEP stabilization.Comment: 4 pages, 4 figure
Co-existing structures in 105Ru
New positive-parity states, having a band-like structure, were observed in
105Ru. The nucleus was produced in induced fission reaction and the prompt
gamma-rays, emitted from the fragments, were detected by the EUROBALL III
multi-detector array. The partial scheme of excited 105Ru levels is analyzed
within the Triaxial-Rotor-plus-Particle approach
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